In essence, the PAM is a portable launch platform with spin motor attached and spring device. When ready to launch the payload, the spin motor is activated and the spring device ejects the payload at the proper time.
Orbital attitude thrusters aboard the the payload adjust the course and attitude of the payload.
In the case of Space Shuttles, which are limited to low Earth orbits of below 690 miles, the PAM is used to boost satellites into much higher orbits, for example, geocentric orbits which are at 22,300 miles. The PAM-D cradle shown here is serial No. 02 and was flown on four Space Shuttle missions and on three Shuttles, the Challenger, Discovery, and Atlantis. McDonnell Douglas Astronautics Co. This PAM-D lacks its Sun shade and electronic modules. It also provided an expendable launch vehicle backup system during the early Space Shuttle flights and extended the functional operating range of the Shuttle. The capacity of the later PAM cradles, such as the D-model, were capable of carrying a maximum weight of 2,450 lbs for the Delta 3910 PAM system and 2,800 lbs for the Delta 3920.