Good afternoon, everyone! Last week, we saw the end of the Richards administration, the departure of Lloyd Davis as NASA Administrator, and the beginnings of the Orion "soonbase" outpost program. However, this week, we're doing something a bit different, and covering some hardware-that-never-was from within the Eyes universe...
Eyes Turned Skyward, Part IV: Post #13
For today’s
This IS Rocket Science, I have one sentence for you: It wasn’t supposed to be this way.
The venerable old Apollo was supposed to be consigned to museums by now, nothing more than a historical relic--an important one to be sure, but still a thing of the past. It wasn’t supposed to be ferrying American, European, Japanese, and other astronauts to Space Station
Freedom. It wasn’t supposed to be the basis of two generations of supply tugs, carrying parts, equipment, food, water to
Freedom. And it most certainly wasn’t supposed to be the dependable old workhorse carrying the first humans back to the Moon in three decades.
Instead, there was supposed to be a slick new spaceship that would undergird NASA’s space exploration efforts. Bigger, better, more capable, it would be a giant leap past Apollos capabilities. And it would be cheaper, not only increasing
Freedom’s abilities, but freeing up money to pay for a return to the Moon, maybe even a mission to Mars and a Moon base. It would simply be the best spaceship available. But it never flew, while the dependable old Apollo kept trudging onwards.
It wasn’t supposed to be like this. But it is. Why?
Background
By the mid-1980s, soon after the beginning of the
Freedom project, NASA engineers could see that they had a problem. Apollo, a design dating back to the birth of NASA itself, had proven itself a reliable steed over the past decade, ferrying astronauts to and from Skylab and Spacelab, fully erasing the poor reputation it had been saddled with after Apollo 1. It had also proven itself flexible; the Block III and Block III+ upgrades had progressively improved its ability to serve as a space station ferry, while the more significant AARDVark modifications had produced a new kind of spacecraft, the space station resupply ship. However, both the III+ and AARDVark were limited, reactive, intended only to fulfill the demands of Spacelab.
Freedom would be something else. Bigger, with more astronauts living on it for longer, with more lab space, more experiments, more electrical power, more everything.
Freedom would be an entirely new type of space station, built in space from modules launched from the ground. Spacelab had taken a few tentative steps in that direction, with the Airlock Module and the European Research Module, but at its heart it had always been the modified S-IVB upper stage, containing most of its volume and all of its power supply, life support equipment, and other vital gear. These new requirements and new capabilities would impose new demands on
Freedom’s fleet of support spacecraft. Ten astronauts would require more rotation flights, more supply flights. Supporting the station’s array of external and internal payloads would put even greater demands on the latter. And assembling the station would require powerful tugs capable of moving massive modules with the delicacy of a ballerina and the flexibility of a gymnast.
Apollo and AARDV couldn’t do that, not as they were. Something new would be needed. Although the initial inclination of most of NASA’s engineers was to upgrade Apollo and AARDV as necessary to meet
Freedom’s requirements, a smaller faction, based at Johnson Space Center in Houston, Texas, proposed that NASA build an entirely
new spacecraft. Twenty years earlier, the demands of space station resupply on a similar scale had inspired the proposal of an entirely reusable launch vehicle, termed the Space Shuttle, to achieve it economically and cheaply; the insurgents were not so ambitious, but merely proposed to build a reusable replacement to Apollo and AARDV. Refurbished and reused after every mission, just a few of these new spacecraft could ferry supplies and astronauts to the space station again and again, saving the agency large amounts of money by eliminating the need to produce new vehicles for each mission and by eliminating the dedicated resupply craft. By being designed to modern principles, with modern equipment, and modern objectives, it would not be saddled with the quarter-century-old heritage of Apollo, making it better tailored to NASA’s current missions rather than NASA’s past ones.
It would have one more advantage, a powerful one, over the existing Apollo-AARDV combination: downmass capability. One problem that had plagued scientists and engineers throughout the Spacelab program had been an inability to ship equipment and experiments back from the space station when they were no longer useful. On the ground, broken equipment could be analyzed to identify design problems and perhaps even repaired and relaunched, while shipping back completed experiments could allow further research--such as witnessing the adaptation of animals raised in zero or partial gravity to Earth’s gravity--or modifying experiment design and reflying scientific payloads to build directly on previous results. With a capsule barely big enough to fit Spacelab’s five astronauts, however, only the most critical--and small--things could be shipped down from orbit. Anything else could only be crammed in an AARDV pressurized volume and allowed to burn up over the southern ocean, lost forever to scientists and engineers.
The insurgents called their idea the Reusable Cargo/Crew Craft, or RC^3 for short. While their idea was little more than a sketched outline, they were vocal and energetic in pushing it within Johnson, and they had considerable success in promoting it outside Johnson. RC^3 would be a new, interesting challenge, and would be good for the Center, attracting even more influence and funds. Even the director of Johnson soon became an advocate, pushing the project elsewhere in the agency.
