Subsea surveying apparatus

Abstract

The present disclosure relates to an apparatus for use with one or more sensors to detect a subsea object. The apparatus comprises a structure which is configured to be towed in water by a vehicle. The structure comprises modular sections. Unlocking insights from Geo-Data, the present invention further relates to improvements in sustainability and environmental developments: together we create a safe and liveable world.

Description

SUBSEA SURVEYING APPARARATUSTECHNICAL FIELD

[0001] This disclosure relates to an apparatus for use with one or more sensors to detect a subsea object. The disclosure further relates to a method of manufacturing the apparatus. The disclosure further relates to a kit of parts for use with one or more sensors to detect a subsea object. Unlocking insights from Geo-Data, the present invention further relates to improvements in sustainability and environmental developments: together we create a safe and liveable world.BACKGROUND

[0002] There is a general and ongoing need to improve the safety and efficiency of subsea surveying. Subsea surveying involves scanning marine environments to detect submerged objects, such as unexploded items of ordnance (UXO), anchors, and cables. Detection of objects like these is especially important for subsea construction projects, like the construction of wind farms.

[0003] In particular, there is a need for a subsea object detection apparatus which can be used with sensors to scan the marine environment to detect such submerged objects which is safer and which exhibits greater operability than existing approaches.

[0004] A known approach to subsea surveying is to deploy a wing-like structure in the marine environment, that structure being equipped with sensors of a kind suitable for detecting the object(s) to be detected. For example, in the case of detecting UXOs, the structure is equipped with magnetometers. The magnetometers are arranged such that, when the structure is towed through the marine environment, it is possible for variations in both vertical and transverse magnetic gradients to be detected. This enables ferrous signatures from background geological noise and motion noise to be almost entirely removed. This allows ferrous signatures from objects of interest - such as UXO - to be identified, and UXO subsequently detected. In the known approach, the structure is configured to be towed in the sea by a vehicle, such as a Remotely Operated Towed Vehicle (ROTV). In turn, the ROTV is typically towed by a vessel, such as a ship, from which the structure is launched and recovered.

[0005] There is a specific opportunity to improve the safety and operability of the known approach to subsea surveying, as will now be described. The wing-like structure of the known approach is - as is common for offshore equipment - relatively heavy. While being heavy weight enhances durability in harsh marine environments, such weight also leads not only to operability challenges, but presents a safety risk to personnel on board the vessel. This is especially the case during launch and recovery of the structure to and from the sea when, typically, the relatively heavy structure is manipulated from the vessel to the sea using a single lifting point. It can be difficult to control the motion of the structurewhile being lifted, especially during adverse weather conditions, which presents a safety risk to on board personnel.

[0006] Turning to operability, the operability of (that is, ability to use) the structure is important for reasons of operational efficiency. There is a specific opportunity to improve the operability of the structure of the known approach, as will now be explained. First, the relatively heavy weight of the known structure means that, due to the described safety issues, the known structure cannot be used in adverse weather conditions. This leads to reduced operability. Second, the maintenance and repair of the known structure and the sensors it carries is challenging and time consuming. This is in part because, typically, extensive disassembly of the structure is required. This leads to significant periods of downtime for maintenance, further reducing operability. Finally, again linked to its weight, the likelihood of the known structure being damaged upon impact with the vessel, water or seabed, is significant. Naturally, any such damage necessitates repair of the structure, still further reducing its operability.

[0007] There is thus a need for an improved apparatus for using with one or more sensors to detect a subsea object. This disclosure aims to solve at least one of the abovementioned problems associated with subsea object detection apparatus.OVERVIEW

[0008] An apparatus for use with one or more sensors to detect a subsea object is disclosed. The apparatus comprises a structure which is configured to be towed in water by a vehicle. The structure comprises modular sections. The modular sections comprise a first sensor housing section, a second sensor housing section, and at least one longitudinal section. The first sensor housing section is releasably coupled to one end of the longitudinal section. The second sensor housing section is releasably coupled to the other end of the longitudinal section. Each of the first and second sensor housing sections is arranged to house a sensor for detecting the subsea object.

