Valve for use in an anchoring and / or payload delivery system for an underwater ve hicle

Abstract

A valve for controlling flow of ambient water into a buoyant body in an anchoring and / or payload delivery system for an underwater vehicle, the valve comprising:at least one valve inlet configured to be open, in use, to ambient water;at least one valve outlet configured to communicate with the buoyant body;a pressure balance chamber in fluid communication with one or more of the valve inlets and thereby configured to be open, in use, to ambient water;a stationary part;a moveable part arranged to be exposed at least partially to ambient water and configured to move, in use, relative to the stationary part between a first position, wherein the valve is in a closed state in which fluid communication from the valve inlet(s) to the valve outlet(s) is prevented and a second position, wherein the valve is in an open state in which fluid communication from the valve inlet(s) to the valve outlet(s) is allowed, thereby allowing ambient water to flow into the buoyant body;wherein a first part of the moveable part is exposed to ambient water and a second part of the moveable part is exposed to water within the pressure balance chamber so that the moveable part is pressure balanced such that when the valve is in the closed state there is substantially no net force on the moveable part due to the pressure of the ambient water; andwherein the valve is configured such that a movement-resisting force between the stationary part and the moveable part holds the moveable part in the first position, in use, until a valve actuation mechanism is operated to overcome the movement-resisting force and move the moveable part to the second position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONSThis application in a by-pass continuation of PCT Application No. PCT / GB2024 / 051503, filed Jun. 13, 2024, which claims the benefit of and priority to United Kingdom Patent Application No. 2312452.2, filed Aug. 15, 2023. The contents of these applications are incorporated herein by reference in their entireties and for all purposes.The present disclosure relates to a valve for use in an anchoring and / or payload delivery system for an underwater vehicle, in particular, but not exclusively, an autonomous underwater vehicle (AUV). The disclosure relates to an anchoring and / or payload delivery system for an underwater vehicle comprising such a valve. The disclosure also relates to an underwater vehicle comprising such an anchoring and / or payload delivery system.An autonomous underwater vehicle (AUV) is a robot submarine, which can be used to explore the world's oceans without a pilot or any tether.It is known to deploy an AUV to carry out submarine operations, including, for instance, surveys of areas of ocean, to improve our understanding of ocean ecosystems. Ideally, such surveys of an area of ocean require many samples, measurements and / or observations to be taken at depth over an extended period of time. AUVs are typically powered by one or more batteries. The typical battery lifetime of an AUV may make it difficult, challenging or impossible to carry out a longer-term survey of an area of ocean. For instance, it may be desirable to survey over an extended period of time a remote and / or periodically inaccessible area of ocean such as beneath an ice sheet in a polar region, in order to improve our understanding of the ocean ecosystem in the area of ocean. However, the typical battery lifetime of an AUV may be insufficient for an AUV to be deployed to carry out the desired survey.An AUV may be deployed for a longer-term survey of an area of ocean if it can be reliably anchored to the seabed at a location of interest between taking samples, measurements and / or observations. While the AUV is anchored to the seabed, the AUV's systems can be turned off or run in a low power or standby mode. Power need only be drawn from the AUV's batteries when the AUV is moving from one location to another and / or taking samples, measurements and / or observations. Consequently, the AUV potentially may be deployed for a longer period of time than if it is having to run on full battery power throughout a given deployment.US2020 / 0103317A1 discloses an example of an AUV with an umbilical reel and anchor device. An umbilical cable of the umbilical reel is connected to the anchor device. In operation, the umbilical reel raises and lowers the anchor device through payload doors of the AUV. The anchor device is a suction anchor.Briggs, Robert Clayton. “Mechanical design of a self-mooring autonomous underwater vehicle.” PhD diss., Virginia Tech, 2010, Briggs, R., McCarter, B., Neu, W. L., & Stilwell, D. J. (2010, September). Design elements of a prototype self-mooring AUV. In OCEANS 2010 MTS / IEEE SEATTLE (pp. 1-8). IEEE 2010 and McCarter, Brian, Robert Briggs, Stephen Portner, Dan Stilwell, Wayne Neu, Ryan Coe, Richard Duelley, Dexter Malley, and Jason Mims. “Design and testing of a self-mooring AUV.” In 2012 Oceans, pp. 1-8. IEEE, 2012 describe a single activation mooring system built into an AUV.

[0008] A first aspect provides a valve for controlling flow of ambient water into a buoyant body in an anchoring and / or payload delivery system for an underwater vehicle, the valve comprising:

[0009] at least one valve inlet configured to be open, in use, to ambient water;

[0010] at least one valve outlet configured to communicate with the buoyant body;

[0011] a pressure balance chamber in fluid communication with one or more of the valve inlets and thereby configured to be open, in use, to ambient water;

[0012] a stationary part;

[0013] a moveable part arranged to be exposed at least partially to ambient water and configured to move, in use, relative to the stationary part between a first position, wherein the valve is in a closed state in which fluid communication from the valve inlet(s) to the valve outlet(s) is prevented and a second position, wherein the valve is in an open state in which fluid communication from the valve inlet(s) to the valve outlet(s) is allowed, thereby allowing ambient water to flow into the buoyant body;

[0014] wherein a first part of the moveable part is exposed to ambient water and a second part of the moveable part is exposed to water within the pressure balance chamber so that the moveable part is pressure balanced such that when the valve is in the closed state there is substantially no net force on the moveable part due to the pressure of the ambient water; and

[0015] wherein the valve is configured such that a movement-resisting force between the stationary part and the moveable part holds the moveable part in the first position, in use, until a valve actuation mechanism is operated to overcome the movement-resisting force and move the moveable part to the second position.

[0016] As a result of the moveable part being pressure balanced such that when the valve is in the closed state there is substantially no net force on the moveable part due to the pressure of the ambient water, variations in the movement-resisting force due to depth may be relatively small. Hence, a relatively simple and / or low force and / or reliable valve actuation mechanism may be employed. Consequently, the valve may be relatively cheap to manufacture and / or operation of the valve may be relatively reliable, even on longer-term missions.

[0017] The moveable part may be received at least in part in the stationary body or vice versa.

[0018] The moveable part may be movable linearly relative to the stationary body.

[0019] The moveable part may be moveable in a longitudinal direction relative to the stationary body.

[0020] The moveable part may include a valve stem.

[0021] The stationary part may include a valve body.

[0022] The valve stem may be received at least in part in the valve body. The valve stem may be moveable longitudinally relative to the valve body.

[0023] A passage disposed at least in part within the moveable part may connect the valve inlet to the pressure balance chamber. The passage connecting the valve inlet to the pressure balance chamber may extend from a first end of the moveable part to a second end of the moveable part. The passage connecting the valve inlet to the pressure balance chamber may extend in a longitudinal direction from the or a first end of the moveable part to the or a second end of the moveable part. The passage connecting the valve inlet to the pressure balance chamber may be straight. The passage connecting the valve inlet to the pressure balance chamber may have a constant cross-section along its length.

[0024] The movement-resisting force may comprise, or consist essentially of, a friction force. Additionally or alternatively, the movement-resisting force may comprise any suitable force, e.g. a magnetic force.

[0025] The valve outlet(s) may comprise one or more flood ports.

[0026] The valve may comprise one or more sealing means configured to provide a fluid-tight seal between the stationary part and the moveable part.

[0027] The stationary part may be adapted to be connected, in use, to a release plate. The release plate may be configured to be fitted to a part of a structure of the underwater vehicle.

[0028] The stationary part may comprise an elongate body. At an end, the stationary part may comprise a flange.

[0029] A second aspect provides an anchoring and / or payload delivery system for an underwater vehicle comprising:

[0030] at least one valve according to the first aspect;

[0031] a buoyant body downstream of the or each valve, the or each buoyant body containing air at a reduced pressure;

[0032] a surface seal between an end of one or more of the buoyant bodies and a release plate, each surface seal being configured to hold one of the buoyant bodies in place against the release plate and / or a surface seal between a first part of one or more of buoyant bodies and a second part of the one or more buoyant bodies, the surface seal being configured to hold the second part of the buoyant body in place against the first part of the buoyant body; and

[0033] a valve actuation mechanism operably connected to one or more of the valves, the valve actuation mechanism being operable to overcome the movement-resisting force and move the moveable part of a given valve to the second position, thereby allowing water to flow into the buoyant body downstream of the given valve such that the buoyancy of the buoyant body downstream of the given valve changes sufficiently for the surface seal to be overcome, thereby releasing the buoyant body from the release plate or the second part of the buoyant body from the first part of the buoyant body.

[0034] The anchoring and / or payload delivery system may be configured such that one or more of the buoyant bodies is / are neutrally buoyant when the moveable part of the valve(s) upstream of the one or more buoyant bodies is / are in the first position.

[0035] The anchoring and / or payload delivery system may be configured such that one or more of the buoyant bodies become(s) negatively buoyant or positively buoyant once the moveable part of the valve(s) upstream of the one or more buoyant bodies is / are in the second position.

[0036] A tether may be housed at least partially within one or more of the buoyant bodies.

[0037] The tether may connect the buoyant body or the second part of the buoyant body to the or a release plate. The tether may releasably connect the buoyant body or the second part of the buoyant body to the or a release plate.

[0038] The anchoring and / or payload delivery system may comprise a tether release actuator operable to release the tether from the release plate.

[0039] The tether may have a length greater than a length of the buoyant body.

[0040] The tether may include a length of shock cord.

[0041] The tether may include a length of chain.

[0042] The second part of the buoyant body may be configured to act as a mass anchor.

[0043] The buoyant body may be configured to act as a mass anchor.

[0044] The buoyant body may contain a payload. The payload may include a payload housing and a payload device stored within the housing.

[0045] The payload or payload housing may be releasably connected to the buoyant body, the second part of the buoyant body and / or the or a release plate.

[0046] The second part of the buoyant body that is released from the first part of the buoyant body may comprise an end cap.

[0047] One or more of the surface seals may be provided at least in part by a sealing element, e.g. a sealing ring. The sealing element(s) may each be disposed between an end of the buoyant body and the release plate or between a second part of the buoyant body and a first part of the buoyant body.

[0048] The reduced pressure of air in the or each buoyant body may be a vacuum pressure. For instance, the reduced pressure of air in the buoyant body may be no more than 0.5 bar, no more than 0.3 bar, no more than 0.2 bar or no more than 0.1 bar.

[0049] One or more of the buoyant bodies may be tubular.

[0050] The valve actuation mechanism may comprise a holding means for holding directly or indirectly the moveable part in the first position and an actuator operably connected to the holding means, wherein the actuator is operable to cause the holding means to release the valve actuation member. Once released, the moveable part of the valve may be free to move from the first position to the second position.

[0051] The valve actuation mechanism may comprise a valve actuation member, e.g. a valve actuation arm, operably connected to the moveable part of the valve and the holding means may be configured to holding the valve actuation member such that the moveable part is in the first position. Once released, the valve actuation member may be configured to act on the moveable part of the valve to move the moveable part of the valve from the first position to the second position. Once released, the valve actuation member may be configured to pull or push the moveable part of the valve from the first position to the second position. The valve actuation member may comprise a valve actuation arm.

[0052] The valve actuation mechanism may comprise a biasing means configured to bias the moveable part of the valve from the first position towards the second position. For instance, the biasing means may be configured to bias the or a valve actuation member in a direction such that when the valve actuation member is released, the valve actuation member pulls or pushes the moveable part of the valve from the first position to the second position. The biasing means may include at least one resilient member such as spring or the like.

[0053] The valve actuation mechanism may include at least one stop means to limit directly or indirectly the extent of movement of the moveable part of the valve. For instance, one or more of the stop means may be configured to limit the extend of movement of the or a valve actuation member operably connected to the moveable part of the valve.

[0054] In an implementation, the valve actuation member may be disposed a distance away from one face, e.g. an upper face, of the or a release plate and the associated buoyant body may be disposed adjacent or connected to an opposite face, e.g. a lower face, of the or a release plate.

[0055] The valve actuation mechanism may comprise a swinging pivot link connecting a first end of the valve actuation member, e.g. the valve actuation arm, to a face of the release plate.

[0056] The holding means may act on a second end of the valve actuation member, e.g. the valve actuation arm.

[0057] The valve actuation member may be connected, e.g. pivotally connected, to the moveable part of the valve at an intermediate point along a length of the valve actuation member.

[0058] For example, the holding means may comprise a Galvanic link and the actuator operably connected to the holding means may comprise a Galvanic link actuator.

[0059] In an implementation, the valve actuation mechanism may comprise an electromagnet, a solenoid and / or a servo motor operably connected to the moveable part of the valve.

[0060] The anchoring and / or payload delivery system may comprise up to or at least two, up to or at least three, up to or at least six, up to or at least 10, up to or at least 12, up to or at least 20 or up to or at least 50 buoyant bodies.

[0061] A third aspect provides an underwater vehicle comprising a valve according to the first aspect or an anchoring and / or payload delivery system according to the second aspect.

[0062] The underwater vehicle may be an autonomous underwater vehicle (AUV). The underwater vehicle may be a remotely operated vehicle (ROV).

[0063] The underwater vehicle may be powered by one or more fuel cells and / or one or more batteries.

[0064] The underwater vehicle may have any depth rating. For instance, the underwater vehicle may have a depth rating of up to or at least 1000 m, up to or at least 2000 m, up to or at least 3000 m, up to or at least 4000 m, up to or at least 5000 m, up to or at least 6000 m or up to or at least 7000 m.

[0065] The anchoring and / or payload delivery system may be disposed at least partially in a forward portion of the underwater vehicle.

[0066] The underwater vehicle may be configured such that the buoyant body, e.g. flood tube, or part thereof released in an anchoring and / or payload delivery operation may exit, e.g. fall, unimpeded from the underwater vehicle.

[0067] In implementations, the anchoring and / or payload delivery system may be configured such that the buoyant body or part thereof released in an anchoring and / or payload delivery operation may exit the underwater vehicle in any direction, e.g. in an upwards direction or a downwards direction relative to the underwater vehicle. For instance, the anchoring and / or payload delivery system may be configured such that a payload may exit the underwater vehicle in an upwards direction or a downwards direction relative to the underwater vehicle.

[0068] In implementations, the underwater vehicle may comprise one or more doors or covers configured to open to allow one or more of the buoyant bodies to exit the underwater vehicle during an anchoring and / or payload delivery operation.

[0069] The door(s) or cover(s) may be disposed at least partially in or on an exterior surface of the underwater vehicle.

[0070] The door(s) or cover(s) may be configured to return to a closed position once the anchoring and / or payload delivery operation is completed. The door(s) or cover(s) may be biased towards the closed position.

[0071] A fourth aspect provides a method of delivering a payload from an underwater vehicle comprising:

[0072] operating an underwater vehicle according to the present disclosure, the underwater vehicle comprising a payload delivery system according to the present disclosure; and

[0073] while the underwater vehicle is submerged, deploying the payload delivery system to release the payload from the underwater vehicle.

[0074] The payload may be released from the underwater vehicle when the underwater vehicle is moving and / or when the underwater vehicle is at anchor and / or as part of an anchoring operation.

[0075] The method may be carried out as part of a mission, which may be at least partially pre-planned.

[0076] The mission may include delivering a plurality of payloads, e.g. at one or more desired or predetermined locations and / or times, during the mission.

[0077] Each payload may be negatively buoyant or positively buoyant.

[0078] Each payload may include a payload housing and a payload device contained in the payload housing.

[0079] A fifth aspect provides a method of carrying out a mission using an underwater vehicle comprising:

[0080] operating an underwater vehicle according to the present disclosure, the underwater vehicle comprising an anchoring system according to the present disclosure;

[0081] directing the underwater vehicle along a route submerged within a body of water, the route including at least one desired anchoring location;

[0082] deploying the anchoring system to anchor the underwater vehicle at each of the desired anchoring locations; and

[0083] after a period at anchor at a given desired anchoring location, releasing the anchor from the underwater vehicle and, optionally, directing the underwater vehicle along a subsequent section of the route.

[0084] The mission may be at least partially pre-planned.

[0085] The route may include a plurality of desired anchoring locations.

[0086] At one or more, e.g. all, of the anchoring locations, the underwater vehicle may be powered down or operated in a lower or low power mode for at least some of the period while the underwater vehicle is at anchor.

[0087] One or more payloads may be delivered during the mission, e.g. at one or more desired or predetermined locations and / or times, during the mission. A given payload may be released from the underwater vehicle when the underwater vehicle is moving and / or when the underwater vehicle is at anchor and / or as part of an anchoring operation.

[0088] Each payload may be negatively buoyant or positively buoyant.

[0089] Each payload may include a payload housing and a payload device contained in the payload housing.

[0090] The mission may have an overall duration of up to or at least a week, up to or at least four weeks, up to or at least 12 weeks, up to or at least 26 weeks or up to or at least a year.

[0091] The body of water may include a sea and / or an ocean. The body of water may include a freshwater body of water and / or a saltwater body of water.

[0092] One or more, e.g. all, of the desired anchoring locations may be on a surface or a structure within the body of water, e.g. a surface or a structure at the bottom of the body of water. The surface at the bottom of the body of water may be the seabed.

[0093] The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and / or combined with any other feature or parameter described herein.

[0094] Embodiments will be described, by way of example only, with reference to the accompanying drawings, in which:

[0095] FIG. 1 shows a cross-sectional view of an example of a flood tube assembly for an anchoring system for an underwater vehicle;

[0096] FIG. 2 shows an enlarged view of an upper portion of the flood tube assembly of FIG. 1;

[0097] FIG. 3 shows an enlarged view of the valve in the flood tube assembly of FIG. 1 with the valve in a closed state;

[0098] FIG. 4 shows the valve of FIG. 3 in an open state;

[0099] FIG. 5 shows a cross-sectional view of another example of a flood tube assembly for an anchoring system for an underwater vehicle;

[0100] FIG. 6 shows a cross-sectional view of an example of a flood tube assembly for a payload delivery system for an underwater vehicle;

[0101] FIG. 7 shows an autonomous underwater vehicle (AUV) releasing an anchor;

[0102] FIG. 8 shows the AUV of FIG. 7 with the anchor tethered to the AUV and descending towards the seabed;

[0103] FIG. 9 shows the AUV of FIG. 7 anchored to the seabed;

[0104] FIG. 10 shows the AUV of FIG. 7 moving away from the seabed after untethering the anchor;

[0105] FIG. 11 shows a portion of an AUV with a door in an external surface of the AUV in a closed position;

[0106] FIG. 12 shows the portion of the AUV of FIG. 11 with the door in an open position; and

[0107] FIG. 13 shows the portion of the AUV of FIG. 11 and FIG. 12 with the door in the closed position following an anchoring and / or payload delivery operation.

[0108] FIG. 1 shows a cross-sectional view of an example of a flood tube assembly 1 for an anchoring system for an underwater vehicle such as an AUV.

[0109] A release plate 2 may be fixed to a part of a structure 3 of the underwater vehicle or built into the structure 3 of the underwater vehicle.

[0110] The release plate 2 has an upper face 21 and a lower face 22. A first circular groove 221 is disposed on the lower face 22.

[0111] A flood tube 4 has an open end 41 sealed against the lower face 22 of the release plate 2 and a closed end 42 distal from the open end 41. The open end of the flood tube 4 comprises a second circular groove 411. A sealing ring 5 is disposed in the second circular groove 411 and the first circular groove 221. The sealing ring 5 fits snugly in the first circular groove 221. The second circular groove 411 is wider than the first circular groove 221 such that the first circular groove 221 is received partially in the second circular groove 411.

[0112] The air pressure within the flood tube 4 is a vacuum pressure, e.g. from 0.1 bar to 0.2 bar.

[0113] The release plate includes a vacuum port (not shown) connectable to a vacuum apparatus operable to apply a vacuum to the flood tube 4 as the flood tube is loaded, in use, into an underwater vehicle.

[0114] The flood tube 4 is held against the lower face 22 of the release plate 2 by a surface seal provided by the sealing ring 5. As will be described herein, the surface seal is overcome when the flood tube assembly 1 is deployed. It has been found that the surface seal may provide a reliable seal under all ground handling and operational conditions, while not in any way impeding release of the flood tube 4 when an anchoring operation is initiated.

[0115] One or more electrical connections (not shown) are provided on the release plate for connection to control circuitry required to execute an anchoring operation.

[0116] The flood tube 4 constitutes an example of a suitable buoyant body for use in an anchoring and / or payload delivery system for an underwater vehicle. Any given buoyant body, e.g. the flood tube 4, may be designed specifically for a given implementation. For instance, the wall thickness, diameter, material(s) and / or the length of the flood tube 4 may be selected to resist pressures encountered at operating depth and / or to displace sufficient water when under vacuum to ensure that the overall system (e.g. the flood tube assembly 1) is neutrally buoyant.

[0117] A tether 8 is attached at a first end to a first tether connector 10 attached to the release plate 2. A second end of the tether 8 is attached to a second tether connector 11 attached to the closed end 42 of the flood tube 4.

[0118] The tether 8 is stowed within the flood tube 4 and has a length greater than a length of the flood tube 4. As will be described elsewhere herein, the tether 8 spools out of the flood tube 4 during an anchoring operation.

[0119] The length of the tether 8 may be selected depending upon the intended application of the flood tube assembly 1, e.g. depending upon the underwater vehicle in which the flood tube assembly 1 is to be installed and / or the planned operations that the underwater vehicle is going to carry out on a given mission.

[0120] The tether 8 may comprise any suitable material or combination of materials. In an implementation, the tether 8 may include a length of a shock cord (e.g. an elastomeric cord) and a length of a chain.

[0121] In implementations, the tether 8 may comprise a length of a shock cord, a length of a load carrying tether and a length of a weighted chain. The lengths of the length of the shock cord, the length of the load carrying tether and / or the length of the weighted chain may be selected according to, for example, the mass of the underwater vehicle, a current anticipated at an intended anchoring location and / or anticipated ground conditions at the intended anchoring location. For instance, higher anticipated currents at the intended anchoring location may favour selection of a tether having a longer overall length. The length of the shock cord may help to absorb the impact of the buoyant body, e.g. the flood tube, falling away from the underwater vehicle after release. The mass of the weighted chain may help to ensure that the buoyant body, e.g. the flood tube, may lie flat against the seabed following impact of the anchor on the seabed. This may aid the holding power of the anchor, e.g. in silt, sand or mud. It may also reduce snatch loads from the underwater vehicle riding at anchor.

[0122] The tether 8 is stored in the flood tube 4 in vacuum until deployment. Consequently, the tether 8 may remain in relatively good condition until deployment, which may be an important consideration for long-and / or ultra-long endurance missions.

[0123] The tether 8 may be packed within the flood tube 4 in such a way the tether 8 freely uncoils from the flood tube 4 following release of the flood tube 4 from the release plate 2.

[0124] The flood tube assembly 1 includes a valve 6 operable to control flow of ambient water into the flood tube 4. The valve 6 is connected to the release plate 2. A valve actuation mechanism 7 is connected to the release plate 2 and operably connected to the valve 6.

[0125] Also connected to the release plate 2 is a tether release actuator 12. The tether release actuator 12 is operably connected to the first tether connector 10. After an anchoring period has passed, in use, a signal from the underwater vehicle is sent to the tether release actuator 12 to release the tether 8 from the first tether connector 10. The tether 8 may then be discarded with the flood tube 4. The underwater vehicle may then float free, with the overall buoyancy of the underwater vehicle now returned to its normal cruise configuration.

[0126] The structure of the valve actuation mechanism 7 is shown in detail in FIG. 2. The tether 8 has been omitted for clarity.

[0127] The valve actuation mechanism 7 includes a valve actuation arm 71. The valve actuation arm 71 is disposed a distance from the upper face of the release plate 2. A first end 79 of the valve actuation arm 71 is connected to the upper face 21 of the release plate 2 by a swinging pivot link 72.

[0128] At a first end, the swinging pivot link 72 is pivotally connected to the first end 79 of the actuation arm 71. At a second end, the swinging pivot link 72 is pivotally connected to a pivot link connector 73 attached to the upper face 21 of the release plate 2.

[0129] At an intermediate point along the length of the valve actuation arm 71, the valve actuation arm 71 is pivotally connected to a first end 611 of a valve stem 61. The valve 6 includes the valve stem 61 and a valve body 62. The valve body 62 is fixedly connected to the release plate 2 and extends through the release plate 2. The valve stem 61 is received in part in the valve body 62 and is moveable longitudinally relative to the valve body 62.

[0130] At a second end 75, the valve actuation arm 71 is attached via a Galvanic link 77 to a Galvanic link 78 actuator. The Galvanic link actuator 78 is operable to break the Galvanic link 77 to initiate an anchoring operation, as is described in more detail herein. The Galvanic link actuator 78 is fixedly mounted in the release plate 2.

[0131] A spring housing 74 has a mounting plate 742 at a first end, which is connected to the upper face 21 of the release plate 2. A valve actuation spring 76 is housed within the spring housing 74. A first end of the valve actuation spring 76 is connected to an inner surface of the spring housing 74 and a second end of the valve actuation spring 76 is connected to the valve actuation arm 71. The second end of the valve actuation spring 76 is connected to the valve actuation arm 71 at a point between the points at which the valve actuation arm 71 is connected to the valve stem 61 and the Galvanic link 77. The point at which the second end of the valve actuation spring 76 is connected to the valve actuation arm 71 is closer to the point at which the valve actuation arm 71 is connected to the Galvanic link 77 than it is to the point at which the valve actuation arm 71 is connected to the valve stem 61.

[0132] At an intermediate point along its length, the spring housing 74 includes a pair of slots 741a, 741b, which are arranged on opposite sides of the spring housing 74. The valve actuation arm 71 extends through the spring housing 74 via the slots 741a, 741b. The slots are configured such that the valve actuation arm 71 may move, in use, in a direction away from the release plate 2. The extent of movement of the valve actuation arm 71, in use, in the direction away from the release plate 2 is limited by the length of the slots 741a, 741b. Accordingly, the slots 741a, 741b provide a stop means configured to limit movement of the actuation arm 71, in use, in the direction away from the release plate 2.

[0133] As shown in FIG. 2, the valve actuation mechanism 7 is shown in its initial state, in which the valve actuation spring 76 is held under compression by virtue of the Galvanic link 77 holding the valve actuation arm 71 in place relative to the release plate 2.

[0134] The valve 6 is shown in detail in FIGS. 3 and 4. FIG. 3 shows the valve 6 in a closed state. FIG. 4 shows the valve 6 in an open state.

[0135] The valve body 62 constitutes a fixed part of the valve 6. The valve stem 61 constitutes a moveable part of the valve 6.

[0136] The valve body 62 comprises an elongate body 63 including an open end 631 and a closed end 632. An internal bore 64 of the valve body 62 extends longitudinally from the open end 631 to the closed end 632. At the open end 631, the valve body 62 includes a flange 633. The flange 633 extends radially outwardly from the elongate body 63.

[0137] At an intermediate point along the length of the elongate body 63, four flood ports 634 are spaced around a circumference of the elongate body 63. Each flood port 634 comprises an aperture extending through a thickness of a wall of the elongate body 63. The flood ports 634 are spaced equally around the circumference of the elongate body 63. In implementations, other numbers and arrangements of one or more flood ports may be employed.

[0138] Between the flood ports 634 and the flange 633, an outer surface of the elongate body 63 comprises a threaded portion 635. In use, the valve body 62 is fixedly connected to the release plate 2 by screwing in the valve body 62 such that the threaded portion 635 engages with a complementarily threaded aperture in the release plate 2. When the valve body 62 is fixedly connected to the release plate 2, the flange 633 sits adjacent the upper face 22 of the release plate2.

[0139] The first end 611 of the valve stem 61 is configured to be pivotally connected to the valve actuation arm 71. The valve stem 61 comprises an elongate body 65. The elongate body 65 extends into the internal bore 64.

[0140] A longitudinal passage 651 extends through the valve stem 61 from the first end 611 to a second end 612 opposite the first end 611. The longitudinal passage 651 is substantially uniform in cross-section along its length.

[0141] Towards the second end 612, a first sealing ring 661 sits in a first circumferential groove 681. A distance further from the second end 612. a second sealing ring 662 sits in a second circumferential groove 682. The first sealing ring 661 is configured to provide a fluid-tight seal between the valve stem 61 and an inner surface of the internal bore 64 of the valve body 62. The second sealing ring 662 is configured to provide a fluid-tight seal between the valve stem 61 and the inner surface of the internal bore 64 of the valve body 62. The first sealing ring 661 and the second sealing ring 662 move, in use, with the valve stem 61.

[0142] A third sealing ring 671 is mounted inside the flange 633. The third sealing ring 671 is configured to provide a fluid-tight seal between the valve stem 61 and the inner surface of the internal bore 64 of the valve body 62. The third sealing ring 671 does not move, in use, with the valve stem 61.

[0143] FIG. 3 shows the valve 6 in the closed state. In the closed state, the valve stem 61 is in a first position, in which the valve stem 61 is positioned such that the first sealing ring 661 and the second sealing ring 662 are disposed either side of the flood ports 634.

[0144] There is a portion of the internal bore 64 between the second end 612 of the valve stem 61 and the closed end 632 of the elongate body 63 of the valve body 62. The portion of the internal bore 64 between the second end 612 of the valve stem 61 and the closed end 632 of the elongate body 63 of the valve body 62 constitutes a pressure balance chamber 69.

[0145] When deployed in an anchoring and / or payload delivery system, the anchoring and / or payload delivery system is configured such that the first end 611 of the valve stem 61 is exposed to ambient water. Accordingly, the pressure balance chamber 69 is in fluid communication with ambient water via the longitudinal passage 651. Irrespective of depth, the valve stem 61 is pressure balanced within the valve body 62 by virtue of substantially equal ambient water pressures acting in opposing directions on the first end 611 of the valve stem 61 and the second end 612 of the valve stem 61. Typically, the areas of the valve stem 61 exposed to ambient water at each end of the valve stem may be equal or substantially equal and subjected, in use, to substantially the same ambient water, e.g. sea, pressure.

[0146] In the closed state, there is no fluid communication from the pressure balance chamber 69 to the flood ports 634.

[0147] FIG. 4 shows the valve 6 in the open state. In the open state, the valve stem is in a second position, in which the valve stem is positioned such that the valve stem 61 has moved longitudinally within the internal bore 64 such that fluid communication from the pressure balance chamber 69 to the flood ports 634 is allowed.

[0148] With reference to FIGS. 1, 2, 3 and 4, operation of the flood tube assembly 1 during an anchoring operation will now be described. When an underwater vehicle including an anchoring system including the flood tube assembly 1 is near a desired anchoring location, a signal is sent to the Galvanic link actuator 78 to initiate Galvanic corrosion of the Galvanic link 77. The ensuing Galvanic corrosion of the Galvanic link 77 causes the Galvanic link 77 to break, thereby releasing the valve actuation arm 71. The valve actuation spring 76 urges the valve actuation arm 71 to move in a direction away from the release plate 2.

[0149] The slots 741a, 741b in the spring housing 74 provide a limit to the extent of movement of the valve actuation arm 71 in the direction away from the release plate 2. As the valve actuation arm 71 is urged away from the release plate 2 by the valve actuation spring 76, the swinging pivot link 72 remains connected to the first end 79 of the valve actuation arm 71. The first end 79 of the valve actuation arm 71 moves towards the release plate 2 as the second end 75 of the valve actuation arm 71 moves away from the release plate 2. The valve stem 61 is moved from the first position to the second position by the valve actuation arm 71. As a consequence of the valve 6 being pressure balanced, the only force to be overcome by the actuation mechanism 7 in moving the valve stem 61 from the first position to the second position is friction, principally friction between the first sealing ring 661 and the inner surface of the internal bore 64 of the valve body 62, friction between the second sealing ring 662 and the inner surface of the internal bore 64 of the valve body 62 and friction between the third sealing ring 671 and the outer surface of the valve stem 61. By including the swinging pivot link 72 in the valve actuation mechanism 7, the valve stem 61 may not be subjected to any side loading during activation of the valve 6.

[0150] Through appropriate materials selection for the valve stem 61, the valve body 62, the first sealing ring 661, the second sealing ring 662 and the third sealing ring 663, a fluid-tight seal between the valve stem 61 and the valve body 62 may be maintained, even at elevated pressures such as would be encountered at depth. For instance, the fluid-tight seal between the valve stem 61 and the valve body 62 may be maintained at pressures of up to 700 bar or more.

[0151] As noted above, the only force to be overcome by the valve actuation mechanism 7 in moving the valve stem 61 from the first position to the second position is friction, principally friction between the first sealing ring 661 and the inner surface of the internal bore 64 of the valve body 62, friction between the second sealing ring 662 and the inner surface of the internal bore 64 of the valve body 62 and friction between the third sealing ring 671 and the outer surface of the valve stem 61. This force due to friction may be an example of a movement-resisting force between a stationary part, e.g. the valve body 62, and a moveable part, e.g. the valve stem 61, of a valve, e.g. the valve 6, that holds the moveable part in the first position. The movement-resisting force may comprise, or consist essentially of, a friction force. Additionally or alternatively, the movement-resisting force may comprise any suitable force, e.g. a magnetic force. A relatively simple, reliable valve actuation mechanism may be employed such as the valve actuation mechanism 7.

[0152] When the valve stem 61 is in the second position, i.e. when the valve 6 is in the open state, ambient water flows into the flood tube 4. The flood tube 4 then becomes negatively buoyant, eventually overcoming the surface seal. The flood tube 4 will then descend under gravity towards the seabed, since the flood tube assembly 1 may be fitted to the underwater vehicle at a location from which the flood tube 4 can fall under gravity away from the underwater vehicle without being impeded by any part of the underwater vehicle.

[0153] The flood tube 4 and the valve 6 may be configured to have a desired fill time, i.e. a period of time for water to fill (or flood) the flood tube 4 sufficiently to break the surface seal holding the flood tube 4 against the lower face 22 of the release plate 2. For instance, by varying the number, arrangement, sizes and / or dimensions of the flood ports 634, the desired fill time may be varied. In an example implementation, the flood tube assembly 1 may have a fill time of from 3 to 35 seconds, depending upon operating depth.

[0154] Similarly, the flood tube 4 and the valve 6 may be configured for operation at a desired depth, e.g. by varying the number, arrangement, sizes and / or dimensions of the flood ports 634.

[0155] The flood tube 4 remains connected to the underwater vehicle by the tether 8. The flood tube 4 provides a mass anchor. The flood tube 4 additionally may be relatively likely to snag on the seabed, due to the cup-or scoop-like shape of the flood tube 4.

[0156] In the valve 6, the valve stem 61 (i.e. the moveable part of the valve) is pressure balanced by virtue of substantially the same surface area of each end of the valve stem 61 being exposed, in use, to ambient water, e.g. sea water. Hence, irrespective of depth, when the valve 6 is in the closed state there is substantially no net force on the moveable part due to the pressure of the ambient water.

[0157] However, there will be some increase in the friction force(s) resisting movement of the valve stem (i.e. the moveable part) relative to the valve body (i.e. the stationary part) at higher depths, since the sealing element(s) (e.g. the surface seal, the first sealing ring, the second sealing ring and / or the third sealing ring) will be compressed relatively by the increased depth pressure of the ambient water.

[0158] In an implementation, the valve may be configured such that the friction force resisting movement of the moveable part relative to the stationary part may be around 1 kgf. For example, the valve actuation spring (or other suitable biasing means) may be selected to have a spring force (or equivalent) of around 6 kgf. The spring force may therefore be more than sufficient to overcome the friction force even at a depth of 1500 metres.

[0159] It will be appreciated that the spring force, or strength of another suitable biasing means, may be selected to be sufficient to overcome the friction force, or other movement-resisting force, at the intended deployment depth. To ensure reliable operation of the valve at depth, the spring force, or strength of another suitable biasing means, may be selected to be at least 1.5 times, up to or at least 2 times, up to or at least 3 times or up to or at least 5 times, the friction force, or other movement-resisting force, at the intended deployment depth.

[0160] Considering an example where the friction force resisting movement of the moveable part relative to the stationary part is 1 kgf at sea level, the applicant has found that if the valve were not pressure balanced, then the force resisting movement of the movement of the moveable part relative to the stationary part would be 184 kgf at a deployment depth of 1500 m. Consequently, a relatively strong and / or complicated valve actuation mechanism would be required.

[0161] In contrast, when the valve is pressure balanced as described herein, it has been found that the friction force resisting movement of the moveable part relative to the stationary part may be from 3 to 4 kgf at a deployment depth of 1500 m. Consequently, a relatively simple and / or reliable valve actuation mechanism may be employed. For instance, a spring with a spring force of around 6 kgf may be more than sufficient to overcome, in use, the friction force resisting movement of the moveable part relative to the stationary part at a deployment depth of 1500 m.

[0162] Without wishing to be bound by any theory, it is envisaged that a valve according to the present disclosure may be capable of being deployed at depths of up to, or even greater than, 6000 m, with appropriate selection of the valve actuation spring and the sealing elements.

[0163] It will be appreciated that, as a result of the valve being pressure balanced, the increase in holding and activation pressure forces between the stationary part and the moveable part due to changes in operating depth is substantially eliminated. Any changes in absolute holding forces and activation forces (i.e. movement-resisting force(s)), in use, between the moveable part and the stationary part may be limited to increases in friction in the sealing element(s) due to pressure changes. These changes may be relatively small. For instance, these changes may be less than 10%, less than 5%, or even less than 2%, of the change in the forces that would otherwise have to be reacted by the holding mechanism due to changes of depth if the valve were not pressure balanced.

[0164] FIGS. 7 to 10 illustrate a sequence of stages of an anchoring operation for an underwater vehicle fitted with an anchoring system comprising one or more flood tube assemblies according to the present disclosure. For instance, one or more, e.g. a plurality of, flood tube assemblies according to the present disclosure may be housed in a forward portion of an underwater vehicle. Any number of flood tube assemblies may be employed, depending upon the underwater vehicle in question and its specific deployment. For instance, the anchoring system may comprise up to or at least six flood tube assemblies, up to or at least 12 flood tube assemblies, up to or at least 20 flood tube assemblies or up to or at least 50 flood tube assemblies. In implementations, the anchoring system may comprise two flood tube assemblies, three flood tube assemblies, six flood tube assemblies, 12 flood tube assemblies or 18 flood tube assemblies.

[0165] In the example illustrated in FIGS. 7 to 10, an underwater vehicle in the form of an autonomous underwater vehicle (AUV) 100 is fitted with an anchoring system 101 comprising a first flood tube assembly 1′ and a second flood tube assembly 1″. The first flood tube assembly 1′ and the second flood tube assembly 1″ are disposed in a forward portion of the AUV 100. The first flood tube assembly 1′ and the second flood tube assembly 1″ are each substantially the same as the flood tube assembly 1 described above. Hence, like features are labelled with the same reference numerals, but with a prime (′) for features of the first flood tube assembly 1′ and a double prime (″) for features of the second flood tube assembly 1″. In implementations, one or more of the flood tube assemblies may be disposed in another portion of the AUV. One or more of the flood tube assemblies may be disposed in any portion of the underwater vehicle.

[0166] In FIG. 7, the AUV 100 is approaching a desired anchoring location. Hence, the flood tube 4′ of the first flood tube assembly 1′ has been flooded with ambient water, as described above. The flood tube 4′ has started to fall under gravity and fallen through a hole in an underside of the AUV 100. The hole in the underside of the AUV 100 may be permanently open or may be covered with a door or cover that remains in place until the anchoring operation begins. The door or cover may be configured to open when the anchoring operation is taking place and to close when the anchoring operation has been completed. The underwater vehicle, e.g. the AUV, may experience less drag when the hole(s) for deployment of the flood tube assemblies are covered with a door or cover that remains in place until the anchoring operation begins as compared with example(s) when the hole(s) for deployment of the flood tube assemblies are uncovered (i.e. permanently open). Accordingly, for example, the battery lifetime of the underwater vehicle may be longer for implementations, in which the hole(s) are covered with a door or cover that remains in place until an anchoring and / or payload delivery operation begins.

[0167] As shown in FIG. 8, as the flood tube 4′ descends, the tether 8′ unwinds. The AUV 100 may pitch forward, as a result of the flood tube 4′ being released.

[0168] FIG. 9 shows the flood tube 4′ acting as a mass anchor on a portion of seabed 102. The AUV 100 is anchored to the portion of seabed. The AUV 100 may be powered down or switched to a low power mode for a period of time until it is required to carry out another operation or travel to a different location.

[0169] When it is time for the AUV 100 to travel to a different location, a signal is sent to the tether release actuator 12′, which operates to release the tether 8′ from the first tether connector 12′. For example, the tether release actuator 12′ may release the tether 8′ by opening a hook or loop or by cutting the tether 8′. The AUV 100 is then disconnected from the flood tube 4′. As shown in FIG. 10, the tether 8′ and the flood tube 4′ are left on the seabed 102 and the AUV 100 can then travel to its next anchoring location where the second flood tube assembly 1″ may be employed to anchor the AUV 100 in place. After any number, e.g. all, of the flood tube assemblies in the anchoring system, the AUV 100 may travel back to the location, e.g. a ship or dock, from which it was launched. By releasing the tether 8′, the risk of snagging as the AUV 100 travels away for the anchoring location may be reduced, thereby increasing the likelihood of the AUV 100 successfully completing its mission.

[0170] FIG. 5 shows a cross-sectional view of another example of a flood tube assembly 1000 for an anchoring system for an underwater vehicle.

[0171] A release plate 1002 may be fixed to a part of a structure 1003 of the underwater vehicle or built into the structure 1003 of the underwater vehicle.

[0172] The release plate 1002 has an upper face 1021 and a lower face 1022.

[0173] A first end 1041 of a flood tube 1004 is attached to the lower face 1022 of the release plate 1002. An end cap 1042 is sealed against a second end 1043 of the flood tube 1004. A sealing ring 1005 is disposed between the end cap 1042 and the second end 1043 of the flood tube 1004. The sealing ring 1005 may be connected to the second end 1043 of the flood tube 1004 or the end cap 1042.

[0174] The air pressure within the flood tube 1004 is a vacuum pressure, e.g. from 0.1 bar to 0.2 bar. Hence, there is a surface seal between the end cap 1042 and the second end 1043 of the flood tube 1004. The surface seal holds the end cap 1042 in place against the second end 1043 of the flood tube 1004. The surface seal is overcome when the flood tube assembly 1000 is deployed.

[0175] A tether 1008 is attached at a first end to a first tether connector 1010 attached to the release plate 1002. A second end of the tether 1008 is attached to a second tether connector 1011 attached to the end cap 1042.

[0176] The tether 1008 is stowed within the flood tube 1004 and has a length greater than a length of the flood tube 1004. The tether 1008 spools out of the flood tube 1004 during an anchoring operation.

[0177] The length of the tether 1008 may be selected depending upon the intended application of the flood tube assembly 1000, e.g. depending upon the underwater vehicle in which the flood tube assembly 1000 is to be installed and / or the planned operations that the underwater vehicle is going to carry out on a given mission.

[0178] The tether 1008 may comprise any suitable material or combination of materials. In an implementation, the tether 1008 may include a length of a shock cord (e.g. an elastomeric cord) and a length of a chain.

[0179] The flood tube assembly 1000 includes a valve 1006 operable to control flooding of the flood tube 1004. The valve 1006 is connected to the release plate 1002. A valve actuation mechanism 1007 is connected to the release plate 1002 and operably connected to the valve 1006.

[0180] Also connected to the release plate 1002 is a tether release actuator 1012. The tether release actuator 1012 is operably connected to the first tether connector 1010.

[0181] The valve 1006 operates in substantially the same manner as the valve 6 described above. The valve actuation mechanism 1007 operates in substantially the same manner as the valve actuation mechanism 7 described above. Similarly, the tether release actuator 1012 operates in substantially the same manner as the tether release actuator 12 described above.

[0182] The only significant difference between the flood tube assembly 1000 and the flood tube assembly 1 is that the end cap 1042 provides the mass anchor when the flood tube assembly 1000 is deployed in an anchoring operation, as opposed to the flood tube 4 providing the mass anchor when the flood tube assembly 1 is deployed in an anchoring operation. Consequently, relatively less material may be discarded after each anchoring operation. The mass of the end cap 1042 may be selected such that it is sufficient to provide, in use, an effective mass anchor.

[0183] FIG. 6 shows a cross-sectional view of an example of a flood tube assembly 2000 for a payload delivery system for an underwater vehicle.

[0184] A release plate 2002 may be fixed to a part of a structure 2003 of the underwater vehicle or built into the structure 2003 of the underwater vehicle.

[0185] The release plate 2002 has an upper face 2021 and a lower face 2022.

[0186] A first end 2041 of a flood tube 2004 is attached to the lower face 2022 of the release plate 2002. An end cap 2042 is sealed against a second end 2043 of the flood tube 2004. A sealing ring 2005 is disposed between the end cap 2042 and the second end 2043 of the flood tube 2004. The sealing ring 2005 may be connected to the second end 2043 of the flood tube 2004 or the end cap 2042.

[0187] The air pressure within the flood tube 2004 is a vacuum pressure, e.g. from 0.1 bar to 0.2 bar. Hence, there is a surface seal between the end cap 2042 and the second end 2043 of the flood tube 2004. The surface seal holds the end cap 2042 in place against the second end 2043 of the flood tube 2004. The surface seal is overcome when the flood tube assembly 2000 is deployed.

[0188] A payload 2008 is attached at a first end to a first payload connector 2010 attached to the release plate 2002. A second end of the payload 2008 is attached to a second payload connector 2011 attached to the end cap 2042.

[0189] The payload 2008 is stowed within the flood tube 2004. The payload 2008 may be selected depending upon the intended mission of the underwater vehicle. The payload 2008 may be a negatively buoyant payload or a positively buoyant payload. A negatively buoyant payload may be intended to be delivered to the sea bead. A positively buoyant payload may be intended to float to the surface after operation of the payload delivery system at a desired location.

[0190] Also connected to the release plate 2002 is a payload release actuator 2012. The payload release actuator 2012 is operably connected to the first tether connector 2010.

[0191] The valve 2006 operates in substantially the same manner as the valve 6 described above. The valve actuation mechanism 2007 operates in substantially the same manner as the valve actuation mechanism 7 described above. Similarly, the payload release actuator 2012 operates in substantially the same manner as the tether release actuator 12 described above.

[0192] During a payload delivery operation, the valve actuation mechanism 2007 and the valve 2006 operate to flood the flood tube 2004. The payload release actuator 2012 also operates on the first payload connector 2010 to release the payload 2008. The end cap 2042 descends from the flood tube 2004 under gravity with the payload 2008 attached thereto by the second payload connector 2011.

[0193] If the payload 2008 is intended to be delivered to the seabed, then the payload 2008 may remain connected to the end cap 2042 by the second payload connector 2011. The end cap 2042 may assist in anchoring the payload 2008 on the seabed.

[0194] If the payload 2008 is intended to be delivered to the surface (or a lower depth), then the payload 2008 may be positively buoyant and the second payload connector 2011 may be configured to break at some time after deployment of the flood tube assembly 2000. The end cap 2042 may then pull the payload 2008 down away from the underwater vehicle before the second payload connector breaks 2011 to release the payload 2008, thereby allowing the payload 2008 to float upwards to or toward the surface of the water.

[0195] Any suitable means operable to break the second payload connector 2011 or otherwise release the payload 2008 from the end cap 2042 may be employed, depending, for example, upon the timing required for a particular mission. The means operable to break the second payload connector 2011 or otherwise release the payload 2008 from the end cap 2042 may include, for example, a tether-activated latch release, a timer release or a chemical link. The tether-activated latch release may be configured to be activated after the payload has fallen through a predetermined distance from the underwater vehicle. The timer release may be configured to be activated after the expiry of a predetermined period of time. The chemical link may be configured to dissolve after a set period of time exposed to ambient water, e.g. sea water.

[0196] The payload 2008 may include a payload housing and a payload device stored within the payload housing. The payload housing may comprise a tube. The payload housing may protect the payload device from environmental or other damage until the flood tube assembly is actuated to deliver the payload. The payload housing may fall under gravity from the underwater vehicle. The payload housing may be configured to release the payload device after a predetermined time.

[0197] The present disclosure may provide a means for delivering a payload, e.g. a payload device, while an underwater vehicle such as an AUV or ROV is submerged. In order to do this, any buoyancy change to the underwater vehicle needs to be compensated for on payload release in order to maintain underwater vehicle trim. By carrying the payload to be delivered within a flood tube, release of the payload, and adjustment of underwater vehicle buoyancy may be accommodated with a single trigger signal.

[0198] Benefits of carrying and deploying payloads in this way may include:

[0199] Automatic adjustment of underwater vehicle buoyancy on release of the payload.

[0200] The payload is stored in air, e.g. within the flood tube or within a payload housing contained in the flood tube, until release, which may help to protect the payload from corrosion and damage. This may be important for longer-duration missions, in particular, when it is envisaged that a given payload may be stored for up to a year or more before deployment. Another consequence of the payload being stored in air is that data transfer between the payload, e.g. the payload device, and the underwater vehicle may be relatively straightforward and may use one or more data transfer means such as Bluetooth®, WiFi or easy-release contact for communications that would not be usable if the payload were stored in a flooded environment. Such data transfer means do not impeded release of the payload in any way, which may reduce the chances of deployment failing.

[0201] Generally, it is envisaged that a payload delivery system according to the present disclosure may be employed to deliver one or more negatively buoyant payloads and / or one or more positively buoyant payloads. On release, a negatively buoyant payload would sink towards the seabed. On release, a positively buoyant payload may be designed to float to the sea surface. For instance, a positively buoyant payload may include a communications buoy designed to relay data from the underwater vehicle via a satellite link to a remote location. The data may then be processed and / or analysed at the remote location.

[0202] A payload delivery system according to the present disclosure may be configured to release a payload, in use, in any direction relative to the underwater vehicle. A payload delivery system according to the present disclosure may be configured to release a payload, in use, in an upwards direction or a downwards direction relative to the underwater vehicle.

[0203] In the illustrated examples, the valve actuation mechanisms include a valve actuation arm, which may be connected to a release plate by a swinging pivot link. A valve actuation mechanism including a valve actuation arm may, in some instances, make packaging of the flood tube assembly relatively space-efficient, since the Galvanic link actuator may be positioned to one side of the flood tube, which may reduce the overall height of the flood tube assembly. Nevertheless, the person skilled in the art will appreciate that any suitable valve actuation mechanism may be employed.

[0204] It will further be appreciated that the Galvanic link, e.g. a Galvanic burn wire, employed in the illustrated example valve actuation mechanisms may provide a reliable and low power means of actuating the valve. In use, only a relatively low voltage and low current need be applied across the Galvanic link, to initiate corrosion of the Galvanic link due to Galvanic action that weakens and / or breaks the Galvanic link, thereby releasing valve actuation arm. However, any convenient means of actuating the valve may be employed instead of a Galvanic link. Such means may include, for example, a fuse link, a flash wire, a solenoid or other magnetic or electromagnetic release, a timed Galvanic release, a melt wire or a burn wire.

[0205] It will be appreciated that the flood tubes of the illustrated examples merely constitute examples of suitable buoyant bodies. Such buoyant bodies may have shapes and dimensions different from those of the flood tubes of the example implementations illustrated and described herein.

[0206] An anchoring and / or payload delivery system for an underwater vehicle may comprise any number and / or combination of flood tube assemblies disclosed herein. For example, an anchoring and / or payload delivery system for an underwater vehicle may comprise any number and or combination of the flood tube assembly 1, the flood tube assembly 1000 and / or the flood tube assembly 2000.

[0207] For example, in an implementation comprising a plurality of flood tube assemblies one or more of the flood tube assemblies may be configured for anchoring and one or more of the flood tube assemblies may be configured for payload delivery.

[0208] In an implementation, a flood tube assembly may be configured for anchoring and payload delivery. In such an implementation, the flood tube may contain a payload and a tethered anchor. The payload may be intended to be delivered at the same time as the anchor is deployed.

[0209] While the examples have generally been described with reference to AUVs, it will be appreciated that the present disclosure may be applied to any kind of underwater vehicle, including, for example, ROVs.

[0210] For example, it is envisaged that the present disclosure may be applied to an Autosub Long Range (or Autosub LR) AUV operated by the National Oceanography Centre. The Autosub LR AUV may have a range of 2000 km and a depth rating of 6000 m. An anchoring and / or payload delivery system comprising one or more flood tube assemblies may be fitted to the Autosub LR AUV. Typically, a plurality of flood tube assemblies may be fitted into a forward portion of the Autosub LR AUV. For instance, an anchoring and / or payload delivery system comprising two or three flood tube assemblies may be fitted into the forward portion of the Autosub LR AUV. In implementations, the forward portion of the Autosub LR AUV may be extended in order to accommodate an anchoring and / or payload delivery system comprising a higher number of flood tube assemblies, e.g. an anchoring and / or payload delivery system comprising 10, 12 or more flood tube assemblies.

[0211] The Autosub LR AUV may have a typical maximum free-swimming endurance of 6 to 8 weeks. It is envisaged that the Autosub LR AUV may be capable of carrying out underwater operations lasting for around a year if fitted with an anchoring system comprising 10 or 12 flood tube assemblies. Hence, for example, the Autosub LR AUV may be able to operate at depth to carry out a longer-term survey of the ocean under Antarctic ice.

[0212] In an example, the Autosub LR AUV was fitted with an anchoring system comprising two flood tube assemblies. Each one of the two flood tube assemblies was essentially the same as the flood tube assembly 1 described herein. In this example, the flood tube 4 was configured to displace a little over 6 litres of water, making the AUV 4 kgf heavier after flooding, with the water-filled flood tube 4 providing a 4 kg mass anchor when touching down on the seabed.

[0213] Referring to FIGS. 11, 12 and 13, there is shown a portion of an AUV 100′ comprising an anchoring and / or payload delivery system 101′ according to the present disclosure. One of the flood tube assemblies 1′″ (FIG. 11) of the anchoring and / or payload delivery system 101′ is shown and may be any flood tube assembly disclosed herein.

[0214] The flood tube assembly 1′″ is configured to fall, in use, out of the AUV 100′ through an opening in an outer surface 105 of the AUV 100′. A door 103 in is configured to cover the opening in the outer surface 105 of the AUV 100′. The door 103 is configured to provide a smooth hydrodynamic surface when the door is in a closed position, as shown in FIG. 11 or FIG. 13. The door 103 may be considered a skin fairing flap or flaps.

[0215] In the illustrated example, the door 103 comprises a pair of flaps 104 (FIG. 12), which are lightly biased, e.g. sprung, towards the closed position. Following release, the weight of the flood tube or end portion may be sufficient to push the flaps 104 to an open position (FIG. 12). The tether (not shown) keeps the flaps 104 partially open, e.g. while the AUV 100′ is at anchor.

[0216] When the tether is released, the buoyancy of the released AUV 100′ in combination with the mass of the tether, pull the tether clear of the door and the flaps 104 then return to the closed position (FIG. 13). Accordingly, the empty flood tube assembly position may be fully faired during subsequent cruise of the AUV 100′ with minimal drag penalty. Without doors such as these such skin fairing flaps, it is envisaged that the cumulative drag penalty over the course of a mission could be very significant, particularly for an anchoring and / or payload delivery system comprising a significant number, e.g. six, 10 or 12 flood tube assemblies, as might be employed for a long-or ultra-long duration mission.

[0217] The present disclosure may be useful for a wide range of applications, including surveying, reconnaissance and / or payload delivery, particularly, but not exclusively, for longer-term missions, e.g. missions that are intended to last for longer than a given underwater vehicle's power source, e.g. battery, under normal, continuous operating conditions. Applications may include environmental and oceanographic science, monitoring and oil and gas exploration and production sites, monitoring subsea carbon capture and storage sites, prospecting and / or monitoring subsea mining sites.

[0218] The present disclosure may facilitate one or more of the following capabilities:

[0219] Extended operation of an underwater vehicle in an area of interest, thereby enabling, for example, observations to be taken over an extended period of time.

[0220] Operation of an underwater vehicle, e.g. an AUV, in remote and / or difficult-to-access locations. Such remote and / or difficult-to-access locations may include locations under Arctic or Antarctic ice, where access for deployment may only be possible at limited times of the year due to sea ice, but observations are required at other times.

[0221] Silent acoustic observation with an underwater vehicle, e.g. an AUV, anchored at a location of interest. Silent acoustic observations typically cannot be made while the underwater vehicle is in motion. By providing an anchoring system containing a plurality of flood tube assemblies, during a single mission the underwater vehicle may be anchored at a plurality of locations of interest and silent acoustic observations and / or any other type of observations may be carried out at one or more, e.g. all, of the locations of interest.

[0222] An anchoring system according to the present disclosure may enable an underwater vehicle, e.g. an AUV, to act as a virtual mooring, which may boost the time observations can be made from an underwater vehicle in locations that would not be accessible for more conventional fixed mooring strategies.

[0223] It will be understood that the present disclosure may be employed at depths in excess of 1500 m. The present disclosure may be fitted to underwater vehicles of any depth rating.

[0224] While the invention has been described in terms of subsea operations, it will be appreciated that the invention may be utilised in freshwater locations, e.g. reservoirs, lakes and / or rivers, as well as or instead of in saltwater locations.

[0225] An anchoring and / or payload delivery system according to the present disclosure may be capable of being retro-fitted to an existing underwater vehicle. Alternatively, the anchoring and / or payload delivery system according to the present disclosure may be incorporated within an underwater vehicle when the underwater vehicle is built initially.

[0226] An anchoring and / or payload delivery system according to the present disclosure may be configurable for an intended mission or deployment.

[0227] An anchoring and / or payload delivery system according to the present disclosure may have a relatively low cost of operation and / or a relatively high reliability of operation. Having a high reliability of operation may be important, since it may reduce the risk of losing an AUV during a mission, especially during a long-or ultra-long duration mission when it could be a significant length of time from the start of the mission to deployment of the anchoring and / or payload delivery system.

[0228] It will be understood that the invention is not limited to the above-described implementations and various modifications and improvements can be made without departing from the concepts herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

Claims

1. A valve for controlling flow of ambient water into a buoyant body in an anchoring and / or payload delivery system for an underwater vehicle, the valve comprising:at least one valve inlet configured to be open, in use, to ambient water;at least one valve outlet configured to communicate with the buoyant body;a pressure balance chamber in fluid communication with one or more of the valve inlets and thereby configured to be open, in use, to ambient water;a stationary part;a moveable part arranged to be exposed at least partially to ambient water and configured to move, in use, relative to the stationary part between a first position, wherein the valve is in a closed state in which fluid communication from the valve inlet(s) to the valve outlet(s) is prevented and a second position, wherein the valve is in an open state in which fluid communication from the valve inlet(s) to the valve outlet(s) is allowed, thereby allowing ambient water to flow into the buoyant body;wherein a first part of the moveable part is exposed to ambient water and a second part of the moveable part is exposed to water within the pressure balance chamber so that the moveable part is pressure balanced such that when the valve is in the closed state there is substantially no net force on the moveable part due to the pressure of the ambient water; andwherein the valve is configured such that a movement-resisting force between the stationary part and the moveable part holds the moveable part in the first position, in use, until a valve actuation mechanism is operated to overcome the movement-resisting force and move the moveable part to the second position.

2. The valve of claim 1, wherein the moveable part is at least one of (1) received at least in part in the stationary part or vice versa or (2) moveable linearly relative to the stationary part.

3. The valve of claim 1, wherein a passage disposed at least in part within the moveable part connects the valve inlet to the pressure balance chamber, optionally wherein the passage connecting the valve inlet to the pressure balance chamber extends from a first end of the moveable part to a second end of the moveable part.

4. The valve of claim 1, wherein the movement-resisting force comprises, or consists essentially of, a friction force and / or a magnetic force.

5. The valve of claim 1, wherein the valve outlet(s) comprise one or more flood ports.

6. The valve of claim 1 comprising one or more sealing means configured to provide a fluid-tight seal between the stationary part and the moveable part.

7. An anchoring and / or payload delivery system for an underwater vehicle comprising:at least one valve according to claim 1;a buoyant body downstream of the or each valve, the or each buoyant body containing air at a reduced pressure;a surface seal between an end of one or more of the buoyant bodies and a release plate, each surface seal being configured to hold one of the buoyant bodies in place against the release plate and / or a surface seal between a first part of one or more of buoyant bodies and a second part of the one or more buoyant bodies, the surface seal being configured to hold the second part of the buoyant body in place against the first part of the buoyant body; anda valve actuation mechanism operably connected to one or more of the valves, the valve actuation mechanism being operable to overcome the movement-resisting force and move the moveable part of a given valve to the second position, thereby allowing water to flow into the buoyant body downstream of the given valve such that the buoyancy of the buoyant body downstream of the given valve changes sufficiently for the surface seal to be overcome, thereby releasing the buoyant body from the release plate or the second part of the buoyant body from the first part of the buoyant body.

8. The anchoring and / or payload delivery system of claim 7 comprising a tether housed at least partially within one or more of the buoyant bodies.

9. The anchoring and / or payload delivery system of claim 8, wherein the tether connects the buoyant body or the second part of the buoyant body to the or a release plate and optionally comprising a tether release actuator operable to release the tether from the release plate.

10. The anchoring and / or payload delivery system of claim 7, wherein the second part of the buoyant body is configured to act as a mass anchor and / or the buoyant body is configured to act as a mass anchor.

11. The anchoring and / or payload delivery system of claim 7, wherein one or more of the buoyant bodies contain a payload, optionally.wherein the payload or a payload housing is releasably connected to the buoyant body, the second part of the buoyant body and / or the or a release plate.

12. The anchoring and / or payload delivery system of claim 7, wherein one or more of the surface seals is / are provided at least in part by a sealing element.

13. The anchoring and / or payload delivery system of claim 7, wherein the reduced pressure of air in the or each buoyant body is a vacuum pressure.

14. The anchoring and / or payload delivery system of claim 7, wherein the valve actuation mechanism comprises a holding means for holding directly or indirectly the moveable part in the first position and an actuator operably connected to the holding means, wherein the actuator is operable to cause the holding means to release the valve actuation mechanism, wherein, once released, the moveable part of the valve is free to move from the first position to the second position, optionally wherein the valve actuation mechanism comprises a biasing means configured to bias the moveable part of the valve from the first position towards the second position.

15. The anchoring and / or payload delivery system of claim 7 comprising up to or at least two, up to or at least three, up to or at least six, up to or at least 10, up to or at least 12, up to or at least 20 or up to or at least 50 buoyant bodies.

16. An underwater vehicle comprising an anchoring and / or payload delivery system according to claim 7.

17. The underwater vehicle of claim 16, wherein the anchoring and / or payload delivery system is disposed at least partially in a forward portion of the underwater vehicle and / or wherein the underwater vehicle is configured such that the buoyant body or part thereof released in an anchoring and / or payload delivery operation exits unimpeded from the underwater vehicle.

18. The underwater vehicle of claim 16 comprising one or more doors or covers configured to open to allow one or more of the buoyant bodies to exit the underwater vehicle during an anchoring and / or payload delivery operation.

19. A method of delivering a payload from an underwater vehicle comprising:operating an underwater vehicle according to claim 16; andwhile the underwater vehicle is submerged, deploying the payload delivery system to release the payload from the underwater vehicle.

20. A method of carrying out a mission using an underwater vehicle comprising:operating an underwater vehicle according to claim 16;directing the underwater vehicle along a route submerged within a body of water, the route including at least one desired anchoring location;deploying the anchoring system to anchor the underwater vehicle at each of the desired anchoring locations; andafter a period at anchor at a given desired anchoring location, releasing the anchor from the underwater vehicle and, optionally, directing the underwater vehicle along a subsequent section of the route.

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