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JANE'S DEFENCE WEEKLY - JUNE 22, 2005

RUAG exploits new warhead technology

PAOLO VALPOLINI
JDW Correspondent Milan

RUAG's Defence Warhead Division demonstrated numerous new products in late May based on recently developed technology.
The new technology, which involves hollow-charge warheads based on a variable thickness molybdenum liner, has allowed RUAG to produce warheads that maintain optimal performance even if their desired stand-off distance (the distance between the target armour and the warhead detonation point) is not precisely respected, with the perforation remaining similar to results obtained where the stand-off distances are from three to five times the length of the charge diameter. Using this technology, RUAG charges can fully exploit almost all of the liner mass and put it where it is most needed at a speed of 11.5-12 km/s.
Two products employing the new technology were shown in action, the first being a 146 mm diameter charge containing 2.9 kg of explosive that perforated about 1,500 mm of ballistic steel consisting of a series of 80 mm thick steel plates. The molybdenum jet generated a hole with a diameter of 18-20 mm through the whole target. Such a warhead is proposed for the upgrade of anti-tank missiles of former generations as well as for new weapon systems in this category.
Another test was conducted using an RPG-7 rocket-propelled grenade launcher equipped with a RUAG tandem warhead designed to ensure good penetration even against armoured vehicles equipped with explosive reactive armour. This warhead achieves a penetration in excess of 900 mm against rolled homogenous armour and has an increased range up to 250-300 m. Tested against a former Swiss Army Pz68 main battle tank, it penetrated the gun breech block and remained inside the tank; subsequent tests produced both an entry and exit hole.
A warhead for the M72 LAW based on insensitive explosive and with a penetration in excess of 500 mm has also been developed: the current version is based on a single charge while a tandem warhead will be available soon.
RUAG also demonstrated the 81mm Mortar Anti-Personnel Anti-Materiel (MAPAM) mortar bomb, which uses the same layout of ball fragments used in the 60 mm MAPAM, although JDW understands that some of the 4,800 balls in the round (compared to the 2,400 4.2 mm diameter balls of the 60 mm bomb) have a greater diameter and are located in the rear part of the bomb body. A 120 mm version, which will include four sub-elements equipped with proximity fuses, is under development; the four bodies will spread the balls mostly in the frontal arc (similarly to RUAG's CRAD grenades), the weapon being of the airburst type (while the 60 mm and 81 mm work with point detonation fuses). The diameter of the balls is believed to be up to double that of the original balls in order to provide better anti-materiel effects. The four sub-elements will be deployed from the bomb body and will then remain suspended under asymmetrical parachutes, ensuring their spread over the target area. A prototype of the 120 mm MAPAM should be ready by year-end.
RUAG also showed what it calls the Starblast warhead. This utilises a new thermobaric technology to consistently augment the effect of an explosion, considerably increasing the time during which overpressure is created by the blast. Whereas conventional fuel air explosive bombs employ two separate ignitions - one to spread the explosive and the second to detonate it - and have proved unreliable, especially in strong winds, the RUAG technology allows the explosive to be spread over the target area and detonated by a single ignition system. The Starblast warhead uses a semi-solid explosive substance, the effects of which are more than double that of an equivalent TNT charge.
This technology can be used to develop numerous different weapon systems, from conventional bombs to urban warfare systems (such as the RUAG Modular Explosive Penetrator round used to penetrate buildings before exploding) or even in a 40 mm grenade. Tests have so far been conducted with charges up to 4.5 kg.


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INTERNATIONAL DEFENCE REVIEW - AUGUST, 2005

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RUAG unveils two shaped-charge warheads

Neil Gibson

Two new shaped-charge warheads have been unveiled by the Swiss RUAG company: a molybdenum (Mo) lined 146 mm diameter (152 mm case) and the second a new and improved tandem copper-lined warhead for the RPG-7 weapon system.

The ability to defeat heavily armoured AFVs relies on two main technologies: shaped charges - also know as the Monroe or Neumann effect - and that of pure Kinetic Energy (KE) attack. The use of pure KE attack is not used in most guided and shoulder-launched anti-armour weapons at present, mainly due to the necessary velocity, inherent high complexity and potential lethality to an unprotected firer. Shaped charges, on the other hand, can be thrown - even hand-placed - and can still defeat heavy armour. In this case the energy required to penetrate the target comes from the explosive contained within the munition, not the munition's velocity.

This is accomplished by using the explosive to collapse a hollow lined cavity (normally metallic) into itself, forming a hypersonic jet of material which pushes its way through the target.

RUAG's compact 146 mm PBXW-11 filled warhead consists of an aluminium alloy case with a Mo elliptical shaped liner. Its PBXW-11 filling is a relatively insensitive pressed plastic bonded explosive (PBX) containing HMX. The warhead has a central detonator well, the detonation wave being directed to the periphery of the charge via RUAG's waveshaper material PEGAB (PolyEster with GlAssBubbles). In a series of radiographic tests, the jet tip velocity (Vtip) reached around 11.5 km/s, achieved through a combination of the liner shape, its thickness, initiation mode and material. The Mo liner, although difficult to fabricate, more costly and having a lower dynamic ductility, has a higher bulk speed of sound which allows for a higher liner collapse velocity and hence jet velocity. Penetration is also improved as Mo possesses a higher density in comparison to copper, 10,280 to 8,920 kg/m3. For the demonstrations at RUAG's range in May (2005), the warhead was placed at 5.5 cone-diameters (CD) from a target array consisting of 22, 80 mm-thick RHA plates. The detonation of the charge resulted in the perforation of 17 plates and the lodging of the jet remnants some distance into number 18, an approximate penetration of some 10 cone diameters (1.45 m), with the average hole diameter through the plates by approximately 20 mm.

