Boldly Going: A History of an American Space Station

[e of pi]

Boldly Going Part 17 Image Annex

Images by @nixonshead (AEB Digital on Twitter) showing off the interior of the LOX Tank after conversion to habitation space. Images in this annex are reduced in size, so click on them for links to the full size renders!

 

[TimothyC]

Boldly Going Part 18

The original concept for the Shuttle-C was to formalize the minimal-modification philosophy which had produced the Enterprise launch capability on STS-37R. In the end, changes and scope creep during the program meant modifications of some kind or another for almost every component of the stack. The Space Shuttle Orbiter was replaced by the new Rockwell OPAM, the reusable Orbital Propulsion/Avionics Module which held the RS-25 main engines during ascent through orbit and payload separation, allowing their return under parachutes to sites like Edwards or White Sands. The refurbishable Solid Rocket Boosters were replaced by new semi-reusable Liquid Rocket Boosters, originally contracted to General Dynamics, then handed off in turn to Martin Marietta and Lockheed-Martin in sequence as the aerospace mergers of the 1990s progressed. These new liquid boosters were intended to raise payload and increase safety not only for the lunar-bound Shuttle-C, but also eventually on conventional Space Shuttle missions. The same was true for the new “Super Lightweight Tank” developed based on the existing Light Weight Tank. Using aluminum-lithium alloy materials to replace aluminum in portions of the tank structures produced a reduction of close to ten percent in the structural mass of the tanks. This brought a benefit of nearly three metric tons in the payload not only of Shuttle-C but also the conventional Shuttles, which would begin using the new super-lightweight tanks as soon as they were available.

To build on existing production of high-performance hydrogen engines in the United States, General Dynamics’ proposal called for using a new variant of the same familiar RS-25, leaving the Shuttle-C an all-hydrolox vehicle for primary ascent. This variant would be the new SSME-35, a variant of the RS-25 with a smaller nozzle expansion of just 35:1 replacing the existing 69:1 nozzle used on the orbital RS-25 engines of the Space Shuttle and Rockwell OPAM. The powerhead and combustion chamber would be largely identical to that already being developed for the Block II RS-25 by Rocketdyne, enhancing cost-effectiveness through common production and manufacturing throughout the Space Shuttle and Shuttle-C program. Even with these cost reductions, it was unthinkable to watch hundreds of millions of dollars of precisely constructed engines fall into the ocean on every launch--indeed, such a waste would hardly have been worth contemplating for double or triple the Shuttle-C’s launch capability. To avoid this, the liquid booster’s engines would be mounted in their own pod, which could detach from the bottom of the relatively simple tanks as had the booster engines of General Dynamics’ stage-and-half Atlas rockets. The pod would parachute into the ocean, protected from water and impact by airbags and flotation devices. The existing recovery flotilla could then retrieve the pods and bring them back to Kennedy Space Center. Existing maintenance facilities could service the pods on-site, as the SSME-35 and SSME-69 engines were almost fully interchangeable other than the bell. Compared to the existing Solid Rocket Boosters, this avoided the expense of shipping all booster hardware across much of the country between uses and would increase utilization of teams and facilities already on-site in Florida. Similar benefits would come from increased utilization of existing staff at Michoud, where NASA and General Dynamics proposed co-location LRB and External Tank production. Though specific production tooling varied between the tanks, an existing knowledge base and technical staff could be drawn upon for the new booster’s tanks.

The new Liquid Rocket Booster system would not only improve the payload of the Shuttle-C for the Minerva lunar missions. Their use aboard the conventional Space Shuttle would increase safety, cut costs, and boost the ability of the Shuttle to carry logistics payloads such as experiments, food, water, and other consumables to the space station compared to the existing Solid Rocket Boosters. They would also enhance the existing orbiters’ ability to launch the heavy new modules which would make up Space Station Enterprise’s enhanced laboratory capabilities. Unfortunately, the decision to incorporate these improvements into Shuttle-C added the possibility for greater delays if unexpected problems cropped up with the new hardware. While Shuttle-C had initially been planned to debut in 1996, this date ended up--almost inevitably--delayed. For the OPAM, these delays had largely related to the new electro-mechanical actuators (EMAs) and the adaption of Shuttle-heritage tiles and thermal blankets to the new OPAM outer mold-line. Sufficient battery power to control through an off-nominal ascent and once-around abort ended up exceeding the available system mass. Instead, a new ethanol-LOX APU, powering a turbo-generator, was substituted to provide primary SSME gimbal power and recharge a smaller set of flap actuator batteries for orbital operations and landing. While the change produced a more operable system which still eliminated two hypergolic fluids from the vehicle, the delivery of the first flight-ready OPAM module for NASA acceptance testing at Stennis was delayed into 1996. This, in turn, pushed its availability for first flight into 1997. As the brains and brawn of the new Shuttle-C, the OPAM contained most of the same systems as a Space Shuttle boattail in a new, though still reusable, form factor, and they were assigned designation codes just like their Orbiter half-sisters. While the Shuttles were sleek darts bearing the name of ships of exploration, the OPAMs were workhorses to be judged by their lift and the first pair delivered were given internal nicknames referencing heroically outsized figures from American folklore. The first delivered, OV-201, was dubbed the “John Henry,” while OV-202 was dubbed “Paul Bunyan.”

While on the surface apparently less complex, the liquid rocket boosters were actually the larger source of delays. Designing an engine pod capable of detaching from its tanks inflight drew heavily on General Dynamics’ Atlas stage-and-a-half experience, and both NASA and General Dynamics had originally expected the development process to be relatively straightforward compared to Rockwell’s Orbital Propulsion and Avionics Module. Unfortunately, the program faced one unexpected challenge after another, from the thermal protection of the engine pod on entry to challenges with the changes intended to reduce maintenance on the low-expansion RS-25E engines. Repeated corporate restructurings had not helped matters, and issues with water infiltration in early tests of engine pods dropped under parachute for procedure development were still causing delays as late as 1997. By the middle of 1996, it became clear to NASA that while Rockwell would be delivering OV-201 in time to support a Shuttle-C debut in the middle of 1997, Lockheed-Martin (the current inheritor of General Dynamics’ Space Division and the LRB contract) would not have the new liquid boosters ready for at least another six months beyond, pushing Shuttle-C’s debut into 1998. This would leave only 18 months from the Shuttle-C debut flight to the unofficial goal of “sortie before the Apollo 11 30th anniversary”. The delays and reduced margin were initially discussed largely within Marshall, but as the updates diffused through the Space Shuttle mission planning teams at Johnson and the Minerva program office, they began to draw increasing attention from NASA headquarters. Eighteen months from launcher debut to the first landing was not unprecedented--it was similar to Apollo’s successes. However, NASA of 1997 was no longer the agency it had been in 1967, and headquarters and Minerva management were less willing to be cavalier with time or spending. In finding a path to best protect Minerva’s budget and objectives, NASA leadership faced a hard decision.

One option was to fly the early demonstration missions of the Shuttle-C using the existing Space Shuttle Solid Rocket Boosters. Exploiting the “drop-in” design of the liquid boosters for the conventional Space Shuttle stack, reverting to the Solid Rocket Boosters for the first demonstration flight would allow the maiden launch to occur at least in the summer of 1997. This would add another 6 months of schedule protection to the lunar landing goal and keep the Shuttle-C on pace with other program hardware. However, this would remove the intended first flight of the liquid boosters on the relatively low-risk demonstration mission. From then until the first sortie mission, all Shuttle-C missions were planned to be flown with crew aboard, testing program-critical payloads and with critical mission objectives. Using Thiokol’s SRBs on the debut of Shuttle-C would lock in their use for these subsequent missions, and delay the debut of the LRBs until after the first landing. This would heavily impact payload margin by cutting the Shuttle-C’s capabilities, creating issues for the already-marginal single-landing payload of the new LSAM in the sortie configuration., Thus there would be added risks to the safety, success, and value of the initial lunar return flights. The other option was to wait out Lockheed Martin’s delays and allow Shuttle-C to debut with the LRBs on the first flight as intended. This would add no crew risks and incur no further program-level schedule “debt” beyond the initial delays. The risk was that if Lockheed Martin continued to experience delays, the launch of the first lunar return mission might slide out of 1999 and into the new millennium.

With the 1999 lunar return goal being strictly unofficial, NASA ultimately decided that crew safety outweighed any concerns of “lunar return by the Apollo 30th.” Even in his Space Exploration Initiative speech in 1989, President Bush had specifically stated his goal to avoid setting a hard and fast decadal target, and further had identified Space Station Enterprise full utilization as the primary task for the 90s, with the lunar program only to be “beginning in the 1990s”. While President Clinton had supported the international character of the lunar program, he had echoed similar language. Ultimately, Minerva’s program leadership pushed NASA’s human spaceflight leadership team to accept the delays, a process boosted when NASA’s congressional outreach and the Public Affairs Office found that “the moon for the new millennium” was just as--if not even more--effective as a message as “the moon before the 30th anniversary of Apollo”. The delays would just have to be tolerated - Lockheed Martin would get the time they needed. By the spring of 1997, NASA’s patience was rewarded, as Lockheed’s schedules stopped slipping and the intended delivery of the first booster sets stabilized in January of 1998. Ultimately, through herculean effort by Lockheed Martin and NASA, the first LRB flight hardware was accepted for delivery by NASA in December of 1997, two weeks before the revised promise date. Still, pressure on the broader Minerva program remained tight, and had impacts throughout NASA’s human and uncrewed spaceflight programs.

 

[e of pi]

Boldly Going Part 19

The Shuttle-C debut wasn’t the only place where Shuttle-heritage liquid and solid rocket boosters were being weighed against one another. Even before the tragic loss of Discovery, forces within the Department of Defense had already questioned the wisdom of concentrating their entire heavy launch manifest on the Space Shuttle. With dubious flight rate assumptions and high operational costs, an alternative that would complement the shuttle was sought. Once the Space Shuttle returned to flight, these issues were only amplified, especially given the requirement to support every Shuttle mission out of Vandenberg with a second launch-on-need standby orbiter out of Florida. Thus, the DoD decided that it was in the interest of national security for them to maintain their own parallel stable of launch vehicles. The immediate result was the conversion of the Titan IV, originally intended to complement the Space Shuttle, into an entirely parallel program. The Titan IV, a derivative of the long-standing Titan vehicle, pushed its heritage to the limits in order to launch Space Shuttle-class payloads. However, it became clear that the Titan IV had very little remaining growth potential, and costs for the Titan-derived vehicles were spiralling upwards at dizzying rates. If the DoD was to have a parallel stable of launch vehicles as a backup or alternative to using NASA’s Space Shuttles, it would need a new vehicle, designed from the ground up to be cost-effective for the Department’s current needs. Beginning in the late 1980s, the DoD began incubating the concept of a new expendable launch vehicle program to replace the Titan IV and end dependence on Shuttle. In one of few solid policy actions taken in spaceflight between Bush’s 1989 Space Exploration Initiative speech and the 1991 formal authorization of Space Station Enterprise expansion and the new lunar program, Congress authorized the DoD to conduct a competition to select a new “Evolved Expendable Launch Vehicle.”

In the original 1991 specification, the Department of Defense called for contractors to submit designs for a vehicle or family of vehicles capable of launching payloads ranging between 20,000 and 65,000 pounds to a low Earth orbit, with geostationary orbit performance of up to 25,000 pounds. Most companies submitted proposals, but when the downselections were made in late 1992, two proposals stood head and shoulders ahead of the pack both in terms of capability but also in terms of operational cost: Thiokol’s Heimdall launcher (the new marketing-approved name for a variant on their 1980s SRB-X family) and General Dynamics’ Atlas III (the marketing-approved name for that company’s proposal to use their Shuttle-C LRB engine pod mounted to a lightly modified tank set for a common-core booster). Drawing on the legacy of the existing Space Shuttle and the development already funded by NASA for the new Shuttle-C lunar launch vehicle, Heimdall and Atlas III offered relatively low development costs and strong payload growth potential. Moreover, though the DoD had not initially required consideration of recoverability and reuse in their bid specifications--a fact the “Expendable” in the competition name hinted at--the recoverability of significant portions of both vehicles helped boost their cost-competitiveness compared to the other alternatives.



Thiokol’s Heimdall was viewed as a low-risk and immediately available option. Better yet, the opportunity to support the heavy solid rocket booster production industry found powerful backers within the DoD and on Capitol Hill. Still, much as with the Space Shuttle and Shuttle-C, General Dynamics’ liquid booster offered increased performance and decreased maintenance time and cost. Though originally the EELV program had been expected to downselect to just one vehicle, it ultimately selected both of the two Shuttle-related vehicles in late 1992. The fact that both programs had powerful interests on the Hill helped protect the DoD from charges of unneeded duplication of contract costs, and having two vehicles with largely separate supply chains would help protect the DoD’s “independent” stable of launch vehicles from any stand-downs of NASA’s Space Shuttles. In such an event, the DoD could simply fall back to its other launch vehicle. In keeping with the reusability of both selected options, the program was renamed in 1993 into the National Security Space Launch (NSSL) program. By the end of the year, the Atlas III NSSL entry had been inherited by Martin Marietta when they completed a purchase of General Dynamics’ entire space division, including both the Shuttle-C LRB and its Atlas III derivative.



As had happened with Commercial Titan III, NASA too found benefits in the availability of a Shuttle-parallel cost-effective launch vehicle, both for flagship exploration missions and for the carrying out of tasks which would have otherwise required diverting scarce Space Shuttle launch windows to lower-priority but still schedule-critical missions. This was illustrated best with the debut of Thiokol’s Heimdall rocket in the spring of 1997, when NASA provided the DoD with payloads for the first several “risk-reduction” launches. These payloads were the satellites of the Lunar Data Relay System, revised versions of NASA’s existing TDRS satellite constellation able to handle the relatively minor differences between operations in geostationary orbit and operations in long-life halo orbits around the Earth-Moon Lagrange points EML-1 and EML-2. A set of three satellites at each of these points would extend NASA’s continuous communications and tracking relay system from low Earth orbit to anywhere in cis-lunar space or on the surface of the moon. While NASA weighed the benefits of waiting for Lockheed Martin’s liquid booster for Shuttle-C, the Thiokol Heimdall was proving its value paving the way for future astronauts with the launch of six LDRS satellites spread between three early Heimdall launches in 1997 and 1998.

Artwork by @TimothyC (Arnie Holmes on Twitter) in Shipbucket Style

 

[TimothyC]

Boldly Going Part 20

After all the delays, the date for the maiden launch of Shuttle-C finally arrived as OV-201 made its first trip to the pad in early 1998 for the debut of the new heavy lifter. Though officially the Shuttle-C mission numbering was subsumed within the broader “STS” mission list, a block around STS-100 had been carved out for the debut Minerva missions when their planning was frozen in 1997. Thus Minerva planning was enabled without reference to broader Space Shuttle and Space Station Enterprise operations. Shuttle-C’s debut would be designated STS-99-C. The Orbital Propulsion and Avionics Module (OPAM) “John Henry” and the rest of the STS-99-C stack left High Bay 2 on the crawlerway to LC-39B, following the path of its antecedents: the Saturn V, and the Space Shuttle Enterprise. The payload it would carry for the maiden launch of the Shuttle-C had been heavily debated. Attempting to square the circle of conflicting demands for pad and VAB access at Kennedy Space Center, it had been considered that the maiden Shuttle-C might follow even more directly in the footsteps of Enterprise and STS-37R by carrying several elements of Space Station Enterprise’s truss to orbit. However, the risk of the new vehicle’s debut carrying such difficult-to-replace payloads loomed large in the minds of those who only a few years ago had lived through the tension of STS-37R and STS-38R’s early days. Even worse, a new vehicle would have to be provided to circumvent the problems of getting the truss elements to rendezvous with the station. Another plan to attempt to sell space aboard the maiden launch to a risk-tolerant commercial customer fell through when none could be found who were willing to meet NASA’s requirements.

Ultimately, the primary goal selected for STS-99-C was a test of the Kepler-L’s revised heat shield, executed by using the first flight version of the new Earth Departure Stage to send a boilerplate Kepler capsule (with the newly designed launch escape system for aerodynamic fidelity during ascent) into an elliptical orbit simulating the velocity of Earth return. The recovery of the two booster engine pods by the recovery flotilla and the return of the “John Henry'' under parachute to White Sands Space Harbor two days later proved that the Shuttle-C was as capable as its STS-37R predecessor--and far more repeatable. By the time OV-201 returned to the ground, the Earth Departure Stage had demonstrated its own potential, firing after a four-orbit coast to propel the Kepler-L boilerplate and over ten metric tons of water ballast into a high energy orbit, demonstrating the stage’s ability to propel payloads into cislunar space. The boilerplate, for its part, demonstrated the required ability of Kepler-L’s upgraded heat shield to handle returning to Earth from the higher energies of a cis-lunar trajectory. In the history of NASA’s heavy lift program, STS-99-C would compete with STS-37R for the title of the maiden flight of Shuttle-C.



The success of the maiden Shuttle-C launch paved the way for the Minerva program’s second planned demonstration mission and the first Minerva crew to fly in space. The Minerva program’s complex mission profiles resulted in a variety of mission numbers assigned to any given flight, and Minerva 1 was no exception. The launch support tasks were often referred to within KSC by the launch’s mission number, STS-100-C, while ESA’s Kepler support led to the capsule most commonly being tracked as the “Kepler-L1” mission. Managing three names for the same mission was just one preview of the complexity awaiting the Minerva 1 crew after their launch in September of 1998, which marked the first time a crew would fly aboard the Space Transportation System with no Shuttle. For the STS-100-C launch, four astronauts including ESA pilot Thomas Reiter flew in the upgraded lunar-capable Kepler capsule Jules Verne for Kepler-L1 atop the second launch of the John Henry, along with the first of the program’s Conestoga lunar modules. Though both the Kepler capsule’s new lunar-equipped Service Module and the new Conestoga LSAM had been extensively tested on the ground prior to acceptance, this launch was the first test of each vehicle in space. It would be a marathon workout for both. For safety, the initial launch brought the vehicles into an orbit coplanar with Space Station Enterprise, helping to ensure the station was constantly available as a safe haven should issues aboard the untested vehicles require response beyond that which NASA could provide from the ground.

Once in orbit, the crew of STS-100-C aboard the Jules Verne flipped their spacecraft over, and extracted the LSAM from the payload shroud which had protected it on ascent. With the LSAM extracted, the engine module was no longer needed, and the OPAM John Henry was commanded to detach and go about the process of returning to Earth. The Verne’s crew then boarded the habitat module and activated its systems. Over subsequent days, the crew conducted orbital adjustments to test both the enhanced Trans-Earth Injection capability of the Verne’s Orbital Maneuvering System and the main engines of the descent stage of the LSAM. When both systems proved functional, Verne’s crew settled in to test one another major capability of the lander: its equipment for use on extended lunar missions, yet another contribution of Space Station Enterprise to the lunar project. The launch of STS-37R and the dramatic demonstration of the capability of the Space Transportation System when its Orbiter could be defined as payload capability and not ballast was a key factor in the selection of the middle-of-the-road side-mounted Shuttle-C instead of a larger and more expensive in-line modification of the Stack for launching lunar payloads. The European Kepler crew vehicle drew directly on work done for Space Station Enterprise’s lifeboat requirements. The LSAM drew on yet another of the things Enterprise had demonstrated: the tremendous value in reusing propellant tank volume as functional living space on extended duration missions.

Using a concept dubbed “Habitank,” the Conestoga LSAM mounted the hydrogen tanks for its descent stage as two massive, nearly-rectangular volumes, one on each side of the vehicle with each then subdivided internally by slosh baffles. For the initial demonstration landings, designated “Class-A” missions but often referred to simply as “sortie flights,” the LSAM would rely on a central two-level habitat/airlock module to support a crew for a few days on the surface. For longer duration outpost missions, the two hydrogen tanks could be accessed using permanent passageways and the volume inside the tanks vented, filled with breathable air, and outfitted. A second set of ports on the end of each tank would allow deployable corridors to connect the Habitanks of each crew and cargo lander to node modules carried as the main payload of cargo landers, meaning even a crew rotation landing would contribute nearly 50 cubic meters of new volume to a base. A single crew lander and cargo lander would constitute a “Class-B” outpost mission, capable of supporting a full crew of four for more than a month. Adding two more landers would turn a Class-B outpost into a Class-C lunar base, capable of supporting a permanent crew of four with sufficient rotations and resupply. The use of the Habitanks to grow capabilities smoothly from sortie to settlement helped inspire the selection of the LSAM’s program name, Conestoga. Like the old Conestoga wagons which had helped settle the American west, the new Habitank LSAM would see the crew space expand as their supplies contracted and they forged forward across inhospitable terrain.









