Space Shuttle Program

The goal of the Space Shuttle was to reduce the cost of launching a payload into earth orbit and achieving this by employing spacecraft components that could be reused to the greatest extent possible, and high volume use of the vehicle.  The Shuttle (Space Transportation System, STS) is comprised of the Orbiter (i.e., the Shuttle itself), two Solid Rocket Boosters (SRBs), and an External Fuel Tank, which contains the majority of the liquid fuel required to achieve orbit.  Additional fuel for orbital adjustments are carried aboard the Orbiter and burned by the two Orbital Maneuvering System Engines.  With the exception of the External Tank, the Space Shuttle and SRBs are reusable.  The segmented SRBs are parachuted into the ocean and restored, and the Orbiter lands like an airplane when it returns from orbit.  The External Tank is not reusable and is replaced on every flight.  However, lessons learned during operation of the Shuttle have taught us that the price of restoring the vehicle for its next flight is significantly greater than originally planned, and involves more inspections and people than anticipated. 

Had it not been for the Space Shuttle several costly and important satellites would have failed without rescue missions, the most famous of which is the Hubble Telescope.  This orbiting telescope can now see almost as far back in space-time as the origin of the universe, or the Big Bang.  This required the Hubble to be outfitted with some new optics which corrected optical imperfections in the original launch configuration of the Hubble.  There have been additional rescue missions intended to extend the useful life of the Hubble and further enhance performance.  These carefully planned restoration missions were executed with precision accomplishing all their goals, again demonstrating that manned spaceflight is essential for an ambitious space program. 

The concept of the Space Shuttle goes back to the late 1960s and early 1970s. It was approved and publicly announced in 1972, and the earliest tests occurred in 1981. While the program has achieved many of its stated goals, the fleet has been grounded at least three times, twice associated with the loss of human life. The first time a problem was discovered with the O-ring gasket system in the segmented SRB which permitted the hot products of combustion to strike the nearby fuel tank and cause the catastrophic explosion of the Challenger. The second significant problem involved microscopic cracks discovered in the engine system which grounded the fleet until they were fixed. The third was the Columbia disaster, caused by damage inflicted by a massive chunk of insulation breaking away from the tank and striking the leading edge of the port (left) wing during the launch. It was not known just how extensive this damage was, and tragically, the Orbiter was incinerated on reentry.