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What is space shuttle?
A Space Transportation System (STS) or space shuttle is a manned launched vehicle. The main components of STS are an external tank, two solid rocket boosters and a winged orbitor.
The orbiter carries astronauts and payload into low earth orbit. Most often the orbiter itself is referred to as the the space shuttle, which is technically a misnomer. The shuttle is the first orbital spacecraft designed for partial reusability. The space shuttle will retire by 2010 and Orion, a new vehicle that is designed to take humans to the Moon and beyond, will replace it.
What was the need to make reusable spacecraft?
The main concept behind Nasa’s Space Shuttle Programme was to increase the viability of the space trip. The shuttle was designed to meet the challenge of exploration as well as to do many other jobs at a reduced cost. It was also proposed that an STS would help in routine utilization of space. However, all these claims were later criticized, given the fact that per-pound launch cost are not appreciably cheaper, as well as the years of interruption s in launches following shuttle failures.
How does the shuttle works?
The shuttle takes off like a rocket, operates in orbit as a spacecraft, and lands like a airplane. After the first two minutes of flight, the two solid fuel boosters are cut loose from the tank. The spent boosters eject parachutes and fall down about 280 km from the launch site, from the are collected for reuse.
After some time , the external tank is also cast off. It is however not suitable for reuse. Free from the tank and booster, the orbiter fires its manoeuvring engines and consequently, reshapes the egg-shaped flight path to a circular orbit. Now the shuttle is ready for work.
Coming back to earth is most critical and demanding part of the shuttle voyage. The orbiter has to change from spacecraft to an aircraft. The most difficult part is controlling the shuttle at middle speeds and altitudes, during the re-entry into the atmosphere, air friction heats up the orbiter, apart from the fact the ionization in the surrounding atmosphere blacks out communication with the ground for some time.
At an altitude of about 93 km, the air becomes dense enough so that aerodyanamic controls take hold, and the orbiter becomes a heavy glider.
Without fuel for its main engines, the craft wouldn’t be able to go around for a second landing approach in case of a miscalculation, as an airliner could, hence, it becomes very important to have clear landing conditions and a comparatively large runway.
What Is the importance of the heat shield , in the re-entry of any spacecraft?
When a manned space vehicle reenters the earth’s atmosphere, air friction can produce external surface temperatures as high as 3000 degrees Fahrenheit – well about the melting point of steel. Special thermal barriers are required to protect the vehicle and its occupants. The earlier space capsules were protected during reentry by shedding layers of heavy, resinous heat shield through a process called ablation.
With a design life of about 100 missions, the shuttle requires a light weight, reusable thermal protection, approximately 24,300 tiles and 2,300 flexible insulation blankets are pasted on the outside of the orbiter. The pasting is a complicated system as no two tiles on an orbiter are exactly alike. The tiles are delicate and have to be protected from stresses. The Columbia disaster took place when the debris of a piece of insulated foam damaged one of these tiles.
How is the nomenclature of space shuttle done?
Space shuttles are named after pioneering sea vessels. Atlantis is named for the research vessel that was the first to use electronic sounding devices to map the ocean floor. Challenger was named for the sloop captained by Robert Gray who explored British Columbia.
Discovery is named for one for the two ships used by the British explorer Captain James Cook. The other of Cook’s ships is the namesake for the shuttle Endeavour. Enterprise, the first space shuttle Orbiter, was originally to be named constitution. However, viewers of the TV science fiction show ‘STAR TREK’ started a writein campaign urging the white house to rename the vehicle Enterprise.
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