Nuclear bunker buster - AbsoluteAstronomy.com

Bunker-busting nuclear weapons, also known as earth-penetrating weapons (EPW), are a type of nuclear weapon

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

designed to penetrate into soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, rock

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

, or concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

to deliver a nuclear warhead to a target. These weapons would be used to destroy hardened, underground military

Military

A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

bunker

Bunker

A military bunker is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks...

s buried deep in the ground. In theory, the amount of radioactive nuclear fallout

Nuclear fallout

Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...

would be reduced from that of a standard, air-burst nuclear detonation because they would have relatively low explosive yield

Nuclear weapon yield

The explosive yield of a nuclear weapon is the amount of energy discharged when a nuclear weapon is detonated, expressed usually in the equivalent mass of trinitrotoluene , either in kilotons or megatons , but sometimes also in terajoules...

. However because such weapons necessarily come into contact with large amounts of earth-based debris, they may, under certain circumstances, still generate fallout. Warhead

Warhead

The term warhead refers to the explosive material and detonator that is delivered by a missile, rocket, or torpedo.- Etymology :During the early development of naval torpedoes, they could be equipped with an inert payload that was intended for use during training, test firing and exercises. This...

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.

Base principle

While conventional bunker busters utilize several methods to penetrate concrete structures, these are for the purpose of destroying the structure directly, and are generally limited in how much of a bunker, or system of bunkers they can destroy by depth and their relatively low explosive force (versus nuclear weapons). The primary difference between conventional and nuclear Bunker Busters, is that while the conventional version is meant for one target, the nuclear version can destroy an entire underground bunker system in one hit.

The main principles in modern bunker design are largely centered around survivability to nuclear war. As a result of this both American and former Soviet sites reached a state of "super hardening" involving principle defenses against the effects of a nuclear weapon, spring or counterweight (in the case of the R-36) mounted control capsules, thick (3-4 feet for the Minuteman command capsule) heavily reinforced with rebar and steel. These systems were designed to survive at their base a near miss of 20 megatons. The reason for this is that the seismic forces of an air burst of 20 megatons does not impart shockwaves strong enough to overcome their countermeasures, and due to things like depth, soil type, rock formations, etc, the predictability of the outcome is highly variable.

A nuclear bunker buster negates most of the countermeasures involved in the protection of underground bunkers. By penetrating the ground it directs all of its energy into it, this means that a relatively low yield may be able to produce seismic forces beyond those of an air burst or even groundburst of a weapon with twice its yield. Additionally the weapon by imparting the kinetic energy at depth has the ability to impart more severe horizontal shockwaves which many bunker systems are not explicitly designed to combat. Further, the explosive force being expelled into the ground directly and at depth keeps the fission and fusion products more limited in immediate distribution, as opposed to carrying them high into the upper atmosphere along with the rest of the vaporized debris. This means while there is fallout, it is extremely localized, making the weapon especially appealing to tactical planning, as opposed to strategic planning.

Penetration by explosive force

Concrete

structure design has not changed much in the last 60 years. The majority of protected concrete structures in the US military are derived from standards set forth in Fundamentals of Protective Design, published in 1946 (US Army Corps of Engineers). Various augmentations, such as glass

Glass

Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

, fiber

Fiber

Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....

s, and rebar

Rebar

A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...

, have made concrete less vulnerable, but far from impenetrable.

When explosive force is applied to concrete, three major fracture regions are usually formed: the initial crater, a crushed aggregate surrounding the crater, and "scabbing" on the surface opposite the crater. Scabbing, also known as "spall

Spall

Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...

ing," is the violent separation of a mass of material from the opposite face of a plate or slab subjected to an impact or impulsive loading (this does not necessarily mean that the barrier itself must have been penetrated at this point).

As the compressive wave propagates to the opposite side of the concrete and is reflected, the concrete fractures, and scabbing occurs on the interior wall. As such, an asymptotic relationship exists between the strength of the concrete and the damage that will be done between the crater, aggregate, and scabbing.

While soil is a less dense material, it also does not transmit shock wave

Shock wave

A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

s as well as concrete. So while a penetrator may actually travel further through soil, its effect may be lessened due to its inability to transmit shock to the target.

