by Jay Chladek
The next logical step after man had taken his first steps into space would be to find ways to spend more time in orbit. The construction of a space station was the most likely way to achieve that. The Mercury spacecraft design was limited in its capabilities since it did not have the ability to change orbit. A follow-up spacecraft was needed. But there were still limits to what even a larger capsule could do. Having in orbit a station that a capsule could dock with and that men could occupy for longer periods seemed like a worthy goal NASA should pursue, but it didn’t happen quite that way.
Shortly after astronaut Alan Shepard became the first American to fly in space, U.S. president John F. Kennedy put NASA and the country on a path to land on the moon before the Soviets at the end of the 1960s. His advisors felt that this was the best goal to exploit. It would force the Soviets into a sustained test of capabilities where the limitations of their design philosophy and political ideology would potentially be exposed. At the same time, it would showcase the technical expertise of the United States to the rest of the world.
A prime reason for a space station’s existence in fictional works was to service spacecraft headed out to explore elsewhere. A logical idea was that if NASA were to place a station in orbit, it could act as a floating fuel stop for a craft headed to the moon. But again, a station was not in the cards. Instead, two approaches were considered in Project Apollo’s lunar-landing goal: direct ascent and Earth-orbit rendezvous. In direct ascent, a massive rocket launches one spacecraft to the moon with all the fuel it needs. The spacecraft on top lands, and the astronauts perform their tasks and then return home. Earth-orbit rendezvous, on the other hand, required the launching of two or more smaller rockets with a part of the lunar spacecraft. The ships would rendezvous and dock in Earth orbit to transfer the fuel between them, and the completed spacecraft would fly its mission to the moon and back. Neither method required a space station, although an Earth-orbit rendezvous might leave some hardware in orbit for later use.
While NASA received a sizeable amount of funding for Apollo, it wasn’t unlimited, and the agency still had to get creative in terms of what mission profile to use. Ultimately, a new mission profile known as Lunar Orbit Rendezvous was created to help save fuel by landing a purpose-built craft on the moon while the heavier launch and recovery spacecraft remained in orbit. This approach meant that nothing would be left in Earth orbit once the spacecraft was on its way to the moon.
NASA’s plate was going to be full for almost a decade with the lunar-mission goal. The follow-up program to Mercury, known as Project Gemini, tested many of the techniques needed for a flight to the moon while also testing the endurance of men and equipment for periods up to fourteen days in orbit. Mercury’s short-duration spaceflights and Gemini’s goals provided experience on living and working in space. But beyond two weeks for a flight to the moon and back, there were still plenty of questions about long-term stays in space that needed to be answered.
The air force still had a major interest in space. They regarded it as the next possible battleground, especially if the Soviets had similar thoughts. Concerns about the effects of long-duration spaceflight weren’t necessarily limited to just human beings, as no one quite knew what the effects would be on equipment. While American satellites had been flying since 1958, their limited battery life and endurance, plus the fact that they couldn’t be recovered, meant that there was no way to see exactly how the space environment was affecting their systems.
Hostile to man-made objects, space is an environment of extremes. The temperature change alone between direct sunlight and shadow provides challenges of thermal control to ensure that the internal contents of a spacecraft, be they manned or unmanned, don’t overheat or freeze solid. There are also the very harmful effects of solar radiation and cosmic rays to consider. The microgravity environment also means that objects designed for use in a 1-g environment might not behave quite the same. Loose balls of solder undetected on a circuit board might float free to touch electric terminals, potentially causing an electrical short. Other particles floating free could get into places where they weren’t supposed to go. Heat convection doesn’t act the same either in zero gravity, since heated air can’t rise above cool air. Even moisture expended by astronauts from sweat, urine, and exhalation can cause condensation on critical equipment. Unforeseen problems can creep up when least expected as missions grow longer.
