Star 48
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The Star 48 is a type of solid rocket motor used by both the Space Shuttle and the New Horizons probe. It is used almost exclusively as an upper stage. It was developed primarily by Thiokol Propulsion, and now manufactured by Boeing.
The "-48" designation refers to the approximate diameter of the fuel casing in inches; Thiokol had also manufactured other motors such as the Star-37 and Star-40. Internally, Thiokol's designation was TE-M-711 for early versions, and TE-M-799 for later ones. Subtypes are given one or more letter suffixes after the diameter number, or a trailing number (i.e., "-2") after the internal designation.
The most common use of the Star-48 is as the final stage of the Shuttle and Delta II launch vehicles. Other launchers have also incorporated the motor, but with lower frequency. In such usage, the complete stage (motor plus accessories) is referred to as PAM, Payload Assist Module, as the Shuttle could only take satellites to Low Earth Orbit. Because Geostationary orbit is much more lucrative, the additional stage was needed for the final leg of the journey. On such missions, the stage is spin-stabilized. A turntable, mounted in the shuttle payload bay or atop the previous Delta stage, spun the PAM and payload to approximately 60 rpm prior to release.
Usually after motor burnout and just prior to satellite release the PAM is de-spun using a Yo-Yo de-spin technique.
A non-spinning, thrust-vectoring version of the Star-48 is available ("Star-48V"), but much less common.
A Star-48 engine used in the 3rd stage of the New Horizons probe will be the first part of the New Horizons mission to reach Jupiter orbit, arriving before the probe. It will eventually cross Pluto orbit in 2015, but will miss the planet itself by 200 million kilometres.
