The Transtar system was an upper stage engine using injector(s), chamber, and nozzle derived from the OMS system. These propellants are pump-fed which increase chamber pressure and Isp. They also permit the use of low-pressure lightweight tanks.. Manufacturer: AeroJet Propulsion Division. Applications: upper stage. Mounting: gimballed ( 10 degrees by two electromechanical actuators. Mixture Ratio: 1.8:1. Cooling Method: fuel regenerative for chamber, radiative for extension. Burn Time: not available, 15 starts.