GB2302224A

GB2302224A - Gun-launched guided projectile system

Info

Publication number: GB2302224A
Application number: GB8221793A
Authority: GB
Inventors: Brian Gordon Aitchison; David Arthur Murray
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1982-07-30
Filing date: 1982-07-30
Publication date: 1997-01-08
Anticipated expiration: 2002-07-30
Also published as: GB2302224B; GB8221793D0

Abstract

In a gun launched guided projectile system for use with small-calibre weapons, comprising a projectile launching gun, a control station 14 located remotely from the projectiles and associated with the gun, and a supply of projectiles, the control station includes means for tracking targets 12 and in-flight projectiles 11, means for predicting future target and projectile positions, a computer for calculating projectile course corrections and means for transmitting course correction signals to the projectiles in flight, and the projectiles have course correction means responsive to the course correction signals. Conveniently the course correction signal comprises a common directional reference signal which may be a plane-polarised radio wave, and a subsidiary reference signal, which may be a laser beam scattered from the sea surface below the projectile flight path. Each course correction signal may include an indication of the time of flight of the projectile to which that signal relates, each projectile being arranged to respond only to those course correction signals containing the appropriate time of flight so that many projectiles may be addressed and guided separately in a single communications channel.

Description

TITLE: GUN-LAUNCHED GUIDED PROJECTILE SYSTEM This invention relates to a gun-launched guided projectile system.

Gun-launched guided projectiles (hereinafter referred to as GLGPs) are known in artillery, and comprise a missile or similar projectile for launching from a conventional gun. Conventional GLGPs contain on-board target detection and missile guidance and control equipment to enable the missile to home on a target after launch. This gives superior hit probability as compared to a conventional shell, which once fired cannot change course to compensate for target manoeuvres. Conventional GLGPs are restricted to calibres above about 72mm, since it is difficult to design a small-calibre GLGP incorporating the required target detection and missile control equipment. There is however a need for GLGPs of smaller calibre.

It is an object of the present invention to provide a GLGP system suitable for use with small-calibre weapons.

The present invention provides a GLGP system including a projectile launching gun, a control station associated with the gun and adapted to track targets and projectiles in flight and to supply projectiles with course correction signals for target mics distance reduction, and a supply of GLGPs having course correction means responsive to the course correction signals. The GLGP system of the invention has the advantage that each projectile requires remotely controlled course correction roans and limited coroputational facilities only, tracking and course correction computation moans being located remotely at the control station.In view of the reduction in projectile-borne equipment, the invention makes it possible to provide a small-calibrc GLGP system, unlike prior art device Furthermore, each CLGP is considerably less expensive than prior art devices, due to the reduction in irrecoverable equipment incorporated therein.

The GLGP control station preferably includes means for tracking a target and in-flight projectiles, means for predicting future target and projectile positions and a computer for calculating projectile course corrections required to reduce target miss distance. The control station preferably also includes a transmitter for communicating course correction signals to the GDGPs or projectiles in flight.

The projectile course correction means conveniently comprises a pyrotechnic impulser operative through one or more ports in the projectile body.

The course correction signals are preferably referred to a common directio:ial reference signal generated at the control station and detected by each projectile in flight. The control station may convcniently provide a subsidiary reference to remove any ambiguity in the ccr-""'.on reference signal. The refercnce signal may be a planepolarised radio wave and the subsidiary reference a laser bear scattered from the sea surface below the projectile flight path; in this case each projectile is equipped ':ith a dipolar antenna for reference signal recce iron and an optical detector for laser beam detection; the projectile also contains a reference signal processing circuit to indicate a "vertically up" projectile attitude.

Ecch course correction signal preferably includes an indication of the time cf flight of the projectile to which that signal relates, and each projectile is then arranged to respond only to those course correction signals containing the appropriate time of flight. Jn this way projectiles may be addressed and guided separately in a single communications channel.

In order that the invention might be more fully understood, one embodiment thereof will now be described, by wi of example only, uith reference to the accompanying drawings, in which:- Figure 1 is a schematic functional diagram of a GLGP system of the invention, Figure 2 illustrates a ship-borne GLGP system incorporating a laser positions refrrcnce, Figure 3 and 4 are respectively sectional and side elevations of a small-calibre GLGP, Figure 5 is a functional block diagram of a projectile reference signal processing circuit, and Figure 6 illustrates reference signal processing by the cir@uit of Figure 5.

Referring to Figure 1, a gun 10 fires a series of projectiles 11a, 11b...........11n towards an aerial target 12 initially (time t=ta) at 12a and later (time t=tb) at 12b. The target 12 executes evasion manoeuvres between 12a and 12b as indicated by a target track 13.

