CA1231861A - Inflatable decelerator - Google Patents

Abstract

INFLATABLE DECELERATOR

ABSTRACT

The present invention relates to a collapsible decelerator for aerial bombs launched from a high velocity vehicle and designed to provide a high drag stabilizer capable of withstanding release in airstream velocities moving at 2,600 feet per second. The deceleration includes a hollow inflatable star, the outermost points of which have hooded valve openings through which regulated airflow enters and inflates the star to decelerate the munition to which it is attached.

Description

123t861 l BACKGROUND OF THE INVENTION

-4 When a retarding mechanism and a body suspended therefrom are launched from an aircraft or missile at high speed, deployment 6 of a decelerator may cause a severe shock due to sudden 7 retardation. Such shocks are often sufficient to cause x structural failure of the retarding device or damage of the 9 payload to which it is attached. Prior art retarding devices lo utilize parachutes, metal fin stabilizers and ballute Il technology to decelerate bomblets in progressive steps and to l2 reduce the incidence of damage. A common difficulty with such 13 devices has been that excessive speed at the time of dispersal 14 often overstresses the decelerator and fails it. For example, s parachutes provide drag at speeds below 1,500 feet per second 16 but upon opening suddenly at high speed the lines tangle, l7 become disoriented or break. Parachutes are also unfit for use l8 in wooded areas since they get hung up in branches and shrubs, Is thus preventing the load from impacting the target.
2l Metal fin stabilizers provide acceptable deceleration where 22 release velocities are under 1,600 feet per second but often 23 structurally fail at higher speeds, and cause tumbling, t4 unstable trajectories and insufficient dispersion patterns 25 where wide scattering is desired.

27 The combination of a parachute and balloon referred to as 28 ballute technology such as taught in U.S. Patent No. 4,215,836 29 issued to the same inventor herein provides many advantages over the prior art. The invention in this case provides 31 further and significant improvements over the concept covered 3~ by the noted patent.

,.~ , Sb ; .,, . 1 , ,.s~.`3' 1 2 3 1 ~6 SUMMARY OF THE INVENTION

The present invention is directed to an inflatable decelerator for deployment with an attached load unit in an airstream comprising: an inflatable flexibly collaps-ible chamber of generally star shape form consisting of aplurality of radially outwardly projecting lobes in spaced-apart relationship to each other, said chamber in its inflated state having an essentially Elat upper surface and a conical lower surface, air inlet means including at least one air passage proximate the outer distal end of each said lobe, and air scoop means operatively related to each said air inlet and including an upstanding hood cover-ing said inlet and spaced-apart therefrom for capturing a portion of external airflow around said chamber and direct-ing said portion into said inlet to inflate said chamber.

The present invention is further direeted to a combina-tion deceleration and de-spin deviee for attaehment to a sub-munition, comprising: an inflatable starshaped chamber having at least three radially extending lobes and having in its inflated state an essentially flat upper surface and a eonieal lower surface, air inlet means on each of said lobes proximate the outermost ends thereof, and air scoop means operatively related to eaeh said air inlet means and including an upstanding hood around said inlet means and spaced-apart therefrom for capturing a portion of external airflow around said chamber and directing said portion into said inlet to inflate said chamber.

The present invention relates ts ballute technology which wil permit successful dispersion at speeds above 2,600 feet per second by providing air scoops which will assure proper inflation of the device and structural integrity. Following deceleration, the retarding device continues to function as a guidance and stabilizing device for a munition.

It is therefore an object of this invention to provide a novel high drag stabilizer attached to a munition so that improved reliability of operation is provided.

Another object of this invention is to provide a high drag stabilizer which can be economically constructed and can operate at speeds as much as 2,600 feet per second.

Still another object of this invention is to provide a high drag stabilizer which is attached to a munition and, upon deceleration to a preselected terminal velocity, becomes a stabilizing device.

These and other objects and many of the attendant advantages of the present invention will become apparent as the same becomes better understood from the following detailed description, taken in conjunction with the accompanying drawings.

