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by amnesiac on June 13th, 2005

amnesiac

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Exactly what is rocket fuel made of, and how much is required per tonne of payload to achieve escape velocity?

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  • by An0nym0us on January 24th, 2006

    An0nym0us

    Liquid propellants used by NASA and in commercial launch vehicles can be classified into three types: petroleum, cryogenics, and hypergolics.

    Solid propellants (two categories): homogeneous and composite. Both types are dense, stable at ordinary temperatures, and easily storable.

    Hybrid propellant engines represent an intermediate group between solid and liquid propellant engines. One of the substances is solid, usually the fuel, while the other, usually the oxidizer, is liquid. The liquid is injected into the solid, whose fuel reservoir also serves as the combustion chamber. The main advantage of such engines is that they have high performance, similar to that of solid propellants, but the combustion can be moderated, stopped, or even restarted. It is difficult to make use of this concept for vary large thrusts, and thus, hybrid propellant engines are rarely built.

    Ref:
    http://en.wikipedia.org/wiki/Rocket_fuel
    http://www-pao.ksc.nasa.gov/kscpao/nasafact/count2.htm
    http://www.braeunig.us/space/propel.htm

    To answer the second question, the amount of fuel used per tonne of payload varies depending on what fuel is used, how it is used, the "specific impulse" (change in momentum per unit of propellant) of the fuel, and what else is in the rocket (rocket motors, tanks, pumps, control mechanism etc) Don't forget that a lot of rockets these days have multiple stages that use different propellents at different altitudes too.

    A quick search found some vehicles with as poor a ratio as 2 percent payload... The fuel weight is usually between 70% to 90% of the total weight.

    This doesn't apply to rockets designed to take off from anywhere but earth. This doesn't apply to model rockets and toys.

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