[2] It is designed to destroy large, reinforced concrete structures, such as bridges, and was developed by Alliant Techsystems in collaboration with the Lawrence Livermore National Laboratory.
[1] The PAM originated in a project run by the Livermore laboratory for the United States Air Force.
In the 1980s, they were tasked with developing a two-stage explosive device: this resulted in a 2,000 lb bomb, and funding from DARPA to develop a three-stage device designed to blow craters in runways.
[1] Each PAM consists of four primary components: a Tandem Forward Charge (TFC), a Follow Through Charge (FTC), a propulsion system, and an electronic fusing system.
The FTC is then accelerated by the propulsion system into the newly drilled hole, where it detonates, removing up to 75% of the target's ability to bear loads.