This is the regeneratively-cooled liquid fuel rocket motor designed and built in 1942 by James H. Wyld of the American Rocket Society (ARS) for the Navy. It is a copy of the original Wyld motor, built in 1937 and successfully tested in 1938 and 1941.
One major problem facing early rocket experimenters was a suitable cooling for their motors, which often over-heated. In the regenerative system, the propellant circulates around the motor's cooling jacket before injection into the combustion chamber, where it is ignited with the oxidizer (liquid oxygen). Wyld, with three other ARS members, formed Reaction Motors, Inc. (RMI) in 1941 to develop the Wyld engine. RMI thus produced reliable JATO (Jet-Assisted-Take-Off) motors to help lift large, heavily-loaded planes. The motor was donated to the Smithsonian in 1968 by the Aerojet General Corp.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.