Charles A. Borcher et al- Incendiary Fragmentation Warhead

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United States Patent [19]Borcher et al.

[11][45]

4,106,411Aug. 15, 1978

[54] INCENDIARY FRAGMENTATIONWARHEAD[75] Inventors: Charles A. Borcher, Maitland;William R. Porter, Orlando; MartinH. Harris, Winter Park, all of Fla.[73] Assignee: Martin Marietta Corporation,Orlando, Fla.[21] Appl. No.: 609,777[22] Filed: Sep. 2, 1975

Related U.S. Application Data[63] Continuation of Ser. No. 103,903, Jan. 4, 1971,

abandoned.[51] Int. Cl.2 F42B 13/48[52] U.S. Cl. 102/67; 10216;102124HC; 102/65; 102166; 102190[58] Field of Search 10216, 65, 66, 67, 90,102124HC[56] References Cited

U.S. PATENT DOCUMENTS2,801,590 8/1957 Balke et al. 102/903,263,612 8/1966 Throner, Jr 102/67

FOREIGN PATENT DOCUMENTS555,279 3/1957 Belgium 102167636,921 9/1963 Belgium 102149.2669,449 8/1963 Canada 102167

Primary Examiner- Verlin R. PendegrassAttorney, Agent, or Firm-Julian C. Renfro; Gay Chin[57] ABSTRACTIn order to achieve a fragmentation device having ahighly effective coupling between the fragments andhigh explosive used therewith, as well as a very lethalincendiary effect when combined with a pyrophoricingredient, enabling this device to bring about increaseddevastation upon supplies or equipment of an enemy,we provide in accordance with this invention a novellayered arrangement in which one or more layers ofpyrophoric material such as a zirconium alloy are inter-posed with one or more well-defined layers of highexplosive and fragments, thus making possible veryhigh fragment velocities, a high density, uniform pat-tern of fragments, and most importantly, a wide disper-sion of pyrophoric particles with the fragments thatserve to cause immediate conflagration of any oils, fuelsor other combustibles that are in the vicinity of thetarget, or which have been released by the action of thefragments thereupon.

20 Claims, 5 Drawing Figures

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separated burning particles must be hot enough andretain a sufficiently high combustion temperature longenough to ignite suitable substances such as combustiblegases or liquid or solid fuels. The pyrophoric substances5 must be sufficiently stable to be suitable for rough han-dling and to resist for sufficiently long periods the cor-rosive influences to which they are subjected in normaluse.In other words, the term pyrophoric denotes a mate-rial, usually a metal alloy, which is ignited in a weapondetonation, and continues to support combustion. Thepyrophoric material we use is in a form or state whichwill not ignite spontaneously, and hence is quite safe tohandle. The incendiary effects brought about in accor-15 dance with this invention result from the inclusion ofthe pyrophoric material.Because of the positioning of this material with theother components of the munition, upon detonation ofthe explosive, the fragments are caused to disperse, andthe pyrophoric material caused to break into a verylarge number of small pieces, some of which are causedto be clad to the fragments, while others of the smallpieces of pyrophoric material are propelled through theair by themselves. Because these particles are at a tem-perature of approximately 3,500 K, they cause an im-mediate and catastrophic fire when they come intocontact with diesel fuel, oils, lubricants, other combusti-bles, and most violently with fuels of a highly volatilenature such as gasoline.In a preferred embodiment, the external case of themunition is a hard metal such as steel, tungsten carbide,or similar material, immediately inside of which may bea thin liner or layer of pyrophoric material such aszirconium tin. Immediately inside the zirconium tinlayer may be a layer of explosive, compatible with thezirconium tin, and amounting to an arrangement whichmay be handled safely and which is nontoxic. Suchexplosives may for example include Composition B,cyclotol, octol, and C-4.Thus, a single layer offragments, zirconium alloy andexplosive amounts to a lethal arrangement that may beeffectively used in a comparatively small weapon suchIn accordance with the present invention, a novel as a bomblet. Other arrangements within the spirit oflayered fragmentation device is taught which involves this invention may include two or more layers of frag-one or more well defined layers of fragments, with each 45 ments, zirconium alloy, and explosive, although infragment layer being separated by a suitable layer of many instances it will not be necessary to have zirco-explosive material. As will be seen, our novel layered nium alloy inside each fragmentation layer. Also, thefragmentation device may take the form of succession zirconium alloy or other pyrophoric material may beof cylindrical layers; a spherical bomblet designed to disposed other than between the fragment and explosiverotate as it falls; a stacked longitudinal array of planar 50 layers, and may for example be disposed outside thelayers; or a shaped charged type device, with it being fragment layer.understood that in each instance, at least one layer of With regard to the use herein of pyrophoric metal, itpyrophoric material isused, typically disposed between is known that when such metal is subjected to an explo-a layer of fragments and a layer of explosive. The ar- sive shock, brittle fracture occurs. This disintegrationrangement is such as to enable the substantially simulta- 55 exposes hot metal to the atmosphere and since pyro-neous detonation of the explosive layers and hence an phoric metals are highly reactive with oxygen, a rapideffective, uniform, high density fragment pattern, but oxidation or burning occurs on the bared surface. Thiseven more significantly, an incendiary effect creating process occurs slower under ambient conditions andimmediate and catastrophic fires as a result of the inclu- normally is terminated when a thin oxide layer is builtsion of the pyrophoric material. 60 up on the surface, protecting the nascent metal of theThe present novel weapon distinguishes over all interior volume from contact with oxygen. However, ifknown prior art explosive devices by the fact that it the local temperature at the surface can be maintainedcontains pyrophoric fragmentating material, either with above the metal-oxide melting point, the oxide iscontin-or without nonpyrophoric fragmenting material. The ually removed and the burning is sustained. The ability

