This is the attitude control system for the Titan 3E launch vehicle. The system consisted of three SE-9 rocket engines to provide attitude control in three axis. Each engine produced from 45 pounds of thrust and used storable, hypergolic, or self-igniting, propellants that made it simple and reliable. The Titan 3E was a modified U.S. Air Force Titan missile used to launch deep space probes or satellites into geosynchronous orbits. Most notably, the Titan III-E launched two Viking spacecraft to Mars in 1975. These engines were transferred to the Smithsonian in 1970 from the U.S. Air Force.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.