Minuteman Missile Historic Resource Study

Liquid-Fuel Intercontinental Ballistic Missiles: Atlas and Titan

One of the most important early problems tackled by missile developers working with the WDD was that of fueling the rocket, or more accurately, of finding a fuel that would be effective in flight, but also safe on the ground. Early ICBMs were powered by a highly volatile liquid-fuel mixture of liquid oxygen and kerosene or nitrogen tetroxide. [60] This mix powered both the early ICBMs—Atlas and Titan. Problems with liquid fuel were evident from the early days of development and posed challenges and safety issues for on-site crews. Liquid fuel was heavy and unstable and dangerous to handle and store. Other practical issues included the need to store the fuel outside the missile, loading the fuel just prior to launch. This complication made it necessary to develop a safe system of pumps, storage tanks, and mixing chambers to store the fuel.

The other option for powering the new ICBMs was solid fuel, which was only in the beginning stages of research and development when the Atlas missile program began in earnest in 1954. [61] Given the mission of the WDD to produce a working ICBM in the shortest possible timeframe, liquid fuel was the only viable option for the first ICBMs. [62]

Atlas

The Atlas missile was the first ICBM activated by the Air Force. The development and deployment of this ICBM was the result of a massive, fast-tracked effort on the part of the WDD, the ARDC, and its contractors. By December 1955, one year after the Atlas development program was taken over by the WDD, there were fifty-six contractors working on the Atlas program. [63] By 1957 the list of contractors had grown to 157.

Early specifications for the Atlas missile required a 240,000 pound vehicle with two 135,000 pound booster engines and a sixty thousand pound sustainer engine. Although Atlas development utilized certain elements of existing technology, including propulsion systems designed for the canceled Navaho cruise missiles, the Atlas design was state-of-the-art. [64] The Atlas missiles had to be pressurized while on alert, because the stainless steel shell was so thin—a requirement of flight—that only pressure kept it in place while on the ground. If the missile was fueled and launched, the liquid oxygen fuel inside the missile created the necessary pressure to hold the missile's shape. This system allowed for a much lighter airframe, but required continual maintenance to prevent structural collapse. In layman's terms, an unpressurized Atlas missile might best be understood as a deflated balloon. [65]

The first Atlas ICBM was tested successfully on 17 December 1957 and the first Atlas missile went on alert at Vandenberg Air Force Base in California on 31 October 1959. [66] Atlas missile crews were in place at numerous air force bases by 1961, and a year later, twelve Atlas squadrons were on alert, in addition to the missile at Vandenberg. [67]

Three generations of the Atlas missile were deployed by the Air Force—Atlas D, E, and F. Technological advances would be seen in each new generation of Atlas produced, most notably through improvements in thrust, launch, and guidance system. As the Atlas is the direct predecessor of the Minuteman missile, some key details of the progression of this system will shed useful light on the Minuteman's origins. [68]

Atlas D

• First deployed in 1959.

• First deployed at Vandenberg Air Force Base in California, F.E. Warren Air Force Base in Wyoming, and Offutt Air Force Base in Nebraska.

• F.E. Warren Air Force Base had two squadrons with six missiles. Vandenberg Air Force Base and Offutt Air Force Base had three squadrons for a total of nine missiles at each base.

• Possessed 360,000 pounds of thrust and measured eighty-two feet long.

• Propelled by a one-and-one-half stage liquid-fuel rocket.

• The missile was stored horizontally and housed aboveground in soft complexes with gantries or "coffins."

• To launch, the missile roof was pulled back, the missile raised to a vertical position, fueled, and fired.

• The launch sequence began when the two boosters and the sustainer engine were lit. Two small vernier engines above the sustainer ignited shortly after lift-off (2.5 seconds). Booster engines burned once in flight, and these, along with the turbo-pumps, were discarded quickly once a signal was received from the ground station. The sustainer engine was the last to extinguish and the vernier engines were responsible for course and velocity corrections. [69]

• Three missiles, a control center, and a radio guidance system were controlled by a single missile crew.

• The radio guidance system was accurate to one and one-half miles and could only control one missile at a time.

• Armed with a one-megaton thermonuclear warhead.

• Range of approximately 6,400 miles.

Atlas E

• First deployed in 1961.

• First deployed at Fairchild Air Force Base in Washington, Forbes Air Force Base in Kansas, F.E. Warren Air Force Base, and Vandenberg Air Force Base.

• Nine missiles comprised a squadron. Fairchild, Forbes and F.E. Warren Air Force Bases had three squadrons. Vandenberg had one squadron.

• Atlas E was more powerful than Atlas D, with 389,000 pounds of thrust.

• Range of approximately 9,400 miles.

• Controlled by a self-contained, automatic inertial guidance system accurate to within one and one-half miles.

