This is a 25 pouind thrust RCS (Re-entry Control System) rocket motor, or thruster, for the Gemini spacecraft. The RCS thrusters controlled spacecraft's attitude (roll, pitch, and yaw). They were fixed thrust, cold nitrogen gas pressurized, self-contained propulsion systems using storable, hypergolic (self-igniting) propellants of nitrogen tetroxide and monomethyl hydrazine and therefore had no separate ignition system.
On 24 February 1962, the primary contractor for the Gemini spacecraft, the McDonnell Aircraft Corporation, awarded a subcontract to North American Aviation Company's Rocketdyne Division, for the two liquid propulsion systems for the spacecraft. One was the RCS, while the other was the orbital attitude maneuvering system (OAMS), which controlled the movement of the craft. RCS thrusters were very similar in appearance and power to the 25-lb thrust OAMS units and were located forward of the crew compartment in an independent module. The RCS consisted of a pair of completely independent systems, each having eight 25-pound thrusters fired in groups. The RCS performed up to expectations in all the Gemini flights from Gemini III from March 1965, up to the final Gemini flight (Gemini XII) in November 1966.
McDonnell Douglas donated this motor to the Museum in 1968.