Bunker buster
A bunker buster is a type of munition that is designed to penetrate hardened targets or targets buried deep underground, such as military bunkers.
Armor piercing shells
Germany
s were bunker-busting artillery shells, developed by the German engineer August Cönders, based on the theory of increasing sectional density to improve penetration. They were tested in 1942 and 1943 against the Belgian Fort d'Aubin-Neufchâteau.Aircraft delivered bombs
World War II
Germany
In World War II the Luftwaffe developed a series of unguided rocket-propelled armor-piercing bombs for use against shipping and fortifications.United Kingdom
In World War II, the British designer Barnes Wallis, already famous for inventing the bouncing bomb, designed two bombs that would become the conceptual predecessors of modern bunker busters: the five tonne Tallboy and the ten tonne Grand Slam. These were "Earthquake" bombs—a concept he had first proposed in 1939. The designs were very aerodynamic, allowing them to exceed the speed of sound as they fell from 22,000 ft. The tails were designed with offset fins causing the bombs to spin as they fell. Using the same principle as a spinning top, this enabled them to resist being deflected, thereby improving accuracy. They had casings of high grade steel, much stronger than the typical World War II bomb so that they would survive hitting a hardened surface, or penetrate deep into the ground.Though these bombs might be thought of as 'bunker busters' today, in fact the original 'earthquake' theory was more complex and subtle than simply penetrating a hardened surface. The Earthquake bombs were designed not to strike a target directly, but to impact beside it, penetrate under it, and create a 'camouflet' or large buried cavern at the same time as delivering a shock wave through the target's foundations. The target then collapses into the hole, no matter how hardened it may be. The bombs had strong casings because they needed to travel through rock rather than reinforced concrete, though they could perform equally well against hardened surfaces. In an attack on the Valentin U-Boat pens at Farge, two Grand Slams went through the 15 ft reinforced concrete hardening—equalling or exceeding the best current penetration specifications.
The British Disney bomb was a World War II device designed to be used against U-boat pens and other super-hardened targets. Devised by Captain Edward Terrell RNVR of the Admiralty's Directorate of Miscellaneous Weapons Development, it had a streamlined hardened case and weighed some including the rocket assembly. The actual explosive content was about.
For accuracy, the bombs had to be dropped precisely from a pre-determined height. They would free-fall for around 30 seconds until, at, the rockets were ignited, causing the tail section to be expelled. The rocket burn lasted for three seconds and added to the bomb's speed, giving a final impact speed of, approximately Mach 1.29. Post-war tests demonstrated that the bombs were able to penetrate a thick concrete roof, with the predicted ability to penetrate of concrete.
United States
Post war, the US added a form of remote guidance to the Tallboy to create the Tarzon, a 12,000-pound bomb deployed in the Korean War against an underground command center near Kanggye.Modern
During Operation Desert Storm, there was a need for a deep penetration bomb similar to the British weapons of World War II, but none of the NATO air forces had such a weapon. As a stop-gap, some were developed over a period of 28 days, using old 8 inch artillery barrels as casings. These bombs weighed over two tons but carried only of high explosive. They were laser-guided and were designated "Guided Bomb Unit-28 ". It was proven effective for the intended role.An example of a Russian bunker buster is the KAB-1500L-Pr. It is delivered with the Su-24M and the Su-27IB aircraft. It is stated to be able to penetrate 10–20 m of earth or 2 m of reinforced concrete. The bomb weighs, with being the high explosive penetrating warhead. It is laser guided and has a reported strike accuracy of CEP.
The US has a series of custom made bombs to penetrate hardened or deeply buried structures:
| Depth of Penetration | Weapon Systems | - |
| Penetration of reinforced concrete: 1.8 m | BLU-109 Penetrator | GBU-10, GBU-15, GBU-24, GBU-27, AGM-130 |
| Penetration of reinforced concrete: 3.4 m | BLU-116 Advanced Unitary Penetrator | GBU-15, GBU-24, GBU-27, AGM-130 |
| Penetration of reinforced concrete: 3.4 m | BLU-118/B Thermobaric Warhead | GBU-15, GBU-24, AGM-130 |
| Penetration of reinforced concrete: more than 6 m | BLU-113 Super Penetrator | GBU-28, GBU-37 |
More recently, the US has developed the 30,000-pound GBU-57.
Fuzing
The traditional fuze is the same as a classic armor-piercing bomb: a combination of timer and a sturdy dynamic propeller on the rear of the bomb. The fuze is armed when the bomb is released, and detonates when the propeller stops turning and the timer has expired.Modern bunker busters may use the traditional fuze, but some also include a microphone and microcontroller. The microphone listens, and the micro controller counts floors until the bomb breaks through the desired numbers of floors.
ATK is working on a Hard Target Void Sensing Fuze for 2000 and 5000 pound weapons to explode when they reach an open space in a deeply buried bunker.