Boldly Going Part 14
After all the debate, the plan for NASA as approved in 1991 was, quite simply, right down the middle. As expected, “Option B” was selected for expansion of Space Station Enterprise. ESA and NASDA each signed a memorandum of understanding with NASA to formalize their participation later that year. ESA would provide their MRRC as a crew lifeboat and alternate crew access vehicle in exchange for launch of a laboratory module and crew slots aboard station, while Japan would provide the hulls for the two node modules in exchange for the launch of their own lab and crew. After a delay of nearly 2 years, Bush finally saw Space Station Enterprise’s expansion back on track. However, the biggest headline was the formal blessing of NASA’s new lunar ambitions. The new program, formalized as the “Minerva Program,” was approved and budgeted for full design studies and development. The project would follow roughly along the lines of NASA’s baseline Option D Design Reference Mission, and the new program office began issuing contracts almost as soon as it came into formal existence. Marshall would coordinate the development of the Shuttle-C cargo launch vehicle, building on Enterprise experience, while Johnson would coordinate the human landing system. Other centers like JPL, Lewis, and Ames would develop surface hardware and robotic precursor missions. Much like Reagan’s goal to launch Enterprise “before my term is up,” the goal of launching the first Minerva crew to the moon within the decade was unofficial, but widely understood to lurk behind a planning date which settled neatly into 1998.
Development of the Shuttle-C vehicle was anticipated to be the simplest aspect of the program, given the recent launch of Enterprise as a “cargo launch vehicle” pathfinder. However, it was quickly complicated by other factors. The inability to return Enterprise’s three RS-25 Space Shuttle Main Engines to the ground had long been a sore point, and the lunar program’s expected need for two to six Shuttle-C flights per year would stress production of even a cost-reduced RS-25. Thus, the design for Shuttle-C evolved to include a reusable boat-tail, incorporating the three SSMEs and the vehicle’s avionics into a single package capable of diving through the atmosphere nose-first and surviving for recovery via a parachute post flight. Though more complicated than simply excising the propulsion boat-tail from the orbiter design and building a cost-reduced expendable copy, the development of this reusable propulsion and avionics module was anticipated to substantially reduce operational costs for the lunar program. Still, once the first major dam had burst, further changes came quickly.
The orbital propulsion and avionics module quickly became a platform for implementing other Space Shuttle “wishlist” items like the replacement of the Auxiliary Power Unit generators and hydraulics with a new system for gimbaling the three engines and aerodynamic surfaces using electro-mechanical actuators (EMAs). This would eliminate two fluid handling systems from the vehicle, making it substantially easier to service. A similar system had long been desired for the orbiter fleet, and indeed its addition to Enterprise had been studied during the station’s conversion with the goal of eliminating the need to launch an orbiter’s APUs for a mere eight minutes of operation. While introducing it to the orbiter fleet in the mid-80s had been a step too far, now they found their home on the two initially-ordered vehicles. Similar stories occurred throughout the detailed design of the stack, with the result that the program rapidly grew in both cost and schedule. A prime example of this was the decision to replace the Shuttle-C’s solid rocket boosters (as used on Enterprise and every other Space Shuttle launch) with new liquid rocket boosters. Serious issues with the solid rocket boosters had been found during the post-Discovery investigations, requiring the rapid implementation of plans to make the joints between the solid segments safer. However, the cost savings of reusing the solid rocket boosters had largely not turned up. The challenges of retrieving boosters from the sea, breaking them down and shipping them back to Utah for refilling, then returning them to Florida and restacking into integrated boosters left the costs of the refurbishment similar to simply manufacturing new booster casings. Liquid rocket boosters, particularly if their engines could be reused with the relatively cheap tanks expended, offered a chance not only to increase Shuttle-C’s performance but to do so while decreasing operational expense. While approved for Shuttle-C, there was hope of applying these changes over time to the main Space Shuttle program as well.