The new tandem RPG-7 warhead, unlike the previous firing, was a full system test. The launcher was at a distance of by approximately 75 m to the target. The target was a Swiss Pz68 tank, aligned so the round impacted its side. The warhead consists of two shaped charges: a small precursor charge (approximately 30 mm diameter); and the main charge (100-112 mm). Both were copper-lined and with either a PBXW-11 or LX-14 filling. No details were given of the liner profile, initiation mode, or whether RUAG's FORCE-HAMMER shock decoupling technology was used. In static tests the warhead is capable of penetrating >900 mm of RHA after second generation ERA. The dynamic firing resulted in the round striking the centre of the tank, approximately 20 mm below the turret, the jet passed along the top of the hull armour, ripping it open, then passed through the turret ring and embedded itself in the main gun's breech block. Total penetration depth was not disclosed, but this hit would have certainly resulted in an operational kill, as the main gun was out of action.

A high-performance warhead for the M72 LAW from Nammo was not demonstrated during the May trials, although some details were disclosed. The warhead is point-initiated and has a wide-angled elliptical (tulip) shaped liner of copper. It is filled with an insensitive explosive filling. The complete round was reported to weigh no more than the original. Its penetration was given as greater than 500 mm of RHA before any ERA, well above the above the 355 mm of the M72A4 model.



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INTERNATIONAL DEFENCE REVIEW - DECEMBER, 2004

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Warheads widen infantry weapon effects for urban warfare

Neil Gibson and Rupert Pengelley

Post-Cold War retrenchment may have cut down the number of active companies but the range of capabilities developed by infantry weapon warhead designers is expanding to match the flexibility demands of modern forces. Neil Gibson and Rupert Pengelley report

Warheads for infantry-portable weapons systems, like the protection systems to counter them, are a constantly evolving field of research and development. The types of targets these weapons are now required to defeat are much more numerous and diverse than in the past, when the primary concerns were countering armoured fighting vehicles (AFVs) or unprotected troops at short to medium ranges (50-500 m). One of the principal drivers for this change has been an increased focus on the requirements of military operations in urban terrain (MOUT). The list below indicates the range of targets to be overcome.

The classical target set includes:

metallic single or multilayered AFV targets, protected by armour of rolled homogenous steel (RHA), high-hardness steel, aluminium or titanium;

composite armours that use materials such as ceramics, metals and fibre-reinforced plastics;

AFV targets that are additionally protected by single or multilayer explosive reactive armour (ERA), the platform being already protected by one or many of the above;

infantry in the open or in defilade; and

soft-skinned and lightly armoured vehicles.

The additional, wider set, brought on by MOUT operations and new armours, includes:

earth and timber bunkers;

reinforced concrete bunkers;

buildings made from materials such as wood, brick, mortar and cinderblock;

the rapid creation of access points to buildings made from these materials;

cave complex clearing (initial entrance cave only);

AFV targets protected by either active or passive defensive aid suites (DAS); and

electric armour, using either electromagnetic-fired plates or the electrodynamic disrupting effect of a high-current pulse on the shaped-charge jet.

To overcome these many and diverse targets, a variety of warhead types have been developed or are under development, among them blast/fragmentation; enhanced blast (thermobarics); shaped, compact shaped, multimode shaped, long-standoff shaped and combined effects charges; explosively formed projectile (EFP) and multimode EFPs; follow-through weapons (shaped charge/EFP with follow-through blast/ fragmentation bomb); high-explosive squash head (HESH), also called high-explosive plastic (HEP); modular explosive penetrator (MEP); and variable-geometry warheads. An explanatory note on each is given on pages 41-45. (See also the warhead/target matrix on page 44, which highlights the pros and cons of each warhead against the target set.)

The challenge facing the weapon designers is to meet the user's need to cover as many target types as possible with one system.

TDW, a German subsidiary of EADS, is one of the many developers working on a multipurpose warhead design. Dr Helmut Muthig, president and chief executive officer at TDW, describes this as "a triple-effect single warhead that combines the effects of a shaped charge, a penetrator charge and a blast/frag[mentation] charge to defeat heavy armour as well as to deliver a lethal effect (with enhanced blast effect) behind any obstacles such as light armour, brick, walls, sandbags. It should be added that also an intelligent fuzing contributes to that effectiveness." The putative target set for the TDW design also includes radars, trucks, missile and helicopters as well as corvettes, fast patrol boats and fast inshore attack craft, the latter having particular relevance for marine units operating in a force-protection or anti-invasion role.

The TDW design is geared to calibres of around 150 mm and is suitable for new-build applications or retrofitting to guided weapons in the Milan, HOT, or TRIGAT class. The design has not yet been applied to a running missile programme, but Dr Muthig tells IDR that discussions on upgrading these weapons are in progress. It is scalable for use with other forms of infantry-operated weapon but Dr Muthig thinks it is unlikely that all three effects could be combined in a warhead with a calibre of less than 100 mm.

"Each (individual) technology module -- and even some combinations of them -- have already reached a high Technology Readiness Level in so far as they are used in serial production," Dr Muthig tells IDR. "It is the new (and) unique combination of the complex effects and their interaction that has (yet) to be demonstrated in [its] completeness." TDW is relying principally on internal funding to complete the warhead, including its proper fuzing. A demonstration programme to verify its performance is being planned.