The gun 10 and projectiles 11 are directed by a control station indicated generally by 14. The g'dn 10 receives target range, height and bearing information from a target prediction device 15. A tracking device 16 tracks the projectiles 11 and target 12 by means of respective antennae 17 and 18. The tracking device 16 supplies target position information to th prediction device 15 and projectile position information to a projectile position predictor 19. A projectile manoeuvre computer 20 receives projectile and target data and prediction from the predictor 19, the tracking device 16 and the target prediction device 15.The computer 20 supplies course correction signals to a command transmitter 21 for onward transmission to the projectiles 11. The computer 20 includes a projectile time-of-flight clock (not shown) for rnitoring the instantaneous time of flight of each projectile 11. The control station 14 includes a stabilised radio frequency transmitter 22 and an antenna 23 to transmit a plane-polarised positional reference signal to eact projectile.

Preferring now also to Figure 2, the control station 14 and gun 10 are located aboard a ship 24. A laser 25 is mounted on a ships mast 26, and is arranged to illuminate the sea surface at 27 below the projectile 11. The laser beani 28 is arranged so that it does not interscct the projectile track 29 from the gun 10 (although this is not apparent in Figure 2). The projectile 11 receives laser light indicated by arrows 30 scattered from the sea surface 27.

Referring now also to figures 3 and 4, each projectile or GLGP 11 has a nose region 31 containing a solid rod target penetrator 32 and a course correction computer 33. The cor'puter 33 incorporates (not shown) a time of flight clock and a reference signal processing circuit (as will be deseribed below). The projectile 11 has a midsection 34 containing guidance means comprising a multi-port pyrotechnic impulser 35. The impulser 35 is operative to furnish a transverse impulse via any one of four ports 36 set at 90 intervals around the body of the projectile 11.The projectile 11 also has a tail section 37 including a slipping obturator 38 for gun barrel contact, a radio receiver 39 and power supplies 40. The tail section also includes an optical detector 41 for detecting sea-seattered laser light, radio receiving antennae including a dipole and indicated generally b 4k, and wrap-around stabilisation fins 43 (shown deployed).

The antennae 42 provide for reception of course correction and reference signals.

Referring now also to Figure 5, the projectile manoeuvre computer 20 includes A reference signal processing circuit indicated generally by 50 for providing a datum for projectile guidance. The above-mentioned dipole antenna 42 and radio receiver 39 are connected to L phase-locked oscillator 51. The oscillator 51 is connected to a divide-by-two circuit 52 and thence to phase adjust and processing circuits 53 and 54 respectively. The optical detector 41 is connected to an applil-ier 55 arid thence to a processing circuit 55 controlling the operation of the phase-adjust circuit 53.

The GLGP system illustrated in Figures 1 to 5 operates as follows.

The control station 14 acquires and tracks the target 12 by means ol the antenna 18 of the tracking device 46. The gun 10 is aimed at the target's future position as indicated by the prediction device 15, and commences firing the series of projectiles 11a, 11b........11n.Each projectile ii is largely decoupled from the gun barrel rifling by the slipping obturator 38, but retains residual spin in the order of tens cf revolutions per second. The fins 43 deploy as each projectile 11 leaves the gun 10. The projectiles are each tracked by the antenna 17, and the target and projectile predictors 15 and 19 extrapolate the respective trajectories to furnish mise distance and bearing data to the projectile manoeuvre computer 20.The computer 20 has algorithms to compute the timing and direction of the ryrotechnic impulse required to cerrect ti.e course of each projectile and to minimise or clininate the target !iS distance.

The computer 20 outputs a control word incorporating the tine of flight of the rolevant projectile 11 and the appropriate timing and direction of the impulse to be supplied by the pyrotechnic impulser.

The course correction is expressed in terms of the initiation time of the impulser and the angle to the vertical of the impulser port at initiation. The reference from which the vertical is obtained is derived from a combination of the plane-polarised reference signal transmitted by the control station antenna 23 and the sea-scattered laser light detected by the projectile@s optical detector 41.

5 Referring now to Figure 6, there are shown @mplitude / time graphs of signals (A) to (G) inclusive appearing in the reference signal processing circuit 50. The dipole antenna 42 and receiver 39 detect the plane-polarised reference signal transmission from the transmitter 22 of the control station 14. Since the projectile 11 and antenna ',t2 have residual spin as described earlier, the detecied reference signal (A) varies sinusoidally with a maximum value occurring time per revolution as the antenna 42 rctates with respect to the polarised signal.The reference signal (A) is fed to the phase-locked oscillator 51 which avoids difficulties with signal fading, and is then divided by two to produce signal (C). At t this point, the reference signal has a two-level phase ambiguity since it doer; not distinguish between "vertically up" and "vertically down". The ambiguity is removed by the laser sea illumination detected by the optical detector 41 and amplifier 55, which produce signal (F) comprising a series of pulses each corresponding to detector 41 iu a vertically down attitude.Signal (F) is converted to a serre.' of narrow spikes (G) which ale employed for phase adjustment of (ç) to provide (D). Signal (D) then provides m maxima each indicating a "vertically up" attitude for the projectile, corresponding to the detector 41 pointing vertically down, and (D) is processed to yield (E), a series of spikes each occurring at the "vertically up" attitude.