term pyrophoric as used herein relates to metals and 65 to maintain this high temperature is believed to be thealloys which exhibit pyrophoric effects in response to fundamental attribute of effective pyrophoric metals.impulse from detonation and/or impact. For such alloys The energy (heat of combustion) released throughand metals to be technically useful, the mechanically combustion of the metal surface tends to increase the

1 4,106,411INCENDIARY FRAGMENTATION WARHEADThis is a continuation of patent application Ser. No.

103,903, filed Jan. 4, 1971, and now abandoned.CROSS REFERENCE TO RELATEDAPPLICATION

This invention may be regarded as having a definiterelationship to the allowed patent application of 10Borcher and Porter entitled "Layered FragmentationDevice," Ser. No. 249,458, filed Apr. 28, 1972, which isa continuation-in-part of a continuation-in-part applica-tion based upon an original application filed Jan. 3,1966.

BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to fragmentation devices, andmore particularly to a device utilizing fragments and 20explosive in discrete, alternating layers. Italso relates to

shaped charges. The present invention distinguishesover such weaponry as taught in the above-citedBorcher and Porter application by additionally provid-ing at least one layer of pyrophoric material, preferably 25interspersed between a layer of fragments and a layer ofexplosive.2. Description of the Prior ArtIn the past, a number of fragment type warheads havebeen proposed, but these have suffered from numerous 30disadvantages, including the fact that a comparativelyhigh explosive-charge-to-metal ratio was required inorder to achieve the desired fragment projection veloc-ity. Such prior art configurations typically involved asingle explosive burster charge surrounded by frag- 35ments, but because of low coupling efficiencies, a con-siderable amount of explosive was required if desirablyhigh fragment velocities were to be achieved with alimited number of fragments. Catastrophic fires did notusually result from the action of weapons of this type. 40SUMMARY OF THE INVENTION

