STS-51

Flight Crew

CULBERTSON Jr., Frank Lee, 44, USN, commander, 2nd mission Previous mission: STS-38 (1990)

READDY, William Francis, civilian, pilot, 2nd mission Previous mission: STS-42 (1992)

NEWMAN, James Hansen, 36, civilian, mission specialist 1 BURSCH, Daniel Wheeler, 36, USN, mission specialist 2 WALZ, Carl Erwin, 38, USAF, mission specialist 3

Flight Log

The original launch attempt on 17 July was scrubbed during the T — 20 minute hold due to premature and unexplained charging of pyrotechnic initiator controllers on the LH vent arm umbilical and the SRB hold-down bolts. The problem was traced to a faulty control card on the Mobile Launch Platform (MLP). After an abbreviated countdown which commenced on 23 July, the 24 July launch attempt was halted at T — 19 seconds due to problems with the APU turbine assembly in one of the two hydraulic power units on the right SRB. The APUs were replaced on the pad. The launch was rescheduled for 4 August and again for 12 August because of concerns over the Perseid meteor shower which was due to peak on 11 August. The 12 August attempt was aborted at the T — 3 second mark due to a faulty sensor which was monitoring fuel flow on SSME #2. This resulted in the fourth pad abort in the programme and the second of 1993. All three engines were subsequently changed out on the pad. The launch was then scheduled for 10 September, but following loss of

communications with the Mars Observer spacecraft and the NOAA-123 satellite, NASA slipped the launch 48 hours in order to review the design, production and testing of ACTS prior to committing it to launch and deployment.

The ACTS was successfully deployed during FD 1 and, some 45 minutes after leaving the payload bay of Discovery, the TOS was fired to take the satellite towards its geostationary operational orbit. The second deployment of the mission came on FD 2, when ORFEUS-SPAS was released by RMS for six days of independent data collection, the first of a planned series of ASTRO-SPAS missions. The SPAS also carried the IMAX camera, which recorded spectacular images of Discovery flying in orbit both during release and recapture of the pallet satellite.

As ACTS was being checked out in its geosynchronous orbit and ORFEUS was away gathering data, the crew of Discovery settled down to their own science programme of payload bay and mid-deck experiments. These included the exposure to space of selected materials for a short duration, protein crystal growth, chromo­some and plant cell division, high-resolution Shuttle glow spectrograph photography of the aurora, an investigation into polymer membranes processing, further calibra­tion of the Air Force Maui Optical Site and radiation monitoring inside the crew compartment. The crew also continued the programme of Earth resources and phenomena observations.

On FD 5 (16 Sep), Walz (EV1) and Newman (EV2) performed the third and final generic EVA (7 hours 5 minutes) to evaluate tools, tethers, foot restraints and mobil­ity. Part of this programme was connected to the forthcoming Hubble Service Mission manifested for STS-61. This time the RMS was not used to support the EVA, because it was needed later in the flight to retrieve ORFEUS-SPAS. This also provided a “minimum equipment scenario”, with the crew making optimum use of materials already aboard for other purposes. This could prove essential for a mission requiring EVA where no RMS was available.

The landing of STS-51 on 21 September was called off due to the possibility of rain showers within 48 km of the SLF. Discovery eventually came home to the first end-of – mission night landing at the Cape.

Milestones

163rd manned space flight

87th US manned space flight

57th Shuttle mission

17th flight of Discovery

28th US and 52nd flight with EVA operations

1st use of Transfer Orbit Stage

1st end of mission night landing at KSC

3rd and final test and demonstration EVA