[0009] Advantageously, the modular design of the apparatus allows for quicker assembly and disassembly of the apparatus. This reduces operational downtime for maintenance and repair. In particular, due to the modular design, access to sensors housed in the sensor housing sections is straightforward due to the releasable coupling between each sensor housing section and the longitudinal section. This reduces the downtime associated with maintaining and replacing sensors. Furthermore, as a result of the modular design, the apparatus may be formed from lighter weight materials. This increases safety for personnel handling the apparatus because the apparatus is easier to control during launch and recovery of the apparatus to and from the sea. The opportunity to use lighter weight materials also increases operability, because - due it being safer to launch and recover - it is possible to use the apparatus in more adverse weather conditions. Further still, due to it being lighter weight, the likelihood of the structure being damaged upon impact with the vessel, water or seabed is lower, and indeed anysubsequent maintenance or repair required is faster to execute, as already discussed. Finally, the modular design of the apparatus allows for more modular sections to be added. For example, for more longitudinal and sensor housing sections to be added. As a result, the width of the apparatus in the direction generally perpendicular to the tow direction can be easily increased, as needed. This results in a more versatile apparatus and one that can result in fewer scan survey lines or infdl lines being required, which results in more efficient surveying.

[0010] In some examples, the longitudinal section has a substantially airfoil-shaped cross-section. For example, the longitudinal section may have the cross-sectional shape of the National Advisory Committee for Aeronautics (NACA) 0010 airfoil. Specifically, the substantially airfoil-shaped crosssection may: be substantially symmetrical about the airfoil chord; have a maximum thickness of around 10% of the chord length; and have no camber (that is, have a camber line coincident with the chord).

[0011] Advantageously, having an airfoil-shaped cross-section results in lower drag load when the apparatus is towed through the water. This lowers the energy requirements of the system.

[0012] In addition, and likewise advantageously, having an airfoil-shaped cross-section results in improved fluid flow stability properties. This reduces high-frequency vibrations and pitch and roll angle variation. Ultimately this leads to more accurate and / or reliable sensor results, and thus object detection. Furthermore, having an airfoil-shaped cross-section may result in a lift force on the longitudinal section such that flight height of the apparatus may be adjusted. For example, if it is desired to fly the apparatus at a greater depth in relation to the water surface, the airfoil-shaped cross-section may be adjusted such that a downward facing net force is effectuated through the interactions of the water with the longitudinal section, pressing the apparatus further down.

[0013] Sections may be releasably coupled using one or more releasable coupling means. Releasable coupling means may comprise bolts (such as brass bolts), clips, latches, and / or snap-fit connections.

[0014] In some examples, the apparatus comprises one or more sensors for detecting the subsea object. Each sensor may be housed in a respective one of the sensor housing sections.

[0015] Advantageously, the arrangement of each sensor in a respective sensor housing section allows for both better protection of the sensors and results in better fluid flow around the sensor, which leads to more accurate results. This is because housing the sensors in sensor housing sections results in smoother flow around the sensors. This reduces the presence of vibrations or distortions caused from turbulent flow, which can affect the sensors readings. Additionally, housing the sensors in their sensor housing sections ensures the sensors remain stable and properly orientated, again leading to more accurate data.

[0016] In some examples, the one or more sensors are magnetometers, acoustic sensors, or a combination of magnetometers and acoustic sensors. The apparatus may be configured to detect a subsea object comprising ferromagnetic material, such as underwater UXO. When the apparatus isconfigured to detect a subsea object comprising ferromagnetic material, the one or more sensors may be one or more magnetometers.

[0017] Advantageously, the use of magnetometers allows for variations in magnetic field to be detected. Since any ferrous object, including UXOs, alters the magnetic field, the use of magnetometers allows for the location of objects such as UXOs to be detected. Naturally, it is extremely important that UXOs are detected and addressed before subsea construction projects begin. Advantageously, the use of acoustic sensors can be used instead of, or in combination with, the use of other sensors, including magnetometers. The use of acoustic sensors to locate subsea objects by detecting sound waves reflected by the object further increases the quality of survey data.

