Launch Information Launch originally scheduled for March 9, but during processing work at Pad A, significant cracks found on all four lug hinges on the two external tank umbilical door drive mechanisms. NASA managers opted to roll back the vehicle to the VAB on March 7, and then to OPF for repair. Hinges replaced with units taken from orbiter Columbia, and reinforced. Discovery returned to pad on April 1, and launch re-set for April 23. Mission again postponed when, during prelaunch external tank loading, a transducer on high-pressure oxidizer turbo-pump for main engine number three showed readings out of specification. Transducer and its cable harness were replaced and tested. Launch was rescheduled for April 28. Landing Information Runway 15, Kennedy Space Center, Fla. Rollout distance: 9,235 feet. Rollout time: 56 seconds. Mission duration: eight days, seven hours, 22 minutes, 23 seconds. Landing diverted to KSC because of unacceptably high winds at planned landing site, Edwards. Landed revolution 134. Mission Highlights Dedicated Department of Defense mission. Unclassified payload included Air Force Program-675 (AFP-675); Infrared Background Signature Survey (IBSS) with Critical Ionization Velocity (CIV), Chemical Release Observation (CRO) and Shuttle Pallet Satellite-II (SPAS-II) experiments; and Space Test Payload-1 (STP-1). Classified payload consisted of Multi-Purpose Release Canister (MPEC). Also on board was Radiation Monitoring Equipment III (RME III) and Cloud Logic to Optimize Use of Defense Systems-1A (CLOUDS-1).
Launch Date: April 28, 1991, 7:33:14 a.m. EDT Launch Vehicle: Discovery Crew: Michael L. Coats (3), CommanderMichael L. Coats, Jr.(1), Pilot Guion S. Bluford Jr.(3), Mission Specialist 1 Gregory J. Harbaugh (1), Mission Specialist 2 Richard J. Hieb (1), Mission Specialist 3 Donald R. McMonagle (1), Mission Specialist 4 Charles L. Veach (1), Mission Specialist 5