Aug. 13, 1963
`T.C.POULTER
`SHAPED CHARGE AND METHOD OF FIRING THE SAME
`Filed Jan. 14, 1959
`
`2 Sheets-Sheet l
`
`5
`
`4
`
`Th'OMRS C. POULTE/2,
`INVENTOR.
`
`RTTOl:?#EYS
`
`DynaEnergetics Europe GmbH
`Ex. 1008
`Page 1 of 15
`
`

`

`Aug. 13, 1963
`T.C.POULTER
`SHAPED CHARGE AND METHOD OF FIRING THE SAME
`Filed Jan. 14, 1959
`
`3,100,445
`
`2 Sheets-Sheet 2
`
`Fig.3
`
`Fig. 4
`
`JI
`
`31'
`
`INVENTOR
`Th om as C. Poulter
`
`BY
`
`DynaEnergetics Europe GmbH
`Ex. 1008
`Page 2 of 15
`
`

`

`United States Patent Office
`
`3,100,445
`Patented Aug. 13, 1963
`
`1
`
`3,100,445
`SHAPED CHARGE AND METHOD OF
`FIRING THE SAME
`Thomas C. Poulter, Palo Alto, Cam'., assignor of one-half
`to Borg-Warner Corporation, Chicago, Ill., a corpora(cid:173)
`tion of Illinois, and one-hail to Haml:mrton Company, a
`corporation of Delaware
`Filed Jan. 14, 1959, Ser. No. 786,888
`16 Ciaims. (Cl. 102,-24)
`
`5
`
`2
`There is, however, not a single one of these variables
`which ·can be considered to be an independent variable.
`On the contrary, the changing of any one of them changes
`an unknown number of the others, usually by •an . unde-
`termined amount, so that without a rather clear under(cid:173)
`standing of the detonation process ,and the possible mecha(cid:173)
`nisms of jet formation, it is impossible to predict the per(cid:173)
`It is not
`formance. of a new design of shaped ·charge.
`surprising, therefore, that most of the development work
`10 to date has. been conducted on a cut-and-try basis with
`usually very discouraging and inconclusive results.
`To develop a set of rules for the design of ,an effective
`lined shaped charge based on so. many interdependent
`variables would, of course, be impossible. A .fundamen(cid:173)
`tal .study of the detonation process and the mechanism
`whereby a metal liner is given its velocity when ,an ex-
`plosive in contact with it is detonated, was therefore un(cid:173)
`In. this manner a few '1east common denomi(cid:173)
`dertaken.
`nators have been obtained which provide some useful de(cid:173)
`sign parameters.
`From this it has been ,possible to evaluate tJhe relations
`between the shape of the detonation front and the de(cid:173)
`tonation velocity, and the relation between the detona(cid:173)
`tion velocity and the detonation pressure. Still .fur(cid:173)
`ther studies of the detonation process permit an evalua(cid:173)
`tion of the factors controlling the duration of the pressure
`associated with the detonation process. This pressure
`and its duration provide a means of determining the im(cid:173)
`pulse imparted to ~he :liner. This, coupled with the de(cid:173)
`sign of the liner, provides a means for d,etermining the
`direction and velocity of the motion imparted to the vari-
`mis elements of the Uner. Thus, it has 1been possible to
`better understand the .complexity of jet formation and
`its control, which has resulted in the invention and de(cid:173)
`velopment of a basic design of a shaped charge having
`vastly improved performance characteristics.
`In the usual cut-and-try procedure there has been but
`little, if any, basic information on which to arrive at a
`modification of the construction of a charge, nor was
`there any basis for knowing whether the change in per(cid:173)
`formance was a result of the variable which was inten-
`tionally changed or whether one of the dependent vari(cid:173)
`ables dominated any change there may have been in
`performance. It was therefore a matter of changing an
`unknown number of variables by an indeterminate
`amount to produce an accumulative effect that may be
`positive or negative.
`From a knowledge of jet penetration .it is possible to
`specify certain desirable properties of a jet and, with this
`as a basis, to establish many of the requirements for
`a jet-producing mechanism and through that to an effec-
`tive charge design.
`For good performance, the material in the jet should
`be concentrated in to a compact, straight line of high
`velocity, high density material. There should be a maxi(cid:173)
`mum range in material velocity in the jet consistent with
`its having the highest attainable material velocity at
`the forward end of the jet, and decreasing at a reason(cid:173)
`ably uniform rate over the len.gth of the jet to the mini(cid:173)
`mum velocity that will produce. effective penetration.
