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GBU-57A/B MOP
American GPS-guided "bunker buster" bomb From Wikipedia, the free encyclopedia
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The GBU-57 series MOP—the initials stand for Guided Bomb Unit and Massive Ordnance Penetrator—is a 30,000-pound (14,000 kg) class, 20.5-foot-long (6.2 m) precision-guided munition "bunker buster" bomb developed by Boeing for the United States Air Force (USAF).[6][4] Composed of a BLU-127 bomb body and an integrated GPS/INS guidance package, the GBU-57 has seven variants, the most recent being the GBU-57F/B.[4] Due to its size and weight, the GBU-57 MOP can only be carried by the Northrop B-2 Spirit strategic bomber[7][8] and the B-21 Raider,[9] although initial tests were conducted with a modified Boeing B-52 Stratofortress.[10][11]
The GBU-57 MOP was first used in combat on June 22, 2025, when seven Northrop B-2 Spirit stealth bombers dropped 14 GBU-57 bombs on Iran's Fordow Uranium Enrichment Plant and Natanz Nuclear Facility.
The bomb is much larger than earlier USAF bunker-busters such as the 5,000-pound (2,300 kg) GBU-28 and GBU-37.[12]
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Development and production
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In 2002, the US Air Force began the "Big BLU" (BLU = Bomb Live Unit) program to develop a series of very powerful conventional munitions.[13] Two main weapons were associated with this concept: a blast variant, the GBU-43/B MOAB (Massive Ordnance Air Blast), a 21,700-pound conventional bomb designed to destroy a large area; and a penetrator variant, the GBU-57 MOP (Massive Ordnance Penetrator). The MOAB was developed in 2003,[14] but the MOP project was paused for funding and technical difficulties.
Bomb damage assessment during the 2003 invasion of Iraq revealed that the Air Force's bunker-busting bombs sometimes failed to destroy fortified military bunkers. This led to the resumption of the Big BLU project. In July 2004, the USAF asked defense contractors to develop a large, precision-guided bomb that could destroy targets deep underground, in caves, or in hardened bunkers.[15] That year, the Defense Threat Reduction Agency (DTRA) and the Munitions Directorate of the Air Force Research Laboratory (AFRL) at Eglin Air Force Base launched the MOP project.[12]
The MOP was designed by Boeing to be used with the B-2 Spirit.[16][17] It was first tested in March 2007, in a DTRA tunnel at the White Sands Missile Range in New Mexico. In July 2007, Northrop Grumman received a contract to refit the B-2, enabling it to carry two of the 14-ton bombs.[18] Beginning in 2008, the MOP was tested under various conditions, including on rocket sleds at Holloman High Speed Test Track and from B-52 and B-2 strategic bomber aircraft at White Sands.[10][11]
Congress approved the acceleration of the project in October 2009,[19][20] but funding delays and test-schedule changes delayed the deployment.[21] The USAF finally began receiving the MOP in September 2011, and had received 16 MOPs by November 2011.[13] In March 2012, there was an "operational stockpile" at Whiteman Air Force Base.[22] By early 2013, the MOP had been integrated onto the B-2.[23]
By November 2015, at least 20 of the bombs had been delivered to the USAF.[24] In October 2019, the USAF awarded $90 million contracts to two steel forging plants to make an unspecified number of case assemblies for the bomb's BLU-127C/B warhead.[25]
In 2024, it was announced that the production capacity of the GBU-57 was going to be at minimum tripled.[26]
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Key components
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The GBU-57's explosive component is a bomb of the BLU-127 series, whose modular design accommodates improvements and upgrades.[4][27] One variant of the BLU-127 bomb body contains 4,590 pounds (2,082 kg) of AFX-757 and 752 pounds (341 kg) of PBXN-114, a polymer-bonded explosive (PBX), for a total explosive payload of 5,342 pounds (2,423 kg). The PBX is optimized for controlled detonation in confined spaces. The bomb's casing is made from high-density Eglin steel alloy, engineered to survive the extreme stresses of deep penetration before detonation.[4][28][29]
Attached to the BLU-127's tail, is a KMU-612 tail-kit which contains a GPS-assisted inertial navigation system guidance package, as well as control surfaces to maintain trajectory and allow for mid-course adjustments.[30][31] The GBU-57 has grid fins, not the planar fins found on most conventional bombs, because they can fold for storage in a B-2's bomb bays and offer greater control at high speeds. Grid fins have higher drag than planar fins, and so are usually smaller.
