Insensitive munitions
Encyclopedia
Insensitive munitions are munitions
that are chemically stable
enough to withstand mechanical shocks
, fire, and impact by shrapnel, but that can still explode as intended to destroy their targets.
s, shrapnel
, shaped charge
s or the detonation of another nearby munition. The term refers to warhead
s, bomb
s, rocket motors, although different countries' armed forces may have their own definitions.
Due to “accidents, and the subsequent loss of human life, cost of repairing and replacing materiel, and the toll taken on operational readiness and capability, Insensitive Munitions (IM) improvements are mandated by law in the U.S."
Three approaches are taken when designing insensitive munitions: Firstly, the high energy device can be protected and transported with an external protection of some kind. Some munition shipping containers are designed to provide some protection and thermal insulation
. Secondly, the chemistry of the high energy fill is chosen to provide a higher degree of stability, for example by using plastic bonded explosives
. Lastly, the casings of high energy devices can be designed in such a way as to allow venting or some other form of pressure relief
in a fire.
Beyond the three approaches above, other threats need addressing when designing IM, e.g., slow and fast cook-off, sympathetic detonation
, bullet and fragment impact, and shaped charge
jet impact. Extensive testing requirements for potential IM candidates to address these threats are extremely costly. Modeling programs are being designed to simulate the threat of bullet and fragment impact in an effort to reduce testing costs. One of the most promising methods that engineers and scientists within the U.S. Department of Defense (DoD) are employing to help to enhance IM performance is by using advanced multiphysics
modeling programs. Also, another effort is underway developing 2-D numerical code that will simulate the threat of slow and fast cook-off.
(IHE) such as triaminotrinitrobenze (TATB
) or various insensitive explosive mixtures, or plastic/polymer-bonded explosive
s, which are similar to reactive material
s. TATB particularly will not detonate if impacted by typical fragments or burned in a fire.
A new IHE called Insensitive Munitions Explosive (IMX-101), has been qualified and approved by the U.S. Army to replace trinitrotoluene (TNT). IMX-101 is said to have the “same lethality as traditional TNT, but is far less likely to explode if dropped, shot at or hit by a roadside bomb during transport”. This IHE has been tested and proven to be a safer alternative within large-caliber projectiles currently utilized by the Army and Marine Corps.
Another IHE, experimental, is FOX-7
.
IHEs often combine amino groups and nitro groups in the same molecule.
enough to withstand the forces involved in an aircraft accident. The Lawrence Livermore National Laboratory
developed the "Susan Test" — a standard test designed to simulate an aircraft accident by squeezing and nipping explosive material between metal surfaces of a test projectile. Following experiments with this device, the Los Alamos National Laboratory
developed a new safer type of explosive, called insensitive high explosive (IHE), for use in U.S. nuclear weapons.
IHE explosives can withstand impacts up to 1500 feet per second (457.2 m/s), as opposed to conventional HE, which will detonate at only 100 feet per second (30.5 m/s).
, and at least those of the United Kingdom
, are manufactured using insensitive munition designs. These are almost exclusively TATB
plastic bonded explosive (LX-17-0 and PBX-9502). Conventional high explosives are still used in missile
s and nuclear artillery
shells where weight and volume is a factor (IHE by weight contains only two-thirds the energy of HE, so more is needed to achieve the same effect).
Ammunition
Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...
that are chemically stable
Chemical stability
Chemical stability when used in the technical sense in chemistry, means thermodynamic stability of a chemical system.Thermodynamic stability occurs when a system is in its lowest energy state, or chemical equilibrium with its environment. This may be a dynamic equilibrium, where individual atoms...
enough to withstand mechanical shocks
Shock (mechanics)
A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
, fire, and impact by shrapnel, but that can still explode as intended to destroy their targets.
Description
Insensitive munitions (IM) will only burn (rather than explode) when subjected to fast or slow heating, bulletBullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...
s, shrapnel
Fragmentation (weaponry)
Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...
, shaped charge
Shaped charge
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...
s or the detonation of another nearby munition. The term refers to 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...
s, bomb
Bomb
A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
s, rocket motors, although different countries' armed forces may have their own definitions.
Due to “accidents, and the subsequent loss of human life, cost of repairing and replacing materiel, and the toll taken on operational readiness and capability, Insensitive Munitions (IM) improvements are mandated by law in the U.S."
Three approaches are taken when designing insensitive munitions: Firstly, the high energy device can be protected and transported with an external protection of some kind. Some munition shipping containers are designed to provide some protection and thermal insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...
. Secondly, the chemistry of the high energy fill is chosen to provide a higher degree of stability, for example by using plastic bonded explosives
Plastic explosive
Plastic explosive is a specialised form of explosive material. It is a soft and hand moldable solid material. Plastic explosives are properly known as putty explosives within the field of explosives engineering....
. Lastly, the casings of high energy devices can be designed in such a way as to allow venting or some other form of pressure relief
Relief valve
The relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire....
in a fire.
