STS-94 (July 1-17, 1997) was a re-flight of the Microgravity Science Laboratory (MSL-1) Spacelab mission, and focused on materials and combustion science research in microgravity. Mission duration was 376 hours and 45 minutes, traveling 6.3 million miles in 251 orbits of the Earth.
The launch of STS-83, the first Microgravity Science Laboratory (MSL-1) mission, was postponed for a day to replace some insulation around a water coolant line in Columbia's payload bay. Liftoff was further delayed 20 minutes due to anomalous oxygen readings in the orbiter's payload bay. STS-83 was cut short due to a problem with one of the three fuel cells that provide electricity and water to Columbia (flight rules required that all three must be operating). At 14:30 GMT on April 6 the crew were ordered to begin a Minimum Duration Flight (MDF). On April 8 the OMS engines ignited at 17:30 GMT for the deorbit burn, and Columbia landed on Runway 33 at Kennedy Space Center at 18:33 GMT.
With delays in International Space Station construction leaving ample room in the shuttle schedule, NASA made the unique decision to leave the equipment installed in Columbia and refly this mission with the same crew later in 1997 as STS-94.
STS-94 was the reflight, with the same equipment and crew, of the curtailed STS-83 mission. Cargo Bay Payloads:
In-Cabin Payloads: SAREX, MSX
The mission this time went for its full two week duration and the crew completed the full list of experiments. The deorbit burn was on July 17, 1997 at 09:44 GMT and Columbia landed on KSC's Runway 33 at 10:46:34 GMT.