`The necessity for this spread jn jet velocity is to permit
`each element of the jet to complete its penetration of
`the target before the. following element strikes the target.
`Other things · being equal, an increase in velocity of
`the forward end of the jet will increase the penetration .
`of the jet. This is a very important factor since the
`percentage . in penetration greatly exceeds the increase in
`jet velocity necessary to produce it.
`It is entirely possible that an increase in the average
`velocity of the material in the jet may reduce. the pene(cid:173)
`tration if· that increase in velocity occurs primarily at the
`after-portion of the jet. In such a case each element of
`
`This application is a continuation-in-part of my co(cid:173)
`pending application Serial No. 439,564, filed June 28,
`1954, for "Shaped Charge," now abandoned.
`This invention relates. generally to e:x;plosive devices
`and is directed ,particularly to improvement-s in shaped 15
`charges. The term "shaped charge," as used herein and
`as generally employed in the art of explosives, designates
`a charge of high explosive having a cavity in its forward
`end which is lined with a layer of inert material. The liner
`may be metallic, such as copper, steel, cast iron, alumi- 20
`num or lead, or may be of glass or other non-metallic
`materiaL The cavity and .Jiner are usually conical, hemi(cid:173)
`spherical, or conforming to other surfaces of revolution
`about the longitudinal axis of the charge. Provision is
`made for initiating detonation of the charge on its axis 25
`at its rearward end.
`Upon detonation of a conventional shaped charge, a
`detonation front advances through the charge in the di(cid:173)
`rection of its major axis and impinges on the liner. By
`virtue of the extremely high particle velocities and pres- 30
`sures prevailing in the detonation front, the major por(cid:173)
`tion of the .Jiner is dynamically extruded in a pencil(cid:173)
`like jet along the charge axis at extremely high velocity.
`Because of the great penetrating power of this . high(cid:173)
`velocity jet, many ,applications, both military and in- 35
`dustrial, of the shaped charge have been developed. An
`outstanding example of an industrial application is in
`the perforation of well casing and subtel'fanean forma(cid:173)
`tions sur;rounding oil, gas and water wells.
`Since its original development •as a military weapon, 40
`the ,shaped charge has been the subject of extensive re(cid:173)
`search, both analytical and experimental. For the most
`part, experimental research has been confined to cut(cid:173)
`and-try procedures, and analytical research has been con(cid:173)
`fined to the study of experimental data and the devel- 45
`opment of theories of the mechanism .of jet formation
`which are consistent with and attempt to explain such
`data. Many conflicting and ,erroneous theories and ex(cid:173)
`planations of the mechanism of jet formation have been
`advanced.
`'!,he mechanism of jet formation from a lined hollow
`charge is very complex, and there is probably no single
`explanation that will elfplain all of • -the experimental
`results to the exclusion of all other proposed mecha(cid:173)
`nisms. The most widely publicized mechanism is re- 55
`ferred to as the hydrodynamic flow mechanism (Journal
`of Applied Physics, 19, 563, 1948). There are extensive
`elfperimental results to substantiate at least two other
`mechanisms (plastic• deformation and •brittle .fracture)
`so that when one considers that it is ,possible. to have the 60
`formation of the jet follow any one of three mechanisrns,
`plus all possible combinations of these, it is not surpris-
`ing that much confusion has resulted.
`The problem is further complicated tby the fact that
`there are no independent variables.
`It is generally recognized that the size, shape and
`composition and thickness of •case surrounding it, the
`shape, thickness, and composition of the liner, stand-off
`distance, method of detonation of the charge, shaping of
`the detonation front, and the angle that the detonation 70
`front makes with the surface of the liner me all known
`to materially affect the performance of shaped charges.
`
`50
`
`65
`
`DynaEnergetics Europe GmbH
`Ex. 1008
`Page 3 of 15
`
`

`

`3,100,445
`
`3
`the jet would be striking the target before the preceding
`element had completed its penetration, and the piling-up
`effect may cause a large decrease in depth of penetration
`of as much as 7 5 percent, with only a minor increase in
`hole diameter. The extent to which the after-end of the 5
`jet can have its velocity increased is determined by the
`ability of each preceding element to complete its pene(cid:173)
`In order to obtain maximum penetration, the
`tration.
