http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true
There's a growing chorus of calls to send astronauts to Mars rather than the moon, but critics point out that such trips would be long and gruelling, taking about six months to reach the Red Planet. But now, researchers are testing a powerful new ion engine that could one day shorten the journey to just 39 days.
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.
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