GB2209201A

GB2209201A - Detonation triggering means for projectiles

Info

Publication number: GB2209201A
Application number: GB8817929A
Authority: GB
Inventors: Roland Schmidt; Kurt-Volker Hechtenberg; Richard Benedikter
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1987-08-27
Filing date: 1988-07-27
Publication date: 1989-05-04
Anticipated expiration: 2008-07-27
Also published as: FR2619901B1; GB2209201B; DE3728560C1; GB8817929D0; FR2619901A1

Description

1 1 1 PKD140788 DETONATION TRIGGERING MEANS FOR PROJECTILES 2209201 This

invention relates to detonation triggering means for projectiles, particularly hollow charges, which have a forerunner or lead projectile which prior to firing is arranged on the front part of the projectile and which at the moment of firing or shortly thereafter detaches itself from the projectile and then travels ahead of same with specific differential velocity.

For projectiles in which detonation is to be triggered at the moment of target impact of the projectile, or shortly thereafter, electro-optical impact detectors are known, in addition to mechanical or electrical detectors, which respond to the flash of light generated by the projectile upon the target impact and thereupon initiate the detonation. Such an arrangement is disclosed in German patent specification No. 34 24 868.

On the other hand, in the case of projectiles which develop their greatest effectiveness at a specific distance from the target, particularly hollow charges, where the most favourable target range lies at about 2 to 3 calibres, ignition mechanisms are necessary which PKD140788 respond prior to impact of the projectile and trigger its detonation at the correct distance from the target. For this purpose, detonation means of such projectiles usually comprise a rigid or extensible distance piece on which there is mounted, at a predetermined target distance in front of the tip of the projectile, an impact sensor which triggers the detonation of the projectile when it strikes the target. Alternatively, in the case of known projecXiles of the type with which the invention is concerned, as disclosed, for example in U.S. patent specification No. 3 416 448, a forerunner or lead projectile is used which detaches itself from the front part of the main projectile upon or shortly after firing and travels ahead of this. In all previous proposals the forerunner projectile remains coupled with the main projectile by way of a contact wire, or another flexible connection element, which is stretched during the flight up to a length corresponding to the required target distance, and upon target impact generates a.detonation triggering signal which is transmitted by way of the flexible connection element to a detonation mechanism on the main projectile. Both detonation arrangements having a rigid or extensible distance piece and those having a contact-wire-guided forerunner projectile require great accuracy in

1 -r W PKD140788 construction and are costly to produce, and in the case of the latter there is the additonal difficulty, particularly in the case of a long straight firing path, of tensioning the contact wire or other flexible connection element without a disturbing effect on the flight behaviour of the projectile.

The object of the invention is to provide detonation means of the kind mentioned at the beginning hereof in such a way that with simple structural means, and more especially without constructionally complex coupling between main projectile and forerunner projectile, reliable detonation triggering at a predetermined target distance is guaranteed.

This object is achieved in accordance with the invention in that a forerunner projectile which travels ahead of the projectile in unfettered manner and gives off a radiation pulse upon impact is used, and the main projectile contains a receiving device for the radiation pulse, a twostage integrator with a first integration stage which represents integration of the differential velocity of forerunner projectile and main projectile during the flight until.the reception of the radiation pulse and a second integration stage which provides the PKD140788 - 4 difference between the content of the first integration stage and the time integral of the projectile velocity as from the instant of the pulse reception, as well as a threshold-value detector which emits a detonation pulse as soon as the difference provided by the second integration stage falls below a predetermined limiting value.

In accordance with the invention, in conjunction with the special design of the detonation triggering device on the main projectile, a forerunner projectile is used which speeds ahead of the main projectile in unfettered manner, along with constant increase in the forerunning distance between the main projectile and the forerunner projectile. The size of this forerunning distance is ascertained constantly by time integration of the differential velocity in the first integration stage, so that the content of this integration stage upon target impact of the forerunner projectile corresponds to the distance of the projectile from the target, whereupon the radiation pulse generated by the impact of the forerunner projectile activates, in a wireless manner, the second integration stage, which now forms the time integral of the projectile velocity and subtracts same from the content of the first integration stage, until PKD140788 1 the thus formed difference corresponds to the required target distance of the projectile and the thresholdvalue detector preset to this target distance emits a detonation-triggering pulse. The detonation triggering means in accordance with the invention can be realised in a structurally very simple manner, without a mechanical coupling between the forerunner projectile and the main projectile being needed, and it works extremely reliably and with a detonation-triggering distance which is variably presettable to the required value at the threshold-value detector. It is particularly suitable for projectiles having a long straight firing path, and above all hollow charges.

In a further, structurally particularly simple development of the invetion the integrator is preferably designed as an analog circuit, for which as main components merely a capacitor, a charging-current limiter and a discharging-current limiter are needed in which respect the capacitor voltage in the first flight phase up to receipt of the radiation pulse corresponds to the forerunning distance between the main projectile and the, forerunner projectile and in the second flight phase after the target impact of the forerunner projectile corresponds to the target distance of the PKD140788 6 projectile which reduces in accordance with the projectile velocity as far as the required limiting value.

