U.S. Strategic Missile and Armament Systems (1950s60s) (continued)
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.  This mix powered both the early ICBMsAtlas 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.  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. 
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.  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.  The Atlas missiles had to be pressurized while on alert, because the stainless steel shell was so thina requirement of flightthat 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. 
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.  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. 
Three generations of the Atlas missile were deployed by the Air ForceAtlas 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. 
By 1962 the number of Atlas missiles scattered across the country had grown to 126.  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. 
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.  The WDD developed Titan ICBMs concurrently with the Atlas.  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:
Titan I remained on alert for only three yearsfrom 1962 until 1965before being replaced by the 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. 
Features of Titan II include:
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.
Last Updated: 19-Nov-2003