Thiokol's Star family of space motors provides propulsion for spacecraft and launch vehicle upper stages.  The Star number for each motor indicates its approximate principal diameter in inches, while the letter designations are used to denote configurations tailored to a particular set of needs.  The Star 63 currently comes in two models, the D and the F.

The Star 63D perigee motor has successfully delivered payloads to elliptical transfer orbit.  Given a range of propellant loads, the Star 63D payload capability ranges from 3,080 to 4,588 pounds at a constant velocity of 8,012 feet per second.   The Star 63F perigee motor has successfully completed development and qualification and is in production.  It can be offloaded to a propellant weight of 7,305 pound.  Motor components are of proven design features and material, thus maximizing reliability.