This is the liner for the 1,300 pound thrust M17G regeneratively-cooled liquid fuel rocket motor constructed and tested by Reaction Motors, Inc. Its development in 1942 contributed to the development of a JATO (Jet-Assisted-Take-Off) unit for use by heavily-loaded Navy PBM seaplanes.
The raised diagonal ridges helped channel the fuel (gasoline) around the chamber while fine grooves throughout the length of the jacket cylinder helped swirl the coolant. The liner thus served as a cooling jacket and gave the motor a double wall. But the Navy did not adopt liquid fuel JATO engines and chose simpler and cheaper solid propellant JATOs. This object was donated to the Smithsonian by the Reaction Motors Division of Thiokol Chemical Corporation in 1985.
Reaction Motors Div., Thiokol Chemical Corp.