A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Various types are used to cut and form metal, initiate nuclear weapons, and penetrate armour. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Armour (or armor) is protective covering most commonly manufactured from metals to prevent damage from being inflicted to an individual or a vehicle through use of direct contact A typical modern lined shaped charge can penetrate armour steel to a depth of 7 or more times the diameter of the charge's cone (cone diameters, CD), though greater depths of 10 CD and above are now feasible.
Contents |
Overview
Shaped charges are frequently used as warheads in anti-tank missiles (guided and unguided) and also gun-fired projectiles (spun and unspun), rifle grenades, mines, bomblets, torpedoes and various types of air/land/sea-launched guided missiles. They are also used to demolish large obsolete structures by precisely placed and progressively timed cutting charges with the intent of causing an inward collapse that confines the debris to the structure's footprint. Demolition is the opposite of Construction: the tearing-down of Buildings and other Structures It contrasts with deconstruction Shaped charges are today used most extensively in the petroleum and natural gas industries, in particular in the completion of oil and gas wells, in which they are detonated to perforate the metal casing of the well at intervals to admit the influx of oil and gas. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, A perforation in the context of Oil wells refers to a hole punched in the casing or liner of an Oil well to connect it to the reservoir [1]
A typical device consists of a solid cylinder of explosive with a metal-lined conical hollow in one end and a central detonator, array of detonators, or detonation wave guide at the other end. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied For the Ratt album see Detonator (album A detonator is a device used to trigger an Explosive device. Detonation is a process of Supersonic Combustion in which a Shock wave is propagated forward due to energy release in a reaction zone behind it The enormous pressure generated by the detonation of the explosive drives the liner contained within the hollow cavity inward to collapse upon its central axis. The resulting collision forms and projects a high-velocity jet of metal forward along the axis. Most of the jet material originates from the innermost layer of the liner, about 10% to 20% of its thickness. The remaining liner material forms a slower-moving slug of material, which because of its appearance is sometimes called a "carrot. "
Because of variations along the liner in its collapse velocity, the jet so formed has a varying velocity along its length, decreasing from the front. This variation in velocity stretches the jet and eventually leads to its break-up into particles. In time, the particles tend to lose their alignment, which reduces the depth of penetration at long standoffs.
Also, at the apex of the cone, which forms the very front of the jet, the liner does not have time to be fully accelerated before it forms its part of the jet. This results in its small part of jet being projected at a lower velocity than jet formed later behind it. As a result, the initial parts of the jet coalesce to form a pronounced wider tip portion.
Most of the jet formed moves at hypersonic speed, the tip at 7 to 14 km/s, the jet tail at a lower velocity (1 to 3 km/s), and the slug at a still lower velocity (less than 1 km/s). In Aerodynamics, hypersonic speeds are speeds that are highly Supersonic. The exact velocities are dependent on the charge's configuration and confinement, explosive type, materials used, and the explosive-initiation mode. At typical velocities, the penetration process generates such enormous pressures that it may be considered hydrodynamic; to a good approximation, the jet and armor may be treated as incompressible fluids, with their material strengths ignored. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion
The liner
The shape most commonly used for the liner is a cone, with an internal apex angle of 40 to 90 degrees. A cone is a three-dimensional Geometric shape that tapers smoothly from a flat round base to a point called the apex or vertex Different apex angles yield different distributions of jet mass and velocity. Small apex angles can result in jet bifurcation, or even in the failure of the jet to form at all; this is attributed to the collapse velocity being above a certain threshold, normally slightly higher than the liner material's bulk sound speed. Other widely used shapes include hemispheres, tulips, trumpets, ellipses, and bi-conics; the various shapes yield jets with different velocity and mass distributions.