With the main engine of the descent stage tested, the crew of the Verne vented the LSAM’s tanks and spent four days verifying the procedures to safing the tanks, pressurizing the same with a breathable atmosphere, and opening them for outfitting. The conversion of ET-007’s LOX tank into the Enterprise Habitat Module was not only valuable inspiration, but also served as an opportunity to learn best practices for what to do (and not do) in converting a tank into a habitat. While the procedures had been extensively tested on the ground in mockups and even in flight-fidelity hardware inside Glenn Research Center’s cavernous Plum Brook vacuum chamber, testing the Habitank conversion process in space was a key goal of the debut mission of the Jules Verne. The benefits of recent experience were readily apparent. Even with the handicap of the absence of gravity, whether that of Earth as experienced in the mockups or the lower lunar gravity which would be experienced on nominal missions, the outfitting by Verne’s crew (including a few Enterprise assembly veterans) went smoothly.

Over the course of four days, the crew went through the elaborate process of testing the conversion of the LSAM’s port hydrogen tank. First, the tank was vented to space and allowed to thermally condition for 13 hours, to ensure any residual hydrogen had a chance to escape. Next, the crew connected the tank to the vehicle’s nitrogen supply, and flooded it with the main portions of a breathable atmosphere. Another few hours allowed the tank to reach thermal equilibrium again, and then oxygen was added to bring the breathing gas mixture inside the tank to sea level equivalent composition. When the tank reached habitable conditions, the STS-100-C crew opened the tank access vestibule, removed insulation panels, and then accessed the tank itself--all told, consuming almost a day from the first venting of the tank. From there, the crew disassembled the internal slosh baffle walls and outfitted the volume with some of the rough equipment of a basic module, using materials which had been temporarily stowed in the vehicle’s sortie habitat and airlock. The tank habitat’s major wiring and ventilation runs were installed, along with a few of the required lighting modules, internal insulation and other equipment. The resulting module was as skeletal as a 1996 photograph of Space Station Enterprise’s habitat, but a full outfitting wasn’t required to prove the point.



With the rough outfitting complete, the conversion had progressed far enough to show the process was indeed viable in space in the new tank layouts, and that the time required was in line with the expectations from the ground testing and Enterprise experience. As expected, the labor required was too much to be of use on the two-person sorties possible from a single lander, but well within the operational window of the multi-launch medium-duration outpost flights where the additional volume available “for free” would be invaluable. With the critical tasks complete, the new habitat was immediately abandoned, as the descent stage was jettisoned to allow the crew to test the LSAM’s ascent stage. Though its time in use was short, the early flight of Habitank in orbit had demonstrated critical applications of Space Station Enterprise experience to the expansion of future lunar outposts. However, for there to be a lunar outpost to be expanded, the lunar program would have to first succeed in returning humans to the moon and bringing them safely back to Earth. STS-100-C completed the demonstration of this by jettisoning the LSAM’s lower descent stage and testing the engines of the ascent stage, completing trials of all three new spacecraft propulsion units debuting on the mission. The crew returned safely to Earth after a week in space, completing the second Minerva demonstration mission. Whether considered by the standards of STS-100-C, Kepler-L1, or Minerva 1, the mission could only be called a complete success. The stage was set for the return of humans to the moon.




[1] For more reading on the (real!) Habitank concept, you can check out either the project report here or its section in the fantastic After LM: NASA Lunar Lander Concepts Beyond Apollo by John F. Connolly. You can also see some images of the real mockups made to evaluate the concept IOTL here.

Thanks in general go out to the entire art team for this post: @nixonshead (AEB Digtial on Twitter), @norangepeel (Cass Gibson on Twitter), and DylanSemrau

 

[e of pi]

Boldly Going Part 21

The STS-100-C launch of the Minerva 1 mission paved the way for the first human landing on the moon in three decades. Still, there were critical tasks which had to be conducted to complete the certification of the Conestoga lander and Kepler capsule for the lunar mission. These were more than just paperwork challenges--the hardware for Minerva 2 simply was not ready. In the Apollo era, budgets had been high enough to always have the next mission’s hardware prepared almost immediately. The result was the demonstrated ability to launch five Saturn Vs either to the moon or with lunar-capable hardware to orbit in a single 12-month period. By contrast, NASA of the 1990s had to work within strict budget constraints, with funds siphoned off for the ongoing support of Space Station Enterprise and NASA’s various unmanned probes, including the lunar precursor missions and flights to Mars as well as beyond. The result was a certain inevitable friction as the two launches required for Minerva 2 were prepared in tandem.

The first launch of the mission, STS-101-C, would carry the relatively low-risk payload of the filled Earth Departure Stage. Much as with STS-37R, the EDS could loiter in orbit for some time on its own and its launch date was relatively open. However, once the EDS was launched, the second launch of the pair, STS-102-C, would carry the crew and their lander to meet it. This required a safe launch for the crew and delivery of the mission’s capsule and lander to orbit within the tight launch windows each day over the week the EDS could loiter without losing its propellant margins for trans-Lunar injection to boiloff. With these tighter constraints and higher-value payload, the more proven OV-201 “John Henry'' was assigned to the STS-102-C stack. The veteran OPAM proceeded through a smooth turnaround and stacking flow. This left the second space-rated Shuttle-C engine module to come off of the Palmdale line, OV-202 “Paul Bunyan,” assigned the lower-criticality STS-101-C mission. While turnaround and stacking for “John Henry” was fairly smooth, the new hardware for the STS-101-C stack made up with more than its share of delays. The initial delivery of “Paul Bunyan” was held up for weeks at Stennis during testing due to persistent but intermittent computer failures which only occured during simulations of full-mission firings, and not during single-engine or full-cluster short duration static testing. The problems were ultimately traced to interference caused by faulty grounding in the new electromechanical actuator system, but the result was that the second propulsion unit needed for the two launches of STS-101-C and STS-102-C was delayed. Similar delays plagued the Kepler capsule program--though Jules Verne had performed well enough on orbit, some changes had been recommended, and overhauling the Francesco Grimaldi to incorporate these improvements delayed its delivery to Kennedy Space Center from Europe for the Kepler-L2 flight.

The production of the new sea-level-optimized SSME-35 engines for the Lockheed-Martin LRBs was another source of delay, as Rocketdyne struggled to increase their build rate enough to address NASA’s order for more than 40 of the new sea level engines on top of DoD requirements for the activation of Lockheed Martin’s Atlas III NSSL Vehicle. Though NASA had initially ordered enough of the new Block II powerheads fitted with SSME-35 nozzles to supply four two-booster flight sets, issues with scaling production to meet the surging demand meant that by the end of 1998 Rocketdyne had managed to deliver only 18 of the new engines to address NASA’s order--still two engines shy of the twenty needed to equip two full flight sets. Desperate for engines, NASA was forced to turn to an unorthodox source: the DoD’s NSSL program. The Atlas III had just completed the launches required for its debut and certification process, and had a nine month gap in its flight manifest. Though the USAF and NASA relationship over their shared pod hardware was always uneasy, the USAF was eventually persuaded to allow Rocketdyne to rob Peter to pay Paul, largely on the strength of being able to borrow from NASA’s pool of engines and booster pods in the future, when their ongoing acquisition would leave them a larger pool of spares. This promise of a trade for a “player to be named later,” in sports terms, allowed Rocketdyne to temporarily borrow two flown SSME-35 engines from the Atlas III certification flight set to give NASA enough LRB engines to have STS-101-C and STS-102-C ready simultaneously for the first lunar sortie in three decades.

The result was one minor delay after another, pushing the launch of Minerva 2 out into the summer. Still, the delays to the lunar program in 1998 and 1999 were to Space Station Enterprise’s gain. While the lunar program wrestled with hardware availability, their delays freed slots on Kennedy Space Center launch schedules and Johnson Space Center training calendars. The gaps allowed the station program to accelerate the launch of the new modules for the massive orbital complex. In 1997, the early station crews had completed the assembly of the new Enterprise Habitat Module inside the former ET-007 LOX tank. Expedition 6, which had taken over the station from Expedition 5 in the fall of 1997, was ready for the hard EVA work of installing the first of the station’s new modules. The only challenge was for the Shuttle crews to deliver modules and aid in their attachment. In warehouses and payload preparation facilities from Houston to Florida, the sections of the station’s new Integrated Truss Structure had begun to accumulate. Beginning in the spring of 1998, these segments began to rise to orbit, requiring an entirely different type of labor-intensive assembly. The buildout of the deck structures and internal fittings of the Enterprise Habitat Module had been a day-to-day litany of minor tasks, individually each short and simple, but performed over and over. In the course of the outfitting, astronauts had been tasked with building up more than a dozen support columns and then attaching hundreds of deck and wall frame units, and installing hundreds of meters of air ducts, power lines, and other utilities. The work was tedious, but low-risk and conducted entirely in pressurized environments--the kind of work which called more for hourly technicians than PhD-equipped astronauts. The Integrated Truss Structure assembly, beginning with the launch of the P0 Module on STS-105 in May of 1998, represented something entirely different.

Thanks to the extensive ground-integration of the truss elements, only a few dozen hours of work were required to attach the first sections to the pre-prepared SRB mounting points, install power and data cables, and connect radiator coolant loop lines for future use. The P0 Module on the port side of Enterprise, and its mirror-twin the S0 module on the starboard side were an early trial of this approach. Though the two modules played home to the start of the Mobile Basing System’s “railroad in space” along the truss, and provided mounting points to future scientific experiments, they were primarily structural spacers with few of the complex deployment events common on the radiator and solar array elements of the truss. However, those few hours of work required elaborate choreography and training on the ground, and work in the arduous and exhausting EVA environment instead of the shirt-sleeve work environment of the ET-007 LOX tank. Unlike the free-wheeling shirtsleeve environment of the tank outfitting process, where simple tasks could be carried out as needed by whichever crewmembers were available or simply set aside for later, the EVAs were limited to two crew members at a time and planned to the minute, including contingencies. There was no manhandling of structural elements, instead the bulk positioning could be done by the station or Shuttle’s Canadarm robotic maneuvering systems. Even so, issues cropped up with connecting the inboard structural connections to the mounts originally intended to carry the Solid Rocket Boosters. While the joints were designed for large axial loads, they could not be fully used due to the remains of the bolt capture systems originally designed for separating the boosters in flight--the SRB attachment points never having been envisioned during Space Station Enterprise’s original design in 1983 as a spot for future expansion. Thus, once the preliminary structural connections were made with bolts, stabilizing arms were deployed to press against the sides of the external tank to help spread the load. All the while, astronauts worked against as much as with their suits. Each was, after all, a tiny spacecraft in its own right with gloves that tortured hands and joints which turned every movement into an exertion.

The benefit of the modular assemblies was that every Shuttle mission and indeed each EVA made for massive and dramatic progress aboard the station. As the Space Shuttle Endeavour departed the station to complete her STS-105 mission, the crew had left a permanently changed Space Station Enterprise behind them. The new P0 module stuck out awkwardly from the port side of the station, the first asymmetric external sign of the changes coming soon. While the station’s appearance had been largely identical for every arrival between STS-38R and STS-105, now it would begin to alter radically every flight. With the lunar program delayed, opportunities were opened to advance the schedule of Enterprise components already waiting for launch, and the result was that an assembly mission visited Enterprise almost every month and a half during 1998.

The STS-105 mission’s launch of the P0 truss was mirrored with the installation of the S0 truss on the other side of the station by STS-106 just seven weeks later. Logistics upmass intruded briefly in late August, then Endeavour carried up the first of the new radiator modules with the launch of the P1 Truss Element on STS-108 in early September. The first of the station’s massive new solar arrays, the P2/3 Truss Element, was carried to orbit and attached to Enterprise by Atlantis in October. After Atlantis visit on STS-109, the station presented a strangely asymmetric profile with its new 50 kW of additional generating capacity until the arrival of STS-110 in December and STS-111 in January of 1999 completed the inner solar arrays. Previously, the External Tank and Orbiter had dominated the station’s profile, even with the Enterprise Power Module spread near the tail. Now, the station had developed an entirely new scale, spreading triple the original amount of panels on a new truss longer than the External Tank.



The success of these preparations for the station’s further growth was demonstrated with the launch of the new European Laboratory Module Columbus aboard Challenger in April, 1999. The new module was the first new laboratory space worth the name since the station’s original launch in 1989, and marked the start of Enterprise’s transition to a fully operational center for orbital research instead of a decade-long job site. In spite of this milestone, STS-113 took place in a relative vacuum of press coverage, as even internal NASA coverage focused on the upcoming lunar return. After Challenger vacated High Bay 1 on the way to the pad to launch Columbus to the station, her space in the VAB would be taken by STS-102-C, the third launch of OV-201. These vehicles, once prepared, would launch the lander and capsule intended to ferry the first lunar crew in three decades.



Artwork by: @nixonshead (AEB Digital on Twitter)

 

[TimothyC]

Boldly Going Part 22

In 1969, hundreds of millions had tuned in to watch as the Apollo 11 crew had journeyed to, and landed on the Moon. In early 1999, thanks to the explosive growth of television and other media, NASA’s press office estimated the audience for the return to the moon could top a billion people. The public affairs office had worked to support several Apollo history projects in the leadup to the lunar return, including the discovery of several reels of 65mm footage of the rollout and launch of Apollo 11. They were determined to document the return of humans to the lunar surface at least as well, and as the two massive Shuttle-C boosters rolled to the pad, they were accompanied not only by security guards, technicians, and engineers but also by IMAX film crews. The maiden launch of the new OV-202 “Paul Bunyan” would fly from LC-39A, carrying the Earth Departure Stage to orbit. The relatively proven OV-201 “John Henry” would carry the Kepler-L2 crew aboard the new Francesco Grimaldi. As a Class-A sortie mission, only half the crew would land, spending just four days on the surface due to consumables limits. The surface crew was led by the overall mission commander Eileen Collins, her third flight assignment after previously flying and commanding the Space Shuttle. Along with her Lunar Module Pilot, Rick Husband, Collins would descend to the surface while ESA’s Kepler pilot Lt. Col. Maurizio Cheli and NASA’s Scott Horowitz would remain in orbit, conducting observations of the lunar surface and prepared to assist with any issues during the first landing of the new Conestoga LSAM on another world. A marker of the lunar program’s delays could be found in how far out of sequence the mission numbers they retained from the “century block” reserved for the lunar program had slipped from those being flown by conventional Shuttles. While “John Henry'' and “Paul Bunyan'' were being rolled to the pad for STS-101-C and STS-102-C, orbiter Endeavour was already being prepared for STS-114, which would carry the first elements of the Japanese laboratory complex. The delays of the dual-launch requirement were now also affecting Enterprise’s schedule. Until at least STS-101-C was flown, orbiter Atlantis was effectively pinned inside the Orbiter Processing Facility for lack of an available VAB cell to begin preparing for either an STS-115 mission or a Launch-on-Need STS-315. Without Atlantis ready for an orbital rescue of Endeavour, STS-114 could proceed no further than stacking and checkout. Thus, NASA’s entire attention was focused on the preparation of the two cargo stacks for near-simultaneous launches--and that included the crew aboard Space Station Enterprise.

This would be the first lunar landing watched live by humans off Earth, and the crew of Enterprise Expedition 11 were looking forward to being an audience to history. Even with the new European Columbus laboratory requirements added to the “Old Lab'' of the LLM in OV-101’s payload bay, science aboard the station only had full-time demands for one and a half astronauts. Maintenance and upgrade preparations for the station added requirements for another two and a half full-time astronauts, but the result was that the crew still had substantial free time available, at least between Space Shuttle visits. Though there was little they could do to support the launch beyond well-wishes, Enterprise Expedition 11 still found time to follow every technical briefing on the progress of STS-101-C and STS-102-C as Grimaldi’s crew prepared for their lunar flight.

When STS-101-C lifted off the pad in June 1999 with the Earth departure stage, the NASA TV broadcast of the launch was relayed up to the station, and played on both of the station’s internal video monitors (one on the wall of the galley in the new Habitat Module, and fitted with a projector and drop-down screen, and the other included as part of the Enterprise Operations Center in the former cockpit of the orbiter). While the majority of the crew clustered around the screen in the galley, three had a more direct seat in the EOC. A coincidence of timing allowed the crew aboard Enterprise to photograph the launch of STS-101-C from the windows of Enterprise as it passed over the Kennedy Space Center--the first time a launch of Shuttle-C had been captured from space. Japanese astronaut Soichi Noguchi captured several famous still images, while American rookie astronaut Don Pettit filmed the event with the station’s VHS camcorder. The film, scratchy as it was, held a place of pride in the station’s onboard video library for years, and was copied for return to Earth. In the background audio, the commentary from the NASA TV live coverage can be heard while a barely-visible tower of steam with a glowing pinprick at its head rises from the Florida coast line. OV-202 proved as solid in its debut as OV-201 had before it, leaving the Earth Departure Stage behind in orbit before returning to Earth at White Sands. Now, the clock was on to see Grimaldi’s crew join their ride to the moon in orbit.

The new Shuttle-C demonstrated the value of drawing on NASA’s entire STS legacy for heavy lift, as the launch of STS-102-C followed mere hours after STS-101-C. After launch on STS-102-C, the crew separated Grimaldi from the fairing shroud, extracted their LSAM, and boosted away from OV-201 and the expended External Tank to pursue a rendezvous with the Earth Departure Stage launched earlier that day. By the end of Flight Day 2, the stack was docked and verified, and the words were given: “Grimaldi, you are GO for the moon.” The EDS’ RL-60 engines lit to carry the stack on the beginning of their lunar journey. For three days, the crew of Enterprise went about their daily tasks aboard the station, preparing for the planned launch of STS-114 to carry up the first elements of the Japanese lab in just over a month. However, the progress of the Grimaldi flight was never far from the crew’s mind. At least one of the station’s radios tended to remain tuned to the LDRS link via TDRS relay at all times to follow along with the mission in the most direct possible fashion. When Grimaldi passed the point where lunar gravity began to dominate Earth gravity, NASA arranged a press event with a conversation between the crews of the lunar and station missions, which was widely broadcast on the ground. Enterprise Expedition 11’s commander, Michael Foale, closed the event by offering his best wishes to Collins and her crew aboard Grimaldi as they were “going where so few have gone before.”

Part of the reason the quote became so famous had to do with public attention to the mission. Though NASA’s public affairs had been promoting the entire lunar return throughout the demonstration missions and the leadup to STS-101-C, it was widely noted that it was as if in the days leading up to STS-102-C that the country and the world suddenly awoke to discover they were once again actually embarked on a journey to the moon. Visitors on NASA’s websites peaked in the hundreds of millions per day as the crew of Grimaldi flew on their lonely path to the moon, causing many of the agency’s public-facing servers to crash under the load until more were brought on-line. News programs suddenly began to pick up the video packages NASA’s public affairs office had so carefully prepared. CNN, in particular, found the rapid progress of the lunar return to be a perfect fit for their 24-hour coverage--there was always a new video from NASA public affairs on the state of the Kepler-L2 mission and new graphics of Grimaldi’s location relative to the Earth and the moon. Talking heads vied for time with former NASA astronauts in live segments explaining the mission plan and comparing Grimaldi’s capabilities to the Apollo landers which had preceded it. The differences between Collins’ planned Class-A sortie, the upcoming Class-B outpost, and the planned Class-C base missions were discussed. A particular turn of phrase from NASA’s PAO seized public attention, comparing Minerva 2 to a “camping trip” and the later Habitank-enabled multiple-launch missions to a “cabin in the woods.” These live segments traded off against recorded statements from Neil Armstrong, Buzz Aldrin, Michael Collins, and other Apollo astronauts. However, Foale’s salute to Eileen Collins and her crew, capturing the moment in only a few seconds, saw heavy use as an encapsulation of NASA’s new mission on 24-hour cable news. Ultimately, though NASA had expected the audience to total just over a billion, it was estimated thanks to such coverage that the audience for the descent to the moon and the first steps reached more than twice that number.







Art by @nixonshead and DylanSemrau

 

[e of pi]

Boldly Going Part 23

Though it would nominally spend as long on the surface as an Apollo J-class mission, Minerva 2’s Class-A sortie mission plan was considered by the Minerva team as more of a test flight. There would be no equivalent of Apollo 10’s near-landing dry run. On its first flight beyond Earth orbit, a Conestoga lander would descend to the lunar surface. Eileen Collins and Rick Husband would be engaged in a test pilot’s mission, a trial of radar, engines, and human nerve in a complex ballet that would end, if all went well, with the touchdown of a vehicle massing more than 20 metric tons on the lunar surface. Beside that challenge, three days of EVAs and limited surface science operations were a secondary concern, however much it frustrated selenologists. In order to maximise the chances of success for the Conestoga lander’s trial by fire, any plans for a landing site which might complicate the initial descent were suspect. For all of Minerva 2’s large sortie habitat and the Class-A sortie’s ability to match an Apollo J-class mission for duration and time on the lunar surface, lunar scientists felt like Minerva 2 wasn’t a small step forward, but a giant leap back. They found little sympathy from the mission commander when advocating for a more exciting landing site or reserving less mission margin for descent trajectory contingencies and more for surface exploration hardware and in-situ experiments. While Collins had enjoyed the weeks of geology field training crammed in around landing simulations and surface contingency training, she had set the tone of the mission by studying meter-by-meter orbital photographs of any potential landing site looking not for geological sites of interest but for any concentrations of boulders or aggressive slopes which could impair her crew’s successful landing and safe return. In one heated discussion about conducting multiple fully-integrated tests of each EVA for each potential site to evaluate potential scientific return and the need for site-specific hardware to be fit into the limits of the Class-A sortie’s payload mass, Collins snapped that “we need to focus more on what we’re doing to make sure we land and open the hatch and less on what we do when we get out.” Lunar scientists knew a lost cause when they saw one.

