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.[1] 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 4,400 lb (2,000 kg)
PAM-D (
Delta class), uses a
Star-48B rocket motor, designed for satellites up to 2,750 lb (1,250 kg)[2]
PAM-DII (Delta class), uses a Star-63 rocket motor, designed for satellites up to 4,150 lb (1,880 kg)[2]
PAM-S (Special) as a kick motor for the space probe
Ulysses[2]
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".[3] The PAM-D stage, which had been used to launch the
GPS satellite2A-11 in 1993, crashed in the sparsely populated
Saudi Arabian desert, where it was positively identified.[3]