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3temperature, while both conduction and radiation tendto reduce the temperature. All three processes are ratelimited: combustion, by surface area and available oxy-gen; conduction, by internal temperature gradient, par-ticle mass and thermal conductivity; and radiation, by 5external temperature gradient and emissivity.As particle size is decreased, the internal volumedecreases faster than the surface area since these areproportional to the cube and square respectively of thelinear dimensions. When volume issmall, loss of heat by 10conduction is minimized since there is no large mass ofmetal to function as a "heat sink." Therefore, smallerparticles of any material are more likely to sustain burn-ing. For each type of pyrophoric metal there is a criticalparticle size for maximum support of combustion. 15Larger fragments would be rapidly extinguished,smaller fragments would be more rapidly consumed.Maximum burning time as interrelated to fragment sizeand velocity is desired for pyrophoric munitions toincrease effective range and probability of ignition of 20target materials.Several "transition temperatures" may exist for onemetal or alloy due to different changes in oxidation rateoccurring at different temperatures. The correct transi- 25tion temperature is important to incendiary action. Forexample, titanium has a "transition temperature" near8500 C due to a second type of oxide forming, but prob-ably the true transition temperature ishigher where theoxide is dissolved in the metal. Thus, titanium is proba- 30bly a transition temperature controlled metal ratherthan a critical temperature controlled metal as sug-gested by some.The pyrophoric material size effect warrants furthercomment. Fine particles have a higher surface to vol- 35ume ratio so that as the particles oxidize the relativelylarger amount of heat produced per unit volume byoxidation 'will cause higher temperatures in the parti-cles. Thus, smaller particles will ignite where the samematerial in bulk form will not ignite. 40If the ambient air pressure is lower (for example, athigh altitudes), the ignition temperature may be low-ered. This effect isbelieved to be due to the fact that thevapor pressure of the metal can be greater than thepressure of the surrounding atmosphere. The pressure 45differential can rupture the protective oxide seal. Alu-minum and zinc are believed to behave in this manner.The explosion of the munition does several things tothe pyrophoric metal. Itsupplies energy producing heatand causes metal fracture. Fresh metal surfaces are 50exposed both from the metal to metal fracture and the

spalling of oxide layers where present. The resultingmetal particles can be heated above the critical or igni-tion temperature by the explosion and will be self-heated toward the flame temperature.Much work has gone into studying metal burning,and a number of models have been postulated. Mostmodels are similar in many respects, for example, thevaporization of the metal from the particle and theoxidation of the metal vapor in the flame. One theory 60suggests two reaction zones around the metal particle.In the inner zone, metal vapor and oxygen produceoxide vapor by a homogeneous reaction. A supersatura-tion of oxide vapor results in rapid nucleation and somecondensation of oxide on oxide. The heat of oxidation 65and of condensation isliberated so that the inner zone isthe hottest. Condensed oxide particles grow in size asthey are convected toward the outer zone, where the

4,106,411 4condensed oxide particles pile up to form the outerluminous edge of the flame.The novel weapon configuration of the present in-vention makes it possible to effectively use the frag-menting device to perforate fuel containers, to volatilizethe fuel by hydraulic ram action of fragments passinginto fuel at high velocity, and causing the particles ofburning pyrophoric material to violently ignite the vol-atilized fuel and the total fuel within the container.When the explosive is detonated, both the pyrophoricliner and the steel case will fragment and be drivenoutwardly from the munition at high velocity. Testshave confirmed that the pyrophoric material creates alarge plurality of burning particles exiting from thewarhead. These particles may be independent of thesteel fragments, or may be bonded to the steel fragmentsas a result of the detonation. High speed photographshave shown that a 0.050 inch sheet of zirconium alloybehind a layer of 30 grain steel fragments will createliterally thousands of burning zirconium alloy particleswhich saturate the target area, assuring ignition of fuelsvolatilized by the steel fragment portion of the war-heads, as well as the destruction of other materials bypenetration and/or perforation. Mechanical action ofsteel fragments coupled with high temperature burningpyrophoric particles thus results in violent ignition offuel in containers.It is therefore a primary object of this invention toprovide a highly effective and particularly devastatingincendiary fragmentation warhead.It is another object of this invention to provide anovel weapon configuration involving the layering ofpyrophoric and explosive material. .It is still another object of this invention to provide aweapon configuration involving alternate layers of ex-plosive, pyrophoric and fragmentation material,

amounting to an arrangement capable of creating cata-strophic fires.Other objects, features and advantages will be moreapparent from a study of the appended figures of draw-ing in which: .FIG. 1 is an illustrative sectional view of one form ofa novel incendiary fragmentation warhead in accor-dance with this invention, revealing concentric layeringof explosive, pyrophoric and fragmentation materials;FIG. 2 isa cross-sectional view of a bomblet incorpo-rating some of the teachings of the present inventionpertinent to the use of pyrophoric material;FIG. 3 is a top view illustrating the use of fragmentsin a weapon utilizing axial layering;FIG. 4 is a side elevational view related to FIG. 3, inwhich further details of axial layering are revealed,including the use of pyrophoric material; andFIG. 5 is a perspective view, partly in section, to55 reveal the use of a pyrophoric liner in a shaped chargetype weapon;FIG. 6 is a sectional view of an alternative embodi-ment of a novel incendiary fragmentation warhead inaccordance with this invention.DETAILED DESCRIPTION

