Antares, known during early development as Taurus II, is an expendable launch system developed by Orbital Sciences Corporation and the Pivdenne Design Bureau to launch the Cygnus spacecraft to the International Space Station as part of NASA's COTS and CRS programs. Able to launch payloads heavier than 8,000 kg (18,000 lb) into low Earth orbit, Antares is the largest rocket operated by Northrop Grumman. Antares launches from the Mid-Atlantic Regional Spaceport and made its inaugural flight on April 21, 2013. Antares 100 was retired in 2014 and series 200 was retired in 2023 due to component unavailability. As of January 2024 Antares 300 is under development.

Castor is a family of solid-fuel rocket stages and boosters built by Thiokol and used on a variety of launch vehicles. 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.