The Space Shuttle - A Mission Profile

The Space Shuttle - A Mission Profile
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The Space Shuttle is a staged, reusable spacecraft consisting of three components: the Orbiter, the airplane-like vehicle that achieves orbit and returns to land on a runway; the External Tank, which carries the fuel for the Shuttle’s main engines and helped to make the Orbiter technologically feasible; and the Solid Rocket Boosters that provide well over half of the Shuttle’s liftoff thrust of six and a half million pounds. And it needs it - at 4.4 million pounds, the Shuttle is no lightweight!

All Space Shuttle launches begin at launch pad 39A at Kennedy Space Center after some 60 or so days of processing and assembly. From liftoff, the Shuttle accelerates at only .6g (though this ratio dramatically improves as it burns fuel) and takes a little over two minutes to reach SRB (Solid Rocket Booster) separation; at this point, the Shuttle is already traveling at over four times the speed of sound and has reached an altitude of almost 150,000 ft. As the Shuttle sheds mass and reaches the upper layers of the stratosphere, air resistance begins to dwindle allowing it to accelerate much more rapidly. Only four minutes later, it has accelerated to Mach 15 and ascended to over 400,000 ft. From here, only two minutes remain to main engine cut off (MECO) and ET separation. The Orbital Maneuvering System (OMS) engines then fire, placing the Shuttle in a circular orbit traveling at approximately 17,500 miles per hour. Once on orbit, the Shuttle’s cargo bay doors open to expose radiators that shed excess heat and allow payloads to be deployed via their own rocket motors or the RMS (remote manipulator system). If EVA (a spacewalk) is necessary, the astronauts exit through the airlock in the cargo bay.

The trip back down is considerably slower. From deorbit burn (a mere 200 mph change in velocity is enough to start the trip home!) to landing takes about an hour. Thirteen minutes of this time is spent in communications blackout due to the ionization of the air surrounding the vehicle; external air temperatures will peak at 2750 degrees Fahrenheit at the nose and leading edge of the wings. During re-entry, the Shuttle is un-powered and flies a carefully monitored trajectory in order to conserve energy for landing.

Despite all this, the mission is the easy part - a Shuttle will spend a few weeks undergoing maintenance upon its return!