`forward end of the jet should have the maximum obtain(cid:173)
`able velocity. and each successive element should have 10
`the maximum velocity consistent with permitting the pre(cid:173)
`ceding element to complete its maximum penetration of
`the target before the succeeding element strikes.
`With such specifications set up for an effective jet, it
`then becomes a matter of selecting the mechanism of jet 15
`formation and the charge design which will best lend it(cid:173)
`self to the production of such a jet.
`While it is possible to design a lined shaped charge
`operating by a mechanism· of jet formation whereby the
`high velocity forward end of the jet originates from the 20
`base of the liner, such a design does not permit taking
`advantage certain novel features of the present invention.
`From experimentation in which a conventional charge
`was modified in such manner as to increase the velocity
`of the after end of the jet by only a small amount, it 25
`was found that an appreciable decrease in penetration
`resulted. From this it was obvious that if any appreci(cid:173)
`able increase in penetration was to be accomplished, it
`would have to be through an increase in the velocity of
`the forward end of the jet. This meant devising tech- 30
`niques for increasing the velocity imparted to the metal
`of the apex of the liner.
`Numerous attempts have been made to do this by
`means of peripheral detonation of the charge with gen(cid:173)
`erally unsatisfactory results, either because of the re- 35
`quirement of an excessive quantity of explosive or, if
`the quantity of explosive were reduced, because the meet(cid:173)
`ing of the converging detonation front over the apex of
`the liner would blast a hole through the liner along its
`axis· and disrupt its normal jet formation.
`It is my dis- 40
`covery, however, that if the inert barrier by which pe(cid:173)
`ripheral detonation is · generated is so constructed as to
`permit a delayed detonation to occur through its central
`portion, then instead of the converging peripheral detona(cid:173)
`tion front meeting at the center and blasting a hole 45
`through the apex of the liner, it will meet the delayed ex(cid:173)
`panding detonation front in a circular area generally
`surrounding the apex of the liner and a generally spheri-
`cal . concave detonation front is developed which en(cid:173)
`velopes the apex of the liner in a pressure manyfold the 50
`sum of the pressures in the two detonation fronts.
`Thus the forward end of the jet acquires a velocity far
`in excess of that produced by the conventional expanding
`spherical detonation front produced by single-point
`initiation.
`Due to the more nearly normal angle of approach of
`the peripherally generated detonation front over the cen(cid:173)
`tral portion of the liner, the velocity over the central
`portion of the jet will be correspondingly increased.
`This will therefore permit an increase in the after portion 60
`of the jet, and hence the ratio of explosive to metal
`around the base of the liner can be increased over and
`above that which is permissible with the single-point(cid:173)
`initiated · charge.
`I have discovered that my invention provides another 65
`very important advantage in that merely by a small shift
`in position of the apex of the liner closer to or farther
`away from the inert barrier, the diameter of the hole
`produced by the jet from this charge can be varied over
`a several-fold range, the maximum size hole being pro- 70
`duced with the liner at the proper distance to cause
`the detonation front to conform in curvature to that of
`the liner apex.
`A general object of the invention is therefore to pro(cid:173)
`vide an improved shaped charge the performance of 75
`
`4
`which is characterized by more effective utilization of
`the energy available in the explosive than has heretofore
`been possible.
`Another object of the invention is to provide an im(cid:173)
`proved shaped charge which, upon detonation, produces
`a jet of higher overall velocity than has heretofore been
`attained.
`A further object of the invention is to provide an im(cid:173)
`proved shaped charge which not only produces a higher
`:velocity jet than heretofore, but which is so designed
`that the velocity of successive elements of the jet is dis-
`tributed over a range of velocities sufficiently ,wide to per(cid:173)
`mit each element of the jet to most effectively expend its
`,energy in effecting penetration of the target before the
`next succeeding element strikes the target.
`Another object of the invention is to provide a shaped
`charge wherein the shape of the detonation front is altered
`in a predetermined manner by a body of inert material
`embedded in the explosive charge.
`Yet another object of the invention is to provide a
`shaped charge wherein the size and shape of the hole
`produced in a target may be predetermined solely by
`the relative positions of certain of the charge components.
