24-01-2013, 04:53 PM
Space Shuttles and its Advancements
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INTRODUCTION
The successful explortion of space requires a system that will reliably transport payloads into space and return back to earth; without subjecting them an uncomfortable or hazardous environment. In other words, the space crafts and its pay loads have to be recovered safely into the earth. The space shuttle used at older times were not re-usable. So NASA invented re-usable space shuttle that could launch like a rocket but deliver and land like an aeroplane. Now NASA is planning to launch a series of air-breathing planes that would replace the space shuttle.
A BRIEF HISTORY OF THE SPACE SHUTTLE
Near the end of the Apollo space program, NASA officials were looking at the future of the American space program. At that time, the rockets used to place astronauts and equipment in outer space was one-shot disposable rockets. What they needed was a reliable, but less expensive, rocket, perhaps one that was reusable. The idea of a reusable "space shuttle" that could launch like a rocket but deliver and land like an airplane was appealing and would be a great technical achievement.
External fuel tank
As mentioned above, the fuel for the main engines is stored in the ET. The ET is 158 ft (48 m) long and has a diameter of 27.6 ft (8.4 m). When empty, the ET weighs 66,000 lb (30,000 kg). It holds about 1.6 million lb (719,000 kg) of propellant with a total volume of about 526,000 gallons (2 million liters).
Orbital maneuvering systems
The two orbital maneuvering systems' (OMS) engines are located in pods on the aft section of the orbiter, one on either side of the tail. These engines are used to place the shuttle into final orbit, to change the shuttle's position from one orbit to another, and to slow the shuttle down for re-entry.
SPACE PLANES AND REPLACEMENT OF SPACE SHUTTLE
To replace the space shuttle NASA is planning to launch a series of space planes that named as X series planes. Some X series planes are given below
• The X-37, which will test many space plane technologies, including re-entry capabilities.
• The X-34, a sub orbital vehicle that will test technologies to reduce cost, time and personnel for space launches.
• The X-33, a reusable launch vehicle (RLV) that is a prototype for a space shuttle replacement.
In this the third one that is X-33 is the one that will replace the space shuttle in the future. Despite the shuttle's many accomplishments, the fact remains that it is extremely expensive to launch into space. Each pound of payload in the shuttle's bay costs $10,000 to launch. According to NASA, each of the space shuttle's two solid rocket boosters carries about 1 million pounds (453,592 kg) of solid propellant. The large external tanks hold another 500,000 gallons of super cold liquid oxygen and liquid hydrogen. These two liquids are mixed and burned to form the fuel for the shuttle's three main rocket engines. The cost of this huge amount of propellant, and of recovering and replacing the solid rocket boosters for every mission is extremely expensive. NASA's solution to the problem is the X-33.