Bunker buster bombs are not battlefield munitions. They serve a very specific purpose, with potential returns far outpacing the monetary cost.
By now, most observers are aware of the seemingly devastating US Air Force strikes on Iran’s underground nuclear facilities on June 22. Six B-2 Spirit bombers hit three Iranian targets, most notably the heavily fortified Fordow nuclear enrichment site. It was the first known operational deployment of the GBU-57 “Massive Ordnance Penetrator” (MOP) bomb, more commonly called the “bunker buster.” The mission was aimed at destroying Iran’s nuclear enrichment program when the regime refused to limit itself to strictly civilian nuclear power-generation.
The GBU-57 MOP is the world’s most powerful non-nuclear aerial munition, packing 5,342 pounds of lethal high-explosive inside its 30,000-pound bulk. The bomb is so heavy that only the B-2 and the B-52 can carry it—though the B-52’s vulnerability to modern air defense systems precludes its operational use on such missions. Each B-2 can carry two GBU-57s.
The USAF collaborated with Boeing to design, test, and manufacture the GBU-57 MOP to penetrate and destroy the world’s hardest and best-protected targets without resorting to nuclear weapons. The project began in 2004, after previous bunker buster munitions failed to fully penetrate hardened enemy positions during the 2003 Iraq invasion, resulting in inadequate performance.
The GBU-57 MOP is designed to penetrate up to 200 feet of moderately hard rock, and up to 60 feet of reinforced concrete. For comparison, this is three times the effective penetration rate of the 4,000- to 5,000-pound GBU-28, the GBU-57’s immediate predecessor.
The 20-foot long hardened ferro-cobalt alloy casing accounts for most of the GBU-57’s weight. The in-flight adjustable guidance fins allow pinpoint precision, even with the bomb achieving supersonic speeds before impact. The kinetic energy from the bomb’s combined weight, velocity, and hardened construction provide the penetration—but the electronics package maximizes the GBU-57 MOPs effectiveness.
The bomb’s nose contains a precise GPS and inertial guidance system that employs those adjustable fins. This ensures the GBU-57 hits its intended target. But the bomb’s precision doesn’t stop there; its delayed fuse detects voids or open spaces in the target’s protection, only then triggering the payload for maximum destruction and high-value results.
A useful point of comparison here is World War II’s iconic B-17 Flying Fortress bomber, which carried an average payload of 4,000-8,000 pounds of bombs. According to contemporary statistics, only 20 percent of the B-17’s payload landed within 1,000 feet of its target. Even then, underground facilities were all but impervious, even to a direct hit. By contrast, the GBU-57 MOP delivers over 5,300 pounds of high explosive on-target every time, even when that target is deep underground. Strategic bombing has come a long way.
The GBU-57 Is One of America’s Most Expensive Bombs
Of course, modern munitions are not cheap—and specialized high-precision weapons are even more expensive. The GBU-57 MOP’s exact price tag is classified, but estimates place its cost in the tens of millions of dollars per unit. Add that to the B-2 bomber’s astonishing operational cost of $150,000 per flight hour, and the GBU-57 becomes one of history’s most expensive single-use conventional weapons. Such expenditures alone would limit the GBU-57’s role to the strategic realm.
But the specialized mission also dictates the strategic designation. The bunker buster bombs are not battlefield munitions. They serve a very specific purpose, with potential returns far outpacing the monetary cost. Ending Iran’s uranium enrichment capability—if Operation Midnight Hammer truly achieved this goal—is one of those outsized returns.
Iran’s Fordow nuclear facility reportedly took six GBU-57 MOPs, meaning over 32,000 pounds of high explosive detonated in its most sensitive areas. Amateur video circulated showing mushroom-like fireballs rising hundreds of feet over the impact area. If the destruction was as complete as some sources have reported, Iran is paying a steep price for its intransigence. And even without complete destruction, the three targets would require years and millions of dollars to rebuild. That’s time and money the Iranians may not have—and the cost of the munitions that made it so on the American side seems to have been well-spent.
About the Author: William Lawson
William Lawson is a military historian focusing on World War II and 20th century conflicts and the American Civil War. His specialty is operational level warfare, especially American amphibious doctrine. He writes on history, politics, and firearms for multiple publications and historical journals. He serves on the editorial advisory board for the Saber & Scroll Journal and Military History Chronicles and is a member of the Society for Military History and the American Historical Association. Lawson is based in Virginia.
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