The Atlas ballistic missile was originally a U.S. intercontinental ballistic missile, but, as it became obsolete for its military application of delivering a reentry vehicles containing a warhead containing a nuclear weapon, has been used extensively as a space launch vehicle. It was the primary booster for the orbital flights of Project Mercury. An Atlas family of launch vehicles remains in commercial production, although virtually none of the original technology is used today; the distinguished name lives on.
Design concepts and development
It introduced techniques for saving critical weight in the booster, allowing larger payloads. Perhaps the most counterintuitive was the balloon tank, which held the fuel and oxidizer inside extremely thin metal walls. The walls would collapse had the tanks not been pressurized.
A second technique, called stage and a half, did not release entire burned-out stages as did later rockets, but took off on three engines, and then dropped off two of them when adequate speed was gained. While this technique is no longer used in the Atlas family of commercial launch vehicles, a modern parallel is the way the solid rocket boosters of the Space Shuttle drop off after they exhaust their propellant.
|Atlas A||Booster engine only; 600 mile test range|
|Atlas B||Full engine fit|
|Atlas C||Near-operational procedures test|
Use as an intercontinental ballistic missile
Atlas family missiles were the first generation of United States ICBMs, which taught a great deal about what was needed in a more mature weapon. The first operational version, the Atlas D, went operational in 1959, and the last model, Atlas F, were retired from ICBM duty by FY 1968.
Perhaps their greatest limitation was the need to fill their oxidizer tanks with cryogenic liquid oxygen, a procedure that took several hours.
|Atlas D; PGM-16D/CGM-16D [Note 1]||Deployed above ground in small groups||radio-inertial guidance|
|Atlas E; CGM-16E||Greater dispersion, but stored horizontally and needed significant setup time.||inertial guidance, Improved engine|
|Atlas F; HGM-16F [Note 2]||Vertical underground storage but had to be raised from silo for launch.||inertial guidance, Improved engine|
- Note 1: "C" prefix for semi-hardened "coffin" storage
- Note 2" "H" prefix for hardened underground silo