US2505042A - Antiaircraft projectile and fuse for said projectile - Google Patents

Description

April 25, 1950 R. GOURDON 2,505,042

ANTIAIRCRAFT PROJECTILE AND FUSE FOR SAID PROJECTILE Filed July 23, 1947 [/VVi/YTOR W memr. GOUROO/V Patented Apr. 25 1950 UNITED STATES orrics ANTIAIRCRAFT PROJECTILE AND FUSE FOR SAID PROJECTILE French company Application July 23, 1947, Serial No. 762,973 In France July 29, 1946 Claims. (Cl. 102-702) The present invention relates to anti-aircraft projectiles.

It is known that it is extremely diflicult to obtain a direct hit on an aircraft moving at a very high speed, the path of which is always liable to sudden and unexpected variations.

Endeavours have been made to construct projectiles provided with very accurate time fuses which are intended to cause the shell to explode at a predetermined time after the shot has been fired; in spite of this, such projectiles are of very doubtful eficiency and involve a considerable waste of ammunition.

It has also been proposed to construct electronic fuses provided with ultra-short wave transmitting and receiving devices, but this type of fuse is fairly complicated and comparatively expensive to manufacture.

The present invention has for its object an antiaircraft projectile and a fuse which is extremely simple and easy to manufacture for said projectile and is based on an entirely different principle, said fuse being such that the projectile automatically bursts as soon as it is near the target.

Said projectile comprises, in combination, a metal body, an explosive charge in said body, and at the front of said body a fuse which is adapted to ignite said explosive charge by the action of the discharge, 1. e. the flow, through said fuse and said body, of a portion of the electrostatic charge which has accumulated on the target, said projectile, when it is adjacent to said target and owing to its high speed of translation and rotation, producing a preferential path (i. e. a path of lower ohmic resistance than that of all the other possible surrounding paths) which is followed by said electrostatic charge of the target in order to reach a region of the atmosphere at lower potential.

It is in fact known that a moving body such as an aircraft, moving at high speed through the equipotential layers of the atmosphere, becomes charged at a higher potential than that of the equipotential layer through which it is moving. After saturation, the charge thus accumulated on said aircraft flows away slowly and continuously towards the ground. The tapering shapes of the wings of the aircraft and of the elevator and rudder, contribute to this leakage towards the lower layers at lower potential.

Under these conditions, if another moving body, such as a projectile, is fired obliquely upwards in the direction of the aircraft, it produces an oblique disturbance in the atmosphere. The disturbance of the layers of air through which it passes is greater as the translational and rotational speeds of the projectile are higher and a considerable ionization is thereby produced in the immediate vicinity of said projectile and chiefly behind it. This ionization is due, on the one hand to the direct impact on the air and the particles in suspension which are encountered, and on the other hand to the vortex that the projectile forms behind it. The ohmic resistance of the surrounding layers through which the projectile passes is therefore substantially changed and a highly ionized preferential discharge path of a certain length is-thus formed which is a better conductor than the surrounding air that has remained calm between the surrounding equipotential layers; it is along this preferential path, the ohmic resistance of which is decreased owing to the presence of the projectile and to the ionization which it produces beh nd it, that a portion of the electrostatic charge accumulated on the surfaces of the aircraft flows.

The ionized path comprises the nose of the fuse, the body of the projectile and its disturbed Wake. The projectile according to the invention makes use of the quantity of electricity which is supplied by the target and which flows a10ng said path and supplies the necessary energy to produce a spark without it being necessary to have recourse either to a special source of electric power contained in the projectile, or to a capacity and electrostatic discharge effect of said projectile.

The invention also has for its object a fuse intended for said projectile. Said fuse comprises, in combination, a detonator, a primer located adjacent to said detonator, means for producing through said fuse a path of lower electric resistance than that of the surrounding portions for the discharge of a portion of the electricity accumulated on the target opposite the projectile when said projectile is near said target, and means for igniting said primer by means of said discharge.

With such a device, the ignition occurs automatically as soon as the projectile is sufficiently close to the target for the electric discharge of the static electricity of the target to take place through said fuse; the projectile therefore does not have to come into contact with the target in order to explode; on the other hand, when it explodes, it is at a suitable distance from the target for the effect of the explosion and of the projection of splinters to be efiective.

The invention also has for its object a projectile of the aforesaid type, wherein the fuse is protected, before the projectile is fired, from any untimely electric discharge through it my means adapted to be eliminated when the shot is fired, for example by centrifugal effect, since it is essential for such a projectile to be provided with a safetydevice that protectsiit from anyv accident that could becaused by atmospheric discharges, the proximity of high tension electric lines, electric motors in operation, and the like.

