ATLAS ROCKET

booster for space vehicles, particularly the U.S. Mercury spacecraft series, designed originally as an intercontinental ballistic missile (ICBM). Atlas is equipped with three enginestwo boosters that are jettisoned after about 2 1/2 minutes of operation and a sustainer that operates until orbital velocity is attained. Atlas can lift about 5,800 pounds (2,600 kg) to about a 350-mile (560-kilometre) orbit. Coupled with Agena, the combined AtlasAgena rocket is used for launching lunar and planetary probes, as well as Earth-orbiting satellites, such as Seasat, where the Agena is also the spacecraft. AtlasCentaur, or Centaur, combines the first-stage Atlas, which burns kerosene, with a second stage fueled with liquid hydrogen; it was the first rocket to use liquid hydrogen as fuel.