With such a limited scientific capability, Johnson and the science team eventually came to the conclusion that a lower-risk landing site would be preferred. Many of these sites were also of lower geological interest, and thus represented a lower opportunity cost for the limited scientific planning for Minerva 2. Revisiting an Apollo landing site had been suggested, thanks to past “ground-truth” experience of landing risks and potential science on the effects of hardware in-situ on the lunar surface for nearly three decades. Many of the most interesting sites Apollo had considered or visited (such as Taurus-Littrow, Descartes, or Hadley/Apennines) had been visited by J-class Apollo flights which were more capable than their 30-year-advanced successor. Thus, the site team focused on the earliest Apollo landings, where there might still be good returns for relatively minimal time on the surface, and saved their wishlist Apollo revisits and untested ground for the later flights. As had often happened on Apollo, the commander’s influence helped set the mission plan. Thus, the landing was targeted for a site on the surface near Apollo 12 and Surveyor 3 at Oceanus Procellarum, laying the groundwork for the precise surface rendezvous necessary on Class-B and Class-C missions.

The preparations for the descent were covered live on every channel, carrying the footage from the LSAM’s interior and exterior cameras. Unlike the nonstandard television cameras used on Apollo, the footage from Grimaldi and the LSAM Pioneer was broadcast using normal television cameras, similar to satellite TV broadcasts from remote reporters on 24-hour cable news. The footage, filmed at full “standard definition” was relayed to Houston via the LDRS and TDRS networks for processing into NASA’s live broadcasts and cable television’s live coverage--but along the way, it was also received in real time by the crew of Space Station Enterprise. The scene was captured in a famous photograph of the crew clustered around the television in the habitat’s wardroom/galley, attentive to footage on their projected television screen as Grimaldi and Pioneer separated for the final orbit before descent initiation. However, once again the footage recorded by NASA astronaut Don Pettit on the station’s VHS camcorder captures better the true atmosphere. Though the crew had been focused before their launch on preparing for their stay on Enterprise, all had spent at least some time thinking about the chance to fly to the moon. Some had participated in early design activities, procedure testing, or found a way to sneak time in the simulators in Houston. Almost by definition every astronaut in the corps was someone whose memory of watching Neil and Buzz land on the moon 30 years prior had been a formative experience. However, they were no different from the audience watching the mission on their home televisions: aboard a station remote from Houston or the moon, there was nothing they could do to support the mission. The crew was as well-informed and tense as anyone in mission control as they watched their fellows proceed to the surface of the moon. It was a rare astronaut who hadn’t spent some time thinking about getting a spot on a future mission, and most knew the procedure manual for Collins’ crew almost as well as the astronauts on the flight.

The reactions of the eight astronauts diverged. Pettit seemed devoted to documenting the scene, panning between his fellow crew and the scene onscreen, often distracted by the events shown in the process. Other astronauts took places at the wardroom table or clung to the handgrips on the walls. For some of the trained aviators, laser-like focus and the odd tapping of fingers was the only sign of their concern. Others made their nerves more apparent: in the background of Pettit ’s shot, one of the scientist astronauts constantly moved from wall to ceiling to floor of the module as if pacing or searching for a better view as Pioneer began its descent. As the seconds of the descent ticked past, the crew watching Pioneer’s descent from aboard Enterprise could only follow the checklists in their mind and imagine or recall every possible failure drummed into them by SimSups in their own lunar training. The moon in the images relayed to them grew larger, the limb turning into a horizon as the spacecraft pitched up. As Collins bled off Pioneer’s lateral velocity, craters no longer sped past, and instead the landing site slowly slid into place under the lander’s windows and the cameras carrying the feed back to Earth.

The major systems tested in Earth orbit on STS-100-C all performed within expectations. However, flying by internal navigation and the ragged detectable edge of Earth’s GPS bubble, the lander’s computer faced an unexpected headache. In addition to internal guidance, the mission was intended to demonstrate the use of the weak signals from the medium-Earth-orbit GPS satellites which passed by the Earth in establishing a GPS “fix” throughout lunar descent. Though demonstrations on the cruise out to the Moon had shown successful reception and integration of the signals and confirmed accuracy of the “fix” within a kilometer, the receivers experienced larger problems during the actual landing with acquiring and processing the signals while under thrust in the short window after coming out from behind the lunar limb. The result was that just when Collins and Pioneer needed it most, the GPS accuracy vanished. Husband reported to Houston who confirmed they also saw the positional accuracy degrading to more than five kilometers--effectively useless. With a calm that left the issue barely detectable to the average viewer but which sent pulses skyrocketing on Enterprise, Collins shut the GPS out of the control loop, leaving the spacecraft “flying blind” with only internal guidance. Finally, it descended down to altitudes where radar and identification of surface features could get them the rest of the way.

In the VHS tape, Expedition Commander Michael Foale can be seen nodding along as if checking off items in his head as Collins called out surface features and he matched the craters and rilles to the landing profile. Bursts of static occasionally mared the image, both from interference in communications caused by bursts of thruster fire as Collins guided the spacecraft down to the surface and the degradation of one of Space Station Enterprise’s most famous home movies. The fractal pattern of craters and rocks was finally obscured by a sheath of dust, the ground all-too-suddenly revealed to be only meters away below as the spacecraft’s shadow shot into the frame shown on Enterprise television. The crew in the camcorder recording went unnaturally still, as Pioneer settled the last meters to the surface. As the camera view from the moon bumped, shuddered, then went steady, the entire crew held their breath waiting for Collins and Husband to finish checking their status. The words which much of the crew had spent three decades imagining and nine years anticipating brought a round of cheers: “Houston, Pioneer has landed at Intrepid base.” The crew burst into flurries of fist pumps and celebratory zero-g acrobatics, only half-captured on the video. In the exuberance of success, Pettit had lost his grip on the camera while pushing off the galley wall, and the camera went spinning end over end lazily as the crew celebrated their colleagues’ success.

Collin’s and Husband’s landing of the “first woman and the next man” on the moon was marked by a massive peak in viewership, shattering even the Public Affairs Office’s expectations. The surge came thanks to the amplifying effect of days of coverage on 24-hour cable news, headline articles in newspapers and nightly television coverage, as well as a surging interest on the ever-more-accessible internet. In all, over 2 billion people were estimated to have witnessed the landing live in one medium or another, nearly a third of the world’s population - a truly astounding number typically reached only by World Cup Finals and major benefit concerts. The success of a joint American-European return to the lunar surface was identified by many as a crowning achievement as humanity tallied up the events of the previous millennium. For all the build-up, Pioneer’s stay on the lunar surface was not, by itself, particularly impressive. On the first mission, merely achieving a landing with reasonable accuracy was considered a valid goal, and the landing site at Oceanus Procellarum was specifically selected to offer minimal challenges to Collin’s descent. Though some selenogists had criticized the selection of a “milk run” landing site, the wisdom of the relatively low-risk mission plan was shown by its success in spite of the issues encountered on descent.The crew’s training and the spacecraft’s internal guidance paid off. Even with the GPS failure, Collins and the computers put Pioneer down on a landing site less than one hundred meters - just barely more than a football field - away from the center of the targeted 2 km landing ellipse.

The surface mission began almost immediately once the landing was secured. After a few hours of scheduled meals and the obligatory speeches, Collins and Husband descended the ramp for the first of three EVAs they would complete during their stay on the surface. The landing, while historic, was only a minor improvement over the Apollo missions which had come before. A three-day, two-crew sortie to the lunar surface, with a small habitat in a loft over the airlock was a mission capability which would have been familiar to any J-class Apollo crew. The minimal provision for consumables allowed within the sortie lander’s performance meant the air and equipment for outfitting the two large hydrogen tanks as Habitanks was not practical, nor could the time be spared from surface science and more critical systems tests. Though still a home-away-from home, Pioneer was little more than a tent on the lunar surface. By the analogy common in the program, the Class-A missions were “campsites” to be carried out only to prove landing accuracy and the basic functionality of the LSAM. With Collin’s success, NASA announced that further Class-A sortie flights would be curtailed. Instead, the program would move directly into the Class-B outpost series, the so-called “cabin in the woods''. These missions would see a cargo lander precede the crew to the surface, with the two landers and their Habitanks connected, enabling a relatively large habitat to support a full crew of four for more than a full month on the lunar surface. However, these would have to wait for the new millennium--the next lunar mission wasn’t scheduled until the following year in the summer of 2000. During the Minerva 2 mission, millions tuned in for the daily adventures of Collins and Husband on the lunar surface, their launch to rendezvous with Grimaldi in orbit, and their return to Earth. However, when they touched down, many of the audience tuned out even as Enterprise Expedition 11 continued their own mission in orbit around Earth.





Artwork by: DylanSemrau & @norangepeel (Cass Gibson on Twitter) with support from @nixonshead (AEB Digital on Twitter)

 

[TimothyC]

Boldly Going Part 24

While the return to the moon received the majority of press coverage and public interest available to NASA’s activities, it was by many measures the smallest of NASA’s ongoing human spaceflight programs. Collins’ crew had embarked on a mission lasting barely more than a week, involving two Shuttle-C flights, and spent just 3 short EVAs on the lunar surface. Later missions would double the number of LSAMs used and give Class-B outposts nearly an order of magnitude more capability. Still, they were far short of the manpower and time invested in the regular launches of Space Shuttles both on their own and to support the launch of crew and new modules to Space Station Enterprise, which was still itself, under assembly. The habitat areas and solar power generation had completed expansion, but the new laboratories had only begun to launch. While the new European Columbus laboratory was a massive step change from the old Spacelab-derived Leonardo Laboratory Module originally launched in the station’s cargo bay more nearly a decade before, it was still just a fraction of the station’s intended scientific capabilities. The rest of 1999 saw the continuing buildup of the station’s new laboratories, consuming another three Space Shuttle launches. One of those launches was the core of the multi-module Japanese Laboratory complex, though the exterior “porch” with its own small robotic arm and the small removable “storage closet” which would be used for logistics transfer to the lab complex fell to the manifest for 2000. The last two Space Shuttle assembly missions to Enterprise for the millennium carried up the Japanese-built Node 2, attaching it to the zenith port of Enterprise’s Leonardo Lab, and then attaching the new European-built, American-outfitted US Lab Destiny to Node 2’s forward Common Berthing Mechanism. The new node opened up space for the addition of a second back-up Kepler lifeboat, as well as providing a place to mount the new American Laboratory.

Although the lunar return had grabbed the headlines, 1999 had been a coming-of-age for Space Station Enterprise. The year had seen the completion of the main elements of the new truss, tripling the station’s generating capability and providing power for the new laboratories which the station’s crew of eight were now hard-pressed to keep fully staffed. Seven Space Shuttle missions had flown to the station: five assembly flights plus two flights carrying one of the stations’ logistics modules and a rotation of the station’s lifeboats on their staggered one-year stays on-station. Expedition 12 took over a station wholly distinct from the barebones shack in space which Expedition 1 had encountered when they began permanent occupation of the station only four years prior. The workhorse of the station, of course, was the Space Transportation System and the Space Shuttle orbiter fleet. Between the lunar return mission, space station logistics, and Space Station Enterprise assembly missions, there had been nine STS flights flown--breaking records not seen since just before the Space Shuttle Discovery tragedy 13 years prior. However, unlike the flat-out sprints which had contributed to missing Discovery’s fatal tile damage during ascent, the orbiter fleet and their operations were increasingly robust.

The requirement to constantly support Enterprise on orbit had required Johnson Space Flight Center in Houston to add significant staff in Mission Control and other oversight duties, and the need for a peak in station assembly flights nearly aligned with the peak launch requirements of the lunar return program had been foreseen for more than five years. With a flush budget still flowing thanks to President Clinton’s continued support of the international Enterprise space station program and the joint Euro-American lunar return, Johnson Space Flight Center and associated KSC launch and landing teams were more than capable of fully supporting three simultaneous spaceflights, enough for Enterprise, a Space Shuttle, and a lunar mission at the same time. Indeed, NASA’s human spaceflight program was, if anything, better able to handle the uptick in flight rate than they had been for routine crew-tended operations of Space Station Enterprise in the early years of the decade. The system was also getting safer and more capable: with the delivery of another twenty SSME-35 engines, Lockheed Martin was able to finish and deliver the required reusable LRB engine pods to enable the first use of LRBs to replace SRBs on STS-117, the final launch of the year. The LRBs were not only safer and slightly cheaper to operate than the Thiokol-manufactured segmented SRBs they replaced, but were also better performing. Just as with the Shuttle-C, they boosted Earth orbit payload by as much as 5,000 kg. This had enabled STS-117 to launch the American laboratory module Destiny fully outfitted with scientific equipment, and enhancements to the station’s ECLSS already fully pre-integrated, not to mention enough food and consumables to save an entire additional Space Shuttle flight for the year.

Enterprise completed her first decade in orbit as a massively successful science platform. Born of mistaken intelligence and expedient improvisation, the new millennium saw the former orbiter stack now the core of a gigantic orbital outpost. With its two outboard truss modules yet to launch, the station was still longer and wider than a football field, offering a total pressurized volume of more than 1,300 cubic meters while massing more than 450 metric tons. A crew of eight, with frequent visitors nearly doubling their numbers, spent their days working in and around four capable laboratories. When former Senator John Glenn became the oldest astronaut to visit the station on STS-114 aboard Space Shuttle Endeavour in 1999 shortly after leaving office, he summed up the situation by saying,”In my days with Project Mercury, we had a spacecraft you didn’t board--you put it on. It’s remarkable to get to see myself just how much things have changed.” While most visitors to the station were put up in “guest quarters” on the old OV-101 mid-deck, Glenn was given a place in the main habitat module in the former LOX tank. Flight Engineer Don Pettit, who had continued his rookie flight aboard as part of Expedition 12, vacated his larger personal quarters for the once-and-future astronaut. The small personal quarters available for the permanent crew were more than twice as large as Glenn’s entire Freedom 7 spacecraft. Officially as an administrative measure in recognition of Glenn’s participation in ongoing Space Station Enterprise’s biosciences experiments, Glenn was temporarily assigned as a Mission Specialist for Enterprise Expedition 12.

Glenn spent the 17 days of Endeavour’s visit to the station involved in a variety of experiments intended to compare the performance of the elderly in microgravity to that of NASA’s normal astronaut pool, including both physical and mental evaluation. One of the highlights of Glenn’s time as a Mission Specialist was becoming not only the oldest Astronaut, but the oldest person to conduct an IVA. As a test of the ability to carry out EVA, Glenn and Pettit made a 2-hour IVA inside the near-vacuum of ET-007’s still-vacant hydrogen tank, a massive space that nearly matched the entire pressurized volume of the station. NASA had yet to find a good application for it, so it tended to be used for experiments which required large open volumes of either atmosphere or near vacuum but minimal exposure to radiation or debris. Glenn’s IVA, a simulation of actual EVA with no risk of falling “off-structure,” was one such example. As was partially expected, Glenn found the EMU extremely difficult to maneuver. Although he was able to assist in many internal activities that required only a sharp mind and attention to detail, spacewalking was clearly a young astronaut’s game. Some accused the IVA, and indeed the entire mission, of being little more than a publicity stunt, but NASA found great value in the biomedical data Glenn’s mission produced. The visit of a Mercury astronaut to the station capped off a massively successful year for Enterprise. Only a few major components remained to be launched: the last elements of the Japanese complex, the outboard truss solar arrays, and a number of external experiment pallets on the truss which would complete the station’s major expansion, resulting in a configuration which would remain stable for over a decade. The turn of the millenium marked a new beginning for America’s marque outpost in orbit.

The end of the millennium was more of a mark of oncoming doom for the other major space station on orbit, the Russian Mir. Visits by American Space Shuttles had occurred a few times during the mid-90s as outreach, along with Russian exchange missions to Space Station Enterprise. A significant portion of the station’s operating revenue--and of the Russian human program as a whole--came from funding provided by the French space agency CNES and ESA to provide for the permanent presence of a French or European astronaut on every Mir mission. These visits to the station, including the use of the dedicated Euro-French Priroda laboratory module helped stake France’s claim to being the only nation with astronauts in orbit on two space stations. However, by 1999 the station was growing increasingly ramshackle. Despite the added French funding, the station’s solar arrays continued to fall into disrepair. While Enterprise saw its solar generating capacity increased threefold from 50 kW, Mir’s seemingly-random pincushion of aging arrays struggled to provide more than 30 kW. The loss of one of Kvant-2’s two solar arrays in a collision during an attempt to test the TORU manual docking system on Progress M-34 was a worrying sign that the station’s ongoing viability was questionable. The French astronaut aboard, Jean-Jacques Favier, was not made aware of the test until it was already in progress, and a cascade of failures including poor crew sleep scheduling and oversights in cargo loading led to the Progress coming in off-axis and too quickly. CNES officials were livid, especially when a subsequent EVA established from the shattered remains of the solar arrays that the Progress passed within centimeters of the module‘s hull, risking a complete depressurization.

In the aftermath of the collision, French and ESA officials demanded concessions from the Russian space program, including more input into flight event scheduling on the station. This threat was backed up by a significant trump card: with ESA’s new Columbus lab module due to launch shortly to Space Station Enterprise and participation in the American lunar return, France placed less value on maintaining access to an independent station as a counterbalance to the vagaries of American domestic politics. However, the Russians had already been trying to construct a path forward for a new station to replace the aging Mir, creatively dubbed “Mir-II”. During the waning days of the Soviet Union, the plans had been grandiose. In an ironic twist, Space Station Enterprise had inspired the Soviet Union to consider options in the late 1980s for Energia-launched stations. By launching on Energia, the payload volume and mass would be available for either a pre-integrated set of DOS and FGB modules or a new custom module size. Plans were even considered for an Energia-launched Mir-II which would have had several of the modules pre-integrated within Energia’s fairing, as well as providing its own version of Enterprise’s intertank passages to allow for outfitting the Energia core stage on orbit. However, the fall of the Soviet Union downsized and delayed plans for a Mir successor much as it delayed the launch of portions of Mir itself.

As envisioned in 1997 planning, a reduced Mir-II was to be built using the DOS-8 base block and the Spektr laboratory module. Both modules were built either for or as a backup to Mir but neither flew due to lack of sufficient funds for outfitting and launch. Completing the station would be several small modules, including two spherical nodes, a larger solar power module, and secondary lab facilities located in miniature research modules. While DOS-8 and Spektr would house most of the critical systems, the Russians hoped funding could eventually be obtained for additional modules to house even more power generation, as well as potentially providing residence for international science or tourism. Despite the reduced scope, lining up sufficient funds to complete the project had always depended on continuing European involvement in the station, and CNES and ESA knew it. If Mir-II was to go forward with their participation, they demanded a relationship with a more equitable balance of control, similar to or even better than the situation they enjoyed on Enterprise. Their plan was to outfit the station with their own laboratory module, derived from the “Automated Transfer Vehicle” they were developing as a logistics vehicle for ongoing barter negotiations aboard Space Station Enterprise. The ATV core module would, by its nature as a logistics vehicle for Enterprise, also include its own solar power generation and orbital control systems. ESA and CNES had already been pointing out that this rendered the new European “Power and Research Module” a backup for the DOS-8 primary systems, and effectively capable of being a station all its own. This capability, and its attraction, was deeply rooted in ESA internal proposals for a free-flying microgravity research outpost or miniature space station using the same hull.

The 1997 collision threw gasoline on the fires of these discussions. CNES and ESA knew they had the Russian program over a barrel, and extracted three major compromises which they claimed would help ensure superior organization of the new Mir-II project. First, CNES would maintain permanent ownership of the FGB module whose completion they would have to help fund. Second, unlike Mir, primary flight control of the Mir-II space station would be shared between a new ESA-operated CNES facility in Toulouse and Russia’s traditional mission control in Moscow. Third and finally, any flights by astronauts sent by any sovereign nation not represented in ESA or by any private tourists regardless of their origin would be cooperatively arranged between Russia and ESA. ESA, CNES, and Russia would all receive dedicated shares of the launch revenue, with the remainder split between the program which provided the launch and the program which provided the return. The language was written with an eye towards potential reciprocity, allowing ESA and CNES to fly tourists or sovereign nation astronauts to Mir-II aboard Kepler capsules, but such missions were not high on their priority list and the reciprocity in fund-sharing was largely a sop to Russian pride. The third condition fundamentally boiled down to ESA and CNES extracting a tax on any space tourists Russia flew to the station, but did not restrict Russia from arranging such flights in whatever quantity and at whatever price they were able to find buyers. With serious issues with Mir, Euro-French agreements on funding, and a path to profitability of the station through tourism flights, the Russians agreed to all three points, resulting in the formal approval of Mir-II in late 1997. Russian program leadership projected launch of the initial elements in 2001, though CNES and ESA privately anticipated launch to be delayed at least a year from that. While the new station would still be barely a third the size of Enterprise, it would continue the Russian program as a going concern and the tourism flights cleared by the French and European leadership would be a critical part of the ongoing budget of the Russian program.




