Ion Propulsion Engine Speeds Deep Space Probe on Its Way

The ion propulsion engine on NASA’s Deep Space 1 probe has been running for more than 200 days since the craft’s launch in October 1998, propelling the tiny spacecraft more than 206 million miles from the Earth on its mission to intercept the Comet Borelly in September 2001, the space agency said this week. The engine, which runs intermittently, ionizes atoms of xenon and ejects them at 68,000 mph, consuming about one pound of xenon every four days. After the projected 538 days of thrust, the small engine will have increased the probe’s speed by about 6,800 mph, a much greater boost than could be achieved with a similar quantity of rocket fuel.

Soon after launch, Deep Space 1 lost the use of its star tracker navigation system, threatening its rendezvous, but ground personnel were able to reprogram the tracker and save the mission.