The Payload Assist Module (PAM) is a modular upper stage designed and built by McDonnell Douglas (now 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 satellite 2A-11 in 1993, crashed in the sparsely populated Saudi Arabian desert, where it was positively identified.^[3]

Gallery

• 
  PAM-D stage in assembly
• 
  SBS-3 satellite with PAM-D stage being launched from Space Shuttle Columbia
• 
  Saudi officials inspect a PAM-D module that re-entered the atmosphere in 2001
• 
  SATCOM KU-2 attached to a PAM-DII is being released from the cargo bay of the Space Shuttle Orbiter Atlantis during STS-61B
• 
  Ulysses is mated with the PAM-S