Athena II

The Athena II is a four-stage rocket, consisting of solid first, second and third stages, and a monopropellant liquid-fuelled fourth stage. The first and second stages are Castor 120s, which are also used on some versions of the Taurus rocket. An Orbus 21D motor was used as the third stage on launches during the 1990s. The fourth stage is an Orbital Adjustment Module, fuelled by hydrazine and propelled by four MR-107 engines, which is used for final insertion.