Sub Projectile or Flechette Launch System

The present invention relates to dart-like projectiles such as flechettes and more particularly pertains to a physical structure for explosively, radially launching a plurality of flechettes employing a driver generator for propagating a radially directed plane wave.

In the field of launching flechettes, it has been the general practice to employ pneumatic, mechanical and explosive drivers for imparting a high velocity to the projectiles. However, such launch systems have proved unsatisfactory in that the mechanical and pneumatic systems could not provide a sufficiently high launch velocity to make the flechette useful for the purpose intended. On the other hand, explosive launching from conventional ammunition items resulted in severe and intolerable damage to the flechette and fin assembly. Additionally, such form of launching necessitates side or fin first launch for economical packaging in round carriers. The present invention overcomes these problems and solves a long existing need.

The general purpose of this invention is to provide an explosive flechette launch system that has all the advantages of similarly employed prior art devices and has none of the above described limitations and disadvantages. To attain this, the present invention provides a unique structural arrangement wherein the flechettes are releasably supported and sandwiched between pairs of disc plates. A central coaxial radial, plane wave, explosive driver is disposed axially of said plates and flechettes and extends between the outer plates. The flechettes are oriented radially or laterally and when radially directed are provided with a fin assembly slidingly and coaxially mounted on the body thereof with a rear enlarged portion for firmly holding said fin assembly after launch and for providing a surface area upon which the propagating wave energy will act.

An object of the present invention is to provide an efficient, reliable, economically feasible, explosive launch system for sub projectiles, such as flechettes without damage thereto.

Another object is to provide a flechette explosive launch system wherein the flechettes are radially launched when initially oriented either lateral to or pointed in the direction of flight.

Still another object is to provide a novel flechette which may be radially launched in the direction of flight at a maximum velocity without fin damage.

A further object is to provide a high energy radial plane wave explosive generator capable of launching a plurality of radially support flechettes.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective of an embodiment made in accordance with the principle of the instant invention;

FIG. 2 is a perspective of the embodiment of FIG. 1 immediately subsequent to launch;

FIG. 3 is a cross-section of the flechette with the pusher piston;

FIG. 4 is a perspective of another embodiment made in accordance with the principle of this invention and, also a cross-sectional view of a radial plane wave explosive generator; and

FIG. 5 is a cross-sectional view of an improved flechette.

In the illustrated embodiment of FIG. 1 the flechette explosive launcher 10 includes a central circular cylindrical driver explosive 11 about which are longitudinally disposed an upper 12 and bottom plate-like disc 13. Intermediate these plates and sandwiched therebetween are alternate layers of flechette assemblies 14 and spacer disc plates 15. All the discs are circular and have an aperture therethrough, through which the driver 11 passes so as to form a structure about the driver. Although only two layers have been shown, it is clear that as many as necessary or desired can be assembled.

The flechette 16 illustrated in FIG. 3, essentially includes a circular elongated cylindrical body 17 whose forward end portion is formed with a sharp pointed tip 18. The opposite end thereof is formed with an outwardly and rearwardly divergent tail 19 that has flattened side walls 20. Disposed about the flechette body for sliding movement therealong is a fin assembly 21 which is provided with a central aperture 22 and four laterally extending fins 23. Since the fin assembly 21 can slide lengthwise of the body, then as the flechette body accelerates forwardly, the fin assembly will in relation to the body, move rearwardly as indicated. With a sudden, rapid acceleration, the fin assembly will move relative to the body and becomes impaled on the tail portion due to its divergent configuration and thereafter fixedly secured thereto. By fabricating the entire fin and flechette assembly of a plastic material the inherent distortion of such materials lends itself to the operation above described.

