Titan (rocket family)

Titan II

The Titan II family includes the Titan II ICBM and two space-launch derivatives: the Titan II GLV and the Titan 23G. The Titan II used the LR-87-5 engine, which burned hypergolic propellants—nitrogen tetroxide as oxidizer and Aerozine 50 (a 50/50 mix of hydrazine and unsymmetrical dimethylhydrazine)—instead of the liquid oxygen and RP-1 used by the Titan I. The original guidance system, built by AC Spark Plug, employed an inertial measurement unit derived from MIT Draper Laboratory designs and an IBM ASC-15 missile guidance computer.

When spares became scarce, the system was replaced starting in March 1978 by the Delco Electronics Universal Space Guidance System, which used a Carousel IV IMU and a Magic 352 computer; the change saved $72 million per year in maintenance and was completed in 1981. The switch to room-temperature hypergolic propellants eliminated the dangers of cryogenic liquid oxygen, which had caused several Atlas and Titan I silo explosions. However, the toxic and corrosive nature of Aerozine 50 and nitrogen tetroxide led to accidents.

In August 1965, a fire ignited by a welding torch in a Titan II silo northwest of Searcy, Arkansas, killed 53 construction workers.

Titan III

The Titan III was a modified Titan II with optional solid rocket boosters, developed for the United States Air Force as a heavy-lift satellite launcher. It was formally known as Program 624A (SSLS), with several expansions of that acronym. The Titan III core resembled the Titan II but had thicker tank walls, ablative skirts, radio ground guidance instead of inertial guidance, guidance placed on upper stages, removal of retrorockets and other ICBM hardware, and slightly larger second-stage propellant tanks that used space in the avionics truss without lengthening the stage.

The LR-87 engines received performance enhancements over time; on SRB-equipped variants, heat shields protected the engines from booster exhaust, and the engines were modified for air-starting. The first Titan III guidance system used an AC Spark Plug IMU and an IBM ASC-15 computer whose drum memory was lengthened by 20 tracks, increasing capacity by 35%. The Titan IIIC used a Delco Carousel VB IMU and MAGIC 352 computer. The Titan IIIA was a prototype with a Transtage upper stage.

The Titan IIIB series (23B, 24B, 33B, 34B) used an Agena D upper stage to launch KH-8 GAMBIT reconnaissance satellites from Vandenberg Air Force Base into polar orbits, with a maximum payload of about 7,500 pounds (3,000 kilograms).

Titan IV

The Titan IV was an extended-length Titan III with solid rocket boosters, capable of launching with a Centaur upper stage, the USAF Inertial Upper Stage, or no upper stage. At the time of production, the Titan IV was the most powerful uncrewed rocket available to the United States, with correspondingly high manufacturing and operations costs.

By the time it became operational, Department of Defense and NRO satellite launch requirements had declined due to longer satellite lifetimes and reduced reconnaissance demand after the Soviet Union's internal disintegration. These factors, along with technology improvements, drove the unit cost very high. Additional expenses came from ground operations at Vandenberg Air Force Base for polar launches; Titan IVs also launched from Cape Canaveral Air Force Station for non-polar orbits.

Launch vehicle retirement

Most decommissioned Titan II ICBMs were refurbished for Air Force space launches and achieved a perfect launch success record. The Titan IVB was the last Titan to remain in service; its penultimate launch occurred from Cape Canaveral on 30 April 2005, and its final launch from Vandenberg on 19 October 2005 carried the USA-186 optical imaging satellite for the National Reconnaissance Office.