`Another object of the invention is to provide a shaped
`charge incorporating a body of inert materi3!l embedded
`in the explosive charge, and wherein the size and shape
`of the hole produced in a target may be varied in pre(cid:173)
`determined manner by varying the distance between the
`inert body and the liner.
`A still further object of ,the invention is to provide
`a shaped charge wherein, upon detonation, a detonation
`front is developed in the explosive which is characterized
`by a central concave front and a peripheral or annular
`convex front.
`Still another object of the invention is to provide a
`shaped charge incorporating means for developing, upon
`detonation, a central detonation front and an initially
`separate and distinct peripheral detonation front, the
`time and space relation of the two fronts being such that
`they merge into a composite front having a concave cen(cid:173)
`tral portion characterized by extremely high order pres-
`sure and particle velocity.
`Yet another object of the invention is to provide
`a shaped charge wherein the optimum stand-off distance
`from the base of the liner to the target is substantially
`less than with charges heretofore developed.
`Still another object of the invention is to provide a
`shaped charge wherein the mechanism of jet formation
`is such that the degree of interdependence of the various
`parameters of the charge is substantially less than in
`charges heretofore developed.
`A still further object of the invention is to provide a
`shaped charge wherein the usual slug or "carrot" may, if
`desired, be substantially eliminated.
`55 Another object of the invention is to provide a shaped
`charge incorporating a body of explosively active sub(cid:173)
`stance embedded in the explosive charge as a means for
`providing a peripheral high-order detonation and a central
`low~order detonation.
`Yet another object of the invention is to provide a
`method of firing an explosive charge, particularly a
`shaped charge.
`Generally speaking, based on my studies of detonation
`phenomena, I have discovered and developed an arrange(cid:173)
`ment and procedure or technique whereby a detonation
`front of abnormally high pressure and velocity can be
`developed in the explosive charge rearwardly of the liner,
`with the central portion of the front being concave and
`conforming in shape very closely to that of the apex por(cid:173)
`tion of the liner. This is accomplished by developing a
`combined peripheral detonation front and central detona-
`tion front in predetermined time and space relation to
`each other and to the apex portion of the liner. The
`merging of these detonation fronts produces a composite
`front in which the pressure and the detonation velocity
`
`DynaEnergetics Europe GmbH
`Ex. 1008
`Page 4 of 15
`
`

`

`3,100,445
`
`5
`greatly exceed the sum of the individual pressures and
`velocities of the two fronts. Not only is it possible to
`"tailor" the shape of this composite front to conform
`substantially to liner apices of dh'ferent curvatures, but
`it is also possible with my improved charge design to pro- 5
`duce a wide range of target hole sizes with the same
`liner shape, by the simple expedient of slight changes in
`the position of the liner, involving merely a slight change
`in loading technique.
`,In general, the invention includes a method of firing 10
`a detonating explosive charge having in a face thereof an
`outwardly ;opening cavity ,the walls of which are defined
`by a surface of revolution about an axis, the cavity having
`sidewalls converging to the rear, the charge being ,capable
`of sustaining Jaw-order detonation and high-order detona- 15
`tion ,therein, and the cavity being lined with a 'liner,
`which method includes ,the following steps: initiating a
`low-order detonation in said charge in a zone coaxial
`with the axis and spaced inwardly from the inner end
`of the cavity; and initiating a ihigh-mder detonation in 20
`and throughout an annular zone in ,the charge, which
`zone is located in a plane. normal to the axis, is spaced
`inwal'dly from the inne,r end of ,the cavity, is positioned
`symmetrically about the ,axis, and is disposed around
`,the zone of initiation of low-order detonation, .the initia- 25
`,tion of the high0order detonation being performed in
`predetermined time relation to the initiation of the low(cid:173)
`orde,r detonation to cause the detonation waves resulting
`from ,the initiations to merge in a zone focated in the
`charge between ,the zones of initiation and the cavity to 30
`form a composite detonation wave that attacks the Hner.
`The manner in which ,the foregoing and other .objects
`may be accomplished will :become apparent from the
`following detailed description of a 1presently preferred
`embodiment of ,the invention, reference being had to the 35
`accompanying drawings wherein:
`FIGURE 1 is a central :longitudinal sectional view of a
`shaped charge embodying the invention;
`FIGURE 2 is an enlarged view similar to FIGURE 1,
`illustrating successive stages of propagation of the indi- 40
`v,idual detonation :fronts, their merger into a single com(cid:173)
`posite front, the progressive change in shape of the com(cid:173)
`posite front and its impingement on the apex :portion of
`the liner;
`FIGURE 3 is a fongitudina1 axial sectional. view of 45
`another embodiment of a shaped charge in accordance
`with. the invention; and
`FIGURE 4 is a longitudinal axial sectional view of
`a third form of shaped charge embodying the invention.
