BACKGROUND An aircraft carried rocket launcher of the type in question includes an array of launch tubes, open at the leading end for the launching of rockets carried in the tubes. It is known to provide a cover on the front of such a launcher for environmental protection. For use on high speed aircraft the protective covers have been in the form of fairings for aerodynamic purposes. With lower speed aircraft, especially helicopters, the aerodynamic considerations are not as significant and flat forward covers have been used for environmental protection alone.

With a flat cover the rocket exhaust plume will"splash"against the forward end of the launcher and may be ingested into the aircraft engine. The ingestion of high temperature rocket exhaust can in turn lead to engine surge during rocket firings. Other difficulties that arise with at least some of the known protection devices include the disintegration of the protection device into fragments that impact on the aircraft and may cause damage, referred to as Foreign Object Damage (FOD).

The present invention is therefore concerned with the provision of a rocket protection device that will minimize the rocket exhaust ingestion into the aircraft engine and that will preferably provide environmental protection to the rockets while minimizing the potential for FOD.

SUMMARY According to the present invention there is provided a rocket protection device for use with a rocket launcher having a plurality of launcher tubes therein, the rocket protection device comprising: a body with a convex leading surface and a plurality of rocket bores through the body; and a body mount for mounting the body on a front end of the launcher with the rocket bores through the body aligned with the respective launcher tubes.

The convex configuration of the leading surface of the protection device minimizes the rocket exhaust ingested by the engine of the aircraft. It is recognized that in the prior art the rocket exhaust"splash"on the forward launcher face, as the rocket separates from the launcher, is a major contributor to the exhaust ingestion problem. The contoured profile of the present rocket protection device provides a more streamlined exhaust plume flow around the launcher. As a result, the plume does not expand towards the aircraft engine air intake.

Theoretical studies show that the intake does not experience any change in its operating conditions as a result of rocket firing. The opposite occurs when the protection device is not employed. In this case, the"splash"allows the rocket exhaust to expand in all directions. Analytical results show that the engine compressor experiences an increase in temperature by as much as 400°K.

The protection device preferably includes a cover mechanism for closing the open leading ends of the rocket bores. This may be a membrane extending over the convex leading surface of the body and secured to the body for closing the leading ends of the rocket bores. In alternative embodiments, plugs may be inserted into the leading ends of the rocket bores. This provides additional environmental protection to the rockets loaded in the launcher both in flight and on the ground. Environmental protection is also provided by the core of the body.

Foreign Object Damage (FOD) becomes of importance when fragments of launcher components (e. g. cover mechanisms) produced by the passing of the rockets through them, are large enough to cause damage to the aircraft. The FOD produced by the present protection device may be limited with appropriate selection of membrane or plug materials and attachment techniques.

In the preferred embodiments of the present invention, the protection device is quickly and easily installed on the launcher in the field by a single person without the use of tools.

The protection device is intended to be reusable, the only disposable part being the cover mechanism, where used.

Embodiments of the invention will now be described by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, which illustrate an exemplary embodiment of the present invention: Figure 1 is an isometric view of a launcher equipped with the rocket protection device; Figure 2 is a longitudinal cross-section of the rocket protection device mounted on the launcher; Figure 3 is a partial plan view showing the mount safety pin and the band clamp for the membrane; Figure 4 is a rear isometric of the protection device core; Figure 5 is an isometric view of the locking ring; Figure 6 is a section along line 6-6 of Figure 5; Figure 7 is an isometric view of the retaining ring mounted on the launcher; and Figure 8 is a perspective of an alternative embodiment of the rocket protection device.

DETAILED DESCRIPTION Referring to the accompanying drawings, and especially to Figure 1, there is illustrated a rocket launcher assembly 10 that includes a launcher 12 with a leading end 14 carrying a rocket protection device 16. The protection device includes a mount 17 that mounts the protection device on the launcher. This mount includes a retaining ring 18 that is fixed to the launcher and a locking ring 20 that is fixed to the rocket protection device body 22 and engages with the retaining ring 18.

The body 22 has a convex leading face 24. As shown in Figure 2, the body 22 has a core 26 moulded from glass reinforced nylon with a membrane 28 over the convex leading surface of the core to provide the outer skin of the body. The membrane is formed from a flaccid synthetic plastic material and is held in place on the core using a band clamp 30.

Referring most particularly to Figure 4, the core 26 of the protection device has an outer shell 32 with an ellipsoidal leading face 34. Moulded integrally with the shell are nineteen rocket bores 36. As illustrated in Figure 2, when the protection device is mounted on the launcher, the bores 36 align with respective ones of the launcher tubes 38 in the launcher, with the trailing end of the core confronting the launcher front bulkhead 40.