Many of these changes originated within Marshall, which formally directed the program, but given Shuttle-C’s formal subordination to Minerva’s budget line, all such changes also had to touch the desk of the new Associate Administrator for Exploration, Mike Griffin. Griffin had long had the personal belief that the loss of the Saturn V had been a tremendous setback for NASA, and had personally supported the Option F program and its larger-capability, Saturn V-equivalent, Shuttle-Derived Heavy Launch Vehicle (SDHLV). When taking over his new role overseeing Minerva in 1991, he was stuck with the size category which had been approved, but was determined to see it be as technologically advanced and operationally effective as possible to increase the odds of being able to apply it to programs outside of “just” Minerva. Griffin’s influence was key to the approval of many of the largest changes which would come to define Shuttle-C, including the liquid rocket boosters and the reusable Orbital Propulsion and Avionics Module. The politicking required for Griffin and Marshall to get their way on this scope creep meant delays both to approval and to availability of the final product. However, they argued successfully that with the clean-sheet lander as the primary pacing item, Shuttle-C had development time to burn. By the end of 1991, the design process for Shuttle-C was well underway. Marshall had issued contracts for all the major subsystems of the rocket: the Orbital Propulsion and Avionics Module (to Rockwell), the Payload Fairing (to Martin Marietta), the new Liquid Rocket Boosters (to General Dynamics), and the Exploration Upper Stage (to Boeing) which would finish the system’s job by injecting payloads to the moon and beyond.
While the new components of Shuttle-C proceeded into detailed design at Marshall, the Minerva team at Johnson focused on the conceptual details of the new lander design.The rough scope of the lander program was set by the selection of the launch vehicle and the missions NASA expected the vehicle to perform. The requirements NASA set out for their internal design teams and industry study partners to fulfill with the new “Lunar Surface Access Module” (LSAM) called for a lander which could be prepared for a lunar cargo or crew flight in just two launches of the Shuttle-C. Subtracting mass reserved for a lightweight crew return capsule, this would require a mass of no more than 40 metric tons fully outfitted for crew launch configurations and 42 metric tons for cargo-delivery missions. Within this the LSAM would have to fit the ascent and descent stages, the crew’s surface habitat, and the consumables to support a crew on the lunar surface for a reasonable time. NASA studies for Options D and E had analyzed the performance of the Apollo crews, and discussed in some detail the balance between a larger crew and a smaller crew staying for longer times. After all, the two-person crews of Apollo had performed admirably in all major mission tasks, including troubleshooting vehicles on the fly and carrying out surface science. Adding an additional crew member to the landing party required at least 200 kg of astronaut and support systems (such as an additional EVA suit). Expressed instead as additional consumables, even 200 kg was enough to double or triple the surface stay for a crew of two, while providing more gear to enhance their productivity. The loss from a smaller crew came mostly from the loss of redundancy in the event of an astronaut being injured during the mission and in the loss of specialization. Either selenologists and physicists would have to train sufficiently to take over systems engineering roles during descent as had Harrison Schmidt on Apollo 17, or the entire surface science capability of early sorties would depend on the training of pilot-turned-selenologists. Whether Minerva accepted missions little longer than Apollo but with twice as many crew or missions several times longer but with only the same crew capacity as Apollo, the lander would be a formidable science vehicle even for short sortie missions.
For plans further in the future, the capabilities of the vehicle would also have to be driven by the requirement to land a large emplaced habitat and other heavy hardware to support the development of a lunar base which the President and Congress had tentatively authorized, and which NASA hoped would materialize in truth. By using an additional two Shuttle-C launches, a second lander could carry almost 15 metric tons of cargo to the lunar surface. This was enough that a crew lander groaning under the requirements of landing at least four astronauts to the surface and returning them to space could be allowed to carry minimal other cargo, while still supporting a stay measured in weeks or months. Only a few such landings at the same site would rapidly build up the infrastructure of a permanent base to rival the capabilities of Space Station Enterprise in low Earth orbit. However, the challenges of designing the vehicle for crew and cargo delivery were non-trivial. The Shuttle-C payload shroud was cavernous, with axial height to spare. However, the height of the vehicle above the ground was a consideration for astronaut safety when alighting from the vehicle’s deck, and every meter above the surface complicated the task of moving massive cargo modules from the deck of a lander to the surface. In considering the award of the lander prime contract, NASA searched for ways to maximize the potential of the lander as a base-building element in ways which wouldn’t jeopardize the capabilities as a sortie vehicle. When Johnson awarded the contract for the new LSAM to McDonnell-Douglas in November 1991, it was at least partly due to their eager embrace of a unique concept which had emerged from Johnson’s teams in NASA “blue-sky” lander plans.