`Referring to FIGURE 1, a ,charge ,case 1 is herein 50
`shown as cylindrical but may be of any other desired
`shape symmetrical with respect to ,the charge axis, and
`is . preferably of metal such as steel, cast iron or alu(cid:173)
`minum but may if desired be of non-metallic material
`such as plastic. A liner 2 of copper or other suitable ma- 55
`terial is mounted in the case in a conventional manner.
`As shown, the apex portion 3 ,of ,the liner is rounded and
`the side portions of the liner are of gradually decreasing
`It will be understood, however, that ,the
`curvature.
`&pecific shape of the liner does not constitute a significant 60
`aspect of · the instant invention and various other shapes
`may be employed .ff desired.
`Rearwardly of the liner .the case 1 is filled with an
`explosive 4 having a hfgh detonation raite, such as TNT,
`Cyclotal, etc. Embedded in the explosive 4 adjacent the 65
`rear wall of the case is a barrier 5 of inert material such
`as steel or other .metals or non-metals. The barrier 5 is
`disposed transversely of the charge and is symmetrical
`and coaxial with ,the case and liner. As . shown the
`barrier 5 is of uniform thickness and is preferably in 70
`the form of a segment of a sphere, although other shapes
`which are symmetrical with the axis of the charge may
`:be employed, such as conical, paraboloidal, elli!psoidal,
`or a flat disc. The diameter or transverse dimension
`of the barrier is less •than the internal diameter of the 75
`
`6
`case 1 ,thereby providing an annulus 6 of explosive sur(cid:173)
`rounding the periphery of the · barrier and joining the
`:bodies of explosive at the forward and rearward sides of
`In order to provide a layer ,Df. explosive 7.
`,the :barnier.
`of uniform thickness •between the barrier and the rear
`wall 8 of the case 1, ,the :latter is prderably also in the
`form of a segment of a. sphere or of other shape con(cid:173)
`forming to ,that of the barrier.
`A tubular socket 9 projects from the rear wall of ,the
`case 1 in coaxial relation thereto, and is perforated
`transversely at 10 to receive a leng,th of Primacord 1l or
`other detonating .fuse. A booster pellet :U is seated in
`the socket 9 between the .Primacord :1.1 .and the rear wall
`of. the case, and is in direct contact with ,the explosive
`7 .through an. opening 13 in the !fear wall 8, it being
`understood ,that the explosive also fills ,the opening 13.
`The opening 13 should ·· be small enough to assure con(cid:173)
`centricity of the detonation front.
`It will be apparent that detonation of the Primacord
`11 will detonate the booster :1.2, which in turn initiates
`detonation of the explosive 7 at the opening 13. Re(cid:173)
`ferring to FIGUR,E 2, ,the detonation front developed at
`tlle · opening •13
`initially ,expands .spherically until it
`strikes the rear wall of the. barrier 5, whereupon it is
`converted into a radially expanding circular foont pro(cid:173)
`gressing through the -layer 7 of ,explosive, successh,e po(cid:173)
`sitions of the front being indicated at 15, 15a and 1'5b.
`Upon reaching the periphery of the barrier, ,the detona~
`tion front rprogresses ,ther,earound, and forwardly ,through
`the annulus 6 of explosive. As it passes the fo.rward
`peripheral edge of the barrier and enters ilie main body
`of explosive 4 it is :free to expand both forwardly and
`radially inwardly toward the ax,is of the charge. Hence,
`the forward and inward por,tion of the front assumes the
`form of a portion of the surface o.f a torus, as indicated
`by ,the corresponding pairs of ,arcuate dotted lines 16, 16a
`and 16b.
`Meanwhile the detonation of the explosive in contact
`with the rear surface of the barrier 5 has generated a shock
`pulse in thematerial of the barrier. This shock pulse, ini(cid:173)
`tiated at a point on the axis of the charge, progresses for(cid:173)
`wardly through the barrier as indicated at 17, 17a, 17b
`and 17c, •to the forward, concave surface thereof. Also
`as the detonation front indicated at 15, 15a and 15b ex(cid:173)
`pands through the explosive layer 7, it rolls along the rear
`surface of the barrier 5 and generates a radially progress(cid:173)
`ing series of shock pulses in the barrier, which progress
`forwardly through the banier.
