Bunker Buster: How the Massive Ordnance Penetrator (MOP) Works

The GBU-57 Massive Ordnance Penetrator (MOP) is a 30,000-pound class weapon designed to strike hardened, deeply buried targets. The MOP guides itself using a combination of GPS and an inertial navigation system, then impacts the surface at high speed while using a specialized steel alloy casing to “drill” through the ground, and finally detonates its roughly 5,000-pound warhead. The MOP can reportedly penetrate at least 200 feet, although newer models may be able to strike even deeper. If a single MOP is unable to reach the target, additional MOPs could be dropped to penetrate deeper underground. The B-2 Spirit is the only aircraft in the U.S. inventory currently equipped to employ the MOP in combat and can carry two of the weapons, while the forthcoming B-21 Raider is expected to carry a single MOP.