GB2505721A

GB2505721A - Countermeasure cartridge

Info

Publication number: GB2505721A
Application number: GB201216195A
Authority: GB
Inventors: John William George Marks; Keith Bright
Original assignee: Wallop Defence Systems Ltd
Current assignee: EST Defence Company UK Ltd
Priority date: 2012-09-11
Filing date: 2012-09-11
Publication date: 2014-03-12
Anticipated expiration: 2032-09-11
Also published as: GB201313397D0; GB2505770B; GB2505769A; GB2505769B; GB201216195D0; GB2505770A; GB2505721B; GB201313399D0

Abstract

A countermeasure cartridge comprises a payload incorporating a plurality of filament bundles and a sabot member 9. The sabot member 9 is adapted to retain the plurality of filament bundles. In use, the payload is dispensed from the cartridge and the sabot member 9 releases the filament bundles into the atmosphere to facilitate the forming of a chaff cloud.

Description

A Countermeasure Cartridge

Field of the Invention

The invention relates to countermeasure cartridges, and in particular to chaff countermeasure cartridges.

Background to the Invention

Chaff has been in use for many years, in the form of aluminised glass filaments provided in the form of "chaff hanks" containing typicalLy between 150,000 and 200,000 filaments per hank cross-section, these filaments being cut to Lengths such that a resonant back-scatter, or "radar cross section" (RCS), is obtained, so presenting a "false target echo" to a threat radar.

Naval and Air Use chaff products provide an effective RCS signature over the standard radar operating frequencies between 1.0 GHz and 18.0 GHz. The frequency of 18.0 GHz represents a practicaL operating frequency upper limit, on account of the unacceptabLe atmospheric attenuation at higher eLectro-magnetic frequencies. However, within the region of atmospheric attenuation, a number of "windows" occur, one such being in the band from 30 GHz to 40 GHz. This is of military significance for the purposes of very high resolution (high accuracy) radar tracking systems, which may operate within this window at an acceptabLe Level of radar signal attenuation.

There is military interest in the development of chaff decoy products for use in the 30 GHz to 40 GHz band, known as the "millimetric" or "mmW" band. To date however, LittLe progress has been made in the production of a practical mmW chaff payload, the reason being associated with the required "dipoLe length" (filament cut Length) necessary to obtain an efficient resonant RCS response.

The problem is illustrated by the foLlowing list of required "haLf-wave resonant" dipoLe lengths:-Radar Half-Wave Frequency Dipole Length GHz mm 2.0 75.0 4.0 37.5 8.0 18.8 9.5 15.8 14.5 103 18.0 8.3 30.0 5.0 35.0 4.3 40.0 3.8 This introduces a considerable manufacturing difficulty, reLated to the processing and assembly of the very smalL "chaff cut lengths' required at mmW frequencies, and which the mmW payload design as described in this note has been deveLoped to overcome.

Additionally, the RCS of a chaff dipole is proportionaL to the square of the dipole length.

This means that there is a physical problem in achieving a sufficiently high RCS at mmW frequencies. The solution to this problem, as described in this note, has been to adopt a very fine chaff dipole fiLament diameter, alLowing more dipoles to be packed into the available payload cross-section.

It is the purpose of this invention to provide soLutions to the foLlowing problems: * the efficient processing and assembly of the chaff payload in the course of manufacture; * the efficient deployment of smalL mitlimetric cuts to generate a RCS that is sufficientLy high for operationaL purposes.

Summary of the Invention

In a first broad independent aspect, the invention provides a Countermeasure Cartridge comprising a payload incorporating a pLurality of filament bundles and a sabot member, whereby said sabot member is adapted to retain said plurality of fiLament bundles; in use, said payLoad is dispensed from said cartridge and said sabot releases said filamentg; bundles into the atmosphere to facilitate the forming of a chaff cLoud. This configuration enables cartridge to incorporate and retain the small mmW chaff cuts, without them cross contaminating into other chaff cuts contained within the chaff payload. The contamination can occur if the filaments spill out from their retaining membrane when being Loaded in the cartridge. Furthermore, this simplifies the handLing process of the mmW when forming the chaff payload.

Another advantage of this configuration is that the sabot enables the smalL chaff cuts to be depLoyed to an effective position away from the aircraft so that it can form an effective RCS, otherwise the small mmW chaff wiLl unpredictably disperse as it exits the cartridge and not form an effective RCS.

PreferabLy, a countermeasure cartridge further comprising a wrapping means arranged about said sabot. This configuration provides contains the chaff filaments within the chaff payload as it exits the cartridge, therefore improving the dissemination of the chaff payload which subsequently reduces the phenomenon of "bird nesting", which can result in more than 50% of a conventional payLoad being lost.

PreferabLy, said wrapping means is wrapped about said sabot in the same rotational direction as the spin of said payload when dispensed from said cartridge. This enabLes a wrapped sabot to be dispensed from the cartridge, whereby the wraps unwind efficiently to provide an effective dissemination of the contained chaff fiLaments. Therefore preventing the wraps from binding, which resuLts in an inefficient dissemination of the contained chaff fiLaments; or worse stilL the dissemination of the chaff fiLaments wiLL not occur at aLL.

PreferabLy, said wrapping means is wrapped about said sabot in the range of 3 to 4 turns.

This configuration determines the controLled reLease of the chaff bundLes contained within the sabot. The controLLed reLease is used to determine the reLease over a predetermined time period and/or predetermined cloud configuration (i.e. a Long duration may create eLongated cLoud configuration).

PreferabLy, said wrapping means is a poLyimide or poLyester materiaL, or a shrink wrap materiaL. This materiaL provides heat, shock and/or pressure protection for the sabot, and the chaff fiLaments of the chaff bundLes carried within the sabot, contained chaff fiLaments, incorporated within the chaff bundLes, when the chaff payLoad is dispensed / ejected from the cartridge.

