CASTOR 30B

CASTOR 30B is the exact solid upper-stage motor used as the second stage of Antares 120 and a variant of the CASTOR 30 family. Northrop Grumman's CASTOR Motor Series catalog describes it as a production motor modified from CASTOR 30, primarily through a propellant change and a longer nozzle; it is designed to operate as a second or third stage. The catalog gives a 169.9-inch length, 89,090 lbf (396.29 kN) maximum vacuum thrust, 67,370 lbf (299.68 kN) average vacuum thrust, 300.6 seconds specific impulse, and 126.7 seconds burn time, with TP-H8299 HTPB polymer propellant containing 20% aluminum. NASA's Orbital-2 press kit identifies an ATK CASTOR 30B as the Antares second-stage motor. Lifecycle remains unknown: the catalog calls the motor flight-proven but does not establish current production or universal in-service status, so historical Antares 120 use is not treated as motor-wide retirement.