GBU-57 Massive Ordnance Penetrator (MOP) is a 30,000-pound (13,600 kg), precision-guided bunker-buster bomb developed by Boeing for the United States Air Force (USAF). It is designed to destroy deeply buried and hardened targets, such as underground nuclear facilities, by penetrating up to 200 feet (61 meters) of earth or reinforced concrete before detonating. Key Specifications:

Length: 20.5 ft (6.2 m)

Diameter: 31.5 in (0.8 m)

Warhead: 5,740 lb (2,604 kg) of high explosive (AFX-757 and PBXN-114)

Guidance: GPS/INS with grid fins for precision control

Penetration: Up to 200 ft (61 m) of soil or rock; approximately 18 m (60 ft) into 5,000 psi concrete

Fuzing: Large Penetrator Smart Fuze (LPSF) allows for depth-specific detonation 

Only carried by the B-2 Spirit stealth bomber, which can carry two MOPs.

The B-21 Raider is also slated to carry the GBU-57.

The B-52 Stratofortress has been used in testing but is not currently combat-capable with the MOP. 

First used in combat on June 22, 2025, during U.S. strikes on Iran’s Fordow Uranium Enrichment Plant and Natanz Nuclear Facility.

Seven B-2 bombers dropped 14 MOPs in total, targeting deeply buried sites thought to be up to 300 feet (90 m) underground. 

Initiated in 2004 under a USAF-DTRA partnership.

Entered service in 2011; at least 20 units delivered by 2015.

Production capacity was tripled in 2024 to meet strategic demand. 

Iran’s Fordow facility is located under 300 feet of rock, and its concrete exceeds 30,000 psi compressive strength—potentially beyond the MOP’s penetration capability.

Analysts suggest multiple sequential drops may be required to achieve deep penetration, increasing risk and complexity. 

GBU-43/B MOAB (Mother of All Bombs): Airburst bomb (21,700 lb), designed for area destruction, not penetration.

GBU-28: 5,000 lb laser-guided bomb; limited to ~20 ft (6 m) penetration.