PreferabLy, said sabot member further comprises a first body member and second body member, whereby both said body members are arranged adjacent to each other to encLose said fiLament bundLes. This configuration enabLes a number smaLL mmW chaff cuts to be stacked on top each other in a predetermined sequence, thereby forming the chaff payLoad, with out any cross contamination between the chaff cuts.

PreferabLy, both said first and second body members are eLongated and whereby each said body member further comprises an open end and a closed end opposite to said open end.

This enabLes the chaff payLoad to be retained within the sabot.

PreferabLy, both said first and second body members are attached together via a hinge, whereby said hinge is arranged at said cLosed end of each said body member. This enabLes the chaff payLoad to exit the payLoad in a predetermined manner/ direction.

PreferabLy, said sabot is formed from a plastics materiaL. This enabLes the sabot to be formed from cheap, Light weight materiaL that is easy and cheap to manufacture; and wiLL aLso not impede the fLight characteristics of the chaff payLoad. Furthermore, this materiaL accepts a substantiaL amount of distortion without incurring structuraL integrity or dispensing efficiency probLems which may occur when the chaff payLoad is Loaded into the cartridge.

PreferabLy, said payLoad further comprises a second pLuraLity of fiLament bundLes and a second sabot member; whereby said second sabot member is adapted to retain said second pLuraLity of fiLament bundLes. This configuration enabLes the optimisation of the chaff cLoud properties such as chaff density and/or cLoud configuration.

PreferabLy, a countermeasure cartridge further comprising a first tube and a second tube arranged within said first tube, thereby providing a void between the waLLs of each said tube for containing said payLoad within said cartridge. This configuration enabLes the chaff payLoads to stacked about the inner tube Located within the transport tube, whereby the inner tube functions as a burster tube which ruptured after a detonation and subsequentLy distributes the surrounding chaff packs from the chaff payLoad.

PreferabLy, said void further comprising a dividing member that spans said void and is arranged on each said waLL of each said tube; thereby dividing said void into a first and second compartments. This configuration enabLes the chaff packs to be incorporated within separate payLoad compartments within the chaff payLoad, therefore providing a means of evenLy distributing chaff packs aLong the Length of the chaff payLoad.

PreferabLy, said sabot is formed as a Liner for Lining an inner surface of a payLoad chamber of said cartridge. This provides a means of dispensing aLL the chaff packs from the cartridge as one payLoad, with out any obstruction being caused by the cartridge casing.

PreferabLy, a countermeasure cartridge further comprising a second wrapping means arranged about said sabot. This configuration provides the advantage of preventing the chaff contents from disseminating and so increase the baLListic traveL of the chaff untiL the point where the LocaL air veLocity causes the wrappings to unwind. The unwrapping of the of the wrappings means can occur within 0.5 seconds, therefore by adding a number of separate wrapping means it is possibLe to taiLor the process of unwrapping, so that the dispense of the bare chaff fiLaments' is deLayed. Therefore, the wrapping the sabot with additionaL wrapping means provides an optimum chaff cloud size and I or obtain an optimum point of dissemination from the point of dispense.

Preferably, said wrapping means is formed in a Loose poLyester tube. The constant diameter tubes greatly increase the efficiency of the wrap cutting process.

In a second broad independent aspect, the invention provides a filament bundle adapted to be retained in a sabot device of a countermeasure cartridge. The sabot retains the bundle and prevents it from prematurely releasing the filaments whilst it is being deployed from the cartridge. The sabot also prevents the filament bundle from disintegrating when be loaded into the cartridge.

PreferabLy, each filament from said bundle is formed from a plurality of atuminised gLass filaments. Each filament from this configuration provides a dipole, which in use, provides a back scatter, also known as a radar cross section (RCS", which presents a false target echo to a threat radar.

Preferably, each said filament is coated in a fatty acid, which in use provides a slip enabling coating.

PreferabLy, each said filament comprises a mean coated diameter of 18.2 jim. This provides fiLament with fine diameters, which enabLe the loading of 1 50000 to 400,000 filaments into a chaff bundle.

PreferabLy, said filament comprises a ± 3-G coated diameter in the range of l3pm to 23jim.

PreferabLy, each said filament comprises an eLectrical conductivity of 10012 over a 25-cm witness length.

PreferabLy, comprising a plurality of said filaments in the range of 150,000 to 400,000 filaments. This configuration provides what is known as "Fine Filament (FE) chaff", which in use provides a denser RCS, which in turn increases its potential effectiveness of providing a false target echo.

PreferabLy, the Length of each said fiLament is in the range of 3mm to 5mm. This provides an effective radar signature over the radar operating frequencies of 30Ghz to 40Ghz.

PreferabLy, a Countermeasure cartridge payLoad comprising a fiLament bundLe as previousLy mentioned.

In a third broad independent aspect, the invention provides a method of forming a fiLament bundLe which in use, is retained in a sabot device of a countermeasure cartridge comprising the steps of: * Winding a chaff hank over an "I' shaped former device; * AppLying a shrink wrap about said wound chaff hank; and * Cutting shrink wrapped packs to required miLLimetric Length.

Brief Description of the Figures

Figure 1 shows a cross sectionaL view of a NavaL Chaff Decoy mmW PayLoad.

Figure 2 shows a pLan view of a payLoad separator member.

Figure 3 shows a cross sectionaL view of a payLoad compartment.

Figure 4a shows a schematic view of a sabot wrap.

Figure 4b shows a schematic view of sabot body sheLLs Located about a mmW payLoad.

