STS-55

Flight Crew

NAGEL, Steven Ray, 47, USAF, commander, 4th mission Previous missions: STS 51-G (1985), STS 61-A (1985); STS-37 (1991) HENRICKS, Terence Thomas “Tom”, 41, USAF, pilot, 2nd mission Previous mission: STS-44 (1991)

ROSS, Jerry Lynn, 45, USAF, mission specialist 1, payload commander, 4th mission

Previous missions: STS 61-B (1985); STS-27 (1988); STS-37 (1991) PRECOURT, Charles Joseph, 37, USAF, mission specialist 2 HARRIS Jr., Bernard Anthony, 36, civilian, mission specialist 3 WALTER, Ulrich, 38, civilian, German payload specialist 1 SCHLEGEL, Hans William, 41, civilian, German payload specialist

Flight Log

Getting STS-55 off the ground proved to be one of the more frustrating tasks of the Shuttle programme. The launch was originally set for late February 1993 but slipped back after problems arose with the turbine blade-tip seal retainers in the high-pressure oxidiser turbo pumps of the SSMEs. The option chosen was to replace the turbo­pumps at the pad, pushing the launch back to 14 March. This new launch date slipped when a hydraulic flex hose burst during a Flight Readiness Test. All twelve lines were removed and three of them had to be replaced before they could all be reinstalled. The revised 21 March launch was delayed by 24 hours due to a one-day delay in the launch of a preceding Delta II mission. Then, at T — 3 seconds on 22 March, the launch was aborted again by orbiter computers, this time because the #3 engine had failed to ignite. The third pad abort in the programme (the others being STS 41-D in 1984 and STS 51-F in 1985) was later traced to contamination during manufacture that had caused overpressure and precluded full engine ignition. All three engines were

replaced with spare units. The next attempt, on 24 April, was scrubbed when one of three IMUs gave possibly faulty readings and a 48-hour delay was scheduled to allow the removal and replacement of the IMU. Finally, on 26 April, the launch proceeded without incident. Following the launch, Pad A was scheduled for a period of refurb­ishment and modification which would last until February 1994.

The second German Spacelab mission featured 88 experiments in materials and life sciences, technology applications, Earth observations, astronomy and atmo­spheric physics. The crew would work in two shifts. The Red Shift comprised Precourt, Harris and Schlegel, while Nagel, Ross, Henricks and Walter worked the Blue Shift. After all the dramas of getting the mission off the ground, the crew encountered further problems in orbit. An overheating orbiter refrigerator/freezer unit in the mid-deck necessitated the use of a back-up to store samples, while a leaking nitrogen link in the waste water systems had to be fixed by the crew. The mission also suffered from a loss of communications for about 90 minutes due to an errant command from Mission Control in Houston (MCC-H). Columbia flew in a gravity gradient mode for most of the flight, which meant that onboard consumables were used at a reduced level. The mission management team determined that there was sufficient electrical power available to extend the mission by a day, which also meant that at landing Columbia had logged sufficient duration to bring the cumulative total flight time across the fleet (Columbia, Challenger, Discovery, Atlantis and Endeavour) to 365 days 23 hours 48 minutes – just over one year in space on 55 missions. The landing of STS-55 was originally set for KSC, but was moved to Edwards due to cloud cover over the Shuttle Landing Facility area at the Cape.

Most of the experiments were provided by the German Space Agency and ESA, with a number being supplied by Japan and three by NASA. The French Space Agency, CNES, was also involved in the mission. This was the final “national” Spacelab mission from Germany, due in part to NASA’s reluctance to reduce the costs of flying such a large payload. Germany (and many other nations) decided that in future they would fly their experiments as part of International Spacelab missions. Despite this, valuable experience and information was gathered from the mission that would have relevance to the Columbus module that was being designed by ESA for the US space station (Freedom) programme.

Milestones

160th manned space flight

85th US manned space flight

55th Shuttle mission

14th flight of Columbia

8th Spacelab Long Module mission

2nd dedicated German Spacelab mission

Accumulated flight time for all Shuttles exceeds 1 year