Artwork by @nixonshead (AEB Digital)

 

[e of pi]

Boldly Going Part 25

The new millennium saw NASA facing the challenges arising from its own success. The lunar program had succeeded in meeting the unofficial goal of a return to the moon before the decade was out--and before the thirtieth anniversary of the Apollo 11 landing. The goal had never been officially codified, but the relevant dates had been specifically designed to be reasonably met when President Bush had given the Space Exploration Initiative speech in 1989. Only the delays in the original program authorization and then in fielding the Shuttle-C’s new Liquid Rocket Boosters had cast doubt on the ability of the agency to meet their objectives and lunar schedule. Similarly, the new millennium saw Space Station Enterprise’s largest expansions nearly complete, with only a few more launches remaining to finish the orbital outpost. The availability of sufficient Liquid Rocket Booster engine pods to serve Space Shuttle launches as well as Shuttle-C lunar cargo missions also brought benefits for the Shuttle program, as the safety of the vehicle was increased even while cost and handling times between launches were reduced. The next three to five years of NASA’s future were well in hand, with the reduced costs of Shuttle, the completion of Space Station Enterprise, and the preparations for the first multi-launch lunar missions. However, the success in all of their 90s-era objectives left NASA’s long-term strategic planners eyeing the future and debating what new challenges could come over the horizon.



Though the dual-launch Class-B lunar outpost mission planned for 2000 was hotly anticipated by the public, internally NASA’s Florida operations teams were most focused on the complete phase out of the Solid Rocket Boosters for ordinary Shuttle missions and their replacement with the Liquid Rocket Boosters. The change not only came with improved payload capability and reduced maintenance, but also eliminated major areas of risk, improving performance, safety, and cost. Not only were the new SSME-35 engines easier to shut-down in an emergency than the old SRBs, but the pods’ five-engine design allowed them to launch with 80% throttle. Thus, the new LRBs would be capable of performing a nominal mission even with a single engine out right off the pad. The added thrust of the SSME-35s and the lower mass of the stack also meant that it was possible to reduce the throttle setting on the Orbiter’s SSME-69 engines from the usual 104.5% to “merely” 100% while still increasing the payload of the stack. Another benefit would come from changing how the Space Shuttle stack handled the “thrust bucket,” an aggressive reduction in engine power carried out before and during the time of peak pressure on the rocket to reduce “max-Q.” The maneuver was nick-named for the shape it made in SSME-69 telemetry traces for thrust and other values. The existing SRBs required much of the thrust bucket to be handled by the Orbiter’s three main engines, moving them from 104% of rated power to just over 70% power, then throttling back to 104% at the conclusion of the “bucket”. While the grain structure of the SRBs allowed their thrust profile to be “programmed” geometrically, the new LRB’s ten SSME-35 engines allowed a true throttle back of the boosters. Even with the added stress of a requirement to cycle from 80% thrust to 67% thrust and back during max-Q, the SSME-35’s short firing time during a mission and relatively low throttle setting would be much lower stress than the existing SSME-69 profile. These gentler stresses suggested that the time between overhauls for the pod’s engines should be even higher, and maintenance reduced over even that of the Block II SSME-69 just being introduced [1]. For the SSME-69’s part, eliminating the aggressive “thrust-bucket” throttle-down and throttle-up mid-burn would add to the Block II’s benefits in minimizing maintenance, further reducing costs of the Shuttle for both Enterprise support missions and independent flights to other orbits.

Lockheed Martin, who had inherited the LRB and related Atlas III NSSL program from General Dynamics through the complex aerospace mergers of the post-Cold War drawdown, stood to reap tremendous benefits from NASA’s desire to replace SRBs with LRBs on all future Space Transportation System flights, whether they be Shuttle-C or conventional Space Shuttle missions. However, the DoD had focused many of its low-mass missions onto the ATK Heimdall vehicle. This desire was driven both thanks to a better fit of the Heimdall family’s performance to the missions required (particularly in its single-stick Heimdall 31C configuration) and congressional and internal advocacy for helping to preserve strategic missile development and production capabilities. Lobbyists reasoned that with Shuttle and Shuttle-C supporting it, there was little risk of Atlas III fading away without commercial or DoD support, but solid fueled rocket production continued to be a strategic asset until and unless a new major missile program was begun. The preference for the new partially reusable Atlas III and Heimdall boosters for even NASA missions spoke to new doubts about the Space Transportation System which dominated NASA and DoD thinking during the tail end of the nineties, despite the Space Shuttle program racking up records in support of Enterprise’s rapid expansion and the Shuttle-C debuting for lunar flights. Neither NASA nor the DoD was wholly comfortable having all their eggs in one basket when it came to critical space launchers, and the early months of 2000 helped demonstrate why.

The veteran ground crews at Kennedy Space Center had been running at full tilt throughout the high tempo of operations in 1999, and were ready for more. However, the infrastructure was less capable. Issues with wear on ground support equipment from deferred maintenance resulted in heavy delays to both of the first Space Shuttle launches of the year, with STS-118 being delayed by more than four weeks due to the need to replace both the stack and service structure sides of the newly-installed cryogenic umbilical connector for the portside LRB. Though similar interface issues had been encountered before, the wear of multiple missions and changing weather meant that the umbilical had fallen out of tolerance, resulting in persistent and dangerous hydrogen leaks around the stack. The delays to launches of Enterprise logistics and the remaining station modules helped push the launch of the two Shuttle-C flights required for pre-positioning the cargo element of the first Class-B Habitank outpost into the summer, the first of several delays which would eventually push the crew launch for that mission into 2001.

The Space Shuttles were also showing their age in other ways, both on their own and in comparison to the newer portions of the American launcher stable. The hypergolic Auxiliary Power Units (APUs), OMS engines, and RCS thrusters of the Space Shuttles required major sacrifices in ground handling. The electrically-driven aerodynamic and gimbals and ethalox maneuvering thrusters of the new Shuttle-C engine pods mitigated these issues, making a vehicle safer and easier to work on and around. Moreover, the payload increases for the Space Shuttle came just as the completion of the expansion of Space Station Enterprise rendered such increases less and less relevant--while the logistics payload of the Space Shuttles was increased by the better part of two tons, the large truss and laboratory modules whose design could have benefitted from greater payload were already launched. Routine cargo and crew launches depended more on payload bay size than on launch mass, and the 100-ton mass of the Orbiter was almost overkill for many of the missions it would be called on to support now that its assembly was completed. While the costs of the Space Shuttle were reduced by the LRBs and process improvements to “only” two to three hundred million for each additional flight made in a year, this was still several times the cost of launching a logistics vehicle on other existing launchers like Heimdall or Atlas III--a fact driven home by ESA’s first independent launch of a crewed spacecraft with the Kepler-C capsule Johannes Kepler and a crew of four ESA astronauts to Space Station Enterprise on top of the new Ariane 5 launcher in March, 2000. The four-person crew stayed three weeks onboard the station and assisted in several time-critical EVAs to support outfitting the ESA laboratory’s external payload mounts. The prime purpose of the mission however was a statement that ESA didn’t require NASA assistance in launching crew or cargo to the station--a demonstration of independent launch capacity crucial to ESA’s pride. It did not escape NASA’s notice that despite being less capable than a full Space Shuttle launch, the cost of the mission ran to half that of a Shuttle flight, and there would be times in the coming years where making any logistics flight on time and for a lower cost would be more important than the absolute cargo or crew capacity of that flight.



Space Station Enterprise itself was wrestling with its purpose in the aftermath of its expansion. For almost five years, the space station had been a “self-licking ice cream cone”: the station’s crew had been aboard first for the manual work of outfitting ET-007 LOX Tank habitat, then the installation and outfitting of the expanded solar truss and laboratory facilities. In other words, the raison d'être of the station had been its own expansion and operations. Now, with that expansion completed, the station had to move into an operational phase where every hour of crew time not spent in a laboratory or critical maintenance activities was a drain on the program budget, as NASA tried to excite researchers and commercial partners about sending experiments to fill the station’s labs. The station remained the flagship for humanity’s exploration of space, at least until a permanently-crewed moonbase was constructed. NASA still continued to search for additional applications to help justify its ongoing operations, and for ways in which the station’s capabilities and technologies could be leveraged for the next generation of space development. With the station’s first major expansion complete, NASA was still looking for any way possible to build on its success in the future, particularly in ways which would benefit other programs in Earth orbit and beyond.

One example of this came during the 2001 servicing mission to the Hubble Space Telescope. In addition to carrying up new multi-ton cameras and replacing critical systems such as gyroscopes and star trackers, the crew of STS-125 also installed a new docking ring and optical target on the aft end of the telescope, which would enable it to receive future uncrewed tugs for reboost or orbital adjustments. These plans were about more than maintenance. In the long term, NASA was developing a strategy for an Orbital Maneuvering Vehicle to use this docking ring to push Hubble’s orbital inclination from its original 28.5 degrees to a new 39-degree inclination co-orbital with Space Station Enterprise. This would enable the station to act as an orbital dockyard for Hubble, reducing the need for a separate launch-on-need mission in case of issues, as had been the case for STS-125 and other such flights which went to orbits other than that of the station. Moreover, while Space Shuttle missions would still be needed for replacing the multi-ton primary instruments of the telescope, the planned new orbit would enable crew aboard the station to carry out the repair of any minor issues which might arise. Along with servicing Orbital Maneuvering Vehicles or Orbital Transfer Vehicles, this kind of “orbital dockyard” service would also be of value for NASA’s future long-term plans.

As NASA began to update their 1989-vintage Space Exploration Initiative visions for space exploration to include a new journey to Mars, finding ways for the new program of record to continue to justify supporting Enterprise was not officially a critical factor in architecture selection. Still, when choosing between options which were otherwise equally effective for developing design reference architectures for NASA’s new mars plans, the options which could make use of NASA’s existing orbital assets and experience were favored over those which did not tie into the existing lunar architecture and the massive recent investments in Enterprise. Eventually, this would lead to the last major overhaul of Enterprise’s original legacy STS-37R hardware in the years to come. For the moment, though, Mars plans remained far off, awaiting Congressional approval. In the meantime, NASA had to negotiate scheduling ongoing station operations, Shuttle flight rhythms, and the launch of 2001’s Minerva 3 “cabin-in-the-woods” lunar outpost.

[1] SSME Blocks are complicated. The following is per Jenkins:
SSME First Manned Orbital Flight (FMOF) were used for STS-1 through STS-5, and were rated only to the maximum originally specified for the engine. This number is set as 100% of rated thrust, and future engines were certified for higher.
SSME Phase I were used through Challenger (STS-51L), and were rated at 104%, and in theory 106% to support very heavy payloads (up to 65,000 lbm) and polar missions.
SSME Phase II were used post-Challenger, and retained the earlier rating of 104%, but not 106%. Phase II and prior engines are referred to as RS-25A by Rocketdyne.
SSME Block I first flew in OTL on STS-70 in 1995, and utilized the new Pratt & Whitney High Pressure Oxidizer Turbo-Pump, a two-duct powerhead, and a few other modifications.
SSME Block IA first flew in OTL on STS-73, also in 1995, and was a Block I with a modified main injector and modified temperature sensors. Rocketdyne refers to both Block I and Block IA as RS-25B
Block IIA first flew OTL on STS-89 in January of 1998, and integrated all of the changes planned for the Block II except the new High Pressure Fuel Turbo-Pump (HPFTP). This included the new Large Throat Main Combustion Chamber (LTMCC) that reduced the expansion ratio from 77.5 to 69.5. The corresponding reduction in chamber pressure and ISP was countered by the change from 104% thrust to 104.5% thrust. Rocketdyne designated this configuration the RS-25D
Block II first flew OTL on STS-104 in 2001, and added the HPFTP to the Block IIA design. NASA delays to the HPFTP design (done by Pratt & Whitney) historically slowed this effort. Rocketdyne Designation for the Block II was RS-25C

In this timeline, Block II work is never slowed, and the full suite of Block II changes is introduced around the time of the historical Block IIA. These changes are made in parallel with the introduction of the SSME-35 nozzle and chamber alongside the SSME-69 chamber and nozzle. Here, by 2000, the SSME-35 and SSME-69 in service are both using Block II chambers, turbo-pumps, and probably throats.

A short (and free!) version of SSME history can be found in this NTRS paper, entitled Space Shuttle Main Engine (SSME) Options for the Future Shuttle.

Artwork by @nixonshead (AEB Digital)

 

[TimothyC]

Boldly Going Part 26

Minerva 3’s month-long trip to the moon in 2001 would be the first demonstration of the Habitank concept in-situ on the lunar surface, extending the legacy of Enterprise’s wet lab design to the moon. As a Class-B outpost mission, Minerva 3 required a total of four Shuttle-C launches, with each pair being used to send a separate LSAM lander to the lunar surface. The first lander was pre-positioned in Tsiolkovsky Crater in the late summer of 2000. Freed from the need to carry an ascent vehicle, this vehicle - only the second LSAM to land on the lunar surface - carried another 16.5 metric tons of surface payload. Though also including various power systems and surface exploration gear, the primary payload was the massive Service Core, a lunar equivalent to Enterprise’s node modules. The module offered an 8 meter long, 4.27m diameter core unit filled with consumables and life support systems. It was fitted to act as the nexus of the Class-B outpost while offering the potential to expand into a Class-C lunar base. To this end, it housed six deployable inflatable passageways, with one on each end and two along each side of the module. The side passageways were positioned so that when the core was positioned properly, the two inflatable passageways on a side of the module could be connected to ports on the end of the two Habitank modules on an LSAM, tying the core to the LSAM’s pressurized volume in two places. A second LSAM could then be attached on the other side, forming the Class-B configuration. In this “figure-8” layout, the outpost would consist of two airlocks (one on each LSAM), one sortie hab, the ascent module cabin, four Habitanks, and the core module--nine rooms totaling more than 1,200 square feet of floor space. Though called a “cabin,” even this early outpost would be a spacious base for exploration. The two end passages on a Lunar Core Module could be connected in series, allowing the expansion from the two-LSAM medium-duration outpost into a full lunar base of nearly arbitrary size.



The second major payload carried by Minerva 3B’s LSAM was one of the program’s most controversial decisions: the use of a nuclear reactor for outpost power generation, providing all the power a base could require through the two-week lunar night. The TOPAZ-II reactor would constitute the main Russian contribution to the lunar program, providing 5 kW of electrical power from just 12 kg of Uranium contained within the 1,000 kilogram reactor system. The political benefits of using a Soviet-derived nuclear reactor and avoiding Soviet space scientists and nuclear engineers seeking alternative employment was a powerful cudgel used to help overwhelm Congressional opposition to the application of nuclear power in space.The benefits of a powerful and consistent energy source for future outposts helped ensure its selection by NASA. However, even given the successful demonstration of TOPAZ-II for eight months on the lunar surface prior to the arrival of the Minerva 3 crew in 2001, opposition by anti-nuclear advocates was strong--though often mistaken, as the peak of protests came during the launch of the Minerva 3B mission on STS-127, when the reactor had already been delivered and operational on the lunar surface for more than eight months.



In an echo of the STS-38R Enterprise commissioning flight, when the crew of Minerva 3 arrived on the lunar surface thanks to another pair of Shuttle-C launches in early 2001, their first task was the assembly of the outpost they would occupy, a project which would consume most of the six Earth days remaining before lunar night. Thus, bare hours after landing, the crew of Minerva 3 deployed the main cargo of their LSAM: four of the golf-cart-sized lunar rovers which were the utility vehicles of the Minerva surface architecture. Officially the Multi-Utility Lunar Exploration System, these “mules” were the packbeasts of the Minerva architecture. Each had four wheels: two large 1.5m diameter forward wheels, and two smaller trailing wheels, with steering somewhat like a tricycle provided by a hinge between the front axle and the main chassis. Two “mules” could be coupled together, providing supplemental carrying capacity and redundant batteries and motors in the event of any failure. This redundancy was key to allow a more safety-conscious NASA to qualify the system for extended traverses well beyond walk-back distance. A single mule pair could carry the entire expedition, and thus a full-crew traverse was protected against the complete failure of even two of their four mule prime movers. The mule’s awkward wheel arrangement was a legacy of their secondary role: bolt-on casters for the moving of hardware on the lunar surface. A capture system on each MULE rover allowed it to attach to a trunnion on the leg of the LSAM or one of the footpads of the Minerva core module and lift it off the ground, leaving the smaller rear wheels in the air and the weight of the leg balanced on the two large forward wheels. With all four MULEs attached, the LSAM or Minerva core was essentially putting on roller skates, and could be transported at as many as two kilometers per hour.

After landing, the crew’s first EVA was spent deploying and guiding the four mules to attach to the legs of their Minerva 3B LSAM. Thus, their LSAM was converted into a massive pressurized rover. That afternoon and evening, the crew used the mules to tow their LSAM along the first few hundred meters of the traverse to the landing site of the Minerva 3A cargo LSAM. The Conestoga lander’s program name was once again apt, a massive vehicle bound for a frontier pulled by mules. This legacy yielded the crew’s name for their Minerva 3B LSAM: the Prairie Schooner. The next day, the Schooner completed the traverse to Minerva 3A’s LSAM landing site, and the crew set to work in an afternoon EVA configuring the outpost. The first task was using a remote-controlled mule to drive the TOPAZ-II reactor to its final emplaced potion at the end of a 300 meter long power cable. Next, the crew used the Minerva 3A LSAM’s onboard crane to lower the core module to the surface, then used the mules to position both the core module and the Prairie Schooner into their proper placement relative to the LSAM 3B lander. The third day on the surface was spent attaching the four pressurized tunnels and coupling the base’s three modules together. Overnight, the ground crew carried out tasks to fill the four Habitanks with breathable atmosphere mixtures. Day four on the surface marked the first day without an EVA, as the crew worked all day inside to open up hatches from the airlock into Schooner's two Habitanks, gain access to the Core Module from there, then repeat the process to open up the LSAM 3A Habitanks. With all five major modules linked into the same pressurized volume, life support systems, and power grid, the crew was able to spend the final days of lunar dusk on a series of short-range EVAs, conducting local site science and emplacing several small experiment packages in the long lunar dusk.

Over the course of the two-week lunar night, Minerva 3’s crew settled into their new base. They finished outfitting the four Habitanks into a short-duration outpost. The two Habitanks aboard Schooner were fitted out as bunkrooms, ensuring that should a problem arise during the night all four expedition crew would already be aboard the LSAM carrying an ascent stage. The two Habitanks aboard the Minerva 3B cargo lander became a geology lab and an EVA preparation area, while the core module contained the small galley, wardroom, and outpost control center. With the modules outfitted, the crew moved from engineering into focusing on science. In cooperation with selenologists in backrooms on the ground, the commander and science mission specialists reviewed the samples gathered on their initial traverses and made detailed plans for the exploration to follow once the sun rose again. In addition to the outfitting tasks and geology review, the long lunar night offered the chance for long-duration exploration of the human body in lunar gravity. The downtime meant precisely calculated exercise routines on the outpost’s folding treadmill and weight bench went uninterrupted by the strenuous activities of near-daily EVAs.

By the time the sun rose in March of 2001 and the Minerva 3 crew could go about the final two weeks of their month on the lunar surface, the legacy of Enterprise had been well and truly extended to the moon. The Minerva crew made use of in-space conversion experience developed on Enterprise and Enterprise-heritage EVA suits, exercise equipment, and biomedical expertise. When the Minerva 3’s crew departed the lunar farside, they left behind a powerful outpost for any future explorers to further develop. Within the ten-year lifespan of the cabin’s TOPAZ-II reactor, the base could be easily repressurized and reactivated for expansion. Thus, the four Class-B outpost missions would each lay the groundwork for a full lunar base at multiple sites around the moon. For those who doubted such a capability, a fresh explosion of applications for platforms in Earth orbit provided a model to examine closely.










