The Star 48 is the largest of a family of solid rocket motors used by many space propulsion and launch vehicle stages, almost exclusively as an upper stage. It was developed primarily by Thiokol Propulsion and after several mergers, is manufactured by Northrop Grumman’s Space Systems division. A Star48B stage is also one of the few man-made items sent on escape trajectories out of the Solar System, although it is derelict since its use. The Star48B variant was the PAM-D upper stage used on the retired Delta II rocket.

The Star 48 has been used as an upper stage in three- and four-stage launch systems.

Overview

The "48" designation refers to the approximate diameter of the fuel casing in inches (122cm); Thiokol had also manufactured other motors such as the Star 37 and Star30. 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 "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, and the "M" stands for the motor.

The Star 48 holds 2,000kg of propellant. The most common use of the Star 48 was as the final stage of the Delta II launch vehicles. Other launchers such as ULA's Atlas 551 have also incorporated the motor but with lower frequency. On board the Space Shuttle, the complete stage (motor plus accessories) was 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 was spin-stabilized. A turntable, mounted in the shuttle payload bay or atop the previous Delta stage, spun the PAM and payload to approximately 60rpm 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 Payload Assist Module that had been used to launch a USA-91 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.

A Star 48B motor 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 also crossed Pluto's orbit in 2015 at a distance of 200million kilometers.

In 2013 a Star 48GXV ("G" for "graphite case") was tested for the Solar Probe Plus mission (which later was renamed to the Parker Solar Probe) but the development was cancelled, in favor of a Delta IV Heavy / Star48BV combination. for the launch in 2018.

A non-spinning, thrust-vectoring version called Star48BV is available, and is the final stage of the Minotaur IV+ launch vehicle.

Star 48B

The Star 48B version has an extra 11 kilograms of propellant more than the regular Star48, for a total of 2011kg. There is a version of the Star48B that is lengthened and also heavier, called the Star48BL.

In operation as a third stage, the Star 48B sits on top of the spin table, and before it is separated, it is spun up to stabilize it during the separation from the previous stage. (see also spin-stabilisation) The Star48B can produce 15,000 pounds of thrust (newtons), with a burn time of 1minute 27seconds.

Star 48B was used on the Atlas-E/F SGS-2, and is the basis for the McDonnell Douglas PAM-D upper stage used on the Delta rocket.

Use on New Horizons

A Star 48B was used on the third stage of the New Horizons spacecraft launch. New Horizons was launched by ULA's AtlasV551 in January 2006, and the Star48B booster was launched along with the New Horizonss spacecraft on an escape trajectory out of the Solar System. The Star48B ignited and burned for 84seconds, taking both on a trajectory past Pluto; however, because the Star48B became derelict and did not have course corrections like the NH spacecraft, it was projected to miss Pluto by hundreds of millions of miles.

New Horizons Star 48B was calculated to arrive at Jupiter six hours before New Horizons, and on October15, 2015, passed through Pluto's orbit at a distance of 213million kilometers (over 1au) distant from Pluto. This was nearly four months after the New Horizons probe did.

Europa Clipper

NASA intended to launch the Europa Clipper using a Star48 on a SpaceX Falcon Heavy. The addition of a Star48 "kick stage" would have allowed the Clipper mission to reach Europa without needing a gravity assist from Venus. This was later removed with an updated Mars gravity assist route.

Star 48 version details

See also

• Star (rocket stage)

• List of artificial objects leaving the Solar System

• Three-stage-to-orbit

References