Payload Assist Module

{{Short description|Single-stage solid-fueled booster stage}}

Image:PAM-D 1920x1080.ogv spacecraft. The stage is successively spun, fired, yo-yo de-spun and jettisoned.]]

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.{{cite web |url=http://www.globalsecurity.org/space/systems/pam.htm |title=Payload Assist Module (PAM) |publisher=Global Security |access-date=June 8, 2012}} 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 {{convert|4400|lb|abbr=on}}
• PAM-D (Delta class), uses a Star-48B rocket motor, designed for satellites up to {{convert|2750|lb|abbr=on}}{{Cite web |last=Krebs |first=Gunter D. |title=PAM-D, PAM-D2, PAM-S |url=https://space.skyrocket.de/doc_stage/pam-d.htm |access-date=2024-01-05 |website=Gunter's Space Page}}
• PAM-DII (Delta class), uses a Star-63 rocket motor, designed for satellites up to {{convert|4150|lb|abbr=on}}
• PAM-S (Special), uses a Star-48B as a kick motor for the space probe Ulysses

The PAM-D module was used as an optional third stage of the classic Delta rocket. The PAM-D was discontinued after the Challenger accident. A simplified 3rd stage using the STAR-48 motor was employed on Delta II.