[0018] In some examples, at least one of the sensor housing sections comprises at least one protruding portion, the at least one protruding portion being releasably received by the longitudinal section. The at least one sensor housing section may generally have a substantially circular shaped cross-section, and the at least one protruding portion may protrude in a radial direction. That is, the at least one protruding portion may be a radially protruding portion. The at least one protruding portion may protrude from the portion of the sensor housing section having the substantially circular shaped cross-section. The portion of the sensor housing section having the substantially circular shaped crosssection may be a hollow core. The at least one protruding portion may extend along around half of the axial length of the at least one sensor housing section. Alternatively, the at least one protruding portion may extend along less than half of the axial length of the at least one sensor housing section.

[0019] Advantageously, the use of a protruding portion allows for straightforward assembly (and reassembly) of the apparatus, and a resulting robust apparatus with improved structural integrity. This is for numerous reasons, including the following. First, because the protruding portion serves to position the at least sensor housing section correctly with respect to the longitudinal section. This helps guarantee correct assembly. Second, because the overlap provides structural integrity. Third, because the overlap serves as a convenient site for the two parts to be fixed together using, for example, bolts. Further advantageously, when there is a plurality of protruding portions, the at least one sensor housing may be easily assembled (and reassembled) with a plurality of other sections of the apparatus.

[0020] In some examples, at least one of the sensor housing sections is arranged to releasably receive the sensor it is arranged to house.

[0021] Advantageously, having releasable sensors allows for quick and straightforward installation and removal of the sensors, thus reducing assembly times and operational downtime for repair.

[0022] In some examples, at least one of the sensor housing sections comprises a nose section and a joining section. The joining section or the nose section may be arranged to house (and optionally releasably receive) the sensor for detecting the subsea object. The nose section and the joining section may be releasably coupled to each other.

[0023] Advantageously, the provision of the sensor housing section as two parts - with a nose section and a joining section - means that the sensor housed within may be accessed without having to decouple the sensor housing section from the main structure (or indeed even from the longitudinal section it is releasably coupled to). Instead, the nose section may, for example, be decoupled from the joining section, and the sensor housed within easily accessed.

[0024] In some examples, the joining section is substantially T-shaped. For example, the joining section may comprise: a hollow core having a substantially circular shaped cross-section; and three radially protruding portions. In this example, two of the radially protruding portions may be arranged substantially opposite each other, and the other of the radially protruding portions may be arranged substantially equidistant between the two opposing radially protruding portions. Such an arrangement is advantageous when the joining section is arranged as an external component of the apparatus, for example.

[0025] In some examples, the joining section is substantially X-shaped. For example, the joining section may comprise: a hollow core having a substantially circular shaped cross-section; and four radially protruding portions. In this example, the radially protruding portions may be arranged substantially equally around the core. That is, with around 45 degrees between them. Such an arrangement is advantageous when the joining section is arranged as an internal component of the apparatus, for example. This would be the case when there are three layers of sections, for example, in which case the X-shaped joining section might be advantageously used in the middle layer of the sections.

[0026] In some examples, the joining section comprises: a hollow core having a substantially circular shaped cross-section; and two radially protruding portions. In this example, the two radially protruding portions may be arranged around the core with any non-zero angle between them. For example, with an angle of around 120 degrees between them, or with an angle of around 180 degrees between them. Such an arrangement is advantageous when the joining section is arranged as part of a complex, honeycomb-like structure.

[0027] In some examples, the modular sections further comprise: at least two bridging sections; a further longitudinal section; a first further sensor housing section; and a second further sensor housing section. The first further sensor housing section may be releasably coupled to one end of the further longitudinal section. The second further sensor housing section may be releasably coupled to the other end of the further longitudinal section. Each of the first and second further sensor housing sections may be arranged to house a sensor for detecting the subsea object. Each of the at least two bridging sections may be releasably coupled to, and extend between, a respective one of the first and second sensor housing sections and a respective one of the first and second further sensor housing sections such that the longitudinal section is arranged substantially parallel to the further longitudinal section.

