The Atlas II was a medium sized expendable launch system that was manufactured by Lockheed Martin. The main purpose for the Atlas II was to launch payloads to LEO (low earth orbit) and GTO (Geosynchronous transfer orbit). There are three different models for the rocket; there is the Atlas II, Atlas IIA, and the Atlas IIAS. The maximum capacity the Atlas II can hold when reaching low earth orbit is 6,580kg (14,506lbs), while at Geosynchronous transfer orbit the rocket can only hold a capacity of 2,810kg (6,194lbs). The Atlas II was first launched in December of 1991. The total number of launches the Atlas II had was 63. Which of 63 were a success making the Atlas II the most reliable expendable launch system in aerospace history. The Atlas II had 10 successful launches, while the Atlas IIA and Atlas IIAS had a total 53 successful launches (23 from Atlas IIA and 30 from the Atlas IIAS). The length of the Atlas II was 47.4 meters tall (155.5 feet). The diameter of the rocket was 3.05m (10 feet). The Atlas II stage I used a MA-5A that produced 2,159kN of thrust (485,362 pounds of thrust), the rocket also had two boosters and a sustainer. The Atlas II had an interstage assembly and had a dual engine centaur as well. The Atlas IIA used an MA-5A and a RS-56-OBA, while Stage I of the Atlas IIA used a RS-56-OSA that produced 2,093kN of thrust (470,682lbs). The Atlas IIA stage II centaur used a RL-10A-4 engine that produced 85kN of thrust (41,592lbs). The Atlas IIAS on the other hand used a Castor IVA engine that produced 498kN of thrust (112,000lbs). The Atlas IIAS stage I used a RS-56-OBA that also produced 2,093kN of thrust (470,682lbs). Stage II used a RS-56-OSA that produced 386kN of thrust (86,844 lbs). Last but not least, Stage III used a centaur RL-10A-4 engine that produces 185kN of thrust (41,592 lbs). The last launch of the Atlas II was in August of 2004.