Germany's Dynamit Nobel Defence is best known for its Panzerfaust 3 (Pzf 3) anti-tank rocket launcher that fires 110 mm multipurpose shaped-charge warheads. The baseline version has a 1.5 kg HE filling and can penetrate more than 800 mm RHA. It can be switched from anti-armour to anti-masonry/anti-bunker mode by retracting the probe on the front of the warhead. The Pzf 3-T (Tandem) model differs in having an additional shaped-charge precursor installed in the probe that can perforate ERA without detonating it. If the probe is not extended, the precursor serves to add 100 g of explosive to the main charge, increasing the weapon's effectiveness against secondary targets. The latest version is the Pzf 3-IT (Improved Tandem), whose extended probe gives a longer standoff and enables the warhead to penetrate 900 mm RHA behind ERA. Bunkerfaust, the anti-bunker version of Pzf 3, fires a Diehl-designed warhead combining a large precursor and a follow-through fragmentation grenade that detonates behind the wall.

In co-operation with Rafael, Dynamit Nobel now also offers the Wall Breacher ring-type shaped-charge warhead, which is designed to create a man-sized hole in a wall without causing excessive structural damage. This has been applied not only to Pzf 3 but also to the German company's RGW 60 (60 mm) and Pzf 90 (90 mm) disposable launchers. Dynamit Nobel also continues to supply HESH-type warheads, which in 60 mm calibre incorporate 500 g of explosive and are capable of punching a wider than 400 mm hole in masonry. The baseline (HEAT) warhead of the RGW 60 penetrates deeper than 300 mm RHA, while the HEAT-MP (multipurpose) version penetrates 100 mm RHA and generates 270 pre-formed fragments.

Out of sight

The RGW 60 provides the basis of the Corner Shot Panzerfaust (CSP) system that Dynamit Nobel launched at Eurosatory in 2004 in association with Corner Shot of Israel. The CSP has a portable collapsible monopod to which is attached a remote-view sighting system. This allows the firer to aim the RGW 60 from behind cover and can also be used for surveillance.

The Pzf 90 design provides the basis for Dynamit Nobel's involvement in new and future overseas programmes such as the Singaporean MATADOR (Man-portable Anti-Tank, Anti-DOoR) and US FOTS (Follow-On To SMAW [Shoulder-launched Multipurpose Assault Weapon] ). MATADOR is a 90 mm-calibre 8.9 kg man-portable disposable anti-armour weapon system which has been under development since 1999 in conjunction with the Singapore Armed Forces (SAF) and the country's Defence Science and Technology Agency (DSTA).

Intended to meet the needs of an increasingly urbanised battlefield as a replacement for the Armbrust short-range anti-armour weapon that has been in SAF service since the 1980s, MATADOR was formally unveiled in September this year. It is designed for firing from within confined spaces (more than 15 m3) and is described by the SAF as the first of its kind to have both anti-armour and anti-brick wall capabilities. Its operating temperature range is -40ºC to +63ºC. The 2.6 kg dual-capability warhead, when set to delay/squash-head mode, creates an opening wider than 450 mm in a double brick wall, while in the impact/HEAT mode its armour-penetration capability is billed by the SAF as sufficient to defeat light tanks and APCs. Compared with the Armbrust, MATADOR's increased muzzle velocity (250 m/s) reduces susceptibility to wind, the time of flight to 300 m being 1.2 seconds. Its precision optical sight gives an effective range of 500 m, a Picatinny rail being fitted for mounting night-vision devices.

The more recent shoulder-launched weapons from Dynamit Nobel Defence have muzzle velocities that are at least 100 m/s greater than their predecessors; the RGW 60 with 280 m/s, for example. Among other benefits, this gives scope for saboted explosive-filled kinetic energy (KE) penetrators to be fired against masonry and concrete structures directly from the recoilless launcher, in contrast to RUAG's MEP warhead design (see below), in which a KE penetrator of more restricted size is included inside a standard (oversized) warhead casing. An anti-structure KE penetrator round and a multipurpose HE projectile are among the warhead types proposed for Pzf 90/FOTS.

Israel Military Industries (IMI) has introduced an urban warfare adaptation of its Shipon anti-armour rocket, designated Shipon-UT. This meets the primary requirements of urban warfare, defined by the company as the ability to be fired from within an enclosed space to defeat urban defence positions, breach walls and incapacitate enemy personnel.

In live demonstrations, the Shipon-UT's multipurpose warhead has shown that it can defeat a range of target types, including earth and timber bunkers; triple brick walls; double-reinforced concrete walls; and 76 mm RHA plates. The same warhead may be operated in airburst mode, enabling it to be used to engage troops in the open. Two other warheads are available for Shipon-UT, including a breaching warhead designed to create an opening in a wall large enough for a soldier to pass through; and a tandem anti-armour warhead capable of penetrating more than 800 mm of RHA.

Low noise

In firing mode the Shipon-UT is 1 m long with an external diameter of 106 mm and a warhead diameter of 100 mm. The rocket has a fire-control system in its reusable anti-tank configuration that gives it an effective 600 m range against moving targets, while the multipurpose variant is a one-shot weapon with a simple optical 300 m-range sight. On-the-shoulder weights are 11.5 kg and 9 kg respectively. The Shipon-UT's propulsion system generates low noise and toxicity levels inside the enclosure as well as a very low signature outside the firing window. A gas-tight modified Davis Gun launch method is employed to ensure that the discarded tube contains the sealed gases and that no propellant burns outside the canister. The propulsion unit and warhead both incorporate insensitive munition (IM) materials.

One of IMI's principal rivals is a fellow Israeli company, Rafael Armament Development Authority, which developed the Simon door-breaching rifle-grenade in 1989-90. Compatible with M16 or M4 rifles, Simon has been type-classified in the US, where it is produced under licence by General Dynamics Armament and Technical Products (GDATP) as the M100 Grenade, Rifle Entry Munition (GREM). It has also now been acquired by UK forces. The Simon grenade is fitted with a probe to give the requisite standoff distance to its small explosive charge, creating a pressure wave with sufficient force to tear a door from its hinges without generating an internal pressure or fragments that might injure hostages on the other side of the door.