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l BRIEF DESCRIPTION OF THE DRAWINGS

3 FIG 1 is a general perspective view, partly broken away, of 4 the inventive structure in this case;
s 6 FIG 2 is an isolated view of the decelerator device from 7 FIG l partly fragmented;

FIG 3 is a cross-sectional elevational view of the structure lo seen in FIG 1 but with the decelerator in a collapsed or Il folded state;

13 FIG 4 is a view similar to FIG 3 but showing multiple 14 bomblets in nested relationship within a rocket;
16 FIG 5 iS a side elevation of the structure seen in FIGo l;

l FIG 6 is an isolated view of the structure from FIG 5;

FIG 7 iS a graph depicting loss of combat effectiveness in 21 the structure of Figs 1 through 5 based on angular 22 displacement; and 24 FIG 8 is a general view of the structure from FI~s~ 1 t ough S just prior to impact with a target.

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l DETAILED DESCRIPTION OF THE INVENTION

3 Referring to the drawings, reference numeral 10 in FIG. 1 4 generally denoteF. a sub-munition assembly or combination in which a bomblet, sub-munition or other body 12 is securely 6 attached to a decelerator comprising inflatable hollow 1exible 7 chamber 14 by means of a connecting rod or shaft 16 which 8 junctions in any convenient manner such as suggested for nut 28 9 and load stem 30 disclosed in mentioned U.S. Patent No.
4,215,836.
ll 12 Sub-munition or bomblet 12 includes an outer substantially 3 cylindrical housing 18 with chamber 14 secured at one end l4 thereof and terminating in a lower edge 19 having a series of rectangular projections 20 and 22 in spaced-apart sequence as suggested by spaces 24 and 26. Housing 18 of bomblet 12 l7 contains all the essential components (not shown) necessary for x combat weapons of this type including an explosive mass, an l9 impact detonator and other sensor mechanisms adapted to arm and actuate the explosive. In addition, housing 18 includes inner 2l wall 28 forming a somewhat conical-shaped and concentric inner

2~ cavity or hollow storage space 30 volumetrically configured to 23 accommodate the size and shape of chamber 14 when the chamber 24 is in the collapsed or uninflated state. This permits the 2s sequential packing of multiple bomblet assemblies about a 26 longitudinal axis such as to occupy an elongate cylindrical .~ cket payload section in the manner suggested by JIG. 4.

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;, i ~2318~1 l With reference to FIG. 2, the decelerator 14 may be seen to 2 have a shape generally analogous to an essentially flat star

3 illustratively having three radially outward projecting lobes

4 or wings 32. The essentially star-shaped chamber 14 is s constructed by joining a flat top panel 34 to a slightly 6 rounded bottom panel 36 about their respective peripheries such 7 as by continuous stitching in the manner suggested by seam 38 x coextensive with the outer distal edges of both panels. Panel 36 contains sufficient material so as to form a slightly lo conical shape when chamber 14 is fully inflated such as 1l suggested by FIG. 1 wherein upper panel 34 is substantially 12 flat or planar while panel 36 provides deeper thickness at the 13 center of chamber 14 than at the outer extremeties of the lobes lo 32. Each of the lobes 32 i5 an elongated inflatable compartment contiguous with the axial center portion of chamber 16 14. the cutout areas between lobes 32 are of significance in the performance of the decelerator as discussed below.
l8 l9 Attachment of the chamber 14 to bomblet 12 is done by the use of plate 40 having a swedged miniature clinch nut 42 cemented 2l tc the inside of lower panel 36, while spacer ring 44 is 22 cemented to the outside of panel 36. The plate 40 and the 23 spacer ring 44 are also secured to each other by a plurality of 24 rivets such as 4 equidistantly spaced rivets of the type suggested by rivet 46.

