Private was an experimental rocket developed by the California Institute of Technology on behalf of the United States Army. Tested in two different configurations, it provided the proof of concept that a fin-stabilised ballistic missile was technologically feasible, and led to the development of the Corporal ballistic missile.
The Private program was begun in 1944 as an outgrowth of work by the California Institute of Technology's Guggenheim Aeronautical Laboratory that had produced the first practical jet-assisted take-off (JATO) rockets. A proposal to adapt the JATO rockets for research into the development of ballistic missiles was accepted, and the first flight of the Private A rocket, developed under the direction of Tsien Hsue-shen, took place in December 1944, conducted at Camp Irwin in California.
Private A was an unguided, fin-stabilised ballistic rocket; it consisted of a JATO unit equipped with cruciform tail fins, and a set of four T22 booster rockets that were jettisoned after launch. This made Private A the first multistage rocket to be flown in the United States.