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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.

 Display Status

This object is not on display at the National Air and Space Museum. It is either on loan or in storage.
Object Details
Date ca. 1959-1961 Country of Origin United States of America Type PROPULSION-Rocket Engines Manufacturer Reaction Motors, Inc.
 Dimensions Length, 82 inches; width, 42 inches; height, 48 inches; length, thrust cylinders (8), 21.75 inches each; diameter, cylinders (8), 6 inches each; weight, approximately 500 pounds (empty weight of each XLR-11 is 210 pounds).
 Materials Mainly stainless steel, some titanium, some copper alloy tubing; pump housing, cast aluminum; insulated electrical wiring.
 Inventory Number A19630364000 Credit Line Transferred from the U.S. Air Force Data Source National Air and Space Museum Restrictions & Rights Usage conditions apply
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