In some instances of use it may be necessary to set the charging and/or discharging current variably by an appropriate pre-programming of the current limiters. For example, in cases where the differential velocity between the forerunner projectile and the main projectile in the working phase of the first integration stage and/or the projectile velocity in the working phase of the second integration stage change noticeably. However, in most cases the velocity changes are slight, especially in the case of a long straight firing.path, and accordingly, with a view to a further structural simplification, a constant-current circuit, preferably a field effect diode, is advantageously used as the charging or, respectively, discharging current limiter. The structurally simplest development of the integrator, in which merely resistors are provided for the charging and discharging current limitation of the capacitor, is particularly to be preferred when the differential and the projectile velocity changes in accordance with the voltage course of an R C member, or certain tolerance range is permitted for the required detonation

1 PKD140788 7 triggering distance of the projectile with regard to the target.

The simplest form of radiation pulse is constituted by the impact bang of the forerunner projectile. However, in view of the high propagation speed, and for ease of detection a flash of light is preferred, which is emitted upon target impact of the forerunner projectile. This is detected by a light-flash-sensitive switching element of the receiving device which then renders the first integration stage ineffective and switches on the second integration stage.

Finally, in order to be able to predetermine variably the ignition triggering distance of the projectile, an adjustable threshold-value detector is advantageously provided.

The invention will now be explained in more detail with reference to two exemplified embodiments in conjunction with the drawings. In diagrammatic representation: Fig. 1 shows a projectile, including a forerunner projectile, with a flat firing path in various PKD140788 flight attitudes between firing and target impact of the forerunner projectile; Fig. 2 is an analog circuit forming the two-stage integrator; Fig. 3 is a graph which shows the voltage course, proportional to the forerunning distance of the forerunner projectile or to the target distance of the projectile, at the capacitor of the analog circuit in accordance with Fig. 2; and Fig. 4 is a modified analog circuit, in which respective resistors are provided for charging and discharging current limitation.

In accordance with Fig. 1 a projectile 2 in the form of a hollow charge is fired at the instant t 5 on a long, straight firing path S in the direction of the target Z. Arranged in the front part of the projectile, for instance at the tip of the hollow-charge cone, is a forerunner projectile 4, which is designed as a sphere, which gives off a radiation pulse upon impact, and which detaches itself from the front part of the projectile 2 PKD140788 1 - 9 upon or shortly after firing. The forerunner projectile 4 travels ahead of the projectile 2 as a predetermined differential velocity, i.e. with a forerunning distance which increases steadily along the firing path S dependent upon the flight time. The separation of the forerunner projectile 4, and its higher velocity compared with the projectile 2, are brought about by knetic and/or aerodynamic processes and can be achieved by a small pyrotechnical bursting charge (not shown) which is ignited upon firing.

Thus, in an intermediate position between firing and target Z, i.e. at the instant t 1 shown in Fig. 1, the forerunner projectile 4 has distanced itself from the projectile 2 by the forerunning distance si. and at the instant t 27 when the forerunning distance has increased to S 2 the forerunner projectile 4 encounters the target Z and emits the said radiation pulse, e.g. a bang, but preferably a flash of light, which is received by a detonation triggering device on the main projectile. After receipt of this signal the projectile 2 draws closer to the target Z, at the projectile velocity and on the firing path S, until at the instant t 3 it reaches a predetermined ignition triggering distance D (most favourable for the desired effect of the projectile) 0 PKD140788 - 10 from the target Z, whereupon detonation of the projectile 2 itself is effected.

As shown in Fig. 2 the detonation triggering device in the projectile 2 is designed as an analog circuit and contains a voltage sourse 6, an acceleration switch 8, which is closed by the firing acceleration at the moment of detachment of the forerunner projectile 4 from the projectile 2, and a capacitor 10 with a charging currect limiter 12 and a discharging current limiter 14, each of which are designed as a respective constantcurrent circuit in the form of a field effect diode comprising a selfconductive field effect transistor 16 and,. connected subsequent to this on the drain side an adjustable resistor 18. Connected in series with the discharging current limiter 14 is a radiation-pulse receiving elemet 20, e.g. a photothyristor, which is caused by the flash of light of the forerunner projectile 4 to tilt over into the conductive state. Connected in parallel with the capacitor 10 is an adjustable threshold-value detector 22, which emits a detonation triggering signal as soon as the capacitor voltage drops below below the preset threshold value.

S PKD140788 11 - By way of the switch 8, which closes simultaneously with the detachment of the forerunner projectile 4, and with the photothyristor 20 initially still blocked, the voltage of the battery 6 is applied to the chargingcurrent limiter 12 and the capacitor 10, which constitutes a first integration stage. In this respect, the charging-current intensity is kept, by appropriate adjustment of the resisitor 18 associated with the charging-current limiter 12, at a value which is proportional to the velocity difference between the forerunner projectile 4 and the main projectile 2. In the space of time t 0 to t 2 the capacitor voltage U c (Fig. 3) is thus proportional to the time integral of this velocity difference and a direct measure of the size of the forerunning distance S between the forerunner projectile 4 and the main projectile 2.