Simon is complemented in Rafael's product range by the Wallbuster and Bunkerbuster (the BDM 60-CS) one-shot disposable 9 kg shoulder-launched rocket systems, suitable for firing from confined spaces. The Wallbuster and Bunkerbuster incorporate a common sighting system and 60 mm launch tube with which differing types of oversize warhead are integrated, thereby simplifying training.

The Wallbuster munition, developed for urban warfare applications, has an effective range of 15-50 m and includes a 2.5 kg explosive filling triggered by a piezo-mechanical impact fuze. Its warhead exploits the same (explosively formed ring) design approach as Simon to cut a man-sized (89-96 cm) hole in double-layered brick walls or 20 cm-thick double-reinforced concrete walls. The Bunkerbuster, which is optimised for use against concrete bunkers, earth and timber bunkers or against light armoured vehicles, features a 60 mm HESH-type warhead. Its fuze has two modes -- a long delay applied to soft target material or a short one if it encounters steel. As offered by licensee GDATP, the BDM 60 has a maximum range of 250 m, weighs 7.12 kg and is 950 mm in length.

Neither munition is truly multipurpose but designers at Rafael assert that in principle each is sufficiently light for both types to be carried within a squad. Even so, in response to market demands, Rafael has recently introduced its MPM 90-CS (Multi-Purpose Munition [Confined Spaces]), an enlarged one-shot system specifically intended to address the full range of targets out to a maximum effective range of 500 m. It has a launcher diameter of 90 mm, a length of less than 1 m and, according to Rafael, a weight of "9-13 kg depending on the application".

Details of the warhead types on offer with MPM 90-CS are sparse but these are described as including variants effective "against targets such as light armoured vehicles, bunkers, and tanks". Rafael says that one of their characteristics includes "enhanced blast effect".

A version of the MPM 90-CS warhead (integrated with a Dynamit Nobel launcher) forms part of the GDATP submission for the US Marine Corps' (USMC's) FOTS competition, in which it has been pitted against Lockheed Martin teamed with IMI. According to Rafael some 45 rounds were successfully fired as part of the recently completed FOTS system integration phase but the programme remains unfunded.

Despite the downturn in its domestic business, Swiss company RUAG has been successful in securing an increased share of world warhead business from non-traditional clients. Chief among these are the British and Swedish armies for the Saab Bofors Dynamics MBT-LAW (light anti-tank weapon) rocket programme; the Swedish Army for the Bill 2 anti-tank missile programme; and the US Army for its Precision Guided Mortar Munition (PGMM) programme, although this contract award is the subject of a protest from the losing bidders. All of these incorporate RUAG warhead technology, whose selection against international competition provides practical endorsement of the company's proprietary isostatic pressing and shrink-fit assembly techniques, which RUAG claims have enabled it to take the armour-penetration capabilities, consistency and producibility of large and small-calibre shaped charges to new levels.

For shaped charges the advantages posited for isostatic pressing include an increase in the density of the explosive filling, leading to a higher detonation velocity; and greater uniformity of the filling, leading to a more uniform propagation of the detonation wave and an absence of cracks that might disturb its propagation. In all, these give rise to "excellent jet formation and superior penetration", say RUAG. The use of shrink-fit methods in assembly of the explosive components also eliminates the risk of air gaps being formed within warheads.

Another contributor to the reproducibility and effectiveness of RUAG warhead designs is the company's proprietary virtual development tool, based on an object-oriented system analytical toolset and mathematical modelling. This process is used to optimise existing warheads and develop new materials and technologies for achieving improved behind-wall or behind-armour effects.

For multiple warheads incorporating charges with diameters of 100 mm or less, RUAG has also introduced its proprietary Roundhammer decoupler, which serves to reduce any disruption to the main charge caused by the shock, blast and fragments generated by precursor charges.

Beneficiaries of these techniques include the TOP100 warhead supplied for the Instalaza Alcotan-100 rocket launcher system. The TOP100 has a 100 mm main charge and 65 mm non-initiating precursor charge, its total mass being 2.9 kg and its explosive mass 850 g. This version has a nominal 8.5 charge diameter (CD) penetration capability, exhibiting a behind-ERA penetration capability in excess of 800 mm.

Roundhammer is also used in the tandem warhead that RUAG has supplied for an improved version of Giat's APILAS 112 mm shoulder-fired rocket, which was adopted by the Finnish Army in 2002; and in the new tandem warhead fitted to the Malyutka 2000 (improved AT-3 Sagger) developed in conjunction with RUAG's Bulgarian partner VMZ. The Malyutka 2000 has a 2.8 kg warhead incorporating a compact main charge with a length-to-diameter ratio of 1 and a copper liner produced using RUAG's flow-turning process. Its diameter is 120 mm and its nominal penetration capability exceeds 10 CD. The Malyutka 2000's warhead is credited with a main-charge penetration capability of "at least 850 mm" of RHA behind second-generation ERA arrays.

Another VMZ anti-armour weapon to have been improved with RUAG's help is its Factoria 9M111-TOP100 version of the Russian 9M111 (AT-4 Spigot) missile. The calibre of the missile is 120 mm, and that of its 2.9 kg warhead around 100 mm, again yielding an RHA penetration of around 850 mm behind a second-generation ERA array, which is first pierced by the TOP100's non-initiating precursor.