Liners have been made from many materials, including glass and various metals. The deepest penetrations are achieved with a dense, ductile metal, and a very common choice has been copper. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 For some modern anti-armor weapons, molybdenum and pseudo-alloys of tungsten filler and copper binder (9:1 thus density is ~18t/m3) have been adopted. Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 The reaper-binder, or binder, was a farm implement that improved upon the Reaper. Just about every common metallic element has been tried, including aluminium, tungsten, tantalum, depleted uranium, lead, tin, cadmium, cobalt, magnesium, titanium, zinc, zirconium, molybdenum, beryllium, nickel, silver, and even gold and platinum. WikipediaNaming Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 Tantalum (ˈtæntələm (formerly tantalium /tænˈtæliəm/ is a Chemical element with the symbol Ta and Atomic number 73 Depleted uranium (DU is Uranium primarily composed of the Isotope Uranium-238 (U-238 Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 Zirconium (zɚˈkoʊniəm /ˌzɝˈkoʊniəm/ is a Chemical element with the symbol Zr and Atomic number 40 Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Silver (ˈsɪlvɚ is a Chemical element with the symbol " Ag " (argentum from the Ancient Greek: ἀργήντος - argēntos gen Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 The selection of the material depends on the target to be penetrated; for example, aluminium has been found advantageous for concrete targets.
For the deepest penetrations, pure metals yield the best results, because they display the greatest ductility, hence postponing the breakup of the stretching jet into particles. In charges for oil-well completion, however, it is essential that a solid slug or "carrot" not be formed, since it would plug the hole just penetrated and interfere with the influx of oil. In the petroleum industry, therefore, liners are generally fabricated by powder metallurgy, often of pseudo-alloys, which if un-sintered, yield jets that are composed mainly of dispersed fine metal particles. Powder metallurgy is a forming and fabrication technique consisting of three major processing stages Sintering is a method for making objects from powder, by heating the material (below its Melting point - solid state sintering until its particles adhere
During World War II, liners were made of copper or steel, though other materials were tried or researched. The precision of the charge's construction and its detonation mode were both inferior to modern warheads. This lower precision caused the jet to curve and to break up at an earlier time and hence at a shorter distance. The resulting dispersion decreased the penetration depth for a given cone diameter and also shortened the optimum standoff distance. Since the charges were less effective at larger standoffs, side and turret skirts (known as Schürzen) fitted to some German tanks to protect against Russian anti-tank rifle fire [2]were fortuitously found to give the jet room to disperse and hence reduce its penetrating ability.
The use of skirts today may increase the penetration of some warheads. Due to constraints in the length of the projectile/missile, the built in stand-off on many warheads is not the optimum distance. The skirting effectively increases the distance between the armour and the target, providing the warhead with a more optimum standoff and greater penetration if the optimum stand-off is not drastically exceeded. Skirting should not be confused with bar/slat/chain armour which is used to damage the fuzing system of RPG-7 projectiles. The RPG-7 (РПГ-7 is a widely-produced portable shoulder-launched, Anti-tank Rocket propelled grenade weapon The armour works by deforming the inner and outer ogives and shorting the firing circuit between the rocket's piezoelectric nose probe and rear fuze assembly. An ogive ("Oh-jive" is a curved shape figure or feature Piezoelectricity is the ability of some materials (notably Crystals and certain Ceramics including bone to generate an Electric potential in response to If the nose probe strikes the armour, the warhead will function as normal.
The spacing between the shaped charge and its target is critical, as there is an optimum standoff distance to achieve the deepest penetration. At short standoffs, the jet does not have room to stretch out, and at long standoffs, it eventually breaks into particles, which then tend to drift off the line of axis and to tumble, so that the successive particles tend to widen rather than deepen the hole. At very long standoffs, velocity is lost to air drag, degrading penetration further.