Artwork by: @norangepeel (Cass Gibson on Twitter), @nixonshead (AEB Digital on Twitter), & DylanSemrau[/I]

 

[e of pi]

Boldly Going Part 27

With the launch of Minerva 3 in 2001, NASA had established the first of a new generation of human outposts beyond Earth orbit. However, it wasn’t the only new outpost launched that year. After many delays, Russia finally launched the first modules of Mir-II. Funded by contributions from Europe and a number of private tourists, Russia spent the next two years launching and assembling their third generation modular space station in a 52 degree inclination orbit shared with the existing and still intermittently occupied Mir-I. Assembly began with the DOS-8 Zvezda station core module, then the Spektr lab module. As soon as the first modules of the new station were launched, it became home not only to ESA astronauts and spationauts, but also to a stream of private tourists whose dollars helped pay the bills of the cash-strapped Russian program. The first resident in the temporary tourist crew quarters in Spektr was internet dot-com billionaire Paul Allen. He had been debating founding his own space launch company for tourist purposes and justified his flight experience as a “fact finding” expedition (for which he was able to take a tax write-off). In 2002, the Europeans launched their Curie laboratory to become the third module of the station. The same small size which made Mir-II less capable than Enterprise in both lab volume and power supply ironically also produced a purer microgravity environment. Though still intermittently disturbed by the motion of tourists and crew aboard, for a time Curie was the preferred site for housing experiments which depended on high-quality microgravity, such as pharmaceuticals and crystal growth. Until the launch of the first Russian power module in 2003, Curie’s 15 kW solar panels would also provide half of the power generated aboard Mir-II, exceeding the capacity of the smaller arrays aboard Zvezda and Spektr.



Beyond being the primary home for microgravity experiments and its contributions to the power grid of Mir-II, Curie was also the debut of a new generation of European multi-purpose spacecraft. The base design, named the Multi-Purpose Space Vehicle, came from coupling an MPLM-derived pressure hull to a service module developed from the Kepler-L lunar crew vehicle.In Curie’s case, modifications were made to the basic MPSV hull to add additional solar panel capacity, uprate her thrusters for on-orbit refueling and longer use, and increase the rated lifespan of her micrometeor and orbital debris protection by providing an outer layer of metal shielding. By removing these modifications, the same basic MPSV design became the “Automated Transfer Vehicle,” a 20-ton logistics carrier for launch aboard Ariane 5. With the benefits of this large additional logistics stream for both Mir-II and (more regularly) Space Station Enterprise, the new ATV would pay the way for a stream of European astronauts to both outposts. With this, ESA continued to be the only agency to maintain a continuous presence on more than one space station. A final derivative of the MPSV bus would stretch this claim further. In 2005, ESA launched their Galileo space platform. Galileo was the full embodiment of the concept of a “Man-Tended Free-Flyer” which had originally spawned the ATV type and the Columbus and Curie lab modules aboard Enterprise and Mir-II. By European reckoning, Galileo was both a tug and a space station. Modifications to the MPSV bus for Galileo would consist of the same long-life modifications from Curie, but with only the reduced solar power of the ATV. The performance of Galileo was further increased by adding additional propellant tanks inside the pressurized cabin, taking advantage of the non-toxic propellants selected for the MPSV design. Much like Curie, Galileo featured a second docking port located between the four OMS engines, connected by a short pressurized tunnel to the habitable module. By mounting an APAS port on the main pressurized module at its other end, Galileo was thus capable of both docking independently to APAS ports, or being berthed by robotic arm to a station’s CBM port to transfer the larger ISPRs it was fitted to carry.

Galileo’s first major mission began with its launch in August 2005 aboard an Ariane 5 rocket. Rather than flying to the 52 degree orbit of Mir-II or the 39-degree orbit of Enterprise, Galileo started its career in a 28.5 degree orbit. With its propellant tanks full to overflowing, Galileo began the burns to chase down its first customer: the Hubble Space Telescope. Conducting servicing operations at an orbit distinct from that of Enterprise had been a problem for decades, and the Americans had been heavily interested in solving the problem by relocating the telescope to a more convenient orbit. Unfortunately, Congressional leadership had repeatedly declined to fund the expense of an American Orbital Transfer Vehicle (OTV) or Orbital Maneuvering Vehicle (OMV) which might only be used once. With autonomous docking ability and massive propellant tanks, Galileo was the perfect pinch-hitter for the role of a reusable orbital tug. After three days spent chasing down the telescope, Galileo gently docked to the port left behind four years earlier by STS-125.

Over the next several weeks, a series of gentle burns eased the telescope’s inclination higher and higher. Even with the augmented propellant tanks, Galileo wasn’t up to the task of moving the combined 30-ton stack to a 39-degree orbit coplanar with Enterprise in a single operation. Instead, Galileo burnt off just over 5 metric tons of the ethanol-LOX propellants, adjusting Hubble’s orbit by 4.5 degrees. Leaving it at the new 33 degree orbit, Galileo continued on to Enterprise using the more than three tons remaining in its tanks. Arriving in September 2005, Galileo docked and was refueled with supplies sent up on the Space Shuttle and ATV. With its internal tanks topped off, Galileo burnt its way back to Hubble and powered it through another 3.5 degrees of inclination adjustment. The reduced capability, in spite of the increased propellant load, came from the need to not just boost down to Hubble, but also to retain propellant to come back to Enterprise for the final refueling which would bring Hubble to an orbit coplanar with the station. The complex operations interrupted Hubble’s observing time off and on through the rest of 2005, but by 2006 the telescope had been inserted into its new 545 kilometer 39 degree orbit.



With this first mission complete, Galileo was berthed to the station rather than docked, and began to receive an overhaul to suit its new role not as just a tug, but as a free-flying scientific platform which could also serve as a tug. This new mission would not require the large propellant tanks needed for the Hubble move, and the tanks could be reused for other purposes. The LOX capacity was repurposed to store additional oxygen and nitrogen to sustain a breathable atmosphere during independent operations. The ethanol tanks were drained, purged, and eventually refilled with water for both cooling and bioscience research. As a result of the slow “boiloff” of residual stored ethanol from the remaining supplies stockpiled aboard the station, the crew of Enterprise enjoyed a very happy year of holidays throughout 2006. While the tanks were being repurposed, Enterprise crew installed experiments into ISPR racks that had been left empty on Galileo’s launch. These experiments, specifically launched via shuttle and MPLM to Enterprise for installation on ]Galileo, would take advantage of the independent nature of the platform. Smaller and free from crew-induced vibrations, Galileo would offer a dramatically superior environment for long-duration microgravity than Enterprise or even its cousin, the Curie laboratory aboard Mir-II. Additionally, experiments aboard Galileo would be free of the safety concerns that precluded open combustion experiments from being conducted on other stations. After the conversion, Galileo was refueled for station-keeping and cast loose from Enterprise again to take up its own co-orbital position a few dozen kilometers behind the larger station. By European reckoning, Galileo’s largely independent operations made them the third agency to operate their own space station. However, NASA and many American news sources typically regarded Galileo as an adjunct to the American outpost, as integral to its operational tempos and capabilities as Space Shuttle launches, Hubble servicing, or Kepler lifeboat rotations.

By 2009, Space Station Enterprise was at the center of a network of off-Earth outposts. In addition to playing host to a normal crew of 8, which surged as high as 18 during Space Shuttle and European Kepler crew visits, Enterprise also was the logistics base for Galileo which typically orbited within a few dozen kilometers. The Hubble Space Telescope was left in its orbit coplanar with but roughly 50 kilometers above the station, within easy access but far enough away to avoid conflicts with station operations or impacts by station-generated debris. Galileo made roughly annual visits to the main station for upkeep and maintenance, and was also assigned to bring Hubble to Enterprise roughly every 2-3 years for maintenance and reboost. On the moon, the Americans had constructed “cabin-in-the-woods” outposts at the landing sites of Minerva 2 at Oceanus Procellarum, the Minerva 3 mission on the lunar farside at Tsiolkovsky Crater, and the Minerva 4 outpost at Shackleton Crater near the lunar South Pole. The latter had been expanded with an additional pair of LSAMs and an arched, regolith-covered roof, to form “Shackleton Base.” There, drawing on the station’s 8 Habitanks and two Minerva Core Modules, crews were able to stay up to nine months to conduct increasingly detailed examinations of much of the lunar south pole region. The base had begun accumulating the detritus every long-duration human outpost seemed to eventually develop. The base’s galley still featured a cardboard standup of Quark, signed by Armin Shimerman, which the Minerva 4 crew had left behind in the airlock to greet the arrival of Minerva 5’s crew to “Deep Space One,” More noticeably the base also possessed an increasingly large pool of un-converted “surplus” LSAMs which grew by one for every additional crew that visited the base.

As for the rest of human spaceflight, Mir-II had been recently completed, though the station still had echoes of its Soviet roots. Moreover, the constant supply of millionaire and billionaire tourists often gave it a reputation as the tabloid center of spaceflight. The flight of billionaire Charles Simmons and his fiancée Lisa Pérez in 2009 didn’t help matters. The pair were engaged before their flight, and once on orbit revealed their intention to be married in space. They presented a marriage license from the State of California, and asked the station’s rather amused Russian commander to perform the official ceremony. By exercise of the ancient privilege of vessel commanders, he pronounced them husband and wife. The two then proceeded to spend much of their time in the supplementary tourist quarters located in the pressurized module at the root of the station’s portside solar truss. Within weeks, the module (home to two supplemental crew quarters and an additional hygiene station) had shed its original inevitable nickname of the “Orbital Hilton” and been equally inevitably renamed the “Honeymoon Suite.”

Tabloid interest was immediate in the orbital marriage ceremony, and how any ensuing consummation might have been achieved. Other media fanned the flames, if more tastefully. On their return, the newly married couple helped recoup some of the $120 million cost of the 3-month “honeymoon of a lifetime” by publishing a book, which went on to be a New York Times best seller. Largely a boilerplate romance of a dot-com billionaire and a mere dot-com millionaire falling in love over a joint interest in spaceflight, the book’s marketing push teased that it made references to the mechanics of sex in space, a matter of interest to gossip hounds but which the stodgy NASA Public Affairs Office considered verboten. The couple’s time in space was confined to a few chapters near the end, before a discussion of their relationship since their return home, but contained just enough prurient details to titillate the audience turning up for them. However, perhaps the book's most famous line was an assertion that the experience combined with the so-called “overlook effect” of seeing the Earth from space “left them feeling like they were experiencing something no one had ever felt before--a connection that transcended bodies and borders to create a bond to last a lifetime.”

Originally, the book’s marketing had carried the pitch that it was the story of the first married couple to fly in space. In a rare breach of silence about the entire topic however, NASA’s Public Affairs team had pointed out this wasn’t true when the book was submitted to them for comment early in publication. Though the Simmons were the first to be married in space, they were not the first married couple in space. Following a whirlwind romance during training, NASA astronauts Mark Lee and Jan Davis had flown together on STS-47 in 1992. By the time the pair’s romance had come out, the agency had been unable to arrange to replace one or both in time to avoid disrupting the mission of carrying a Spacelab module full of Japanese experiments to Space Station Enterprise. The matter had raised eyebrows inside the agency at the time, but now the Simmons’ honeymoon getaway brought the matter back to the forefront. Officially, NASA refused to answer any questions about any activities the two newlyweds had gotten up to in space in the early days of Space Station Enterprise, before permanent crew were aboard. Presumably then, the pair had been too busy, too professional, or too closely chaperoned by the rest of the crew for anything to result. With the Simmons honeymoon, the matter came back to intense public attention nearly two decades after it had occurred. Divorced since 1999, Davis and Lee were both reluctant to comment on the events of a marriage now a decade in the past or risk the wrath of the NASA PAOs. The closest thing to a public answer came when Jan Davis visited Texas A&M for a speaking arrangement and small-group meetings with aerospace engineering students. According to posts later circulated on the internet, one of the young women in a small-group arranged by the campus Society for Women Engineers had dared ask the question which NASA preferred to never have addressed. Asked if she had found any experience of orbital flight and related activities to yield something like Simmons’ famous line about a “connection to last eternity,” Davis had simply said “I can’t say I’ve ever experienced that myself.”

Some within space advocacy circles shook their heads in horror that in just a decade space headlines had gone from a return to the moon to such tabloid-level tawdry questions. They saw it as a sign that space was becoming just another place polluted by the worst of humanity, not someplace to look for humanity to achieve something better than its worst impulses. Of course, it also reflected that space was becoming a destination for humanity at large, not just for the government-selected and screened few. In some ways, the immaturity reflected the growing maturity of human access to orbit and beyond, as it required regular flights of multiple tourists at a time to a station large enough to assure them privacy. The main practical effect of the controversy was that another three couples expressed interest in registering for a “getaway in space'' aboard Mir-II, further driving space tourism. Given the arrangements for profit-sharing of tourism flights to the station, these deals meant almost $40 million apiece in the coffers of ESA and CNES, enough to ensure the two agencies also developed a relaxed attitude about what private citizens (or at least the ultra-wealthy) might be getting up to in the privacy of Mir-II’s tourism cabins. For all the immaturity of the Earth-side reactions, access to space was becoming increasingly mature. However, portions of the systems for accessing space were becoming not just mature, but worn by age.



[1] Historically not a station mission, obviously, but with a biomedical focus and utilization of Spacelab, the mission would benefit from going there. Moved from the OTL STS-47

Artwork by: @nixonshead (AEB Digital on Twitter)

 

[TimothyC]

Boldly Going Part 28

In 2009, Space Station Enterprise celebrated the end of its second decade in space. The milestone provided a convenient marker for evaluating how NASA’s human spaceflight program had evolved since the station’s launch. At the orbital outpost, NASA had accumulated tens of thousands of crew-days in space in 14 years of permanent occupation, along with various visiting Shuttle crews. After the explosive growth of the late 1990s, the station’s core configuration had remained relatively constant. Instead, the main changes had come with the concentration of space assets like Galileo and the Hubble Space Telescope in orbits near Enterprise. With this concentration and a growing focus on sustained scientific capabilities at the station and lunar outposts, flights of the Space Shuttle to any destination other than Enterprise grew increasingly rare. The Space Shuttle had achieved its role as a space truck to serve a constellation of space vehicles, but its independent operational capabilities were increasingly unnecessary. Instead, these capabilities were overshadowed by the aging of the vehicles themselves and growing frustration with the Shuttle’s maintenance requirements. Rockwell’s OPAMs for the Shuttle-C heavy lifter and Lockheed Martin’s reusable engine pods for Atlas-III and Shuttle LRBs, coming off their own first decade in service, provided a notable point of comparison between the “first generation” Shuttle hardware and the “second generation” spawned by Shuttle-C.

Similar struggles were experienced in the lunar program as the Minerva office moved from early exploration and base development into routine flights to consolidate operations at the three Minerva “Class-C” base sites. With Shackleton Base receiving its sixth crew in 2009, the one-way flights of the descent stages became more and more of a problem. The cost of providing a new Conestoga lander for each crew or cargo logistics flight began to be a significant contributor to the cost of supplying and occupying Shackleton. The Shuttle-C Earth Departure Stage was used for some DoD Atlas III Heavy flights, and the Kepler-L lunar crew capsule shared many of its systems with the fleet of Earth-orbital capsules used for Enterprise lifeboats and independent European crew launches. Conestoga had no such cost savings. The high resulting cost was a restriction on any plans to uprate any of the other Minerva sites to a Class C outpost for intermittent or permanent crew occupation. Indeed, NASA was increasingly considering their future plans beyond cislunar space entirely, which would require costs of the existing programs to be minimized and allow for new development. Discontinuing permanent lunar occupation or ending operations at Enterprise was politically unpopular. Thus, as Mars loomed larger in NASA’s plans, the agency would have to find ways to cut costs in the aging Space Shuttle and Conestoga programs.

The focus on replacing the first generation Space Shuttle and converting Conestoga to a reusable operational strategy reflected the change in NASA’s operations since the two vehicle’s respective births. Though the Space Shuttle had been the workhorse of the American program for nearly thirty years, its roles were being increasingly rendered unneeded by other vehicles. Independent flights with Spacelab or Spacehab to orbits other than that of Enterprise had largely stopped, and Shuttle-C and Atlas III had taken over the role of the American pre-eminent heavy lift vehicles for large probes and lunar missions. Just as the Space Shuttle’s LRBs had increased its payload above that originally envisioned in the 1970s, the assembly of Enterprise was completed largely using the existing SRBs. For a few years, the augmented capability had been consumed with ethanol-LOX propellants to refuel the Galileo tug/station for its task of moving Hubble to near Enterprise’s orbit. Since then, it had largely been employed for whatever odd tasks NASA could find for bulk liquids and solids on the station or simply gone unused in the name of increased redundancy and safety. The higher performance demanded from the full-throttle SSME-69 engines on the orbiters made for higher maintenance requirements relative to the otherwise identical SSME-69 and SSME-35 engines on Shuttle-C and the LRBs respectively. For the latter, as part of an Atlas-III rapid response demonstration, Lockheed Martin and Rocketdyne had recently demonstrated five full-duration firings of an Atlas-III core on a test stand in under a week. Further, the orbiter’s hypergolic-fueled APUs and OMS made for challenges in ground handling and spacecraft processing which the all-cryogen Shuttle-C OPAMs simply didn’t experience. While wearing “bunny suits” to clean and remove an OMS pod for servicing, crews at the Orbiter Processing Facilities couldn’t help but compare the “hangar queens” to the work-horse Shuttle-C Propulsion & Avionics Modules. With their electromechanical actuators and non-toxic ethalox thrusters, servicing a pair of OPAMs for a Minerva lunar mission took less time than servicing a single Shuttle Orbiter for a crew mission.

Spares were also a concern as the orbiter’s primary structures and secondary systems aged. No new orbiter components had been manufactured since the construction and delivery of OV-105 Endeavour in 1991. NASA was carefully monitoring wear and fatigue cracking of the orbiter’s primary structures as they husbanded the spare wings and tail collected from the butchering of OV-101 into Space Station Enterprise. In contrast, Rockwell had delivered a total of five OPAMs in the last decade, culminating in the deliveries of OV-203 George Mueller and OV-204 Richard Byrd in 2002 and the refurbishment of the test vehicle OV-200, retroactively the Pete Conrad, to reach near-flight status in 2003. None of the OPAMs was more than seven years out of a major overhaul, and Lockheed Martin was still intermittently producing batches of LRB/Atlas-III engine pods to keep the operational Air Force and NASA booster fleet over a dozen.

Once payloads reached the moon, the task of ferrying them down to the surface was another bottleneck. As Minerva had moved from sorties and base construction into regular operations, Conestoga’s design advantages had transformed into limitations. While it lacked Shuttle’s direct comparison to the Shuttle-C and LRB, its faults were no less apparent to those who had to work on and fund its operation. Early in base construction, Conestoga’s clever expendable descent stage, with its two Habitank wet-workshop hydrogen tanks, had been useful as every landing in the buildout of the site provided not just crew or cargo, but also free volume. However, by the fourth crew rotation, the number of LSAMs landed at Shackleton began to exceed the capability of the crews at the base to convert or even attach to the base given the limited numbers of ports available on each Minerva Core Module. NASA was required to provide every crew and logistics mission with a new Conestoga for a one-way flight to the moon, where a “boneyard” worth hundreds of millions of dollars began to collect just off the cleared and sintered landing pad. Each new arrival, once its cargo or crew were unloaded, was towed by mule rovers to a resting spot just beyond the berm protecting the base from flying debris. Once in line behind the berm, the precision engineered hardware was simply abandoned in place in case of a future need which seemed to grow increasingly remote. The Conestoga’s greatest benefit - its adaptable expendable descent stage - had become its greatest downside. Even in the early 2000s, NASA had investigated long-term design improvements to let the lander be refilled and serviced in lunar or Earth orbit. This would allow a small set of landers to serve ongoing permanent lunar bases, and let the existing expendable ascent stages be replaced entirely. As Shackleton Base moved into regular nearly year-long crew missions, Conestoga was rarely being called upon to push to the limits of its capacity. Thus, as with Shuttle, the cost of conducting any flight to the lunar surface began to dominate over the benefit of any single marginal kilogram delivered per flight.

None of the issues with Shuttle or Conestoga were new however, and options for fixing them had been in the works for the better part of a decade. Beyond the Conestoga reuse plans, NASA had been entertaining options for a lighter, cheaper, and lower-maintenance “Shuttle-II”. In 2009, they were finally authorized to begin development of a full-on Shuttle successor and the implementation of the modifications to let Conestoga become a reusable cislunar tug and reusable lander. Uncrewed spacecraft had proved their value over the previous decade with the successes of autonomous rendezvous on the Galileo free-flyer/tug and Conestoga cargo landers’ descent to the surface under internal control on cargo flights. For improved safety and reduced performance requirements, the plan was that the new design would not require crew on every mission. Instead, those missions requiring pure cargo performance could use the full capability, while crew missions would carry a crew compartment mounted in the payload bay. Another break came in the elimination of the primary external tank, the largest single disposable element of the Space Transportation System. Instead, the new vehicle’s design would consist of a 5-meter diameter fuselage, with a 12-meter-long payload bay sandwiched between an aft oxygen tank and a forward hydrogen tank. For cargo missions or Kepler lifeboat rotations, the vehicle’s designed payload of 14 metric tons would suffice for most Enterprise logistics purposes. Though reduced from the theoretical limits of the existing Space Shuttles, the net delivered payload would be similar to what current Space Station Enterprise logistics flights could accommodate due to center of gravity limits on abort landings. For crew flights, a cabin module would nestle into the bay, mounting to the same payload trunnions but leaving its exterior hull flush with and replacing the standard bay doors and thermal protection system. The crew module would provide spacious seating for up to 14 astronauts, offering cheaper and more capable crew transport to Space Station Enterprise or other destinations. For safety, the surfaces of the pod inside the bay were to be covered with a single-use ablative heat shield, and the ends of the module would house six massive solid abort motors capable of blasting the crew cabin free of a disintegrating orbiter. This ensured that regardless of any issues on ascent or return, the crew of Shuttle-II had a way to get home. For launch, the new orbiter would be its own second stage. First stage boost would be a series-staged burn more like Atlas-III Heavy, with Shuttle-II hung from the side of a pair of existing Shuttle LRBs. The new vehicle would be able to tie into the same thrust mounts used by the existing Shuttle and Shuttle-C stack and the Atlas III Heavy side boosters. The design was frozen in 2011, and introduction into service was predicted for 2018.

