Castor is a family of solid-fuel rocket stages and boosters built by Thiokol (now Northrop Grumman) and used on a variety of launch vehicles.[1] They were initially developed as the second-stage motor of the Scout rocket. The design was based on the MGM-29 Sergeant, a surface-to-surface missile developed for the United States Army at the Jet Propulsion Laboratory.[2][3]
Instead of using a D6AC steel case and PBAN binder like the Space Shuttle SRB, these will use the technology derived from the GEM motors which have carbon composite cases and HTPB binder.[11] The carbon composite design eliminates the factory joint common on all Space Shuttle SRBs.