With this level of support, RC^3’s success seemed preordained. But the Scylla that would eventually swallow the project whole was already apparent at the edge of vision: money. Specifically, development money. Engineers working on Block IV Apollo and Block II AARDV could, quite correctly, point out that RC^3 would cost more to develop than their projects, despite the significant modifications they were requiring to the basic Apollo design. They would not require any major design advances, unlike the hazy imaginings of a winged or lifting-body RC^3. Worse, Charybdis was already present on the other side, ready to gobble up the project with development time. Even in the most optimistic case, RC^3 would not be ready until after Freedom itself had begun construction, requiring at least a brief period of Apollo operation unless the whole station was delayed. Finally, while Johnson was inspired by the new money and influence that would flow through them, North American Rockwell, Apollo’s prime contractor, was terrified; they were not guaranteed to win the RC^3 contract, and if Apollo was not exactly a titanic moneymaker, it was still a profit center for the firm.
Still, the promise of a reusable spacecraft was enough in the long run that after deciding to go through with the Block IV/II upgrade program, NASA Headquarters gave its blessing to Johnson refining the concept, under the name “Advanced Crew Vehicle,” or ACV, under which it would forever afterwards be known. As it had since the 1960s, Johnson farmed this work out to its industrial contractors, both established firms like Lockheed and Boeing and a wide field of newcomers or non-manufacturers like Science Applications International Corporation. By 1989, these early studies were nearing completion, and a firmer idea of what the ACV was was beginning to emerge from their analyses. The spacecraft, all agreed, should have a reentry vehicle larger than Apollo’s, with most groups eliminating the large mission modules used by the Block III+ and Block IV spacecraft, allowing it to transport not only a crew but a substantial amount of supplies. All also agreed that it should be designed around the capabilities of the Saturn M02, the standard NASA crewed launch vehicle, rather than requiring a new vehicle.
Where they differed was not in these fundamentals of design, but in the finer details. Crew size, cargo capability, program of operations, and, above all else, the shape of the craft were points of contention. Winged and lifting body designs dominated, with Lockheed in particular peddling a scaled-down Starclipper, an idea they had tried to sell off and on to the military and NASA since the 1960s. Most of the major contractors followed this winged/lifting body line, in line with Johnson’s own preferences, but North American Rockwell notably bucked the trend with a scaled-up Apollo capsule, focusing more on streamlining operations and processing than exploiting advanced materials and designs in an eerie reflection of the “Big Gemini” concept that had been defeated by Block III Apollo as the resupply vessel for Spacelab.
Just as the ACV program was beginning to come together, President Bush launched a bombshell into the room with his announcement of the Constellation program in July. Although a number of Johnson personnel had been involved with the development of the Constellation concept, little of this information had leaked to the ACV group, and the entire space landscape was abruptly changed. Now the long-term goal was no longer a space station resupply vehicle but instead a lunar ferry that could be used to support Freedom, demanding radical changes in the design of the spacecraft. Most especially, the dominant lifting designs immediately became non-viable; under lunar reentry conditions, they would have serious thermal and stress problems, encountering high levels of heating and severe decelerations. Instead, more ballistic designs rose to prominence in the next round of studies, attempting to square the circle of allowing aerodynamic maneuvering without unacceptable stresses from lunar or planetary re entry.
The most successful contractor in this round was McDonnell-Douglas, who drew on their expertise in designing nuclear missile reentry vehicles to propose an entirely new design, the biconic. Although it had occasionally popped up in studies in the United States and elsewhere, McDonnell-Douglas’ design was by far the most developed biconic crew capsule ever proposed, taking full advantage of the design’s lifting body properties to largely square that devilish circle. While not initially popular, reanalysis of the Douglas design gradually won more and more of the Johnson team over, and by the time the next phase of contracts were being readied in 1992, Douglas was a heavy favorite to build the vehicle.
Then Bush lost reelection to the Democrat from Tennessee, Al Gore. Less than enthused about his predecessor’s programs, he quietly axed the ACV in 1993 among the more dramatic cancellation of manned Mars plans and other trims to NASA’s budget, after reviewing the state of the space program. Instead of a shiny new spacecraft, designed from scratch for NASA’s modern needs, yet another upgrade to the Apollo--the Block V--was contracted, lending the venerable old spacecraft another generation of operation.
Design
While many ACV designs were proposed during the project’s lifetime, the most developed, and most likely to have actually flown, was probably McDonnell Douglas’ biconic design, first published in 1990 and abandoned after the cancellation of the ACV project in 1993. The design never received an official name but was internally known as “Argo,” after the ship used by the Argonauts in their legendary voyage for the Golden Fleece.
The term ‘biconic’ refers to the shape of the spacecraft: a cone stacked on top of a truncated, less-sloped conical frustum, creating a shape reminiscent of a conical “bent pyramid”. As with all reentry vehicles since the 1950s, the edges of the vehicle, including the cone’s point, would have been rounded, to eliminate undue thermal stress during reentry. First used on a series of still largely classified nuclear warhead reentry vehicles during the 1970s and 1980s, the advantages of the biconic design for the ACV were that it combined relatively good performance during lunar reentry with aerodynamic maneuvering capability at high speed well in excess of any capsule design.