The flechettes are disposed within the assembly in an outwardly directed, radially oriented position with the fin assembly 21 proximate and coaxial with the pointed end and the flattened tail portion 20 inserted into a mating recess 24 (also see FIG. 3) in a piston pusher block 25. The pusher block is in abutting relation with the peripheral surface of the explosive driver 11 and supports the rear of the flechette. Forward support is provided by pairs of wedge support blocks 26 intermediate adjacent flechettes. The fins of each flechette rest thereon and a like block pair disposed to rest on the upper fin surface and abut the lower face of the plate immediately thereabove. Thus the flechettes are releasably supported and pointed in the ultimate direction of flight. These wedge supports could be stamped out or united and combined to reduce the overall number and of almost any relatively rigid material. It is clear from the foregoing that the function of the wedges could equally well be performed by forming the plates with radial recesses for supporting and guiding the flechettes or any other releasable support means. The entire launch assembly is surrounded, encapsulated or encased in skin, membrane or sleeve of suitable plastic or thin metal for containing and protecting the components. The explosive driver may be of any suitable explosive or propellant such as sheet explosive, composition C-4 or preferably a propellant which exhibits no brisance but provides energy in the form of a high pressure low velocity wave. Initiating means, such as wires 27 are provided to detonate the driver although fuzes of various types could be substituted dependent on the ultimate purpose of the launch system. These means include electrical, chemical, mechanical, remote, self-contained, time controlled and environmental sensors or other suitable means for functioning the explosive driver. In operation the device is delivered to its operational destination and thereafter initiated. When the driver bursts it rapidly expands radially and imparts a high thrust to the pusher piston against its relatively large rear surface. This energy is transmitted to the flechette via its flattened rear edge face disposed within the piston notch. The flechette body then travels through the stationary fin assembly which is impaled on the taper of the flattened end of the body and both proceed in the direction of flight locked together. Since the pusher piston has a higher aerodynamic drag than the assembled flechette it will lose contact therewith soon after the thrust force terminates. FIG. 2 shows the action immediately after the explosive driver has been detonated. The plates serve to confine the energy therebetween and direct it a generally radial direction for proper launching. The device as disclosed is of the antipersonnel type in the form of a land mine but can also be used for air bursts, jump-up device, booby traps, etc.

Illustrated by way of FIG. 4 is one form of a radial plane wave generator 40 which is in the shape of a right circular cylinder. The volume thereof is divided into three major sectors a first outer annular cylinder 41, an inner right cone 42 which is designated as a waveshaper and the volume intermediate the first two volumes. The point of explosive initiation is at the apex 43 of the cone. The first two volumes being filled with a suitable explosive such as Composition C-4 while the intermediate volume 44 is air or some inert material. The explosive material and/or the inert material are selected such that their respective detonation wave velocities provide a wave transit time from the point of initiation 43 to the base of the cone 45 which is equal to that from the point 43 to the inner peripheral surface 46 of the annular cylinder 41. The conical waveshaper in conjunction with the cylindrical configuration serves to produce a radially directed right circular cylindrical plane wave. The plane wave generator 40 is entirely contained in a jacket 46 which is axially disposed between a pair of plates 47 and 48 and supported by a cylindrical sleeve 49 which extends into both plates. Disposed circumferentially about the planewave generator or driver 40 in a lateral orientation, pointed in either direction, are a multiplicity of flechettes 50 which may be imbedded in an inert, compatible supporting matrix 51 such as expanded foam. When desired, upper 52 and lower 53 annular supports are provided. A casing 54 as described in conjunction with the formerly described embodiment surrounds the structure. It shoud be noted that standard flechettes are used and the side or lateral thrust from the generator is applied to the body of the flechette which effectively represents a relatively large area. Almost immediately after the launch the aerodynamic forces acting on the flechette due to the fins turn the flechette to point and be properly directed in the forward direction of flight.

An improved flechette design is illustrated in FIG. 5 wherein the device 60 is generally of the standard configuration including a forward pointed end 61 and a thin elongated body 62 from which extends an integral fin assembly 63. The fins 64 themselves are thin, sheet-like elements which are perpendicular to each other and joined along an axial line 65. In the standard design the fins terminate in a transverse plane (represented by dotted line 66) with the fins joined at a point 67. Since the fins are structurally, thin weak elements, upon launch a portion of the thrust is borne by the rear edge end face of each fin, and produces a distortion or twist in the fin itself. The fin upon being distorted, functions as a rudder and results in a flight pattern which is not radially linear thus defeating the intended purpose of the flechette. By extending the fins rearwardly and physically making them integral thereat as by nub 68 that is rearwardly convergent or pointed the fins are strengthened and fixedly secured. The flechette is aerodynamically (streamline) shaped which shape is not altered by the rear nub and the laminar air flow during flight remains undisturbed.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.