Traditional rockets burn chemical fuel to produce thrust. Most of that fuel is used up in the initial push off the Earth’s surface, so the rockets tend to coast most of the time they’re in space.
Ion engines, on the other hand, accelerate electrically charged atoms, or ions, through an electric field, thereby pushing the spacecraft in the opposite direction. They provide much less thrust at a given moment than do chemical rockets, which means they can’t break free of the Earth’s gravity on their own.
But once in space, they can give a continuous push for years, like a steady breeze at the back of a sailboat, accelerating gradually until they’re moving faster than chemical rockets.
Several space missions have already used ion engines, including NASA’s Dawn spacecraft, which is en route to the asteroids Vesta and CeresMovie Camera, and Japan’s spacecraft Hayabusa, which rendezvoused with the asteroid Itokawa in 2005.
But a new engine, called VASIMR (Variable Specific Impulse Magnetoplasma Rocket), will have much more “oomph” than previous ones. That’s because it uses a radio frequency generator, similar to transmitters used to broadcast radio shows, to heat the charged particles, or plasma.
The engine is being developed by the Ad Astra Rocket Company, which was founded in 2005 by plasma physicist and former space shuttle astronaut Franklin Chang-Diaz.
As hot as the sun
VASIMR works something like a steam engine, with the first stage performing a duty analogous to boiling water to create steam. The radio frequency generator heats a gas of argon atoms until electrons “boil” off, creating plasma. This stage was tested for the first time on 2 July at Ad Astra’s headquarters in Webster, Texas.