NW043 Atlas D ICBM - First US operational ICBM

In 1955 Convair won the prime contract for Atlas ICBM.The liquid oxygen and kerosene vehicle was designed to carry a thermonuclear warhead over 7000 miles. The Atlas was unique in its “stage and half” design in which two of its main engines were shed to reduce weight after two minutes of flight, while the central sustainer continued to burn. In order to minimize sustainer tank weight (used also for booster engines), Convair employeed balloon construction. Flights of Atlas began on June 11, 1957, with the launch of Atlas A powered by booster alone. In November 1958, an Atlas B reached full design range, and the operational Atlas D was deployed in 1960.
Atlas D served until 1964, when Atlas D's were taken off alert and shipped to Norton AFB, California, where retired Atlas ICBMs were stored for future use as launch vehicles in research a development programs.