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Space Shuttle Transoceanic Abort Landing (TAL) Sites

Space Shuttle TAL Sites

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Planning for each space shuttle mission includes provisions for an unscheduled landing at contingency landing sites in the U.S. and overseas. Several unscheduled landing scenarios are possible, ranging from adverse weather conditions at the primary and secondary landing sites to mechanical problems during the ascent and mission phases that would require emergency return of the orbiter and its crew. The Transoceanic Abort Landing (TAL) is one mode of unscheduled landing. The orbiter would have to make an unscheduled landing if one or more of its three main engines failed during ascent into orbit, or if a failure of a major orbiter system, such as the cooling or cabin pressurization systems, precluded satisfactory continuation of the mission.

Several unscheduled landing scenarios are possible with abort modes available that include: Return to Launch Site (RTLS); East Coast Abort Landing (ECAL) Site; Transoceanic Abort Landing (TAL); Abort Once Around (AOA); and Abort to Orbit (ATO). The abort mode would depend on when in the ascent phase an abort became necessary.

The TAL abort mode was developed to improve the options available if failure occurred after the last opportunity for a safe Return To Launch Site (RTLS) or East Coast Abort Landing (ECAL), but before the Abort Once Around (AOA) option became available. A TAL would be declared between roughly T+2:30 minutes (liftoff plus 2 minutes, 30 seconds) and Main Engine Cutoff (MECO), about T+8:30 minutes, with the exact time depending on the payload and mission profile.

Launch Site - Cape Canaveral TAL Site - Gambia TAL Site - Morocco Two TAL Sites - Spain Four TAL SitesA TAL would be made at one of three designated sites, one in France and two in Spain: Istres Air Base, France; Zaragoza Air Base, Spain; or Moron Air Base, Spain.

Each TAL site is covered by a separate international agreement. TAL sites are referred to as augmented sites because they are equipped with shuttle-unique landing aids and are staffed with NASA, contractor and Department of Defense personnel during every launch.

Space shuttles are launched eastward over the Atlantic Ocean from Kennedy Space Center in Florida for insertion into equatorial orbits. Depending on mission requirements, an orbiter follows an orbital insertion inclination between 28.5 degrees (low) and 57.0 degrees (high) to the equator. All space shuttle launches to the International Space Station use an inclination of 51.6 degrees. The lower inclination launches allowed for a higher maximum payload weight but are no longer used.

High or low inclination launches require different contingency landing sites, with landing sites staffed to ensure there is acceptable weather for a safe landing at a TAL site.

During a TAL abort, the orbiter continues on a trajectory across the Atlantic to a predetermined runway at one of the TAL sites. The sites NASA has designated as TAL sites have been chosen in part because they are near the nominal ascent ground track of the orbiter, which would allow the most efficient use of main engine propellant and cross-range steering capability.

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