Turning now to FIG. 1, it will be revealed that lay-ered device 10 has a center burster 11, around which arearrayed numerous fragments, such as rods 12 that aredeployed in alternate discrete cylindrical layers withexplosive layers 13. As will be evident from this figure,the rods 12 in this weapon embodiment are each in theconfiguration of a discrete rectangular solid, with the


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rods in each layer being arranged in several parallelrows to form a generally cylindrically-shaped configu-ration. In the present illustration, several rows of rodsare employed, but it isof course to be understood that alarger or smaller number may be employed if desired. 5Each such fragment layer amounts to an essentiallysolid structure, extending around the warhead. Therods 12 can be of low carbon steel and possess a lengthto thickness ratio of 1 to 1 to >30 to l.Itwill also be noted that some five layers of rods are 10employed in this illustrative embodiment, and betweeneach layer of rods a discrete layer of explosive 13 isdisposed. Detonation of the center burster 11is broughtabout by a conventional electric initiator 18, which intum causes the booster 19 to function and detonate the 15explosive center burster. The several explosive layersare detonated substantially simultaneously through ei-ther shock initiation through the rods, or through use ofan explosive disc 17 on one or both ends of the cylinder.At such time the rods are caused to be blown outwardly 20at substantial velocity, with an enhanced velocity pro-file and in a highly controlled pattern. The outermostlayer is typically surrounded by a casing 14, such as aFiberglas cover, although if the outermost layer offragments is to be created from a scored cylinder, the 25scored cylinder serves as the casing.Quite significantly, by the use of alternate layers ofrods and explosive all in direct contact, very effectivecoupling of explosive to fragments is brought about,with resultant high velocities and effective patterning 30that will enable an enemy target to be dealt a cripplingblow if detonation of our warhead takes place within areasonable range thereof. Spherical fragments, which,because of their relatively small contact area with theexplosive, may be desirable for minimizing fragment 35velocity while creating a velocity gradient, whereasfragments in the nature of rods or cubes are to be usedwhen velocity gradients are desirable and fragmentvelocities are to be maximized. .With regard to velocity gradient, such is achieved 40within the fragment pattern through the layering tech-nique. This velocity gradient spreads out the fragmentpattern in depth to increase the hit probability of thefragments. When the explosive central charge is initi-ated, it expands against the enclosing fragment layers, 45thus compressing the high explosive between the frag-ment layers and adding energy to the explosive. Whenthe explosive is then shock initiated, the fragments arepropelled at a higher velocity because of the greaterexplosive energy density. The outermost fragment layer 50has the highest velocity because it is surrounded byatmospheric pressure externally and detonation pres-sure internally, while the internal layers are surroundedby detonation pressure.As will be noted in FIG. 1, in accordance with the 55present invention we utilize at least one shell or sheet 15of pyrophoric material such as of zirconium alloy, dis-posed between an explosive layer and an adjacent frag-ment layer. In this illustrated embodiment, two shells 15are utilized, disposed between the two outermost explo- 60sive layers, and the respective fragment layers outboardof these explosive layers. Although other configura-tions are of course possible within the spirit of this in-vention, we have been most successful when using zir-conium tin in a thickness such as 0.050 inch, which 65material may be preformed so asto fit properly betweena given explosive layer and the fragments immediatelyoutboard of that explosive layer. In such instances, we

