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Space Shuttle Atlantis (Orbiter Vehicle Designation: OV-104) is one of the three currently operational orbiters in the Space Shuttle fleet of NASA, the space agency of the United States.[2] (The other two are Discovery and Endeavour.) Atlantis was the fourth operational shuttle built. "Atlantis" is named after a two-masted sailing ship that operated from 1930 to 1966 for the Woods Hole Oceanographic Institute.[3] In early 2008, NASA officials decided to keep Atlantis flying until 2010, the projected end of the Shuttle program.[4] This reversed a previous decision to retire Atlantis in 2008.[5][6]
[edit] Current statusAtlantis is currently at KSC launch pad 39A where it was being prepared for STS-125, the final shuttle mission to the Hubble Space Telescope.[7] Reports indicate NASA plans to roll Atlantis back to the VAB on October 20, 2008, since the STS-125 mission has been postponed until 2009.[8] [edit] HistoryThe first flight of Atlantis, STS-51-J, took place during October 1985. The mission was one of five flights during which crews conducted classified military activities. Atlantis flew one other mission, STS-61-B, before the Space Shuttle Challenger disaster temporarily grounded the shuttle fleet in 1986. Atlantis was used for ten flights between 1988 and 1992. Two of these, both flown in 1989, deployed planetary probes (Magellan on STS-30 and Galileo on STS-34). Another mission, STS-37 flown in 1991, deployed the Compton Gamma Ray Observatory. Beginning in 1995 with STS-71, Atlantis made seven straight flights to Mir (a Russian space station) as part of the Shuttle-Mir Program. After STS-86, the seventh flight of Atlantis to Mir, the orbiter underwent a series of refitting operations. From November 1997 to July 1999, about 165 modifications were made to Atlantis, including the installation of the Multifunction Electronic Display System, or glass cockpit. In May 2000 Atlantis returned to service for STS-101, a flight to the International Space Station (ISS). The first mission flown by Atlantis after the Space Shuttle Columbia disaster was STS-115, conducted during September 2005. The mission carried the P3/P4 truss segments and solar arrays to the ISS. The longest mission flown using Atlantis -- STS-117 during June 2007 -- lasted almost 14 days. Because Atlantis is not equipped to take advantage of the Station-to-Shuttle Power Transfer System, missions cannot be extended by making use of power provided by ISS.[9] NASA had planned to withdraw Atlantis from service in 2008, as the orbiter would have been due to undergo the scheduled Orbiter Maintenance Down Period (OMDP); this is a major program of refit and maintenance which would have lasted at least a year. Because of the final retirement of the shuttle fleet in 2010, this was deemed uneconomic. It was planned that Atlantis would be kept in near flight condition to be used as a parts hulk for Discovery and Endeavour. However, with the significant planned flight schedule up to 2010, the decision was taken to extend the time between OMDPs, allowing Atlantis to be retained for operations. Atlantis has been swapped for one flight of each of the other orbiters in the flight manifest. As of March 2008, Atlantis is now projected to fly at least three more missions prior to the end of the shuttle program[10]:
[edit] Flights
Atlantis has completed 28 flights, spent 220.40-days in space, completed 3,468 orbits, and flown 89,908,732 nautical miles (166,510,972 km) in total, as of September 2006. Among the five Space Shuttles flown in space, Atlantis has conducted a subsequent mission in the shortest time after the previous mission when it launched in November, 1985, only 50 days after its previous mission.
[edit] Aging
NASA announced that 24 helium and nitrogen gas tanks, named Composite Overwrap Pressure Vessels, in Atlantis are older than their designed lifetime (designed for 10 years, later cleared for another 10 years but in service now for 22 years). NASA said it cannot guarantee any longer that the vessels on Atlantis will not burst or explode under full pressure. Therefore, the vessels will only be at 80 percent pressure as close to the launch countdown as possible, and the launch pad will be cleared of all but essential personnel when pressure is increased to 100 percent. A launch pad explosion could damage parts of the shuttle and even wound or kill ground personnel. An in-flight failure to the vessels could even result in the loss of the orbiter and its crew. Because the original vendor is no longer available, the vessels cannot be rebuilt before 2010, when the shuttles are scheduled to be retired. NASA analyses originally assumed that the vessels would leak before they burst, but new tests showed that they would burst before they leak. The new launch procedure, of clearing the launch pad of all but the essential personnel and pressurizing the tanks to 100 percent as late as possible, will now be conducted during the remaining Atlantis launches if no other resolution is found. Atlantis will have to fly at least one more time in this setting. It is unclear, but possible, that Discovery, which will launch another five or six times, has the same problems and if the same launch procedure needs to be conducted with Discovery. Since Endeavour, which will launch another six or seven times, was built much later, around 1990, it is possible that Endeavour does not have the same problem.[12] [edit] See also
[edit] References
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