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Discovery launches on STS-51-C
|Mission type||Satellite deployment|
|Mission duration||3 days, 1 hour, 33 minutes, 23 seconds|
|Distance travelled||2,010,000 kilometres (1,250,000 mi)|
|Spacecraft||Space Shuttle Discovery|
|Launch mass||113,802 kilograms (250,891 lb)|
Gary Payton, MSE
|Start of mission|
|Launch date||24 January 1985, 19:50:00UTC|
|Launch site||Kennedy LC-39A|
|End of mission|
|Landing date||27 January 1985, 21:23:23UTC|
|Landing site||Kennedy SLF Runway 15|
|Perigee||332 kilometres (206 mi)|
|Apogee||341 kilometres (212 mi)|
Back row: L-R: Payton, Buchli, Onizuka
STS-51-C was the 15th flight of NASA's Space Shuttle program, and the third flight of Space Shuttle Discovery. It launched on 24 January 1985, and made the fourth shuttle landing at Kennedy Space Center, Florida, on 27 January. STS-51-C was the first shuttle mission to deploy a dedicated United States Department of Defense (DoD) payload, and consequently many mission details remain classified.
Third and last spaceflight
|Mission Specialist 1||Ellison Onizuka
|Mission Specialist 2||James Buchli
|Payload Specialist 1||Gary Payton, MSE
Backup crew 
|Payload Specialist 1||Keith Wright|
Mission summary 
STS-51-C launched from Kennedy Space Center (KSC) on 24 January 1985 at 14:50 EST, and was the first of nine shuttle missions that year. It was originally scheduled for 23 January 1985, but was delayed because of freezing weather. Challenger had been scheduled for this flight, but Discovery was substituted when problems were encountered with Challenger's thermal protection tiles. STS-51-C marked the 100th human spaceflight to achieve orbit.
The mission was the first shuttle flight dedicated to the Department of Defense (DoD), and most information about it remains classified. For the first time, NASA did not provide pre-launch commentary to the public until nine minutes before liftoff. The Air Force only stated that the shuttle successfully launched its payload with an Inertial Upper Stage on the mission's seventh orbit. It is believed that the payload was an Magnum/ORION ELINT satellite into geosynchronous orbit, and that STS-33 and STS-38 launched others. Payton stated in 2009 that STS-51-C's payload is "still up there, and still operating."
Also according to Aviation Week, the shuttle initially entered a 204-kilometre (127 mi) x 519-kilometre (322 mi) orbit, at an inclination of 28.45 degrees to the equator. It then executed three Orbital Maneuvering System (OMS) burns, the last being executed on the fourth orbit. The first burn was conducted to circularize the shuttle's orbit at 519 kilometres (322 mi).
The mission lasted 3 days, 1 hour, and 33 minutes. Discovery touched down on Runway 15 at KSC on 27 January 1985, at 16:23 EST. IMAX footage of the STS-51-C launch was used in the 1985 movie The Dream is Alive.
Connection to the Challenger disaster 
Almost exactly a year after STS-51-C, Space Shuttle Challenger was destroyed with all hands on board during the STS-51-L mission including Ellison Onizuka, a crew member on both flights. As part of the investigation into the disaster, it was reported to the Rogers Commission that during the launch of STS-51-C, the worst solid rocket booster (SRB) blow-by effects of any mission prior to STS-51-L occurred, indicating conclusively that the Viton O-rings were not sufficiently sealing the hot gases inside the combustion chambers of the SRBs while firing. After they were recovered post-flight, the O-rings in both the right and left SRBs showed some degree of charring, but analysis of the center field joint of the right SRB showed an unprecedented penetration of the primary O-ring and heavy charring on the secondary O-ring.
This information was significant to the established consensus that low air temperature was a major factor in Challenger's destruction because the temperature at STS-51-C's launch was also, up to its time, the coldest recorded during a shuttle launch, at only 53 °F (12 °C).
See also 
- Cassutt, Michael (August 2009). "Secret Space Shuttles". Air & Space. Retrieved 17 February 2012.
- Rogers Commission Report (1986). "Report of the Presidential Commission on the Space Shuttle Challenger Accident, Volume 1, Chapter 6".