Columbia (OV-102), the first of NASA's orbiter fleet, was delivered to Kennedy Space Center in March 1979. Columbia initiated the Space Shuttle flight program when it lifted off Pad A in the Launch Complex 39 area at KSC on April 12, 1981. It proved the operational concept of a winged, reusable spaceship by successfully completing the Orbital Flight Test Program - missions STS-1 through 4.
Other, more recent achievements for Columbia include the recovery of the Long Duration Exposure Facility (LDEF) satellite from orbit during mission STS-32 in January 1990 and the STS-40 Spacelab Life Sciences mission in June 1991 - the first manned Spacelab mission totally dedicated to human medical research.
Columbia is named after a small sailing vessel that operated out of Boston in 1792 and explored the mouth of the Columbia River. One of the first ships of the U.S. Navy to circumnavigate the globe was named Columbia. The command module for the Apollo 11 lunar mission was also named Columbia.
Discovery (OV-103), the third of NASA's fleet of reusable, winged spaceships, arrived at Kennedy Space Center in November 1983. It was launched on its first mission, flight 41-D, on August 30, 1984. It carried aloft three communications satellites for deployment by its astronaut crew.
Other Discovery milestones include the deployment of the Hubble Space Telescope on mission STS-31 in April 1990, the launching of the Ulysses spacecraft to explore the Sun's polar regions on mission STS-41 in October of that year and the deployment of the Upper Atmosphere Research Satellite (UARS) in September 1991.
Discovery is named for two famous sailing ships; one sailed by Henry Hudson in 1610-11 to search for a northwest passage between the Atlantic and Pacific Oceans, and the other by James Cook on a voyage during which he discovered the Hawaiian Islands.
Atlantis (OV-104) was delivered to Kennedy Space Center in April 1985. It lifted off on its maiden voyage on Oct. 3, 1985, on mission 51-J, the second dedicated Department of Defense flight. Later missions included the launch of the Galileo interplanetary probe to Jupiter on STS-34 in October 1989, and STS-37, with the Gamma Ray Observatory (GRO) as its primary payload, in April 1991.
Atlantis is named after a two-masted sailing ship that was operated for the Woods Hole Oceanographic Institute from 1930 to 1966.
Authorization to construct the fifth Space Shuttle orbiter as a replacement for Challenger was granted by Congress on August 1, 1987. Endeavour (OV-105) first arrived at KSC's Shuttle Landing Facility May 7,1991, atop NASA's new Shuttle Carrier Aircraft (NASA 911). The space agency's newest orbiter began flight operations in 1992.
Endeavour is named after the first ship commanded by 18th century British explorer James Cook. On its maiden voyage in 1788, Cook sailed into the South Pacific and around Tahiti to observe the passage of Venus between the Earth and the Sun. During another leg of the journey, Cook discovered New Zealand, surveyed Australia and navigated the Great Barrier Reef.
Endeavour features new hardware designed to improve and expand orbiter capabilities. Most of this equipment will be incorporated into the other three orbiters during out-of- service major inspection and modification programs. Endeavour's upgrades include:
*the plumbing and electrical connections needed for Extended Duration Orbiter (EDO) modifications to allow up to 28-day missions.
*updated avionics systems that include advanced general purpose computers, improved inertial measurement units and tactical air navigation systems, enhanced master events controllers and multiplexer-demultiplexers, a solid-state star tracker and improved nose wheel steering mechanisms.
*an improved version of the Auxiliary Power Units (APUs) that provide power to operate the Shuttle's hydraulic systems.
Columbia, the first on-line orbiter to undergo the scheduled inspection and retrofit program, was transported Aug. 10, 1991, after its completion of mission STS-40, to prime Shuttle contractor Rockwell International's Palmdale, Calif., assembly plant, where the work was performed. The oldest orbiter in the fleet underwent approximately 50 modifications, including the addition of carbon brakes, drag chute, improved nose wheel steering, removal of development flight instrumentation and an enhancement of its thermal protection system. The orbiter returned to KSC February 9, 1992 to begin processing for mission STS-50 in June of that year.
Columbia's EDO changes will allow it to support up to a 16- day mission. The upgrades that make a longer stay in space possible include the EDO pallet which holds a set of liquid hydrogen and liquid oxygen tanks to provide additional fuel for the orbiter's electrical power generation system, a regenerating system for removing carbon dioxide from the crew cabin atmosphere, two additional nitrogen tanks for cabin air, an improved waste collection system and additional middeck lockers for storage.
Current plans are for Atlantis and Discovery to undergo the retrofit program within the next two years.
Many other modifications were made to the orbiter fleet before Discovery's Return to Flight mission, STS-26, in September 1988, including improvements to the main engines, thermal protection system and propellant supply systems, and installation of a new crew escape system.
Main engine modifications included changes to the high- pressure turbomachinery, hydraulic actuators and main combustion chamber.
Some of the tiles that make up the orbiter thermal protection system were replaced to make the system lighter, stronger and more durable. Also, a reinforced carbon-carbon panel was added to the orbiter chin between the nose cap and the nose wheel well door to provide improved insulation against the searing heat experienced during reentry into the Earth's atmosphere.
Improvements to the orbiter propellant supply system included a redesigned 17-inch quick disconnect valve between the orbiter and the external tank. Additional modifications were made to the propellant systems of the orbiter reaction control system, orbital maneuvering system and the auxiliary power units.
A new crew escape system was added that allows the Space Shuttle crew to bail out if the orbiter has to make an emergency return descent and a safe runway cannot be reached. This system consists of an escape pole that can be extended from the opened crew hatch. The crew would then fasten a lanyard hook assembly that is a part of the pole to their parachute harnesses. Once attached to this hook, the crew would slide down the deployed pole, away from the orbiter. Once free of the pole, they would parachute to safety.
Any problems that may have occurred with orbiter systems and equipment on the previous mission are checked out and corrected. Equipment is repaired or replaced and extensively tested. Any modifications to the orbiter that are required for the next mission are also made in the OPF.
Orbiter refurbishment operations and processing for the next mission also begin in the OPF. Large horizontal payloads, such as Spacelab, are installed in the orbiter cargo bay. Vertical payloads are installed at the launch pad.
Following extensive testing and verification of all electrical and mechanical interfaces, the orbiter is transferred to the nearby Vehicle Assembly Building where it is mated to the external tank with attached solid rocket boosters. Then, the assembled Space Shuttle vehicle is carried to the launch pad by a large tracked vehicle called the crawler-transporter.
At the launch pad, final preflight and interface checks of the orbiter, its payloads and associated ground support equipment are conducted. After a positive Flight Readiness Review, the decision to launch is made and the final countdown begins.