Blue Shuttle – How the Air Force influenced the STS design process

Few spacecraft are quite so instantly recognisable as the Shuttle Orbiter. Even in retirement the surviving craft remain iconic, resplendent in their black & white thermal tiles and boasting their trademark double-delta wing.

But the story of how the Orbiter got its familiar shape and the Space Transport System reached it’s eventual configuration is an interesting one reflecting the requirements of the US Air Force more than the needs of NASA. So why did the Air Force have such a big hand in the design and what were their plans for the Shuttle? The story starts in the Apollo era of the late 1960’s.

NASA’s post Apollo Plans
As the Apollo programme recovered from the Apollo 1 tragedy, the flight schedule progressed rapidly. 1967 saw the Saturn V take flight and in 1968 Apollo 7 finally proved the Command and Service modules during the first crewed flight. As the year drew to a close, Apollo 8 propelled men beyond Earth orbit for the first time sending Borman, Lovell and Anders to the Moon.

Things seemed set fair for NASA to make good on Kennedy’s bold pledge to land a man on the moon and return him safely before the decade was out, but within NASA plans were already being drawn up to define the agency’s role in a post Apollo world. Having seen the Apollo Applications Programme lose support and funding in the wake of the Apollo 1 hearings, new ideas were needed.

What emerged was an integrated plan for a fleet of Space Stations in Earth and Lunar orbits serviced by nuclear powered shuttles. Heavy boosters of the Saturn V class would still be needed to loft the largest payloads, but for regular service flights to and from orbit NASA proposed a reusable Shuttle, with George Mueller instrumental in guiding the initial studies for this craft, outlining the early policy for the system prior to leaving NASA. Clearly a reusable craft that could be readily serviced and rapidly returned to flight would offer significant economic advantages over the expendable boosters used up to that time.

A number of ideas were studied in the early phases with Lockheed, McDonnell Douglas, General Dynamics and North American Rockwell developing initial designs for configurations that could meet NASA’s requirements. Lifting Bodies were one obvious direction, with the work being done at NASA’s Flight Research Centre at Edwards AFB in the Mojave validating their early promise. Some designs proposed piggy-back systems with a large reusable booster stage and a smaller orbiter. Others looked at large expendable booster stages that could loft a re-usable spaceplane. Single Stage to Orbit (SSTO) configurations were also examined as was a Trireme of three craft of which one would continue to Orbit, while the others returned to base.

Faget’s Design
Eventually the two stage fully reusable piggy-back configuration emerged as the most promising and the contractors were invited to concentrate on this. As with previous crewed vehicles, NASA’s Manned Spaceflight Centre worked on their own concept under the guidance of legendary designer Max Faget. Having earned his stripes as part of the original Space Task Group that designed the Mercury and later Gemini and Apollo capsules, Faget had demonstrated an innate ability to envision reliable craft by placing simplicity at the forefront. He now turned his attention to the proposed Shuttle and what emerged was a blunt bodied, straight winged Orbiter carried on a huge winged booster craft. The stack would launch vertically with initial thrust coming from the booster stage which would carry the orbiter to hypersonic velocities before releasing it to fly the rest of the way into orbit.

The configuration was hugely ambitious given that the booster stage was estimated to be around the size of Boeing’s new 747 airliner. Considering that it would need to fly at velocities and conditions only recently probed by the far smaller X-15 research aircraft, the scale of the challenge is apparent. The Orbiter would offer a modest payload capability, servicing the proposed Space Stations or even launching smaller payloads. It would return by flying through the atmosphere at a high angle of attack, presenting it’s blunt profile and creating a shock wave to keep the heat away from the structure – an approach Faget had used successfully in his capsule designs. As velocities slowed, the Orbiter would drop it’s nose and lift would be generated by the small wings. Cross range would be relatively low, somewhere in the range of 200 miles, but extendable turbojets would ensure the craft could reach its designated destination. Given that the proposed low inclination orbital track would bring the Orbiter back across the United States, a variety of landing strips could be made available, but the ultimate aim was to land at the launch facilities allowing for rapid processing and return to flight.

This approach seemed to offer a feasible and practical solution with more control and lower landing speeds as compared to a pure lifting body, but it wasn’t universally popular.

Early Air Force involvement
Since NASA’s earliest days, cooperation with the Air Force over booster systems had always taken place. It made sense to avoid costly parallel developments, and this approach had worked well for both parties throughout the 1960s. Within this cooperative environment, the Air Force Flight Dynamics Laboratory now examined initial designs for the Shuttle. Concerns were raised about Faget’s straight winged concept and its ability to cope with the transition from the re-entry phase to lifting atmospheric flight.

