DESIGN AND HISTORY
The National Aeronautics and Space Administration’s (NASA’s) Space Shuttle Program was designed with the intention of sending the vehicles into low orbit around Earth, during which astronauts are able to conduct experiments; assemble, repair, capture, and release into orbit technological structures, such as the International Space Station (ISS), the Hubble Space Telescope, and satellites; and deliver, install, and retrieve supplies and equipment for the ISS. Throughout most of the process of building the ISS, which began in 1998, astronauts have been living in it (often for several months), having been carried to and from it by the space shuttles.
In 1966, effort toward the development of the space shuttles began. Approval by the government and planning occurred in stages over several years. After several concepts were considered, the design and construction of the space shuttle culminated in ’76 as Enterprise, the test shuttle built not for spaceflight but for observation of its flight ability.
Space shuttles were the first (and are the only) reusable spacecraft. The space shuttles themselves return to Earth and the solid rocket boosters (SRBs) are retrieved after their release during launch; the external tank (ET) is not recovered after its release. The space shuttle is able to launch vertically from Launch Pad 39A or 39B at Kennedy Space Center (KSC) in Florida, fly in orbit, dock to the International Space Station or other structures, and return to KSC (or any of several NASA-approved Landing Site runways around Earth) by landing on wheels released from its underside.
The shuttle system is comprised of the orbiter (or space shuttle), ET, and two SRBs. The orbiter is attached along the ET, and the two SRBs are at the ET’s sides. The space shuttle system is assembled at KSC’s Vehicle Assembly Building in Florida, carried to a launch pad at KSC aside the pad’s Fixed Service Structure, then filled with cargo secured into its payload bay. Astronauts enter the shuttle’s cabin through its door, which is accessible from the Fixed Service Structure.
The orbiter is divided into three fuselage sections: forward, including the crew cabin; mid, including the payload bay; and aft, including the fuel-filled orbital maneuvering system (OMS) pods and the three main engines (space shuttle main engines, or SSMEs). The OMS and SSMEs are relied upon during the shuttle’s return to Earth; this usage during re-entry is referred to as the “deorbit burn.” The SRBs provide the fuel blend for the initial lift during launch and are soon dropped into the ocean when they are no longer needed; they are later retrieved for reuse. Liquid forms of oxygen and hydrogen from the ET pass through to the space shuttle to power its SSMEs. The ET is the source of lift for the remainder of the journey out of Earth’s atmosphere and is released after its fuel has been expended by the SSMEs; the ET cannot be reused because it disintegrates during its fall through the atmosphere and into the ocean. The color of the ET is caused by the rusting metal; the ET had been painted for the first spaceflight (with Columbia), but no others were painted after that mission because of the weight and cost of doing so.
Each space shuttle mission begins its name with “STS” (abbreviated from “Space Transportation System”), which is followed by numbers that distinguish each mission. For most missions, the second part of each name indicates where it is in the sequence of all space shuttle missions — the final mission, STS-135, is the one-hundred-and-thirty-fifth spaceflight for the Space Shuttle Program; the order of some missions had changed without affecting their names. During 1984 through ’86, the tenth through twenty-fifth missions were named differently from this system; after “STS,” the first digit was the fiscal year, the second was the launch site, and the letter was the place in order of missions for the fiscal year.
Initially, before unknown hindering factors emerged, the space shuttles were expected to endure 100 spaceflights each, partially because of their reusability. Since their initial spaceflights, during preparation for their next missions, the shuttles have undergone upgrades to improve their performance and safety. After the final mission, the space shuttles have had 135 spaceflights carrying 355 individuals, many of whom have been crew members for multiple missions. Among the Space Shuttle Program’s 133 successful missions, two were unsuccessful: STS-51L with Challenger in 1986 and STS-107 with Columbia in 2003, together losing fourteen crew members during the shuttles’ destruction.
(Continued in Part 2)
For more about NASA’s missions, visit http://www.nasa.gov or http://contributor.yahoo.com/user/kmmh.