Penetration growth

Under its long-standing association with Swedish company Saab Bofors Dynamics, RUAG has also progressively raised the RHA penetration of the HEAT warhead used in the baseline 84 mm AT4 CS rocket launcher from up to 420 mm to up to 500 mm (AT4 CS HP). Most recently, in the AT4 CS IM version, the Swiss company has raised RHA penetration to more than 600 mm. The same technology has helped raise the penetration capability of the Nammo-produced M72 EC version of the US 66 mm LAW to better than 500 mm, and that of the latest VMZ-produced version of the PG-7 rocket for the ubiquitous Russian RPG-7 rocket launcher to as much as 1 m RHA (behind third-generation ERA).

RUAG's warhead developments also include product-improved versions of the MEP (see IDR 4/2003, p4) originated by Denel in South Africa. The MEP Mk 1 slow-flying (150 m/s) 40 mm sub-calibre penetrator is designed to pierce urban structures, bunkers (including 250 mm of double-reinforced concrete, a 375 mm-thick triple brick wall or an earth-and-timber bunker protected by a 1.2 m thickness of sandbags), or light armour (12.5 mm RHA or 50 mm aluminium) before exploding to generate a behind-barrier fragmentation and blast effect. It can also be fuzed to explode on initial impact against a wall, creating an entry-hole with a diameter as big as 762 mm.

In its MK2 configuration the MEP has been successfully integrated within full-calibre warheads associated with a number of different rocket launchers, including VMZ's PG-7MEP grenade for the RPG-7; Saab Bofors Dynamics' AT4 CS; Dynamit Nobel's Panzerfaust 3; and the Russian RPG-22. The use of these launchers imposes diameter constraints that RUAG aims to circumvent with its developmental MEP Mk2. With a bigger internal volume and payload, through exploitation of what RUAG describes as high dynamical rheological penetration technology, the MEP Mk2's explosive filling incorporates a combination of PBXN-110 and non-ideal explosive to enhance the penetrator's blast characteristics.

Exploiting its latest Starblast thermobaric filling, which has three times the energy output of the basic Russian single-cycle propellant-based system with a bursting charge, sources say that RUAG is working with Insys on a novel anti-structures/anti-tank warhead design. Intended for fitting to weapons in the category of the US 83 mm SMAW (Shoulder-launched Multi-purpose Assault Weapon), it is expected to utilise a precursor developed under the Insys PANDORA (Penetration And Non-Detonation Of Reactive Armour) programme (see p44).

The Naval Surface Warfare Center (NSWC), Indian Head, is a major exponent of enhanced blast techniques in the US. NSWC works in the infantry weapons field, principally on behalf of the USMC. One of the centre's industrial associates is Talley Defense Systems, which, using independent research and development funding, completed in 1999 its first demonstration of an 84 mm thermobaric warhead suitable for use with the Carl Gustav M3 launcher. Talley was sponsored in 2001 by the NSWC to demonstrate SMAW-HIT, a high-impulse thermal warhead for firing by the USMC's SMAW against cave and bunker targets. The company went on the following year to complete development and qualification of SMAW NE (novel explosive), a dual-purpose thermobaric warhead for the same weapon. The US Army Armament Research, Development and Engineering Center (ARDEC) subsequently sponsored Talley to develop and demonstrate a unitary thermobaric warhead for the SMAW-D (disposable) variant. In co-operation with the USMC, Talley has also developed a confined space propulsion system for SMAW, designated SMAW LEAP (Low-signature Encased Assault Projectile), which reduces its backblast and overpressure without loss of range or velocity.

Another established shoulder-launched weapon to have received a thermobaric revamp is the 66 mm M72 LAW. Talley was funded by NSWC to devise a new variant designated M72 NE, whose unitary warhead is characterised by the company as being filled with a "high-performance enhanced blast explosive, initiated by a self-discriminating fuze" that produces a delayed reaction on light walls, or a detonation on impact when striking reinforced targets. In parallel the company has been working on the M72 HH version, which uses solid and semi-solid fills to create long-duration heat effects able to "migrate round corners and into multiple rooms." According to Talley it has "demonstrated temperatures of up to 150ºC for more than six seconds."

Warhead types: a study in profiles

BLAST/FRAGMENTATION

Much research has also been undertaken since the Second World War on controlling and enhancing the fragmentation effects of warheads. The two main techniques to regulate the fragmentation of a warhead, instead of relying on the more haphazard mode of natural fragmentation, is the controlled fragmentation method (such as internal scoring or zone embrittlement) and the use of pre-formed fragments (such as cubes, spheroids or rods) within the casing body. Both control methods increase the efficiency of a given warhead size but with increased complexity and cost.

The fragmentation effect of most warhead types can be improved by one of these methods, giving the weapon a multipurpose functionality. The main costs incurred are an increase in size and weight of the warhead, if the primary function is not to be sacrificed. If these increases cannot be accommodated, then there is a loss in the performance of the primary function.

Through the use of advanced fuzes, made feasible by ever-shrinking electronic devices and micro-electromechanical systems technologies, the fragmentation warhead's efficiency can be improved. The warhead can be made to function at specific times and distances from the launcher. The fuze makes use of highly accurate timing and turn counting in addition to a possible proximity function. Although timing and proximity fuzes are not new to missile and artillery weapons, the ability to fit them into a warhead as small as a 20 mm projectile represents a step forward. (Examples of this include the Alliant Techsystems [ATK] 25 mm XM25; ST Kinetics' S418 40 mm Air-Bursting Munition; General Dynamics' 25 mm XM307; and the Nammo Raufoss 40 mm PPHE-T/SD airburst munition.)