[0028] Advantageously, the provision of such bridging sections, further longitudinal sections, and further sensor housing sections means that - when needed - the apparatus can be extended to feature an additional tier (that is, level). Accordingly, in use, and when necessary due to the specific real world conditions at hand, there may be an additional tier of sensors provided. That is, there may be two tiers of sensors, if needed. The apparatus is thus easily adaptable for different real world scenarios. The ability to adapt the apparatus in this way leads to improved accuracy and / or reliability of the detection results, leading to improved sensor detection, and makes the apparatus versatile and suitable for a range of different projects.

[0029] Further advantageously, the bridging sections provide improved rigidity to the apparatus which is important for the strength and durability of the apparatus, and also for the accuracy of the sensor results and object detection.

[0030] In some examples, one or more of the bridging sections is configured to releasably couple to a tow arm. Such bridging sections may be elsewhere referred to as bridging connections.

[0031] In some examples, the modular sections are configured such that the bridging sections are oriented substantially perpendicular to the longitudinal section and the further longitudinal section. As a result, the at least two bridging sections, the longitudinal section and the further longitudinal section may generally form a rectangle shape. The bridging sections may be orientated - i.e., extend -substantially perpendicular to the axis of travel. The plane in which the bridging sections extend may be perpendicular to the plane in which the axis of travel extends. For example, such that the plane extending between the longitudinal section and the further longitudinal section is oriented substantially vertically. Accordingly, the tiers of the apparatus may be arranged to stack vertically.

[0032] Advantageously, vertical arrangement of the tiers allows for straightforward assembly. As such, quicker assembly and disassembly of the apparatus can be achieved. This reduces operational downtime for maintenance and repair.

[0033] In some examples, the modular sections are configured such that the bridging sections are oriented - i.e., extend - at a non-perpendicular angle to the longitudinal section and the further longitudinal section.

[0034] In some examples, the modular sections are configured such that the tiers of the apparatus are arranged to stack at an angle to the vertical. For example, the modular sections may be configured such that the plane extending between the longitudinal section and the further longitudinal section is oriented at a non-zero angle to the vertical (such as at an angle of between 0 and 90 degrees, such as 45 degrees). Put another way, the modular sections may be configured such that the angle formed between the plane in which the axis of travel extends and the plane extending between the longitudinal section and the further longitudinal section is non-perpendicular, such as 45 degrees. The modular sections may be configured such that the tiers of the apparatus tilt generally away from the direction of travel of the apparatus.

[0035] Advantageously, the arrangement of tiers such that they are offset from each other in the tow direction - for example, offset such that the tiers tilt away from the tow direction - may prevent lower tiers from blocking the path of view to the seabed of sensors positioned in a higher tier. For example, an altimeter sensor requires an undisturbed path of view to acoustically measure the distance to the seabed.

[0036] In some examples, the modular sections are configured such that the bridging sections form a triangular truss-like pattern between the longitudinal section and the further longitudinal section. For example, the bridging sections may be offset from the vertical in the lateral direction. For example, the bridging sections may extend between the longitudinal section and the further longitudinal section at an angle of between 0 and 90 degrees (perpendicular): for example, at an angle of 45 degrees. As such, the bridging sections form a triangular truss-like pattern. In some examples, the plane extending between the longitudinal section and the further longitudinal section is orientated substantially vertically; in other examples, the plane may form a non-zero angle to the vertical, as described above in relation to non-vertically stacked tiers of the apparatus.

[0037] Advantageously, the arrangement of the bridging sections such that they are oriented at an angle to the vertical axis in the lateral direction, such as to form a triangular truss like arrangement, results in a stronger structure. As a result, the structure is more resistant to damage in use. Further, because of the inherent strength advantage, smaller, thinner and / or lighter parts may be used, which reduces material usage and improves safety. Further, the arrangement of the bridging sections such that they are oriented at an angle to the vertical axis and with a lateral offset can result in a stiffer structure. This allows the modular sections - and thus the sensors - to more accurately remain in position during use.

