STENNIS SPACE CENTER, Mississippi, USA — rocket motor that could push payloads into space more safely, cleanly and cheaply than conventional solid and liquid fuels passed muster during its first significant firing, a NASA manager said Thursday.

A rocket motor that could push payloads into space more safely, cleanly and cheaply than conventional solid and liquid fuels passed muster during its first significant firing, a NASA manager said Thursday.

The rocket motor undergoes a test at Stennis

Less noxious and combustible on its own than most solid rocket motors and less expensive than most liquid engine motors, the hybrid motor was fired for 15 seconds on Friday while laid on a horizontal test-stand.

It currently can launch 80,000 pounds on top of its weight at sea level — enough for small research payloads, said Robert Bruce, project manager of the Hybrid Propulsion Demonstration Program at NASA's Stennis Space Center in Mississippi. The center is located on 125,000 acres of land far from residential communities.

"It's inherently safe because you can hit it with a hammer," Bruce said. "You can drop it. You can even try to light it with a lighter. Most solid rocket motors are very sensitive to heat and electrical discharge."

Initially, the thick black fuel is poured into a casing and allowed to set and turn rubbery like gelatin.

To ignite it, an oxidizer is continuously injected into its core, giving engineers a safety feature that other propellants lack — the fire and thrust can be turned off even after ignition with the flip of a switch.

During a preliminary test in July, engineers let the rocket motor fire for two seconds.

The motor was designed and built by 35 engineers, managers and technicians who are part of a consortium that includes NASA, Lockheed Martin Astronautics and Boeing Rocketdyne.

NASA plans to use the new motor to launch a 60,000-pound payload of microgravity experiments in March 2000, Bruce said.

Hybrid motor is safer, NASA says

Jennette Gordon, an environmental specialist at Stennis, called the hybrid motor environmentally safe.

It emits far less noxious fumes than most solid rocket motors in existence today but more than liquid rocket engines, which are fairly benign compared to the solid type.

The 45-foot-long motor resembles the solid rocket boosters used on the space shuttle and weighs 125,000 pounds.

The hybrid motor is years away from being useful for something like the space shuttle, which relies on three liquid engines and two solid rocket boosters to provide 1.5 million pounds of thrust. Engineers hope to scale up its thrust on future models.

Future tests of the motor will rely on different ignition and oxidation injection methods.

Engineers started working seriously with hybrid motors about eight years ago. The group at Stennis began building this latest version about 14 months ago, Bruce said.

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