ORBUS

HTPB Solid Rocket Motor

The ORBUS upper stage motor was developed by Pratt & Whitney's Chemical Systems Division (CSD, owned by UTC) in the late 1980s. It flew on the IUS (Inertial Upper Stage) and TOS (Transfer Orbit Stage) orbit insertion stages.

The ORBUS-21 & ORBUS-6E first flew on the IUS on Titan-34D in 1982, followed by flights on the Titan-402A, 402B and Shuttle from 1983 to 1999. ORBUS-7S and 21S were upper stages on Titan Commercial in 1990, followed in 1992 by a ORBUS-21 motor on the TOS-21H upper stage on Commercial Titan's Mars Observer launch, and in 1993 on Shuttle STS-51. ORBUS-21D was the last version to fly on the Athena I & II launch vehicles up to 2001.