[0038] In some examples, the span of the bridging sections is less than the length of the longitudinal section and the further longitudinal section. In other words, the bridging sections are shorter than the longitudinal section and the further longitudinal section.

[0039] In some examples, the further longitudinal section and / or the bridging sections have a substantially airfoil-shaped cross-section. The cross-section shape be that of the NACA 0010 airfoil, as previously described in relation to the longitudinal section.

[0040] In some examples, when the longitudinal section and / or the further longitudinal section has a substantially airfoil-shaped cross-section, the longitudinal section and / or the further longitudinal section is configured such that, in use, the angle of attack on the section(s) is zero. Alternatively, the angle of attack may be negative (and non-zero).

[0041] Advantageously, a negative angle of attack results in the production of a downward lift force. This helps encourage the apparatus to travel down towards the sea floor when being towed in the water. In other words, this helps achieve a lower altitude of the apparatus relative to the seabed. By exploiting the force creating properties of the airfoil-shape, an energy saving is achieved.

[0042] In some examples, at least one of the further sensor housing sections comprises a nose section and a joining section. The nose section and / or the joining section may be substantially as previously described in relation to the sensor housing sections.

[0043] In some examples, one or more of the sensor housing sections and / or one or more of the further sensor housing sections comprises an aperture for the flow of water into the respective sensor housing section.

[0044] Advantageously, the aperture(s) enable water to quickly flood into the apparatus during launch of the apparatus into the water, and - similarly - to quickly drain out from the apparatus when the apparatus is being recovered from the water. Further, the aperture(s) advantageously serves as an opening in the apparatus that could be utilised in conjunction with a sensor coupled to the apparatus, such as an altimeter sensor, which requires an undisturbed path of view to operate. For example, an altimeter sensor requires an undisturbed path of view to acoustically measure the distance to the seabed. Such a sensor could be positioned in the apparatus in such a location that an undisturbed path via the aperture is provided.

[0045] In some examples, the apparatus has an axis of travel. The axis of travel of the apparatus may be substantially perpendicular to the longitudinal axis of the at least one longitudinal section. The axis of travel and the longitudinal axis of the at least one longitudinal section may extend in substantially parallel planes to each other. The apparatus may have a lateral axis. The lateral axis of the apparatus may be substantially perpendicular to the axis of travel of the apparatus. The lateral axis of the apparatus may be substantially parallel to the longitudinal axis of the at least one longitudinal section.

[0046] In some examples, the apparatus comprises at least a first and second tow arm, the first and second tow arms being releasably coupled to the apparatus at opposite sides of the apparatus to each other. In other words, the first and second tow arms may be releasably coupled to the apparatus at laterally opposite sides of the apparatus to each other.

[0047] Advantageously, the coupling of the tow arms either side of the apparatus enables greater control of the apparatus (compared, say, to having one or more tow arms coupled only towards the middle of the apparatus), and thus delivers a more stable arrangement. In turn, this results in more reliable scan results.

[0048] In some examples, the modular sections comprise at least two end sections. The end sections may be arranged at opposite sides of the apparatus to each other. In other words, the end sections may be arranged at laterally opposite sides of the apparatus to each other. Each of the first and second tow arms may be releasably coupled to a respective one of the end sections.

[0049] Advantageously, such end sections provide a convenient way for the tow arms to be swiftly attached or detached from apparatus.

[0050] In some examples, the apparatus may comprise at least one inner tow arm. The inner tow arm may be generally arranged between the first and second tow arms. The at least one inner tow arm may be releasably coupled to one or more of the bridging sections.

[0051] In some examples, the first, second and / or inner tow arms are configured to provide a tow force to the apparatus for towing the apparatus through the water.

[0052] In some examples, at least a portion of each of the first and second tow arms extends laterally beyond a respective one of the outermost sensor housing sections. That is, each of the first and second tow arms extends beyond a respective one of the outermost sensor housing sections in a lateral direction. This may be such that the modular sections, the first and second tow arms, and the vehicle together generally define a perimeter within which the sensor housing sections are contained. Alternatively or additionally, the configuration of the first and second tow arms may be such that the first and second tow arms are configured to deflect debris away from the apparatus. For example, away from the sensor housing sections.