6prefer to use 30 grain steel fragments, but other frag-ment weights perform essentially as well in the war-head. Obviously, other weights may be used if the tar-get vulnerability so requires, and other nonpyrophoricfragment layers than steel may be employed.Upon detonation of the explosive layers in accor-dance with the techniques taught in copending applica-tion Ser. No. 249,458, the fragments are caused by thedetonation to move rapidly outwardly away from themunition at high velocity, with the pyrophoric liners 15of course being caused to break up into small pieces,which pieces also move outwardly from the munition athigh speed. Although in most instances the pyrophoricmaterial travels outwardly as discrete pieces, it is alsopossible In some instances for the nonpyrophoric frag-ments to in effect become partially "cladded" or"bonded" with the pyrophoric material, with the resultthat the heavy fragments actually are in such instancecapable of not only perforating the target but also caus-ing fire or an explosion therein.The usual circumstance is for the heavy steel frag-ments to travel outwardly and perforate the target,which of course may include fuel containers. In suchinstances, the hydraulic ram action of the fragmentspassing into the fuel at high velocity causes the fuel tovolatilize, which enhances the chance of this fuel ex-ploding in instances when glowing pyrophoric frag-ments arrive shortly after this perforation. High speedmotion pictures have revealed that literally thousandsof burning pyrophoric particles at roughly 35000 Ksaturate a target area subsequent to the detonation of anexplosive device in accordance with this invention, andthis assures the ignition of fuels volatilized by the actionof the heavy fragment portions of the warhead.Itis to be realized that we are not to be limited to theuse of five rows of fragments as shown in FIG. 1, nor

limited to two shells 15 of pyrophoric material, forobviously within the spirit of this invention these quan-tities could be changed. Tests have confirmed that theuse of dense, fragmentable material such as of steel inour warhead enables superior results to be obtained inmost instances. Although we may of course use onlyfragments of pyrophoric material on some occasions,because of the lesser density of such material and itstendency to break into small pieces, we have found that ,fragments of pyrophoric material simply do not perfo-rate the targets as well as do the heavier steel fragments,and thus by themselves do not serve as satisfactorily tocause the ignition of fuel or other combustibles con-tained in or associated with most targets.Tests have also shown that it is highly desirable toutilize an optimum ratio of ignited surface area relativeto the mass of the pyrophoric material. Without thisoptimum ratio, the heat generated by the burning sur-face area is insufficient to sustain burning because ofheat loss to the nonburning mass. For this reason, thepresent configurations provide for the breakup of thepyrophoric liner material and thus igniting a large num-ber of burning particles.Usable in lieu of or in addition to the zirconium mix-tures and alloys, the pyrophoric material may be se-lected from a group consisting of mixtures and alloys oftitanium, aluminum, magnesium, cesium, iron, copper,and pyrophoric combinations thereof.A typical layered device as depicted in FIG. 1mightfor example contain three layers of 30 grain steel frag-ments, having a total weight of 14pounds, containing 8pounds of fragments, 5 pounds of explosive, and 1

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7 4,106,411pound of zirconium tin or other pyrophoric material.This warhead would have an LID of approximately 2.Firing tests have demonstrated that when initiated si-multaneously at both ends, the fragment velocity willrange between 3,000 and 7,500 feet per second. It was 5also observed in the same tests that the pyrophoricmaterial in thousands of small particles was ejected witha velocity of approximately 1,000 to 7,500 feet per sec-ond. This warhead has been vividly demonstrated to setfuel fires repeatedly at distances of 75 feet. Thus we see 10the invention herein described adds to a standard typewarhead without pyrophoric material, the capability ofviolently igniting volatile fuels so that destruction byfire can be achieved in addition to the perforation of thetarget by fragments. 15Turning to FIG. 2, it will there be noted that we haveillustrated the cross-sectional appearance of a bomblet20 utilizing our novel teachings and configurations.Similar reference numerals to those used in FIG. 1willbe noted to have been employed in conjunction with the 20embodiments of FIG. 2 and figures following. The inte-rior of the bomblet is formed by high explosive 21 sur-rounded by a fragment layer 22 that in turn is sheathedby a tough plastic case or casing 24. This case is prefera- 25bly formed in two halves or hemispheres that have beencarefully formed so as to properly interfit as shown inFIG. 2. Preferably four sets of fins or wind vanes 27 aredisposed at spaced locations about the periphery of theweapon, at the juncture line, with one-half of each fin 30being disposed on each hemisphere. The fins are config-ured along one edge to catch the air as the bomblet isdropped and are smooth along the other edge, with theair-catching edges being aligned in a rotative sense sothat all the fins contribute to causing rotation of the 35bomblet in a common direction.Immediately inside the plastic case 24 is the fragmentarray 22, which may utilize either discrete fragments, orhemispherical members that have been "coined" orotherwise configured such that breakup of the fragment 40array into separate fragments occurs at such time as thehigh explosive 21 in the interior of the bomblet is causedto detonate. Preferably such detonation is broughtabout by action of a fuze 28 that causes the arming ofthe device after a number of revolutions have taken 45place, or a critical spin rate is achieved as a result of theaction of the fins 27. More particularly, this type ofweapon is typically released at altitude, and allowed tofall to the ground in enemy territory. In falling throughthe air, a very rapid spinup of the weapon is brought 50about by the action of the fins which thus arm the fuze,permitting detonation on impact. A booster 29 may beused adjacent the fuze 28 to assure the detonation of themain explosive 21.In accordance with this invention, we utilize a pyro- 55phoric liner 25 between the explosive material 21 andthe fragment array 22. This liner may be in two halvesor hemispheres that are configured so as to interfit be-tween the components 21 and 22, and is preferably ofzirconium tin, say 0.050 inch thick. 60As in the case of the device in accordance with FIG.1, upon the detonation of the explosive material in thebomblet, the pyrophoric material is caused to break up,and to accompany the metallic nonpyrophoric frag-ments as they fly outwardly at great speed from the 65device. The fragments of course serve to pentrate thetarget, and the pieces of pyrophoric material serve toignite explosive vapors in a very effective manner. A