Penetration with a hardened penetrator

Further thinking on the subject envisions a penetrator, dropped from service height of a bomber

Bomber

A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...

aircraft, using kinetic energy to penetrate the shielding, and subsequently deliver a nuclear explosive to the buried target.

The problems with such a penetrator is the tremendous heat applied to the penetrator unit when striking the shielding (surface) at hundreds of meters per second. This has partially been solved by using metals such as tungsten

Tungsten

Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...

(with a much higher melting point than steel), and altering the shape of the projectile (such as an ogive

Ogive

An ogive is the roundly tapered end of a two-dimensional or three-dimensional object.-Applied physical science and engineering:In ballistics or aerodynamics, an ogive is a pointed, curved surface mainly used to form the approximately streamlined nose of a bullet or other projectile.The traditional...

).

Altering the shape of the projectile to incorporate an ogive

Ogive

shape has yielded substantial results. Rocket sled

Rocket sled

A rocket sled is a test platform that slides along a set of rails, propelled by rockets.As its name implies, a rocket sled does not use wheels. Instead, it has sliding pads, called "slippers", which are curved around the head of the rails to prevent the sled from flying off the track...

testing at Eglin Air Force Base

Eglin Air Force Base

Eglin Air Force Base is a United States Air Force base located approximately 3 miles southwest of Valparaiso, Florida in Okaloosa County....

has demonstrated penetrations of 100 to 150 feet (45.7 m) in concrete when traveling at 4000 ft/s (1,219.2 m/s). The reason for this is liquefaction

Liquefaction

Liquefaction may refer to:* Liquefaction, the general process of becoming liquid* Soil liquefaction, the process by which sediments become suspended* Liquefaction of gases in physics, chemistry, and thermal engineering* Liquefactive necrosis in pathology...

of the concrete in the target, which tends to flow over the projectile. Variation in the speed of the penetrator can either cause it to be vaporized on impact (in the case of traveling too fast), or to not penetrate far enough (in the case of traveling too slow). An approximation for the penetration depth is obtained with an impact depth formula

Impact depth

The physicist Sir Isaac Newton first developed this idea to get rough approximations for the impact depth for projectiles traveling at high velocities.-Newton's approximation for the impact depth:...

derived by Sir Isaac Newton.

Combination penetrator-explosive munitions

Another school of thought on nuclear bunker busters is using a light penetrator to travel 15 to 30 meters through shielding, and detonate a nuclear charge there. Such an explosion would generate powerful shock waves, which would be transmitted very effectively through the solid material comprising the shielding (see "scabbing" above).

Criticism

The main criticisms of nuclear bunker busters regard nuclear fallout

Nuclear fallout

and nuclear proliferation. The purpose of an earth-penetrating nuclear "bunker buster" is to reduce the required yield needed to ensure the destruction of the target by coupling the explosion to the ground, yielding a shock wave similar to an earthquake. For example, the United States retired the B-53 warhead

B53 nuclear bomb

The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of , was the most powerful weapon in the U.S...

, with a yield of 9 megatons

TNT equivalent

TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...

, because the B-61 Mod 11

B61 nuclear bomb

The B61 nuclear bomb is the primary thermonuclear weapon in the U.S. Enduring Stockpile following the end of the Cold War. It is an intermediate yield strategic and tactical nuclear weapon featuring a two-stage radiation implosion design....

could attack similar targets with much lower yield (400 kilotons), due to the latter's superior ground penetration. Thus the fallout of a B-61 Mod 11 would likely be less than that of a B-53. Supporters note that this is one of the reasons nuclear bunker busters should be developed. Critics claim that developing new nuclear weapons sends a proliferating message to non-nuclear powers, undermining non-proliferation efforts.

Critics also worry that the existence of lower-yield nuclear weapons for relatively limited tactical purposes will lower the threshold for their actual use, thus blurring the sharp line between conventional weapons intended for use and weapons of mass destruction intended only for hypothetical deterrence and increasing the risk of escalation to higher-yield nuclear weapons.

