GB2192976A

GB2192976A - Aerial load assemblies

Info

Publication number: GB2192976A
Application number: GB08616563A
Authority: GB
Inventors: John Stephen Lingard
Original assignee: GQ Defence Equipment Ltd
Current assignee: GQ Defence Equipment Ltd
Priority date: 1985-07-09
Filing date: 1986-07-08
Publication date: 1988-01-27
Also published as: GB8616563D0; GB2192976B

Abstract

An aerial load assembly 10 comprises a load 11 which is required to descend to and take up an upright disposition on a substantially level surface and a balloon device 12 secured to the load 11 and so shaped and dimensioned in relation to the load 11 as when inflated to make the assembly 10 unstable on the receiving surface in all dispositions of the load 11 except when it occupies the upright disposition. The load assembly 10 may comprise a ground mine 11 and be launched in the collapsed condition from a ground launcher. Air scoops 19 direct air into valve-controlled inlet ports 20 for ram-air inflation of the balloon during its descent. Upon landing with the weight vector (26) through the centre-of-gravity (24) of the mine lying outside the contact base (29-30) of the assembly with the ground surface (25), the assembly will roll until the forward end 13 of the mine (11) rests on the surface (25). <IMAGE>

Description

SPECIFICATION Aerial load assemblies The present invention relates to aerial load assemblies and is particularly although not exclusively concerned with an assembly discharged into the air and having an aerial load required to be deposited on the ground in a predetermined disposition relative to the ground.

A proposal has been made for the aerial deployment of ground mines in which the mines are discharged into the air by a ground launcher for descent to the ground at locations remote from the launching site. The deployment of mines in this way has however a disadvantage that the mine may take up any one of a number of incorrect dispositions on the ground following impact and its functioning adversely affected as a result.

It is an object of the present invention to provide a ground mine assembly by the use of which the above-mentioned disadvantage can be avoided.

In the above proposed aerial deployment of ground mines, there is a further disadvantage that the functioning of the mine may be adversely affected by its high impact velocity with the ground.

It is another object of the present invention to provide a ground mine assembly by the use of which both the above-mentioned disadvantages can be avoided.

It has hitherto been proposed for low altitude delivery of bombs to a target from an overflying aircraft to provide on the bomb a decelerator device which decelerates the bomb in its descent to the ground, thereby to ensure safe separation of the aircraft from the ground burst of the bomb. To improve the performance and andrhance the delivery of the bomb it has furthermore been proposed to use a decelerator device in the form 6f a ram-air inflated balloon which is automatically deployed from the aft end of the bomb following discharge of the bomb from the aircraft and which upon inflation so increases the aerodynamic drag on the bomb as to cause the bomb to follow a predetermined favourable trajectory to the ground. Results of tests on the balloon decelerator device have also indicated that it could be used for aerial delivery of stores and equipment.

The balloon decelerator device hitherto proposed comprises a centre tube for attachment coaxially to the aft end of the bomb, a forward balloon surface extending rearwardly and outwardly from the centre tube to a point of maximum diameter where it is joined to a reentrant rear balloon surface which extends inwardly and forwardly to the aft end of the centre tube. The forward balloon surface is provided with valve controlled air inlets arranged in spaced relation around the balloon to produce ram-air inflation of the balloon during descent of the bomb.

Although the balloon decelerator device hereinbefore described could be used in the aerial delivery of loads other than bombs as a means of decelerating the load to a predetermined safe impact velocity, the need arises from time to time for the aerial delivery of a load in such a manner that the load comes to rest on the ground in a predetermined upright disposition or that there is a high probability that the predetermined upright disposition is attained.

It is yet another object of the present invention to provide an aerial load assembly by the use of which the above-mentioned need can be met.

According to the present invention, there is provided an aerial load assembly comprising an aerial load which is required to descend to and take up a predetermined disposition on a level or substantially level receiving surface and a balloon device secured to the load and so shaped and dimensioned in relation to the load as when inflated to make the assembly unstable on the receiving surface in all dispositions of the load except when the load occupies the predetermined disposition.