While the majority of NASA’s attention was drawn by the return to the moon, the Space Station Enterprise Program Office wrestled with suddenly being forced to execute what they had been dreaming about for years while being a distinct second in terms of internal priority. Officially, President Bush had identified the expansion of Space Station Enterprise into a fully crew-rated, permanently-occupied station as the immediate priority for NASA in the coming years. However, in practice the agency’s attention and that of their contractors and the general public was drawn like a moth to the more exciting prospect of a return to the moon. While authorized for the “Option B” permanently occupied station with expanded habitat and lab spaces, for the moment Enterprise was stuck as something quite similar to “Option A”--a work site which could temporarily house Shuttle crews during extended missions and which could host crew-tended experiments between Shuttle flights. Bridging the gap from one to the other while negotiating international diplomacy, standardization of systems designs across multi-national development teams, and the ongoing challenges of continuing to convert a Space Shuttle into an operational Space Station were anything but trivial. However, these challenges were difficult to convey to the public. The need to deploy the station’s massive solar arrays to allow it to survive had made for dramatic television during Atlantis’ STS-38R mission, but in order to power added labs and habitat spaces, new and larger panels would need to be added to augment the generation capability. The new International Standard Payload Rack had to be designed for the larger experiments to be installed in the Japanese and European lab modules, as well as the logistics modules for Shuttle to carry them to and from the station. At the same time, plans had to be fashioned to adapt the anti-slosh baffles into the LOX tank to the Spacelab Instrument Rack drawer which would be the standard equipment unit for life support systems, exercise gear, living, and hygiene facilities in the giant tank. The challenge of assembling an IKEA station using two fundamentally distinct equipment standards was difficult to excite public attention, unlike the more immediate goals of “following the footsteps of Neil Armstrong.”
Worse, many of the priorities for expanding Enterprise into a permanently crewed station ran directly into the needs of the moon program. With the drive to minimize spending, the Multi-Role Recovery Capsule had emerged as an interim stand-in for a lightweight lunar capsule in many NASA studies for lunar flights. Although it massed slightly less than the command module of the Apollo capsule, the MRRC offered a larger diameter and interior volume, enabling it to carry as many as eight astronauts in a lifeboat configuration. With a smaller crew, the same volume (augmented in most plans by the volume of a lunar module’s cabin) was more than capable of housing two or four astronauts to and from lunar orbit for sortie or outpost missions. With the role of lunar orbit insertion usually delegated to the more efficient thrusters of the lunar lander, only a few tons of added propellant would be necessary to allow the MRRC or an equivalent to return through Trans-Earth Injection. Better yet, the clean and safe ethanol/LOX fuels the Italians had selected for the MRRC to minimize risks of operating it in the Space Shuttle’s payload bay were also nearly passively storable in the lunar thermal environment while providing superior performance to hydrazine engines. Between Bush’s original 90-day study in 1989 and the approval of the Option D lunar program in 1991, this stand-in for a presumed American equivalent gradually became a presumption of partnership with ESA on the lunar program, as the European nations had no intention of being left out of the return to the moon if they could avoid it. Moreover, the MRRC was available sooner and cheaper than any American equivalent, as the first lifeboat missions to Enterprise were planned for 1993 and ESA would contribute the (relatively low) cost of converting the MRRC’s service module for lunar-return operations in exchange for seats aboard the American landers. The agreement was made formal with a memorandum of understanding in the spring of 1992, but had been all but assured for at least four months prior. The result for Enterprise was the hijacking of their lifeboat program. Just as fabrication had begun on the hulls of the first two lifeboats, ESA and the MRRC Program’s NASA liaisons enthusiastically turned to the problems of how to modify the design for the lunar program to the detriment of focus on the first prototypes intended for lifeboat use. Though priority snarls were ironed out over the next several months, the delays to MRRC development would directly push out the date when Space Station Enterprise could operate as more than a crew-tended station.