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.

## Overview

### World War II

Creation of such weapons originated during World War II on Earth. Both sides of the Allies and the Axis created weapons that can penetrate and destroy the toughest defenses for each platform.

#### Armor piercing shells

On the Axis side, Nazi Germany created the *Rochling shells,* bunker-busting artillery shells used to defeat *Fort d'Aubin-Neufchâteau*, a Belgian fort. However, Imperial Japan didn't have any bunker-busting capabilities during the war.

#### Aircraft-delivered bombs

In World War II, the Luftwaffe (German Air Force) developed a series of unguided rocket-propelled armor-piercing bombs for use against shipping and fortifications.

On the side of the Allies, 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 5-tonne *Tallboy* and the 10-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 (6,700 m). 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 (4.5 m) reinforced concrete hardening—equalling or exceeding the best current penetration specifications.

Post-WWII, the United States added a form of remote guidance to the *Tallboy* to create the *Tarzon*, a 12,000-pound bomb (5,443 kg) deployed in the Korean War.

### Modern

During Operation Desert Storm (1991), 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 (203 mm) artillery barrels as casings. These bombs weighed over two tons but carried only 647 lb (293 kg) of high explosive. They were laser-guided and were designated "Guided Bomb Unit-28 (GBU-28)". It was proven effective for the intended role.

The US created custom-made Bunker Busters such as the *Paveway* family of bombs.

### Other kinds of bunker-busting

#### 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.

#### Missiles

The extra speed provided by a rocket motor enables greater penetration of a missile-mounted bunker buster warhead. To reach maximum penetration (impact depth), the warhead may consist of a high-density projectile only. Such a warhead carries more energy than a warhead with chemical explosives (kinetic energy of a projectile at hypervelocity).

#### Nuclear

The nuclear bunker buster is the nuclear weapon version of the bunker buster. The non-nuclear component of the weapon is designed to greatly enhance the penetration into soil, rock, or concrete to deliver a nuclear warhead to a target. These weapons would be used to destroy hardened, underground military bunkers deeply buried. In theory, the amount of radioactive nuclear fallout would be reduced from that of a standard, air-burst nuclear detonation because they would have relatively low explosive yield. However, because such weapons necessarily come into contact with large amounts of earth-based debris, they may, under certain circumstances, still generate significant fallout. Warhead yield and weapon design have changed periodically throughout the history of the design of such weapons. An underground explosion releases a larger fraction of its energy into the ground, compared to an explosion at or above the surface which releases most of its energy into the atmosphere.

## Bunker Busting in the New World

### Japan

As an additional countermeasure against the revival of the Yamato no Orochi, the Japanese government instructed the Ministry of Defense to take measures. This includes the development of Bunker Busters and Thermobaric Bombs, with samples provided by the USFJ. Such weapons will also be helpful against the Gra Valkas Empire once the preparations for the battle are complete.