Saturday science subject: VASIMR

— 4:43 PM on August 1, 2009

Mars is pretty far away—over 650 times the Earth-Moon distance right now, according to Wolfram Alpha. Could we get there in just 39 days? New Scientist says trips to the red planet would normally take half a year, but a new type of ion engine could indeed take people there in just over one month.

Ion engines work by accelerating ions through an electric field, New Scientist says. The new engine, dubbed VASIMR (for Variable Specific Impulse Magnetoplasma Rocket), reportedly delivers greater power by heating up ions with a radio frequency generator:

The radio frequency generator heats a gas of argon atoms until electrons "boil" off, creating plasma. . . . The plasma could produce thrust on its own if it were shot out of the rocket, but not very efficiently. To optimise efficiency, the rocket's second stage then heats the ions to about a million degrees, a temperature comparable to that at the centre of the sun.

It does this by taking advantage of the fact that in a strong magnetic field – like those produced by superconducting magnets in the engine, ions spin at a fixed frequency. The radio frequency generator is then tuned to that same frequency, injecting extra energy into the ions. . . . Strong magnetic fields then channel the plasma out the back of the engine, propelling the rocket in the opposite direction.

New Scientist says this technique lets VASIMR reach "power levels a hundred times as high as other engines." The researchers at Ad Astra, the company that developed VASIMR, are only aiming to get about a pound of thrust. Not much, but as the article points out, rocket engines mostly "coast" after leaving Earth in order to save fuel, so they'd be even slower in practice.

VASIMR would need fuel too, mind you. Reaching Mars in 39 days would require an onboard nuclear reactor, technology that would be "quite a ways down the line," according to Ad Astra Research Director Jared Squire. Still, the project has NASA excited, and the space agency has provided a "small stipend towards VASIMR's development." In the meantime, NASA and Ad Astra plan to test the engine from the International Space Station in 2012 or 2013.

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