The projectile's receiving antenna 42 receives the control eord transmitted from the control station's projectile manoeuvre computer 20, and routes it to the course correction computer 33. The computer 33 compare the time of flight portion of the control word with that indicated by its internal clock. If the two are identical, the computer 33 selects the port 36 through which the course correction impulse is to be delivered, and initiates firing at the correct moment in the spin cycle indicated by reference signal (E) The impulse provided by the impulser changes the course of the projectile 11 and reduces targt miss distance.

If thc control word contains a time of flight different to that indicated by the projectile's internal clock, the projectile computer 33 ignores the course correction instruction. In this way, each course correction is made spacific to a particular projactile.

Claims

1. A gun launched guided projectile system (GLGP)comprising a projectile launching gun, a control station located remotely from the projectiles and associated with the gun and being adopted to track targets and the projectiles and to supply the projectiles with course correction signals for target aiming, and a supply of projectiles having course correction means responsive to the course correction signals.

2. A GLGP system according to claim 1 wherein the control station included means for tracking targets and in-flight projectiles, means for predicting future target and projectile positions, a computer for calculating projectile course corrections and means for transmitting course correction signals to the projectiles in flight.

3. A GLGP system according to claim 1 or claim 2 wherein the course correction signals are referred to a common directional reference signal generated at the control station and detcoted by each projectile in flight.

4. A GLGP system according to claim 3 wherein a subsidiary reference signal is generated by the control station to avoid any ambiguities in the common reference signal.

5. A GLGP system according to claim 3 wherein the common directional reference signal comprises a plane-polarised radio wave.

6. A GLGP system according to claim 5 wherein the projectile is equipped with a dipole antenna for common reference signal reception.

7. A GL5? system according to claim 4 wherein the subsidiary reference signal comprises a laser beam scattered from the sca surface below the projectile flight path.

8. A GL3P system according to claim 4 wherein the projectile is equipped with an optical detector for laser beam detectioli.

9. A GLGP system substantially as herein described with reference to the drawings.

9. A GLGP system according to claim 4 wherein the projectile ineorporate a reference signal processing circuit to provide an orientation reference for the pro;jetile.

10. A GLGP system according to any one of the preceding claims wherein the projectile course correction means comprises a pyrotechnic impulser through one or more ports in the projectile body.

11. A GLG system according to any one of the preceding claims wherein each course correction signal includes an indication of the time of flight of the projectile to which that signal relates, and each projectile is arranged to respond only to those course correction signals containing the appropriate time of flight so that many projectiles may be addressed and guided separately in a single communications channel.

12. A GLGP system substantially as herein described with reference to the drawings Amendments to the claims have been filed as follows CLAIMS 1. A gun launched guided projectile system (GLGP) comprising: a projectile launching gun; a control station located remotely from the projectiles and associated with the gun and including means for tracking targets and in-flight projectiles, means for predicting future target and projectile positions, a computer for calculating projectile course corrections and means for transmitting course correction signals to the projectiles in flight; means to generate a polarised reference signal for detection by each projectile in flight; means to generate a subsidiary reference signal for detection by each projectile to avoid any orientation ambiguities in the polarised signal; and a supply of projectiles have course correction means responsive to the correction signals and to the polarised and subsidiary reference signals.

2. A GLGP system according to claim wherein the polarised reference signal is a plane-polarised radio wave.

3. A GLGP system according to claim 2 wherein the projectile is equipped with a dipole antenna for reception of the polarised reference signal.

4. A GLGP system according to any one of claims 1 to 3 wherein the subsidiary reference sign comprises a laser beam scattered from the surface below the projectile flight path.

5. A GLGP system according to claim 4 wherein the projectile is equipped with an optical detector for laser beam detection.

6. A GLGP system according to any one of claims 1 to 5 wherein the projectile incorporates a reference signal processing circuit to provide an orientation reference for the projectile.

7. A GLGP system according to any one of the preceding claims wherein the projectile course correction means comprises a pyrotechnic impulser selectably connectable to one or more ports in the projectile body.

8. A GLGP system according to any one of the preceding claims wherein each course correction signal includes an indication of the time-of-flight of the projectile to which that signal relates, and each projectile includes a time-of-flight clock and is arranged to respond only to those course correction signals containing the appropriate time of flight so that many projectiles may be addressed and guided separately in a single communications channel.