NASA’s Second Generation Reusable Launch Vehicle Program – also
known as the Space Launch Initiative – is making advances in propulsion
technology with this third and final successful engine hot-fire designed
to test electro-mechanical actuators.

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

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:

Additional information on NASA’s Second Generation Reusable Launch
Vehicle Program is available on the Internet at: