Antenna enclosure

Abstract

A retrofittable enclosure for storing a deployable antenna 120 on the outer surface of an underwater vessel 160 (e.g submarine, AUV), the retrofittable enclosure comprising: a protective housing 110 f

Description

Underwater vessels often have an antenna, for purposes such as communication above the water surface. When not in use the antenna is stowed within the vessel for example by a telescopic retraction to reduce the risk of damage from debris and other transportation problems. This requires a significant amount of design of an underwater vessel to accommodate the antenna. SUMMARY According to first aspect of the present invention, there is provided a retrofittable enclosure for storing a deployable antenna on the outer surface of an underwater vessel, the retrofittable enclosure comprising: a protective housing formed from a positively buoyant structure; an attachment means configured to attach the protective housing to the underwater vessel,; wherein in a first arrangement the deployable antenna is stowed substantially parallel to the outer surface of the underwater vessel and below the surface of the protective housing, and wherein in a second arrangement the antenna is deployed above the surface of the protective housing, wherein the protective housing comprises a hollow, wherein the hollow is configured such that the deployable antenna can be securely stowed, in the first arrangement. The retrofittable enclosure may preferably be attached to an underwater vessel after the underwater vessel frame has been manufactured, such that the attachment doesn’t materially alter the structural integrity of the underwater vessel or overall frame. For example the retrofittable enclosure may be surface mounted to the underwater vessel and as such can be added after the underwater vessel manufacture is finished. In another embodiment the retrofittable enclosure may be mounted to the frame and as such is added during manufacture but does not require redesigning of the underwater vessel as there are no changes made to the overall stress supporting structure. For example if the antenna were designed to sit below the surface skin of the underwater vessel, this is not retrofittable as it requires redesign or cutting of the frame to accommodate. Autonomous underwater vehicles are often very compact, and are filled with preexisting components to minimise space, stowage of a retractable antenna within the underwater vessel, is not always possible, alternatively the antenna may not always be required, and so the deployable antenna may be removed if surface mounted. The deployable antenna may comprise an elongate mast attached to the underwater vessel, and at the distal end from the connection point end, there may be data transfer devices, such as a video and a telecommunications. The protective housing protects the antenna during transit, in the stowed position, by reducing the possibility of damage from debris and collisions to the antenna by providing a barrier. Additionally the protective housing significantly reduces the stress forces encountered due to drag in the water by displacing the fluid around the antenna. The protective housing may be greater than, less than or equal to the length of the antenna. The protective housing may be greater than or equal to the entire length of the antenna and the pivot, such that when the antenna is in the first arrangement it is stowed entirely within the protective housing. The protective housing may have a length that is less than the length of the antenna and be designed to protect the most valuable and / or fragile parts of the antenna, such as the sensors and optics at the fore end of the antenna during stowage. The hollow of the protective housing allows the antenna to be stored in the protective housing, partially or fully encapsulating the antenna. The hollow shape and size may be the exact shape and size of the antenna, or it may be a larger simpler shape that the antenna can fit into, for example a rectangle formed from the furthest extremities of the antenna. The depth of the protective housing hollow, may be equal to or larger than the distance from underwater vessel skin to the furthest perpendicular distance to which the antenna extends. The protective housing may fill in the area between the antenna and underwater vessel skin to reduce relative movement and reduce the stress and torque incurred at a connection point end. The positively buoyant material or structure is one that is less dense than water, and so the positively buoyant material or structure floats in water, this may be fresh or salt water. The positively buoyant structure / material provides a positive buoyant force that partially or wholly counteracts the negative buoyancy caused by the additional mass of the antenna. This may reduce the overall impact of the antenna on the hydrodynamics of the underwater vessel and additionally counteracts the added mass of the retrofittable enclosure. The positively buoyant material may be any low density material, such as a polymer, a low density polymer, such as for example closed cell foam or an open cell foam with a waterproof exterior / skin. The positively buoyant material may help to counteract the buoyancy decrease caused by the antenna’s mass. The closed cell foam is water resistant and highly buoyant, hence reducing the effect of the antenna mass on the buoyancy of an underwater vessel. In a preferred arrangement the closed cell foam may be a syntactic foam. Syntactic foam has a high compressive strength which is important to ensure the protective housing doesn’t deform under hydrostatic pressure. The positively buoyant structure may be formed from a positively buoyant material with a density less than water, such as foam, wood and polymers. The positively buoyant structure may be a body that is in totality buoyant, such as a body formed with an air or other positively buoyant filled void. The positively buoyant structure may be manufactured as a body made from metal or other suitably rigid material with a void filled with air to form an overall positively buoyant structure. The positively buoyant structure may be formed from multiple bodies that in totality form the positively buoyant structure and as such form the protective housing for the antenna. The hollow may be formed from one piece of material that has had the shape of the antenna removed to create the hollow such that the antenna sits flat within the protective housing, alternatively the protective housing may be formed from multiple bodies that form a hollow to accommodate the antenna. The selection of a similar size and shape of the hollow to accommodate the antenna aids in protecting the antenna from debris or anything else that could damage the antenna if it were able to make contact. The protective housing may be shaped to minimise the drag caused by the enclosure in the water. The front (in relation to the front of the underwater vessel) end of the protective housing may be sloped to reduce drag. The protective housing moves through the water and therefore prevents the drag that would have been caused from the antenna. This aids in reducing the negative performance of a surface mounted antenna. The aft end of the protective housing may be sloped to encourage non-turbulent water flow, and hence reduce the drag effects caused to the underwater vessel by adding the retrofittable enclosure. The deployable antenna may be stowed in a more hydrodynamic position in the first arrangement, during non-use and raised to the second arrangement, i.e. the operating position in-use. If the deployable antenna were permanently erect this may increase drag and stress on the antenna. The antenna may be deployable from underwater such that in the second arrangement the antenna is caused to be above the water surface to communicate above the surface. The antenna may comprise any data transfer means, such as, for example telecommunication, visual imagery or a sensor required by the underwater vessel. The antenna may comprise a connection point to the underwater vessel to deploy said antenna between the first and second arrangement, such as an actuator, motor, which can raise or lower a central supporting shaft. The connection point may be at the distal end the data transfer means. The substantially parallel antenna may be any angle where the antenna is below the surface of the protective housing, depending on the height of the protective housing this may be anywhere from 0 ° to 30° relative to the surface of the underwater vessel. The substantially parallel stowage reduces the drag caused by the antenna during underwater vessel motion, such that it reduces the overall profile for collision with debris and reduces the stress incurred along the length of the antenna and at the antenna connection point. The protective housing may also protect any lenses, apertures or sensor electronics on the data transfer tip of the antenna. The protective housing may comprise a flexible lip or cover, such as to reduce ingress of debris into the protective housing when the antenna is deployed in the second arrangement, and further to provide increased protection to the exposed part of the antenna, when stowed in the first arrangement. The protective housing may comprise a thin membrane through which the deployable antenna is stowed underneath. The thin membrane presents the further ingress of debris. The thin membrane may comprise a valve or slit to allow the ease of antenna stowage. The protective housing may comprise sides that are configured to close over the antenna in the first arrangement. The protective housing may be actuated to fully cover the antenna when it is stowed to prevent the ingress of debris and reduce hydrostatic forces on the antenna in transit. The protective housing may comprise a lockable lid, such that in the first arrangement the protective housing forms a waterproof barrier completely surrounding the deployable antenna. The secure stowage of the antenna prevents too much relative movement between antenna and underwater vessel reducing the stress at the connection point where the antenna is mounted to the underwater vessel. According to a further aspect of the invention there is provided an underwater vessel comprising a deployable antenna located on an outer surface of the underwater vessel, and a retrofittable enclosure, as defined herein before, for storing the antenna such that the antenna can be securely stowed in the retrofittable enclosure. In the second arrangement the antenna may be substantially or wholly above the water in the deployed position to reduce signal attenuation of the data transfer signal. The deployable antenna may have a connection point at one end of the antenna to fasten it to the underwater vessel. The antenna may be moved between the first and second arrangement by any means, whilst telescopic may be a possibility, it would require stowage inside the underwater vessel, and this may cause issues with integrity, or interference with payloads on the underwater vessel. Preferably the antenna may be surface mounted, and may be rotated about a pivot point, to move between the first and second arrangement. The rotation may range from 0° to 180° relative to the surface skin of the underwater vessel, and the deployable antenna may rotate through use of an actuator, bell crank, or a motor. Rotation around a pivot point is comparatively simpler to implement, manufacture and waterproof, in comparison for example to a telescopic deployment which can be complex and difficult to waterproof due to all the mating surfaces. In the second arrangement the antenna may be substantially perpendicular to the surface of the underwater vessel. Substantially perpendicular may range from 60° to 120° relative to the surface skin of the underwater vessel. The antenna being substantially perpendicular to the underwater vessel in the second arrangement allows the greatest distance between distal end of antenna and the underwater vessel surface such that the underwater vessel can remain further below the water surface while the antenna is above. This second arrangement position will also maximise the range / transmission of the telecommunication means of the underwater vessel. The attachment means to fasten the retrofittable enclosure to the underwater vessel may comprise a permanent attachment, or removable attachment. The permanent attachment means may comprise: adhesive, rivets, welding, other permanent bonding or any such combination attached directly to the underwater vessel outer skin or to the structural frame of the underwater vessel without structurally compromising the underwater vessel. The permanent attachment method allows the retrofittable enclosure to be fitted securely to the ship and prevent any accidental detachment. The removable attachment means may comprise: magnets, a catch system, threaded connectors, such as bolts or any such combination that can be attached and removed by a user and may be attached directly to the underwater vessel outer skin or to the structural frame of the underwater vessel without structurally compromising the underwater vessel.. The removable attachment method allows the retrofittable enclosure to be attached and detached from the underwater vessel as needed, preventing the requirement for a redesign of the underwater vessel’s structural frame or if the antenna is no longer required. The attachment means may comprise an adhesive. The adhesive may be a metal adhesive such as epoxy. The use of an adhesive may allow a simpler manufacturing step over other methods such as welding, and the additive nature of bonding prevents damage to the underwater vessel structure. BRIEF DESCRIPTION OF THE FIGURES Embodiments of the invention will now be described by way of example only with reference to the figures, in which: Figure 1a shows an example lengthways cross section of a retrofittable enclosure with the antenna deployed. Figure 1b shows an example lengthways cross section of a retrofittable enclosure with the antenna stowed. Figure 1c shows an example plan view of a retrofittable enclosure with the antenna stowed. Figure 1d shows an example widthways cross-section of a retrofittable enclosure with the antenna stowed. DETAILED DESCRIPTION With reference to Figure 1a, a retrofittable enclosure 100 a protective housing 110, a deployable antenna 120 attached (method not shown) to an underwater vessel 160. The deployable antenna 120 is rotated around a pivot 150 that is attached to the underwater vessel 160. The antenna 120 is formed from an elongate mast 190 attached to the pivot 150, and at the distal end there are data transfer devices 195, such as a video 130 that extend laterally form the antenna, and a telecommunications means 140 that extend from the distal face of the antenna mast 190. The deployable antenna is in the deployed second arrangement where some or all of the antenna 120, would be above the water surface 185. The underwater vessel 160 is a submarine with a front “nose” end 165 and an aft propulsion end, with a propulsion means 155. The retrofittable enclosure 100 is attached to the underwater vessel 160, such as by welding, (not shown). The total length of the protective housing 110 is greater than the antenna and encompasses the pivot 150. The protective housing 110 is wider and has a greater depth than the corresponding greatest extensions of the antenna 120. The protective housing 110 comprises a hollow (not shown) of a similar size and shape as the antenna. The protective housing 110 comprises hydrodynamic sloping front 170 and aft 180 sections, wherein the sloping front 170 aids in reducing the drag of the retrofittable enclosure 100 and prevents debris from damaging the antenna Figure 1b is the same retrofittable enclosure 100 as shown in figure 1a except the deployable antenna is in a stowed first arrangement and is completely stowed within the protective housing 110, below the water surface 185. Figure 1 c is a plan view of the same retrofittable enclosure as shown in figure 1 b. The deployable antenna 120 sits within the hollow 270 created by the arrangement of the protective housing 110, wherein the hollow 270 is longer than the total length of the antenna and is wider than the both the laterally extending visual imagery means 130 and the pivot 150. The deployable antenna 120 sits on top of the body 290 that lies between the stowed deployable antenna 120 and the underwater vessel (not shown). With reference to Figure 1d a retrofittable enclosure 100 comprises a deployable antenna 120 attached (as per figure 1a) to an underwater vessel 160. The deployable antenna has visual imagery means 130 that extend laterally from the antenna, and a telecommunications means 140 that extend from the distal face of the antenna. The retrofittable enclosure 100 comprises a protective housing 110 formed from the combination of three distinct bodies 310 all attached to the curved surface of the underwater vessel. Each of these three bodies comprise an outer waterproof layer 320 and an inner air filled hollow 330. The three bodies 310 are formed from two trapezium shapes 340, 360 on either side of the deployable antenna 120 and extending above the antenna, and a singular parallelogram shape 290 that sits between the antenna and the surface 160 of the underwater vessel. The retrofittable enclosure 100 is attached to the underwater vessel by an attachment means (not shown).The hollow 270 is the gap created by arrangements of the three distinct bodies 310 to form the enclosure around the antenna 120 .

Claims

1. A retrofittable enclosure for storing a deployable antenna on the outer surface of an underwater vessel, the retrofittable enclosure comprising:a protective housing formed from a positively buoyant structure;an attachment means configured to attach the protective housing to the underwater vessel, whereinin a first arrangement the deployable antenna is stowed substantially parallel to the outer surface of the underwater vessel and below the surface of the protective housing, and whereinin a second arrangement the antenna is deployed above the surface of the protective housing, whereinthe protective housing comprises a hollow, whereinthe hollow is configured such that the deployable antenna can be securely stowed, in the first arrangement.

2. The retrofittable enclosure according to claim 1, wherein the attachment means comprises a permanent attachment, or a removable attachment.

3. The retrofittable enclosure according to claim 2, wherein the attachment means comprises bolting.

4. The retrofittable enclosure according to any preceding claim, wherein the positively buoyant structure is formed from a positively buoyant material.

5. The retrofittable enclosure according to claim 4, wherein positively buoyant material is a closed cell foam.

6. The retrofittable enclosure according to claim 5, wherein the closed cell foam is a syntactic foam.

7. The retrofittable enclosure according to any preceding claim, wherein the protective housing is shaped to minimise the drag caused by the housing in the water.

8. The retrofittable enclosure according to any preceding claim, wherein in the second arrangement the antenna is substantially perpendicular to the surface of the underwater vessel.

59. An underwater vessel comprising:a deployable antenna located on an outer surface of the underwater vessel, anda retrofittable enclosure according to any preceding claim, for 10 storing the antenna such that the antenna can be securely stowed in the retrofittable enclosure.

10. The underwater vessel according to claim 9, wherein the deployable mast is rotated about a pivot point, to move between the first and second 15 arrangement.

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