At the same time NASA and the Rockwell-heritage areas of Boeing were working on the revised Shuttle-II orbiter design, Boeing’s McDonnell-heritage division was working on the plans for a reusable Conestoga variant, dubbed Diana. On-orbit servicing of the Galileo ethanol/LOX propulsion system meant NASA was reasonably familiar with cryogenic propellant handling in space. The application of the concept to Conestoga was reasonably straightforward. The main challenge came from the addition of hydrogen to the existing oxygen experience, and with it increased worries about thermal insulation. Efforts to minimize tank penetrations and increase propellant life in storage were aided by the design of the hydrogen system. The two large hydrogen tanks and single spherical “sump” tank, designed to enable a more effective Habitank, also helped minimize their surface area and number of tank penetrations. There were even proposals to use the airlock-to-tank interconnects for in-space inspection and servicing of tanks over extended design life, years down the line. This life was not unreasonable in NASA’s view, since the RL-10 engines used by the vehicle were already nominally capable of dozens of relights in space thanks to its spark-ignited, low-pressure, and low-temperature design burning non-coking hydrogen fuel. If the new Shuttle-II or another vehicle could serve as a tanker, then only moderate in-space servicing and a new crew cabin would be required to transform the LSAM descent stage into a single-stage reusable lunar lander. For the occasional deployment of larger structures, additional drop tanks would help preserve the vehicle’s capability for heavier payloads to the lunar surface. The challenge would depend on much the same factors that NASA’s plans for exploration beyond Earth orbit were hinging on: cost per flight of the new Shuttle-II and the presence of a structure in low Earth orbit for the servicing of smaller spacecraft and the assembly of larger ones headed to destinations like Mars.





Artwork by: @nixonshead (AEB Digital on Twitter)

 

[e of pi]

Boldly Going Part 29

By 2010, congressionally approved programs were underway both to replace the space shuttle and to convert the existing Conestoga landing system into a fully reusable vehicle. At this point NASA began to turn its eyes skyward once again, toward the goal that had sat at the far end of program roadmaps for decades: Mars. The development of orbital servicing techniques and support technologies aboard Enterprise had provided extensive experience with the challenges of outfitting a Mars mission. Moreover, the station itself could serve as a platform for the construction and outfitting of a reusable transfer habitat for missions to the red planet. However, while Enterprise crews had spent nearly five years doing an excellent job of maintaining their orbital neighbors Galileo and Hubble, the conditions the job was undertaken in were rough compared to the dream of an orbital spacedock.

The payload bay of OV-101 Enterprise had been full, even on the original launch to orbit. The station’s airlock had been crammed at the aft end of the LLM, bare centimeters from the station’s Canadarm2 and the stowed Enterprise Power Module solar arrays. For twenty years, this cramped “back porch” had been the only location for operational EVAs staged from the station. While either of the station’s two Kelper lifeboats could act as contingency airlocks, doing so would reduce the orbital life of the capsules. Kepler wasn’t designed to operate for extended periods with the cabin in vacuum, nor was it equipped to recover cabin atmosphere during depressurization instead of venting it overboard, and so its use in any but the most dire emergency was discouraged in mission planning.

Similarly, while Enterprise was equipped with a number of robotic manipulator arms that could reach almost all areas of the station, viewing the results of their use was more challenging. Work on Hubble and Galileo was typically performed ‘in situ’, Galileo using its forward APAS port to dock and retrieve Hubble, then approaching the station to be berthed with its aft port to Node 2’s forward CBM. This configuration left both vehicles visible from both the Orbital Operations Center and the Cupola attached to Node 2’s port side, as well as close enough to OV-101’s airlock for the arm to ferry astronauts to the work site without a “walkoff” maneuver. Unfortunately, it also left any crew working on the telescope and miniature station precariously far from the station structure proper. Combined with worries of visiting vehicle thrusters impacting the sensitive telescope, mission rules dictated that work in this location was prohibited when Shuttle visits were scheduled.



These restrictions limited work schedules and often resulted in delays while teams waited for orbital sunrise. Moreover, delicate equipment and circuits were forced to be serviced with panels removed while on the most extreme end of the station, leaving them vulnerable to freak orbital debris and other risks. Furthermore, any tools or hardware that were lost off-structure were lost forever to the void, only to be tracked as debris. Over the life of the station, records indicated that the EVA toolboxes of Enterprise had gone through more than one complete replacement due to on-orbit losses. Worse, this was one of the few areas of the station in clear view from both the Orbital Operations Center and the Cupola. The Cupola could see down past OV-101’s radiators for some Earth imaging experiments and control of the arm near the portside truss and the Japanese Lab. The rest of the station, including all operations with the arm based on the Node 1 flight releasable grapple fixture, required that the control was carried out with the camera view from the arm alone. All of this was in direct contrast to the experiences outfitting the ET-007 LOX tank habitat, where work had been eased by direct access, full control of lighting and environment, and the divorcing of tasks on the worksite from visiting vehicles and proximity operations. To remedy these continuing issues, and to better equip Enterprise for it’s continuing mission as the home port to a growing fleet of spacecraft destined for missions orbital, cis-lunar, and beyond, there was a need for some kind of “space dock” or “hanger.” A new module for the purpose, launched via space shuttle or other vehicle, was extensively studied.


Image from: Centaur Operations at the Space Station: Cost and Transportation Analysis (1988)

The new build concepts for an orbital hangar ran into trouble immediately as they evolved from concepts and wishlists to attempts to craft budget requests. There was a limited supply of open berthing locations on the station where such a new module could be housed long-term, and worse a new design would have substantive development expenses. Instead, for one last time, Enterprise planners would turn their eyes back twenty years to adapt hardware on orbit since the station’s original launch on STS-37R in 1989. Ever since the ET-007 hydrogen tank was sealed against the vacuum of space by the crew of STS-38R, the tank had waited for its moment in the sun. Conversion of the cavernous (1500 m³) volume into laboratory, habitation, or commercial spaces had been repeatedly considered, but no need had yet justified the scope of the task. The outfitting work would require several times the labor taken in turning the original ET-007 LOX tank into habitation space. Moreover, the new volume added by converting the hydrogen tank to functional pressurized volume would dwarf the existing station but would be reliant on the old and more limited SpaceLab rack drawer standard instead of the newer, larger, and more capable International Standard Payload Racks. The new, larger racks were too big to fit through the 36” diameter manhole hatch which served as the entry point into either tank. Thus, the hydrogen tank had largely sat vacant, barring occasional use as a large, but sheltered space for the safe testing systems of EVA suits and procedures that were intended to work in near-vacuum without the risks of going off-structure. In other words, it already met most of the criteria for the desired hanger conversion.

By filling the sealed tank with nitrogen, welding operations and other systems installation (such as wiring for lighting grids and robotic arm mounts) could be carried out safely and conveniently, making use of the tank as a pressurized work environment right until it was cut open to space. After that point, however, the new hangar could never be sealed again, as NASA had judged it unlikely that astronauts working with tools in space would be able to cut a hangar door into the tank in such a way that any kind of trustworthy seal could be installed. The simplest conversion was to simply install all the desired support systems in the new hangar, permanently seal the manhole, and then cut the new hangar access panels from the outside. This would give an enclosed, well-lit space, by itself a massive improvement to the prevailing working conditions for servicing spacecraft at Enterprise.

NASA, however, was tempted to try for something a bit more ambitious. By evaluating which items on their wishlist for a Shuttle-deployed hangar could be incorporated into Enterprise’s improvised equivalent, program managers hoped to develop a capability in excess of the simple open workspace. Ideally, a hangar would have a redundant airlock, a pressurized path into any vehicles docked within it, and a robotics control station with a view of the work site to enable astronauts on EVA to better coordinate with robotics operators inside the pressurized zone. For the Shuttle-launched new-build hangar, the plan had been to launch a standard 4.27m (14 foot) module with a “cupola” of windows on its axial end as a “control booth” for robotics activities. The module would also either incorporate an airlock, or have one attached at a radial port. Docked to the station using another radial or axial port, the control module could also offer a docking port available for any craft housed within the bay. This single integrated module (or assembly of modules) would provide all the command and control functions for the new hangar, acting as the “control tower” for the work site.

If such a module were mounted into the new LH2 tank hangar, the conversion of ET-007 aboard Enterprise could be just as functional as the new-build alternative. Indeed, since the proposed Shuttle-launched alternatives tended to rely on tension-stabilized fabrics or plastic sheeting for the sidewalls of the hangar, the aluminum skin and spray-foam insulation of the converted ET-007 LH2 tank would actually be more robust and offer better radiation shielding than the new-build hangar. The 4.27m diameter of the proposed Hangar Control Module would fit into ET-007’s 8.4m diameter with room to spare. Even with its length, the volume remaining in the bay would still more than exceed the volume of a Space Shuttle cargo bay or standard 5-meter payload fairing.Thus, the bay could still host and service almost any payload a Space Shuttle or NSSL-class rocket could launch. The issue, of course, was that there was no docking port on the interior of the tank’s manhole. However, by this point, welding trials inside Enterprise’s hydrogen tank were old hat. Such welding experiments had been carried out on the station for more than a decade in one form or another, and their results were already being considered critical to install structural mounts for robotic arms, lighting grids, payload mounting trunions, and other fixtures if a hangar conversion went ahead. The engineers proposed simply shipping up a standard APAS docking ring in two sections, each small enough to pass through the 36” manhole, but designed to be joined to each other and the tank forward dome in space. By incorporating an inner hatch inside the newly installed ring, the structure could be proof tested without ever venting the bay to space, enabling astronauts to work on the task until it functioned properly. The installation of a docking port on a vehicle already in space would push the state of the art from mere servicing to actual fabrication. Checkout of the process could be carried out on the ground, with only a few permanent seals to be installed and joined on orbit. Testing of the procedure in the LH2 tanks associated with the Space Station Enterprise LOX Tank Outfitting Mockups in Houston showed the concept to be viable.

Within the cost-constrained environment of the lead up to the expected approval of a Mars program in coming years, NASA recognized that the hydrogen-tank hangar conversion, as jury-rigged as it was, was the best they were likely to get. Once again, time and money would dictate the expedient over the perfect for the expansion of Space Station Enterprise. The concept’s implementation was approved in 2011, with conversion in orbit planned to begin in 2015. Thus, the new hangar at Enterprise would be completed and tested well before any reusable Mars or lunar vehicle would depend on its capabilities.

Artwork by: @nixonshead (AEB Digital on Twitter)

 

[TimothyC]

Boldly Going Part 30

The conversion of Space Station Enterprise’s old liquid hydrogen tank into a hanger bay began in 2015, putting to use the largest remaining unconverted hardware from the original launch. When finished, only the three main engines which had lifted the station on their first and only flight would remain unmodified. The liquid oxygen tank had been converted into the station’s primary habitat section nearly two decades prior, and the mounts for the now-obsolete solid rocket boosters had been repurposed before the turn of the millennium to support the station’s massive integrated truss. These latest changes were complicated by a shift in the station’s operational functions. When the station had undergone the major changes between 1995 and 2001, the upgrades and modifications had been the primary task for the Enterprise crews. Once these tasks were finished however, the focus had changed to scientific return and upkeep, not expansion.

For a decade and a half, crews on-orbit and teams under the program’s banner at Johnson and Kennedy had worried about logistics, maintenance, or utilization and not the station’s long-passed time as a construction site. With a Kepler-E lifeboat at each end of the complex’s convoluted passageway geometry, crew sizes of up to sixteen were supported. Typically however, expeditions were limited to between eight and twelve members due to the number of sleep stations available. The additional lifeboat seats were left open to provide redundancy for visiting vehicles, and to ensure that there was always a seat close-by the crew no matter where on the station a problem might occur. These crews of around ten personnel were more than enough to take on scientific and engineering experiments, routine maintenance, and spacewalks in support of both the station’s science and maintenance, even as the systems aboard began to age.

By 2015 the patchwork interior of Enterprise drew comparisons to the interior of Mir from fifteen years prior. Portions of the station dated back to the original launch of STS-37R in 1989, even if they were long-overshadowed by newer installations. The original habitat section of the OV-101 middeck, home to the sleeping quarters and galley of the first permanent station crews, now mostly saw use of their hygiene facilities. The oldest toilet on station was the least preferred by the crew as it was the one most prone to issues, while being the one furthest from where replacement parts would be brought in. The sleep stations that hosted “Hoot” Gibson and the crews of Expeditions 1 through 4 were now used only by visiting crews, or for short-duration visitors staying between shuttle flights. Often these short-duration visitors were astronauts from international programs not fully affiliated with the station such as Brazil, UAE, and Australia, all of which sent astronauts to the station between 2000 and 2015. The station’s original laboratory, the SpaceLab derived Leonardo Laboratory Module had been slowly changed from research to storage over the intervening years. Only large, permanently fixed equipment such as the sample freezer and furnace remained in regular use as the ISPR equipped labs beat out the older LEOLab and its SpaceLab heritage rack-drawers. The Orbital Operations Center on the OV-101 flight deck was the most active portion of the original station, but even here small changes accumulated to profound differences. The Robotic Manipulator System control station had seen several generational upgrades, and IBM thinkpads on swing-arms covered many of the now-dark CRT monitors originally used to interface with the station’s five computers. The new laptops, as incongruous as their presence was, offered better and more responsive interfaces, as well as more display space than the original methods ever did.

As the station grew older, the crews and ground operators continuously monitored the orbital hardware for signs of structural or mechanical failures. [1] The oldest areas like the LLM and OV-101 came under particular scrutiny, but none received the religious attention reserved for the “hamster tubes.” These inflatable passages inside the ET-007 intertank, first deployed by the crew of STS-38R all those years ago, had originally been required as a part of pre-launch operations. The deployable structures had allowed ground crews access to the rest of the intertank during STS-37R launch prep, providing more commonality with conventional Shuttle launches than a fixed tunnel in the intertank would have yielded. With Enterprise conceived as a short-term gap-filler in response to the ultimately chimerical Soviet plans, the expedient was worth it. At times Enterprise planners cursed the ‘shortsighted’ decisions that left the orbital crews with only a few layers of beta cloth and three redundant bladers between them and vacuum instead of a proper metal hull. Protected by the thick, corrugated, aluminum of the intertank wall however, the skin of the expandable section had held up well for more than two decades. Still, every few years, the crew was required by mission rules to inspect the interior walls for any early signs of failure. The process was complex, requiring moving the layers of accumulated cargo stowage from along the interior walls of the tubes, then the netting that restrained said cargo. Behind that, crews could finally inspect the myriad of pipes and wires which passed through the nexus of the station, and peel back the fabric covering the actual deployable pressure bladders. Like any “spring cleaning,” clearing this area for inspection passes often turned up overlooked, long-retained stowage bags. Thus, crews often spent off-hours in the habitat wardroom over subsequent weeks sorting through the accumulated detritus of twenty-five years in space.

These “spring cleanings'' always found their share of odds and ends, sometimes including items dating to the earliest missions to the station. In 2014, the scheduled check turned up a harmonica originally included in a crew-preference kit aboard STS-39R, the first of the medium-duration “crew-tended” research stays aboard Enterprise. An inventory of the station’s collection of books and media taken while consolidating the onboard library revealed numerous objects of interest, including much of Terry Pratchett’s Discworld series and no fewer than four copies of 2001: A Space Odyssey. The mix of ex-military pilots and research scientists showed in the station’s media library. Not only did it include “nerdy” entries such as VHS tapes of both the original Star Wars Trilogy and DVDs of the Special Editions and Prequels, but also video recordings of every Army-Navy Football game between 1996 and 2006, except for Navy’s 2000 victory over the Army team. The interests of military pilots also showed in the collection including copies of Top Gun on both VHS and DVD--a film which had inspired more than one modern astronaut in their career decisions.

Similar “field days” were undertaken on the moon at Shackleton Base during the few times per year when the moon’s inclination put the “near” in the base’s near-eternal illumination. Though the station’s three aging TOPAZ II nuclear reactors still provided 10 kW continuously for basic operations of life support and other systems, more advanced science and rover operations still depended on a combination of solar panels and batteries to supplement the base’s power grid. The rare “dark weeks” when the local terrain cast long, dark shadows over even the tallest of the bases’ solar array towers were a chance to step down the base’s operational tempo and spend time on maintenance, inventory, and upkeep. With the insatiable demand for lunar sample return, the limitations on crew preference items brought to Shackleton had more to do with the capability to return them to Earth. Thus, even more than aboard Enterprise there was a steady accumulation of nicknacks and memorabilia as more than one base crew member decided they preferred their own personal sample return instead of a cassette tape, CD player, or book. Indeed, it was enough of an issue that one of the Habitanks in a disconnected landers had been dedicated as a “storage locker” for more than a decade of discarded surplus preference items, with the other Habitank of the same lander used for storing long-term contingency spares or refurbished hardware. With the selenogic program often taking crews on traverses away from the outpost for days or weeks, maintenance and scientific experiments a constant drumbeat of tasks when back at Shackleton, and just four sets of hands on the entire lunar surface, time to organize and sort such items was even more dear than aboard Enterprise.



These inspections and other regular maintenance tasks reflected the continuing realities of life aboard Enterprise and at the lunar base. When the LOX tank conversion had been accomplished by Enterprise Expeditions One through Six, the crew on station had little competition for their time and attention. As the process of converting the hydrogen tank into a hanger began, the opposite was now true. The extra demands on crew-time forced an increase in the size of station crews. Temporary sleep stations were rigged in the Kepler lifeboats, allowing a number of 14-person crews on station to provide the needed IVA time in the tank without cutting into the all-important scientific research. The additional hands were appreciated, as the process of converting the LH2 tank proved more challenging in practice than in theory or ground trials, much as had been seen with the original conversion of Enterprise into a station core or the outfitting of the ET-007 LOX tank into the station’s primary habitat.

[1] Author’s note: This section was written in mid-2020 before the leaks in the transfer compartment of Zvezda on ISS were noted as being of any import.

Artwork by: @norangepeel (Cass Gibson on Twitter)

 

[e of pi]

Boldly Going Part 31

Space Station Enterprise’s augmented crews began the work of assembling the new hangar bay fixtures inside the liquid hydrogen tank in 2015. Despite the benefits of working entirely in IVA, crews aboard Enterprise still found the process of welding fixtures to the tank walls in zero gravity challenging. While welding trials had been carried out experimentally, never before had welding been carried out in space on such a scale with intent to use the results. Mounting points for power and data cable runs were relatively simple to position with fixtures that mounted over the stringers and ring frames of the tank. A larger challenge came from the internal rail system which would allow a new miniature robotic arm inside the bay to function as a kind of “bridge crane,” similar to the Mobile Base Systems on the port and starboard trusses for CanadArm2. The waffle-grid pattern of stringers on the interior of the tank had been carefully machined for supporting the tank during launch. Now, the new rail mounts could take advantage of their tight tolerances to provide a pre-aligned base for the new system, but care still had to be taken as the crew members clamped the new mounts in place, aligned the rail, and welded it into final position. Over a year and a half, tasks were checked off the “to-do list” regularly, but there was always more to do.

By 2017, the rail and the mobile robotic arm base for the new “crane” had been installed and tested. Other preparations included installing similarly-precise payload mounting trunnions and stringing nearly a quarter mile of power and data cables. New flood lighting was added to illuminate the bay, and then nearly a quarter acre of fabric panels were added to line the bay, both to protect the wiring and to mitigate reflections from the original metal interior skin.[1] Finally, the rough preparations for cutting the new hangar’s door had been completed, minimizing work which would have to be carried out in vacuum. The hinge and actuator mechanisms for the doors were pre-installed and checked in shirtsleeve IVA, allowing the hinges to be “pre-aligned.” Once the marked section of the tank wall was cut, only minimal EVA work would be required to turn the remnant into a functional door though it would never work as a pressurized hatch. All that remained before the irreversible cutting of the bay door was the final installation of the new internal docking ring.