Figure 4c shows a schematic view of a mmW payLoad stack.

Figure 5a shows an end view of a sabot over-wrap incorporating 3.25 turns.

Figure 5b shows an end view of a baton wrap incorporating 3.0 turns.

Figure 6a shows the open end view of the sabot body shells Located about a mmW payload.

Figure 6b shows a side view of the sabot body shells Located about a mmW payload.

Figure 6c shows the closed end view of the sabot body shells Located about a mmW payload.

Figure 7a shows a schematic view of a sabot over-wrap along the length of the sabot.

Figure 7b shows a side view of a sabot, with two body portions enclosed about a mmW payload.

Figure 7c show an end view of a sabot over-wrap incorporating 3.25 turns.

Figure 8 shows a schematic view of a mmW payload exiting a sabot.

Figure 9a shows the closed end view of a sabot body shell Located underneath a mmW payload.

Figure 9b shows a side view of two sabot body shelLs hinged together in an open configuration for receiving a mmW payload.

Figure 9c shows the cLosed end view of an opposite body shell located underneath a mmW payload.

Figure 10 shows a side view of a sabot, with two hinged body portions, encLosed about a mmW payLoad.

Figure 11 shows a cross sectional view of an Aircraft Self-Protection Chaff: RR1 70 Cartridge incorporating a mmW payLoad.

Figure 12a shows an end view of two liners / sabot bodies assembled in a RR17O Cartridge.

Figure lZb shows an end view of two Liners! sabot bodies assembLed together.

Figure lZc shows an end view of two Liners! sabot bodies hinged together in an open configuration.

Figure 1 Zd shows an end view of two Liners! sabot bodies hinged together in a cLosed configuration.

Figure 1 2e shows an end view of two separate Liners / sabot bodies adjacent to each other in an open configuration.

Figure l2d shows an end view of two separate Liners! sabot bodies adjacent to each other in a cLosed configuration.

Figure 13a shows an end view of a twin pack incorporating two over wrapped sabots.

Figure 1 3b shows an end view of a Loaded twin pack within a RR1 70 Cartridge.

Figure 14a shows a schematic view of two twin shrink wrap packs.

Figure 1 4b shows an end view of two twin shrink wrap packs within a RR1 70 Cartridge.

DetaiLed Description of the Figures

Figure 1 shows a navaL mmw Chaff PayLoad which in use is fitted in a navaL chaff decoy rocket.

DetaiLs of the chaff payLoad are as foLLows: Figure 1 shows a navaL decoy countermeasure cartridge, generaLLy indicated by 1 that incorporates a miLLimetric (mmW) payLoad design. The cartridge 1 incorporates a cyLindricaL tube body 2, which is cLosed at its top end with a top end disc 3 and cLosed at its bottom end with a bottom end disc 4. A second cyLindricaL tube member 5 is Located within the cyLindricaL body 2, whereby the second tube member 5 is concentric to the cyLindricaL tube body 2 and is indicated by the centraL axis AA.

A void 6 is formed between the waLL of the second tube member 5 and the cyLindrical tube body 2, which extends about the second tube memberS. The void 6 extends aLong the Length of the cartridge 1, from the top end disc 3; to the spacer bLock 11 Located on top of the bottom disc 4. The void 6 incorporates six payLoad separators 7, which divide the void 6 into five annuLar payLoad compartments 8. A payLoad separator 7 is Located on top of the spacer bLock 11, which separates the bottom payLoad compartment 8 from the spacer bLock 11. A payLoad separator 7 is Located underneath the top end disc, which separates the top payLoad compartment 8 from the top end disc 3.

Each payLoad compartment 8 incorporates a centraLLy Located sabot wrapped 9 mmW payLoad. Each sabot wrap 9 incorporates 11 chaff cuts (not shown) which are verticaLLy stacked on top of each other to form the mmW payLoad. The chaff cuts are aLso known as "Muffins".

Figure 2 shows a pLan view of a payLoad separator member 7, which is annuLar in shape.

Figure 3 shows a cross-sectionaL view of an annuLar compartmentS within the cartridge 1, which incorporates twenty singLe wrap payLoad chaff packs 9 configured into a singLe Layer upon the payLoad separator (not shown). The rotationat direction of the cartridge, as it has been ejected, is indicated by arrow 21.

Figure 4a shows a sabot wrap 9 which is simiLar to the sabot wrap shown in Figure 1. The sabot wrap 9 typicaLLy has an end to end height of 43.5 mm.

Figure 4b shows a stack of eLeven chaff cuts 10 which forms the mmW payLoad within the sabot wrap 9. The chaff cuts 10 are Loaded within two spLit body sheLLs 31 and 32 of a sabot, whereby both sabot body sheLLs 31 and 32 extend "top to bottom" of the mmW payLoad.

TypicaLLy the stack 10 incorporating eLeven chaff cuts, which forms the mmW payLoad.

The typicaL height of the chaff stack 10 is 42.75 mm. The stack incorporates an initiaL chaff cut (aLso known as a muffin) which is 4 mm in Length and which is positioned on top of a second chaff muffin that incorporates a 3.75 mm Length. This sequence of chaff muffin Lengths is repeated throughout the stack 10 of the mmW payLoad.

Figure 5a shows a cross-sectionaL view of a sabot wrap 9, which is simiLar to the wrap shown in Figures 1 and 4a. The sabot 40 is overwrapped 41 with a 195 mm polyimide materiaL, in an anti cLockwise direction and incorporates 3.25 turns.

Figure Sb shows a cross-sectionaL view of a chaff baton wrap 50. The chaff baton 50 is wrapped 51 with a 185 mm poLyimide materiaL, in an anti cLockwise direction and incorporates three turns.