8felt pad 26 may be placed between the two explosivehalves.Atypical bomblet as illustrated in FIG. 2 is generallyspherical, weighs approximately 2! pounds, and is ap-proximately 4 inches in diameter. This bomblet may becomprised of 6/10th of a pound of high explosive 21, ipound of pyrophoric material 25, and approximately I!pounds of steel fragments, with the pyrophoric materialand the fragments being disposed in a concentric array.The balance of the weight is of course made up by theplastic case and the fuze.From the standpoint of performance, upon firing ofthe fuze, the explosive charge is detonated, causing thefragments to be ejected at a velocity of about 4,200 feetper second. The pyrophoric material is also caused tobreak up in the detonation and is ejected over a velocityrange which will be from as little as 500 fps to as muchas 4,200 fps. Of course, these velocities depend upon theratio of weight of explosive material to the weight ofthe fragments and other structural material beingejected. Thus, we see that this small weapon typicallyejects a large number of 30 grain steel fragments at4,200 fps, and the pyrophoric material along with thefragments to literally saturate the target area with thou-sands of metallic particles burning at around 35000 K.This munition has been successfully demonstrated tostart highly destructive fuel fires in trucks, aircraft, fueltanks, and the like, whereas the same munition withoutthe pyrophoric material does not enjoy the benefit ofthe high probability of destruction by fire.FIGS. 3 and 4 represent a warhead sometimes re-ferred to as an axial projector warhead that has, forexample, four fragment layers 32, with each such layerbeing separated by an explosive layer 33, and with all ofthe foregoing disposed above a cylindrical explosivecharge 31, and contained within a metallic case 34 suchas of steel.. In accordance with this invention, we provide saytwo layers of pyrophoric material 35, such as of zirco-nium tin, with one of such layers disposed between theuppermost fragment layer and the adjacent explosivelayer, as best seen in FIG. 4, and the other pyrophoriclayer disposed between the next lower fragment layerand its respective explosive layer.Firing the detonator 38, by electrical energy or byfiring pin causes the booster 39 to detonate and transferthe detonation to the main charge 31. Since the detona-tion wave travels outward from the booster in all direc-tions and the fragments are nonuniformly orientedaround the booster, such fragments tend to be ejected atvery high velocity in a narrow pattern away from thebooster. Velocity gradient in the layers is as describedabove and in copending patent application Ser. No.249,458, and ignition of the pyrophoric material and itstarget interaction is as described hereinbefore.FIG. 5 represents another embodiment wherein pyro-phoric material is employed in accordance with thisinvention, being used here to enhance the effectivenessof a standard type shape charge munition. In thisweapon, the pyrophoric liner takes generally the formof a cone 45, which is placed adjacent to the usual cop-per cone 42 of a shape charge munition. The pyrophoricliner is thus placed between the copper cone and thehigh explosive material 41, in a somewhat similar man-ner to the previously described devices, wherein it isplaced between fragments and explosive material. Thepyrophoric conical liner may be in the form of a trun-cated cone fitting snugly to the copper cone or it may be