The Air Force pointed out that a delta wing would be far better equipped to cope with the changes in the centre of lift during such a transition and would also allow for manoeuvrability at hypersonic velocities during re-entry, something straight wings couldn’t offer. This manoeuvrability meant the vehicle would have greater cross range which was preferable in terms of abort scenarios. But the Air Force had other reasons to want to the additional cross range…

Justifying the Shuttle
By 1969, with the dust barely settled on the Sea of Tranquility, NASA’s Acting Administrator Tom Paine was working hard to push his Integrated Post Apollo plan, but things weren’t looking good. Although he found an ally in Vice President Spiro Agnew, it was clear that there was neither the appetite nor the funding for a large space exploration initiative from Nixon’s Administration. Public opinion had turned away from space, concentrating instead on the Vietnam War and social problems within the United States.

Through the Agnew-chaired Space Task Group, three options were presented to Nixon, but even these were subject to the harsh economic realities of the time. As the 1970’s dawned and inflation began to bite, the Bureau of Budget under Robert Mayo took a long hard look at NASA and demanded significant cuts. For Paine, this meant that rather than looking towards an expanded programme, he was faced with cutting Apollo flights, ending production of the Saturn V and fighting for the very continuation of piloted spaceflight.

From this bleak picture the Shuttle emerged as the main point of focus. Grand plans for Space Stations and planetary missions could wait, but a Shuttle would keep America in the game, providing a way to achieve these goals in the future while retaining orbital access and an economical launch platform in the near-term. Accordingly, focus switched to making the Space Transportation System a larger, more capable ‘space truck’ able to meet the majority of the Nation’s launch requirements at a fraction of the cost of expendable boosters.

As the Shuttle grimly hung on in the face of fierce Congressional opposition, narrowly avoiding cancellation in a tied vote, NASA’s attention turned to ensuring the Air Force launch manifest could be brought to the Shuttle. If this could be done, managers were confident that the numbers would stack up in their favour and justify the Shuttle’s continued development. But the deal would not come without costs to NASA as the Air Force had very specific requirements for any launch system that would replace their expendable boosters.

Whereas NASA had originally seen the Shuttle as having a limited payload capability and being mainly employed for station re-supply, the Air Force needed to loft large reconnaissance payloads and these would have to reach Polar or High Inclination orbits. The net effect of this was that to win Air Force support, the Shuttle would need a large cargo bay and Delta wings for increased cross range. Faget protested, continuing to champion his straight winged concept but it was clear that what the Air Force wanted, the Air Force would get – the choice was stark, with Paine gone and a new budget based pragmatism in place under new Administrator James Fletcher, NASA could agree to this or risk losing the Shuttle, and therefore crewed spaceflight, altogether.

The Influence of the Single Orbit Mission
The Air Force had long coveted a crewed presence in space. During the 1950’s they had worked on a number of plans to extend their presence above the atmosphere, starting with Man In Space Soonest (MISS) and moving on to more sophisticated systems such as the Dyna-Soar (see: Death of the Dyna-Soar). Their plans were undermined by Eisenhower’s decision to give the U.S. manned mission to a civilian Agency leading to the creation of NASA. Dyna-Soar fared no better falling to McNamara’s budget cuts in the early days of the Johnson Administration. Its replacements, Blue Gemini (A Military extension of NASA’s successful Gemini Programme) and the Manned Orbiting Laboratory also fell victim to cancellation before flights could be made.

Now, as the 1970’s dawned the Shuttle provided them with a new means to place Air Force crews in orbit. The deal on the table for them amounted to stating their ideal specifications, paying none of the development costs and eventually gaining the use of a Shuttle Orbiter for their own missions. The cost was turning away from their Titan III booster and developing their own Shuttle Launch facilities at Vandenberg AFB, California.

The reason that Vandenberg was so important to the Air Force was that it gave them access to the high inclination and polar orbits they needed to overfly the Soviet Union. It wasn’t possible to reach these orbits from Florida as this would have meant launching over populated areas, but Vandenberg gave them a clear shot to the South out over the Pacific and consequently launch facilities had developed there since the late 1950’s to support military satellite operations.

In conjunction with the Air Force, NASAs Mission Planning and Analysis Division (MPAD) began work in the early 1970s on defining Baseline Reference Mission 3. In BRM-3 the Shuttle would be launched from Vandenberg,  reach orbit and carry out its mission before de-orbiting next time round and returning to either Vandenberg, or alternate facilities at Edwards AFB. On such a mission, the Earth would still be rotating under the Shuttle, meaning that by the time it was ready to re-enter, its orbital track would be some 1100 miles to the west of the United States. Flying back to California would require considerable cross range. Added to this, any abort following  launch from Vandenberg would necessitate either a landing at an emergency site at Easter Island or a return to California after one orbit. This brings us back to the Air Force’s preference for Delta wings. By insisting these went into the Shuttle’s final design, the Air Force ensured they could get their single orbit mission and a margin of safety for all other launches from the west coast.

