NASA News Release 97-057
April 30, 1997

NASA engineers at Marshall Space Flight Center in Huntsville, Ala., are conducting a series of tests for the linear aerospike engine, which will provide propulsion for NASA's X-33 Advanced Technology Demonstrator.

The test apparatus, located in the Marshall Propulsion Laboratory's East Test Area, consists of three hydrogen-cooled thrusters, or thrust cells, mounted side by side and attached to a 4-foot-long copper alloy nozzle, or ramp. This apparatus represents a section of the X-33 engine which will have two banks of 10 side-by-side thrusters.

A linear aerospike nozzle basically is a two-dimensional version of a conventional bell nozzle turned inside-out. The thrusters burn a combination of oxygen and hydrogen to propel super-hot exhaust gasses onto the ramp. These exhaust gasses push against and are accelerated by the ramp on one side -- as in a bell nozzle -- but are free to expand to atmospheric pressure on the other side. This allows the aerospike's plume to naturally widen away from the ramp as the vehicle climbs to higher altitudes and atmospheric pressure decreases, providing a self-optimizing, altitude-compensating effect.

The test series at Marshall is collecting data on cell-to-cell plume interaction, cell-to-cell feed system interaction and heating. The information is gathered through pressure, acoustic, thermal and optical sensors placed on and around the test article. High-speed cameras also capture the tests on film from various angles. Data collected from the tests is reviewed with Rocketdyne, maker of the test article as well as the X-33 and VentureStar aerospike engines. A division of Boeing North American, Rocketdyne is located in Canoga Park, Calif.

NASA and Lockheed Martin Skunk Works are developing the X-33 in a partnership formed in July 1996. Plans call for using two aerospike engines, each with two banks of 10 thrust cells, to power the vehicle, which is scheduled for flight testing in 1999.

The X-33 is a technology demonstration model of a Reusable Launch Vehicle (RLV) called "VentureStar" which Lockheed Martin hopes to develop early in the next century.

The company plans to use seven aerospike engines to power the full-scale RLV into orbit. The RLV will transport and launch space payloads at much lower costs per pound than currently possible.

Throughout the next few months, Marshall also plans to conduct aerospike engine component tests on ignition and gas generator systems.

Testing of the 20-cell X-33 aerospike engine is scheduled to take place next year at NASA's Stennis Space Center in southern Mississippi.

Rocketdyne conducted numerous hot-fire tests of a full-scale aerospike engine similar in size to the X-33 model in the early 1970s. The engine design is considered complementary to the X-33's lifting body shape because the vehicle's broad aft end lends itself to lining up a row of aerospike engines to provide the vehicle's propulsion.

Video and images of the hot-fire tests, as well as a detailed fact sheet on the aerospike engine, are available from Marshall's Public Affairs Office. Contact Dr. Dominic Amatore, Public Affairs Office, Marshall Space Flight Center, AL 35812. Phone: 205/544-0031.