Payload Assist Module

[Image:PAM-D 1920x1080.ogv|thumb|225px|PAM-D with the Phoenix spacecraft. The stage is successively spun, fired, yo-yo de-spun and jettisoned.]
The Payload Assist Module is a modular upper stage designed and built by McDonnell Douglas, using Thiokol Star-series solid propellant rocket motors. The PAM was used with the Space Shuttle, Delta, and Titan launchers and carried satellites from low Earth orbit to a geostationary transfer orbit or an interplanetary course. The payload was spin stabilized by being mounted on a rotating plate. Originally developed for the Space Shuttle, different versions of the PAM were developed:

PAM-A, development terminated; originally to be used on both the Atlas and Space Shuttle, designed for satellites up to
PAM-D, uses a Star-48B rocket motor, designed for satellites up to
PAM-DII, uses a Star-63 rocket motor, designed for satellites up to
PAM-S, uses a Star-48B as a kick motor for the space probe Ulysses

The PAM-D module was used as an optional third stage of the classic Delta rocket. The PAM-D was discontinued after the Challenger accident. A simplified 3rd stage using the STAR-48 motor was employed on Delta II.

2001 re-entry incident

On January 12, 2001, a PAM-D module re-entered the atmosphere after a "catastrophic orbital decay". The PAM-D stage, which had been used to launch the GPS satellite 2A-11 in 1993, crashed in the sparsely populated Saudi Arabian desert, where it was positively identified.