The Atlas III (known as the Atlas II-AR (R for Russian) early in development [3]) was an American orbitallaunch vehicle,used in the years between 2000 and 2005.[4] It was developed from the highly successful Atlas II rocket and shared many components.[1] It was the first member of the Atlas family since the Atlas A to feature a "normal" staging method,compared to the previous Atlas family members,which were equipped with two jettisonable outboard engines on the first (booster) stage (with a single center engine serving as the sustainer). The Atlas III was developed further to create the Atlas V.
The Atlas III was developed from the highly successful Atlas II rocket and consisted of two stages. The first stage was heavily modified from Atlas II,and the upper stage remained the Centaur. The AtlasIII was produced in two versions. The baseline was the AtlasIIIA,but the AtlasIIIB,featuring a stretched twin-engine version of the Centaur upper stage,was also produced.[2]
The first stage of Atlas III was derived from that of Atlas II. Its propellant tanks were 3m (9.8ft) longer than those on AtlasII,making more propellant available to the engine and increasing the vehicle's performance. Over 183 tons of RP-1 and liquid oxygen propellants were stored inside the tanks. The storied "stage-and-a-half" system used on all Atlas rockets from Atlas B to AtlasII,where three engines are lit on the ground,and two of them are dropped away during flight,was replaced by a single Russian RD-180 engine,boasting higher thrust and efficiency than previous engines. Unlike AtlasII and the later Atlas V,there was no option for solid rocket motors to be added to the first stage. 12 retrorockets were mounted on the stage to aid in separating it from Centaur during flight.[1]
The first stage continued to make use of the balloon tank technology of previous Atlas rockets,where the stainless-steel tank walls were thin and had to remain pressurized in order to not collapse. The tanks were pressurized with helium gas,which was stored in 13 bottles throughout the stage.[1]
The first stage was unchanged between the Atlas IIIA and IIIB variants.
The Atlas Roll Control Module,which contained several hydrazine thrusters and helped maintain roll stability on AtlasII,was removed on the AtlasIII. The dual-chamber RD-180 was therefore responsible for gimballing to control the rocket's pitch,yaw,and roll during first-stage flight.[1]
The second stage of Atlas III was the Centaur. It was powered by one or two Pratt & Whitney (later Aerojet Rocketdyne) RL-10 engines, fueled by liquid hydrogen and liquid oxygen. Compared to the AtlasII, the added thrust and efficiency of the first stage of AtlasIII allowed for one RL-10 engine to be removed from Centaur, and AtlasIII was the first Atlas to offer a single-engine Centaur. The engines of a dual-engine Centaur were mounted directly on the aft propellant tank bulkhead, whereas the engine on a single-engine Centaur was mounted on a specially made beam connected to those existing dual-engine mounts. The single-engine Centaur featured an RL-10A-4-1 engine with a 51cm (20in) extendible nozzle, which increased the engine's thrust by 1.4kN and specific impulse by 6.5 seconds.[1]
Centaur hosted the vehicle's avionics and flight computers and controlled the entire flight. The RL-10 engine on the single-engine Centaur featured electromechanical gimballing, as opposed to the hydraulic gimballing on other variants.[1]
The tanks of Centaur were balloon tanks like the first stage, made from stainless steel. PVC foam insulation was installed on the outside of the tank walls to help limit propellant boiloff inside the tanks.[1]
Two variants of Centaur flew on Atlas III:
Centaur II, which flew on Atlas IIIA, was only offered with one RL-10 engine. This stage is nearly identical to the CentaurII of AtlasII, with the only major difference being only one engine attached.[5]
Centaur III, aka Common Centaur, which flew on AtlasIIIB, was available with one or two RL-10 engines. Its tanks were 1.68m (5ft 6in) longer than those of the Centaur II, offering a substantial increase in propellant capacity and increasing the stage's performance.[1] This stage would later fly on the Atlas V.[5]
Flying a mission on an Atlas IIIB with a dual-engine Centaur provided a nearly 400kg boost in payload capability to geostationary transfer orbit compared to using a single-engine Centaur.[1]
An Extended Mission Kit (EMK) was available for Centaur. This kit included additional helium bottles, radiation shielding on the LOX tank and electronics, and thermal paint to maintain stable temperatures for electronics.[1]
Payload fairing
Two aluminum fairing models (which previously flew on the Atlas II) were available for the AtlasIII, both with a 4.2m (14ft) diameter:[1][5]
Large, with a height of 12.2m (40ft) and a mass of 2,087kg (4,601lb)
Extended, with a height of 13.1m (43ft) and a mass of 2,255kg (4,971lb)
Fairing selection had a small but noticeable impact on the performance of AtlasIII. For example, when going to a 185km (115mi) low Earth orbit, flying with the Extended payload fairing would reduce the payload capacity by around 45kg (99lb) compared to flying with the Large payload fairing.[1]
Both fairing options were still flown on the Atlas V rocket until 2022.[6] For the AtlasV, these fairings were part of the 400-series of that rocket, and a further extended option ("Extra Extended") was available.[1][7]
The GX rocket, formerly under development by Galaxy Express Corporation, was originally intended to use the boost stage of the Atlas III, provided by Lockheed-Martin, and a newly designed upper stage. It would have launched from the Tanegashima Space Center, south of Kyūshū, Japan. In December 2009, the Japanese government decided to cancel the GX project.[11]
The Atlas III first stage was considered as a Removable Propulsion Module (RPM) for the Starbooster concept. [12]
↑"Atlas IIIA". Encyclopedia Astronautica. Archived from the original on 1 July 2013. Retrieved 8 March 2007.
123Rudman, Thomas J.; Austad, Kurt L. (December 2002). The Centaur Upper Stage Vehicle(PDF). 4th International Conference on Launcher Technology - Space Launcher Liquid Propulsion. Liege, Belgium: Lockheed Martin Astronautics. Archived(PDF) from the original on 13 November 2025. Retrieved 16 July 2022.
↑Plain, Charlie (December 2025). "Out With a Bang!". nasa.gov (Press release). NASA. Archived from the original on 14 February 2005. Retrieved 6 June 2020. This article incorporates text from this source, which is in the public domain.
This template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future
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†† - no new orders accepted and production stopped
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