A series of three hot-fire tests on
tandem Boeing Rocketdyne XRS-2200 aerospike engines has been completed at
NASA’s John C. Stennis Space Center, confirming the performance of
electromechanical actuators (EMAs) that were used in propellant valving for
the engines. EMAs are seen as a technology of choice in new rocket engines
that could be developed under the Space Launch Initiative (SLI).

With a total of 120 seconds of hot-fire performance, the dual-engine test
series has been declared a success, with test objectives met, along with
schedule and cost goals. “We were able to acquire all of the data that we
wanted, which NASA other SLI contractors can use for SLI applications. The
Team did an outstanding job with limited resources and a short timeline,”
said Steve Bouley, division director, propulsion development at the
Rocketdyne Propulsion & Power unit of The Boeing Company,

“Data from the final test completed on August 6 is being thoroughly
reviewed,” said Aerospike Program Manager Mike McKeon. “But we’ve already
had a good look at how the EMAs perform under hot-fire conditions, and the
results confirmed our expectations.”

Instead of hydraulics, future propulsion systems may use EMAs to control
major propellant valves, so gaining performance data in “real world” testing
has significant value. There are six EMAs on each aerospike test engine that
are used to deliver the propellants to the thruster banks and gas

Among other benefits, EMAs are a big help in reducing vehicle weight and
complexity by eliminating the hardware needed to store and pressurize the
hydraulic fluid. And the hope is that future generations of EMAs will be
even more compact than those currently in operation.

The first test of the series — a 5-second ignition test — was run on July
12 and a 25-second test was run on July 24. The third test went for 90

“All of the EMAs performed according to expectations,” McKeon said. “Current
models seem to be rather fragile and we did have to replace several as the
series went on, but that was not unexpected; getting a read on durability
was one of the issues we wanted to address. Nevertheless, the EMA technology
itself is very good, very effective. What seems to be needed are smaller,
more robust models. Newer designs will be helped by thorough analysis that
we plan to do with the EMAs that were a part of this test series.”

Following the series, the engines will now be removed from the stand and put
in storage at SSC, awaiting NASA instructions on final disposition.

Fourteen single-engine test firings of a development configuration of the
unique Aerospike engine were successfully completed at Stennis Space Center
last year, followed by a series of dual-engine tests that was concluded late
this spring.

Rocketdyne developed the XRS-2200 Aerospike engine at its Canoga Park,
Calif., facility for the now-cancelled X-33 program. A joint Boeing and NASA
team at Stennis Space Center did final engine assembly.



Dan Beck

(818) 586-4572