Being free from the basic Apollo capsule, the McDonnell design was free to pick a size optimised for the substantial payload of the Saturn Multibody family. The biconic design was based on a 5.5m diameter at the base, and consisted of two major structures: an outer aluminum isogrid skin, supporting the primary TPS (various options included replaceable ablatives, metallic panels, and ceramic tiles), and an inner aluminum pressure vessel which occupied most of the interior volume of the Douglas ACV. The planned vessel would have had 50% more volume available than a complete Block IV Apollo with a forward two-person flight deck in the nose and a reconfigurable “mid-deck” aft. This allowed the capsule to support up to seven people--two pilots and five passengers--during launch, reentry, and Earth orbital operations, or two pilots and tons of supplies. For lunar missions, four astronauts would be carried, with the difference being used by extra supplies and crew accommodations. An access hatch, for ground operations, would be located on the roof, and a docking tunnel and CADS docking adapter occupied on the ship’s rear. No airlock was planned; if an emergency EVA was required, the whole spacecraft would have to be depressurized and repressurized. Enough air would be transported to do so three times, in addition to normal consumption.
In the unpressurized area wrapped around the mid-deck were tanks of drinking water and fuel for the ACV’s maneuvering thrusters, together with other equipment and supplies. Most of the water and fuel tanks were located in the ship’s rear, wrapped around the docking tunnel/pantry; if a solar flare occurred during a mission, the tunnel would become the crew’s refuge, shielding them from solar protons. Waste would be stored around the refuge to ensure a constant level of radiation protection during the mission. Meanwhile, for the undesirable case of a launch abort, the capsule carried a set of high-thrust engines fitted at the very aft, surrounding the docking tunnel. Just like the Apollo escape tower, these could throw the capsule away from the fireball of an exploding Saturn (a vision all-too-familiar to those watching Spacelab 28). However, unlike Apollo’s tower, which was merely dead weight after launch and jettisoned, Douglas had plans to use the abort propellant either for on-orbit maneuvering or in several propulsive landing scheme similar to the Grumman Starcat.
Landing in general proved to be one of the biggest weaknesses of the design. While multiple approaches could be imagined to successfully land at a flat, good-weather site like Edwards Air Force Base or White Sands, both of which would be reachable even from
Freedom, the trouble was ditching during an abort over the Atlantic Ocean. For this reason, though propulsive landing on the abort engines received extensive consideration, the ultimate decision was to use a parafoil for the terminal landing phase, using it to gently guide the capsule onto a skid landing at Edwards or White Sands. Depending on the abort conditions, an off-nominal landing onto a runway or large, flat site could be achieved, although the spacecraft would likely be damaged, or stable horizontal flight could be achieved followed by individual bailout through the hatch.
For both lunar and Earth orbital missions, the core capsule (which massed around 15 tons) would be augmented by a service/mission module, attached to the spacecraft’s rear docking port. For lunar missions, the service module would store additional consumables and supplies, support solar panels capable of providing power during the surface stay, and potentially incorporate its own engines and propellant supply to act as an insertion stage. For Earth orbital missions, the spacecraft would sport a module which would raise its full weight to the capacity of the 26-ton Saturn Multibody, and which would focus more on resupply, adding even more pressurized cargo volume and in particular storing propellant for
Freedom’s fuel tanks. This was planned to allow a combination of crew rotation missions and dedicated cargo flights to replace the venerable AARDVark as well as Apollo.
Analysis
So, why did the Advanced Crew Vehicle fail? The answer is simple: Money and time. Specifically, ACV always seemed to cost too much in the short term to start, and always seemed to require too much time spent developing and building before it could start flying. Whenever there was plenty of time for development, money was short; and when money was plentiful, time was not. Hence, at every juncture where they could have decided to begin ACV development, NASA instead chose the cheap and fast path of another incremental Apollo upgrade, waiting on better conditions for ACV. In the end, with little more than empty coffers to show for years of work, it couldn’t survive even the slightest budget-cutting pressure.
That suggests how it could actually have flown. The Block III+ was not actually planned by NASA, but instead was a proposal by North American Rockwell intended to forestall further advanced non-Apollo spacecraft development at a moment when even Spacelab looked like too much for the Block III. By demonstrating the mission module technique, it set the stage for the Block IV and Block V upgrades that undercut the apparent future value of the ACV at critical points. If Rockwell had not developed the mission module concept, then there would have been no capability to upgrade the Block III enough for Freedom and something like the ACV would have been a necessity, rather than a nice to have. Freedom might have flown later, and Artemis perhaps not at all, but a new paradigm might have taken hold in spaceflight...
Related posts: Big Gemini, Space Shuttle
Alex Friedlander for TechNet, “This IS Rocket Science: Tidbits from the history of spaceflight” Copyright 2004
