GB2036935A - Improvements in defence systems - Google Patents

Abstract

One or more decoys are provided in order to confuse a hostile craft such ass guided missile, using passive energy re-transmissive mass(es) in the form of a bundle of material such as gossamer metallised plastic foil launched as a hostile craft is detected and the bundle is illuminated passively to provide a re-transmission of energy to which the hostile craft is responsive. The bundle may be illuminated, for example, by a radar beam and/or a laser beam the latter causing the bundle to heat up.

Description

SPECIFICATION Improvements in or relating to defence systems This invention relates to defence systems and in particular to defence systems provided to combat homing missiles.

As is well known missiles are commonly provided with some means of homing into a target.

Examples of such missiles include so called "antiradar" missiles which are provided to home into a source or radar frequency heat seeking missiles which home into sources of heat and missiles with active radar.

It is known to provide some form of decoy system with the object of "confusing" the missile guidance system and so tend to divert it from its true target. Decoy systems as at present known, however, tend to be complex and expensive and often not all together satisfactory when a decoy installation is involved which is itself rendered totally inoperative by a missile hit.

The present invention seeks to provide an improved defence system and in particular an improved defence system for combatting homing missiles in which the above difficulties are mitigated.

According to this invention a defence system comprises means for launching a passive energy re-transmissive mass and energy transmission means for illuminating said mass when launched to provide re-transmission thereby of energy of a kind to which hostile homing system is responsive whereby to provide a decoy therefor.

Whilst the system in accordance with the present invention may be utilised to decoy hostile manned machines normally the system will be concerned with providing decoy defence against guided missiles. Said mass may take the form of a bundle of reflective foil material, e.g. metal strip foil or gossamer metalised plastic foil. Where strip metal foil is used this may be similar to so called "chaff".

Said energy mass may be arranged to be illuminated by a radar beam and/or a laser beam to provide a heating effect and/or other sources of energy to which a hostile homing system may be responsive.

In one embodiment of the invention intended to combat hostile homing systems with active radar means are provided for receiving the radar transmissions of a hostile homing system and retransmitting these to illuminate said mass.

In another embodiment of the invention two coupled radar signal transmission systems are provided, one arranged to provide its normal radar interrogating function and the other provided to illuminate said mass in such manner that the radar beam from said radar signal transmission system which operates normally and the radar beam reflected by said mass are substantially parallel.

'Normally the direction in which said mass is launched is such that the direction of approach of a hostile missile or craft is normal to the plane containing both the target which is to be defended and the energy mass.

Preferably said mass is launched by means of a mortar.

As will be appreciated a bundle of gossamer metalised plastic foil for example will stay airborne often for several minutes. If desired more than one passive energy re-transmissive mass may be launched simultaneously or otherwise and in similar directions or otherwise.

Referring to Figure 1 a ground installation which is liable to be attacked by a guided missile is represented at 1. The installation is provided with a radar system of which the antenna is represented at 2. It is assumed in this instance that the guided missile is a so-called "anti-radar" guided missile that is to say one which homes in onto sources of radar frequency.

The installation 1 is surrounded by a number of mortars of which only two referenced 3 and 4 are shown, the mortars 3 and 4 are provided to launch a bundle of gossamer metalised plastic foil similar to that material which is commonly referred to as "chaff". The bundle of foil is launched as represented at 5.

In operation when the approach of an anti-radar missile is detected the bundle of foil 5 is launched by the most convenient of the mortars in this case mortar 3. The bundle of foil 5 is launched so that the direction of approach of the missile is approximately normal to the plane containing both the target i.e. the radar antenna 2 and the bundle of foil 5. As the bundle 5 is launched it is tracked by the radar antenna 2 and illuminated with radar energy which the bundle then reflects to provide a decoy apparent source of radar energy.

Whilst in this present embodiment the target radar antenna itself is diverted in order to provide the required illumination of the bundle of foil 5, if desired a separate radar system may be provided for this purpose. Furthermore, whilst only one bundle of foil 5 is represented as being launched other bundles may be launched if desired.

