This is a cutaway of the Radiamic liquid fuel thruster of about 100 pounds thrust. It was designated the C-1, or "Common Engine" by the National Aeronautics and Space Administration (NASA).
The C-1 was developed beginning in 1965 by the Reaction Motors Division of the Thiokol Chemical Corporation as a versatile small liquid fuel auxiliary rocket engine adaptable for a number of launch vehicles and spacecraft control systems. However, NASA decided not to go with a common engine and the C-1 never became operational. This engine was donated to the Smithsonian in 1976 by the NASA Marshall Space Flight Center.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.