STS-51-C

STS-51-C (formerly STS-20) 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 1985. 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.

STS-51-C

Launch of Discovery; in-flight photography of this Department of Defense support mission is limited.
Names	STS-20
Mission type	Satellite deployment
Operator	NASA, Department of Defense
COSPAR ID	1985-010A
SATCAT no.	15496
Mission duration	3 days, 1 hour, 33 minutes, 23 seconds
Distance travelled	2,010,000 km (1,250,000 mi)
Orbits completed	49
Spacecraft properties
Spacecraft	Space Shuttle Discovery
Launch mass	113,802 kg (250,890 lb)
Crew
Crew size	5
Members	Ken Mattingly Loren Shriver Ellison Onizuka James Buchli Gary Payton
Start of mission
Launch date	24 January 1985, 19:50:00 UTC
Launch site	Kennedy, LC-39A
End of mission
Landing date	27 January 1985, 21:23:23 UTC
Landing site	Kennedy, SLF Runway 15
Orbital parameters
Reference system	Geocentric orbit [1]
Regime	Low Earth orbit
Perigee altitude	332 km (206 mi)
Apogee altitude	341 km (212 mi)
Inclination	28.4°
Period	91.3 minutes
STS 51-C mission patch Back row: L-R: Payton, Buchli, Onizuka Front row L-R: Shriver, Mattingly Space Shuttle program

Crew

Position	Astronaut
Commander	Ken Mattingly Third and last spaceflight
Pilot	Loren Shriver First spaceflight
Mission Specialist 1	Ellison Onizuka First spaceflight
Mission Specialist 2	James Buchli First spaceflight
Payload Specialist 1	Gary Payton, MSE Only spaceflight

Backup crew

Position	Astronaut
Payload Specialist 1	Keith Wright, MSE First spaceflight

Crew seating arrangements

Seat [2]	Launch	Landing	Seats 1–4 are on the Flight Deck. Seats 5–7 are on the Middeck.
S1	Mattingly	Mattingly
S2	Shriver	Shriver
S3	Onizuka	Onizuka
S4	Buchli	Buchli
S5	Payton	Payton

Mission summary

STS-51-C launched from Kennedy Space Center (KSC) on 24 January 1985 at 19:50 UTC, and was the first of nine shuttle missions in 1985. 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 thermal protection tiles. STS-51-C marked the 100th human spaceflight to achieve orbit.

The mission's length of three days was shorter than the week or longer of most civilian shuttle flights. It was the first dedicated to the Department of Defense (DoD),[3] 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 (IUS) on the mission's seventh orbit. It is believed that the payload was a Magnum/Orion ELINT satellite into geosynchronous orbit. Other DoD flights STS-33 and STS-38 could have carried similar payloads. Payton stated in 2009 that STS-51-C's payload is "still up there, and still operating".[4] Payton was a USAF Manned Spaceflight Engineer (MSE); the USAF declined a NASA offer to fly another MSE on the mission.[5]

Also, according to Aviation Week, the shuttle initially entered a 204 km (127 mi) x 519 km (322 mi) orbit, at an inclination of 28.45° 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 km (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 21:23 UTC. IMAX footage of the STS-51-C launch was used in the 1985 movie The Dream is Alive.

Mission insignia

The crew insignia for STS Flight 51-C includes the names of its five crewmembers. The STS 51-C mission marked the third trip of the Space Shuttle Discovery into space, which is referenced by the three colored trailing strips behind the orbiter in the United States red, white and blue. It was the first Space Shuttle mission totally dedicated to the Department of Defense, hence the DoD central eagle on the mission patch. The five stars on the upper part of the golden band of the DoD insignia represent the five astronauts. As this mission was classified, the patch includes no further detail as to the mission's payload or nature. For similar reasons, the name of the used orbiter was omitted from the patch.

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.[6]

This information was significant to the established consensus that low air temperature was a major factor in Challenger' 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 12 °C (54 °F).[6]

See also

• List of human spaceflights
• List of Space Shuttle missions

References

1. McDowell, Jonathan. "SATCAT". Jonathan's Space Report. Retrieved 24 March 2014.
2. "STS-51C". Spacefacts. Retrieved 26 February 2014.
3. Blakeslee, Sandra. "Astronauts return from secret" (sic) The New York Times, 8 October 1985.
4. Cassutt, Michael (August 2009). "Secret Space Shuttles". Air & Space. Retrieved 18 April 2015.
5. Cassutt, Michael The Manned Space Flight Engineer Programme Archived 2008-12-30 at the Wayback Machine" Spaceflight January 1989
6. Rogers Commission Report (1986). "Report of the Presidential Commission on the Space Shuttle Challenger Accident, Volume 1, Chapter 6". NASA. This article incorporates text from this source, which is in the public domain.

External links

• NASA mission summary