SSME #3 was shipped to the Stennis Space Center in Mississippi for test stand firing over the Labor day weekend (September 5, 1994). Three flight certified SSMEs (removed from the Atlantis STS-66 mission) were installed on the orbiter and Endeavour was rolled back to the launch pad on September 13, 1994. Afterwards, Endeavour's SSMEs were removed and inspected.

A rollback of Endeavour to the VAB was done on August 24, 1994.

The procedure that has been used on previous aborts treats an RSLS abort after SSME ignition as a launch and to require a complete engine reinspection. Ī new launch date was set for early October and then moved up to late September. This was the first flight for the HPOT on Main Engine (SSME) #3. Main Engine #3 (SN 2032) has been used on two previous flights with 2,412 seconds (40 min) of hot-fire time and a total of eight starts. This limit increases to 980 K at T−1.3 s (5.3 s after Main Engine Start). The redline limit to initiate a shutdown is at 867 K. The B channel indicated a redline condition while the other was near redline conditions. There are 2 sensor channels measuring temperature on the HPOT. The HPOT typically operates at 28,120 rpm and boosts the liquid oxygen pressure from 422 to 4,300 psi (2.91 to 29.6 MPa). The automatic abort was initiated by the onboard General Purpose Computers (GPC) when the discharge temperature on MPS Main Engine #3 High Pressure Oxidizer Turbopump (HPOT) exceeded its redline value. Previous aborts occurred on STS-41-D, STS-51-F, STS-55 and STS-51. The launch was originally scheduled August 18, 1994, but there was an RSLS abort at T-1.9 s after all three main engines ignited – the fifth (and final) time in the shuttle program where an RSLS abort occurred after main engine ignition. OMS-2 burn was 1 min 42 s (164 ft/s or 50 m/s) at MET 33 min. Main Engine Cutoff (MECO) was at an apogee of 115 nautical miles (213 km 132 mi) and a perigee of 28 nmi (52 km 32 mi) at MET of 8 min 35 s with Endeavour traveling at 25,779 ft/s (7,857 m/s). Payload liftoff mass 12,511 kilograms (27,582 lb). Orbiter mass at liftoff was 247,129 pounds (112,096 kg) including payload. The Launch window opened at 7:16 am EDT with a 2-hour-30-minute window. Launch September 30, 1994, at 7:16:00.068 am EDT from Kennedy Space Center Launch Pad 39-A. STS-68 was a human spaceflight mission using Space Shuttle Endeavour that launched from Kennedy Space Center, Florida on September 30, 1994.

1992 space shuttle endeavor crew