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Encyclopedia > Robust Nuclear Earth Penetrator

The Robust Nuclear Earth Penetrator (RNEP) is a theoretical weapon intended to pentrate reinforced, underground bunkers belived to be immune to existing weapons. The US Air Force Research Laboratory researched the concept, but the United States Congress cancelled funding for the project in October 2005 at the National Nuclear Security Administration's request. No government or military sources have stated that the RNEP exists. A bunker is a defensive warfare fortification to protect personnel or equipment. ... The United States Air Force Research Laboratory with headquarters at Wright-Patterson Air Force Base, Ohio, was created in October 1997. ... The Congress of the United States is the legislative branch of the federal government of the United States of America. ...

Military theorists expressed interest in the RNEP as a tool to counter technical advances in the design and construction of underground bunkers that house weapons, equipment and key personnel. Rendering useless such bunkers weakens the defensive position of an adversary.

The RNEP would strike the ground above a bunker and penetrate through protective layers of earth and reinforced concrete. The undamaged nuclear warhead would detonate upon reaching a designated depth. Reinforced concrete at Sainte Jeanne dArc Church (Nice, France): architect Jacques Dror, 1926–1933 Reinforced concrete (Ferro concrete) is plain concrete in which reinforcement in the form of rods, bars (rebars) or fibers have been incorporated to strengthen the naturally brittle concrete. ...



Weapons scientists have not proven the feasibility of building a warhead rugged enough to penetrate many meters of earth and concrete. The warhead would need to strike the ground with very high velocity in order to maintain sufficient force to penetrate fortifications. At the same time, the warhead must be strong enough to maintain structural integrity when striking the ground and travelling through underground debris.

Methods of Penetration

Penetration by explosive force

Concrete design remains little changed since 60 years ago. 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, fibers, and rebar, have made concrete less vulnerable, but far from impenetrable. Raymond T. Moore [1] was able to create a "human sized hole" in 18 inch thick (45 cm) thick reinforced concrete in less than 48 seconds with a mere 20 lb (9 kg) of explosive and a bolt cutter. The materials definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly to below its glass transition temperature, thereby not giving enough time for a regular crystal lattice to form. ... Fiber (American English) or fibre (Commonwealth English) is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to pieces of thread. ... A tied rebar beam cage. ...

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 opposite side of the crater. Scabbing, also known as "spalling," 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. Spall are flakes of a material that are broken off a larger solid body. ...

The crater volume varies approximately inversely with the square root of the concrete's compressive strength. Therefore, increasing the compressive strength of the concrete by 50% will yield an approximately 25% smaller crater.

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.

Therefore, there is an asymptotic relationship between the strength of the concrete and the damage that will be done between the crater, aggregate, and scabbing. It is impossible to create a concrete impervious to penetration by explosive. The nature of concrete as a hard surface means that it will suffer extreme damage when subjected to shock wave. In mathematics and applications, particularly the analysis of algorithms, asymptotic analysis is a method of classifying limiting behaviour, by concentrating on some trend. ... In fluid dynamics, a shock wave is a nonlinear or discontinuous pressure wave. ...

Penetration with a purpose-built hardened penetrator

This form of penetration is more difficult.

A hypothetical GBU-12 that weighed only 227 kg (this is in fact only the weight of the explosive payload of a real GBU-12) able to reach the same speed of 488 m/s would release 27 megajoules of energy simply by striking the ground at that velocity. This amount of energy can be represented in heat as 25,600 BTU. A megajoule (abbreviation: MJ) is a unit of energy equal to 1000000 joules. ... A red-hot iron rod cooling after being worked by a blacksmith. ... The British thermal unit (BTU) is a non-metric unit of energy, used in the United States and, to a certain extent, the UK. The SI unit is the joule (J), which is used by most other countries. ...

A projectile must continue to travel through the material protecting the target without deforming or melting in this very harsh environment. Such a feat may be possible (to some extent) with tungsten, which has a melting point of 3422 °C (6,192 °F). General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Atomic mass 183. ...

In the case of concrete and sand, little research exists on the friction encountered by a projectile traveling through either. One can imagine, however, that a projectile traveling through concrete would be subject to very high friction, and even tungsten would reach a point of deformation and even liquefaction. In physics, to liquefy or liquify means to turn something into the liquid state. ...

Despite this seemingly inevitable outcome of tungsten/concrete interaction, penetration research at Sandia National Labs and Eglin Air Force Base has found that there is a "sweet spot," as it were, when penetrating substances such as concrete. Sandia National Laboratories is a major United States Department of Energy research and development national laboratory with two locations, one in Albuquerque, New Mexico and the other in Livermore, California. ... Eglin Air Force Base is a base of the United States Air Force that belongs to the Air Force Materiel Command; the Air Armament Center is the host unit. ...

If the hypothetical projectile reaches a speed of 10,000 feet per second (3,000 m/s) or approximately Mach 9, it simply sublimates (i.e., vaporizes) when it hits the ground. If it hits the ground at 1,600 ft/s (500 m/s), as described above, approximately 15 feet (5 m) of penetration is achieved. The weapon is ineffective in both scenarios. Mach number (Ma) is defined as a ratio of speed to the speed of sound in the medium in case. ... Sublimation of an element or substance is a conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. ...

However, if the projectile travels at 4,000 ft/s (1,200 m/s) or mach 3.5, the concrete begins to liquefy as the projectile impacts it. Assuming a traditional ogive penetrator is used, very little damage is actually done to the projectile. The liquefied concrete actually damages the side and rear of the penetrator slightly, but it arrives essentially intact at the end of its journey. Penetrations of 100 to 150 feet (30 to 45 m) of concrete are possible with this method. In ballistics or aerodynamics, an ogive is a pointed, curved surface used to form the approximately streamlined nose of a bullet, shell, missile or aircraft. ...