In one embodiment of the invention as hereinafter to be described the balloon is secured to an aft end of the load required to be uppermost in the predetermined disposition on the receiving surface and is formed by a frusto-conical forward balloon surface extending rearwardly and outwardly from the aft end of the load to a region of maximum diameter where it joins a hemispherical rear balloon surface.

In a further embodiment of the invention hereinafter to be described the balloon is formed by a forward balloon surface which extends from the aft end of the load forwardly and outwardly to a region of maximum forward extent and then rearwardly and outwardly to a region of maximum diameter where it joins a rear balloon surface which extends rearwardly as a paraboloid of revolution. Preferably, the region of maximum forward extent lies in the same plane or in substantially the same plane as the forward end of the load required to contact the receiving surface in the predetermined position of the load whereby the load is stabilised by the balloon in the predetermined disposition.

In yet another embodiment of the invention hereinafter to be described the balloon is formed by a forward balloon surface which extends from the aft end of the load rearwardly and outwardly as an ellipsoid of revolution to a region of maximum diameter where it joins a rear balloon surface which extends rearwardly as a paraboloid of revolution.

Preferably, the aerial load assembly is arranged to be discharged into the air with the balloon in a deflated condition and the balloon is arranged to inflate by ram air inflation during its flight through the air. The balloon may conveniently include one or more air inlet ports for ram inflation and the or each inlet port may be provided with one-way valve means which close when the assembly reaches a predetermined velocity in flight or when it impacts with the receiving surface and the ram air supply pressure collapses. An air scoop may be provided in the region of each inlet port to direct air into the inlet port. The air scoops may furthermore be so disposed and shaped as to control boundary layer separation and to stabilise the balloon during its flight in the air.The balloon is preferably so constructed as when inflated to decelerate the load during its descent to a predetermined safe impact velocity with the receiving surface.

Where the load is required to take up a predetermined disposition on a level or substantially level ground surface, the balloon device is arranged to be of such configuration as when inflated to cause the weight vector acting through the centre of gravity of the assembly to lie outside the base of the assembly in contact with the ground surface except when the load is in the predetermined disposition. The balloon is furthermore preferably so shaped and constructed and so inflated as to absorb rebound of the load following its impact with the ground surface.

In accordance with the embodiments of the invention hereinafter to be described, the load is a ground mine of cylindrical form with a length shorter than its diameter, and the weight distribution of the mine is such that its centre of gravity lies along the cylinder axis approximately midway between the aft end and a forward end of the mine which take up a lowermost disposition on the ground surface. Preferably, the mass of the balloon in relation to the mass of the mine is such that the centre of gravity of the assembly lies on the axis of the mine substantially midway between its aft and forward ends.

Where the load is a ground mine, the assembly may be arranged for discharge into the air from a ground launcher with the balloon in a collapsed and folded condition at the aft end of the mne. The assembly may with advantage be discharged into the air in a stack comprising a plurality of assemblies which are arranged to separate sequentially from the stack during flight of the stack through the air. The stack of mines may be contained in and form part of an artillery shell or a rocket propelled device.

Where the load is a ground mine, the balloon may be arranged to deflate a predetermined time after the mine has taken up the predetermined disposition on the ground surface. Furthermore, the balloon surface may be such as to provide an effective camouflage for the mine when the balloon deflates over it.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a schematic perspective view from below of an aerially deployed ground mine assembly according to a first embodiment of the invention; Fig. 2 is a schematic side elevation of the assembly shown in Fig. 1; Fig. 3 is a schematic representation showing the descent path of the ground mine assembly shown in Fig. 1 and illustrating the assembly at successive positions during its descent to the ground and its final disposition on the ground; Figs. 4, 5, 6 and 7 are schematic side elevations of the assembly shown in Fjg. 1, illustrating the disposition of the weight vector of the assembly in various dispositions of the assembly on the ground; and Figs. 8 and 9 are schematic side elevations of ground mine assemblies according to second and third embodiments of the invention.

