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.