Deep Space 1 Spacecraft Keeps Going and Going

It has the little engine that could, and the pint-sized
power plant on board NASA’s Deep Space 1 probe has been doing it
longer and more efficiently than anything ever launched. The
spacecraft, designed to test new technologies, has run its unique
propulsion system for more than 200 days (4,800 hours).

“The ion propulsion engine on Deep Space 1 has now
accumulated more operating time in space than any other
propulsion system in the history of the space program,” said John
Brophy, manager of the NASA Solar Electric Propulsion Technology
Applications Readiness project, at the agency’s Jet Propulsion
Laboratory (JPL) in Pasadena, Calif.

Unlike the fireworks of most chemical rockets using solid or
liquid fuels, the ion drive emits only an eerie blue glow as
ionized (electrically charged) atoms of xenon are pushed out of
the engine. Xenon is the same gas found in photo flash tubes and
many lighthouse bulbs.

The almost imperceptible thrust from the system is
equivalent to the pressure exerted by a sheet of paper held in
the palm of your hand. The ion engine is very slow to pick up
speed, but over the long haul it can deliver 10 times as much
thrust per pound of fuel as more traditional rockets.

Previous ion propulsion systems, like those found on some
communications satellites, were not used as the main engines, but
only to keep the satellites on track. Deep Space 1 is the first
spacecraft to use this important technology as its primary means
of propulsion. The NASA Space Electric Rocket Test 2, launched
into Earth orbit in 1970, had the previous record for ion
propulsion, thrusting for about 161 days.

“The importance of ion propulsion is its great efficiency,”
says Dr. Marc Rayman, project manager for Deep Space 1. “It uses
very little propellant, and that means it weighs less so it can
use a less expensive launch vehicle and ultimately go much faster
than other spacecraft.”

The ion particles travel out at about 109,000 kilometers per
hour (68,000 miles per hour). However, Deep Space 1 doesn’t move
that fast in the other direction, because it’s much heavier than
the ion particles. By the end of the mission, the ion engine will
have changed the spacecraft’s speed by about 11,000 kilometers
per hour (6,800 miles per hour).

“This opens the solar system to many future exciting
missions which otherwise would have been unaffordable or even
impossible,” added Dr. Rayman.

The technology is so efficient that it only consumes about
100 grams (3.5 ounces) of xenon per day, taking about four days
to expend just 0.4 kg (one pound).

The only other system that has operated longer is a ground-
based replica of the spacecraft’s engine. The ongoing extended-
life test, being done in a vacuum test chamber at JPL, has run
its ion propulsion system for almost 500 days (12,000 hours) and
is scheduled to complete nearly 625 days (15,000 hours) by the
end of the year.

The Deep Space 1 ion engine could have a total operating
time of more than 583 days (14,000 hours) by the end of its
mission in the fall of 2001.

With its primary mission to serve as a technology
demonstrator — testing ion propulsion and 11 other advanced
technologies — successfully completed in September 1999, Deep
Space 1 is now headed for a rendezvous with Comet Borrelly. NASA
extended the mission, taking advantage of the ion propulsion and
other systems to target a risky, but exciting, encounter with the
comet in September 2001.

But early in this bonus mission Deep Space 1 suffered a
serious setback with the loss of its star tracker navigation
system. Rather than abandon the project, NASA engineers managed a
deep-space rescue. They sent new software, on-the-fly, turning an
onboard camera into a navigation instrument — all while Deep
Space 1 was 321 million kilometers (200 million miles) from
Earth.

Deep Space 1 was launched in October 1998 as part of NASA’s
New Millennium Program, which is managed by JPL for NASA’s Office
of Space Science, Washington, DC. The California Institute of
Technology in Pasadena manages JPL for NASA.

More information can be found on the Deep Space 1 Home Page
at http://nmp.jpl.nasa.gov/ds1/ .

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