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The sign accompanying the linear aerospike engine. It reads


The Linear Aerospike Engine

Marshall's Legacy of Flight

Seeking to develop lighter, more powerful launch vehicles capable of versatile work in Earth orbit, NASA and Lockheed Martin Aeronautics of California experimented in the late 1990s with an engine without a nozzle. Developed to support the X-33 Advanced Technology Demonstrator Program here, the linear aerospike is shaped like an inverted bell turned inside out, "unwrapped" and laid flat. A series of small combustion chambers along the unwrapped bell shoot hot gases along its outer surface, producing thrust. The single-stage X-33 would have been powered by a pair of these engines. Though the X-33 program ended in 2000, the successful development of the linear aerospike engine is helping engineers refine new ideas for tomorrow's next-generation propulsion systems.

Linear Aerospike Quick Facts

Propellants: Liquid Oxygen/Liquid Hydrogen
Thrust (at sea Level): 204,420 lbs.
Height: 7.5 feet
Width: 7.5 feet
Depth: 11.17 feet


While this particular incarnation of the linear aerospike engine was developed in the 1990s, the aerospike concept dates back much farther.

Rocketdyne had developed a round (referred to as "annular" or "toroidal") aerospike engine in the late 1960s and planned to submit the engine in the competition for the Space Shuttle Main Engine. In October 1969 and again in July 1970 NASA issued statements indicating that they expected the engine to be chosen for the SSME program to be a "bell-type engine" with a staged combustion cycle, so Rocketdyne abandoned this effort.

Before development ceased, however, Rocketdyne conducted a test program between March 1966 and October 1967. Information about this test program is contained in

Photos of Rocketdyne's annular aerospike engine undergoing a hot-fire is available from Alternate Wars; do a search for "NASA/USAF Advanced Development Program (ADP) Aerospike Engine" and scroll down to the bottom of that section.

Although no longer pursued for the SSME, Rocketdyne did continue its development on the aerospike concept, producing and test-firing two linear aerospike engines in the early 1970s. Called the "Linear Test Bed" engines, the program started in April 1970 when MSFC's Saturn System Office authorized the work. Research using Linear Test Bed No. 1 concluded in May or June 1972 (depending upon the source), after 44 successful tests; the Linear Test Bed No. 2 work concluded in October 1973 after 29 successful tests. Never intended for flight, the engines were constructed of heavy, inexpensive materials and used turbopumps from the 1960s-era J-2S program.

Many of the photos and videos available online showing the hot-firing of a linear aerospike engine are of the Linear Test Bed engines (including some photos purported to be of the XRS-2200), which has a wider base than the XRS-2200. Oddly enough, even a Rocketdyne fact sheet on the RS-2200 includes a photo of a Linear Test Bed Engine hot-fire test.

Additional information about the Linear Test Bed program can be found in the Linear Test Bed Final Report, Volume I: Test Bed No. 1 and Linear Test Bed Final Report, Volume II: Test Bed No. 2 reports and The Linear Test Bed Program video.

 
Sign by XRS-2200 Linear Aerospike Engine at Marshall Space Flight Center Building 4205
Time picture taken Thu Jul 19 10:59:50 2012
Location picture taken Building 4205
Marshall Space Flight Center
Huntsville, AL
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