Fallout from any nuclear detonation is increased with proximity to the ground. While a megaton-class yield will inevitably throw up many tons of (newly) radioactive debris, which falls back to the earth as fallout, critics contend that despite their relatively minuscule explosive yield, nuclear bunker busters create more fallout per kiloton yield. Also, because of the subsurface detonation, radioactive debris may contaminate the local groundwater.

The Union of Concerned Scientists

Union of Concerned Scientists

The Union of Concerned Scientists is a nonprofit science advocacy group based in the United States. The UCS membership includes many private citizens in addition to professional scientists. James J...

advocacy group points out that, at the Nevada Test Site

Nevada Test Site

The Nevada National Security Site , previously the Nevada Test Site , is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about northwest of the city of Las Vegas...

, the depth required to contain fallout from an average-yield nuclear test

Nuclear testing

Nuclear weapons tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Throughout the twentieth century, most nations that have developed nuclear weapons have tested them...

was over 100 meters, depending upon the weapon's yield. They contend that it is improbable that penetrators could be made to burrow so deeply. With yields between 0.3 and 340 kilotons, they argue, it is unlikely the blast would be completely contained.

Another criticism is that bunkers can be built at greater depth to make them more difficult to reach. The target's vulnerability is then limited to openings like the ventilation system, which are susceptible to conventional explosives. Proponents of nuclear bunker busters respond that deeper bunkers entail higher costs, limiting the potential enemies who can withstand nuclear bunker busters.

Politically, as well, such nuclear bunker busters are unpopular. Most targets are near cities, critics argue, and even minimal fallout will inflict unacceptable levels of collateral damage. Furthermore, they state, the testing of new nuclear weapons would be prohibited by the proposed Comprehensive Test Ban Treaty

Comprehensive Test Ban Treaty

The Comprehensive Nuclear-Test-Ban Treaty bans all nuclear explosions in all environments, for military or civilian purposes. It was adopted by the United Nations General Assembly on 10 September 1996 but it has not entered into force.-Status:...

. Although Congress refused to ratify the CTBT in 1999, the United States has adhered to the spirit of the treaty by maintaining a moratorium on nuclear testing since 1992.

Finally, the need to use nuclear weapons in this role is questioned by critics. They argue that conventional ground-penetration weapons are able to destroy enough buried or strengthened sites to lessen or even remove the need to use nuclear technology. Other conventional weapons such as thermobaric weapon

Thermobaric weapon

A thermobaric weapon, which includes the type known as a "fuel-air bomb", is an explosive weapon that produces a blast wave of a significantly longer duration than those produced by condensed explosives. This is useful in military applications where its longer duration increases the numbers of...

s have proven effective in defeating buried targets which have not been hardened.

Development of bunker-busting weapons

As early as 1944, the Wallis Tallboy bomb

Tallboy bomb

The Tallboy or Bomb, Medium Capacity, 12,000 lb, was an earthquake bomb developed by the British aeronautical engineer Barnes Wallis and deployed by the RAF in 1944...

and subsequent Grand Slam

Grand Slam bomb

The Grand Slam was a 22,000 lb earthquake bomb used by RAF Bomber Command against strategic targets during the Second World War.Known officially as the Bomb, Medium Capacity, 22,000 lb, it was a scaled up version of the Tallboy bomb and closer to the original size that the bombs' inventor,...

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

Valentin submarine pens

The Valentin submarine pens are a protective shelter built to construct German U-boats during World War II at Farge, a small port on the Weser River in Bremen. The pens were under construction from 1943 to March 1945 using forced labour, but were damaged by air-raids and unfinished by the end of...

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

Camouflet

A camouflet, in military science, is an artificial cavern created by an explosion. If the explosion reaches the surface then it is called a crater....