Other features and advantageswill become-apparent from the ensuing description.

In the accompanying drawing which is given solely by way of example:

Fig. 1 is an axial section 'of' aprojectile fuse according to the invention;

Fig. 2 shows a partial axial;: section,-.,: on. its trajectory, of a projectile containingaazitracer charge;

Fig. 3 shows diagrammatically thepath'followed by the electrostatic discharge when a projectile of the type shown in-Fig. 2 is close to the target;

Fig. 4 is a fragmentary 'sectionof amodification.

"According to'the'embodime'nt shown in Fig. 1," the fuse comprises a'fuse-body tin which is fitted," by moulding or otherwise, an insulating portion 2 formingthe front part of the fuse. The

body I andth insulating portion 2 which are closely secured togetherare of 'ogival external 30 shape.

The insulatingportin*2 surrounds a filiform axial electrode 3 which-is advery good conductor.

fine' sheet of tin, completely covers-theogivein order to protect the fuse from any untimely discharge "of electricity through said fuse-until the instant when the projectile leaves the "gun, said sheet of tin being sumcientlythin'to-be eliminated, when the shot is fired,-'for example merely by-the effect of the centrifugal" force.

A primer 5 is housed in an insulating cup 6 which is preferably made of compressedinaterial. Said cupis in turn fitted inthe-rear section of the insulating portion 2." Thepr-imer' which does not contain any 'extra sensitivesubstance (lead nitride) contains a small percentageof mercury fulminate (about 38%) and substances capable of effecting thedivision,the-oxidation-'or the-binding of' the compound (about 10- to 20% of calcium silicid eyabout 30 to 40% ot-barium nitrate;- about '7 a to 10%of le'ad peroxide) This compound is insensitive-to-mechanical shockssuch asn'iight be caused by-cr-ushing the nose 'of the fuse; it islsuch that' -its ignition is. produced by a sort of chain'reaction of the mercury fulmiriate crystals? which are isolated from one another by the calcium si1ic-ide at least one of said crystals being ignited by the calorific and/or electronic 'eifectof a spark pr'oduced by a potential difference of a-few-' thousandvolts and a weak current of the orderof-onemicro- 3 ampere.

The rear end of the axial electro'deliiskept I at a very short distance 6 from the-primer-E by the thickness ofthe cup 6 which is provided with a central hole l, therebybrea-king'the circuit at this point. Thisgap'doeshotexceed a-few tenths of a millimetre.

8 for example of tin, which is held in position by a detonator-holder 9 screwed at In in the body 5. The charge I! of this detonator is supported by a diaphragm l2 provided with a cen- 5 tral hole l3 which is intended to transmit the Li'fire.

'The projectile i shownin Fig; 2 on its trajectory comprises a fuse such as hereinbefore dewscribed. The rear portion of the detonator is l0'.housed. in the mass. of explosive l5. This prothe primer 5 in its compact shape and prevents it from penetratingsbyr inertia .intosth hole I 3.

The very fast rotation and also theghiglnspeed of translation of the projectile. asdt-mises obliquely into'the atmosphere causes. aidisturbance 19::(Fifi.

3) behind said projectile .\..and,-. after; a .-,cer.tain

altitude, said disturbance.iproduces ahighlyionized --pathover a,.i.diSt3,DC8 ewhichnconnectss. together-- layers: of air, the r potential; difference Vn-'-V1-(F-ig.- 3) of which may.reachseverahthoflsand-volts. J ft -shouldw benotedthat ether distance between :the 1 two layersLVn. and. Vhneed .not.;.be "large, since the operation of :..the:-.. fusev list v.pro-

duced by a potential differencerbfiaefeve thousand-volts on eitherside :of the .spark gap 15.

This ionization of the trajectory abehindi the projectile is further. increased in theease; 2 in ---which the projectile is pr0vided,.-With a tracer charge H, the combustion of whichhasithe effect of projecting rnetal-A particles; 2 c T;(Fig;; 2 ,aialong said trajectory.

When -the projectile approa'chesi-the target'ZI (aircraft) (-Figs. 2-and:3)i,: the electrostatic charge which hasaccumulated o rrsaidtarget .as ,it-nioves at high speed throughs-the equipntentialmlayers L15 of the atmosphere is displaced in the direction of the projectile and accumulates on an area-.-:22 of -=high surface density. The: charge:-voltage.on:.the

4 surface -Z 2- ismuch-higher than that 0f. theequire potential layer 'through .1 which thenaircraftsis -moving owingtothe speednf said aircraftand the accumulation of: ionscaused thereby. :iSaid chargeis many caseahighersthan that whichnan 1 be collected :by the. projectile of .much smallersize -wh-ich is-movingtowards itiand ispassing through the same'ionized layer.