At the trailing end of the core 26, the shell has a reduced outer diameter skirt 42 which ends at a rearwardly facing shoulder 43.

For locking purposes, the core has eight external tabs 44 spaced around the external surface of the core immediately in front of the shoulder 43.

These mate with the locking ring as will be described in the following.

Positioned forward of the tabs 44 are six circular recesses 46 in the outer surface of the core. Each of these recesses accommodates a membrane mounting stud 48 that projects from the recess beyond the surface of the core.

The configuration of the locking ring 20 is illustrated most particularly in Figure 5 and 6. The locking ring has a front portion 50 with eight internal tabs 52 that mate with the external tabs 44 at the trailing end of the core.

A back portion 54 of the locking ring has a smaller internal diameter than the front portion 50. The two portions are joined by an internal, forwardly facing shoulder 56. The back portion 54 carries eight internat tabs 58 which serve to connect the locking ring to the retaining ring as will be described more fully in the following. Pin holes 60 in the front portion 50 of the locking ring accommodate pins (not shown) to fix the circumferential alignment of the locking ring on the core body.

The locking ring is equipped with four external ribs 62. They serve as grip for rotating the ring during installation.

At the top of the locking ring 20 is a lug 64 which is pinned to the retaining ring on installation.

The configuration of the retaining ring is most clearly illustrated in Figure 7. The retaining ring includes a leading sleeve 66. This is equipped with eight external L-shaped slots 68. Each slot has an axial part 70 that opens to the leading edge 72 on the sleeve and a circumferential part 74 that extends circumferentially at the back end of the axial portion 68. The locking ring mounts on this retaining ring with the sleeve 18 fitted inside the trailing portion 54 of the locking ring. The tabs 58 on the locking ring fit into the respective slots 68 and the lock ring is rotated clockwise to lock the locking ring and the core on which it is mounted to the retaining ring. At the back end of the sleeve 16, the retaining ring has six lugs 76 that project internally over the front buikhead 40 of the launcher.

The mounting lugs 76 are secured to the launcher bulkhead by bolts 78. A lug 80 on the top of the retaining ring aligns with the lug 64 on the locking ring when the two are connected to accommodate a safety pin 82 (Figure 3) to prevent lock ring rotation on the retaining ring. A tether 84 ties the safety pin to the locking ring lug 64. An integral collar 85 at the rear end of the retaining ring fits over the leading end of the launcher.

As illustrated in Figures 1 and 2, the membrane 28 is preformed to fit the surface contour of the core. Immediately in front of the membrane's rear edge 86 and spaced around the membrane are grommets that fit over respective ones of the membrane mounting studs 48 to hold the membrane in place. The band clamp 30 is then installed. This includes a band 90 with elongate slots 92 that are positioned over the studs 48 and the grommets 88. A clamp 94 includes an over centre toggle 96 for holding the ends of the band 90 together under tension. Two lugs 98 on opposite sides of the toggle accommodate a safety pin 100 that is connected to the band 90 by a tether 102.

To install the protection device on a launcher, the retaining ring is oriented and fastened to the launcher with the bolt 78. With the lock ring and the membrane already installe on the core, the core/lock ring combination is oriented and positioned forward of the retaining ring. The lock ring is placed over the retaining ring and rotated clockwise to lock the core to the retaining ring. The safety pin 82 is installed through the lugs 64 and 80 to prevent lock ring rotation.

This design offers quick and easy installation of the rocket protection device on the launcher in the field. It is readily installed by a single person with no tools.

The installation of the membrane is also easily performed with no tools and in the field. The core and lock ring are reusable items. The retaining ring, which is bolted to the launcher may also be reused on several launchers as launchers become unserviceable.

The core and lock ring are both moulded synthetic plastic and require minimum service and maintenance.

In an alternative embodiment of the invention, the membrane may be fixed to the core by a layer of adhesive, reducing the possibility of FOD from torn off parts of the membrane. In this case, it may not be possible to re-skin the core in the field, depending on the adhesive employed. The band clamp is no longer required.

In a further embodiment of the rocket protection device, illustrated in Figure 8, the leading ends of the rocket bores are closed with plugs 110 of synthetic foam material. This embodiment also includes a frustoconical ring 122 immediately in front of the lock ring 20. This is located approximately where the band clamp is located in the previously described embodiment. The ring 112 serves as a blast deflector for deflecting the rocket exhaust plume away from the lock ring.

While particular embodiments of the invention have been described in the foregoing, it is to be understood that other embodiments are contemplated and are intended to be included within the scope of the invention.