The GBU-57A/B Massive Ordnance Penetrator (MOP) is a U.S. Air Force, precision-guided, 30,000-pound (14,000 kg) "bunker buster" bomb. This is substantially larger than the deepest penetrating bunker busters previously available, the 5,000-pound (2,300 kg) GBU-28 and GBU-37.In 2012, the Pentagon requested $82 million to develop greater penetration power for the existing weapon. A 2013 report stated that the development had been a success, and B-2 integration testing began that year.
The bomb can penetrate 200 feet of 5000 psi hardened concrete and is accurate enough for multiple hits on the same location to penetrate deeper targets or targets with even stronger concrete. One GBUJ-57A/B can only penetrate 8 meters of 10,000 psi rock or concrete. This could drop to 2 meters of 30,000 psi material.
Rock of over 10,000 psi is considered hard. The strongest granite is about 30,000 psi. In 2007, the University of Tehran made several concrete cubes between 50,000 to 60,000 psi, and possible stronger. The aggregate to be made from quartz, and had some steel fibers in the mix.
High-strength concrete has a compressive strength greater than 40 MPa (5800 psi).