`Whether or not the explosive in contact with the for(cid:173)
`ward surface of · the barrier ·5 will be detonated by the
`shock pulse transmitted through the barrier, and whether
`the detonation is low-order or high-order, depends, gen(cid:173)
`erally speaking, on the intensity of the shock pulse as it
`reaches the forward surface of the harrier and on the
`sensitivity of the explosive in contact therewith. The in(cid:173)
`tensity of the shock pulse after it passes through the bra(cid:173)
`rier depends on the material of the barrier, the thickness
`of the central por,tion thereof, and the thickness of the
`central portion of the layer 7 ;of explosive which generates
`the shock pulse,.
`By way of example, in tests wherein the explosive used
`was waxed "RDX," a military form of Cyclonite
`(CH2 ·N·N02 )s
`it has been determined that with a ba:rrier 5 of steel and
`with a ½6 inch thick layer 7 of explosive which is deto(cid:173)
`nated by a booster such as the pellet 12, if the thickness
`of the central pO!!tion of ,the barrier is %6 inch or greater
`the explosive in contact with the forwar,d surface will not
`be detonated by the shock pulse. -If the central portion of
`,the ,barrier is ½o inch to 1/s inch in thickness, the shock
`pulse .transmitted through it will initiate low-order deto(cid:173)
`nation of the explosive at the forward side of the ,barrier.
`If the central portion of the barrier is substantially less
`than ½o inch in thickness the shock pulse will initiate high-
`
`DynaEnergetics Europe GmbH
`Ex. 1008
`Page 5 of 15
`
`

`

`3,100,445
`
`order de,tonation of the explosive at the forward side
`thereof.
`On the other hand, from ,tests with .charges in which the
`type of explosive, the material and thickness of the barrier
`5, and the thickness ,of the layer 7 of eJ<plosive were iden(cid:173)
`ticalwith those referred to in the preceding paragraph, but
`in which the booster pellet 7 was omitted and detonation
`was initiated directly by Primacord, it was found that the
`optimum barrier thickness from the standpoint of depth
`of penetration was 0.069 inch, as compared ,to 0.10 to
`0.125 in the previously mentioned test results.
`'This may
`be explained by the fact that the booster pellet 12 consti(cid:173)
`tutes in effect an additional thickness of explosive behind
`the . central portion of the barrier. This points up the
`important influence which the thickness of the explosive
`exerts on the initial velocity of the shock pulse developed
`in the barnier.
`It is .thus apparent that by the selection of a barrier of
`,appropriate material and thickness, or by varying the ef(cid:173)
`fective thickness of the explosive behind the barrier, any
`one of three distinctly different detonation front condi(cid:173)
`tions may be produced in the explosive forwardly of the
`ba,rrier {a) a converging, high-order peripheral detona(cid:173)
`tion front only; or (b) a converging, high-order peripheral
`detonation front and a delayed, expending, low-order cen(cid:173)
`tral detonation front; or (c) a converging, high-order pe(cid:173)
`ripheral detonation front and a delayed, expanding, high(cid:173)
`order central detonation front.
`The respective characteristics of the two distinct types
`of detonation known as ''high-order" and "low-order"
`detonation are well known to those familiar with explo(cid:173)
`sives and have been delineated in many pub1ications deal-
`ing with explosives. A well-known example of such pub(cid:173)
`lioations is "Detonation in Condensed Explosives," by
`J. Taylor, Oxford Press, 1952, London, England. An ex- 35
`planation and cliscussion herein of those phenomena is
`therefore not,deemed necessary.
`As has been pointed out previously, ,a converging pe(cid:173)
`ripheral detonation front alone ( condition (a) above) is
`not conducive to proper jet formation. The apex of the
`liner is not the first portion of the liner to be given a veloc(cid:173)
`,Inste,ad,
`ity as is the case wdth single-point detonation.
