GB2257237A

GB2257237A - Projectile launching

Info

Publication number: GB2257237A
Application number: GB8133576A
Authority: GB
Inventors: William Thoby Fisher
Original assignee: Baj Ltd
Current assignee: Baj Ltd
Priority date: 1981-11-06
Filing date: 1981-11-06
Publication date: 1993-01-06
Anticipated expiration: 2001-11-06
Also published as: GB2257237B

Abstract

A projectile launch system, particularly for launching decoys from ships comprises a closed-end launch tube (1), a projectile (2) in the tube, and a launch rocket (6) behind the projectile having a diameter substantially smaller than those of the tube and the projectile, a thrust diaphragm plate (9) being rigidly secured to the forward end of the rocket. Preferably the launch rocket burns for only about 0.18 second and separation between the rocket and the projectile occurs shortly after the rocket leaves the launcher tube. During launch, pressure builds up behind the diaphragm plate (9) but as soon as the rocket (6) leaves the launch tube (1) its unaerodynamic shape causes it rapidly to fall while the projectile (2) continues along its trajectory. <IMAGE>

Description

PROJECTILE LAUNCHING This invention relates to the launching of projectiles and is particularly concerned with the launching of projectiles containing payloads of a non-explosive nature. The invention is particularly but not exclusively applicable to the launching of a projectile containing means for deceiving an attacker of a ship. Ships may be attacked by guided weapons which locate and home on the ship by one or more of a number of detecting means such as radar and infrared sensing. In order to reduce the number of hits by such guided weapons it has been proposed to distribute around the ship a number of decoys offering characteristics which will be sensed by the guided weapons which will thus be confused into striking a decoy rather than the ship.

Such decoys to be effective have to be deployed in fairly large numbers and a simple launching system is required.

According to the present invention a projectile launch system comprises a launch tube, a projectile located within the tube and positioned to the rear of and in contact with the projectile, a launch rocket having a diameter which is substantially less than that of the launch tube and the projectile and having a thrust diaphragm plate whose diameter is greater than that of the rocket but smaller than that of the launch tube. Preferably the plate is rigidly secured adjacent the forward end of the launch rocket and the launch rocket is not positively attached to the projectile but may be located at the rear thereof by, for example, a loose spigot and socket fitting.

Preferably the motor of the launch rocket is constructed to burn for less than 0.5 seconds, more preferably less than .25 seconds, the preferred time being approximately .18 seconds. With this arrangement separation of the launch rocket from the projectile will occur shortly after the launch rocket leaves the launcher tube.

The rear end of the launcher tube may be totally closed but is preferably at leas t partially closed and may contain a vent to allow the escape of some but not all of the combustion gases from the launch rocket during launching. The effect of the diaphragm plate and the at least partially closed end of the launch tube is that the combustion gases, from burning of the launch rocket during launch,build up pressure behind the diaphragm plate and the resulting pressure differential across the plate provides thrust which is additional to the thrust produced by the pure rocket effect.

The invention may be carried into practice in various ways but two projectile launching systems embodying the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in diagrammatic form the first launching system; Figure 2 shows the trajectory of the projectile and the launch rocket; Figure 3 is a detail to an enlarged scale of the forward end of the booster rocket and the rearward end ofthe projectile of the second projectile launching system; and Figure 4 is a diagrammatic half cross-section on the line IV-IV in Figure 3.

The launching and projectile system shown in Figure 1 comprises a launch tube 1 which is only one of a battery of such launch tubes arranged side by side.

The launch tube contains a projectile 2 having folded fins 3 at the rear on which runners 4 are formed, these runners engaging the inner surface of the tube 1 to guide the projectile in its travel along the tube during launch. The projectile 2 carries further runners 5 slightly forward of its mid-point, these runners being either secured permanently to the projectile or being in the form of a sabot which is shed shortly after the projectile leaves the launch tube.

Located behind the projectile 2 is a launch rocket 6 of a diameter which is very substantially less than that of the projectile. The rear end of the launch rocket carries legs 7 with runners 8 to guide the launch rocket during launch. Adjacent the forward end of the launch rocket is a cone shaped diaphragm plate 9 which is rigidly secured to the launch rocket and which has a diameter which is approximately 1i times that of the projectile and is very slightly less than that of the launch tube. The forward end of the launch rocket is formed as a spigot 10 which fits loosely in a socket 11 at the rear of the projectile.