Referring first to Figs. 1 and 2 of the drawings, a ground mine assembly 10 comprises a ground mine 11 and an inflatable balloon 12 which serves to decelerate the mine in its descent to the ground following discharge into the air from a ground launcher and to bring the mine on the ground to a predetermined upright disposition in which the forward end 13 of the mine 11 rests on the ground.

As will be seen, the mine 11 is of cylindrical form with a length which is short in relation to its diameter. The weight distribution of the mine is such that its centre of gravity lies along the cylinder axis approximately midway between the aft end 14 of the mine and the forward end 13.

The balloon 12, which is shown in its fully inflated condition in Figs. 1 and 2, comprises a frusto-conical forward balloon surface 15 which is secured at its foremost periphery to the aft end 14 of the mine 11 and which extends outwardly and rearwardly to a region of maximum diameter of the balloon where it is joined along a join line 17 to a hemispherical rear balloon surface 18 which completes the balloon structure. Four air scoops 19 shown distended in Figs.

1 and 2 are arranged in equi-angularly spaced dispositions around the balloon and serve to direct air into valve controlled inlet ports 20 in the forward balloon surface 1 5 for ram-air inflation of the balloon during descent of the assembly. Each of the inlet ports 20 is equipped with a one-way valve which closes when the assembly reaches its terminal velocity in flight or when it impacts with the ground and the ram-air supply pressure collapses. The balloon 12, which is made of a fabric, is packed in a collapsed and folded condition at the aft end 14 of the mine 11.

Referring now to Fig. 3 the mine assembly 10 described with reference to Fig. 1 is shown in successive positions in a descent path following discharge into the air from a ground launcher.

At position A, the mine assembly 10 comprises the mine 11 and the balloon 12 in its collapsed and stowed condition. The balloon 12 then commences to deploy from the aft end of the mine 11 as shown at position B. At this time the air scoops 19 distend for ram-air inflation of the balloon 12. At position C, the balloon 12 is partially inflated and the assembly decelerates with a consequent increase in the trajectory gradient. At position D, the balloon 12 is fully inflated and applying maximum aero-dynamic drag to the assembly. By the time position E is reached the assembly 10 with its mine 11 has reached a predetermined safe impact velocity. As a result of the deceieration of the assembly 10, the trajectory it follows steepens to produce a high impact angle with the ground.The assembly 10 on impact with the ground 22 strikes the inclined ground surface 23 and by virtue of the momentum of the assembly rolls down the inclined surface 23 through positions F, G and H, finally to take up the position J with the mine 11 in an upright disposition with the forward end 13 on the level ground surface. Reduction in the velocity of the assembly to its terminal velocity in flight or on impact with the ground causes the inlet valves 20 automatically to close following a collapse of ram-air pressure and to remain closed so that the balloon 12 remains inflated during the rolling motion of the assembly and the bringing of the mine 11 to the upright disposition shown at position J.

A bleed valve (not shown) may be provided in the balloon surface for effecting a slow deflation of the balloon when the mine assembly is at rest on the ground so that the balloon 12 collapses over the mine 11 as illustrated at position K.

It will be appreciated that the flight path of the mine assembly 10 shown in Fig. 3 is purely.

diagrammatic and shows only the terminal part of the flight path of the assembly discharged into the air from a remote ground launcher (not shown). In particular, the position A of the assembly 10 at which the balloon 12 commences to deploy is shown at the commencement of descent.

Deployment of the balloon 12 may, however, take place at any point in the flight path depending on the overall trajectory required.

The mine assembly hereinbefore described is found to be particularly suitable for deployment of ground mines in which the mines are discharged into the air in a stack from a ground launcher and separate sequentially from the stack during flight of the stack through the air. In this method of deployment each mine assembly 10 would automatically separate in turn from the stack and follow the descent stages illustrated in Fig. 3. The point in the flight path of the stack at which successive mine assemblies are separated would determine the flight path of the assembly and its descent trajectory to the ground.

