SPACE SHUTTLE FUEL
At liftoff, propellant accounts for nearly 90 percent of the weight of the Space Shuttle System. Both solid and liquid propellants are used. The external tank carries liquid hydrogen and, separately, the liquid oxygen needed for combustion. About 470 kg of propellant are delivered to each of the three main engines every second. The solid fuel is in the boosters on either side of the orbiter. Each booster weighs 83 tones, and can hold 504 tones of propellant.
SOLID ROCKET FUEL
The propellant in solid – fuel rockets is shaped into pellets that contain both oxidant and fuel. The pellets also contain substances to prevent them decomposing in storage. The way the propellant is packed into the casing determines how the energy is released. If it is packed so that the surface burns at a constant rate (neutral burn), it provides an even thrust. If the pellets are packed so that the surface area where burning occurs increases gradually, thrust increases gradually (progressive burn). If the burning surface area decreases, the thrust decreases gradually (regressive burn).
LIQUID ROCKET FUEL
The boiling point of liquid oxygen is -183degree Celsius, cold enough to crack metal or shatter rubber. Liquid hydrogen boils at -253degree Celsius. Such low temperatures make both difficult to handle, but they make an efficient propellant.
SPECIFIC IMPULSE
The efficiency of a propellant, known as specific impulse, is defined as the time for which 1 kg of propellant can deliver 1 kg of thrust. So, 1 kg of propellant with a specific impulse of 262 seconds, such as that in the Space shuttle’s solid rocket boosters, can produce 1 kg of thrust for 262 seconds. The higher the specific impulse, the more effective the mix. Liquid propellants have higher specific impulses than solid fuels have.
At liftoff, propellant accounts for nearly 90 percent of the weight of the Space Shuttle System. Both solid and liquid propellants are used. The external tank carries liquid hydrogen and, separately, the liquid oxygen needed for combustion. About 470 kg of propellant are delivered to each of the three main engines every second. The solid fuel is in the boosters on either side of the orbiter. Each booster weighs 83 tones, and can hold 504 tones of propellant.
SOLID ROCKET FUEL
The propellant in solid – fuel rockets is shaped into pellets that contain both oxidant and fuel. The pellets also contain substances to prevent them decomposing in storage. The way the propellant is packed into the casing determines how the energy is released. If it is packed so that the surface burns at a constant rate (neutral burn), it provides an even thrust. If the pellets are packed so that the surface area where burning occurs increases gradually, thrust increases gradually (progressive burn). If the burning surface area decreases, the thrust decreases gradually (regressive burn).
LIQUID ROCKET FUEL
The boiling point of liquid oxygen is -183degree Celsius, cold enough to crack metal or shatter rubber. Liquid hydrogen boils at -253degree Celsius. Such low temperatures make both difficult to handle, but they make an efficient propellant.
SPECIFIC IMPULSE
The efficiency of a propellant, known as specific impulse, is defined as the time for which 1 kg of propellant can deliver 1 kg of thrust. So, 1 kg of propellant with a specific impulse of 262 seconds, such as that in the Space shuttle’s solid rocket boosters, can produce 1 kg of thrust for 262 seconds. The higher the specific impulse, the more effective the mix. Liquid propellants have higher specific impulses than solid fuels have.
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