Beyond the three approaches above, other threats need addressing when designing IM, e.g., slow and fast cook-off, sympathetic detonation
Sympathetic detonation
A sympathetic detonation , also called flash over, is a detonation, usually unintended, of an explosive charge by a nearby explosion. Sympathetic detonation is caused by a shock wave, or impact of primary or secondary blast fragments.The initiating explosive is called donor explosive, the initiated...
, bullet and fragment impact, and shaped charge
Shaped charge
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...
jet impact. Extensive testing requirements for potential IM candidates to address these threats are extremely costly. Modeling programs are being designed to simulate the threat of bullet and fragment impact in an effort to reduce testing costs. One of the most promising methods that engineers and scientists within the U.S. Department of Defense (DoD) are employing to help to enhance IM performance is by using advanced multiphysics
Multiphysics
Multiphysics treats simulations that involve multiple physical models or multiple simultaneous physical phenomena. For example, combining chemical kinetics and fluid mechanics or combining finite elements with molecular dynamics...
modeling programs. Also, another effort is underway developing 2-D numerical code that will simulate the threat of slow and fast cook-off.
Insensitive high explosives
Insensitive munitions are almost always filled with fire resistant, shock resistant insensitive high explosivesExplosive material
An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure...
(IHE) such as triaminotrinitrobenze (TATB
TATB
TATB, or triaminotrinitrobenzene, is an aromatic explosive, based on the basic six-carbon benzene ring structure with three nitro functional groups and three amine groups attached, alternating around the ring....
) or various insensitive explosive mixtures, or plastic/polymer-bonded explosive
Polymer-bonded explosive
A polymer-bonded explosive, also called PBX or plastic-bonded explosive, is an explosive material in which explosive powder is bound together in a matrix using small quantities of a synthetic polymer...
s, which are similar to reactive material
Reactive material
In the US military, reactive materials are a new class of materials currently being investigated by the Office of Naval Research and others as a means to increase the lethality of direct-hit or fragmentation warheads...
s. TATB particularly will not detonate if impacted by typical fragments or burned in a fire.
A new IHE called Insensitive Munitions Explosive (IMX-101), has been qualified and approved by the U.S. Army to replace trinitrotoluene (TNT). IMX-101 is said to have the “same lethality as traditional TNT, but is far less likely to explode if dropped, shot at or hit by a roadside bomb during transport”. This IHE has been tested and proven to be a safer alternative within large-caliber projectiles currently utilized by the Army and Marine Corps.
Another IHE, experimental, is FOX-7
FOX-7
FOX-7 or 1,1-diamino-2,2-dinitroethene ' is an insensitive high power explosive compound. It was first synthesized in 1998 by the FOA Defence Research Establishment ....
.
IHEs often combine amino groups and nitro groups in the same molecule.
Origin
Following the 1966 Palomares B-52 crash and the 1968 Thule Air Base B-52 crash, concerns were raised by accident investigators about the high explosive used in the nuclear devices, which had detonated on impact. Efforts were started to find an explosive that was stableChemical stability
Chemical stability when used in the technical sense in chemistry, means thermodynamic stability of a chemical system.Thermodynamic stability occurs when a system is in its lowest energy state, or chemical equilibrium with its environment. This may be a dynamic equilibrium, where individual atoms...
enough to withstand the forces involved in an aircraft accident. The Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory
The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...
developed the "Susan Test" — a standard test designed to simulate an aircraft accident by squeezing and nipping explosive material between metal surfaces of a test projectile. Following experiments with this device, the Los Alamos National Laboratory
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
developed a new safer type of explosive, called insensitive high explosive (IHE), for use in U.S. nuclear weapons.
IHE explosives can withstand impacts up to 1500 feet per second (457.2 m/s), as opposed to conventional HE, which will detonate at only 100 feet per second (30.5 m/s).
Use in nuclear weapons
Insensitive high explosive has been available to the United States military for use in its nuclear weapons since 1979—by 1991, 25% of the country's nuclear stockpile was using IHE. Most modern American nuclear weaponsNuclear weapons and the United States
The United States was the first country to develop nuclear weapons, and is the only country to have used them in warfare, with the separate bombings of Hiroshima and Nagasaki in World War II. Before and during the Cold War it conducted over a thousand nuclear tests and developed many long-range...
, and at least those of the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, are manufactured using insensitive munition designs. These are almost exclusively TATB
TATB
TATB, or triaminotrinitrobenzene, is an aromatic explosive, based on the basic six-carbon benzene ring structure with three nitro functional groups and three amine groups attached, alternating around the ring....
plastic bonded explosive (LX-17-0 and PBX-9502). Conventional high explosives are still used in missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
s and nuclear artillery
Nuclear artillery
Nuclear artillery is a subset of limited-yield tactical nuclear weapons, in particular those weapons that are launched from the ground at battlefield targets...
shells where weight and volume is a factor (IHE by weight contains only two-thirds the energy of HE, so more is needed to achieve the same effect).