Castor 4B

Thiokol Castor 4B

Mission Profile

The Castor 4B was a single-stage solid-propellant strap-on booster motor developed by Thiokol Chemical Corporation, widely used as a thrust augmentation stage on the Delta launch vehicle family to increase first-stage liftoff performance for heavier payloads. An upgraded derivative of the earlier Castor 4 with improved propellant formulation and higher thrust, it was first used in flight in May 1991. The Castor 4B's role in the Delta II family was substantial, providing the additional thrust needed for maximum-performance missions that required the full nine strap-on booster configuration.