Thor Agena B

Thor DM-21 Agena B

Mission Profile

The Thor Agena B (Thor DM-21 Agena B) was a two-stage American launch vehicle combining the Thor IRBM first stage with the improved Agena B upper stage, which introduced a restart capability that greatly enhanced orbital mission flexibility for reconnaissance and scientific payloads. Standing 23.5 m tall with a 2.4 m diameter and a liftoff mass of 56 tonnes, it generated 758 kN of first-stage thrust. First flying in October 1960 under the Thor IRBM Program, the Thor Agena B launched the Samos reconnaissance satellites and multiple scientific missions, with its restartable Agena engine enabling the complex orbital maneuvers required for precision reconnaissance satellite operations.