Skip to main content Smithsonian Institution

Catalog Data

Reaction Motors, Inc.  Search this
Mainly stainless steel, some titanium, some copper alloy tubing; pump housing, cast aluminum; insulated electrical wiring.
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).
PROPULSION-Rocket Engines
Country of Origin:
United States of America
ca. 1959-1961
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.
Credit Line:
Transferred from the U.S. Air Force
Inventory Number:
Restrictions & Rights:
Usage conditions apply
See more items in:
National Air and Space Museum Collection
Data Source:
National Air and Space Museum