Gonsequently,=as soon as-theprojectile is at a distance from the target-equaltown-shorterthan a-certain distance a (Fig;-3) awleakage of thelelec- -trostatic charge takesaplace lalong the: :linesi 23 0 from the surface 22 towards the-preferentiallpath,

i; e; the p-athof least-=ohmicresistance; formed -by the projectile itself andits-highly-ionized wake 9;the ionization being further increased-\by -the -metalparticles Ea -Said leakage isrconcentrated towards the tip of theogive-of-the-projectile.

--'Almost' the entire eharge ofielectricity, inl -the form of arbrush discharge,afollows the path of the-central electrode Bavhichis well insulatedi-and which, since it is preferably of electrolytic copper,

isotmuch higher- -conductibility than the- -surrounding medium, whi-le itscapacity: which has vabsolutelyno function to performherein, is nearly nilQsince said electrode is {as short as possible.

Owing-to the gap 1 of w-idthe 'thatexists at 1 ='(F-ig 1); all the-"energy of the discharge is con- The heat energy produced by the disruptive spark and the electronic impact on the crystals of the primer 5 ignite said primer which fires the charge ll of the detonator through the opening l3 and causes the projectile M to explode without said projectile needing to come into contact with the target.

It should be noted that experiments have proved that the fuse is practically insensitive to an impact; it may for example pass through a hard obstacle without operating, since either the electrode 3 merely buckles, i. e. becomes curved, or it comes into contact with the primer at a considerably reduced speed such that, taking into account the relative mechanical inertia of the primer, the same does not operate.

Furthermore, it is possible to adopt the arrangement shown in Fig. 4, wherein the electrode 3 is bent for example twice symmetrically with respect to the axis at 3 and 3 50 that an accidental impact that produces a considerable deformation of the nose of the fuse merely deforms the bends 3 and 3 thereby avoiding a mechanical transmission of the stress from the electrode 3 to the primer 5.

Naturally, the invention is in no way limited to the embodiments illustrated and described which have only been chosen by way of example.

Thus the filiform electrode 3 of the foregoing examples may be replaced by a conducting substance, for example in powdered form, filling an axial duct provided in the insulating member 2.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An anti-aircraft projectile, comprising in combination a hollow metal body, an explosive charge in said body, and at least one fuse projecting from said body and comprising a dielectric mass forming a front nose that projects from the body of the projectile, at least one electric conducting element which has practically no capacity and which passes from end to end through said dielectric mass and terminates at the surface thereof by its forward end, a primer located at least adjacent to the other end of said conducting element, means fo igniting said primer by the action of the flow of an electric current through said conducting element and said projectile, and a detonator located adjacent to said primer.

2. An anti-aircraf t projectile according to claim 1, furthermore comprising, at the rear of said hollow body, a tracer charge with metallic particles for increasing the ionization of the atmosphere in the wake of said projectile.

3. A fuse for an anti-aircraft projectile, comprising in combination, a metal body, a dielectric mass housed in said body and forming a projecting front nose, at least one electrode extending through said dielectric mass and terminating at one of its ends on the outer surface of said mass, a primer located at least adjacent to the rear end of said electrode, means for igniting said primer by the action of a flow of electricity through said electrode and said projectile, and a detonator mounted in said body behind said primer.

4. Fuse according to claim 3, wherein said means for igniting said primer comprise a small spark gap provided between the rear end of said electrode and said primer which is sensitive to the electronic impact and to the heat which are produced by an electric discharge passing across said gap.

5. Fuse according to claim 3, wherein said electrode is filiform and is of very low electrostatic capacity.

6. Fuse according to claim 5, wherein said electrode is made of electrolytic copper of high conductivity.

'7. Fuse according to claim 3, wherein said electrode is filiform and has at least one bend therein so that an impact will cause it to yield and thereby prevent a mechanical ignition of the primer.

8. Fuse according to claim 3, wherein said primer is of a composition which is insensitive to a physical percussion produced by said electrode.

9. Fuse according to claim 3, furthermore comprising means for protecting it from any untimely electric discharge before it is fired.

10. Fuse according to claim 9, wherein said protecting means comprise a metal cover adapted to cover the front portion of said fuse and to be eliminated as the projectile leaves the barrel of the gun.

ROBERT GOURDON.

REFERENCES CITED FOREIGN PATENTS Country Date Norway Feb. 21, 1927 Number

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