27 Of critical importance to the invention concept in this case t8 is the addition of at least one hole proximate the outer distal 2~ edge of each lobe 32 as shown illustratively by hole 50 in FIG. 2. It is through the three holes thus formed that airflow 31 necessary for inflation of chamber 14 occurs. Since the launch 32 speed of the assembly 10 is based upon the operating 123186~

l characteristics of the bomb or missile from which it is 2 launched, the airflow rate into chamber 14 can be adjusted 3 according to the size of holes 50 in the lobes.

s Of particular and critical importance, along with the 6 starlike shape of chamber 14, is the use of scuppers or hoods 7 over each hole 50 such as scuppers 52 and 54 seen in FIGs. 1 8 and 2. Each of the three hoods or pockets forms an upstanding 9 covering over each of the holes 50 respectively, but spaced-o apart therefrom to engage or capture a small portion of the external airflow around chamber 14 and scoop such portion into 12 the pocket such that it will be confined and spilled or 13 otherwise directed into the hole 50 covered by the pocket.
14 Thus, each pocket as suggested by pocket 52 in FIG. 2 has an Is open end portion 56, a blind closure end portion 58, and side 16 portions 60 and 52 extending therebetween. These portions l7 comprise surfaces which slope from the open ended air inlet 18 area 56 toward blind terminus 58 from which there is no outlet 19 or escape, whereby airflow entering the inlet 56 is forced through hole 50 and thence into chamber 14.

22 The scooping action thus achieved by pockets 52 and 54, for 23 example, is especially significant in assuring reliable and 2~ effective operation of the decelerator in this case. As seen from FIGs. 3 and 4, the sub-munition assembly 10 prior to its 26 deployment in combat use is stored or stacked with decelerator 27 14 tightly folded and collapsed upon itself to form a high 28 density mass within the smallest possible space envelope. This 29 permits the highly compressed and compact mass of chamber 14 to fit in tightly and close intimate nested relationship within 31 concentrically formed cavity 30 at the centex of each bomblet 32 12. However, when the sub-munitions 10 are ejected into space .~ c.

l while moving at high speed such as 2,600 feet per second or 2 more, positive and forceful action is essential to assure that 3 the compact mass of collapsed chamber 14 will not remain stuck 4 together in a relatively solid ball, but will inflate and s become distended so that its decelerating and stabilizing 6 functions on bomblet 12 will occur.

8 The mentioned forceful and positive action to unfold and g inflate chamber 14 is achieved by the scuppers including items lo 52 and 54 described above. Thus, the chamber 14 when collapsed ll is folded in a manner so that one or more of the scuppers or 12 pockets such as items 52 and 54 are exposed on an exterior l3 surface of the folded mass. Upon deployment into a relatively 14 high speed mass of air, the hoods or pockets will initially Is engage and capture a portion of the air surrounding the mass, 16 and direct this portion into the chamber 14, which will then 17 begin to unfold and extend all of its lobes 32 radially 18 outward, in the same manner of a pilot chute dragging the main l9 canopy into an airstream during operation of a parachute.

21 The starlike form of chamber 14 provides very important 22 advantages not available from other chamber shapes such as 23 square or round. Thus, the lobes 3~, being arranged about a 24 center longitudinal axis, displace an impacting mass of air in a similarly arranged pattern between the lobes whereby balanced 26 aerodynamic forces about the noted axis invariably result.
27 This causes self correction of the position and direction of 28 movement of bomblet 12 to lessen or minimize wobbling, tumbling 29 or non-uniformity in its flight path such as would produce excessive scatter in a rocket payload comprising multiple 3l bomblets, misfires or duds due to angular misalignment of the 32 firing mechanism with respect to an impact surface at the "I, :, l target. While more than three lobes might achieve a 2 satisfactory result if arranged in the manner discussed above, 3 not less than three are necessary to provide the required 4 balance and three only are preferred.

6 While star-shaped chamber 14 provides significant 7 improvements over conventional decelerators regardless of the 8 shape or configuration of bomblet 12, it has been found particularly advantageous to provide bomblet 12 with a lower lo distal edge of non-uniform planarity as illustrated by castellated or scalloped edge 19. Thus, referring to FIG. 5, 12 arrow 64 denotes the path of movement of bomblet 12 during its 13 descent following deployment from a missile or artillery ll projectile. Arrows 66 denote the direction of the free us airstream relative to bomblet 12. Dashed lines 68 and 70 ~6 suggest tbe area of separation between airflow masses having l7 different characteristics due to aerodynamic interference from 8 bomblet 12. Thus, sustained impact of airflow 66 against the 19 lower end 19 of bomblet 12 will result in highly turbulent flow proximate surface 18 starting at uniform flow occurs in the 2l free airstream outside the masses of air characterized by these 22 flow conditions is suggested by lines 68 and 70.

