Nuclear Bunker Buster - Development of Bunker-busting Weapons

Development of Bunker-busting Weapons

As early as 1944, the Wallis Tallboy bomb and subsequent Grand Slam weapons were designed to penetrate deeply fortified structures through sheer explosive power. These were not designed to directly penetrate defences, though they could do this (for example the Valentin submarine pens had ferrous concrete roofs 7 metres (23 ft) thick which were penetrated by two Grand Slams on 27 March 1945), but rather to penetrate under the target and explode leaving a camouflet (cavern) which would undermine foundations of structures above, causing it to collapse, thus negating any possible hardening. The destruction of targets such as the V3 battery at Mimoyecques was the first operational use of the Tallboy. One bored through a hillside and exploded in the Saumur rail tunnel about 18 m (60 ft) below, completely blocking it, and showing that these weapons could destroy any hardened or deeply excavated installation. Modern targeting techniques allied with multiple strikes could perform a similar task.

Development continued, with weapons such as the nuclear B61, and conventional thermobaric weapons and GBU-28. One of the more effective housings, the GBU-28 used its large mass (2,130 kg / 4,700 lb) and casing (constructed from barrels of surplus 203 mm howitzers) to penetrate 6 meters (20 ft) of concrete, and more than 30 metres (100 ft) of earth. The B61 Mod 11, which first entered military service in January 1997, was specifically developed to allow for bunker penetration, and is speculated to have the ability to destroy hardened targets a few hundred feet beneath the earth.

While penetrations of 20–100 feet (30 m) were sufficient for some shallow targets, both the Soviet Union and the United States were creating bunkers buried under huge volumes of soil or reinforced concrete in order to withstand the multi-megaton thermonuclear weapons developed in the 1950s and 1960s. Bunker penetration weapons were initially designed within this Cold War context.

The weapon was revisited after the Cold War during the 2001 U.S. invasion of Afghanistan, and again during the 2003 invasion of Iraq. During the campaign in Tora Bora in particular, the United States believed that "vast underground complexes," deeply buried, were protecting opposing forces. Such complexes were not found. While a nuclear penetrator (the "Robust Nuclear Earth Penetrator", or "RNEP") was never built, the U.S. DOE was allotted budget to develop it, and tests were conducted by the U.S. Air Force Research Laboratory.

The Bush administration removed its request for funding of the weapon in October 2005. Additionally, then U.S. Senator Pete Domenici announced funding for the nuclear bunker-buster has been dropped from the U.S. Department of Energy's 2006 budget at the department's request.

While the project for the RNEP seems to be in fact canceled, Jane's Information Group speculated in 2005 that work might continue under another name.