Other advanced research seems to be directed towards selectable initiation points and deformable warheads. Each method allows the fragment pattern and velocity to be focused in a selected direction. The former can involve initiation at the top, bottom or along the periphery of the warhead, focusing the fragments towards the target. The latter uses a skin of explosive, external to the fragments but inside the protective casing, which, when initiated, deforms the fragments. At the appropriate moment the warhead is initiated from the opposite side. Although both of these methods are expensive, complicated and are only likely to be used for anti-aircraft or missile warheads, they are included here for reference.

A substantial blast wave is created in addition to the fragments produced on detonation. A blast in the open will neutralise softer targets at short range but for these targets the fragments are far more lethal. For buildings, the confined blast of a fragmentation warhead within the structure will often cause extreme damage (conditional on the size of the warhead). The blast effects from fragmentation warheads can be improved, normally obtained by the small addition of aluminium powder to the explosive fill. This improves blast and thermal effects without excessive degradation of the fragment velocities. (The addition of large amounts of fuels such as aluminium results in so-called 'non-ideal' explosives - see below.)

ENHANCED BLAST AND THERMOBARICS

The detonation of high explosive (HE) can be viewed in three stages. The first, an anaerobic stage, is measured in microseconds and breaks down the explosive by a shock wave. The subsequent exothermic molecular reactions go on to propagate the detonation wave. The second stage, measured in hundredths of microseconds, is also anaerobic. This involves reactions between any products that were too large to be involved in the main detonation event. The third stage is aerobic and lasts milliseconds. In this stage more, previously unreacted, fuel particles react with the surrounding air.

Stage One defines the HE's high-pressure shock effects (such as propelling a metal liner or fragments); Stage Two prolongs the high-pressure blast pulse, giving a useful heaving effect needed in building or bunker defeat; and Stage Three produces a long-duration, lower-pressure pulse that can also have a high thermal output, both of which are useful for materiel and personnel defeat.

Stages Two and Three are enhanced in thermobarics. This is accomplished by the addition of various fuels and additional oxygen-carrying chemicals to the explosive. The fuel is normally finely powdered aluminium, but boron, silicon, titanium, magnesium, zirconium, carbon and hydrocarbons can also be used. A typical oxygen-carrying chemical would be ammonium perchlorate. By carefully selecting the HE, fuel and oxidiser, the multiple-target defeat effects of blast, fragmentation and thermal pulse can be brought into effect.

Blast enhancement is mainly due to two reasons. The first is the fact of the wide dispersion of the fuel before combustion, making the initial combustion zone very large in comparison with a standard high explosive (metres compared with millimetres). The second is that although the peak pressure produced is lower, the duration is far longer. This is effective as the ability of buildings and people to survive a given pulse pressure level decreases with increasing pulse duration. The thermal effects of such warheads also dwarf those of classical HE, the temperature of the fireball, the heat flux produced and its duration all being several times larger (some an order of magnitude greater).

The first thermobaric weapons, fielded in 1984, were developed by the Russians, the first acknowledged weapon being KBP's RPO-A, or "Shmel". Later, warheads were also developed for the RPG-7 launcher (TBG-7 and Bulgarian GTB-7) and the single shot RShG-1. The original Russian thermobaric fills took the form of a semi-liquid (paste), the composition being RDX, aluminium and isopropyl nitrate. Most modern thermobarics are solids, however.

In general, Western weapon designers were slow to pick up on thermobarics but RUAG, Talley Defense Systems and many others are now actively involved. Talley has tested a modified M72 LAW (light anti-armour weapon) with a thermobaric fill, designated M72 LAWNE (novel explosive). The NE fill selected for further testing in the M72 LAW would seem to be PBXIH-135, which is a mix of HMX, aluminium and hydroxyl terminated polybutadiene (binder). Swiss munitions company RUAG has now moved on to what can be described as third-generation thermobarics in the form of its Starblast technology. According to RUAG this is a hybrid of non-ideal explosive and a single-cycle system, scalable for munitions ranging in type from the company's Modular Explosive Penetrator (MEP) Mk2 to mortar rounds.

SHAPED CHARGES

The continuing battle between the warhead and armour designers and the requirements of MOUT have ensured that research in shaped charges remains active. In addition to the constant drive to improve penetration, some of the research is directed towards reducing the charge length (more compact weapons); giving the charge a multi-target defeat ability (reducing the burden of carrying multiple weapons); using bi-material liners (explosive-reactive armour defeat and improved behind-armour effects); and creating the ability to attack armour at extreme standoff (the defeat of defensive aid suites - [DAS]).

The ability of any jet to penetrate a given armour type is dependent on three main parameters: jet velocity, jet material and jet length. Jet velocity is dependent on the explosive used; the explosive's initiation mode; the cavity's angle/shape; the liner material; and the liner's thickness. The jet material's density and dynamic characteristics affect the penetration process. The jet length is a product of jet velocity and jet material. In view of all the main variables, the job of the warhead designer in improving penetration is clearly a complex one. However, this task and the design of new warhead designs have been made easier through the use of advance hydrocodes.

There are many types of hydrocode, a few examples being the Sandia National Laboratories-developed CTH (for US government-approved agencies and Insys Ltd); Century Dynamics AUTODYN 2D&3D (for Diehl Munitionssysteme and many others); and cAst2D (for QinetiQ). Once a task has been submitted, an extensive series of simulations can be run on the various virtual warheads and their targets. Only once these model tests are completed - and the final selected warhead designs agreed - are the warheads created and tested for real. Using these codes means that many of the initial expensive developmental field trials need not be performed, so decreasing both costs and design time.

The explosives used in shaped charges need to have a high detonation pressure and a high rate of detonation, both of which in combination drive the liner together and cause the subsequent penetrating jet to form.