Operation of one particular example of the launch system is as follows. The launch tube has a diameter of 5 inches and the projectile has a length of one metre and a weight of 66 lbs. On firing of the launch rocket, thrust will be developed to drive the launch rocket and hence the projectile along the launch tube.

The combustion gases from the launch rocket will be trapped in the rear end of the launch tube so that pressure will build up to approximately 50 pounds per square inch behind the diaphragm plate and thus develop 1000 lbs of thrust which may be four times the rocket thrust. The launch rocket is constructed to burn for .18 seconds and will substantially have burned out shortly after the projectile and launch rocket have left the launch tube. Because of the unaerodynamic shape of the launch rocket it will rapidly fall into the sea about 150 metres from the ship as indicated by the trajectory 12 in Figure 2.

The projectile on the other hand will continue along its trajectory 13 and will fall into the sea approximately 1.2 kilometres from the ship. There it will float and the payload will be deployed. The payload may include a sea anchor together with a floatation device and the decoy means such as an infrared source or radar reflector.

Figures 3 and 4 show a second launching system in diagrammatic form and it should be noted that in Figure 3 one of the folding fins 23 of the projectile is shown extended although of course it would not be so extended when the projectile is within the launch tube. In the arrangement shown in Figures 3 and 4 there is a launch tube 21 containing a projectile 22 having folding fins 23 at the rear. The projectile carries runners which are not shown to enable it to travel smoothly up the launch tube.

Located behind the projectile 22 is a launch rocket 26 of a diameter which is subtantially less than that of the projectile. The rear end of the launch rocket carries legs. with runners which are not shown. Adjacent the forward end of the launch rocket is a dish-shaped diaphragm plate 29 which is rigidly secured to the launch.rocket and which has a diameter which is approximately 1i times that of the projectile and is only slightly less than the internal diameter of the launch tube. At the forward end of the launch rocket is an ignition system 31 to which a firing cable 32 leads.

The side wall 33 of the projectile extends rearwardly beyond the rear wall 34 closing the payload space of the projectile to form a socket 35 into which fits a spigot 36 formed at the outer end of a cup-shaped element 37 secured to the forward end of the launcher rocket.

As can best be seen from Figure 4, the rear end of the projectile carries four guidance fins 23 each of which is arcuate in cross-section and is hinged along one longitudinal edge to a bracket 38 on the projectile. When the projectile is in the launch tube the fins are wrapped around the projectile as indi cated in Figure 4 but once the projectile has left the launch tube the fins are deployed into positions in which they extend away from the axis of the rocket as indicated at the top of Figure 3.

Claims

1. A projectile launch system comprising a launch tube, a projectile located within the tube and positioned to the rear of and in contact with the projectile, a launch rocket having a diameter which is substantially less than that of the launch tube and the projectile and having a thrust diaphragm plate whose diameter is greater than that of the rocket but smaller than that of the launch tube.

2. A projectile launch system as claimed in Claim 1 in which the thrust diaphragm plate is secured to the launch rocket adjacent the forward end thereof.

3. A projectile launch system as claimed in Claim 1 or Claim 2 in which there is no positive attachment between the projectile and the launch rocket.

4. A projectile launch system as claimed in Claim 3 which includes a loose spigot and socket connection between the projectile and the launch rocket.

5. A projectile launch system as claimed in any of the preceding claims in which the launch rocket is constructed to burn for less than 0.5 seconds.

6. A projectile launch system as claimed in any of Claims 1 to 4 in which the launch rocket is constructed to burn for less than 0.25 seconds.

7. A projectile launch system as claimed in Claim 6 in which the launch rocket is constructed to burn for approximately 0.18 seconds.

8. A projectile launch system as claimed in any of the preceding claims in which the rear end of the launcher tube is closed.

9. A projectile launch system as claimed in any of Claims 1 to 7 in which the rear end of the launcher tube contains a vent.

10. A projectile launch system substantially as described herein with reference to Figures 1 and 2 or to Figures 3 and 4 of the accompanying drawings.

11. A projectile launcher comprising a battery of a plurality of projectile launch systems arranged side by side, each projectile launch system being as claimed in any one of the preceding claims.