Referring now to Figs. 4 to 7, as the mass of the balloon 12 is small in relation to the mass of the mine 11, it can be assumed that the centre of gravity of the assembly 10 lies on the axis of the cylindrical mine 11 substantially midway between its ends 13 and 14 as represented by the reference 24. In the position shown in Fig. 4, with the balloon surface 18 engaging a horizontal ground surface 25 and with the weight vector 26 acting through the centre of gravity 24 the assembly 10 is clearly unstable with the weight vector 26 lying outside the contact base of the assembly with the ground surface 25. As a result, the assembly 10 will roll counterclockwise through the position shown in Fig. 5 to the position shown in Fig. 6 in which the mine 11 and balloon 12 engage the horizontal ground surface 25.In this disposition of the assembly 10, the weight vector 26 still lies outside the base of the assembly determined by contact point 29 of the mine 11 and contact point 30 of the balloon 12. As a result, the assembly 10 rolls further counterclockwise to the position shown in Fig. 7 in which the forward end 13 of the minei 11 rests on the horizontal ground surface 25. The assembly 10 is furthermore unstable for all other dispositions in which the hemispherical rear balloon surface 18 contacts the ground surface 25, with the result that the assembly rolls either clockwise or counterclockwise.

It will be apprecia,ted that the mine 11 will take up an upright disposition with its cylindrical axis vertical when it comes to rest on a flat, horizontal ground surface. Where the terrain is broken up or inclined at a small angle to the horizontal the balloon 12 will bring the end 13 of the mine 11 into engagement with the ground surface without necessarily bringing it to a completely upright disposition. Where the terrain is steeply inclined to the horizontal, it will, however, usually be found that the assembly has sufficient momentum to cause it to roll down the incline irrespective of the disposition of the mine on impact and the the assembly would then continue to roll, as illustrated in Fig. 3, until it comes to rest on a level or near level ground surface.For most purposes it would be considered acceptable that the mine 11 will take up an upright or nearly upright disposition.

A requirement for some mine devices is that the mine be deposited on the ground in an upright disposition or within predetermined limits of the upright disposition. There may further more be a requirement that there is a 75% probability that each mine dropped on to a rolling terrain on hard or soft surfaces will be oriented upwards within say a half radian of the vertical.

Where a mine assembly as hereinbefore described is employed there must also be a high probability (possibly 95%) that the balloon will operate. correctly on both hard and soft ground surfaces and that the balloon does not adversely affect to any significant extent any camouflage or countermeasure resistance properties of the mine. Furthermore, there must be a high probability of the mine functioning correctly following impact at the highest impact velocities and at the worst angles of inclination with the ground surface likely to be expected from use of a variety of delivery means. Preferably, there should be at least a 95% probability of correct functioning for pasture land and an 80% probability for hard ground surfaces. These can be achieved with an aerially deployed mine assembly hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings.

It will be appreciated that the disposition of the balloon 12 in relation to the mine 11, the shape of the balloon 12 and the size and disposition of the air scoops 19 are critical for achieving proper ram-air inflation of the balloon and in flight stability of the assembly.

Although four air scoops with associated inlet valves are used in the embodiment of the invention hereinbefore described any other number of equally spaced scoops greater than two may be used provided they achieve the above described results. The rate of inflation of the balloon 12 may of course be changed by varying the size of the inlet-ports and their associated one-way inlet valves. Any flexible material may be used for the construction of the balloon or the scoops provided it is substantially air impervious. The material may for example be a nylon fabric and the balloon constructed from preformed gores.

It has furthermore been found that the balloon 12 of the assembly 10 has the further advantage of reducing rebound of the mine following its impact with the ground. In addition it has been found that the air scoops 19 in addition to maintaining inflation pressure act to control boundary layer separation and hence serve to stabilise the balloon itself during the descent of the assembly.

