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astronautix.com Atlas IIIB


Family: Atlas. Country: USA. Status: Development. Other Designations: Atlas IIRC; Atlas IIARC.

Atlas IIIB added performance capability complements its sister configuration Atlas IIIA. First flight of the Atlas IIIB is planned for mid-2000, subject to satellite availability. The single-stage Atlas IIIB booster is the same as Atlas IIIA The Lockheed Martin manufactured Centaur upper stage is powered by two Pratt & Whitney RL10A-4-2 turbopump-fed engines burning liquid oxygen and liquid hydrogen. The changes to Centaur for Atlas IIIB are a stretched tank (1.68 m) and the addition of the second engine. Guidance, tank pressurization, and propellant usage controls for both Atlas and Centaur phases are provided by the inertial navigation unit (INU) located on the forward equipment module. Launch Sequence: In a typical Atlas IIIB launch, the vehicle's two RD-180 thrust chambers are ignited shortly before liftoff. Pre-programmed engine thrust settings are used during booster ascent to minimize vehicle loads by throttling back during peak transonic loads/high dynamic pressure region while otherwise maximizing vehicle performance. Just over two minutes into flight, as the vehicle reaches an axial acceleration of 4 g's, the engines begin to throttle back, eventually initiating a constant throttle rate to sustain acceleration at 5.5 g's. Booster engine cutoff occurs approximately three minutes into flight and is followed by separation of Centaur from Atlas. The first Centaur burn lasts about five minutes, after which the Centaur and its payload coast in a parking orbit. During the first burn, approximately eight seconds after ignition, the payload fairing is jettisoned. The second Centaur ignition occurs 27 minutes into the flight, continues for about three minutes, and is followed several minutes later by the separation of the spacecraft from Centaur. Major Suppliers: NPO Energomash / Pratt & Whitney - Atlas RD-180 engines; Pratt & Whitney - Centaur engines; Honeywell - Inertial Navigation Unit; BF Goodrich - Digital acquisition system; SAAB - Payload Separation Systems .


Specifications

LEO Payload: 10,718 kg. Payload: 4,500 kg. to a: Geosynchronous transfer trajectory. Liftoff Thrust: 265,000 kgf. Total Mass: 218,588 kg. Core Diameter: 3.1 m. Total Length: 52.8 m. Launch Price $: 105.00 million. in 2000 price dollars.



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Last update 12 March 2001.
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