This is the Titan II missile engine as adapted to launch the Gemini manned spacecraft. The original Titan I liquid-fuel engine powered the first stage of the two-stage Titan I intercontinental ballistic missile (ICBM). It had two identical separate engine chamber assemblies, each generating 150,300 pounds of thrust, or 300,600 pounds total. The propellants were liquid oxygen (lox) and RP-1, a type of kerosene. This engine was donated to the Smithsonian by the Aerojet-General Corp. in 1971.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.