The terminal velocity of descent of the assembly hereinbefore described may be calculated from the following equation:

where m5 = mass of balloon and load g = gravitational constant < = air density CD = drag coefficient and S = projected area of the balloon Clearly, any, desired rate of descent can be achieved for loads of any mass simply by changing the size of the balloon.

By applying appropriate camouflage to the balloon surfaces an effective camouflage of the mine 11 is obtained if the balloon 12 is arranged finally to deflate over the mine. This clearly has a particular advantage in military situations where enemy observation of the mines should be avoided. Alternatively, means may be provided for automatic release of the balloon 12 from the mine so that the balloon blows away from the area rather than collapsing on the mine.

Conversely, the balloon surfaces may be in colours contrasting with the terrain and the balloon arranged to deflate over the load so as to provide immediate recognition of a load.

It will be appreciated that an aerial load assembly according to the invention may be used for depositing a load appropriately oriented on a water surface, For example, the load may be a sonobuoy required to be dropped from an aircraft overflying water and requiring for its proper functioning to take up a floating disposition on the water in which it its upright.

While the balloon 12 of the aerial load assembly hereinbefore described with reference to Figs.

1 to 7 has proved successful for placement of a mine, it will be appreciated that balloons of other configurations may alternatively be used for this application or for other applications. For example, the mine assembly illustrated in Fig. 8 comprises a ground mine 11 and a balloon 33 formed by a forward balloon surface 34 which extends from the aft end 14 of the mine 11 forwardly and outwardly to a region 35 of maximum forward extent and then rearwardly and outwardly to a region 36 of maximum diameter, where it joins a rear balloon surface 37 which extends rearwardly as a paraboloid of revolution. It will be seen that the region 35 lies approximately in the same plane as the forward end 13 of the mine 11.An assembly with a balloon 33 of this shape may be found advantageous where the mine itself or other load is not particularly stable in the upright position as the forward extensions of the balloon surface 34 would stabilise it in the upright disposition.

A further balloon configuration is illustrated in Fig. 9 where the forward balloon surface 38 conforms approximately to an ellipsoid of revolution and the rear balloon surface 39 conforms approximately to a paraboloid of revolution.

It is to be noted that with each of the balloon configurations illustrated in Figs. 8 and 9 the aerial load assembly is unstable for all dispositions of the mine 11 except that in which the forward end 13 of the mine 11 comes to rest on a level surface.

The ground launcher hereinbefore referred to may take many different forms. It may for example be a heavy duty short range launcher which is vehicle mounted or a light duty man portable launcher. The mine assemblies may be arranged to be fired from the launcher either singly or in a stack from which they sequentially separate during flight of the stack through the air. Where the mine assemblies are to be discharged as a stack, the stack may be fired contained in an artillery shell or in a rocket.

While the use of a ground based launcher has been described, it will be appreciated that the deployment of the mine assemblies in accordance with the invention could be carried out using a launcher mounted on a helicopter.

Claims

1. An aerial load assembly comprising an aerial load which is required to descend to and take up a predetermined disposition on a level or substantially level receiving surface and a balloon device secured to the load and so shaped and dimensioned in relation to the load as when inflated to make the assembly unstable on the receiving surface in all dispositions of the load except when the load occupies the predetermined disposition.

2. An assembly according to claim 1, wherein the balloon is secured to an aft end of the load required to be uppermost in the predetermined disposition on the receiving surface and is formed by a frusto-conical forward balloon surface extending rearwardly and outwardly from the aft end of the load to a region of maximum diameter where it joins a hemispherical rear balloon surface.

3. An assembly according to claim 1, wherein the balloon is secured to an aft end of the load required to be uppermost in the predetermined disposition on the receiving surface and is formed by a forward balloon surface which extends from the aft end of the load forwardly and outwardly to a region of maximum forward extent and then rearwardly and outwardly to a region of maximum diameter where it joins a rear balloon surface which extends rearwardly as a paraboloid of revolution.

