GBU-57 MOP bomb: how the U.S. Air Force hammered Iran’s underground nuclear facilities

The GBU-57 MOP is one of the heaviest bombs in the United States Air Force arsenal, designed specifically to destroy bunkers, fortifications, shelters and underground facilities such as missile silos or nuclear storage sites. Developed in the mid-2000s by the Air Force Research Laboratory, the bomb was tested and produced by Boeing.

The MOP weighs nearly 13,600 kilograms, including a 2,400-kilogram BLU-127 warhead, and measures 625 cm in length with an 80 cm diameter. It is guided to its target using satellite GPS and inertial navigation systems, and is carried exclusively by Northrop Grumman B-2 Spirit bombers.

Capable of penetrating up to 60 metres into the ground or piercing eight metres of reinforced concrete before detonation, the MOP was designed for deep-target operations. In July 2007, Northrop Grumman announced it had signed a contract to adapt the B-2 fleet to carry two MOPs each.

The first test explosion of the MOP was conducted on 14 March 2007 in an underground tunnel at the White Sands Missile Range in New Mexico, under the supervision of the Defense Threat Reduction Agency (DTRA). Between 2008 and 2010, several further test drops were carried out using Boeing B-52 Stratofortress bombers at the same range.

Available information indicates that the U.S. Air Force has ordered at least 20 MOP bombs to date. These weapons are intended for use in scenarios requiring precision strikes against fortified underground targets.