• Armed with a one-megaton thermonuclear warhead.

• Missiles were stored in aboveground coffins.

• To launch, the Atlas E was raised to a vertical position and fueled.

• A separate launch crew staffed each missile site.

Atlas F

• Placed on alert in 1962.

• First deployed at Schilling Air Force Base in Kansas, Lincoln Air Force Base in Nebraska, Plattsburg Air Force Base in New York, Altus Air Force Base in Oklahoma, Dyess Air Force Base in Texas, and Walker Air Force Base in New Mexico.

• Twelve silos and a support base formed a squadron.

• One squadron was deployed at each of the six bases mentioned above.

• More powerful than Atlas E, with 390,000 of thrust.

• Range of approximately 9,400 miles.

• Armed with a one-megaton thermonuclear warhead.

• Controlled by self-contained, automatic inertial guidance system accurate to within one and one-half miles.

• Missile stored vertically in hardened underground silo.

• Missile raised to surface on elevator during launch sequence.

• A single missile was housed in the Atlas F silo with an adjoining underground launch control facility. [70]

By 1962 the number of Atlas missiles scattered across the country had grown to 126. [71] Though first, the Atlas was never intended to be the only American strategic missile. It was destined to be eclipsed in its role by the more advanced Titan and Minuteman systems to follow. The last Atlas missile was launched at Vandenberg on 24 March 1995. Rather than a nuclear payload, this Atlas E carried a Defense Meteorological Weather Satellite to orbit. [72]

Titan I

The development of the Titan missile resulted from the decision of the WDD and the Eisenhower administration in 1955 to move forward with the development of a second ICBM, in case the Atlas ran into delays. [73] The WDD developed Titan ICBMs concurrently with the Atlas. [74] Titan I had several distinct advantages over the Atlas, including greater range, speed, and warhead size. As with the information detailed on the Atlas above, some key moments and statistics for the Titan program will help provide context for the more exhaustive Minuteman discussion to follow. Features of the Titan I include:

• Combat crews began working at the Titan I missile sites in 1961.

• First Titan I went on alert in 1962 at Lowry Air Force Base in Colorado.

• In 1962 Titan I ICBMs were deployed in six squadrons having three missiles each.

• Deployments were located at Beale Air Force Base in California, Ellsworth Air Force Base in South Dakota, Larson Air Force Base in Washington, Mountain Home Air Force Base in Idaho, Vandenberg Air Force Base in California, and Lowry Air Force Base.

• Measured ninety-eight feet long and possessed a self-supporting frame.

• Three missiles were housed in adjacent silos and controlled by a single launch control facility, thereby making this system more efficient for the Air Force to operate.

• A single Titan I, with a range of over 6,300 miles, was capable of launching fifteen minutes after the order was received.

• Two additional Titan I ICBMs in the squadron launch at seven-and-a-half-minute intervals after the first missile.

• Propellant consisted of a two-stage liquid oxygen and kerosene system.

• Missile housed in a 165-foot-deep silo and was raised to the surface for launch.

• Armed with a single four megaton thermonuclear warhead.

• Used to successfully test a "hot" launch directly from the silo. The ability to launch directly from the silo without raising the missile to the surface resulted in a quicker launch time. [75]

Titan I remained on alert for only three years—from 1962 until 1965—before being replaced by the Titan II.

Titan II

Titan II was approved for development in 1959 and was designed to correct some of the perceived shortcomings of the Titan I system. Fifty-four Titan II ICBMs, deployed at Davis-Monthan Air Force Base in Arizona, Little Rock Air Force Base in Arkansas, and McConnell Air Force Base in Kansas, remained on active duty until deactivation began in 1982 and was completed in 1987. [76]

Features of Titan II include:

• Improved inertial guidance and fuel systems.

• Armed with a nine megaton thermonuclear warhead.

• A maximum range of nine thousand miles.

• Employed storable propellants.

• Ability to launch in two minutes.

• Improved rocket engines featured 432,000 pounds of thrust in the first stage and a second stage with 100,000 pounds of thrust.

• Based on the successful tests conducted with Titan I, the Titan II could be launched directly from the silo without having to be raised to the surface.

• Squadrons consisted of nine missiles, each in an underground silo and controlled by a neighboring underground Launch Control Center.

• Two officers and two enlisted combat crew staffed the Launch Control Facility. Beginning in 1978 the first female crewmembers served on the crew of Titan II, setting the precedent for the later mixed-gender Minuteman crews.

As the above discussion demonstrates, both the Atlas and Titan programs offered significant improvements over the manned strategic weapons systems that preceded them. However, each had its shortcomings. The Minuteman was designed to overcome these deficiencies. It is to the Minuteman itself that we next turn.