A space shuttle is a reusable space vehicle which was developed by NASA (the National Aeronautics and Space Administration) in the United States. At the end of the “space race” of the sixties, space travel had become very expensive. In order to keep the space program going, in January of 1972, President Nixon issued a presidential decree supporting the reusable space vehicle (space shuttle) program.
After years of research and testing, four shuttles were built (Columbia, Discovery, Atlantis and Challenger). The first successful space shuttle flight was in 1981 with the space shuttle Columbia.
The space shuttle system is made of four primary elements: an orbiter, two solid rocket boosters, an external tank and three space shuttle main engines.
The shuttle is launched in an upright position. It uses the two solid rocket boosters and the three space shuttle main engines to get off the ground. In about two minutes after the launch, the solid rocket boosters fall off of the external tank into the ocean where they are recovered and reused by NASA. The space shuttle main engines shut down just before the shuttle enters orbit (about eight minutes after the solid rocket boosters detach or ten minutes after the launch). Then the external tank drops from the orbiter and falls into the ocean, but it is not recovered.
The remaining forty-four smaller Reaction Control System (RCS) engines are used to move the orbiter away from the external tank after separation, and to hold the craft stable until the firing of the Orbital Maneuvering System (OMS) engines. These engines place the shuttle into orbit. Once the shuttle is in orbit, the RCS engines are used to make attitude pitch, roll and yaw maneuvers. The OMS engines are also used for major velocity moves while the shuttle is in orbit as well as for the one thrusting sequence used for deorbit.
The orbiter spacecraft (shuttle) is an airspace plane, and it includes a delta wing, a space section fuselage and a single tail. It also includes a crew compartment (where the crew lives and works), a cargo bay, a movable airlock (that is used for space walks) and a remote manipulator arm (that is used to move heavy equipment in and out of the cargo bay). The orbiter can carry a crew of eight people and a crew of ten in emergency conditions.
An average mission is 7-14 days in space. On every mission, the crew has an objective that they have to accomplish. Some missions are different from others. For example, sometimes the crew has to deploy or retrieve satellites from the cargo bay using the Remote Manipulator System. The crew also conducts experiments in the areas of microgravity science, life science, space science, earth science, engineering research and more. On some missions the space shuttle is used to help build the International Space Station by attaching pre-built modules to it in space. Some missions require the crew to go on space walks outside of the shuttle that involve putting on a space suit and going through depressurization procedures in the airlock.
Before re-entry, the crew must close the cargo bay doors, turn the orbiter tail first by firing the RCS thrusters, slow the orbiter down by firing the OMS engines, and then fall back to earth. In the twenty-five minutes or so it takes the shuttle to reach the upper atmosphere, the crew uses the RCS thrusters to pitch the orbiter over so it's nose first with the bottom facing the atmosphere. Then, as a safety precaution, the crew burns any fuel from the forward RCS engines. At this point the shuttle is moving at about 17,000 mph or 28,000 km/h. Heat will build up to approximately 3,000 degrees F, or 1,650 degrees C because of friction with air molecules. To keep it from disintegrating during re-entry, the shuttle has a thermal shield to protect it. After the orbiter re-enters the main atmosphere, it is able to fly and land like an airplane. On the runway, a parachute is deployed to help stop the orbiter.
There have been some tragic moments in the history of the space shuttle program. In 1986, the Challenger exploded during its launch because a flame from a leaky joint on one of the rocket boosters ignited the fuel in the external tank. The entire crew was lost. Several years later, after the disaster’s investigation, the problem was corrected, and the shuttle flights began again. A new shuttle, the Endeavor, was built to replace the Challenger. In February of 2003, the shuttle Columbia broke up in flames minutes before it was to land in Florida. The entire crew of the Columbia was also lost. It is believed that a heat shield on one of the wings was the cause of the problem.
The space shuttles have flown about one-fourth of their expected missions (each was designed to fly one hundred missions). Over the years space shuttles are getting more advanced. NASA is currently researching the idea of space shuttles that are all one piece and totally recoverable. Examples of these are the X-33 and VentureStar designs.
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All photographs and drawing are from NASA and have been released into the public domain under the terms of the GNU Free Documentation License from Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/wiki/Main_Page>.
Copyrighted animated image of space shuttle in upper left corner of page from "Microsoft Office Online" <http://office.microsoft.com/clipart/default.aspx?lc=en-us&cag=1> (October-March, 2004-2005). Clip art available only to licensed users for non-commercial purposes.