Rocket nozzle automatic release system
The function of the mechanism described is to automatically jettison a rocket nozzle element at the conclusion of boost in order to achieve a cruise mode nozzle configuration for the balance of powered flight. The boost nozzle is retained by latched pistons that are mechanically secured until released by chamber pressure, which simultaneously assumes retention of the nozzle by holding the primary piston in place. Upon attainment of cruise mode, the chamber pressure drops, allowing springs to overcome the primary piston force and pull the keeper ring forward to free the nozzle for jettison by motor exhaust.
Kimball, J. B.↗