Yet, originally, in the early development of the Shuttle, an EVA capability was considered unnecessary and was not provided. ''The NASA perspective of a Shuttle was an airliner,'' said spacesuit engineer Jim McBarron, ''and the people inside it wouldn't need suits. It was through prompting and questioning that Aaron Cohen, who was then the Shuttle project manager, finally accepted a contingency capability for closing the payload bay doors - which was an issue they were faced with - to put an EVA capability on the Shuttle.''
The plan was for Lenoir, designated 'EV1' with red stripes on the legs of his suit for identification, and Allen ('EV2') to test the snow-white ensembles and practice techniques for a tricky repair of NASA's Solar Max satellite, planned for the spring of 1984. They had also trained to perform a manual opening and closure of Columbia's payload bay doors, in the event that a malfunction should make it impossible to complete this task automatically. Although the excursion was only intended to last a few hours, it would have occupied virtually the crew's entire day on 14 November.
Assisted by Overmyer, the men would have risen early and begun preparing their suits and the Shuttle's airlock at 7:00 am, before spending the next four hours 'pre-breathing' pure oxygen to wash nitrogen from their bloodstreams and thus avoid attacks of the 'bends'. Their next step would have been to lower the airlock's pressure from the normal 14.7 psi to just 5 psi to check the integrity of the suits. Finally, a little under 73 hours into the mission, the two men would have opened the outermost hatch of the airlock and entered Columbia's payload bay.
The airlock was a cylindrical structure about the size of a Volkswagen Beetle, situated at the rear of the middeck. Its inclusion within the pressurised cabin was done to preserve the maximum amount of volume in the payload bay, and consisted of two hatches, one for the astronauts to enter from the middeck and another through which they would go 'outside'. The volume inside the airlock was cramped: astronaut Rich Clifford, who would make a spacewalk in March 1996, has described hanging there in his bulky spacesuit with his colleague, barely able to even move his arms.
Depressurisation and repressurisation of the airlock was, and still is, in the surviving Shuttles, controllable from the flight deck or from within the airlock itself. Normally, two spacesuits are stored inside the airlock, although there is room for up to four if needed. In fact, many Shuttle missions thoughout the 1990s and into the present century have involved four spacewalkers, working in two alternating pairs, and in May 1992 the airlock successfully demonstrated its ability to support three fully suited astronauts at the same time.
Later modification to most of the Shuttle fleet, in anticipation of planned dockings with the Russian Mir space station and the International Space Station in the mid to late 1990s, would lead to the airlocks being removed from the cabin and mounted instead in the forward part of the payload bay. It was decided, however, that one vehicle still needed a 'full' payload bay capacity for especially large cargoes, and Columbia retained her internal airlock. This proved beneficial when she carried the enormous Chandra X-ray Observatory into orbit in July 1999, which almost filled the entire bay.
Ironically, had she returned safely from STS-107 on 1 February 2003, Columbia's next mission in November of the same year would have been her first trip to the International Space Station. One of the most notable modifications planned in her preparation for that mission would have been the removal, after nearly a quarter of a century, of the internal airlock and its replacement in the forward part of the payload bay. Sadly, as everyone now knows, Columbia would never visit a space station . . .
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