The Commercial Titan III, also known as CT-3 or CT-III was an Americanexpendable launch system, developed by Martin Marietta during the late 1980s and flown four times during the early 1990s. It was derived from the Titan 34D, and was originally proposed as a medium-lift expendable launch system for the US Air Force, who selected the Delta II instead. Development was continued as a commercial launch system, and the first rocket flew in 1990. Due to higher costs than contemporary rockets such as the Ariane 4, orders were not forthcoming, and the CT-3 was retired in 1992.
The Commercial Titan III differed from the Titan 34D in that it had a stretched second stage, and a larger payload fairing to accommodate dual satellite payloads.
The second launch occurred on 14 March, and carried the Intelsat 603 satellite. The rocket's second stage failed to separate, and the payload could only be released from the rocket by means of jettisoning its kick motor. It was later visited by Space ShuttleEndeavour, on mission STS-49. Astronauts attached a new kick motor, which raised the satellite into a geosynchronous transfer orbit, as had originally been planned. The third launch, on 23 June, carried Intelsat 604, and was successful. There were no CT-3 launches in 1991, due to maintenance work at Launch Complex 40. The final flight of the Commercial Titan III occurred on 25 September 1992, and placed NASA'sMars Observer spacecraft into heliocentric orbit, by means of a Transfer Orbit Stage.