Ion-powered Spacecraft Sets Flight
Source: CNN.com
August 18, 2000
(CNN) -- A futuristic engine on an experimental
spacecraft has racked up more operating time in space than any
previous propulsion system, NASA said.
Deep Space 1, designed to test a variety of new
technologies, has zoomed through space using an ion drive propulsion
system for more than 200 days, mission managers said.
"The key here is the operating time. Certainly other
spacecraft have been in space for a long time. But they don't run
their propulsion systems very long," said John Brophy, a Deep Space 1
scientist with NASA's Jet Propulsion Laboratory.
Unlike traditional chemical rockets that blast out hot
exhaust, an ion drive emits only an eerie blue glow as ions, or
electrically charged atoms, exit the engine. The source of the ions is
xenon, a gas found in flash tubes and lighthouse bulbs.
The hardly noticeable thrust from the ions exerts about
the same amount of pressure as a sheet of paper held in the palm of
one's hand. While slow to pick up speed, ion propulsion creates
substantial power over great distances, delivering 10 times more
thrust per pound of fuel than conventional rockets.
"It's acceleration with patience," said Deep Space 1
scientist Marc Rayan. Analogies with tortoises and hares become nearly
inevitable, he said.
"The importance of ion propulsion is its great
efficiency. It uses little propellant, which means the spacecraft
weighs less, can use a less expensive launch vehicle and go much
faster than other spacecraft," Rayan said.
A NASA rocket launched in Earth orbit in 1970 held the
previous ion propulsion record in space, about 161 days. Numerous
communications satellites use ion propulsion, but only to control
their position, not as a primary means of propulsion.
The success of ion propulsion on Deep Space 1 could
transform the future of space exploration.
"It was always considered so exotic that no one would
consider relying on it unless someone showed it worked in a realistic
setting. Deep Space 1 took those risks so later missions wouldn't have
to," Rayan said.
Launched in 1998, Deep Space 1 completed its primary
mission of testing one dozen advanced technologies by September 1999.
But the ship unexpectedly lost the use of its star tracker navigation
system several months later on its way to a rendezvous with a comet in
2001.
Mission engineers managed to restore its sense of
direction by writing new computer programs that use an onboard camera
instead of the star tracker.
"Besides that hiccup, the mission has been flawless,"
Rayan said.
The spacecraft is more than 206 million miles (332
million km) from Earth, according to the Deep Space 1 website.
by Richard Stenger