Payload Assist Module

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PAM-D with the Phoenix spacecraft. The stage is successively spun, fired, yo-yo de-spun and jettisoned.
SBS-3 satellite with PAM-D stage being launched from the Space Shuttle Columbia
PAM-D stage in assembly

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 engines. 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

The PAM-D module, used as the third stage of the Delta II rocket, is the only version in use today.

2001 re-entry incident[edit]

Saudi officials inspect a PAM-D module that re-entered the atmosphere in 2001.

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 a GPS satellite in 1993, crashed in the sparsely populated Saudi Arabian desert, where it was positively identified.[2]

External links[edit]


  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.