One new explosive fill proposed for this purpose is LX-19. This is a PBX containing the explosive CL-20 (Hexanitrohexaazaisowurtzitane) and the binder Estane. The ratios of CL-20 and Estane are 95.8 per cent and 4.2 per cent respectively, the same as for HMX and Estane in the explosive LX-14. LX-19 gives deeper penetration through improvements in jet length and jet velocity but it is slightly more sensitive than LX-14.

The performance of shaped charges can also be significantly improved by manipulating the detonation wave. This can be achieved either through the inclusion of barrier materials within the explosive or by some form of advanced initiation. Although sometimes incorrectly called wave-shaping, a barrier material does not shape the wave but directs it to the periphery of the charge. A toroidal detonation wave then emerges from the periphery and two major effects occur upon arrival at the liner. The first is that the wave travels across the liner at a higher speed; the second is that the liner is accelerated inwards at greater velocity. This gives a higher velocity and a larger velocity gradient to the jet, which, through greater stretching, results in a longer jet. Advanced initiation implies a multipoint initiation system. This can be a continuous peripheral initiator, a ring of initiators or a matrix of initiators. These can be at the top, bottom or some other point along the body of the warhead.

The peripheral and ring methods improve the jet in the same manner as the barrier method mentioned above. The matrix method, which may also include individual initiator timing control, can be used to control the morphology and velocity of the jet to a wide degree. Hence the barrier method is a simple way to improve performance but does not afford any target flexibility. Multimode initiation, on the other hand, is very flexible but also highly complex.

Advanced initiation is one way in which multimode warheads can be created. Introducing a movable 'liner spoiler' into the equation is another method. This approach has been used in an experimental version of Diehl Munitionssys-teme's Bunkerfaust warhead. The spoiler disturbs the jet formation when in place, dispersing the jet or turning the shaped charge into a crude explosively formed projectile (EFP). By connecting the jet spoiler to the nose probe extension mechanism, the weapon is able to attack heavy armour in the jet mode (probe extended) or in buildings and light armour when in the spoiler mode (probe retracted). In the second mode, the follow-through bomb carries on through the hole to explode within the target.

Compact charges have the same performance as standard charges but at greatly reduced length. This compactness is obtained by new liner profiles and the use of advanced barrier or initiation modes. Their reduction in length and weight enhances the portability and manoeuvrability of the complete weapon system.

Combined or multi-effect warheads are generally a melding of the three main classes of warhead (blast, fragmentation and shaped charge) to produce a 'jack of all trades' warhead. Although not the best at any individual class, they do allow one weapon to be used to attack most battlefield targets. In a representative experimental design by ARDEC the case is made robust enough to allow light target penetration before detonation while maintaining good fragmentation characteristics, typically through internal scoring. Between the rear-mounted centric detonator and the shaped charge is an inert barrier, giving the shaped-charge portion penetration performance on a par with compact charges. The fuzing system would have to allow for target sensing in the same manner as the Talley Defense Systems HEDP (high-explosive dual-purpose) round. It would also be surmised that the explosive fill will also be aluminised to improved blast effects.

Information on a RUAG multifunction/multipurpose charge shows it to be a peripherally initiated (barrier method) compact shaped charge, incorporating performed fragments and a bi-material liner for improved behind-armour effects.

The emergence of DAS such as the Russian Kazt (Arena) and Drozd-2 (Thrush) systems has implications for the attack of armour. It has been found that shaped-charge warheads are extremely sensitive to foreign bodies within the explosive or liner area. If a fragment from an active DAS systems-kill vehicle enters either of these areas, the warhead's ability to penetrate armour is drastically reduced, some estimates giving a 70-90 per cent reduction in penetration depth from one 5 mm sphere fragment strike. It can be seen from this that either the warhead or missile will need to be armoured (although this is not feasible for shoulder-launched weapons due to their increased cost and weight), or the weapon has to be able to function outside the DAS envelope.

It is the second, long-standoff method that Insys Ltd has adopted to overcome this problem. Through its knowledge of shaped charges, materials and the use of the hydrocode CTH, Insys has developed a warhead that can produce a coherent jet 80-100 cone diameters (CDs) in length. For a warhead of 100 mm diameter this gives a jet of 8-10 m in length. Normally at these sorts of standoffs the jet starts to fragment into separate particles, diminishing penetration. Although there is no velocity (and subsequently no penetration) information given, the potential for overcoming the current DAS systems with this warhead can be clearly seen.

Another innovation developed by Insys since the 1980s is the system named PANDORA (Penetration And Non-Detonation Of Reactive Armour). The bi-material liner of the PANDORA warhead uses copper and the plastic PTFE (polytetrafluoroethylene) in its construction. Half of the charge's apex is PTFE and the rest is copper. When initiated, the two materials produce two jets that eventually separate, the low-density PTFE jet ending up in front of the copper. The PTFE jet, upon striking an ERA array, perforates but does not initiate it. This leaves a relatively debris-free hole for the copper jet to pass through before tackling the main armour.

EXPLOSIVELY FORMED PROJECTILES

These are an extension of the shaped-charge effect. With EFPs the warhead designer tries to form the whole liner into a projectile and not the jet-plus-slug combination of the shaped charge. This is normally accomplished by increasing the liner thickness and decreasing the liner apex angle. Although the EFPs do not perforate such a great thickness of armour they do create a much larger hole, causing significant behind-armour effects. This can be achieved at standoff ranges of up to 1,000 CDs, making EFPs attractive as the warheads for overflight and top-attack missiles, front charges for follow-through weapons and for weapons to counter DAS systems.