Figure 6a shows the exploded end view of the stack of chaff cuts 10, which are Loaded into the open ends of the sabot's two split sheLLs 31 and 32. The open ends enabLe the stack (or mmW payLoad) to exit from the sabot, when the spLit sheLLs 31 and 32 are open.

Figure S shows a side view of the stack of chaff cuts 10 forming the mmW payload, Loaded within the two spLit shelL bodies 31 and 32 of the sabot, which are simiLar to those in Figure 4b.

Figure 6c shows the end expLoded view of the stack of chaff cuts 10 which forms the mmW payLoad, which are Loaded into the closed end of the sabots two spLit body shelLs 31 and 32. The cLosed end retains the stack 10 within the sabot, when the spLit shelLs 31 and 32 are cLosed.

Figure 7a shows the sabot overwrap 9 is simiLar to the sabot shown in Figures 1 and 4a, where the sabot is wrapped aLong its length.

Figure 7b shows the two spLit body shelLs 31 and 32 of the sabot are Located about the stack of chaff cuts (i.e. muffins) which forms the mmW payLoad.

Figure 7c shows the sabot overwrapped by 3.25 turns, with a 195 mm poLyimide wrap materiaL, which is very similar to the sabot overwrap in Figure 5a.

Figure 8 shows an aLternative embodiment of the sabot, where the two spLit body shelLs 31 and 32 are hinged together at one end by a hinged attachment means 70. When the payLoad is deployed, the mmW chaff payLoad exits the open sabot via its open, unhinged end generaLly indicated by 71. Both spLit body shelL and hinged body sheLL embodiments of the sabot have the same overwraps and open in the same manner.

Figure 9a shows the exploded end view of the stack of chaff cuts 10, which forms the mmW payLoad. The stack 10 is Loaded into a first body sheLL 32 of the sabot. The body 32 has a cLosed end which retains the mmW payLoad.

Figure 9b shows a side view of the stack of chaff cuts 10, which forms the mmW payLoad.

The stack 10 is loaded into the first hinged body member 32 of the sabot. The second body 31 of the sabot is shown to be open and empty, whiLst being attached to first body member 32 via the hinged attachment means 70.

Figure 9c shows an expLoded end view of the stack of chaff cuts 10, which forms the mmW payload. The stack 10 is shown not to be Loaded into the body 32 of the sabot.

Both spLit body sheLLs 31 and 32 have cLosed ends, which when closed, meet and retain the mmW payLoad.

Figure 10 shows the two hinged bodies 31 and 32 of the sabot, encLosed about the stack of chaff cuts 10, which form the mmW payLoad, via the hinge attachment means 70. The direction of closure of the two hinged bodies 31 and 32 is shown by arrow 71.

In use, the payLoad: Is dispensed by a combination of the high stabiLising spin rate of the rocket and an expLosive expuLsion charge contained in a centraL "Burster Tube".

30. Is protected by wrappings, which aLso control the rate of dissemination of the chaff to form an efficient chaff cLoud. For this purpose, the wrappings are "spin-sensitive" with respect to the spin direction of the rocket, which assures that the wraps unwind efficientLy. If the wraps were to unwind in the "opposite hand/direction" with respect to the spin direction of the rocket, the wraps wILL bind and dissemination of the chaff filaments will be either inefficient or not occur at all. Therefore, the wrap direction being in the same sense as the spin direction, as shown in Figure 5.

* The mmW payload is manufactured from a chaff hank of "Fine Filament" (FF) aluminised glass material, the filament diameter being such that it is possible to contain 340000 of filaments in the finished chaff bundle cross-section. Each filament is formed from a glass fibre, such as an E-glass fibre material coated with 99% pure a Eu mini u m" * The basic chaff hank is over-wrapped with a polyimide wrapping film, to a specification that allows the wrapping to protect the chaff from the pressure and heat associated with an explosive expulsion. The film also has efficient un-wrapping characteristics, allowing a "controlled" unwinding of the wrappings to be incorporated in the design.

Furthermore, when the polyimide wrapping materiat is incorporated within naval chaff payloads, it provides a "blast resistant film' and serves the additional heat flash and shock associated with an explosive burster tube expulsion system. This function of the polyimide material is essential when implementing millimetric sabots formed from a plastic(s) material, as it completely protects the sabot and facilitates the dissemination of the contained chaff filaments, at the required distance.

* The polyimide-wrapped 340,000 chaff hank is referred to as a "wrapped baton" and the baton is cut to form the individual chaff dipole cuts, which are referred to as "muffins".

In Figure 1 these "muffins" are shown with lengths of 4.00mm and 3.75mm. These muffin lengths and the ratio of their numbers within the chaff payload provide for an optimised RCS response at the required peak operating frequency between 30 GHz and GHz.

* The chaff cuts (muffins) are collected from the cutting process and placed into a holder, which is referred to as a "sabot". This "sabot" is of vacuum-formed plastic construction. There are two possible embodiments of the sabot which are illustrated in Figures 6 to 10 these are: - (a) Split-Shell Sabot A two-piece construction, the pieces being blanked off at one end to assist with containment of the payLoad.

(b) Hinged Sabot IdenticaL to the Split-ShelL Sabot, but hinged at the bLanked-off end.

As shown in Figure 1, the Loaded sabot is over-wrapped with a further winding of poLyimide fiLm. This additionaL poLyimide wrapping provides heat and pressure protection for the vacuum-formed pLastic sabot, and further controLs the rate of dissemination of the chaff cLoud.