(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

V-3 cannon

The V-3 was a German World War II supergun working on the multi-charge principle whereby secondary propellant charges are fired to add velocity to a projectile....

at Mimoyecques was the first operational use of the Tallboy. One bored through a hillside and exploded in the Saumur

Saumur

Saumur is a commune in the Maine-et-Loire department in western France.The historic town is located between the Loire and Thouet rivers, and is surrounded by the vineyards of Saumur itself, Chinon, Bourgueil, Coteaux du Layon, etc...

rail tunnel about 18 m (60 ft) below, completely blocking it thus showing that these weapons could destroy any hardened or deeply excavated

Earthworks (engineering)

Earthworks are engineering works created through the moving or processing of quantities of soil or unformed rock.- Civil engineering use :Typical earthworks include roads, railway beds, causeways, dams, levees, canals, and berms...

installation. Modern targeting techniques allied with multiple strikes could unquestionably perform a similar task.

Development continued, with weapons such as the nuclear B61

B61 nuclear bomb

, and conventional thermobaric weapons and GBU-28

GBU-28

The Guided Bomb Unit 28 is a 5,000 pound laser-guided "bunker busting" bomb nicknamed "Deep Throat" produced originally by the Watervliet Arsenal, Watervliet, New York. It was designed, manufactured, and deployed in less than three weeks due to an urgent need during Operation Desert Storm to...

. 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 howitzer

Howitzer

A howitzer is a type of artillery piece characterized by a relatively short barrel and the use of comparatively small propellant charges to propel projectiles at relatively high trajectories, with a steep angle of descent...

s) to penetrate 6 meters (20 ft) of concrete, and more than 30 meters (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 (30.5 m) were sufficient for some shallow targets, both the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

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 out of this Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

context.

The weapon was revisited after the Cold War during the 2001 U.S. invasion of Afghanistan

War in Afghanistan (2001–present)

The War in Afghanistan began on October 7, 2001, as the armed forces of the United States of America, the United Kingdom, Australia, and the Afghan United Front launched Operation Enduring Freedom...

, and again during the 2003 invasion of Iraq

2003 invasion of Iraq

The 2003 invasion of Iraq , was the start of the conflict known as the Iraq War, or Operation Iraqi Freedom, in which a combined force of troops from the United States, the United Kingdom, Australia and Poland invaded Iraq and toppled the regime of Saddam Hussein in 21 days of major combat operations...

. During the campaign in Tora Bora

Tora Bora

Tora Bora , known locally as Spīn Ghar , is a cave complex situated in the White Mountains of eastern Afghanistan, in the Pachir Wa Agam District of Nangarhar province, approximately west of the Khyber Pass and north of the border of the Federally Administered Tribal Areas in Pakistan...

in particular, the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

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 DOE

United States Department of Energy

The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...

was allotted budget to develop it, and tests were conducted by the Air Force Research Laboratory

Air Force Research Laboratory

The Air Force Research Laboratory is a scientific research organization operated by the United States Air Force Materiel Command dedicated to leading the discovery, development, and integration of affordable aerospace warfighting technologies; planning and executing the Air Force science and...

.

The Bush

George W. Bush

George Walker Bush is an American politician who served as the 43rd President of the United States, from 2001 to 2009. Before that, he was the 46th Governor of Texas, having served from 1995 to 2000....

administration removed its request for funding of the weapon in October 2005. Additionally, US Senator Pete Domenici

Pete Domenici

Pietro Vichi "Pete" Domenici is an American Republican politician, who served six terms as a United States Senator from New Mexico, from 1973 to 2009, the longest tenure in the state's history....

announced funding for the nuclear bunker-buster has been dropped from the Department of Energy

United States Department of Energy

's fiscal 2006 budget at the department's request.

While the project for the RNEP seems to be in fact canceled, Jane's Information Group

Jane's Information Group

Jane's Information Group is a publishing company specializing in transportation and military topics.-History:It was founded by Fred T...

speculated in 2005 that work might continue under another name.

External links

Earth Penetrating Weapons, Lisbeth Gronlund, David Wright and Robert Nelson, Union of Concerned Scientists, May 2005
Bunker-busters set to go nuclear, David Hambling, New Scientist, 7 November 2002
Low-Yield Earth-Penetrating Nuclear Weapons, Robert W. Nelson, Federation of American Scientists, January/February 2001, Volume 54, Number 1
The B61-based "Robust Nuclear Earth Penetrator:" Clever retrofit or headway towards fourth-generation nuclear weapons?, Andre Gsponer, Independent Scientific Research Institute, 31 March 2007

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