This is the nozzle for a 12AS-1000D-5 JATO (Jet-Assisted-Take-Off) rocket motor, developed and manufactured by the Aerojet Engineering Corporation and used to help lift light aircraft or for rescue operations. The motor produced one thousand pounds of thrust for twelve seconds. One of the most popular JATOs, the 12AS-1000D-5 was the first to be type certified by the Civilian Aviation Authority (certification R-1).
Aerojet gave this nozzle to the Museum in 1948.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.