24 Each of lines 68 and 70 may be seen to approach surface l at 25 vertically spaced-apart locations, since the turbulent effect 26 begins where free airstream 66 initially makes contact with 27 edge 19. Thus, line 70 extends generally upward from the 28 lowermost edge of downward projecting rectangle 22, forming an 29 enclosed angle 72 with surface 18. Line 68 extends at an angle 74 from the same surface, but at a higher location thereon, 31 notably 25 the top of space 24. While the angles 72 and 74 are 32 identical, their lateral distance, respectively, from vertical center line 76 axially through bomblet 12 differs. Distance 78 , may be seen to be noticeably longer than distance 80. The star 3 shape of chamber 14 is designed to take advantage of this flow 4 phenomena, since the outermost ends of each lobe on the star s are dimensioned so as to project beyond the turbulent flow 6 space in the manner illustrated by lobe 32 in FIG. 5 when 7 chamber 14 is fully inflated. Lobe 32 extends a radial 8 distance from axis 76 in excess of distance 80, whereby pocket 9 54 is situated in the free stream area outside of the turbulent lo area between lines 68 and 70.
Il The flow pattern thus suggested in FIG. 5 is shown in FIG. 6 3 which is a view seen from below FIG. 5 looking in the direction 14 of arrows 66. The dotted line as seen in FIG. 6 shows that the us shape of the flow pattern resulting from castellated contours l6 20, 28, 24 and 26, for example, follows essentially the same l7 contour or pattern as lobes 32. Thus, line 68 corresponds with 18 the portion of line 82 which is radially closest to center axis Is 76. This pattern results from the castellated contour of the lower distal edge of bomblet 12 and, in combination with the 21 star pattern of chamber 14, produces a stabilizing action which 22 avoids spinning of the sub-munition 10. If pockets 54 were 23 inside the turbulent space envelope or frusto-conical volume 24 defined by lines 68 and 70, chamber 14 would not inflate, but merely would flap about ineffectively.

27 FIG. 7 shows a graph of the effects of poor impact angle on 28 the letha]ity of bomblet 12, while JIG. 8 shows the angular 3l rameter to which the graph of JIG. 7 refer .., ;!

1 ~3 I g6 1 l In FIG. 8, reference numeral 94 denotes a target surface 2 which in some cases could be the ground and in other cases 3 might be an armored surface of a tank. Bomblet 12 could 4 contain a shaped charge for penetrating armor plate, an exploding fragmentation device for anti-personnel or other 6 payload type such as a signal sensing or relay device typically 7 having several antennas in a symmetrical array. In a 8 fragmentation bomblet for anti-personnel use, the widest 9 dispersing of fragments for maximum effectiveness occurs when lo bomblet 12 is substantially vertical at the moment it Il detonates, so that the blast effects are horizontal. If the 12 bomblet detonates while tipped at an angle, much of the blast i3 effect and fragmentation will disperse upwardly at an angle 14 toward the sky, hence will inflict no damage or injury to lS personnel on the ground. Thus, when the vertical axis through l6 bomblet 12 is at a 15 degree angle from a vertical reference, l7 the lethality of its burst will be only 60 percent of the 18 maximum achievable with the axis vertical. Similarly, for Is proper placement of antennas on the body 12, it must land with its center axis vertical. While no antennas are shown in the 2l drawings, it will be understood that any suitable antenna 22 system among the many known to the prior art may be adapted for 23 use in body 12. Similarly, no shaped charges are shown, and 24 the invention in this case does not depend upon selection of 25 any particular such penetration system known to the prior art.
26 However, with any such system, it is critically important that 27 body 12 containing a shaped charge must have its center axis 28 very nearly vertical when actuated to penetrate a substantially 29 horizontal armor plate surface, since the amorphous metal train formed by the shaped charge will otherwise not effectively 3l penetrate and defeat such plate. It is also iMportant, 32 especially in the case of fragmentation mechanisms, that body 12 not be spinning at the time of impact. The de-spin function , of chamber 14 is highly effective because lobes 3~ have 3 aerodynamic properties analogous to fins, whereby free airflow 4 between the spaced-apart lobes retards their rotation about s center axis 76 in FIG. 6.