The explosive
For optimum penetration, a high explosive having a high detonation velocity and pressure is normally chosen. The most common explosive used in high performance anti-armour warheads is HMX (octogen), though it is never used on its own, as it would be too sensitive. HMX, also called octogen, is a powerful and relatively insensitive Nitroamine High explosive, chemically related to RDX. It is normally compounded with a few percent of some type of plastic binder, such as in the plastic bonded explosive (PBX) LX-14, or with another less-sensitive explosive, such as TNT, with which it forms Octol. Trinitrotoluene ( TNT) is a Chemical compound with the formula C6H2(NO23CH3 Octol is a melt-castable high explosive mixture consisting of HMX and TNT in different weight proportions Other common explosives are RDX-based compositions, again either as PBXs or mixtures with TNT (to form Composition B and the Cyclotols) or wax (Cyclonites). Cyclotrimethylenetrinitramine, also known as RDX, cyclonite, hexogen, and T4, is an Explosive Nitroamine widely used Composition B is an Explosive consisting of castable mixtures of RDX and TNT as well as in some instances additional desensitizing agents Composition B is an Explosive consisting of castable mixtures of RDX and TNT as well as in some instances additional desensitizing agents Some explosives incorporate powdered aluminium to increase their blast and detonation temperature, but this addition generally results in decreased performance of the shaped charge. WikipediaNaming There has been research into using the very-high-performance but sensitive explosive CL-20 in shaped-charge warheads, but, at present, due to its sensitivity, this has been in the form of the PBX composite LX-19 (CL-20 and Estane binder). 24681012-hexanitro-24681012-hexaazaisowurtzitane, also called HNIW, and CL-20, is a Nitroamine explosive with the formula C6H6N12O12
Other features
A waveshaper is a body (typically a disc or cylindrical block) of an inert material (typically solid or foamed plastic, but sometimes metal, perhaps hollow) inserted within the explosive for the purpose of changing the path of the detonation wave. The effect is to modify the collapse of the cone and resulting jet formation, with the intent of increasing penetration performance. Waveshapers are often used to save space—a shorter charge can achieve the same performance as a longer one without a waveshaper.
Another useful design feature is sub-calibration, the use of a liner having a smaller diameter (calibre) than the explosive charge. In an ordinary charge, the explosive near the base of the cone is so thin that it is unable to accelerate the adjacent liner to sufficient velocity to form an effective jet. In a sub-calibrated charge, this part of the device is effectively cut off, resulting in a shorter charge with the same performance.
Shaped Charge Variants
There are several different forms of shaped charge.
Linear shaped charges
A linear shaped charge (LSC) has a liner with V-shaped profile and varying length. The liner is surrounded with explosive, the explosive then encased within a suitable material that serves to protect the explosive and to confine (tamp) it on detonation. The charge is detonated at some point in the explosive above the liner apex. The detonation projects the liner to form a continuous, knife-like (planar) jet. The jet cuts any material in its path, to a depth depending on the size and materials used in the charge. For the cutting of complex geometries, there are also flexible versions of the linear shaped charge, these with a lead or high-density foam sheathing and a ductile/flexible liner material, which also is often lead. LSCs are commonly used in the cutting of rolled steel joists (RSJ) and other structural targets, such as in the controlled demolition of buildings. Building implosion is a term in use in the Controlled demolition industry LSCs are also used to separate the stages of multi-stage rockets.
Explosively Formed Penetrator
The Explosively Formed Penetrator (EFP) is also known as the Self-Forging Fragment (SFF), Explosively Formed Projectile (EFP), SElf-FOrging Projectile (SEFOP), Plate Charge, and Misznay-Schardin (MS) Charge. An explosively formed penetrator (EFP is a type of Petard also known as an explosively formed projectile, a self-forging warhead, or a self-forging The Misznay-Schardin effect, or platter effect is a characteristic of the detonation of a broad sheet of Explosive. An EFP uses the action of the explosive's detonation wave (and to a lesser extent the propulsive effect of its detonation products) to project and deform a plate or dish of ductile metal (such as copper, iron, or tantalum) into a compact high-velocity projectile, commonly called the slug. This slug is projected towards the target at about two kilometres per second. The chief advantage of the EFP over a conventional (e. g. , conical) shaped charge is its effectiveness at very great standoffs, equal to hundreds of times the charge's diameter (perhaps a hundred meters for a practical device).