As shown in Figure 1, the aforementioned navaL chaff payload comprises a wrapping, which is intended to prevent the dissemination of the chaff filaments untiL the chaff bundLes are at a sufficient distance from the burst centre, therefore providing a Large chaff cLoud diameter. NavaL chaff payloads may empLoy arrangements of singLe, doubLe and/or tripLe-wrapped chaff bundLes, which are intended to "fiLl" a Large chaff cLoud efficientLy. This refinement of the navaL chaff payload is not required on the smaLler (76mm to 80mm diameter chaff rockets) because they are designed to be Launched in a saLvo and thereby form a chaff screen The over-wrapped sabots, referred to as "singLe bundLe packs" are Loaded into the casing of the decoy rocket. To further improve the efficiency of the chaff cLoud, additional wrapping may be incorporated, to produce a set of "wrapped packs" as follows: - (a) SingLe BundLe Wrapped Packs SingLe wrapped sabots, as shown in Figure 1.-caLLed "SingLe Packs" (b) DoubLe BundLe Wrapped Packs Two sabots are over-wrapped to produce a "Twin Pack" (c) TripLe BundLe Wrapped Packs Three sabots are over-wrapped to produce a "Triple Pack" Therefore, the chaff cLoud properties of the aforementioned navaL chaff payLoad may be optimised by using seLected numbers of "SingLe", "DoubLe" and "Triple" packs in the payLoad design.

Figure 11 shows an aircraft seLf-protection chaff -RR1 70 cartridge, generaLLy indicated by 81, that incorporates a miLtimetric (mmW) payLoad. The cartridge 81 incorporates a cyLindricaL tube body 82, which is cLosed at its top end by a top end cap 83 and its bottom end cap via a base end sub-assembLy 84. The base end assembLy 84 incorporates an eLectricaL contact assembLy 85 which detonates a squib device (not shown) and ejects the mmW payLoads 86 from the cartridge 81.

The void 87 within the cyLindricaL tube body 82 provides the means for storing four mmW payLoads 86 within the cartridge 81. The four mmW payLoads 86 are stacked on top of each other in a tandem configuration. The four mmW payLoads 86 are contained within a sabot 88, whereby the sabot 88 aLso functions as an internaL Liner to the cartridge 81.

Each chaff pack 84 incorporates two chaff bundLes 89 and 90. The first chaff bundLe 89 incorporates five chaff cuts (muffins) stacked on top of each other. The top muffin is 4.25 mm in Length. The adjacent three muffins beLow the top muffin are 3.75 mm in Length and the adjacent bottom muffin, below the previous three muffins, is 4.0 mm in Length.

The second chaff bundLe 90 incorporates six muffins stacked on top of each other. The top muffin is 4 mm in Length. The adjacent three muffins beLow the top muffin are 3.75 mm in Length. The adjacent muffin beLow the previous four muffins is 4 mm in Length. The bottom muffin beLow the previous 5 muffins is 4.25 mm in Length.

The combined height of aLL the chaff muffins for bundLe 1 is typicaLLy 19.5 mm. The combined height for aLL the chaff muffins for bundLe 2 is typicaLly 23.5 mm.

The two chaff bundLes 89 and 90 are arranged on top of each other to form an overaLL mmW payLoad 91.

The four chaff packs 86 are Loaded into the Liner 88, and may aLternativeLy be formed from either a singLe chaff pack or twin chaff pack configurations.

Figure 12a shows an end view of two Liners 88 assembLed about a payLoad 91 in a RR17O cartridge 81.

Figure 12b shows an end view of two Liners 88 assembLed together.

Figure 12c shows an end view of two Liners 88 hinged 100 in an open configuration.

Figure lZd shows an end view of two Liners 88 hinged 100 in a cLosed configuration.

Figure 12e shows an end view of two separate Liners 88 adjacent to each other in an open configuration.

Figure 1 2f shows an end view of two separate Liners 88 adjacent to each other in a cLosed configuration.

Figure 13a shows a cross-sectionaL view of a "twin pack" chaff pack 93 incorporating two chaff packs 94 and 95, which aie overwrapped with a polyimide wrapper 96. Both packs 94 and 95 incorporate 340000 chaff fiLament bundLes. Each chaff pack 94 and 95 is wrapped in a rotationaL directions indicated by arrows 97 and 92 respectiveLy. The poLyimide wrapper 96 is wrapped about both packs in a rotationaL direction indicated by arrow 98.

Figure 13b shows an end view of an overwrapped "twin pack" 102 chaff pack 93 assembLed within a RR17O cartridge 81. When two or more packs are Loaded into a given space they distort to take up the avaiLabLe room within the cartridge 81. The amount of overLap is determined by the actual bundLe distortion of each pack, whiLst it is being Loaded into the cartridge. This was a potentiaL probLem for with using miLLimmetric pLastic(s) "sabots". However, they provide the advantage of accepting a Lot of distortion without incurring structuraL integrity or dispensing efficiency probLems.

Figure 14a shows an end view of the two "twin pack" chaff packs 101 shrink wrapped together. The shrink wrapped packs are Loaded in the LongitudinaL direction within a cylindricaL casing of a rocket payLoad, or aLternativeLy the square 1 inch x 1 inch section of the RR17O I RR18O standard aircraft chaff cartridges.

Figure 14b shows an end view of the two "twin pack" chaff packs 101 assembLed within a RR17O cartridge.

In use, the payLoad is configured for use with the RR1 70 Aircraft Chaff Cartridge; however, the constructional principLes can be applied to other types of aircraft chaff cartridge. In particuLar, the constructional principles are directLy applicable to the RR18O Aircraft Chaff Cartridge.

As shown in Figure 11, the basic construction of the mmW payLoad wILL be seen to be identicaL to that used for the NavaL Chaff Decoy mmW payLoad as shown in Figure 1.