There were also the questions of what people do when they reach orbit and how such tasks could be exploited for military gain. To the air force, space was an extension of their territory. The air has always been seen as a strategic high ground, going back centuries to when an army might place lookouts on hills to see what an opposing force was doing. During the American Civil War, observation balloons were first used to look far in the distance. When World War I broke out, the airplane made the tethered observation balloon all but obsolete.
Reconnaissance airplanes became a primary source for gathering visual intelligence of other countries both during and after the Second World War. As jet engines were created and refined, these aircraft became more specialized and could fly higher than defending fighters. Yet as the Soviets developed their own high-performance jet aircraft, recon planes became more vulnerable.
It was the Central Intelligence Agency (CIA) who would fund and develop one specialized aircraft that could potentially fly out of range of any antiaircraft defense at the time, and that was the U-2 spy plane. However, when the Soviets successfully managed to shoot down a U-2 flown by Francis Gary Powers deep over their territory on 1 May 1960 with an S-75 Dvina surface-to-air missile (SAM), the days of reconnaissance aircraft directly flying over the Soviet Union were numbered.
Development of much faster aircraft in the form of the A-12 and SR-71 Blackbirds would make photographic intelligence gathering by airplane viable for many more years. But the mission of direct overflight was largely abandoned in favor of flying along a country’s border so as not to risk being shot down. Beyond what could be seen from that distance at extremely high altitudes, there was no direct means of observation. A manned spacecraft orbiting overhead would have little fear of being intercepted.
Weapons delivery from space, as von Braun predicted, was another possible use. But international politics had made the deployment of offensive space weapons something that the West either did not want to consider or at least make public. In October 1961 the Soviet Union air-dropped and detonated a fifty-seven-megaton hydrogen bomb (since nicknamed the Tsar Bomba). It was a prototype for a one-hundred-megaton nuclear device that could be placed in Earth orbit to remain dormant until a war broke out. It has recently been revealed that Soviet premier Nikita Khrushchev considered the one-hundred-megaton orbiting bomb to be more of a political bluff, rather than something seriously considered for operational deployment. In 1961, however, the idea that such a weapon might be flown operationally was very real.
With the role of an orbital offensive weapons platform effectively out of the picture, the air force looked to other military applications that it could perform in orbit. Several internal air force studies were conducted in a proposal to fly a vehicle known simply as the Manned Orbiting Laboratory, or MOL. With NASA’s manned efforts focused on the lunar-mission mandate, having the air force develop a manned space station seemed like a good idea, although it had to receive Department of Defense (DoD) approval and funding first.
In years past, when the air force had received funding to develop dedicated experimental aircraft, its research goals were pretty clear-cut to fly higher, farther, or faster. Long before the Department of Defense was created in 1947 along with the U.S. Air Force as a separate branch of the U.S. military, dedicated test airplanes had been built to push the frontiers of their capabilities. Following the creation of the DoD, dedicated military programs now had to justify their existence. So a proposal to investigate the long-term effects of spaceflight and to test applications of military technology with no specific goal or mission in min
d seemed like a potential waste of military dollars.
The lack of a clear-cut goal had already affected another air force program. This was the Dyna-Soar space plane, later known as the X-20. The name of the vehicle was an abbreviation of the term “Dynamic Soaring.” It was designed to launch into space atop a Titan booster in a high suborbital trajectory but not quite at orbital velocity. In order to keep itself in space, the craft would skip off Earth’s atmosphere in a similar fashion to a thrown stone skipping off the surface of the water, until its speed dropped low enough to reenter the atmosphere and land on a conventional runway.