The EFP is relatively unaffected by first-generation reactive armour and can travel up to perhaps 1000 charge diameters (CDs) before its velocity becomes ineffective at penetrating armour due to aerodynamic drag, or successfully hitting the target becomes a problem. Reactive armour is a type of Vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected The impact of a ball or slug EFP normally causes a large-diameter but relatively shallow hole, of, at most, a couple of CDs. If the EFP perforates the armour, extensive behind armour effects (BAE, also called behind armour damage, BAD) will occur. The BAE is mainly caused by the high temperature and velocity armour and slug fragments being injected into the interior space and the overpressure (blast) caused by this debris. More modern EFP warhead versions, through the use of advanced initiation modes, can also produce long-rods (stretched slugs), multi-slugs and finned rod/slug projectiles. The long-rods are able to penetrate a much greater depth of armour, at some loss to BAE, multi-slugs are better at defeating light and/or area targets and the finned projectiles have greatly enhanced accuracy. The use of this warhead type is mainly restricted to lightly armoured areas of main battle tanks (MBT), the top, belly and rear armoured areas for example. Its use in the attack of other less heavily protected armoured fighting vehicles (AFV) and in the breaching of material targets (buildings, bunkers, bridge supports, etc), it is well suited. The newer rod projectiles may be effective against the more heavily armoured areas of MBTs. Weapons using the EFP principle have already been used in combat; the "smart" submunitions in the CBU-97 cluster bomb used by the US Air Force and Navy in the 2003 Iraq war employed this principle, and the US Army is reportedly experimenting with precision-guided artillery shells under Project SADARM (Seek And Destroy ARMor). Developed and produced by Textron Defense Systems the CBU-97 Sensor Fuzed Weapon is a United States Air Force 1000-pound-class (450 kg non-guided (freefall Cluster bomb Cluster munitions or cluster bombs are air-dropped or ground-launched munitions that eject a number of smaller submunitions a cluster of bomblets A shell is a payload-carrying Projectile, which as opposed to shot, contains an explosive or other filling though modern usage includes large solid projectiles Project Sense and Destroy ARMor, or SADARM, is a US 'smart' Submunition capable of searching for and destroying Tanks within a given target area There are also various other projectile (BONUS, DM 642) and rocket submunitions (Motiv-3M, DM 642) and mines (MIFF, TMRP-6) that use EFP principle.
Tandem warhead
Some modern anti-tank rockets (RPG-27, RPG-29) and missiles (TOW 2B, ERYX) use a tandem warhead shaped charge, consisting of two separate shaped charges, one in front of the other, typically with some distance between them. The RPG-27 is a man-portable disposable anti-tank rocket launcher developed by the Soviet Union from the RPG-26. The RPG-29 Vampir is a Russian hand held Anti-tank Grenade launcher. The BGM-71 TOW is a US Anti-tank guided missile. TOW Tube-launched Optically-tracked Wire-to-command-Link guided Missile Set ERYX is a short-range portable SACLOS -based wire-guided Anti-tank guided missile (ATGM produced by European company MBDA. A tandem-charge weapon is an Explosive device or Projectile that has two or more stages of detonation Usually, the front charge is somewhat smaller than the rear one, as it is intended primarily to disrupt explosive reactive armor. Reactive armour is a type of Vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected
References
- Fundamentals of Shaped Charges, W. P. Walters, J. A. Zukas, John Wiley & Sons Inc. , June 1989, ISBN 0-471-62172-2.
- Tactical Missile Warheads, Joseph Carleone (ed. ), Progress in Astronautics and Aeronautics Series (V-155), Published by AIAA, 1993, ISBN 1-56347-067-5.
- ^ Shaped Charge. globalsecurity. org.
- ^ Panzerkampfwagen IV Ausf.G, H and J 1942-45 By Hilary L. Doyle, Thomas L. Jentz, Tom Jentz, Tony Bryan. Google Books.
See also
External links
- Elements of Fission Weapon Design
- Blaster Exchange Explosives Industry Portal
- Shaped bombs magnify Iraq attacks
- Shaped Charges Pierce the Toughest Targets
- The development of the first Hollow charges by the Germans in WWII
- Use of shaped charges and protection against them in WWII
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic