This propulsion system of a rocket motor assembly includes an array of attitude-control rocket engines, one or more oxidizer-fluid sources, one or more ignition-fluid sources, and, optionally, one or more primary rocket engines. Each of the attitude-control rocket engines has a respective combustion chamber and is offset from the longitudinal axis of the rocket motor assembly so that when a selected one or group of the attitude-control rocket engines is fired, the flight path of the assembly is diverted and/or the rocket assembly spins. The oxidizer-fluid and ignition-fluid sources are in operative communication with the attitude-control rocket engines to respectively permit oxidizer fluid and ignition fluid to be supplied to selected ones or groups of the attitude-control rocket engines. Optionally, a portion of the ignition fluid from the ignition-fluid source can be cooled and used to pressurize the oxidizer-fluid source.