Ion Drives

Previously, I talked about ions. Remember, they are atoms that have either more or less electrons than protons. For ion drives, positive ions, also called cations, are used to propel the craft ahead.

The ions are created in a chamber where the electrons are stripped from an atom or molecule (many times xenon or ammonia, depending on the thruster type), then are accelerated via an electrostatic or an electromagnetic field.

Ion drives have a very high specific impulse, which means they are very efficient engines. Specific impulse is the ratio between the spacecraft's thrust (the force at which the spacecraft is being pushed along) and the weight of the fuel used to create that thrust).

However, the thrust from an ion engine is small since ions themselves are rather tiny. Ion engines are not great from getting place to place quickly in the solar system. Typically, ion drives will be used for space stations for maneuvering or for deep space probes. Though the thrust is tiny, over time, that thrust can add up to a large velocity for the spacecraft.

Deep Space 1

Via NASA

Schematic of Deep Space 1

via NASA