a mechanism mounted on a missile launch rail which may be actuated to perform the functions of engaging electrical circuit firing contacts for the missile , rotating a rocket motor arming arm , and unlocking the forward motion missile restraints . particular structure including a bi - directional linear actuator drive mechanism is provided to perform these functions . in addition , the structure incorporates the capabilities of restraining the rocket motor against full thrust in the event of an inadvertent firing and of restoring the rocket motor to safe condition if a launch is aborted .