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Space Shuttle Atlantis
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Space Shuttle Atlantis is one of the three currently operational orbiters in the Space Shuttle fleet of NASA, the space agency of the United States. (The other two are Discovery and Endeavour.) Atlantis was the fourth operational shuttle built.
In early 2008, NASA officials decided to keep Atlantis flying until 2010, the projected end of the Shuttle program.
This reversed a previous decision to retire Atlantis in 2008.
Current statusAtlantis is currently in OPF-1, an Orbiter Processing Facility at Kennedy Space Center, after completion of mission STS-122. Workers are preparing Atlantis for STS-125, the final shuttle mission to the Hubble Space Telescope, which is targeted for launch on 2008-10-08. Rollover from the OPF to the Vehicle Assembly Building is expected to take place on August 22.
HistoryAtlantis made its first flight in October 1985, conducting classified military activities, one of five such flights. In 1989, Atlantis deployed two planetary probes, Magellan and Galileo, and in 1991, it deployed the Compton Gamma Ray Observatory.
Beginning in 1995, Atlantis made seven straight flights to the Russian space station Mir. On the second Mir flight, it delivered a docking module, and on the subsequent flights, it conducted astronaut exchanges.
From November 1997 to July 1999, Atlantis underwent refitting operations, with about 165 modifications made to the shuttle, including the installation of the Multifunction Electronic Display System, or glass cockpit. It has made six flights since then, all involving assembly activities at the International Space Station.
In October 2002, Atlantis and the six-person crew completed an 11-day mission to the International Space Station that involved three space walks.
NASA scheduled the 27th launch for Atlantis for September 2005, during the window of September 9-September 24. It was ruled unsafe to fly the mission and the launch window was missed, due to the complications during Discoverys launch of mission STS-114 and NASA's subsequent suspension of all future shuttle launches. Atlantis was the designated STS-300 rescue orbiter for the STS-114 mission. Atlantis was scheduled to fly the STS-121 mission, but it was decided that Discovery would fly the mission instead.
After a four-year-halt she went back into orbit along with six astronauts on STS-115, carrying the P3/P4 truss segments and solar arrays.
Atlantis launched on her longest mission STS-117, almost 14 days, on 2007-06-08. 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.
NASA had planned to withdraw Atlantis from service in 2008, as she 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:
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.
See also
External links
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