Rocket Engines, Liquid Fuel, XLR-11, Dual (Interim X-15 Pair)

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    Rocket Engines, Liquid Fuel, XLR-11, Dual (Interim X-15 Pair)

    Two XLR-11 engines of four thrust cylinders each, mounted on top of one another in a common frame; each engine with pump mounted separately to the right, on the frame and without connecting pipes. Thrust cylinders of each XLR-11 arranged in diamond shaped pattern with adjoining plumbing and wiring attached at the end, including vertical, propellant feed lines into the cylinder assembly. Internal nozzles within the ends of the thrust cylinders. Overall, bare metal gray. Frame dark green. Each pump housing, red.

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This is the so-called Interim Engine of the X-15 rocket research aircraft and is made up of two joined XLR-11 rocket engines. The XLR-11 was the standard engine for the earlier Bell X-1 and other rocket research aircraft. The Interim powerplant was used in the X-15 from 1959-1961 due to developmental delays of that aircraft's newer and more powerful XLR-99 Pioneer rocket engine. The Interim engines achieved the X-15's first 29 powered flights. The Interim engine produced a total of 16,400 pounds from its four chambers and was sufficient for the preliminary test flights of the X-15. It achieved some notable records in that phase of the X-15 program. This Interim Engine was transferred to the Smithsonian in 1963 from the U.S. Air Force.