When conceived in 1957, the Dyna-Soar had two planned missions: nuclear strike and strategic reconnaissance. Eventually, the nuclear mission became obsolete as ICBMs matured to become effective weapons. The reconnaissance capability was also given a lower priority due to the development of the first-generation Corona satellites, initially launched as part of a cover project known as Discoverer. Even with the very high speeds and altitudes at which the X-20 was designed to fly, its original missions were still considered high risk, as a threat nation might employ a shoot-down capability. As a result, the air force was left trying to find a new mission to justify the X-20. They were able to keep the project going a little longer by proposing its use as a rescue vehicle in the event of Gemini or Apollo astronauts becoming stranded in orbit due to a malfunction. Giving the vehicle an experimental “X” designation in 1962 also meant that it was being pitched to the DoD as a research craft rather than as its original concept as an operational vehicle with a specific military mission.
In December 1963, U.S. secretary of defense Robert S. McNamara cancelled the X-20 project. As a replacement, the Air Force decided to focus its efforts on the MOL program. The Department of Defense complied, altering its policy a little to allow the program to be funded, even though its goals were considered to be more open-ended, at least in public. In August 1965, President Lyndon B. Johnson directed the Air Force to commence work on the project. While the decision was regarded as a good one in some circles, elsewhere it left more questions than answers as the Air Force was somewhat evasive in discussing exactly what the MOL would do once it achieved orbit. Since this program wasn’t being flown by NASA, the Air Force did not have to publicly disclose its objectives, and various elements of the program remain cloaked in secrecy to this day.
The Douglas Aircraft Company became the main contractor for the MOL design. But rather than assigning a prime contractor to build the MOL and having it coordinate subcontractors, as with an aircraft contract, the air force assumed the coordination role. The air force would define the specifications, the contractors would build the hardware, and the air force would take delivery and perform the final assembly work themselves. This was done to help maintain a higher level of secrecy.
Anatomy of the MOL
In some aspects, the MOL borrowed heavily from hardware that was already built or in development to help save both time and money. Stacked on top of the MOL was a modified version of the two-man Gemini capsule, known as the Gemini-B, which was built by McDonnell Aircraft for NASA (McDonnell and the Douglas Aircraft Company would merge into one company in 1967 to form McDonnell Douglas Corporation). Behind the capsule and its mission adaptor section was the MOL itself, housed in a cylinder measuring 10 feet in diameter by 56.5 feet long. Including the Gemini capsule, the entire complex was just over 72 feet in length.
Just behind the modified Gemini spacecraft with its adaptor section was an eight-foot-long equipment section containing fuel and consumables tanks, plus reaction control thrusters for the laboratory. The pressurized habitat section was located just behind the equipment section. It measured about twelve feet in length, with the interior layout set up with the front of the spacecraft being the top and the rear being the bottom, as opposed to a horizontal layout seen on many subsequent space stations. Behind that was a thirty-seven-foot-long mission module section.
The entire vehicle, complete with astronauts in the Gemini capsule, would launch into orbit aboard a modified Titan III rocket. The Titan III was a stretched version of the Titan II ICBM, which itself was being used for NASA’s Gemini program. Improvements were made to the newer Titan III’s engines, and additional power for the rocket was provided in the form of a pair of five-segment solid-rocket motors (SRMs) strapped to the booster, one on each side. The Titan III system, both with and without the SRMs, would become a workhorse space launcher for DoD payloads until the early 1980s, with versions of the rocket also being used to fly unmanned NASA probe missions to Mars and the outer planets.
For the MOL, the Titan III-M booster would use a set of slightly longer seven-segment SRMs for added power. In this configuration, the Titan III-M could loft a payload weighing sixteen tons into a polar orbit or nineteen tons into an equatorial orbit. While the Titan III-M never flew operationally, the longer SRMs were paired with a modified version of the Titan III core to create the Titan IV launcher, which flew from 1989 until 2005. The Titan series rockets were eventually retired from service, in part because they used hypergolic propellants. Hypergolic fuels combust on contact with one another, meaning they don’t need a spark to ignite. The fuels are highly efficient and storable. But they are also very toxic, and it doesn’t take much exposure to kill an unprotected human.
