Engineers at the Marshall Space Flight Center in Huntsville, Ala., have begun a series of engine tests on a new breed of space propulsion: a Reaction Control Engine developed for the Space Launch Initiative (SLI) - a technology development effort to establish reliable, affordable space access.

Marshall tests TRW Reaction Control Engine for SLI. Credit: NASA/MSFC/D. Olive

The engine, developed by TRW Space and Electronics of Redondo Beach, Calif., is an auxiliary propulsion engine designed to maneuver vehicles in orbit. It is used for docking, reentry, attitude control, and fine-pointing while the vehicle is in orbit.

The engine is unique in that it uses non-toxic chemicals as propellants - a feature that creates a safer environment for ground operators, lowers cost and increases efficiency with less maintenance and quicker turn-around time between missions. As part of its SLI work, the Marshall Center is testing multiple engine designs using different propellant combinations, including liquid oxygen as the oxidizer and liquid hydrogen or ethanol as the fuel.

"The Marshall Center is very pleased to be testing this new technology with TRW," said Robert Champion, main propulsion/auxiliary propulsion systems project manager for the Space Launch Initiative. "Marshall has a long history of testing and developing propulsion systems for launch vehicles and spacecraft. These tests will directly contribute to advancing the next generation of propulsion systems for reusable launch vehicles."

Testing includes 30 hot-firings. This is the first engine test performed at the Marshall Center that includes SLI technology. The Marshall Center is testing the reaction control engine using liquid oxygen as an oxidizer and liquid hydrogen as fuel.

"The combination of liquid oxygen and liquid hydrogen was chosen because it offers one of the highest performances in conventional liquid engines," said Champion.

Liquid hydrogen does have its drawbacks, however -- it must be stored at the extreme temperature of -423 F. "By testing various fuel combinations we are able to determine which engine will best suit the requirements needed for the reusable launch vehicle," said Champion.

Another unique feature of the reaction control engine is that it operates at dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The low level thrust of 25 pounds of force allows the vehicle to fine-point maneuver and dock while the high level thrust of 1,000 pounds of force is used for reentry, orbit transfer and coarse positioning.

Space Launch Initiative is a NASA-wide research and development program - managed by the Marshall Center - designed to improve safety, reliability and cost effectiveness of space travel for second generation reusable launch vehicles.