[0053] Advantageously, in this way, the first and second tow arms protect the apparatus - and, in particular, the sensor housing sections and thus the sensors - from impact with floating debris. Floating debris may include fishing equipment, containers, or other items at sea, which can cause significant damage to the apparatus or the sensors.

[0054] In some examples, the vehicle is a remotely operated towed vehicle (ROTV). The ROTV may be towed by a vessel. The vessel may be an uncrewed surface vessel (USV).

[0055] Advantageously, ROTVs can climb and descend quickly, enabling the apparatus to maintain a constant altitude above the seabed. This improves the accuracy of the sensor and thus objection detection results.

[0056] In some examples, one or more of the modular sections is formed from a composite material.

[0057] Advantageously, the use of a composite material reduces the weight of the structure compared to conventional approaches. This increases safety for personnel handling the apparatus, as previously discussed. Further advantageously, composite materials have a favourable weight-strength relationship, resulting still in a durable apparatus able to withstand harsh marine environments.

[0058] Also disclosed is a method of manufacturing the above described apparatus. The method may comprise forming one or more of the modular sections using a moulding process.

[0059] In some examples, the moulding process comprises: layering up composite material in a mould; treating the composite material to form a composite modular section; and removing the composite modular section from the mould.

[0060] Advantageously, the described manufacturing method allows, for any given section, for local reinforcement of highly loaded areas by adding more layers of composite material in these areas.This ability to reinforce specific areas results in a robust apparatus without excessive use of materials and whilst keeping the weight of the apparatus at a minimum.

[0061] Also disclosed is a kit of parts for use with one or more sensors to detect a subsea object. The kit comprises a plurality of modular sections configured to be assembled to form a structure. The modular sections comprise: a first sensor housing section; a second sensor housing section; and at least one longitudinal section. The first sensor housing section is configured to be releasably coupled to one end of the longitudinal section. The second sensor housing section is configured to be releasably coupled to the other end of the longitudinal section. Each of the first and second sensor housing sections is arranged to house a sensor for detecting the subsea object. The structure may be configured to be towed in water by a vehicle.

[0062] Optional features described in relation to the apparatus may be optional features to the kit of parts.

[0063] Also disclosed is a method of manufacturing the above described kit of parts. The method may comprise forming one or more of the modular sections using a moulding process.

[0064] Optional features described in relation to the method of manufacturing the apparatus may be optional features to the method of manufacturing the kit of parts.

[0065] The term “vehicle” as used herein may refer to any type of vehicle, including marine vehicles and airborne vehicles. Examples of marine vehicles include surface vessels (such as ships), submarines, autonomous marine vehicle, and remotely operated towed vehicles. Examples of airborne vehicles include piloted aircraft, remotely operated aircraft, and autonomous aircraft. The term “vehicle” may also refer to other types of vehicle, as will occur to the person skilled in the art.

[0066] The term “apparatus” as used herein may refer to either a single apparatus or plural apparatus and should not be understood as being particularly limited to either a single discrete apparatus or a plurality of discrete apparatus unless a particular apparatus is further described as such.

[0067] The above mentioned and other features and advantages of the disclosure will be best understood from the following description referring to the attached drawings. In the drawings, like reference numerals denote identical parts or parts performing an identical or comparable function or operation.BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the disclosure and are therefore not to be considered to be limiting of its scope, the principles herein aredescribed and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0069] FIG. 1 is a three-dimensional view of an implementation of the disclosure showing the apparatus coupled to a remotely operated towed vehicle;

[0070] FIG. 2 is a three-dimensional view of an implementation of the disclosure showing the structure of the apparatus;

[0071] FIG. 3 is an exploded view of an implementation of the disclosure showing a subset of the modular sections of the structure;

[0072] FIG. 4 is an exploded view of an implementation of the disclosure showing a different subset of the modular sections of the structure;