2. Manned Orbiting Laboratory concept, with Gemini capsule in front. Courtesy U.S. Air Force.
While the Gemini capsule was designed for docking operations, it was only intended to dock with a test target vehicle in orbit and not a pressurized craft. Internal crew transfers between docked spacecraft wouldn’t be carried out until the Apollo spacecraft began flying. That left the problem of how to get the crew from the Gemini capsule into the MOL and back again before undocking and reentry. Various proposals were considered. One proposal had astronauts spacewalking to and from the lab. Another had them entering the lab via an inflatable, external transfer tunnel. Still another had the capsule pivoting around on a giant hinge until it lined up with a transfer hatch on the laboratory.
The method ultimately selected was fitting a hatch in the capsule’s heat shield and having the crew transfer between the Gemini and the habitat section of the MOL via a pressurized transfer tunnel that went through the Gemini’s heat shield and adapter section. While this method was considered the best, it had a few problems since it meant the internal configuration of the Gemini spacecraft had to be altered somewhat to accommodate both items. Another worrisome aspect was that no one knew if a hatch could be designed to withstand the heat of reentry without compromising the integrity of the spacecraft’s heat shield. It would require testing to prove that the concept was a sound one.
Once the crew transferred into the MOL’s habitat section, the Gemini would remain shut down in cold storage. It would not be used again until the return to Earth. The astronauts would spend the entire mission inside the MOL. The MOL’s habitat section could also act as an airlock module, should the mission call for a space walk, also known as EVA (extravehicular activity). Inside the module, the crew would have all the comforts of home in the form of sleeping berths, a food-preparation area, an exercise bicycle, and a zero-g vacuum toilet. A control panel would give the astronauts full control of the orbital attitude of the MOL and the mission module’s equipment. Unfortunately, there was no window present in the MOL’s habitat module, so astronauts would have no view of what was going on outside except for what they could see through their mission module’s periscopes.
Even before the Apollo 1 fire occurred in late January 1967, the air force had misgivings about using pure oxygen in a spacecraft due to the potential fire danger, and there were medical concerns about the possible side effects of breathing pure oxygen for long periods. A two-gas oxygen-nitrogen system was the most ideal solution, but it would have added weight and complexity. Eventually, the air force settled on a two-gas system featuring 31 percent helium and 69 percent oxygen at 5 psi (pounds per square inch). Helium is an inert gas that will n
ot contribute to combustion, and it is lighter than normal air. One potential drawback was the fact that helium affects the pitch of people’s voices, causing them to sound like Donald Duck when talking. This side effect may have been considered a positive one as it would be almost impossible to identify who was flying an MOL mission from their voice transmissions.
Power for the MOL would come from either solar panels or fuel cells. Both systems were considered for their advantages, and provisions were made to equip the MOL with either one, depending on the length of the mission. For missions lasting less than thirty days, fuel cells would be carried because of their simplicity as they utilized oxygen and hydrogen to produce electricity. As a by-product, they produced water, which could be used for drinking and cooling electronics. But fuel cells can only produce power for as long as they have reactants. Solar panels, on the other hand, are better suited for longer missions since they generate electricity as long as they have sufficient sunlight. However, storage batteries are needed to maintain electrical power when a spacecraft is not in direct sunlight, and relatively large solar arrays are needed to generate an equivalent amount of power to what fuel cells can generate. Solar arrays would only be used for missions intended to last longer than thirty days.
At the end of a mission, the MOL would be shut down; once the crew had transferred into the Gemini spacecraft, they would prepare for a return to Earth with the results of their experiments. Once the Gemini had undocked, the MOL would be commanded to deorbit and burn up since there were no provisions for other spacecraft to dock with it (at least not initially, although the idea of docking two MOL’s together back-to-back was proposed). This approach seemed somewhat wasteful, but it had the added benefit of newer MOLs being steadily improved in quality over the earlier versions as the U.S. Air Force became more proficient at building and operating them.