Information learned from this hot-fire test series about new electro-mechanical actuator technology - which controls the flow of propellants in rocket engines - could provide key advancements for the propulsion systems of future spacecraft.

The test of twin Linear Aerospike XRS-2200 engines, originally built for the X-33 program, was performed Monday, Aug. 6, at NASA's Stennis Space Center, Miss. The engines were fired for the planned 90-seconds and reached a planned maximum power of 85 percent.

The test was originally slated to attain full-power during 100-seconds of testing. Prior to the test, engineers determined the necessary results could be achieved at reduced duration and power. Based on this determination, both planned duration and planned power were reduced.

Two shorter hot-fires of the aerospike engines were performed last month in preparation for the final test firing on Aug. 6.

The Second Generation Reusable Launch Vehicle Program, led by NASA's Marshall Space Flight Center in Huntsville, Ala., is a technology development program designed to increase safety and reliability while reducing costs for space travel.

"Because every engine proposed by industry for a second generation vehicle has electro-mechanical actuators, we took advantage of these aerospike engines already on the test stand to explore this relatively new technology now -- saving us valuable time later," said Garry Lyles, Propulsion Projects Office manager of the Second Generation Reusable Launch Vehicle Program at the Marshall Center. "This data is critical toward developing the confidence required to support the use of these actuators on future launch vehicles."

Electro-mechanical actuators electronically regulate the amount of propellant (fuel and oxidizer) flow in the engine. The new technology is a potential alternative and improvement to the older pneumatic and hydraulic-fluid systems currently used by the aerospace industry to drive and control critical rocket engine valves.

"This series of engine firings tested the actuator control system in what we call a 'real condition of use' environment," said Dr. Donald Chenevert, electro-mechanical actuator project manager at the Stennis Center. "Firing allows us to see how the integrated system handles the extreme cold of cryogenic propellants, the stress loads of the propellants pushing through the valves, and the dynamic response to commanded flow rate changes. Additionally, we have many other unique conditions such as shock and vibration loads not found in a lab, so we capture more realistic data about the true performance of the actuators."

Engineers are performing engine post-test inspections, and early indications are that all test objectives have been met, Chenevert said. The final data is to be fed directly into the engine systems being considered for a second generation reusable launch vehicle, Lyles said.

"Propulsion is one of the highest and most critical technology areas that we are exploring," said Dennis Smith, manager of the Second Generation Reusable Launch Vehicle Program Office at the Marshall Center. "Our goal also is to find, improve or develop technologies such as airframes, avionics, health management systems and ground operations - all to make getting people and payloads into space safer and cheaper."

The Rocketdyne Propulsion and Power Unit of The Boeing Company in Canoga Park, Calif., developed the aerospike engine and supported the engine tests at Stennis Space Center.

Additional information about electro-mechanical actuators can be found on the Internet at: http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2001/01-265.html

Additional information on NASA's Second Generation Reusable Launch Vehicle Program is available on the Internet at: http://www.slinews.com

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