Atlas (rocket)

I

Introduction

Atlas (rocket), family of rockets used primarily as launch vehicles for commercial, military, and scientific satellites. The Atlas rocket was originally designed by the United States Air Force for use as an intercontinental ballistic missile (ICBM), a rocket capable of carrying a nuclear warhead to a target on another continent. Soon after the first Atlas missile launch, the Air Force recognized the rocket’s potential for launching spacecraft. In 1958 an Atlas rocket became the first communications satellite when it broadcast a recorded greeting from President Dwight D. Eisenhower around the world. This broadcast marked the first time a human voice was heard from space. Atlas rockets launched spacecraft for the Mercury program, the first manned American space missions, in the early 1960s, and went on to launch many other space exploration missions. Today Atlas rockets launch artificial satellites for private companies and governments worldwide.

II

Early Atlas Rockets

Conceptual development of the Atlas rocket started in 1946 and construction of the rocket’s components began in the early 1950s. The first Atlas test flight occurred in 1957. One year later an Atlas rocket orbited the Earth carrying Score, an experimental communications system complete with an audio tape machine that broadcast President Eisenhower’s recorded greeting around the world. In 1962 Atlas launched American astronaut John Glenn aboard the Mercury capsule Friendship 7, the first manned American mission to orbit the Earth. Atlas rockets launched three additional manned Mercury missions in 1962 and 1963.

The Atlas rocket used to launch Mercury consisted of one and one-half stages, or rocket engines. After the first several minutes of flight, the lower engines burned out and fell away, leaving the upper stage to lift the craft the rest of the way into orbit. This version of the Atlas measured about 29 m (95 ft) in height. It was fueled by liquid oxygen and liquid kerosene and was capable of launching a 1,400-kg (3,000-lb) capsule into low-Earth orbit—that is, an orbit with an altitude of 2,000 km (1,200 mi) or less.

Atlas rockets have launched many other American space missions. Other major Atlas launches included Mariner 2, the first U.S. planetary probe (to Venus in 1962); Mariner 9, the first Mars orbiter (1971); and Pioneer 11, the first Jupiter-Saturn probe (1973).

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III

Modern Atlas Rockets

In the early 1980s the Atlas family of rockets appeared to face the end of their service as space launchers. At that time, the National Aeronautics and Space Administration (NASA) planned to rely on the space shuttle, a reusable rocket and spacecraft, for missions previously performed by Atlas rockets and other rockets that could be used only once. However, after the space shuttle Challenger exploded in 1986, most satellite launch activity reverted to expendable rockets.

In 1988 the Air Force awarded a contract to General Dynamics to refurbish Atlas rockets to launch its Defense Satellite Communications System III (DSCS III), a series of satellites designed to provide secure voice and data transmission. The first of several such launches took place in 1992. Martin Marietta Corporation (now Lockheed Martin Corporation) purchased the Atlas series rockets from General Dynamics in 1994. Today Lockheed Martin manufactures Atlas rockets to launch commercial, military, and research satellites for private companies and governments worldwide.

Current Atlas production includes the Atlas II, Atlas III, and Atlas V series. Rockets of the Atlas II series measure approximately 47 m (154 ft) tall and weigh up to 234,000 kg (516,000 lb) when fully fueled. Much more powerful than their predecessors, Atlas II rockets consist of two and one-half stages—a one and one-half-stage propulsion system similar to the earlier Atlas rockets and an upper stage. Atlas II’s upper stage, called the Centaur, is one of the most powerful upper stages in use today. It burns liquid oxygen and liquid hydrogen. The largest Atlas II, Atlas IIAS, also includes four strap-on boosters. Atlas IIAS can launch 8,600 kg (19,000 lb) into low-Earth orbit or 3,070 kg (6,760 lb) into geostationary orbit. Satellites in geostationary orbit circle the Earth at an altitude of 35,700 km (22,200 mi), appearing to stay in one place because their orbit speed matches the rate of the Earth’s spin.

Rockets in the Atlas III series measure up to 53 m (174 ft) long and weigh more than 220,700 kg (486,500 lb) when fully loaded. Atlas III rockets consist of two stages. A new, single-stage main engine replaces the one and one-half stage propulsion system of the earlier Atlas rockets. It burns liquid oxygen and liquid kerosene fuel. The Centaur stage of the most powerful Atlas III, Atlas IIIB, is 1.7 m (5.6 ft) longer than the Centaur used in the Atlas II. Rockets in the Atlas III series can launch up to 4,500 kg (9,920 lb) into geostationary orbit.

The first Atlas V is scheduled to launch in late 2001. The largest and most powerful rockets in the Atlas family, Atlas V rockets measure up to 62 m (204 ft) tall and weigh more than 333,000 kg (735,000 lb) when fully loaded. The first stage of the Atlas V rockets will be a single-stage Atlas main engine, a newly developed booster engine with up to five strap-on rocket boosters. Its Centaur upper stage is virtually identical to the Centaur used on Atlas IIIB rockets. The Atlas V rockets can lift up to 8,200 kg (18,000 lb) into geostationary orbit.

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