Payload Assist Module



The Payload Assist Module (PAM) is a modular upper stage designed and built by McDonnell Douglas (Boeing), 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 (Atlas class), development terminated; originally to be used on both the Atlas and Space Shuttle, designed for satellites up to 4400 lb
 * PAM-D (Delta class), uses a Star-48B rocket motor, designed for satellites up to 2750 lb
 * PAM-DII (Delta class), uses a Star-63 rocket motor, designed for satellites up to 4150 lb
 * PAM-S (Special) as a kick motor for the space probe Ulysses

The PAM-D module, used as the third stage of the Delta II rocket, was the last version in use. As of 2018, no PAM is in active use on any rockets.

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.