As anticipated, the ring’s installation and sealing proved troublesome. Several days of IVA work was spent on aligning the installation and tack welding the new ring components into place. From there, the secondary sealing gaskets could be tested, before being doubled up with the final welding of the two-piece docking ring into a single component welded in turn to the tank wall. Multiple attempts at this critical joining operation were required before the new internal docking ring was able to pass leak tests at the three times overpressure required by ground engineers and spaceborn astronauts alike. A leak in this area, so close to the station’s hamster tubes, could be insidious and tremendously risky. The crew of Enterprise were willing to do the job several times over if so required to ensure an issue never occurred. Because of the time required for its installation and the cost of an astronaut’s labor per hour on station, the new 300 kg docking structure was calculated as one of the most expensive construction operations in human history in terms of cost-per-kilogram. Eventually, though, the task was complete.

When the time came to cut open the 70-foot long “bomb bay” style door in the hangar’s 96-foot long sidewall, crews vacated the bay and left the task to a cutter attached to the station’s robotic arm. Cutting through the sidewall not only simplified the cuts compared to trying to cut off the end-dome of the tank, but also allowed a larger door for access to the bay and avoided interference with the “U”-shaped sump still in place in the LH₂ aft dome. This sump, and its associated plumbing and baffles, had drawn the hydrogen for Enterprise’s thirsty engines on their first and only climb to obit more than twenty years before, then had been plugged to seal the bay on STS-38R. The complexity of cleanly cutting the massive pipe was better avoided in NASA’s opinion. With the bay door cut and its edges cleared of burrs, the new hangar bay was open for business. The next Shuttle to arrive at the station carried up the new Hangar Control Module, the last major pressurized addition to the station to date. Installation in the confined hangar was eased by using the hangar’s own robotic crane arm for final alignment and installation. Once the module was attached and activated, Enterprise finally had a fully functional robotics control station with a view on the other side of the station than the OV-101 control deck as well as a fully redundant (and much improved) primary personnel airlock. The doors, for their part, functioned as expected. While they could not seal the bay, they were sufficient to close off paths into it for most debris and radiation. Perhaps even better, they were sufficient to prevent tools or equipment from being lost on EVA within the bay, the end to a long-standing problem.

When Galileo ferried Hubble to the station for their next overhauls in 2018, the benefits were demonstrated beyond argument. The repair scope for Hubble was particularly extensive: new solar arrays designed for repeated extension and retraction to fit in the new Enterprise hangar, two of the telescope’s gyroscopes replaced, the swapping of a star-tracker (never originally intended for replacement in orbit), as well as the replacement of one of the primary cameras with the latest in a series of progressively upgraded units. Even before the hangar’s introduction, Hubble servicing aboard Enterprise was preferred to servicing with Shuttle, as EVA tasks could be spread over more days without a return to Earth driving the schedule. In this case, however, the task list was accomplished with ten percent fewer EVA hours than predicted based on past Enterprise overhauls of Hubble. Astronauts ran hours ahead on every EVA thanks to improved coordination with robotics operators, consistent controlled lighting, and reduced time from the airlock to the worksite. With the overhaul of Hubble completed days early, the main challenge of the vehicle’s visit to station was a renewed debate between ESA astronauts and NASA crew if pulling Galileo into Enterprise’s hangar for inspection of its OMS engines rendered it a “shuttle” based from Enterprise’s hangar, instead of a free-flying station.[2]

In the meantime, the original Space Shuttle program had wound its way towards conclusion. The first-generation reusable vehicle which had spawned and nurtured Enterprise was due for replacement by a next-generation fleet of spacecraft. The new Shuttle-II and reusable Conestoga vehicles were hoped to operate surface-to-orbit and orbit-to-the-moon for a fraction of the cost. The remaining four original series orbiters, Atlantis, Columbia, Challenger, and Endeavour, had all done their part in shaping the history of space development. Their constant support carrying the flag of Space Station Enterprise to and from the launch pad for almost thirty years played no small part in the station’s success. However, with Shuttle-II on the horizon, the program was already looking to the next generation. As the finale of the original Space Shuttle neared, carrying the flag of supporting Space Station Enterprise and the next generation of lunar and Mars exploration would fall to Atlas III, Shuttle-C, and Shuttle-II...if the agency could navigate a critical series of technical and funding challenges.





Artwork by: @nixonshead (AEB Digital on Twitter)

[1] This fabric liner, on the vast interior surface of the tank-turned-hanger, had a number of features of note, including the Station’s name, a NASA Meatball, and in one area, tributes to the many seamstresses who had worked in aerospace ranging from Ida Holdgreve (about whom the Smithsonian Magazine has recently run an article - and she had an absolutely fascinating story) who worked for the Wright brothers, through those who had sewn the Apollo Lunar suits, to the teams that had made the liner itself.

[2] Stories of efforts to get an “OV-101 ⁄ 7 Galileo” decal on the side of the ESA vehicle are purely apocryphal.

 

[TimothyC]

Boldly Going Part 32

NASA’s success in preparing Enterprise to be the home for a new generation of reusable spacecraft came at a critical time for the agency. While the conversion of the station’s LH₂ tank into a spacedock was ongoing, NASA’s budget had been under increasing pressure at home. The agency was transitioning fully to a second generation of space access vehicles, both for surface-to-orbit and for orbit-to-moon. This next generation fleet was planned to combine the capabilities of the Space Shuttle with the increased operability and efficiency of the Shuttle-C propulsion modules for a new generation of spacecraft, as well as the ability to sustain the Minerva lunar outposts without the cost of expending a series of Habitank landers whose pressurized volume was no longer required. Unfortunately for those at NASA hoping for a rapid transition of focus from the moon and station to Mars, the cost of the new Shuttle-II orbiters and the reusable Conestoga’s modifications had blown many optimistic budget predictions out of the water.

NASA had initially hoped the heritage of the 200-Series Shuttle-C OPAMs and the Block II SSME might keep development to under $3 billion before the first test flight, and keep the cost for acquiring the full fleet of five vehicles under $5 billion. By the time the first flight article, OV-301 Independence was delivered for captive-carry testing in 2016, the program budget had already exploded to more than $6 billion for production and testing even with the rest of the fleet still in the early stages of construction. Though free from the operational challenges of hypersonic flight and high-pressure engines, the reusable derivative of the Conestoga lander had to wrestle with a longer logistical tail. Landers might have to return as far as Space Station Enterprise in low Earth orbit for full servicing. To minimize this frequency, primary systems like engines, propellant transfer equipment, and cargo loading gear had to be made robust enough for extended operations in vacuum, not merely for a single flight to the lunar surface. As a result, program costs had grown from the roughly $1.5 billion originally estimated to nearly $3 billion. The new variant’s development approached a quarter of the entire original Conestoga program cost from a clean sheet of paper to Minerva 2’s landing on the moon.

Such budget overruns on both of NASA’s next-generation vehicles inspired intense Congressional scrutiny. Senior NASA leadership were called to the Hill to justify the overruns in cost and schedule. In the meantime, Congressional focus on preserving the existing lunar program and second-generation reusability project at any cost had led to the ongoing postponement of any of NASA’s plans for Mars. NASA proposals had been floated to terminate the lunar base or even Space Station Enterprise as a way to free the funds...a notion which was dead on arrival in a Congress dominated by those whose constituents were paid for the continuing support of those programs. Even within NASA, the idea of sacrificing continuous station occupation, and once again losing the capability for ongoing lunar access after the hard fight to reacquire it, was deeply unpopular. Thus, only when the new lunar lander was in operation and Shuttle-II entered service for station support could NASA once again hope to turn its eyes towards Mars.

Without such a lofty goal in the near term, NASA’s 2017 operational tempo for Space Station Enterprise and the Minerva Lunar Outpost Armstrong (renamed in 2014 in honor of the late moonwalker) could fade into the background. To support fourteen astronauts on orbit and four on the lunar surface, five Space Shuttle launches and at least two Shuttle-C flights were needed every year. This routine made for a background hum of operations. Still, it was easy for those not paying close attention to lose track of Enterprise Expeditions, Armstrong crews, and the launches to support them. Finding capacity to develop and test Shuttle-II and its ground systems had to compete with a myriad of daily requirements, as operations crews were already stretched to keep up with their other demands. Volunteers willing to put in the additional overtime still stepped forward in large numbers to support the new flagship vehicles, drawn as they were by the lure of the first new large American rocket since Shuttle-C’s introduction in 1998.

The Shuttle-II program found as many complications to its introduction in the late 2010s as its predecessor’s introduction had 35 years earlier. Some issues like the original struggles with the SSME had been solved through extensive experience with Shuttle and with Shuttle-C’s engine pods, as the Block II SSME was now celebrating its second decade of operations. Rocketdyne was still producing or overhauling eight engines a year to support more than one hundred SSME flights, even as they prepared plans for a new Block III SSME which would incorporate a Russian-inspired channel-wall nozzle and main combustion chamber for improved life and reduced manufacturing expense. The program still brought new challenges for the propulsion team, primarily having to do with air-starting the Shuttle-II’s single SSME-69. A series of trials at Stennis during 2012 simulated starting the complex staged-combustion engine using only onboard systems, seeking to optimize startup transients and minimize the risk of a “hard-start”. The process required a complex combination of tank pressurization, pre-starting the lower-complexity RL-10 auxiliary/OMS engines to settle propellant, and closely controlled turbine spin ups to boot strap up to full power. The development program had to compete for test stand time not only against acceptance testing of engines for the operational fleet, but also for test engineer time due to development of the new vacuum-optimized RL-10 intended for the reusable Conestoga. This new engine, though on other test stands, was consumed with near-daily firings to work up to demonstrating the one-hundred-firing life required for orbital reuse without overhaul.

The mix of old and new continued elsewhere in the Shuttle-II vehicle. By using two of the existing liquid rocket boosters bolted together as a side-mounted first stage, Shuttle-II was the beneficiary of one of the best flight records in the history of rocketry. The venerable design had flown two each on more than 120 launches since its introduction on Shuttle-C and STS-116’s application of the liquid booster to conventional Shuttle flights in 1999. Its solid predecessor, though, had defied those who expected it to vanish after Shuttle stopped supporting it. With DoD funding, the solid boosters had made 110 Space Shuttle launches prior to STS-116, and then been used as the base for ATK’s Heimdall launch vehicle. The solid-based launcher was primarily a backup to the LRB-based Atlas III for larger payloads, given Atlas III’s higher performance and slightly lower cost. Still, Heimdall had achieved a respectable flight rate, as its single-stick configuration served as the primary replacement for the Delta II launch vehicle. Between the two National Security Space Launchers, Heimdall had flown first and launched more than seventy national institutional payloads over the previous twenty years [1]. However, winning the majority of the medium and nearly all heavy launches, Atlas III had added almost eighty missions to the LRB’s tally of successes. Thus, the statistical reliability of the LRB was drawn from a background of more than three hundred successful flights. Given that Shuttle-II had only minor modifications to the thrust attachments, NASA was confident in the success of the new vehicle’s first stage.

Novelties in Boeing-Rockwell’s new orbiter design more than made up for the simpler task facing Lockheed Martin’s first stage development team. For the first time, a reusable rocket would have to incorporate significant cryogenic propellant storage into the primary structure. Both Shuttle LRBs and Shuttle-C’s propulsion modules kept their hydrogen and oxygen propellants in tanks which were (with one notable exception aboard STS-37R) disposed of without a thought. The Soviet Buran shuttle’s kerolox orbital maneuvering tanks were both warmer and smaller in mass and volume than the Shuttle-II’s internal second stage hydrogen tanks. For a service life of dozens of missions, Shuttle-II’s composite propellant tanks would have to survive hundreds of cycles being filled and drained of hard cryogens for nominal missions and aborts, then face the heat of entry repeatedly on the other side of the same structures. Even before their integration into a vehicle, the first set of prototype tanks were put through near-daily proof tests throughout 2013 to qualify their ability to survive cryogenic temperatures and pressures without leaks or damage even after dozens or hundreds of cycles.

The thermal protection system required to keep the heat of entry out of the orbiter’s propellant tanks and major structures also brought new twists on a familiar problem. Thanks to a reduced ballistic coefficient on entry caused by a smaller maximum payload and overall lighter structures, Shuttle-II would encounter a less challenging heat pulse during return to Earth. However, NASA was aiming for reduced hand-labor to turn around their next-generation vehicle, and continued to worry about the risk of tile damage, even thirty years after the loss of Discovery. Thus, NASA had specified that Shuttle-II would use improved ceramic-impregnated thermal blankets to replace the fragile and labor-intensive tiles on even more areas of the vehicle. For the belly and other critical surfaces where the blankets could not be applied, NASA studied new metal-honeycomb sandwich tiles.

With inner and outer refractory skins separated by metal honeycomb voids, the new tiles combined some of the concepts of the “hot-structure” X-15 and X-20 with the piecemeal replaceability and traditional aluminum primary structure of the existing Space Shuttle orbiters. The new metal tiles were more impact and weather-resistant than the fragile ceramic tiles, and the use of mechanical fasteners instead of adhesives made them easier to install and service. Still, it was a radical change and was identified as a key risk. The metal tiles received extensive testing in arcjet wind tunnels even as the first orbiters were beginning to undergo structural assembly in 2013 and 2014. In the meantime, other engineers at NASA prepared contingency plans to cover the new orbiters’ bellies in the same ceramic thermal protection tiles which shielded the original Space Shuttle and the 200-series Shuttle-C OPAMs.

Interfacing with the existing Space Station Enterprise logistics pipeline was critical to the success of the new orbiters. When flying without crew, Shuttle-II would be equipped with a small Docking Module in the forward part of the bay. The small pressurized vestibule would connect to the station with an APAS port and provide a space to connect power, data, and fluids plumbing to Enterprise, Galileo, the reusable Conestoga landers now called the Diana series, and the Mars spacecraft NASA was beginning to study in rough concept. The rest of the bay offered similar payload interfaces to the first-generation Shuttle, enabling the new orbiters to continue to carry existing payloads like MPLMs, Spacelab pressurized and unpressurized pallets, the commercial Spacehab modules, and Canadarm. With the reduced overall length, the pallets used for carrying cryogenic propellants for Galileo and hypergolic propellants for Enterprise’s orbiter-vintage OMS pods would have to be modified, as would procedures for Kepler lifeboat exchange. However, the biggest new challenge was the crown jewel of Shuttle-II’s capabilities: its crew module.

Shuttle-II’s ability to carry crew was distinctly unlike its predecessor. Instead of being integral to the structure, the crew module was a detachable pod, almost a spacecraft unto itself. It would fill the entire flight when used, but could be left home when not needed. By using the entirety of Shuttle-II’s new bay length and 14-ton payload mass for crew support, the Shuttle-II crew pod would actually be more capable than the existing Shuttle. With the lower deck of the MPLM-sized module used for consumables storage and the new Shuttle’s toilet, hygiene facilities, and life support systems, the crew module could carry a total of eight people for a week on independent flights. Trading onboard consumables with additional seating on the upper deck would allow the pod to transfer as many as 14 astronauts to an existing spacecraft or station. This configuration, anticipated as the primary flight mode, would allow rotation of an entire Enterprise expedition on a single flight or a half-expedition with several short-stay “surge” astronauts from international partners. In a “high density” configuration for future stations, NASA and Rockwell even considered replacing all lower-deck facilities other than the toilet with additional seating to boost capability to 22 aboard. This would more than double the record for the existing vehicle, though endurance in such a configuration would be limited and best suited to fast rendezvous or evacuation roles.

Though the orbiter was capable of extensive automatic operations and would normally be expected to land itself without human intervention, the astronaut office was uncomfortable with any vehicle where crew aboard were entirely unable to “put a hand on the stick.” Thus, the crew pod’s commander and pilot sat in a “simulator”-style setup in the front of the compartment, able to see outside through cameras and numerous “glass cockpit” displays. Their only direct view outside the crew module would come through a pair of upward-facing windows for operations using the module’s integrated retractable docking port. There, they would have complete ability to override the computer systems through all phases of flight from launch initiation to wheel-stop on the runway, including over the powerful abort motors mounted fore and aft of the pressure compartment designed to blast the pod and crew safely free of any issues on launch abort or return to Earth.

The biggest loss with the new crew pod was its lack of a dedicated airlock. Though the docking port of the crew module could be used as an improvised airlock, the APAS port’s interior dimensions were difficult to navigate in practice while wearing a suit. This reduced capability reflected the broader limits of the new Shuttle-II: it was a true shuttle to the stations and spacecraft it would serve. Thus, it lacked the “jack of all trades” abilities of its predecessor, and with that came losing capabilities like combining cargo with crew for servicing space probes or other craft as it launched them. However, the plethora of pallets designed for the new orbiter showed this wasn’t a drawback, but a natural result of specialization building on the lessons of the past in pursuit of the optimal next-generation spacecraft.

The transition from the original Space Shuttle fleet to the new Shuttle-II came on the heels of an extended series of ground-side systems testing. Test articles were prepared not only for secondary pallets and the crew pod, but of the airframe itself. The first qualification tanks were assembled with structural test articles for the wings and fuselage to produce OV-300. This vehicle was intended only to fly in atmosphere for captive carry and glide tests to demonstrate basic autonomous and crew-commanded return to a runway, much as OV-101 Enterprise had done for the original Shuttle. Thus, only aerodynamic replicas of the RS-25 main engines and the RL-10 secondary propulsion were fitted. Still, Enterprise herself proved it was possible to underestimate such early production vehicles. Reflecting this, when OV-300 was rolled out of Palmdale in 2016 and ceremonially named Spirit, a plaque was affixed to the forward end of the payload bay marking “spacewalkers: cut here for hydrogen tank access”.

For the moment, OV-300 was atmosphere-bound for testing, like its OV-101 and OV-200 antecedents. Still, with Mars plans becoming more openly discussed as the next logical step, no one was willing to write off any possibilities. The first flight-weight orbiter, OV-301 Independence, began propulsion testing at Stennis in late 2017. Barely a month later, OV-300 completed the first crewed captive carry test on the back of the 747 Shuttle Carrier Aircraft. By the time the series of more than a dozen captive carry and glide flights were completed in 2018, OV-301 was being delivered to Florida for the new system’s maiden launch with the confidence that it would be able to land after its first flight.




Artwork by: @nixonshead (AEB Digtial on Twitter)

[1] Institutional payloads are those launched for US Government agencies such as NASA, NOAA, and others, as well as those launched in support of national security missions.

 

[e of pi]

Boldly Going Part 33

Despite the success of Spirit in the captive carry and glide tests, ground testing of the Shuttle-II’s systems could only go so far. Many of the critical capabilities of the orbiter could only be tested inflight, during ascent or orbital operations. The first Shuttle-II orbital flights would themselves be demonstrators, each adding incremental capabilities from orbit to landing to operations with Enterprise. Unlike the original Shuttle, which had flown crewed on its first orbital flight and Shuttle-C, which had flown with crew on merely its second flight, Shuttle-II could perform the majority of its major roles with no crew aboard. Thus, NASA planned a series of five missions to prove the vehicle safe by transporting logistical supplies like MPLMs and Kepler lifeboats before any lives would be risked.

Much like with the introduction of Shuttle-C in the late-90s, NASA allocated a block of consecutive mission numbers to the sequence of demonstration flights, reserving them for use even as the primary Shuttle and Shuttle-C manifest varied from year to year. Shuttle-C’s test flight designation block, including the missions supporting Minerva 2’s return to the moon, was assigned bracketing the coveted STS-100 milestone. Given the prodigious flight rate of the late 1990s and early 2000s and orbital support since, the Space Transportation System was already assigning mission numbers around STS-270 by the time Shuttle-II’s debut mission numbers were reserved. With an eye on public relations, the equally coveted STS-275 through STS-280 were reserved for Shuttle-II’s demonstration flights [1].

Spirit’s captive carry and glide flights and Independence’s propulsion testing at Stennis were the most visible aspects of the preparations for Shuttle-II’s debut on STS-275. However, before STS-275 could fly, the Cape required extensive logistical efforts to prepare to process the new vehicle and the two existing STS vehicles in parallel. With the transition from SRBs to LRBs, processing flows for normal Space Shuttle operations and even the dual-launch Minerva lunar cargo flights were significantly smoother than they had been during the turn-of-the-millenium peak. Even though the number of launches remained relatively similar, the elimination of nearly 20 days of SRB stacking time (and resulting exclusion of work in adjacent High Bays) meant High Bay 3 was now surplus to requirements for regular stacking. Though it needed to be retained for a “safe-haven” in the event of extreme weather, the processing platforms in the high bay could be dismantled. The platforms were then reconfigured to support stacking Shuttle-II’s twin-LRB first stage, mating Shuttle-II itself, and checking out the assembled combination for flight. Mobile Launch Platform 3, originally built for Saturn V, would now be modified to support another vehicle. The base of the platform had only minor changes as the LRBs for Shuttle-II would retain their distance and positioning relative to each other as on the original Shuttle, and Shuttle-C stacks. The air-started nature of the Shuttle-II main engine also meant that there was no need for a new flame trench for the new vehicle. With just minor modification of the existing service masts and new connections from the LC-39 fixed service structures, all four MLPs could eventually be used with the original orbiters, the well established OPAMs, or the new Shuttle-IIs. LC-39B was the first of the pads to receive modifications to the Fixed and Rotating Service Structures to support the revised vehicle interfaces. In March 2019, the new facilities were activated, and the stacking of Indepence for her first flight began.