7 While only one illustrative example of the device according 8 to the present has been described herein, many variations 9 thereof are possible within the scope of the teachings of this lO disclosure. Accordingly, the scope of the invention is not 11 limited by the example described but rather by the language of 12 the appended claims.

I claim:

, .j ' '` I,

Claims (12)

1. An inflatable decelerator for deployment with an attached load unit in an airstream comprising:
an inflatable flexibly collapsible chamber of generally star shape form consisting of a plurality of radially outwardly projecting lobes in spaced-apart relationship to each other, said chamber in its inflated state having an essentially flat upper surface and a conical lower surface, air inlet means including at least one air passage proximate the outer distal end of each said lobe, and air scoop means operatively related to each said air inlet and including an upstanding hood covering said inlet and spaced-apart therefrom for capturing a portion of external airflow around said chamber and directing said portion into said inlet to inflate said chamber.

2. The structure set forth in claim 1, further including:
a payload body of elongate form, attachment means on one end of said body for securing said chamber to said body, said body having a lower end opposite from said one end, said lower end having a castellated shape with cut-out portions between spaced-apart projections, one of said projections being in vertical alignment under each of said lobes.

3. The structure set forth in claim 2 above, wherein:
said lobes are three in number, and said projections are three, one under each of the lobes, and the outermost end of each said lobe projects outward beyond the turbulent flow resulting rom contact of the free airstream with said lower end.

4. The structure set forth in claim 2 above, wherein:
said payload body comprises a generally cylindrical shaped bomblet for fragmentation against ground targets.

5. The structure set forth in claim 2 above, wherein:
said payload body comprises a signal sensing antenna array.

6. The structure set forth in claim 2 above, wherein:
said payload body comprises a shaped charge for penetrating armor.

7. A combination deceleration and de-spin device for attachment to a sub-munition, comprising:
an inflatable starshaped chamber having at least three radially extending lobes and having in its inflated state an essentially flat upper surface and a conical lower surface, air inlet means on each of said lobes proximate the outermost ends thereof, and air scoop means operatively related to each said air inlet means and including an upstanding hood around said inlet means and spaced-apart therefrom for capturing a portion of external airflow around said chamber and directing said portion into said inlet to inflate said chamber.

8. The invention in accordance with claim 7, wherein the inflatable starlike chamber is so constructed and arranged that prior to deployment into an airstream, the lobes are tightly folded and collapsed upon themselves to form a high density compressed compact mass within the smallest possible space envelope.

9. The invention in accordance with claim 8, wherein the highly compressed and compact mass is so constructed and arranged to fit tightly and in close intimate nested relationship with a concentrically formed cavity at the center of each sub-munition.

10. The invention in accordance with claim 9, wherein ejection of the deceleration and de-spin device into an airstream causes the compressed and compact mass to be distended and the chamber inflated so as to decelerate and stabilize the sub-munition.

11. The invention in accordance with claim 10, wherein the chamber is collapsed and folded in a manner so that one or more of the hoods are exposed on an exterior surface of the folded mass so that upon deployment into an airstream, the pockets will initially engage and capture a portion of the air surrounding the mass and direct this portion of air into the chamber which will begin to unfold and extend all of the lobes radially outwardly to inflate the chamber.

12. The invention in accordance with claim 7, wherein the lobes are so constructed and arranged about a center vertical axis whereby balanced aerodynamic forces about the axis results when air impacts against the lobes causing self-correction of the position and direction of movement of the sub-munition to lessen and minimize wobbling, tumbling or nonuniformity in its flight path.