SATELLITE LAUNCH SCHEDULED IN '97\Edwards laboratory to test propulsion system for use in orbit.

Byline: Charles F. Bostwick Daily News Staff Writer

An experimental satellite propulsion system developed at Phillips Laboratory's Propulsion Directorate is expected to be launched in a test in 1997, officials said Tuesday.

The size of an office desk, the system uses an electric arcjet - similar to an arc-welding torch - to heat a stream of ammonia, providing thrust to shift an orbiting satellite from place to place above the Earth.

"It's a very small amount of thrust but with a satellite you don't need a large amount of thrust," said Ranney Adams, spokesman for the Edwards laboratory, which develops and tests new missile, rocket and satellite propulsion systems.

The advantage of the arcjet is that it uses about one-third the fuel needed by conventional rockets to maneuver satellites in orbit.

That means military reconnaissance satellites can maneuver over wider distances to spy on hot spots, as was done during the Persian Gulf crisis, before they run out of fuel and are relegated to orbiting over a single swath of the Earth.

Satellites could also be built smaller because they don't have to carry as much fuel, allowing them to be launched with smaller and less expensive rockets, or they could carry more and heavier instruments.

The arcjet will use its satellite's large solar cells and batteries to generate and store energy.

An arcjet propulsion system intended to demonstrate that the method is practical was built by TRW Space and Electronics Group in Redondo Beach under a $24 million contract issued in 1990 by Phillips Laboratory's Propulsion Directorate at Edwards, Adams said.

The Edwards unit had spent about $1 million developing the arcjet technology during the 1980s, Adams said.

TRW's arcjet - called ESEX, for Electric Space Experiment, will be mounted onto an Air Force research satellite - ARGOS, or Advanced Research and Global Observation Satellite - scheduled for launch next year.