Atlas(launch Vehicle)

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The Atlas, produced in the 1950s as the first U.S. intercontinental ballistic missile (ICBM), has also served as a launch vehicle. Its design profited from the thermonuclear breakthrough of 1954 that made lighter warheads possible. The Atlas ICBM stood 25.14 m (82.5 ft) high and had a diameter of 3.05 m (10 ft). The lift-off weight was about 120,600 kg (266,000 lb). The range exceeded 14,484 km (9,000 mi).Attached to the base was a gimbal-mounted Rocketdyne LR-105 engine of 25,855-kg (57,000-lb) thrust, which operated in conjunction with two 453-kg-thrust (1,000-lb) swiveling motors used for roll control and vernier adjustment of velocity. Two Rocketdyne LR-89 boost engines burned at takeoff in conjunction with the central sustainer, each 74,844-kg-thrust (165,000-lb) engine operating about 145 seconds before separating. The central engine continued to burn for a total of about 270 seconds. All engines drew their liquid oxygen-kerosene (RP-1) propellants from common tanks in the sustainer. Guidance depended on an inertial system that deflected the main engines in conjunction with the two roll jets.Two launchings of Atlas took place at Cape Canaveral in 1957, but only the third (Aug. 2, 1958) was a complete success, the missile traveling about 4,023 km (2,500 mi) downrange. The operational Atlas-D was flight-tested from the Pacific Test Range in California, between April and August 1959, and improved versionsÑAtlas E and FÑwere test launched in 1960 and 1961, respectively. Some operational missiles were contained in coffinlike shelters from which they were raised to a vertical position for launch. Increasing concern over launch-site vulnerability led to the construction of underground silos from which missiles would be elevated only for launching.Atlas rockets have played a prominent role in the U.S. space program, both military and civilian, as well. In December 1958 an Atlas main-stage in orbit broadcast a recorded Christmas message by President Eisenhower, and Atlas was responsible for launching America's Mercury program astronauts into orbit. In addition, Atlas launched Lockheed Agena rocket stages for the U.S. Air Force and NASA. Later, the LOM/LHM Centaur stage was mounted atop a modified Atlas D to provide a versatile, high-energy launch vehicle for orbiting a wide range of satellites. After the Space Shuttle Challenger disaster in 1986, interest increased in further developing various stage combinations. In 1993 a vehicle called Atlas 2 was introduced, consisting of several smaller strap-on rockets attached to a large pressure-stabilized booster.