Spacelab had been commissioned in the aftermath of the 1972 decision to abandon plans for the development of a large orbiting space station, beyond Skylab. With this decision, NASA realised that it would need to come up with an interim means to conduct the space science that the station would have provided, and they began looking at the proposed Space Shuttle for solutions. With congressional pressure mounting for NASA to privatise, the Spacelab module concept provided planners with an agreeable solution that would also allow the space agency to foster international cooperation - a key mandate for the future of space science and exploration.
Spacelab had initially been developed in the 1970s under the auspices of the eleven-member European Space Agency (ESA). During early development planning for the Space Shuttle, NASA realised that it needed a working facility independent of the cramped, noisy and crowded flight and mid-deck areas. At one time NASA had entertained thoughts of building the laboratory itself, but post-Apollo retrenchments
caused them to forego this option. The space agency turned instead to its European counterpart for assistance. ESA representatives began productive discussions with NASA on developing a pressurised, non-deployable modular research facility that could be launched inside the proposed Shuttle's cargo bay, operating in various configurations and combinations for specific types of missions.
On a flight such as STS-9, with seventy-one experiments to be conducted, there was simply not enough room in the Shuttle mid-deck area to accommodate all the experiment controls and displays. "They all took volume and panel area to hold the hardware and controls for their operation,'' according to Garriott, "and all this activity would otherwise have to go in the mid-deck area, where the off-duty crew was having to sleep! There was simply no room to run this many experiments, around the clock, without a separate module.''28
The pressurised module used on STS-9 was the "long" version, 7 m in length and 3.96 m in diameter. Experiments were carried out using floor-mounted single or double racks (all side-by-side) and a workbench. Access to the laboratory, mounted in the aft section of the payload bay (due to centre-of-gravity limitations), was achieved by entering a pressurised, cylindrical tunnel through the crew module airlock in the mid-deck. There was a 107 cm vertical offset of the mid-deck airlock to the airlock at the centreline of Spacelab, so the tunnel and its adaptor had been designed with a compensatory "joggle" section, which the astronauts had to negotiate. The "joggle" also permitted a small amount of longitudinal movement during the ascent and descent phases of the flight, helped absorb movements caused by the differential expansion rates of the orbiter and Spacelab module, and minimised any overstressing that might have occurred in a straight-tunnel/adaptor configuration.
Spacelab, like Skylab before it, represented a true amalgamation of space engineering and fundamental scientific research in the manned space effort. As Spacelab Mission Manager Harry Craft stated prior to the STS-9 launch: "We are reaching a major milestone in the space program.''29
The Shuttle/Spacelab combination offered several advantages for space science, mainly onboard scientists and other experts who could conduct and monitor experiments, maintain equipment, serve as test subjects, evaluate data, and make crucial decisions on the spot. The facility would also provide an observatory base for a global view of Earth and an unobscured view of the universe using larger, more capable instruments, the ability to retrieve and return experiment samples and apparatus for later analysis and possible re-flight, and serve as a test-bed for new equipment and research techniques.
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