The GBU-57 is a precision-guided munition, able to strike within meters of its target.[32] Detonation timing is managed by the Large Penetrator Smart Fuse (LPSF), which adjusts the moment of explosion based on impact depth and the characteristics of the underground structure.[28]
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Combat use
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US airstrikes on Iranian nuclear facilities
The first combat use of the GBU-57 was during the United States strikes on Iranian nuclear sites on June 22, 2025,[33][34] when seven Northrop B-2 Spirit stealth bombers dropped twelve MOPs on the Fordow Uranium Enrichment Plant and two on the Natanz Nuclear Facility.[35][36]
There has been debate over whether the GBU-57 Massive Ordnance Penetrator (MOP) can reliably destroy Iran's deeply buried nuclear sites. The Fordow facility and the new halls under construction at Natanz are thought to lie more than 80 m underground, whereas the original Natanz enrichment plant sits roughly 20 m below the surface.[37]
The MOP is reportedly able to penetrate about 18 meters of reinforced concrete with a compressive strength of 5,000 psi (34 MPa).[38][39] Iranian domestic research has produced concrete exceeding 30,000 psi (210 MPa), which could sharply reduce the bomb's effective penetration depth.[37] Additionally, the Fordow site is underneath rock composed primarily of limestone which has variable compressive strength but can reach 25,000 psi (170 MPa), especially at greater depths.[40] Advanced bunker-shell construction techniques can cause deflection or yaw.[41]
Specifications and capabilities
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- Length: 20.5 feet (6.2 m)[5][42]
- Diameter: 31.5 inches (0.8 m)[5][42]
- BLU-127 bomb body weight: 27,125 pounds (12,304 kg)[4]
- Explosive weight: 5,342 pounds (2,423 kg)[4][42]
- Penetration: (debated) There is debate about the penetration capabilities of the bomb. The US Air Force has said that the GBU-57 can penetrate up to 200 ft (60 m) of unspecified material before exploding.[43] The BBC reports that analysts at Janes Information Services say the weapon can penetrate about 200 ft (60 m) of earth or 60 ft (18 m) of concrete.[38] A separate source suggests penetration of up to 60 ft (18 m) into reinforced concrete with a compressive strength of 5,000 psi (34 MPa) and 8 ft (2.4 m) into 10,000 psi (69 MPa) reinforced concrete.[16]
Only the B-2 Spirit is configured to carry the MOP; the B-21 Raider is slated to carry it.[44][28] The B-52 has been used to test the MOP, but would require modification to be used in combat.[4]
The GBU-57 has a 'smart' fuse that is capable of achieving effects against targets on which there is limited intelligence.[45] It can also be preprogrammed to detonate at a specified depth.[46]
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Users
United States
United States Air Force – At least 20 in service as of November 2015.[3]
Gallery
MOP being offloaded in preparation for its first explosive test, 2007.
MOP underground at White Sands Missile Range before its first explosive test, 2007.
Mock up of MOP inside a bomb bay of a B-2 simulator, 2007.
B-52 releases a MOP during a weapons test, 2009.
See also
- Specific large bombs
- BLU-82 Daisy Cutter bomb
- Father of All Bombs
- GBU-43/B Mother of All Bombs, another very large US bomb
- Grand Slam (bomb)
- T-12 Cloudmaker
- Tallboy (bomb)
- FAB-9000
References
External links
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