In the case of the Aircraft mmW payload, whiLst poLyimide wrapping may be retained, the use of an aLternative poLyester or simiLar wrapping materiaL may be approved by the design authority. Furthermore, the wrapping does not usuaLLy have to serve a protective purpose, unlike the previously mentioned navaL chaff payLoad. The chaff is ejected from the containing cartridge by means of a piston arrangement pLaced over a pyrotechnic impuLse squib. In this case the wrapping may be an aLternative poLyester materiaL, such as "MeLinex" TM The wrapping then serves the folLowing functions: (a) providing a practicaL means of handling the chaff cuts for assembly; and * (b) providing efficient dissemination of the chaff payload on ejection form the cartridge, therefore reducing the phenomenon of "birdnesting", which can otherwise resuLt in ore than 50% of the payLoad being effectiveLy lost.

However, some aircraft cartridges have powerfuL impuLse squibs, and where this is the case poLyimide blast-proof fiLm/materiaL may be required.

As shown in Figure 11, the 340000 chaff cuts are over-wrapped and contained within a "cartridge Liner" which fits into the body of the RR1 70 cartridge (the "cartridge Liner" is a form of sabot).

The Liner may comprise two separate pieces, or the pieces may be hinged at one end, or aLong one side, as shown as an alternative construction scheme in Figure 11.

An alternative chaff payload scheme employs a 170,000 fine filament chaff hank which is folded over an I-section former to produce the 340,000 bundle size. Two of these 340,000 bundles in I-shaped formers can be contained within the RR17O cartridge body -this aLternative construction arrangement is aLso shown in Figure 11. This method of construction is also applicable to the RR18O chaff cartridge.

For the constructionaL scheme as shown, the cartridge case is of the standard RR1 70 design and incorporates the standard BBU-35b or equivalent expulsion squib and the standard RR170 end-cap.

ALternative cartridge cases and seaLing arrangements may be employed, in accordance with customer requirements and incLuding waterproof designs for the body, squib sealing and end cap.

To accommodate specific baLlistic requirements for the ejected payLoad, variants may be included in the design as follows: - (a) The wrappings may be of a multipLe type to deLay blooming of the chaff cloud.

(b) In place of the single liner, multiple liners may be introduced.

(c) The multipLe Liners may be associated with a "Multi-Shot' design, such that between 2 and 4 sub-payloads can be ejected in a defined sequence.

(d) The liners may be over-wrapped to further deLay the blooming of the chaff cloud.

(e) The liners may be omitted and a wound bundle system introduced to maximise the bloom response (this may be particuLarly associated with the I-former construction option).

Multiple chaff over-wrappings prevent the chaff contents from disseminating and so increase the ballistic travel of the chaff until the point where the locaL air velocity causes the wrappings to unwind. This "unwrapping" can itself occur in Less than 0.5 seconds. By adding a number of separate wraps we can "taiLor" the process of unwrapping so that dispense of the "bare chaff filaments (also known as dipoLes)" is delayed.

Therefore, this multiple wrap technique obtains an optimum chaff cloud size, and/or obtain an optimum point of chaff dissemination from the point of payload dispense.

If no wrapping are used to contain the chaff filaments, the chaff fiLaments would disseminate quickly (typicaLly within 0.1 second), because the individual chaff dipoles wouLd be brought to the Local air speed (i.e. they travel with the local wind speed) in less than 0.01 seconds. Therefore, a pack of "bare chaff dipoLes" would be dispensed very quickly and subsequently cannot form an optimaLly large cloud.

ALso, multiple short wrap lengths are better than one long wrap Length -long wrap Lengths tend to "bind" so that the actual dispense of the chaff dipoles can be very inefficient.

As mentioned previously, the chaff payload incorporates aluminium glass filaments, which are cut to Lengths to obtain a RCS.

The RCS of a chaff payload is proportional to the square of the half-wave resonant dipole length (Ah). This means that at mmW frequencies, with a relative dipole length L, (LR = Ah / Ahrnmw) the RCS at the mmW frequency is reduced in proportion to 1/LR2. At the same time, the shorter mmW dipoLe length aLlows the same payLoad space to contain a Larger number of dipoles, in direct proportion to LR. The net effect is that the overall reduction in RCS at the equivalent mmW half-wave resonant frequency is proportional to (1/LR2)(LR), which is 1/LR. Relative to mmW frequencies, LR then takes values in the order of x4 at the I-Band frequencies and x2 at the J-Band frequencies, giving reLative reductions in mmW RCS of xO.?5 I-Band and xO.5 i-Band.

To counteract these comparative RCS reductions over the mmW frequency band, the current design makes use of a "Fine Filament" ("FF") aLuminised glass construction for the chaff payload hank.

Current chaff payLoads empLoy either 23-micron or 25-micron coated diameter chaff fiLaments as the finest diameter that is generaLLy practicaL for chaff hank manufacture. In comparison, EsterLine have introduced an "FE" aLuminised gLass chaff fiLament hank with the foLLowing characteristics: -Mean coated diameter 18.2um ± 3-a coated diameter range 1 3um to 23um ELectricaL conductivity 1001 over a 25-cm fiLament witness Length For the mmW payLoads, a design chaff bundLe fiLament count of 340,000 is empLoyed as standard.

The associated design specification "FE" chaff hanks are then: (a) for baton-wrapped hanks to form standard wrapped bundLes: -340,000; (b) for speciaL packs using an "I-section former, doubLed hank: -170,000.

Given the same payLoad voLumes, the "FE" payLoad contains 1.6x the number of equivaLent 23um dipoLes and 1.9x the number of equivaLent 25um dipoLes.