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4,106,411in the form of a cap over the entire copper cone. Theouter case 44 may be of aluminum or steel.Performance of this munition is as follows:Firing the detonator 48 causes detonation of thebooster 49 which then transfers the detonation to the 5explosive charge 41. As the detonating explosive chargeprogresses toward the shape charge cone 42, the cone iscaused to collapse in the normal shape charge mannerto form a jet which will perforate target materials.Through the addition of the pyrophoric liner 45 to the 10copper cone, we now not only perforate heavy targetmaterials but we cause burning pyrophoric material tobe introduced through the perforation brought about bythe copper cone, into the chambers such as tanks,trucks, APe's, etc., thereby causing a harsh environ- 15ment for personnel, or igniting gasoline, diesel fuels, orother materials which may be contained within thetarget. Ithas been demonstrated that a I! inch diametercopper cone shape charge without pyrophoric materialwill penetrate a I! inch steel plate but will not ignite a 20container of diesel fuel 4 feet behind the steel plate.With the addition of the pyrophoric material to such ashape charge device, we now enhance capability so thatthe diesel fuel under the same conditions is quickly 25ignited. As with the other embodiments of this inven-tion, we are not limited in either size or weight in muni-tions to which we may apply the pyrophoric material.As should now be apparent, we have provided inaccordance with this invention a novel incendiary 30weapon, comprising explosive and pyrophoric materialdisposed in conjunction with a metal layer, wherebyupon detonation of the explosive material, the pyro-phoric material and metal layer are caused to be co-dis-persed. Although the pyrophoric material is preferably 35directly adjacent to the metal layer, this is not a firmrequirement, and although the metal layer is preferablyof a relatively heavy, fragmentable, nonpyrophoricmetal, the metal layer may also be of a fragmentablepyrophoric material, or even be funnel shaped, and an 40ingredient of a shaped charge device.The explosive and pyrophoric material may be in theform of concentrically disposed layers, with the layerseither being generally cylindrically disposed or gener-ally spherically disposed, or alternatively, the layers 45may be substantially planar. In each of these instances,only a single layer of such materials may be used, oralternatively, multiple layers employed. In the eventmore than one layer of explosive is utilized, the arrange-ment is such that the explosive layers are detonated 50substantially simultaneously.End plates may be used for increasing the confine-ment of the explosive, thereby causing the fragmentsand pyrophoric material to be projected within a verynarrow beam spray. These end plates may be massive 55metallic plates, or alternatively may be made of explo-sive material. An initiator may be disposed in each ofthe plates of the latter type, which initiators are electri-cally interconnected so that they may be simultaneouslydetonated. 60An embodiment of this latter type is illustrated inFIG. 6, which involves an explosive end plate 57 ateach end of the weapon, as well as a plurality of layers.These are contiguous yet separate layers, and involveone or more fragment layers 52, one or more pyro- 65phoric layers 55, and one or more layers of explosivematerial 53, with all of these layers extending substan-tially continuously between the end plates 57, and

10around center burster 51. The outermost layer of aweapon of this type is surrounded by a casing 54.It is to be noted that each of the explosive end platesis provided with an electric initiator 58 connected to abooster 59, and each booster isin contact with the cen-ter burster 51. As previously mentioned, we prefer todetonate the detonators 58 substantially simultaneously,so that the detonation of the explosive material canproceed essentially uniformly.The pyrophoric material can, as previously ex-plained, either be zirconium, or else some mixture oralloy of zirconium with tin such as with the tin beingused in percentages from say 1% to 15%. Also, thepyrophoric material may be selected from a group ofmaterials evidencing pyrophorisity, consisting of zirco-nium, titanium, aluminum, magnesium, cesium, iron,copper, or some pyrophoric combination of any ofthese.It should now be obvious that we have provided anovel and highly effective Incendiary FragmentationWarhead, in which lethality to vehicles, stores and thelike is greatly enhanced over previous warheads, in thatthe inclusion of pyrophoric material causes immediateand catastrophic fire in containers of volatile fuels andcombustibles which in accordance with technology ofthe prior art, were usually only perforated by the frag-ments, thereby permitting field repair without destruc-tion by fire.We claim:1. A layered incendiary fragmentation device de-signed to project fragments in a highly controlled pat-tern, comprising at least two layers of fragmentablematerial, and at least two layers of explosive material,with a layer of explosive material being utilized for eachlayer of fragmentable material, at least one layer ofpyrophoric material disposed with said fragmentable

