ICBM Evolutions

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. By 1962 the number of Atlas missiles scattered across the country had grown to 126; less than three years later the Atlas was retired from ICBM service.

The development of the Titan missile resulted from the decision of the Eisenhower administration in 1955 to move forward with the development of a second ICBM, in case the Atlas ran into delays. The Titan was developed concurrently with the Atlas. Titan I had several distinct advantages over the Atlas, including greater range, speed, and warhead size but remained on alert for only three years–from 1962 until 1965–before being replaced by the Titan II. The 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.

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.

During the course of the construction of the Minuteman system, technology and war planning policy led to changes within the design of silos and control center facilities.

Evolution of ICBM Launch Facilities

Just as ICBMs evolved, so did their launch facilities. The first Atlas missiles were stored
upright on launch pads, where they were vulnerable to attack. Later, the missiles were
kept in horizontal, concrete "coffins" and raised vertically before launch. Eventually, the Air
Force moved ICBMs to underground silos; elevators lifted them to the surface for launch.
Titan II and Minuteman were the first ICBMs launched directly from underground silos.

Evolution of Minuteman Launch Control Centers

The first Minuteman launch control centers, such as Delta One, were dependent on life-support equipment in the above-ground launch control facility support building. In later versions, the Air Force buried the life-support equipment underground to help it better withstand a nuclear attack.

Evolution of Minuteman Silos

The Air Force also redesigned the launch facilities to improve survivability. The power
supply unit (shown to the right of each silo) was buried deeper underground, and encapsulated in hardened concrete. The Delta Nine silo represents the earliest configuration (shown in the left illustration).