Electric vehicles in Space

Today marks an interesting event in science, NASA's Dawn spacecraft has entered orbit around the asteroid Vesta.

http://www.nasa.gov/mission_pages/dawn/news/dawn20110716.html

For space geeks, this is a really cool event, possibly comparable to the spacecraft that visited a comet. But for electric vehicle geeks like us, this should be seen as an equally momentous event. Why? Because the Dawn spacecraft has an electric drive.

It's called an 'ion' drive. Normally, a spacecraft uses a chemical rocket for propulsion, stored chemical energy creates heat and forces hot gasses to expand out of a nozzle, producing a reaction thrust. In an ion drive, the chemical reaction isn't used. Instead, solar panels create electrical energy on board the spacecraft. That electricity powers an electromagnetic thruster that accelerates electrically charged ions (usually Xenon gas) out the back of the engine, creating a reaction drive.

Ion drives are low-thrust, but highly efficient. So instead of using a chemical rocket in brief bursts of power, an ion drive is used almost continuously throughout a spacecraft's flight. This constant thrust eventually accumulates into a much higher speed, so the spacecraft can actually arrive at it's destination faster than a rocket-driven craft might have. And the efficiency means that less weight is dedicated to fuel, so more weight is dedicated to spacecraft instrumentation. Dawn's ion drive gets the spacecraft from 0 to 60mph in 4 days, but can run for years on end.

After a year Dawn's ion propulsion system will have increased the spacecraft's speed by 5,500 mph while consuming the equivalent of only 15 gallons of fuel. By the end of its mission Dawn will have accumulated more than 5 years of total thrust time, giving it an effective change in speed of about 23,000 mph.

http://www.jpl.nasa.gov/news/features.cfm?feature=1468

In short, it's everything we love about electric ground transportation, but in space.