Martin Marietta SM-68A/HGM-25A Titan I
Entering operational service in 1962, Titan I was the United States’ first multistage ICBM (Intercontinental Ballistic Missile). Incorporating the latest design technology, Titan provided an additional nuclear deterrent to complement the U.S. Air Force’s Atlas missile. Though the SM-68A was operational for only three years, it was an important step in building the Air Force’s strategic nuclear forces.
The first American ICBM based in underground silos, Titan I gave USAF managers, contractors and missile crews valuable experience building and working in vast bunkers containing everything the missiles and crews needed for operation and survival. These early silos, however, had certain drawbacks. First, the missiles took about 15 minutes to fuel, and then had to be lifted to the surface on huge elevators for launching, which slowed their reaction time. Rapid launching was crucial to avoid possible destruction by incoming missiles, even though Titan shelters were designed to withstand nuclear blasts. Second, the missiles’ placement close together in groups of three –necessary because they shared a single ground-based radio guidance system — made them vulnerable to nuclear attack. All-inertial guidance, which does not depend on ground computers, was not yet perfected.
In its brief career, Titan I equipped six squadrons of nine missiles each, in Colorado, Idaho, California, Washington state and South Dakota. Although Titan I’s two stages gave it true intercontinental range and foreshadowed future multistage rockets, its propellants were dangerous and hard to handle. Super-chilled liquid oxygen oxidizer had to be pumped aboard the missile just before launch, and complex equipment was required to store and move this liquid. Kerosene fuel also was pumped aboard just before launch.
Titan I allowed USAF missileers to perfect techniques for efficiently operating strategic missile facilities spread across several states and requiring great coordination and skill. Still, the SM-68A was a transitional missile. Even as the USAF deployed 54 Titan Is on operational alert from 1963-1965, it prepared to deploy more advanced Titan IIs in their place. Later missiles, like Titan II, used safer fuels and more advanced guidance, but followed the SM-68A example of underground basing and multiple stages.
The two-stage Titan I, together with the Atlas, comprised our nation’s first generation of liquid-fueled, strategic, intercontinental ballistic missiles. Operational Titan Is contained an all-inertial guidance system to direct the nuclear warhead to the target. Liquid propellants for the Titan I’s Aerojet rocket engines were kerosene fuel and liquid oxygen. The HGM-25A (silo-stored, surfaced-launched, ground attack missile), formerly known as the SM-68 (Strategic Missile), was the first USAF ICBM to be placed in hardened underground silos for protection against enemy attack; however, they had to be lifted from their silos to the surface by elevator prior to launching.
The USAF launched its first test Titan I on Feb. 6, 1959, and in April 1962 the first Strategic Air Command squadron of nine Titan Is was declared operational. Eventually squadrons of Titan Is were deployed at five different bases in the western United States. By 1965, however, Titan Is were being phased out in favor of Titan IIs, which offered greater range and payload and were launched from within their silos. Modified Titan IIs also were used to launch the Gemini astronauts into space. The larger and more versatile Titan III, developed from the Titan II, became the third generation of Titan launch vehicles used by the USAF. The Titan III (and Titan 34D) had greatly increased payload lifting capacity provided by two strap-on solid rocket boosters, which combined with the LR-87 liquid-fueled first-stage engine, brought the total lift-off thrust to well over 1 million pounds.
The Titan IVB is the latest version in the Titan family of heavy lift vehicles in use by the USAF. It flew for the first time in February 1997.
The museum has a Martin Marietta SM-68A/HGM-25A Titan I on display in the Missile & Space Gallery.
Note: The Martin B-68 Titan took over the designation after the Martin XB-68 bomber project was canceled. The B-68 Titan I was redesignated SM-68 and later changed to HGM-25A. The Titan I is easily distinguished from the Titan II by noting that the Titan I has a smaller diameter upper stage (the Titan II is constant diameter first and second stages).
TECHNICAL NOTES:
Armament: Nuclear warhead
Engines: First stage powered by Aerojet LR87 two chamber liquid propellant rocket fueled by Kerosene and liquid oxygen (oxidizer) of 300,000 lbs. thrust; note that later versions of the LR87 were much more powerful and fueled by Aerozine-50 (fuel) that ignites on contact with nitrogen tetroxide (oxidizer); second stage powered by Aerojet-General LR91 rocket engine of 80,000 lbs. thrust
Maximum speed: 15,000 mph / 13,904 knots
Maximum range: 6,300 statute miles / 5,475 nautical miles
Maximum altitude: 620 statute miles / 538 nautical miles
Length: 98 ft. 4 in. (ICBM configuration)
Diameter: 10 ft. (first stage) and 8 ft. second stage (ICBM configuration)
Weight: 201,500 lbs. at launch
