Martin Marietta SM-68B/LGM-25C Titan II By Titan II was the longest-serving ICBM (Intercontinental Ballistic Missile) in the U.S. Air Force strategic arsenal. The SM-68B, developed from the Titan I ICBM, was on operational alert from 1963-1987. For most of its nearly 25 years of operation, Titan II was the largest and most powerful American nuclear-armed missile. The Titan design also enjoyed a long career as a space launch vehicle, sending satellites and manned spacecraft into earth orbit. While the SM-68A Titan I system was becoming operational, the USAF recognized that it could be simplified and improved. Using the same manufacturing and test facilities, the SM-68B took shape as a major step forward in ICBM technology. Perhaps Titan II's most important feature was its quick-launch capability. It could be launched in about 60 seconds from inside its underground silo (Titan I took 15 minutes and had to be elevated above ground first). This speed was crucial in responding to a preemptive nuclear attack before incoming missiles arrived. New "hypergolic" liquid fuels made Titan II's quick launches possible. Hypergolic fuels ignite on contact with one another, eliminating the need for an ignition system, and they can be stored at room temperature inside the missile. Partly as a result of using these new propellants, the SM-68B had fewer parts and a simpler design than the SM-68A. Also, a new silo design vented the tremendous blast of Titan II's improved engines away from the missile, allowing in-silo launching and eliminating the need to elevate the SM-68B to ground level before launch. Titan II's advanced "all-inertial" guidance system made the missile less vulnerable to enemy attack. Each SM-68B carried its own self-contained guidance equipment and did not rely on ground computers. This improvement made widely dispersed bases possible, and Titan II sites were typically several miles apart, enhancing survivability during a potential nuclear strike. At the height of SM-68B operations, the USAF deployed 54 Titan IIs at three bases in Arizona, Kansas and Arkansas. Each base had two squadrons of nine missiles each. The combat crew for a single missile included two officers and two enlisted personnel, but many support troops were required to maintain the missiles, train crews, and provide security. In 1981 the USAF undertook a missile modernization program, and Titan II ICBM operations ceased in 1987. Spare SM-68Bs were converted to space boosters and used to launch satellites. This role was not new for Titan II, since this powerful and reliable rocket had been used for many years in civil and military space programs. Titan IIs launched manned Gemini missions for NASA in the mid-1960s, and later Titans evolved into more powerful space boosters with the addition of "strap-on" solid rockets, launching some of the most important U.S. military satellites. TECHNICAL NOTES: Warhead: Single nuclear warhead in the megaton range Re-entry vehicle: General Electric Mark 6, ablative Engines: (1st stage) Aerojet LR87-AJ-5 of 430,000 lbs. thrust; (2nd stage) Aerojet LR91-AJ-5 of 100,000 lbs. thrust Propellants: Aerozine 50 fuel and nitrogen tetroxide oxidizer Range: 9,000 miles Length: 108 ft. Diameter: 10 ft. Weight: 330,000 lbs. fueled Click here to return to the Missile Gallery. Find Out More Related Fact Sheets Martin Marietta SM-68A/HGM-25A Titan I Gemini Spacecraft Aerojet-General LR87 Liquid Rocket Engine Lectures Dr. David K. Stumpf: "Titan II - The Few but the Powerful" (01:03:58) Other Resources Air Force Space Command: ICBM 50th Note: The appearance of hyperlinks does not constitute endorsement by the National Museum of the USAF, the U.S. Air Force, or the Department of Defense, of the external website, or the information, products or services contained therein.