A test firing of twin linear XRS-2200 aerospike engines, originally built for the Lockheed Martin X-33, a next-generation, commercially operated reusable launch vehicle. The aerospike engine is a type of rocket engine that maintains its efficiency across a wide range of altitudes through the use of an aerospike nozzle. A vehicle with an aerospike engine uses 25-30% less fuel at low altitudes, where most missions have the greatest need for thrust.Photo credit: Marshall Space Flight Center
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