The Space Shuttle Orbiter formally started on January 5 1972 by Richard Nixion. The first orbiters were manufactured by Rocwell International and then later by Boeing. The space Shuttle Orbiter was designed to replace the expendable launch vehicles that NASA was using to deliver commercial scientific and applications spacecraft into Earth s orbit. The Orbiter s main engines and boosters combined allows the orbiter to reach orbit. The orbiter comprises of three primary elements the first element a delta-winged orbiter spacecraft having large crew compartment cargo bay and three main engines second is its two solid rocket boosters and the third is an external fuel tank which houses the liquid hydrogen and oxidizer burned in the main engines. The Orbital Maneuvering System (OMS) provides orbital maneuvers which includes insertion circularizattion transfer rendezvous abort to orbit and abort once around. The Reaction Control System (RCS) provides altitude control and translation along the pitch roll and yaw axes during the flight phases of orbit insertion orbit and re-entry. The Thermal Protection System (TPS) covers the outside of the Orbiter for protection against the cold soak of -121 degree Celsius in space to the 1649 degree Celsius heat of re-entry. The Space Shuttle Orbiter s individual fleets are named and numbered similar to ships. All orbiters tend to be externally and identically similar but they have minor internal differences. The Challenger (OV-099) was destroyed after its liftoff in January 28 1986. The Eneterprise (OV-101) was used for test landings. The Columbia which was destroyed during reentry in February 1 2003. And the other orbiters Discovery Atlantis and Endeavor. As of August 21 2007 Columbia and Challenger are no longer in service