Upon receipt of the flash of light at the instant t2, when the projectile 2 is remote from the target Z by the forerunning distance s 20' the photothyristor 20 is switched to conductive mode and in this way a second integration stage constituted by the capacitor 10 and the dischargingcurrent limiter 14 is activated, so that the capacitor 10 now discharges.

PKD140788 The current intensity of the discharging-current limiter 14 is so set by its associated resistor 18 that it exceeds the constant current of the charging-current limiter 12 by a value which is proportional to the projectile velocity. In other words, as from the instant of receipt of the signal thd capacitor voltage Uc is smaller than at the instant t 2 by an amount corresponding to the time integral of the projectile velocity and a direct measure of the target distance of the projectile 2.

As soon as the capacitor voltage has dropped to the threshold voltage U S set at the threshold-value detector 22 in accordance with the required detonation triggering distance D, the threshold-value detector 22 emits a detonation pulse for the hollow-charge projectile 2. By means of the threshold value U S the detonation triggering distance D can be set independently of the flight time.

The mode of construction and operation of the analog circuit in accordance with Fig. 4 corresponds largely to that of the first exemplified embodiment. The sole difference is that the constant-current circuits 12, 14 are replaced either by simple resistors, or by W PKD140788 K potentiometers 112 and 114. Thus, the charging and discharging curves of the capacitor 10 do not extend straight, but in accordance with an efunction. This structural simplification is particularly to be preferred when the forerunner projectile and main projectile velocities change in a flight-time-dependent manner in accordance with the current course of an RCmember and/or a certain tolerance range is permitted for the detonation triggering distance D.

Instead of being designed as an analog circuit, the detonation triggering device can also be designed as a digital circuit with a pulse counter as integrator, which in the first integration stage counts up the counting pulses, generated with a frequency corresponding to the velocity difference between forerunner projectile 4 and main projectile 2, until receipt of the flash of light. Subsequently, in the second integration stage it counts downwards, from the thus achieved counter state, the counting pulses generated with a frequency corresponding to the projectile velocity, until the counter state drops to a limiting value predetermined in accordance with the required detonation triggering distance D, whereupon a threshold-value detector, designed in this case as a PKD140788 comparator, emits the detonation pulse for the projectile 2.

PKD140788 7

Claims

CLAIMS:

1. Detonation triggering means for projectiles having a forerunner projectile which prior to firing is arranged on the front part of the projectile and which at the moment of firing or shortly thereafter detaches itself from the projectile and then travels ahead of same with a specific differential velocity, characterised in that a forerunner projectile which travels ahead of the projectile in unfettered manner and gives off a radiation pulse upon impact is used, and the main projectile contains a receiving device for the radiation pulse, a twostage integrator with a first integration stage which represents integration of. the differential velocity of forerunner projectile and main projectile during the flight until the reception of the radiation pulse and a second integration stage which provides the difference between the content of the first integration stage and the time integral of the projectile velocity as from the instant of the pulse reception, as well as a threshold-value detector which emits a detonation pulse as soon as the difference provided by the second integration stage falls below a predetermined limiting value.

PKD140788 16

2. Detonation triggering means as claimed in claim 1, characterised in that the intergrator comprises a capacitor, a charging-current limiter which is effective during the flight up until the pulse reception, and a discharging-current limiter which is effective as from the instant of the pulse reception, and the thresholdvalue detector responds when a predetermined voltage at the capacitor is fallen below.

3. Detonation triggering means as claimed in claim 2, characterised in that the discharging-current limiter is variably adjustable in accordance with the projectile velocity and the charging-current limiter is variably adjustable in accordance with the velocity difference between the forerunner projectile and the main projectile during the flight.

4. Detonation triggering means as claimed in claim 2 or 3, characterised in that the charging or respectively discharging current limiter is constituted by a constant-current circuit.

5. Detonation triggering means as claimed in claim 4, characterised in that the constant-current circuit is constituted by a field effect diode.

z v PKD140788

6. Detonation triggering means as claimed in claim 2 or 3, characterised in that the charging or respectively discharging current limiter is constitiuted by a resistor.

7. Detonation triggering means as claimed in any preceding claim characterised in that the radiation pulse is a flash of light and the receiving device is a light-flash-sensitive switching element.

8. Detonation triggering means as claimed in any preceding claim, characterised in that the limiting value of the threshold-value detector is adjustable.

9. Detonation triggering means for projectiles substantially as hereinbefore with reference to Figs. 1 to 3 or Figs. 1 and 4 of the accompanying drawings.

Published 1988 at The Patent Office. Sta..,e House 6671 High Ho'bornLondon WC I R 4T F Further copies maybe obtained from The Patent Office, w.r.T BR5 3RD Printed by Multiplex techniques ltd. St lliaaW Cray, Kent Con 1 87 '