and explosive layers, said layers being adjacently dis-posed, yet separate and substantially continuous, ex-tending for a substantial portion of a major dimension ofthe device, and means for bringing about the detonationof said explosive layers substantially simultaneously soas to cause the outward projection of fragments andpyrophoric material.2. The layered fragmentation device as defined inclaim 1 in which said layers of explosive and fragment-able material are formed into a substantially cylindricalconfiguration, at each end of which is utilized an endplate for assuring a narrow beam spray angle.3. The layered fragmentation device as defined inclaim 2 in which said end plates are of relatively mas-

sive metallic construction.4. The layered fragmentation device as defined inclaim 1 in which said fragments are in the form of dis-crete rectangular solids.5. The layered fragmentation device as defined inclaim 1 in which said fragments are in the form of rect-angular solids formed by coining into metallic plate.6. The layered configuration as defined in claim 1 inwhich said layers are concentric, being disposed in agenerally cylindrical arrangement.7. The layered configuration as defined in claim 1 inwhich said layers are concentric, being disposed in agenerally spherical arrangement.S. The layered fragmentation device as defined inclaim 1 in which said layers are parallel layers orientedalong the axis of a cylinder.9. A layered incendiary fragmentation device de-signed to project fragments in a highly controlled pat-


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11tern, comprising at least one layer of fragmentable ma-terial, with a layer of explosive utilized for each layer offragmentable material, at least one layer of pyrophoricmaterial disposed with said fragmentable and explosivelayers, and means for bringing about the detonation ofsaid explosive layers substantially simultaneously so asto cause the outward projection of fragments and pyro-phoric material, said layers of explosive and fragment-able material being formed into a substantially cylindri-cal configuration, at each end ofwhich isutilized an endplate for assuring a narrow beam spray angle, said endplates being of explosive material, each with its owninitiator.10. A layered warhead for projecting a multitude of 15

fragments in a controlled pattern comprising inter-spersed layers of fragmentable material, explosive, andpyrophoric material, and means for detonating saidexplosive material so as to bring about the outward 20projection of fragments and pyrophoric material, saidlayered warhead utilizing a plurality of layers of eachmaterial, with the layers of explosive being detonatedsubstantially simultaneously.11. The layered warhead as defined in claim 10 in 25

which saidpyrophoric material isselected from a groupconsisting of zirconium mixtures and alloys.12. The layered warhead as defined in claim 10 in

which said pyrophoric material is a material selected 30from the group consisting of zirconium, titanium, alumi-

4,106,411 12num, magnesium, cesium, iron, copper, as well as cer-tain pyrophoric combinations of any of these.13. The warhead as defined in claim 10 in which

pyrophoric material is directly adjacent to a layer of5 fragmentable material.

14. The warhead as defined in claim 10 wherein saidfragmentable layer is of a relatively heavy, fragment-able, nonpyrophoric metal.15. The warhead as defined in claim 10 wherein said10 fragmentable layer is of pyrophoric material.16. The warhead as defined in claim 10 wherein said

explosive and pyrophoric materials are generally in theform of concentrically disposed layers.17. The warhead as defined in claim 16 in which alayer of fragments is generally concentric along with

the layers of explosive and pyrophoric material.18. The warhead as defined in claim 17 in which saidlayers are concentric in that they are generally cylindri-cally disposed.19. The warhead as defined in claim 10 in which the

explosive and pyrophoric materials are in the form ofsubstantially planar layers.20. A layered warhead for projecting a multitude offragments in a controlled pattern comprising inter-

spersed layers of fragmentable material, explosive, andpyrophoric material, and means for detonating saidexplosive material so as to bring about the outwardprojection of fragments and pyrophoric material, saidpyrophoric material being principally zirconium, butwith 1% to 15% tin by weight added.* * * * *

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Documents

Charles A. Borcher et al- Incendiary Fragmentation Warhead