4. An assembly according to claim 3, wherein the region of maximum forward extent lies in the same plane or in substantially the same plane as the forward end of the load required to contact the receiving surface in the predetermined position of the load whereby the load is stabilised by the balloon in the predetermined disposition.

5. An assembly according to claim 1, wherein the balloon is secured to an aft end of the load required to be uppermost in the predetermined disposition on the receiving surface and is formed by a forward balloon surface which extends from the aft end of the load rearwardly and outwardly as an ellipsoid of revolution to a region of maximum diameter where it joins a rear balloon surface which extends rearwardly as a paraboloid of revolution.

6. An assembly according to any of claims 2 to 5, wherein the aerial load assembly is arranged to be discharged into the air with the balloon in a deflated condition and wherein the balloon inflates by ram air inflation during its flight through the air.

7. An assembly according to claim 6, wherein the balloon includes one or more air inlet ports for ram inflation of the balloon during flight of the assembly through the air.

8. An assembly according to claim 7, wherein the or each inlet port is provided with one-way valve means which close when the assembly reaches a predetermined velocity in flight or when it impacts with the receiving surface and the ram air supply pressure collapses.

9. An assembly according to claim 8, wherein the balloon is provided with an air scoop in the region of each inlet port to direct air into the inlet port.

10. An assembly according to claim 9, wherein the balloon is made of a flexible material which is substantially air impervious.

11. An assembly according to claim 10, wherein the air scoops are so disposed and shaped as to control boundary layer separation and to stabilise the balloon during its flight in the air.

12. An assembly according to any of claims 2 to 11, wherein the balloon is so constructed as when inflated to decelerate the load during its descent to a predetermined safe impact velocity with the receiving surface.

13. An assembly according to any of claims 2 to 12, wherein the load is required to take up the predetermined position on a level or substantially level ground surface, and wherein the balloon is of such configuration as when inflated to cause the weight vector acting through the centre of gravity of the assembly to lie outside the base of the assembly in contact with the ground surface except when the load is in the predetemined disposition.

14. An assembly according to claim 13, wherein the balloon is so shaped and constructed and so inflated as to absorb rebound of the load following its impact with the ground surface.

15. An assembly according to claim 13 or 14, wherein the load is a ground mine.

16. An assembly according to claim 15, wherein the mine is of cylindrical form with a length shorter than its diameter, and wherein the weight distribution of the mine is such that its centre of gravity lies along the cylinder axis approximately mid-way between the aft end and a forward end of the mine which is lowermost in the predetermined disposition on the ground surface.

17. An assembly according to claim 16, wherein the mass of the balloon in relation to the mass of the mine is such that the centre of gravity of the assembly lies on the axis of the mine substantially mid-way between its aft and forward ends.

18. An assembly according to claim 15,16 or 17, wherein the assembly is arranged for discharge into the air from a ground launcher with the balloon in a collapsed and folded condition at the aft end of the mine.

19. An assembly according to claim 18, wherein the assembly is discharged into the air in a stack comprising a plurality of assemblies which are arranged to separate sequentially from the stack during flight of the stack through the air.

20. An assembly according to claim 19, wherein the stack of mines is contained in and forms part of an artillery shell.

21. An assembly according to claim 19, wherein the stack is contained in and forms part of a rocket propelled device.

22. An assembly according to any of claims 15 to 21 , wherein the balloon is arranged to deflate a predetermined time after the mine has taken up the predetermined disposition on the ground surface.

23. An assembly according to claim 22, wherein the balloon surface is such as to provide an effective camouflage for the mine when the balloon deflates over it.

24. An assembly according to claims 15 to 22 wherein means are provided for automatic release of the balloon from the mine after the mine has taken up the predetermined disposition on the ground surface so that the balloon blows away from the area of the mine.

25. An aerial mine assembly substantially as hereinbefore described with reference to Figs. 1 to 7, 8 or 9 of the accompanying drawings.