Referring to Figure 2 in this case a seaborne system is represented and the missile threat is assumed to be from a heatseeking missile.

In this case upon the detection of the approach of the missile the bundle of metalised foil 5 is again launched such that the direction of approach of the missile is normally to the plane containing the bundle 5 but instead of being illuminated by a radar the bundle of foil 5 is illuminated by a high power CO2 laser 7 which acts to heat the bundle of foil 5 to provide the required decoy.

Referring to Figure 3 in this case the missile here represented at 8 is presumed to have an active radar. In this case a receiver the antenna of which is represented at 9 is provided to receive the interrogating signals transmitted by the missile radar. After amplification the signals originating from the missile are retransmitted at higher power by a directional antenna 10 which is directed at the launched bundle of foil 5. This results in the missile receiving what are apparently strong responses from a target the bundle of foil 5.

Referring to Figure 4 in this case the target is again a ground installation and the missile is presumed to be an "anti-radar" missile. In this case the reflective mass which is launched by the mortar 3 is a lightweight film reflector capable of remaining airborne for several minutes. The launched reflector is now referenced 5' and is illuminated by a radar antenna 2' which is coupled to a main scanning radar antenna referenced 2.

The effect is to provide two radar beams here referenced 11 and 12. The phase and amplitude relationship between the signals transmitted by the antennas 2 and 2' are arranged to be controllable so as to alter the apparent direction of the target signals as seen by the "anti-radar" missile.

Whilst each of the systems described with reference to Figures 1 to 4 above each shows a single type of energy directed to illuminate the launched reflector 5 or 5' it would be appreciated that the various measures proposed may be combined thus for example in Figure 1 the bundle of foil 5 may be illuminated not only by the radar beam from the antenna 2 but also by a CO2 laser like that used in the embodiment of Figure 2 to provide a measure of protection against either the "anti-radar" missile or a heat seeking missile.

Claims (14)

1. A defence system comprising means for launching a passive energy re-transmissive mass and energy transmission means for illuminating said mass when launched to provide retransmission thereby of energy of a kind to which hostile homing system is responsive whereby to provide a decoy therefor.

2. A system as claimed in claim 1 and wherein said mass takes the form of a bundle of reflective foil material.

3. A system as claimed in claim 2 and wherein said mass is metal strip foil.

4. A system as claimed in claim 2 and wherein said mass is gossamer metalised plastic foil.

5. A system as claimed in any of the above claims and wherein said mass is arranged to be illuminated by a radar beam.

6. A system as claimed in any of the above claims and wherein said mass is arranged to be illuminated by a laser beam to provide a heating effect and/or other sources of energy to which a hostile homing system may be responsive.

7. A system as claimed in any of the above claims and intended to combat hostile homing systems with active radars and wherein means are provided for receiving the radar transmissions of a hostile homing system and retransmitting these to illuminate said mass.

8. A system as claimed in any of the above claims and wherein two coupled radar signal transmission systems are provided, one arranged to provide its normal radar interrogating function and the other provided to illuminate said mass in such manner that the radar beam from said radar signal transmission system which operates normally and the radar beam reflected by said mass are substantially parallel.

9. A system as claimed in any of the above claims and wherein the direction in which said mass is launched is such that the direction of approach of a hostile missile or craft is normal to the plane containing both the target which is to be defended and the mass.

10. A system as claimed in any of the above claims and wherein said mass is launched by means of a mortar.

11. A system as claimed in any of the above claims and wherein more than onepassive energy re-transmissive mass are arranged to be launched simultaneously or otherwise and in similar directions or otherwise.

12. A defence system substantially as herein described with reference to Figure 1 of the accompanying drawing.

1 3. A defence system substantially as herein described with reference to Figure 2 of the accompanying drawing.

14. A defence system substantially as herein described with reference to Figure 3 of the accompanying drawing.

1 5. A defence system substantially as herein described with reference to Figure 4 of the accompanying drawing.