Most Brilliant Innovators of 2009: Deep Space Plasma Thruster

Chemical rockets are ponderous. The space shuttle, for instance, carries more than 3.8 million pounds of expensive propellant—even empty, its two solid boosters weigh 193,000 pounds apiece. Oleg Batishchev, principal research scientist at MIT’s Department of Aeronautics and Astronautics, appreciates such rockets for their raw, Earth-escaping punch. But once a craft hits orbit, he says, his new invention makes more sense: The Mini-Helicon Plasma Thruster is designed to be a lighter, cheaper way to move through space.

Batishchev’s engine relies on the acceleration of plasma, a gaseous cloud in which atoms have been stripped of their electrons, making the entire mass highly conductive and responsive to electromagnetic fields. NASA developed a similar engine for its Deep Space 1 Mission, launched in 1998, but the new thruster has advantages. To start, NASA employed pricey xenon gas ($13 per liter) excited into plasma by delicate electrical components, while the new design uses nitrogen (5 cents per liter) activated by a rugged radio-frequency antenna. A mag­netic field channels the plasma through a nozzle at a stunning 40 km/sec, an order of magnitude greater than the output of a chemical rocket. “For the same amount of fuel, we’re getting 10 times more thrust,” Batishchev says. That efficiency may one day win the thruster a trip to Mars. In the meantime, it could replace chemical rockets for pushing satellites from low Earth orbit to geostationary orbit. For this application, older ion engines are too pricey, Batishchev says: “If we’re talking about applications like the privatization of space, this makes more sense.”