Ion Thrusters
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An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by the acceleration of ions. Ion thrusters can be characterized by how they accelerate the ions, with either electrostatic or electromagnetic forces being used. Electrostatic ion thrusters use the Coulomb Force and accelerate the ions in the direction of the electric field. Electromagnetic ion thrusters use the Lorentz Force to accelerate the ions. Note that the term “ion thruster” frequently denotes the electrostatic or gridded ion thrusters only.
The thrust created in ion thrusters is very small compared to conventional chemical rockets, but a very high specific impulse, or propellant efficiency, is obtained.
Due to their relatively high power needs, given the specific power of power supplies, and the requirement of an environment void of other ionized particles, ion thrusters are currently only practical for in-space propulsion applications.
The principles of ion thrusters go back to the concepts developed by the German/Austrian physicist Hermann Oberth which were published in his famous 1929 work “Wege zur Raumschiffahrt” (Ways to Spaceflight). A whole chapter was devoted to power and electric propulsion. There he explained his thoughts on the mass savings of electric propulsion, predicted its use in spacecraft propulsion and attitude control, and advocated electrostatic acceleration of charged gases.
The first working ion thruster was built by Harold R. Kaufman in 1959 at the NASA Glenn facilities. It was similar to the general design of a gridded electrostatic ion thruster with mercury as its fuel. Suborbital tests of the engine followed during the 1960s and in 1964 the engine was sent into a suborbital flight aboard the Space Electric Rocket Test 1 (SERT 1). It successfully operated for the planned 31 minutes before falling back to Earth.