Spacecraft Propulsion Technology

Currently there are two main types of onboard spacecraft propulsion systems: chemical and electrical. Chemical systems, such as the large launcher rocket engines we discussed in Chapter 5, use the chemical energy obtained by burning a propellant/oxidizer mix. This produces a hot and energetic gas, which is then exhausted through a rocket nozzle to produce thrust. Electrical systems, on the other hand, use electrical power to accelerate the propellant gas out of the rocket nozzle. High exhaust speeds can be obtained in this way, but the amount of mass per second that can be accelerated is generally small, unless a large amount of electrical power is used. As a consequence, the thrust of electrical systems is small (usually small fractions of a Newton). This chapter focuses on the more commonly used chemical propulsion systems. Big chemical rocket engines on spacecraft are either solid propellant systems or liquid bi-propellant systems.

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