|Country of origin||United States|
|Used on||Titan III|
|Height||4.57 meters (15.0 ft)|
|Diameter||3.05 meters (10.0 ft)|
|Gross mass||12,247 kilograms (27,000 lb)|
|Thrust||8,000 lbf (36 kN) each|
|Specific impulse||311 seconds (3.05 km/s)|
|Burn time||440 seconds|
|Fuel||Aerozine 50 / N|
Transtage was developed in anticipation of a requirement to launch military payloads to geostationary orbit; a contract for development of the stage was issued on 20 August 1962. Transtage used a pressure-fed two-chamber configuration, using Aerozine 50 fuel and nitrogen tetroxide as oxidizer; the thrust chambers were gimbaled for steering and each produced 8,000 lbf (36 kN) of thrust. The design specification required up to three restarts during the first six hours of a mission.
Forty-seven Titan III launches are known to have used Transtage upper stages; of those, three are known to have suffered launch failures. The first launch, boosted by a Titan IIIA, occurred on 1 September 1964; the Transtage failed to pressurize, resulting in premature engine cutoff, and a failure to reach orbit. The second launch, on 10 December, was successful, and all ensuing launches used the Titan IIIC launch vehicle. The last launch of a Transtage was on 4 September 1989, boosted by a Titan 34D rocket.