It has been suggested that, rather than adopt the smaLL haLf-wave resonant mmW cut Lengths, the "second resonance" (fuLL wave resonant response) of equivaLent i-band dipoLes be empLoyed. However, caLcuLation shows that equivaLent J-band fuLL wave resonant dipoLes wouLd provide onLy 68% of the RCS response produced by the haLf-wave resonant mmW dipoLes -a Loss in potentiaL effectiveness of 32%.

In an aLternative embodiment of the invention, the chaff payLoad is incorporated within a "shrink wrapped pack" for use in aircraft chaff dispensing systems, particuLarLy those systems which empLoy a mechanical piston type of chaff payload ejection system. This configuration of the chaff payLoad provides production advantages in the terms of the ability to use automatic assembly machinery. A shrink wrap pack" has a diameter of approximately 45mm and the shrink wrap is slit by special cutters during the dispensing process.

In another embodiment of the invention, the shrink wrap packaging is adopted in association with a "former device", which in use provides a very high chaff cartridges packing density. The shrink wrap is slit on loading the shrink wrapped payload into the cartridge.

In another embodiment of the invention, the shrink wrap packaging is replaced by a constant-diameter polyester loose tube, whereby the payload comprises a number of loose wrapped bundles which are forced into the constant-diameter tube using a mandrel.

The Loaded packs are subsequently employed with mechanical piston-ejection systems.

The advantage of the constant diameter tubes (which replace the aforementioned shrink wraps) greatly increase the efficiency of the wrap cutting process.

The detailed design features for the mmW payload are summarised as follows: - 1. The use of a "Fine Filament" ("FE") chaff hank, with the following characteristics: (a) aluminised glass filament construction, with a fatty-acid or similar slip-coating; (b) aluminised glass filaments with a mean coated diameter of 18.2um; (c) aluminised glass filaments with a ± 3-c coated filament diameter range of 13.Oum to 23.Oum; (d) aluminised glass filaments with a maximum electrical conductivity of; 1001 over a 25-cm filament witness length; (e) the aluminised glass chaff hank to contain the following filament counts per chaff hank cross section as standard; Type 1 170-K (170,000 filaments) Type 2 340-K (340000 fiLaments) (1) the design cLaims shaLL be incLusive of "FE" chaff hanks to be manufactured in the foLLowing fiLament count range: 150-K fiLaments to 400-K fiLaments (150,000 to 400,000 fiLaments) 2. 340-K "FE" chaff hanks (or between 150-K and 400-K as required) are over-wrapped with potyimide fiLm (or an approved alternative wrapping materiaL) to produce wrapped batons".

3. The wrapped batons are cut to produce mmW "chaff muffins" in mmW cut Lengths (mmW haLf-resonant dipoLe Lengths) seLected to achieve the required RCS performance from the foLLowing Lengths in mm (miLLimetres) and with a toLerance of ± 0.5mm per cut Length. Such as: 3.50mm, 3.75mm, 4.00mm, 4.25mm and 4.50mm 4. A design aLternative to (2) is the use of an T-shaped former over which is wound a 170-K "FE" chaff hank, a shrink wrap being then apptied to form the basis of a 340-K "FE" shrink-wrap chaff pack set. The shrink-wrapped packs are cut to a seLection of required mmW cut Lengths from those defined at (3) above.

5. The individuaL baton-wrap cuts or shrink-wrapped cuts are picked out in bundLe sets and pLaced within a retention sabot or "Liner". The sabots are of vacuum-formed pLastic construction and may be bLanked-off at one or both ends to secure the individuaL mmW chaff cuts in pLace. The sabots may be of separate 2-part construction of a 2-part hinged construction as detaiLed in the design exampLes.

6. In accordance with the design requirements, the sabots may be over-wrapped with a protective poLyimide fiLm, or an aLternative wrapping materiaL as approved by the design authority. A sabot thus formed is referred to as a "payLoad pack".

7. PayLoad Packs as defined at {6} shall singly or in multiples form a millimetric chaff payload. The payload packs may be further over-wrapped to form a payload comprising a defined set of "Single", Double and Triple wrapped payload packs.

The manufacturing steps for providing the millimetric chaff payload are: {1) A fine filament chaff hank is wrapped in polyimide (or approved equivalent) film, forming a "hff baton" {2) The chaff baton is cut on a guillotine, forming the individual chaff cuts, c. 4mm in thickness (diameter c. 16mm) called "muffins" (i.e. they are "discs" of chaff with a retaining "ring" of film, the film being a loose wrap that will unwind on dispensing) (3) The "muffins" are Loaded into the sabot, which comprises two shells, hinges and closed at one end, open at the other (4) The sabot is overiwrapped with a polyimide of other approved wrapping film (5) The sabots may be then loaded directly into the paytoad casing, or may be further over-wrapped (singly or in pairs / triple I quad arrangements) to form various types of "chaff packs" before final loading into the payload casing. These arrangements of "packs" can assist in optimising the chaff cloud formation.

