Atlas III was an evolutionary step between Lockheed Martin’s Atlas IIA(S) and Atlas V. The rocket was the first Atlas to be powered by the twin-chambered, Russian RPO Energomash RD-180 LOX/kerosene engine. It was also the first Atlas to test the new Single Engine (Common) Centaur stage powered by a single Pratt & Whitney RL10A-4-2 LOX/LH2 engine.
Shorn of three liquid thrust chambers, four solid rocket boosters, and 14,200 parts compared to Atlas IIAS, Atlas III orbited heavier payloads for less money.
Atlas IIIA, the initial version that first flew in 2001, could boost 4 metric tons into geosynchronous transfer orbit (GTO) with a dual engine Atlas IIA(S) Centaur stage. Atlas IIIB could do the same with a Single Engine Centaur (SEC) stage, or could put 10.7 tons into low earth orbit with a Dual Engine Centaur (DEC) stage.
Both Atlas III stages used 3.05 meter diameter stainless steel balloon-tanks. Compared with Atlas IIA(S), the Atlas III LOX tank and interstage adapter were stretched by 3.05 meters to a length of 28.91 meters.
RD-180 was derived from the four-chamber RD-170 engine used by the Soviet Union’s Energia and Zenit boosters. RD AMROSS, a joint venture of Russia’s NPO Energomash and UTC Pratt & Whitney, paid for development and purchase of the engines. Each RD-180 cost $10 million. The engine produced 390 tons of thrust at sea level and up to 423 tons of thrust in vacuum.
For Atlas III missions, the engine throttled up and down in a 40-92% range, providing 151,352 kfg to 348,108 kgf (sea level) thrust. The engine’s twin thrust chambers were supplied by a single turbopump running on a LOX-rich preburner staged combustion cycle. The chambers could gimbal +/- 8 degrees to provide pitch, yaw, and roll control.
The old Atlas booster package was replaced by a fixed thrust structure that supported two snub-nose “bottle fairings”. These fairings shrouded the engines and housed six of 13 helium bottles used for stage pressurization.
Also read: Space Launch Report: Ariane 5 Data Sheet
Atlas IIIA first flew from Cape Canaveral’s Space Launch Complex (SLC) 36B in May 2000. Atlas IIIB performed its first launch from the same pad in March 2002. The last of six Atlas III rockets (all successful) lifted off on February 3, 2005.
Vehicle Configurations
| LEO Payload (metric tons) (185 km x [1] 28.5 deg [2] 98.6 deg) | GTO Payload 185 x 35786 km x 27 deg 1800 m/s from GEO* (metric tons) | Earth Escape Payload C3=0 km^2/s^2 (metric tons) | Configuration | LIftoff Height (meters) | Liftoff Mass (metric tons) | |
| Atlas IIIA | 8.69 t [1] 6.90 t [2] | 4.11 t | 3.0 t | Single Stage Atlas + Centaur II + LPF | 51.9 m | 221.00 t |
| Atlas IIIB (SEC) | N/A | 4.19 t | N/A | Single Stage Atlas + SEC + LPF | 54.5 m | 225.21 t |
| Atlas IIIB (DEC) | 10.76 t [1] 9.00 t [2] | 4.61 t | 3.25 t | Single Stage Atlas + DEC + LPF | 54.5 m | 225.23 t |
Vehicle Components
| Single Stage Atlas (Lockheed Martin) | Single-Engine Centaur II (Lockheed Martin) | Single Engine Common Centaur | Dual Engine Common Centaur | Interstage Adapter (Lockheed Martin) | |
| Diameter (m) | 3.05 m | 3.05 m | 3.05 m | 3.05 m | 3.05 m |
| Length (m) | 28.91 m | 10.06 m | 11.89 m | 11.74 m | 4.45 m |
| Propellant Mass (tons) | 183.2 t | 16.93 t | 20.83 t | 20.83 t | |
| Total Mass (tons) | t | 18.65 t | 22.76 t | 22.94 t | 0.47 t |
| Engine | RD-180 | RL-10A-4-1 | RL10A-4-2 | RL10A-4-2 | |
| Engine Mfgr | NPO Energomash | Pratt & Whitney | Pratt & Whitney | Pratt & Whitney | |
| Fuel | RP-1 | LH2 | LH2 | LH2 | |
| Oxidizer | LOX | LOX | LOX | LOX | |
| Thrust (SL tons) | 390.25 t | ||||
| Thrust (Vac tons) | 423.39 t | 10.12 t | 10.12 t | 20.23 t | |
| ISP (SL sec) | 311.3 s | ||||
| ISP (Vac sec) | 337.8 s | 450.5 s | 450.5 s | 450.5 s. | |
| Burn Time (sec) | 184 s | 754 s | 928 s | 464 s | |
| No. Engines | 1 (2 Chambers) | 1 | 1 | 2 |
Vehicle Components, Cont’d
| Large Payload Fairing | Extended Payload Fairing | |
| Diameter (meters) | 4.2 m | 4.2 m |
| Length (meters) | 12.2 m | 13.1 m |
| Mass (tons) | 2.09 t | 2.26 t |
