Star-48B rocket motor
|Country of origin||United States|
|Date||1982 - present|
Star 48 is a type of solid rocket motor used by many space propulsion and launch vehicle stages. It is used almost exclusively as an upper stage. It was developed primarily by Thiokol Propulsion, and is now manufactured by ATK, which purchased Thiokol in 2001.
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. Not surprisingly, the "T" prefix stands for Thiokol, and the following letter refers to the company division that developed the rocket motor. In this case, "E" refers to the Elkton, MD division.
The most common use of the Star 48 was as the final stage of the Space 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 the Payload Assist Module (PAM), 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 Star 48 engine used in the 3rd stage of the New Horizons probe was the first part of the New Horizons mission to reach Jupiter, arriving before the probe. It will eventually cross Pluto's orbit in 2015 at a distance of 200 million kilometers from Pluto.
A Star 48 Payload Assist Module that had been used to launch a GPS satellite in 1993 crashed in the Saudi Arabian desert in January 2001, after its orbit decayed. The unit did not burn up on reentry and was positively identified on the ground.