Atlas II

The Atlas II launch vehicle program has been managed by the Atlas Program Office at the Space and Missile Systems Center, Los Angeles AFB, California.

Atlas II is a two-and-a-half stage vehicle, and has been primarily used to support the Defense Satellite Communications System (DSCS) III program. The Atlas II is capable of lifting approximately 14,500 pounds into low earth orbit and 6,500 pounds to a geosynchronous transfer orbit. The Atlas II was a modification of the Atlas G launch vehicle. The length of the Atlas II has been stretched nine feet from the Atlas G configuration to provide more propellant capacity. Propulsion is provided by a Rocketdyne liquid rocket engine set, which consists of two booster engines and one sustainer engine. All three engines provide 488,500 pounds of thrust. The Centaur upper stage has been increased three feet from its original design. It is powered by two Pratt & Whitney liquid rocket engines which provide a total of 33,000 pounds of thrust.

General Dynamics Space Systems Division was under contract to the Air Force to build nine Atlas IIs (with options to buy more) to be used for DSCS III satellite launches and other payloads. The contract, valued at $442 million, was awarded in June 1988 and ran through December 1997. The first US Air Force Atlas II was launched 10 February 1992.

Atlas IIA Commercial Launch Vehicle

The Atlas IIA is the commercial derivative of the Air Force Atlas ll. Atlas IIA is capable of lifting payloads in the 6,500-pound class to a geosynchronous transfer orbit. The Atlas IIA booster has been stretched nine feet, and the Centaur upper stage is three feet longer than an Atlas I vehicle. Atlas IIA uses a Rocketdyne MA-5A stage-and-a-half propulsion system with two booster engines and one sustainer engine burning a combination of liquid oxygen and RP-I propellant. The Atlas IIA provides total thrust of 474,000 pounds.

Centaur D-1A, also a General Dynamics Space Systems vehicle, is powered by two Pratt & Whitney RL-10A-4 turbopump-fed engines burning liquid oxygen and liquid hydrogen. The two engines produce a total thrust of 41,600 pounds, and are uprated versions of the previously flown RL-10A3-3A engines with extendible nozzles. First flight of this version of Centaur occurred in June 1992 on the Intelsat K mission. The overall Atlas IIA length is 156 feet with large payload fairing, the Atlas length is 82 feet, and the Centaur length is 33 feet. The diameter is 10 feet, and gross liftoff weight is 413,276 lb. with the large fairing.

Atlas IIAS Commercial Launch Vehicle

The Atlas IIAS is an uprated version of the Atlas IIA, with capabilities for meeting even higher payload requirements. The fourth variant in the Atlas family, Atlas IIAS is capable of lifting payloads in the 7,000 to 8,000-pound class range to geosynchronous transfer orbit. Four strap-on solid rocket motor boosters have been added to the booster stage to increase liftoff thrust and payload lift capability. The Atlas IIAS booster uses a Rocketdyne MA-5A stage-and-a-half propulsion system with two booster engines and one sustainer engine burning a combination of liquid oxygen and RP-1 propellant. The MA-5A system provides a total liftoff thrust of 423,500 pounds. The four solid strap-ons are Castor IVA solid rocket boosters, each 37 feet long and 40 inches in diameter, providing an average thrust of 97,500 pounds. Two of the four solid rocket boosters ignite at liftoff, contributing an additional 197,000 pounds of thrust. Total thrust at liftoff is 620,500 pounds. The second pair of solid rocket boosters fires during flight after the first pair burns out, to control acceleration forces. The IIAS Centaur upper stage, is identical to the Centaur flown on IIA.