Payload Assist Module


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
  • PAM-D (Delta class), uses a Star-48B rocket motor
  • PAM-DII (Delta class), uses a Star-63 rocket motor
  • PAM-S (Special) as a kick motor for the space probe Ulysses
PAM-D with the Phoenix spacecraft. The stage is successively spun, fired, yo-yo de-spun and jettisoned.

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 incidentEdit

On January 12, 2001, a PAM-D module re-entered the atmosphere after a "catastrophic orbital decay".[2] 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.[2]



  1. ^ "Payload Assist Module (PAM)". Global Security. Retrieved June 8, 2012.
  2. ^ a b "PAM-D Debris Falls in Saudi Arabia" (PDF). The Orbital Debris Quarterly News. NASA Johnson Space Center. 6 (2): 1. April 2001.

External linksEdit

  • Payload Assist Module at the NASA Shuttle Reference Manual
  • Payload Assist Module at