Columbia's next flight - or rather flights - had multiple personalities, but instead of receiving attention from a doctor, it received the undivided focus of thousands of scientists, engineers, technicians, Shuttle processing workers and a close-knit team of seven astronauts. For STS-83 Mission Specialist Don Thomas, 1997 would prove to be one of the high points of his astronaut career: at the end of January, it seemed unlikely that he would be flying at all that year, but by the end of July he had flown not once, but twice!
Thomas, who had joined the astronaut corps in January 1990, had already flown twice by the time he was named to the STS-83 crew. In many ways, the activities he would be involved with on his third mission closely mimicked the experiments he performed on his IML-2 flight in July 1994. The payload for STS-83 - the Microgravity Science Laboratory (MSL)-1 - was expected to be not only the penultimate voyage of the Spacelab module, but also the last Shuttle flight fully dedicated to materials processing, combustion science and fluid physics research.
All future investigations in these disciplines, it was anticipated, would be conducted by long-duration crews on board the International Space Station, whose inaugural assembly flight was tentatively scheduled for the summer of 1998. In many ways, therefore, STS-83 was to be the last roll of the dice for many physical science investigators, and its importance was highlighted by a very experienced crew: Payload Commander Janice Voss would lead a three-member team - Payload Specialists Roger Crouch and Greg Linteris, together with Thomas - who were responsible for the bulk of the research in the Spacelab module.
Their backgrounds highlighted the nature of the investigations planned on MSL-1: Voss was an electrical engineer, Thomas a materials scientist, Crouch a physicist and Linteris - significantly - a combustion expert. Rounding out Columbia's crew were Commander Jim Halsell, Pilot Susan Still and Mission Specialist Mike Gernhardt, who would supervise the Shuttle's systems throughout a projected 16-day flight. Again highlighting NASA's policy to 'carry over' veteran astronauts on science missions, Halsell had previously accompanied Thomas on IML-2. Still became only the second woman to pilot a Shuttle and, with Gernhardt on board, STS-83 boasted no fewer than five PhD scientists on its crew.
Thomas' brush with bad luck came on 29 January 1997, after a year of training for the flight and only nine weeks away from launch: following an emergency egress training exercise at JSC, he slipped down some stairs and broke his ankle. Unlike the Russians, NASA no longer assigned backup crews to its flights, but on this occasion and in light of the mission's importance, it was considered necessary to quickly train another astronaut to stand in for Thomas, if necessary. By mid-February, it was official: astronaut Cady Coleman, who had flown USML-2, would train as his backup.
"We are hopeful that Don will be cleared for flight,'' said former astronaut Dave Leestma, then-Director of Flight Crew Operations and the man responsible for assigning and managing the training of Shuttle crews. "He is an experienced astronaut with the majority of his required training for this flight already complete. The decision to assign Cady as backup was made to protect all available options.'' Thomas was also assigned, with Gernhardt, as one of two contingency EVA crew members: Coleman immediately began refresher classes and familiarisation sessions with more than two dozen MSL-1 experiments and research facilities.
"Cady's previous experience makes the amount of training required to bring her up to speed minimal,'' Leestma added. Thomas, meanwhile, was determined to be ready in time for Columbia's scheduled 3 April liftoff. "I'm in a period of pretty heavy physical therapy right now,'' he told journalists on 13 March, "spending about five or six hours a day walking in swimming pools, walking with the cast and without the cast, just getting my mobility [and] strength back. We've got three weeks until launch and there's no doubt in my mind or the doctor's mind that I'll be ready in time.''
Whichever astronaut had been chosen to fly, few doubted Coleman's capabilities and aptitude, especially Linda Slaker, the Dean of Natural Sciences and Mathematics at the University of Massachusetts, who had known her for some years. "Cady is a very talented experimentalist, both innovative and very reliable,'' Slaker said. "She has her own speciality - polymeric materials - but she also has to be a quick study, able to learn the fine points of several very expensive experiments from other specialists who will stay on the ground and be able to earn their trust that each experiment will be carried out correctly.''
By mid-March, however, Thomas had been cleared as medically fit to fly and confidently awaited Columbia's 22nd launch on 3 April. Preparations for the mission itself had been chugging along relatively smoothly: integration of research hardware into the Spacelab module allocated to MSL-1 had begun in March of the previous year and was finished and loaded on Columbia around the same time that Thomas broke his ankle. The tunnel adaptor was installed to connect the module to the Shuttle's middeck on 14 February 1997 and the vehicle was moved to the VAB for stacking on 5 March.
Not everything went entirely to plan, however: while in the OPF, during planned modifications to existing lines in the bay's hypergolic fuel system, some highly toxic monomethyl hydrazine - the propellant used by Columbia's RCS steering jets - spilled onto two technicians. They and several others received minor treatment for exposure and possible inhalation, but the accident was not expected
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