`the detonation front first contacts a ring of material far(cid:173)
`ther down on the liner. Since this first contact is normal
`to the surface, that portion of the liner will be given a high
`velocity. As the detonation front rolls ,along the surface
`of the . Hner in the clirection of the apex, the angle of ap(cid:173)
`proach becomes less than 90° and the material is given a
`lower velocity than the portion of the liner first contacted.
`This lower-velocity material is projected into the region
`where the jet is being formed and disturbs the jet forma(cid:173)
`tion. However, as the detonation front reaches the apex,
`it converges and meets a,t a p'oint. . Such a meeting of deto(cid:173)
`nation fronts produces, at that point, ,a pressure estimated
`to be in excess of fifty million p.s.i. With such a pressure
`at a point, •a jet of extremely high-velocity material is pro(cid:173)
`jected into the zone where the jet proper is being formed,
`,and since the lower velocity material has already been
`p11ojected into that zone, the collision of ,the extremely
`high-velocity material with it tends to disrupt the process
`of jet formation. Although the process of jet formation
`proceeds in ,an ovderly manner in the lower portion of ,the
`liner, the disturbance in the formation of the apex of the
`jet has been such as to prevent its superior performance.
`This ,interference can be prevented to some extent if the
`distance between the zone of peripheral initiation ,and clle
`apex of the liner is increased, which accounts for the be(cid:173)
`lief .that in order for peripheral detonation to function
`properly, an excessive amount of explosive is required.
`I have discovered that if ,conditions are such as to pro(cid:173)
`duce a high-order central detonation front and a high(cid:173)
`order peripheral detonation front, the ·collision 'Of two such
`high"order fronts produces ,a sharply defined annular zone
`of extremely high pressure.
`If the ,liner be located close
`enough ,to the barrier to subject ,any portion of ,the liner
`
`8
`to the effect ·of this sharply defined, annular high-pressure
`zone, ,there results a marked decrease in the effectiveness
`of the jet. This is attributed to the sharp boundary0crntting
`effect of the annular high-pressure zone on ,the liner, pro-
`5 ducing a sharp discontinuity in the velocity gradient of
`the jet. On the other hand, if· rthe liner be located far
`enough away from the bar.rier to avoid the sharp bound(cid:173)
`ary-cutting effect of the high-order detonation ·collision
`zone, the performance of ,the charge is strikingly similar
`10 to that of a conventional charge having single-point initia(cid:173)
`tion. This indioates . tha,t the axial spacing between the
`liner and the barrier is so great that the intially centrally
`concave detonation front has been ,converted to ,a conven(cid:173)
`tional convex front before it reaches the ,apex of the liner,
`15 and hence that the advantageous effect of the barrier has
`It therefore appears• that less advanta(cid:173)
`been dissipated.
`geous results are obtained when the parameters of the com(cid:173)
`ponents of a barrier-type charge are . such ,as to produce
`central and peripheral detona,tion fronts which are both
`20 of highaorder.
`One of .the most imporitant a,nd most significant aspects
`of my invention is my discovery that with the proper
`relationship between ,the type of eX:plosive, the barrier ma(cid:173)
`terial and thickness, and the thickness of explosive behind
`25 the central portion of the barrier to develop a low-order
`,central detonation front and a high-order peripheral det(cid:173)
`onation front at the forward side of the barrier, marked
`and unprecedented improvements in charge performance
`from many standpoints, as well as several other outstand-
`30 ing advantages, can be achieved. These improvements
`and ,advantages, which will be explained more in detail
`hereinafter, are briefly as follows:
`(a) Greatly increased depth ,of target penetration and
`volume of target hole for ,a given ,amount of explosive;
`(b) Wide variation in the cross-sectional area of the
`target hole by varying only the amount ,of explosive while
`maintaining all other components the same;
`(c) Substantial reduction in the number of parameters
`which effect performance, making possible the develop-
`40 ment of a simple equation defining the relationship of the
`significant parametern;
`(d) Substantial. reduction in optimum stand-off dis(cid:173)
`tance (from base of liner to target);
`(e) Substantial elimination of the usual slug or "car-
`45 rot."
`The mechanism of development of the initially separate,
`low-order ,central detonation front and high-order periph(cid:173)
`eral detonation front, their merger into a composite
`front having a concave central region, and the progressive
`50 change ~n the contour of this front, will be made clear by
`reference ,to FIGURE 2 of the dr,awing. AB shown there(cid:173)
`in, the dot-and-dash lines 18, 18a ,and 18b ,represent suc