BRM-3 had two variants. 3A was to be a single orbit satellite deployment mission and 3B was to be a single orbit satellite retrieval mission. In both cases the workload would have been extremely heavy for the crew with only a short time available following orbital insertion for them to carry out the mission prior to beginning preparations for the de-orbit burn. Mission 3B would have been especially challenging given that the maximum time estimated between the Shuttle reaching orbit and reaching a station keeping position within 100ft of the target was 25 minutes.

Another more controversial version of mission 3B was apparently also discussed. If it could approach and retrieve a friendly satellite, surely it could do the same for a Soviet one. Single orbit ‘snatch’ missions were envisioned where the Shuttle could launch, retrieve a target craft and be back on the ground before it’s absence was noticed. Clearly, such a mission would have been massively controversial and may even have been construed as an act of war.

The Shuttle gets the go-ahead
Once the Shuttle program received Presidential Approval in 1972, a final configuration was settled upon that gave the Air Force exactly what they needed. North American Rockwell were appointed as prime contractor for the Orbiter which now boasted a 15 foot wide, 60 foot long cargo bay and a payload weight at takeoff of 65,000 pounds to Low Earth Orbit (approx 30,000 pounds to polar orbit) plus the ability to return around 30,000 pounds from orbit. Although this played well for the Air Force, it also allowed NASA to plan planetary probe launches from the Shuttle using booster stages and, importantly, the ability to ship space station modules to orbit when construction of such a facility was eventually approved.

The Air Force’s specifications had come at a cost though. In a March 1973 document dealing with BRM-3, MPAD concluded that “Missions 3A and 3B establish the minimum cross range that the Orbiter must be capable of flying during entry” and “Mission 3A is potentially the mission that sizes the shuttle”. Mission 3B in particular would have driven the requirements for the Orbiters rendezvous sensors allowing for the rapid approach to the target object.

The Orbiter had increased in size, most notably in terms of its wing area. Given the re-entry characteristics of the delta wings, this meant higher temperatures for longer than in Faget’s original straight wing design. Consequently, the Thermal Protection System (TPS) became more complex and heavier. The increase in the length of the payload bay meant there would be little room for internal propellant for use during the boost into orbit. As a result an external tank was proposed, supplemented by re-usable booster rockets. Initial investigations into liquid fuelled boosters took place, but these proved too costly and complex so the cheaper, quicker route of solid propellants was taken, this technology already being in use on the Titan III. While developmentally simpler than a ‘flyback’ fully reusable booster stage, the external tank and solid rocket boosters presented engineering compromises and both eventually led to the loss of vehicles: Booster O-ring impingement causing the loss of Challenger and foam shedding from the external tank causing the TPS damage that led to the loss of Columbia.

Shuttle operations at Vandenberg
In 1975 the green light was given to develop the required facilities for launch and recovery of the Shuttle at Vandenberg. The launch facilities would be created by converting the existing SLC-6 facilities developed for the MOL project prior to it’s cancellation. Construction began in 1979 and by 1986 facilities were essentially complete, although concerns remained about the acoustic suppression system for use during launch. There were also unanswered questions about how the weather conditions on the California coast would have affected regular Shuttle operations.

The Vandenberg launch facilities were striking for their linear arrangement and the close proximity of assembly structures to the pad. There were certainly great risks to the whole facility should a catastrophic incident occur at launch. During 1985 the vehicle handling procedures were tested with an STS stack featuring the Shuttle Orbiter test article, Enterprise.

Unfortunately for the Air Force, this was as close as they would ever get to seeing a Shuttle launch from Vandenberg. Although the ongoing safety concerns about the launch facilities continued, it was events back in Florida that finally ended the prospects for the military Shuttle. When Challenger was lost in January 1986 the Air Force began a process that led to the cancellation of flights from Vandenberg, curtailing future involvement with the STS and returning military payloads to expendable launch vehicles.

The Soviet Response
One interesting consequence of the Air Force’s input into the Shuttle’s design was the fear it created in the Kremlin. Although now often viewed as cold war paranoia given the essentially benign nature of actual STS operations, it seems at the time the Soviets were well aware of the proposed single orbit BRM-3 missions from Vandenberg and these led to great alarm about what else the Shuttle may do on such a mission. Soviet Defence chiefs certainly seem to have regarded the Shuttle as a possible first-strike weapon, although given the preparation time for launch this seems impractical.