In May 2019, STS-275 made the Shuttle-II’s first trip to the pad. The stack’s appearance was starkly different than any which had come down the crawlerway before. The twin boosters and orbiter hanging between them made for a profile unlike the slightly off-balance Shuttle and Shuttle-C. Though similar to the previous generation orbiter in overall dimensions, Shuttle-II was lighter and sleeker, tucked between its two powerful LRBs. With a lower dry mass thanks to tank-reinforced primary structures, Shuttle-II could make due with smaller wings, which were mounted slightly forward of the fully-aft position on the original shuttle. The nose was a smooth ogive, its analytically calculated aerodynamics unbroken by the need for crew windows. The climb off the pad on the nearly-invisible blue flames of an all-hydrogen stack was picture perfect. Captured by numerous photographers, it looked like something out of science fiction.

The break from routine helped draw attention to NASA’s launch operations. With extensive promotion during preparations for launch, audiences in person and online were nearly 30% larger than the typical Space Shuttle mission. For the next three days, Independence stretched her wings on orbit, demonstrating basic systems function and vehicle integrity, while onboard cameras recorded the results. However, after launch, the audience for mission updates rapidly shrank. A robotic space plane with no crew might be safer, but general public interest was ephemeral without crew aboard. Though NASA proudly promoted Independence as the first full-sized cargo spaceplane to land itself uncrewed since the sole Buran landing in 1988, the audience for landing was actually slightly smaller than that of a typical Shuttle return. Independence returned for the program’s second flight, STS-276, in November of 2019. This time, Shuttle-II would go to Space Station Enterprise, like the two conventional Shuttle missions (STS-289 and STS-287) which had launched in the meantime. With the orbiter headed to the station, the viewing audience and news coverage held steadier after launch. During tests in years past, the mini-station Galileo and the related Automated Transfer Vehicles had flown with versions of the Shuttle-II avionics in the loop, providing parallel control tests for the new vehicle’s Shuttle-heritage docking radar under automatic control. Still, STS-276 was the first time the massive bird itself had made the trip to NASA’s most storied outpost. The gawky delta-winged orbiter was more awkward to maneuver than the simpler cylindrical Galileo, and elaborate tests were carried out to prove it was under control during the approach.



Independence made multiple approaches to the station, pausing several times in each to check that guidance remained on target. The pauses also allowed time to ensure that the massive drone spaceplane responded to abort commands from a control panel in Enterprise’s operations center, where much of the crew had gathered to oversee events. The hold points moved steadily closer, with Independence flying formation with Enterprise first at two kilometers, then at two hundred meters, and finally at twenty meters. For the crew aboard Enterprise, the giant new orbiter felt almost close enough to touch. Finally, after hours of testing, Independence’s docking ring slid home at the axial port on the bottom of Node 1.

Shuttle-II had proved it could reach the station, now it remained to be proved that it could service it, a task which fell in 2020 to the next pair of flights. The cargo bay of the new Shuttle-II orbiters was smaller than their predecessors, and made smaller still by the cramped docking module all uncrewed missions to Enterprise would have to carry. Still, the remaining space would be large enough for either of the two most critical payloads: the ESA Kepler lifeboats and the Multi-Purpose Logistics Modules. The second Shuttle-II orbiter, Freedom made her debut on STS-277 in March. The new orbiter carried a Kepler lifeboat in its cargo bay. Following procedures which had been developed over the years, Kepler no longer had to fly itself free of an arriving orbiter or make an independent rendezvous with the shuttle after departing station. Instead, by 1997 procedures had improved to use the station’s arm to pull the lifeboats out of a visiting orbiter’s bay and berth them to one of the station’s APAS ports. Not only did this save wear-and-tear and mision complexity, it ensured the ability to put Kepler lifeboats on APAS ports which were more difficult to access when approaching the station on independent flights. Once STS-277 docked as Independence had on STS-276, Freedom deployed its robotic arm under station and ground control and traded the Kepler lifeboat in its bay for one of the two which had stayed on station for the last six months. When it returned, Freedom proved that Shuttle-II would have the same operational effectiveness which had already allowed the same set of four reusable Kepler-E lifeboats to support more than 50 rotations since 1995 with only minor refits and routine maintenance.

On STS-278 in August 2020, NASA tasked Independence with a mission to demonstrate the other major support required for Space Station Enterprise, by flying the legacy Multi-Purpose Logistics Module Donatello. Though less exciting than the Kepler lifeboats or new modules flown to station, the stumpy can-shaped modules made up the backbone of the Enterprise logistics pipeline. Like dozens of flights before it, STS-278 saw Independence “carrying the mail” with tons of food, clothing, and routine scientific samples. With the module handed off to the station’s waiting arms, Shuttle-II proved it was ready to take on the challenges of supporting Enterprise’s ongoing mission in orbit from the four remaining original Space Shuttles. The full support of all Enterprise operations was demonstrated by a final mission, STS-279, which saw Independence fly to station once more, this time with a fluid cargo and gas transfer transfer pallet in her bay. Though high-pressure nitrogen and oxygen tanks could simply be carried in the bay, transfer of hypergolic propellants for Enterprise and cryogenic oxygen and ethanol for the associated fleet of orbital vehicles was more complex.

On the previous-generation Space Shuttle, launching cryogenic oxygen to Enterprise had required carrying a pallet of tanks inside the payload bay, tied into connections originally used for the Shuttle-Centaur “Death Star’ launches before the loss of Discovery. For Shuttle-II, the process could be simplified by using cryogenic oxygen already stored for the orbiter’s own hydrogen/oxygen Orbital Maneuvering System on every mission. Plumbing to allow connecting to these supplies in flight had been designed into the new orbiter, and no new pad hookups were required. Thus, the only fluid and gas pallets needed for STS-279 and subsequent resupply flights were compressed nitrogen tanks and the tanks for room-temperature-storable hypergolic propellants and ethanol fuel, which could be filled prior to cargo bay close-out and left in-situ even during extended on-pad holds. Still, carrying fluids in the bay always raised the specter of leak concerns. During preparations for STS-279, there was an abundance of caution with the new fluids pallet and (ultimately spurious) warnings of leaks led to multiple aborts and scrubs. Eventually, NASA stood down the launch preparations for multiple days. Technicians reopened the orbiter’s payload bay to replace valve seals between the tank interconnects and the docking module. Finally, Shuttle-II knifed into the sky on a mission to top off the thirsty tanks of Space Station Enterprise and all its associated vehicles. With two orbiters active and five successful flights under their belt, NASA’s Shuttle-II program managers began 2021 ready for the final challenge: crew.



The NASA Public Affairs Office had big plans for STS-280. After a minor refit to incorporate early lessons from the first several flights, OV-302 Freedom was tapped to carry the new crew module to Space Station Enterprise in February of 2021. To reduce risk, only the bare minimum crew would be aboard. Doug Hurley would be the spacecraft commander, while Bob Behnken would be the pilot. In order to ensure there were options for the crew’s safe return if problems with the new orbiter were encountered that made safe landing questionable, NASA arranged to have the previous shuttle mission, flown by Endeavour, held at Enterprise with spare seats to give Hurley and Behnken a backup ride home. For Public Affairs, this was a perfect opportunity. They begged Flight Operations to arrange for a fly-around of the station, conducted by a JAXA HTV which was held at station for a week past the original scheduled departure, to enable the remote camera systems aboard to capture the sight of three Shuttles on orbit together at the same time: the first orbiter (OV-101 Enterprise), the last of the first production run of orbiters (OV-105 Endeavour), and the first of the next generation of NASA crew spacecraft (OV-302 Freedom). With the Enterprise Power Module solar arrays temporarily locked horizontally, Endeavour was docked to the APAS adapter on Node 2’s zenith port, leaving the two sisters nearly touching with Endeavour docked at the Node extending up from the old Leonardo Laboratory module in Enterprise’s payload bay. This left the more easily accessible Node 1 nadir port open for Freedom. The resulting image of three sisters and the massive orbital complex they had spawned proved a spectacular capstone to the trouble-free debut of the new crew module. With data in hand from the first six orbital missions, NASA proudly certified the new Shuttle-II ready for regular service in June of 2021. At the same press conference, they also publicly confirmed the official hand-off between the two generations of shuttle. Though existing missions planned for the original orbiters were to be flown out, any new missions would be planned or transferred to the new Shuttle-II. As a block of mission numbers was reserved for the first flights of Shuttle-II, so too was a block reserved for the last flights of the original orbiters. Thus, the final flight of the original series of space shuttles would be assigned to OV-104 Atlantis in late 2022 on STS-300.








With the final flights of the original space shuttle orbiters, and the handover of orbital support to the new Shuttle-II fleet, Enterprise is now the single longest continuing element in American and International crewed space infrastructure. Its capability to support massive and sustained human occupation in space, not to mention its tremendous scientific capability, more than justifies its continued center-stage position in the realm of human spaceflight. Enterprise’s STS-37R legacy occasionally presents weaknesses, like the narrow intertank “hamster tube” passages which frustrate distributing ISPR-enabled logistics and experiments around the periphery of the pressurized components on the station. Still, the station’s new hangar, and servicing capability it provides, is the center of Enterprise’s support of the President’s renewed initiatives for space exploration. With the ability to service the new reusable Diana variant of the Conestoga lunar landers, the ramp-up of the Shackleton Crater lunar outpost from “Long Duration Stay” to “Permanently Crewed” status will provide work on orbit for many years to come. Within the next decade, the shuttle-turned-station may face an even greater challenge with on-orbit assembly and testing of the Hōkū'ula Mars Transfer Vehicle if Congress upholds the President’s budget requests.

While her sisters eventually fulfilled their role as “space trucks” for the development of space infrastructure, OV-101 Enterprise has transcended her roots in every way by becoming infrastructure. Once a ground-bound reject from the program’s early days, Enterprise rose to the challenge when the lack of an American space station became a critical national deficit. Over decades of operation, her status as an ad-hoc expedient has turned into serving as a keystone for the ongoing development of humankind’s reach into the stellar frontier. In-space outfitting and servicing techniques developed for her construction and expansion were a testing-ground for techniques like Habitank conversion and reusability of in-space assets like Galileo and Conestoga. Her launch aboard STS-37R proved to be the pathfinder for the LRB-powered Shuttle-C, and she remains the most important destination in space for the new Shuttle-II fleet. The central role of Space Station Enterprise in orbital science, American commercial research, and lunar & martian mission planning ensures Enterprise will retain a role supporting missions no one has dreamt of before for years and possibly decades to come. As long as that continues, the program’s motto for the last forty years will remain true: “First to Fly, Last to Land.”




Authors’ Note: I swear, we forgot about the shuttle names in Armageddon until after we had these names picked.

[1] Here is the math we worked through. STS-131 closed out CY2001 ITTL. There were then nine flights each year in 2002 and 2003 to finish building out Space Station Enterprise. Given this total (149 flights at the end of 2003), we looked forward over the next nearly two decades. There would be four or five conventional shuttle flights per year (covering lifeboat rotation and logistics, as well as occasional show-the-flag flights to MIR-II). Furthermore, there are at least two Shuttle-C launches each year to deliver crew to the moon, and there are, in the 2004-2017 period, another nine or so cargo flights, each needing two launches for site establishment and base buildout. With a few additional flights sprinkled in for the DoD and JPL, we came to the conclusion that there would be on average about NINE STS-numbered launches per year. Added to the above total, and when NASA manifests the Shuttle-II test flights in 2016, the first batch available that is near a nice round number starts on STS-275. With the lunar base moving into operations and sustainment instead of expansion, the 2018-2022 period sees a slightly lower number of flights (averaging about eight per year), which is why STS-300 is selected as the number for the last original orbiter flight.


Render by:@nixonshead (AEB Digital on Twitter)
Patch by: Disco Slelge

 

[e of pi]

e of pi’s notes:​

Happy April Fool’s everyone! So...this project started about a year and a half ago, as an idea of a quick-and-dirty timeline to explore what would have to happen to see an orbiter-derived station, primarily drawn from the Ware & Culbertson studies, actually realized. The idea was to do it for the April Fools 2020 post, with three main goals: little additional research so I could do it as a solo project, no new art, and about 5,000-7,000 words. So, more than a year later, let’s take stock: Thanks go to @TimothyC for his help with the additional research and concept development which came about in figuring out the details as this story grew in the telling, and in the process of whipping words into shape to describe this monster of a space station. Thanks go to the entire art team for their work realizing the station and lunar outposts of this timeline. And, more than 68,000 words into a 5,000 word project, thanks to everyone who’s been reading, thinking about, and commenting on this timeline for the past three months.

Ultimately, as TJ and I developed the idea, the issue became simple: this idea was too interesting to deny going into details that emerged as we thought about it. There’s more that could have been told, from how Shuttle-C launched ET-derived Mars vehicles might be built to the future of post-Enterprise stations, or how commercial fares in a timeline where NASA has robust and frequent access relatively cost-effectively from their own stable of launch vehicles, but those felt tertiary at best to Enterprise’s already-overlong story. We have some more thoughts to share, some of which were background notes that didn’t end up coming in the main TL, some of which are semi-canon and semi-contradictory thoughts about the TL’s future after the end, and we’ll be sharing that over the next few weeks and months.

In the meantime, once again, Happy April Fools, and I hope you enjoyed this--the greatest joke in it was the idea this was a story that could be told any shorter.

 

[TimothyC]

TJ's notes:​

First, I would like to thank e of pi for allowing me to join him on this wonderful project. It’s been an adventure more than a year in the making. I’d also like to thank Usili for getting his hands on an early copy of After LM before the pandemic was in full swing, and cluing us in to the “HabiTank” concept that became integral to the lunar program we outlined.

I’d like to thank AEB Digital (nixonshead), Dylan Semrau, Cass Gibson (norangepeal), & Discoslelge for all of the amazing artwork that they have done for us in support of this timeline, and I hope they are remembered when next year’s Turtledove Awards for artwork are up for nomination.

As for the timeline, this started out in the planning stages as a short (ten thousand words or less) project for April Fool’s Day 2020. It uhm, grew out of control, and by mid-February 2020 it was obvious that we needed something smaller to fit into the schedule, which was the nucleus of The Last of the Clippers.


Once freed from the early short writing period, the story was allowed to expand to the final form which is long enough to qualify for more long-form literary awards rather than the shorter novella category (final draft word-count was over sixty-seven thousand words for the story and image annex posts).

While the main story of the timeline is finished, There are some ancillary materials that are not yet in a form ready for public consumption, so look for those in the coming months.

Sincerely,

Timothy ‘Arnie Holmes’ Cizadlo

 

[TimothyC]

Authors’ Notes​

A Discussion on names:​

When writing Boldly Going, we were confronted with the need to give names to the wide variety of vehicles that we had introduced, including the Shuttle-C OPAMs, Kepler capsules, Lunar Landers, European ATV derived modules, and finally the Shuttle-IIs.

Working backwards, the Shuttle-II names remained in flux for quite a while, with the names being finalized only sometime in late December of 2020, resulting in the inadvertent reuse of the names from the movie Armageddon (The intent being a joke that you end up with the orbiter Freedom docking to the Space Station Enterprise.) While we only named three of the 300 series orbiters, using Freedom and Independence as the first two operational units and Spirit as the test article leads to the idea that they are broadly referred to as the Spirit-Class Orbiters. Our thought is that the names selected for the first run of 4-5 operational vehicles would be names that fit with the scheme “Spirit of _”, and will probably seem like the historical names of Mars landers and helicopters. Indeed, part of the reason for the late December switch was that Ingenuity had been grabbed from the list of Mars 2020/Perseverance alternatives earlier in the year, and then we had to switch it to something else when it was selected in turn by JPL for the real helicopter. Additional orbiters beyond these may revert to more conventional names based on ships of exploration, but once again, that’s beyond the scope of the timeline. A potential bridge, though not one we’re canonizing, would be an OV-30X “Spirit of” Discovery as it both fits the name scheme and would serve to honor TTL’s only lost orbiter.

One of the unmentioned bits that was worked out is that because the Spirit Class Orbiters would not have the exact same mounting hardware as the original orbiters, the older NASA Shuttle Carrier Aircraft (SCA) - N905NA and N911NA would not have the correct mounting points for the new vehicles. NASA uses this to justify the purchase of two new, 747-8F derived transports, which would be designated N976NA and N977NA. In keeping with the numbering and the “Spirit-class” naming scheme, these aircraft would be known as The Spirit of ‘76 and The Spirit of ‘77 respectively. The first is obviously named after the American Revolution, and the second after the Enterprise Approach and Landing tests. The numbers are a happy coincidence, mostly selected to fit with the NASA aircraft registration scheme. Most FAA registered NASA aircraft use a three digit number with the NA suffix, with the first number designating the Center the aircraft are based out of, with 9 being the number for Johnson (4 is Wallops; 5 is Langley; 6 Lewis/Glenn; 7 is Ames; 8 is Dryden/Armstrong). After some digging, I (TimothyC) determined that N976NA and N977NA were both going to be available in the 2005-2020 time period. This will also allow NASA to retire the older 747-100(SR), and pipe the new aircraft for in-flight refueling from tankers during their construction, improving the national and international reach of Shuttle-II transport. These new SCAs are expected to have a long and productive life.

Moving on to the ATV derivatives, as was noted by @Polish Eagle, the Galileo Tug / Crew-Tended Free-Flyer / Station was named entirely as a play on the name of the shuttle-craft from Star Trek. We’re glad to see that someone spotted it. Curie was picked for the module on MIR-II because of that station’s greater focus on microgravity physics thanks to the ability of experiments to be placed closer to the station’s center of mass - rather than the labs on Space Station Enterprise which tend to be located on the station’s edges, far from the best environment for microgravity research. The ATV resupply vehicles themselves are left unnamed, as there would have been close to thirty of the vehicles (one per year to Enterprise and one every other year to MIR-II) over the course of the timeline.

One name that was not available was Leonardo, which was a late change to the name of the laboratory inside the Enterprise payload bay, which in early drafts was called the “Enterprise European Laboratory Module” or EELM. That got to be a mouthful, and confusing when the Columbus module would be launched later. The resulting wordplay of using LEOnardo with Low Earth Orbit was too much for us to pass up.

The names for the Kepler capsules were, like the ATV derivatives, selected from the names of various European figures. The selection of the class name was made fairly early on, as it was a name that was neither French, nor British, nor Italian, making it acceptable (if not preferred) to those nations that were paying for the design, had conceived of the design, and had sold the design to the rest of ESA. Once we confirmed that we would be naming the capsules after people, the name for the first lunar-capable capsule almost had to be the Jules Verne, although there was some minor debate as to that being the first lunar-capable capsule, or the first capsule to go to the moon. In the end, it was slotted in as the first lunar capable vessel. The names that we ended up defining with certainty were Johannes Kepler, Charles Messier, Edoardo Amaldi, Jules Verne, & Francesco Grimaldi. The first three were three of the four Kepler-E lifeboats that are cycled through year-long tours on Space Station Enterprise, and the later two are two of the Lunar-capable capsules. Further names were never selected, but the name Issac Newton was likely used for one of the lunar-capable units.

The lander program naming selection of Minerva has been gone over before, and we went over the selection of the name Conestoga in the text in Part 20.

OPAM naming ended up being a bit fabulous in its subtlety. e of pi expressed a desire to name the first two American reusable heavy lift vehicles after two titans of American myth even before we started working on Boldly Going. Thus, when the naming opportunity presented itself, the names Paul Bunyan and John Henry were immediately used. As the timeline progressed, we needed to have additional names. In the process of discussing it, we discovered we had accidentally implied a naming scheme (at least on the meta level), and thus first had George Washington and Richard Byrd penciled in to complete the set. Later on, TimothyC suggested that to avoid confusion with other nationally significant named craft (read: USS George Washington CVN-73) we instead name OV-203 and 204 the George Meuller and Richard Nixon respectively - for their contributions to the shuttle program. The first was met with acceptance. The second was met with the suggestion being ignored - repeatedly. The idea is that the names of the OPAMs start out as unofficial, but since the public reacts better to craft with names than those with just serial numbers, they become official as the OPAMs fly more. The Richard Byrd is the craft that performs most of the Defense Department missions, and I am sure that the Intelligence Community loves the twenty-five foot wide payload fairing that Shuttle-C offers (five meter fairings allow for deployable antennas that are hundreds of meters wide and Shuttle-C is over half again as wide).

OV-105 Endeavour received the same name it did historically, because even with an American space station in service, we did not see a reason why the name would change. We would encourage people to read From Ship to Shuttle: NASA Orbiter Naming Program, September 1988 - May 1989 for a better understanding of how the name was selected.