Claims

Claims 1. A Countermeasure Cartridge comprising a payload incorporating a plurality of filament bundles and a sabot member, whereby said sabot member is adapted to retain said plurality of filament bundles; in use, said payload is dispensed from said cartridge and said sabot releases said filament bundles into the atmosphere to facilitate the forming of a chaff cloud.
2. A cartridge in accordance with claim 1, further comprising a wrapping means arranged about said sabot.
3. A cartridge in accordance with claim 2, wherein said wrapping means is wrapped about said sabot in the same rotational direction as the spin of said payload when dispensed from said cartridge.
4. A cartridge according to claims 2 or 3, wherein said wrapping means is wrapped about said sabot in the range of 3 to 4 turns.
5. A cartridge according to any of the preceding claims, wherein said wrapping means is a polyimide or polyester material, or a shrink wrap material.
6. A cartridge according to any of the preceding claims, wherein said sabot member further comprises a first body member and second body member, whereby both said body members are arranged adjacent to each other to enclose said filament bundles.
7. A cartridge according to claim 6, wherein both said first and second body members are elongated and whereby each said body member further comprises an open end and a closed end opposite to said open end.
8. A cartridge according to claim 7, wherein both said first and second body members are attached together via a hinge, whereby said hinge is arranged at said closed end of each said body member.
9. A cartridge according to claim 6, wherein said sabot is formed from a pLastics material.
10. A cartridge according to any of the preceding claims, wherein said payload further comprises a second pLurality of filament bundles and a second sabot member; whereby said second sabot member is adapted to retain said second plurality of filament bundLes.
11. A cartridge according to any of the preceding claims, further comprising a first tube and a second tube arranged within said first tube, thereby providing a void between the walls of each said tube for containing said payload within said cartridge.
12. A cartridge according to claim 11, wherein said void further comprising a dividing member that spans said void and is arranged on each said wall of each said tube; thereby dividing said void into a first and second compartments.
13. A cartridge according to any of the preceding claims ito 10, wherein said sabot is formed as a liner for Lining an inner surface of a payload chamber of said cartridge.
14. A cartridge in accordance with claim 1, further comprising a second wrapping means arranged about said sabot.
15. A cartridge according to any of the preceding claims, wherein said wrapping means is formed in a loose polyester tube.
16. A countermeasure cartridge as hereinbefore described and/or ilLustrated in any appropriate combination of the accompanying text and/or Figures.
17. A chaff filament bundLe adapted to be retained in a sabot device of a countermeasure cartridge.
18. A bundle according to claim 17, wherein each filament from said bundLe is formed from a pLuraLity of aluminised gLass fiLaments.
19. A bundLe according to claim 181 wherein each said fiLament is coated in a fatty acid, which in use provides a slip enabling coating.
20. A bundle according to any of the preceding claims 18 to 19, wherein each said filament comprises a mean coated diameter of 18.2 pm.
21. A bundle according to any of the preceding claims 18 to 20, wherein each said filament comprises a ± 3-6 coated diameter in the range of l3Rm to 23Rm.
22. A bundle according to any of the preceding claims 18 to 21, wherein each said filament comprises an electrical conductivity of 100«= over a 25-cm witness Length.
23. A bundle according to any of the preceding claims 18 to 22, further comprising a pluraLity of said filaments in the range of 1 50000 to 400,000 filaments.
24. A bundle according to any of the preceding claims 18 to 23, wherein the Length of each said filament is in the range of 3mm to 5mm.
25. A Countermeasure cartridge payLoad comprising a filament bundle in accordance with any of the claims 17 to 24.
26. A filament bundle as hereinbefore described and/or illustrated in any appropriate combination of the accompanying text and/or Figures.
27. A method of forming a filament bundle, which in use, is retained in a sabot device of a countermeasure cartridge comprising the steps of: * Winding a chaff hank over an "I" shaped former device; * AppLying a shrink wrap about said wound chaff hank; and * Cutting shrink wrapped packs to required millimetric length.
28. A method of forming a fiLament bundLe as herein before described and/or iLLustrated in any appropriate combination of the accompanying text and/or Figures.amendments to the claims have been filed as follows 1. A Countermeasure Cartridge comprising a payload incomorating a plurality of filament bundles and a sabot member, whereby said sabot member is adapted to retain said plurality of filament bundles; in use, said payload is dispensed from said cartridge and said sabot releases said filament bundles into the atmosphere to facilitate the forming of a chaff cloud.2. A cartridge in accordance with claim 1, further comprising a wrapping means w arranged about said sabot, 3. A cartridge in accordance with claim 2, wherein said wrapping means is wrapped about said sabot in the same rotational direction as the spin of said payload when dispensed from said cartridge.4. A cartridge according to claims 2 or 3, wherein said wrapping means is wrapped o about said sabot in the range cf 3 to 4 turns.o. A cartndge accorthng to any of the precedrng clauns, wneren said wrapp3ng means is a poLymde or polyester material or a shrink wrap material 6. A cartridge according to any of the preceding claims, wherein said sabot member further comprises a first body member and second body member, whereby both said body members are arranged adjacent to each other to enclose said filament bundLes, 7. A cartridge according to claim 6, wherein both said first and second body members are elongated and whereby each said body member further comprises an open end and a closed end opposite to said open end, B. A cartridge according to claim 7, wherein both said first and second body members are attached together via a hinge, whereby said hinge is arranged at said closed end of each sad body member.9. A cariridge according to cLaim 6, wherein said sabot is formed from a pLastics material.10. A cartridge according to any of the preceding claims, wherein said payload further comprises a second plurality of filament bundles and a second sabot member; whereby said second sabot member is adapted to retain said second plurality of filament bundles.11. A cartridge according to any of the preceding claims, further comprising a first tube arid a second tube arranged within said first tube; thereby providing a void between the walls of each said tube for containing said payLoad within said cartridge.12. A cartridge according to cLaim 11, wherein said void further comprising a dividing 0') iS member that spans said void and is arranged on each said waUof each said tube; thereby divicing said void into a first and second compartments.0 13. A cartridge according to any of the preceding cLaims 1 to 10, wherein said sabot is formed as a Liner for Lining an inner surface of a payload chamber of said cartridge.14. A cartridge in accordance with claim 1, further comprising a second wrapping means arranged about said sabot, 15. A cartridge according to any of the preceding cLaims, wherein said wrapping means is formed in a Loose polyester tube, 16. A countermeasure cartridge as hereinbefore described and/or illustrated in any appropriate combination of the accompanying text and/or Figures.