The immediate Soviet response was to instruct their new Chief Designer, Valentin Glushko, to create a response. While Glushko had come into his post with cherished hopes of achieving what his great rival Sergei Korolev never could by taking Cosmonauts to the moon, he quickly found his energies re-directed to the massive Energia launcher and the Buran Shuttle. Unlike the American STS, Buran had no large rocket engines, relying on the boost from Energia, but this served Glushko’s plans as it still left a heavy lift booster capable of fulfilling his lunar ambitions.

There were also rumoured to be plans for a smaller ‘interceptor’ space plane based on the earlier Soviet Spiral 50/50 designs, often named as Uragan (Hurricane) whose missions would have included the interception and possible destruction of American Shuttle Orbiters. There is little definitive evidence as to whether Uragan actually existed, but the concern the military Shuttle missions generated in Moscow was real enough. For more on Uragan, see Dream Chaser DNA: A story of spaceplane evolution

Conclusions
The Space Transportation System never was able to live up to its early promise either for NASA or the Air Force. Partly because of the more complex design, the Shuttle was never able to achieve the routine ‘airline like’ operations that had been suggested. Regarding the Air Force’s plans for single orbit missions from Vandenberg, the BRM-3 requirement seems to have been quietly dropped by 1977. Its not known whether these missions would have been plausible with the Shuttle as finally built, given the very tight schedule they would have required. They may also have proved too controversial for the Air Force to wish to proceed. As renowned analyst James Oberg commented “The [Air Force] was never clear about just WHAT was to be deployed or retrieved but it was probably something likely to get the Russians REALLY mad, which is why the shuttle would have to land immediately afterwards.”

In the end the Air Force’s proposed use of the Shuttle seems to have suffered from the same inherent flaw as both Dyna-Soar and MOL before it – there seemed no overriding justification for why their missions needed to be crewed when their objectives could be achieved more economically with expendable craft. Although classified missions were flown out of Kennedy Space Centre, they never came at the frequencies discussed during the Shuttle’s early development.

The experience with the Shuttle didn’t stop the Department of Defence from trying for a spaceplane though. Throughout the late 70’s and 1980’s research continued into an elusive reusable winged orbital vehicle. Initially classified under projects such as Copper Canyon this requirement surfaced into the white world as the X-30 National Aerospace Plane (NASP) in 1986, although it always had close ties to the proposed deployment of Reagan’s Strategic Defence Initiative. By 1991 no workable solution to the X-30s requirements could be found – or if it was, it remains classified – so that programme was also cancelled. The Air Force also briefly looked into resurrecting the Lockheed Martin X-33 after that program was cancelled in 2001, but again this appears to have gone nowhere.

The Shuttle will often be remembered for it’s flaws and the compromises forced onto it’s design by a combination of military requirements and budgetary constraints during its long development. The tragic losses of Challenger and Columbia and their crews cruelly highlighted the system’s shortcomings, but the Shuttle’s more positive legacy lies in it’s roles in the construction of the International Space Station and the deployment, repair and servicing of the Hubble Space Telescope – no other vehicle could have achieved these missions at the time. When Atlantis rolled to a halt on the programme’s final flight in 2011, the various Orbiters in the fleet had completed 135 flights and carried over 3 million payload pounds into orbit.

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Author’s Note
In this article I’ve concentrated on one aspect of the developmental history of the Space Transportation System, or Shuttle. In doing so I have only mentioned in passing what were at the time major discussions relating to NASA budgets and roles in the late 1960’s and early 1970’s. To cover these in detail would have required a far longer article but I would recommend and interested readers to refer to The Space Shuttle Decision: NASA’s Search for a Reusable Space Vehicle by T.A. Heppenheimer. This official NASA history details the challenges faced in great detail.

Similarly I haven’t referred to the Shuttle’s operational record for similar reasons. Several excellent accounts exist for this period of the Shuttle’s history.

Sources
The Space Shuttle Decision: NASA’s Search for a Reusable Space Vehicle by T.A. Heppenheimer

The Shape of Wars to come by David Baker

Space Shuttle Systems Baseline Reference Missions Vol 3 – Mission 3A and Mission 3B: JSC Internal Note No. 73-FM-47  by NASA MPAD – Available online via James Oberg’s site at: http://www.jamesoberg.com/sts-3A_B-DRM.PDF

MIT Aircraft Systems Engineering Course (16.885J / ESD.35J) : Lectures 1 & 2  – available online at http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-885j-aircraft-systems-engineering-fall-2005/index.htm