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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Shuttle-Centaur | 8/9 | https://en.wikipedia.org/wiki/Shuttle-Centaur | reference | science, encyclopedia | 2026-05-05T13:20:55.194283+00:00 | kb-cron |
Two Shuttle-Centaur missions were scheduled: STS-61-F for Ulysses in the Space Shuttle Challenger for 15 May 1986, and STS-61-G for Galileo in the Space Shuttle Atlantis for 20 May. Crews were assigned in May 1985: STS-61-F would be commanded by Frederick Hauck, with Roy D. Bridges Jr. as the pilot and mission specialists John M. Lounge and David C. Hilmers; STS-61-G would be commanded by David M. Walker, with Ronald J. Grabe as pilot and James van Hoften and John M. Fabian, who was replaced by Norman Thagard in September, as mission specialists. As well as being the STS-61-F commander, Hauck was the Shuttle-Centaur project officer at the Astronaut Office. He and Walker attended key senior management project meetings, which was unusual for astronauts. The four-person crews would be the smallest since STS-6 in April 1983, and they would fly into a low 170-kilometer (110 mi) orbit, which was the highest that the Space Shuttle could achieve with a fully fueled Centaur on board. Centaur would periodically vent boiling hydrogen to maintain the proper internal pressure. The high rate of hydrogen boil-off from the Centaur meant that deploying it as soon as possible was essential to ensure it had sufficient fuel. Payload deployments were not normally scheduled for the first day to allow time for astronauts who came down with space adaptation syndrome to recover. To avoid this so as to permit a deployment attempt as early as seven hours after launch, both crews were entirely composed of astronauts who had already flown in space at least once before and were known to not suffer from it. The two launches would only have a one-hour launch window and there would be just five days between them. Because of this, two launch pads would be used: Launch Complex 39A for STS-61-G and Atlantis and Launch Complex 39B for STS-61-F and Challenger. The latter had only recently been refurbished to handle the Space Shuttle. The first Centaur G-Prime, SC-1, was rolled out from the General Dynamics factory in Kearny Mesa, San Diego, on 13 August 1985. The theme music from Star Wars was played, a crowd of 300, mostly General Dynamics employees, was in attendance, as were astronauts Fabian, Walker and Hauck, and speeches were given by dignitaries.
SC-1 was then flown to the Kennedy Space Center, where it was mated with CISS-1, which had arrived two months before. SC-2 and CISS-2 followed in November. The USAF made its Shuttle Payload Integration Facility at the Cape Canaveral Air Force Station available in November and December so SC-1 and SC-2 could be processed at the same time. A problem was detected with the propellant level indicator in the oxygen tank in SC-1, which was promptly redesigned, fabricated, and installed. There was also a problem with the drain valves, which was found and corrected. Shuttle-Centaur was certified as flight ready by NASA Associate Administrator Jesse Moore in November 1985. The Johnson Space Center committed to lifting 29,000 kilograms (65,000 lb) but the engineers at Lewis Research Center were aware that the Space Shuttle was unlikely to be able to lift that amount. To compensate, the Lewis Research Center reduced the amount of propellant in the Centaur. This limited the number of possible launch days to just six. Concerned that this was too few, Nieberding gave a presentation to key management officials in which he made the case to Moore for the Space Shuttle engines to be run at 109 percent. Moore approved the request over the objections of representatives of the Marshall Space Flight Center and Johnson Space Center who were present. The astronauts considered the Shuttle-Centaur missions to be riskiest Space Shuttle missions yet, referring to Centaur as the "Death Star". The main safety issue that concerned them involved what would happen in the case of an aborted mission, a failure of the Space Shuttle systems to put them into orbit. In that case, the crew would dump the Centaur's propellant and attempt to land. This was an extremely dangerous maneuver, but also an extremely unlikely contingency (in fact, one that would never occur in the life of the Space Shuttle program). In such an emergency, all the propellant could be drained through valves on both sides of the Space Shuttle's fuselage in 250 seconds, but their proximity to the main engines and the Orbital Maneuvering System was a concern for the astronauts, who feared fuel leaks and explosions. The Space Shuttle orbiter would then have to land with Centaur still on board, and its center of gravity would be further aft than on any previous mission. Hauck and John Young, the astronaut who was chief of the Shuttle office, took their concerns to the Johnson Space Center Configuration Control Board, which ruled the risk acceptable. Engineers at the Lewis Research Center, the JPL and General Dynamics dismissed the astronauts' concerns about liquid hydrogen, pointing out that the Space Shuttle was propelled by liquid hydrogen and at liftoff the Space Shuttle's external tank contained 25 times the amount of fuel carried by Centaur. Surprised by the board's approval of Centaur, Hauck offered his crew the opportunity to resign from the mission with his support, but no one accepted the offer.