Space Shuttle Challenger

Space Shuttle Challenger (NASA Orbiter Vehicle Designation: OV-099) was NASA's second Space Shuttle orbiter to be put into service, Columbia having been the first. The shuttle was built by Rockwell International's Space Transportation Systems Division in Downey, California. Its maiden flight was on April 4, 1983, and it completed nine missions before breaking apart 73 seconds after the launch of its tenth mission, STS-51-L on January 28, 1986, resulting in the death of all seven crew members. The accident led to a two-and-a-half year grounding of the shuttle fleet, with missions resuming in 1988 with the launch of Space Shuttle Discovery on STS-26. Challenger itself was replaced by the Space Shuttle Endeavour, which first launched in 1992. Endeavour was constructed from spare parts originally meant for Challenger and the other shuttles in the fleet.

History

Challenger was named after HMS Challenger, a British corvette that was the command ship for the Challenger Expedition, a pioneering global marine research expedition undertaken from 1872 through 1876.^[2] The Apollo 17 lunar module that landed on the Moon in 1972 was also named Challenger.^[2]

Construction

Because of the low production of orbiters, the Space Shuttle program decided to build a vehicle as a Structural Test Article, STA-099, that could later be converted to a flight vehicle. In order to prevent damage during structural testing, qualification tests were performed to a factor of safety of 1.2 times the design limit loads. The qualification tests were used to validate computational models, and compliance with the required 1.4 factor of safety was shown by analysis.^[3]

NASA planned to refit the prototype orbiter Enterprise (OV-101), used for flight testing, as the second operational orbiter. However, design changes made during construction of the first orbiter, Columbia (OV-102), would have required extensive rework. Because STA-099's qualification testing prevented damage, NASA found that rebuilding STA-099 as OV-099 would be less expensive than refitting Enterprise.

Challenger (and the orbiters built after it) had fewer tiles in its Thermal Protection System than Columbia. Most of the tiles on the payload bay doors, upper wing surface, and rear fuselage surface were replaced with DuPont white Nomex felt insulation. This modification allowed Challenger to carry 2,500 lb (1,100 kg) more payload than Columbia. The hatch tile pattern was also different from that of the other orbiters. Challenger was also the first orbiter to have a head-up display system for use in the descent phase of a mission.

Flights and modifications

After its first flight in April 1983, Challenger quickly became the workhorse of NASA's Space Shuttle fleet, flying far more missions per year than Columbia. In 1983 and 1984, Challenger flew on 85% of all Space Shuttle missions. Even when the orbiters Discovery and Atlantis joined the fleet, Challenger remained in heavy use with three missions a year from 1983 to 1985. Challenger, along with Discovery, was modified at Kennedy Space Center to be able to carry the Centaur-G upper stage in its payload bay. Had STS-51-L been successful, Challenger's next mission would have been the deployment of the Ulysses probe with the Centaur to study the polar regions of the Sun.

Challenger's many spaceflight accomplishments included the first American woman, African-American, and Canadian in space; three Spacelab missions; and the first night launch and night landing of a Space Shuttle. Challenger was also the first space shuttle to be destroyed in an accident during a mission. The collected debris of the vessel are currently stored in decommissioned missile silos at Cape Canaveral Air Force Station. From time to time, further pieces of debris from the orbiter wash up on the Florida coast.^[4] When this happens, they are collected and transported to the silos for storage. Because of its early loss, Challenger was the only space shuttle that never wore the NASA "meatball" logo, and also was never modified with the MEDS "glass cockpit". The tail was also never fitted with a drag chute – it was fitted to the remaining orbiters in 1992.

Mission insignias

Loss of Challenger

Challenger was destroyed as it broke up in mid-flight in the second minute of its tenth mission, on January 28, 1986, at 11:38:00 am Eastern Standard Time.^[5] The breakup was ultimately due to the failure of an O-ring on its right solid-fuel rocket booster (SRB). The O-rings are used to seal the joints between the multiple segments of the SRBs. The failure was due to a variety of factors, including unusually low temperatures prior to liftoff.^[6] The failure allowed a plume of flame to leak out of the SRB and impinge on both the external fuel tank (ET) and the SRB aft attachment strut. This caused both structural failure of the ET, and pivoting of the SRB into the orbiter and ET. Damage near the bottom of the ET resulted in the complete loss of the aft dome of the lower tank and a rapid release of hydrogen, creating a forward thrust of about 2.8 million pounds and pushing the tank up into the intertank structure which connects the liquid hydrogen tank and liquid oxygen tank. This was followed by an almost explosive burning of the hydrogen combined with oxygen leaking from the intertank. Challenger's reaction control system then ruptured, resulting in the burning of its hypergolic propellants. The orbiter, traveling at about Mach 1.92, was forced into an attitude that caused it to endure extreme aerodynamic loads, with the resulting stresses breaking it apart.^[7] All seven crew members were killed. On March 8, 1986, a search team found the crew cabin; it had not been destroyed in the explosion. The bodies of all seven crew members were found, still strapped into their seats. Autopsies were done but exact cause of death was inconclusive. It is believed that at least some of the crew survived the explosion, since three of four emergency air packs found had been deployed. After the explosion, the crew cabin fell over 50,000 feet and hit the water at approximately 200 miles per hour.

Crew members

• Francis R. Scobee – Mission Commander
• Michael J. Smith – Pilot
• Judith A. Resnik – Mission Specialist 1
• Ellison S. Onizuka – Mission Specialist 2
• Ronald E. McNair – Mission Specialist 3
• Gregory B. Jarvis – Payload Specialist 1
• Christa McAuliffe – Payload Specialist 2

See also

• List of human spaceflights
• List of Space Shuttle crews
• List of Space Shuttle missions
• Timeline of Space Shuttle missions
• List of human spaceflights chronologically
• Challenger flag

References

Further reading

• Evans, Ben (2007). Space shuttle challenger: ten journeys into the unknown. Published in association with Praxis Pub. ISBN 9780387463551. http://books.google.ca/books?id=MQjCF8Cc7HoC&lpg=PR1&dq=Space%20Shuttle%20Challenger%20disaster&pg=PR1#v=onepage&q&f=true 

External links

• Mission Summary Archive
• Ronald Reagan: Address to the Nation on the Explosion of the Space Shuttle Challenger
• Space Shuttle Challenger Explosion video
• Shuttle Orbiter Challenger (OV-99)
• Rogers Commission Report
• Astronautix on Challenger
• Space Shuttle Challenger: A Tribute – slideshow by Life magazine
• Challenger Mission Videos of the Accident from Spaceflightnow.com
• NASA film on the accident and investigation downloadable from archive.org The Internet Archive
• Memorial to Greg Jarvis in Hermosa Beach, California at "Sites of Memory"
• Personal Observations on the Reliability of the Shuttle by R. P. Feynman
• RealPlayer video of Feynman's O-Ring demonstration (low quality)
• CBS Radio news Bulletin Anchored by Christopher Glenn of the Challenger Disaster from January 28, 1986 , Part 2 of CBS Radio coverage of Challenger Disaster , Part 3 of CBS Radio News coverage of Challenger disaster, Part 4 of CBS Radio news coverage of challenger disaster
• Image of silo storing Challenger debris
• Space Shuttle Memorial covering both space shuttle disasters