Of course, similar assumptions can be made about substances other than concrete, and the liquefaction of solids is well understood. Much of this research is classified, and there are no real available sources outside of informal conversations with those involved in said research.

Destruction of a buried target through light penetration and nuclear explosion

With light penetration of about 15 to 30 meters underground, the detonation of a nuclear weapon would transmit shock waves very deep into the Earth, which might destroy deeply buried targets. Obviously, the effectiveness of the weapon would depend on the depth of the target and the yield of the explosion. Current weapons under discussion for this use range from 0.3 to 340 kilotons. The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the hypocenter. ...

Nuclear weapons are perhaps most famous for their byproduct: nuclear fallout. Scientists in favor of an RNEP have stated that if a target is penetrated deeply enough, for instance to 200 feet (60 m), and the warhead is sufficiently low-yield and designed to produce very little radiation, the explosion occurring underground would be sufficient to contain the fallout. Fallout is the residual radiation hazard from a nuclear explosion and is named from the fact that it falls out of the atmosphere in to which it is spread during the explosion. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles (radiation). ...

The Union of Concerned Scientists points out that at the Nevada Test Site, the depth required to contain fallout from a nuclear test was between 100 and 500 meters. It is improbable that any type of bomb or missile could be made to penetrate so deeply. The Union of Concerned Scientists as defined on the UCS website: The Union of Concerned Scientists is a nonprofit partnership of scientists and citizens combining rigorous scientific analysis, innovative policy development, and effective citizen advocacy to achieve practical environmental solutions. ... November 1951 nuclear test at Nevada Test Site - Test is shot Dog from Operation Buster, 21 kilotons. ... A nuclear test explosion is an experiment involving the detonation of a nuclear weapon. ...

Present weapons are capable of penetrating no greater than 30 meters (about 90 feet). They have been used effectively in war, but against targets closer to the surface, not deeply buried targets. War is a state of widespread conflict between states, organisations, or relatively large groups of people, which is characterised by the use of lethal violence between combatants or upon civilians. ...

Political ramifications of an RNEP

Assuming the RNEP is a technologically feasible concept, there are political problems.

Subsidence craters left over after underground nuclear explosions
Subsidence craters left over after underground nuclear explosions

Low-radiation, low-yield (possibly in the sub-kiloton range) weapons would not leave a large area irradiated for generations or kill hundreds or thousands of people in a giant mushroom cloud. Instead they would leave a subsidence crater and some seismic activity. On nuclear test ranges, however, it has been found that especially large weapons will leave a "chimney" or "smokestack" at the bottom of the hole, leading to the underground site of the original explosion. It is possible through this aperture that radioactive smoke and debris could rise to contaminate the local atmosphere. The crater-scarred landscape of the Nevada Test Site. ... The crater-scarred landscape of the Nevada Test Site. ... Post-shot subsidence crater and Huron King test chamber, which was less than 20 kilotons (1980) A subsidence crater is the crater left on the surface of an area which has had an underground (usually nuclear) explosion. ... Irradiation is the process by which an item is exposed to radiation. ... The atomic bombing of Nagasaki on August 9, 1945 A mushroom cloud is a distinctive mushroom-shaped cloud of smoke, flame, or debris resulting from a very large explosion. ... Post-shot subsidence crater and Huron King test chamber, which was less than 20 kilotons (1980) A subsidence crater is the crater left on the surface of an area which has had an underground (usually nuclear) explosion. ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth. ...

In October 2005, the Bush administration removed its request for funding the weapon, essentially halting the program.[1]


  1. Moore, Raymond. T.: Barrier penetration tests. National Bureau of Standards Technical Note 837 (1974)
  2. Penetration Resistance of Concrete: A Review, James R. Clifton, for the Physical Security and Stockpile Directorate, Defense Nuclear Agency. January 1992.

See also

Bunker-busting nuclear weapons are a proposed type of nuclear weapon that would be designed to penetrate into soil, rock or concrete to deliver a low-yield nuclear warhead. ... The B61 nuclear bomb is the primary thermonuclear weapon in the U.S. Enduring Stockpile following the end of the Cold War. ...

External links

  • Union of Concerned Scientists article on Earth Penetrating Weapons (EPW)
  • New Scientist article

  Results from FactBites:
The Robust Nuclear Earth Penetrator (RNEP) (700 words)
The Robust Nuclear Earth Penetrator (RNEP) is a nuclear weapon that would burrow a few meters into rock or concrete before exploding and thus generating a powerful underground shock wave.
For comparison, even a one-kiloton nuclear warhead (less than 1/10th as powerful as the Hiroshima bomb) must be buried at least 200-300 feet to contain its radioactive fallout.[3] The high yield RNEP will produce tremendous fallout that will drift for more than a thousand miles downwind.
RNEP would not be effective at destroying chemical or biological agents:  Unless the weapon detonates nearly in the same room with the agents, it will not destroy them.
NRDC: The Bush Administration's Misguided Quest for Low-Yield Nuclear Bunker Busters (1416 words)
Opponents of Bush's "revitalized" nuclear weapons program are expected to offer amendments in the Senate to reinstate the ban, and in both houses to cut funding for the robust nuclear earth penetrator.
The robust nuclear earth penetrator proposal is symptomatic of an increasingly disconnected nuclear weapons establishment in search of a mission.
As for the ongoing development of a high-yield robust nuclear earth penetrator warhead, it is nothing more than "workfare" for federal nuclear weapons laboratories, and a retread of the very Cold War policies the Bush administration pledged to jettison.
  More results at FactBites »



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