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The Question

(Submitted September 27, 1998)

I was rather interested in the new type of propulsion mentioned on television. Please e-mail me about the subject.

The Answer

Hello!

Thank you for writing to "Ask an Astrophysicist." It is great that you are interested in astronomy and in space travel; the technology you are probably referring to is an "ion thruster." From a web page on a course in Plasma and Electric Thrusters given at the University of Wisconsin comes this definition of Electrostatic or Ion Thrusters:

This class has a single member, the ion thruster. Its key principle is that a voltage difference between two conductors sets up an electrostatic potential difference that can accelerate ions to produce thrust. The ions must, of course, be neutralized--often by electrons emitted from a hot filament. The three main stages of an ion-thruster design are ion production, acceleration, and neutralization.
(http://elvis.neep.wisc.edu/~jfs/neep602.lecture30.plasmaProp.96/neep602.lecture30.plasmaProp.96.html
This page appears to have disappeared.)

An ion thruster is being used by Deep Space 1, which uses solar panels as a source of energy to build up the necessary electrostatic potential to accelerate the ions:
http://nmp.jpl.nasa.gov/ds1/tech/sep.html
They are also used for some new commercial communications satellites (Hughes offers this option) for altitude and station keeping.

Cheers,

J. Allie Hajian
John Cannizzo
for the "Ask an Astrophysicist" Team


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