All About GBU-57, the US Bomb Capable of Destroying Iranian Nuclear Bunkers
What is GBU-57 or Massive Ordnance Penetrator, the US bomb carried only by the B-2 stealth bomber (pictured) and designed to destroy targets deep underground. This weapon, according to experts, could be used to strike the Iranian nuclear program.
The bunker-buster bomb is American, the only weapon capable of destroying Iran's deeply buried nuclear facilities.
Iran's underground and hardened nuclear sites are invulnerable to most conventional (i.e. non-nuclear) weapons. The GBU-57 Massive Ordnance Penetrator (MOP) is the most powerful 14-ton non-nuclear bomb in the U.S. arsenal for targeting underground facilities.
If the United States intervenes in the escalating conflict between Israel and Iran, attention would likely focus on damaging or destroying Tehran’s underground nuclear facilities. Iran’s deepest nuclear enrichment site is Fordow, in the desert southwest of Tehran. It lies under about 300 feet of rock.
This task would most likely fall to a small number of Air Force strategic bombers, the B-2 Spirits, which are the only ones authorized to drop these precision-guided bombs capable of penetrating very deep into rock and concrete.
Former US Army lieutenant general and Rand Corporation defense researcher Mark Schwartz insists that “only the United States has the conventional capability” to destroy such a site, AFP reports.
All the details on the GBU-57 bomb, better known as the “bunker buster” or Massive Ordnance Penetrator, built by the American Boeing.
WHAT IS THE GBU-57 MOP BOMB
The GBU-57A/B Massive Ordnance Penetrator (MOP) is a 14-ton precision-guided bunker buster bomb used by the United States Air Force. It is substantially larger than the previously available deepest penetrating bunker buster bombs, the 5,000-lb GBU-28 and GBU-37.
Design of this bomb began in the early 2000s. In 2009, the Department of Defense placed an order for 20 units with Boeing.
As the Washington Post points out, Mop is designed for deep underground and fortified structures, such as bunkers and tunnels. Its design, weight, and steel alloy construction allow it to burrow underground and then explode, according to the U.S. Air Force.
Although it is the heaviest conventional weapon in the U.S. arsenal, it is not designed to saturate explosives over a wide area. Commanders rely on its GPS-guided precision to hit specific, well-defended targets and destroy what ordinary bombs cannot. There are no public reports of the MOP being used in combat, experts say.
THE FEATURES
As already mentioned, the device weighs 14 tons and is 6.2 meters long. It carries 2,500 kg of high explosives.
The warhead casing is made of a special high-performance steel alloy and its design allows it to carry a high explosive load while maintaining the integrity of the penetrator casing during impact. It can penetrate up to 60 meters of reinforced concrete or rock. In fact, this bomb was specifically designed to destroy armored bunkers, tunnel networks and nuclear facilities that conventional munitions cannot reach.
THE EFFICACY
According to The War Zone, the MOP is the world's deepest and most powerful non-nuclear bunker buster, and is essential for destroying highly fortified targets buried under mountains, such as those found in Iran, Russia, China and North Korea. The weapon is guided and can strike the surface above the target with a high degree of accuracy.
But it’s likely more powerful now, after further developments over the past two decades, Trevor Ball, a former Army explosive ordnance disposal technician, told the Post .
The GBU-57 also has a specialized fuse because “you need an explosive that doesn’t detonate immediately under such high shock and pressure,” Masao Dahlgren, a weapons specialist at the CSIS research center in Washington, told AFP .
However, they are also short-range direct-attack weapons, Breaking Defense points out. That means the bombers that launch them must fly close to targets that are likely to be heavily defended.
CARRIED ONLY BY B-2 SPIRIT STEALTH BOMBERS DEVELOPED BY
The U.S. B-2 Spirit stealth bomber is currently the only Air Force aircraft authorized to carry and operationally deploy the MOP, with each bomber capable of carrying two bombs.
Manufactured by US giant Northrop Grumman , the B-2 is the US military's only stealthy nuclear-capable heavy bomber, traveling at subsonic speeds but capable of refueling in flight, the B-2 can travel up to 11,000 kilometers. Experts say this puts the B-2, equipped with stealth technology and equipped to carry the heaviest US bombs and nuclear weapons, in an ideal position to operate in the Middle East.
During the Kosovo War in the late 1990s, B-2 pilots flew round-trip flights from their Whiteman Air Force Base in Missouri to strike targets. In 2017, a pair of B-2s flew for 34 hours to strike Islamic State camps in Libya, the Washington Post reported.
There are only 20 B-2 bombers in the U.S. Air Force inventory. As many as six B-2 bombers were transferred to a joint Anglo-American military base on the Indian Ocean island of Diego Garcia in March, Reuters reported, citing U.S. officials, amid a U.S. bombing campaign in Yemen and rising tensions with Iran.
MOP UPDATES
Recent upgrades to the GBU-57A/B include addressing an undisclosed “integration issue” with the B-2, the Air Force said last year.
The Air Force also said it is testing technology that can help destroy targets whose substructures might be difficult to access for intelligence. A smart fuse on the Mop can detect voids along its downward path, such as rooms and floors, and detonate at the optimal point, Ball said.
This would be an important capability if commanders decided they needed to strike the same deep target multiple times. It is unclear whether the technology is actually in operational use yet, the Post concludes.
This is a machine translation from Italian language of a post published on Start Magazine at the URL https://www.startmag.it/spazio-e-difesa/tutto-su-gbu-57-la-bomba-statunitense-in-grado-di-distruggere-i-bunker-del-nucleare-iraniano/ on Wed, 18 Jun 2025 11:26:50 +0000.