Current research on EFPs focuses on multipoint initiation; new liner types and materials; and explosive fills. Exploiting effects similar to those described above in the multipoint shaped charges section, one EFP warhead can be configured to produce three distinct projectile types. These include a short, long-range, aerostable projectile with a length-to-diameter (L/D) ratio of around 5; a short-range high-penetration rod (L/D 10+); and multiple projectiles. The first projectile type is effective against most light vehicles and for the top attack of heavy armour at long range (up to 1,000 CDs); the second is for the attack of heavy armour at short range (20-100 CDs); and the third is for soft targets, light vehicles and infantry.

The use of new liner materials with increased density and dynamic properties is another area of research. The increased density would improve penetration by some of the same mechanisms as anti-tank KE rounds - that is to say, by a higher energy density and increased force/pressure upon impact. The dynamic properties would involve the ductility of the material, which would lead to longer projectiles and deeper penetration.

Through the use of more powerful explosive fills, the shape (length) of the EFP and its velocity can be increased. Both phenomena give improved penetration and hole diameter by increasing the energy imparted to the target, improving the chance of a target kill.

FOLLOW-THROUGH WEAPONS

This class of warhead uses a shaped or EFP charge to open a hole in the target, through which a delayed-detonation blast/fragmentation or thermobaric bomb enters. The initial directed-energy charge's perforation and the subsequent follow-through bomb's (FTB's) detonation destroy or incapacitate the target.

FTB munitions are available for at least three weapons, including the Pzf 3 (Bunkerfaust) and IMI's Shipon and B-300, the latter licence-produced by Talley Defense as the SMAW. Others are in development by RUAG and Insys. The latter company differs in that its FTBs can be made to detonate within the hole created by the shaped charge. By using this mode (and if the FTB contains enough explosive), a hole large enough for a soldier to enter the building could be made. The RUAG weapon combines its multifunction/multipurpose charge and MEP, creating a system with formidable capabilities.

Although highly effective against light armour, bunkers and buildings, few weapons use the HESH/HEP warhead. Upon impact the warhead squashes against the target, deforming into a mushroom shape. After a few milliseconds, the base fuze is fired and the detonation wave sweeps through the explosive towards the target, which is now in intimate contact with the warhead. For thinner targets the protection material is deformed until it fails. This lets the high-pressure detonation gases into the target, along with accelerated fragments of the protection.

For thicker targets the shockwave from the detonating explosive passes directly to the protection material as a compressive shock wave. This wave then strikes the rear of the target and is reflected. The reflected wave is now not one of compression, but one that is trying to pull apart the material. If the material does not have a high enough tensile strength, it fails and the failure results in parts of the protection being flung off at high velocity within the target.

There are only three weapons in existence that use this mode of attack: the Talley Defense SMAW with the HEDP round; the Dynamit Nobel Dynamics RGW 60; and the MATADOR system co-developed by the DSTA and Dynamit Nobel Defence. The 83 mm SMAW HEDP uses a squash head round with a target sensing fuze. This detonates the aluminised HE fill in HESH mode for hard targets and in delay mode for soft.

The MATADOR uses a 90 mm dual-function deformable shaped charge. In the anti-armour mode, the charge is detonated at a standoff range using its nose probe. In anti-structure mode, the missile strikes the target and lets the warhead section deform on the target like a HESH round. After a predetermined period of time the base fuze operates, blowing a hole up to 450 mm in diameter in a double thick brick wall.

Though its use is not without risk of collateral damage, HESH is highly effective at destroying targets during MOUT and is also far less complex than other attack methods, which is of great importance in a combat situation.

MODULAR EXPLOSIVE PENETRATOR

The MEP concept was devised in South Africa by Denel (Somchem) for the HEMP (High-Explosive MultiPurpose) round of the FT5 light anti-tank weapon system. RUAG has since developed the idea further, creating MEP warheads for the RPG-7 and Pzf 3. The FT5 and the RUAG MEP projectiles function in a similar fashion. On impact, the head of the faux warhead casing is crushed and the inner projectile perforates the target using KE. After a delay of milliseconds, a time-delay fuze functions to detonate the explosive filling within the penetrator, fragmenting the projectile casing and generating a considerable blast.

The baseline RUAG MEP warhead can defeat 12.5 mm of RHA or 50 mm of aluminium, 250 mm of reinforced concrete or 1.2 m of sandbags. The RT5 HEMP warhead is credited with the ability to penetrate 15-20 mm of armour steel, 300 mm of reinforced concrete or 1.5 m of wood-lined earth fortification.

RUAG's MEP Mk2 is physically very different from the Mk1, being based on the company's high-dynamical rheological technology which endows it with more volume for a given surface. Its intelligent fuze also allows the MEP to detonate within the wall, giving the weapon a 'wallbreaker' or entry-hole creation effect. One of the applications for the new technology is RUAG's 'Ka-Bar' design for a combination of a tandem shaped-charge warhead within a strengthened casing. When fired at tanks, it functions as a tandem shaped charge, but when fired at structures it functions as a MEP.

VARIABLE-GEOMETRY WARHEADS

Variable-geometry warheads are a class of deformable multi-effect charges under development by Insys. In one model applicable to infantry weapons, the warhead has a central forward-facing charge and multiple charges mounted around the warhead's axis. The central and body charges can be any of the previously mention warheads types, or various combinations of them. Upon reaching the target, the body charges are mechanically or explosively forced to fold open towards the oncoming target.

The angle between the body and the front charge allows the warhead to vary its area of effect from a tight beam to a wide spread. When the correct angle between the body and front charges has been reached, all warheads detonate, so focusing the entire explosive power towards the target. This makes this class of warheads far more efficient than most previous designs as most of the explosive power and hence projected energy, is sent towards the target.



, Exeter

Exeter (16.08.2005 18:56:35)
16.08.2005 19:23:55

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