[0073] FIG. 5 is a three-dimensional view of an implementation of the disclosure showing an internal section of two sensor housing sections and a bridging section;

[0074] FIG. 6 is a three-dimensional view of an implementation of the disclosure showing a bridging connection; and

[0075] FIG. 7 is a flowchart of a method for manufacturing the apparatus.DETAILED DESCRIPTION

[0076] Examples contemplated by the present disclosure will now be described in more detail with reference to the accompanying drawings. The disclosed subject matter should not be construed as limited to only the embodiments set forth herein. Rather, the illustrated embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0077] Referring to FIG. 1, a three-dimensional view of an implementation of the disclosure is shown. In the shown implementation, the apparatus 1 is shown coupled to a vehicle 5. In this implementation, the vehicle 5 is a remotely operated towed vehicle (ROTV). In use, the apparatus 1 is towed through water by the vehicle 5.

[0078] The apparatus 1 comprises a structure 2. The structure 2 is formed from modular sections. That is, sections which can be releasably coupled to each other such that the structure 2 can be easily assembled and disassembled. In the shown implementation, the modular sections are made of glass fibre reinforced composite. The modular sections are hollow. When assembled, the modular sections form the structure 2. The structure 2 is a wing -like structure. The structure 2 has two tiers: a first tier and a second tier. The first and second tier are arranged to stack vertically.

[0079] In FIG. 1, each of the first tier and the second tier has five sensor housing sections 20 and four longitudinal sections 30. The modular sections are arranged such that the sensor housing sections 20 are positioned along the lateral span of the structure 2 and the longitudinal sections 30 are generally positioned between the sensor housing sections 20. Each sensor housing section 20 is releasably coupled to at least one longitudinal section 30. Each longitudinal section 30 is releasably coupled to two sensorhousing sections 20: one at each end. For example, if each longitudinal section 30 is taken to have a first end and a second end, the first end of each longitudinal section 30 is releasably coupled to a sensor housing section 20, and the second end of each longitudinal section 30 is releasably coupled to another (different) sensor housing section 20. In this way, each longitudinal section 30 is bookended between two sensor housing sections 20. The releasable coupling means (or mechanisms) used between modular sections are described in more detail in reference to FIG. 3.

[0080] The structure 2 - and indeed apparatus 1 overall - has an axis of travel and a lateral axis. The axis of travel and the lateral axis are substantially perpendicular to each other. The axis of travel and the lateral axis generally extend in the same plane as each other. The lateral axis is substantially parallel to the span of the structure 2. It follows that the axis of travel is substantially perpendicular to the span of the structure 2. In use, the structure 2 is towed through water by the vehicle 5 in an orthogonal direction to the span of the structure 2. That is, the structure 2 is towed in a direction generally aligned with the axis of travel.

[0081] The first and second tiers of the structure 2 are connected by bridging sections 60. In this implementation, the number of bridging sections 60 corresponds to the number of sensor housing sections 20 on each tier. Thus, in the shown example, the structure 2 has five bridging sections 60. In the shown example, two of the bridging sections 60 are bridging connections 65. In the present disclosure, the term bridging connection 65 is used to refer to a bridging section 60 which is configured to releasably couple to a tow arm. In other examples, a different number of bridging sections 60 may be a bridging connection 65. The bridging sections 60 and the bridging connections 65 are described in further detail in reference to FIG. 3 and FIG. 6.

[0082] Although in the arrangement shown and described in relation to FIG. 1 there are five sensor housing sections 20 and four longitudinal sections 30, due to the modularity of the sections, the structure 2 may be configured to have any appropriate number of sensor housing sections 20 and longitudinal sections 30. As such, the lateral width of the structure 2 (and thus apparatus 1) may be increased as needed.

[0083] In another example implementation, the structure 2 has two sensor housing sections 20 and one longitudinal section 30. Meanwhile, in another example implementation, the structure 2 has six sensor housing sections 20 and five longitudinal sections 30. The trailing edge of the structure 2 has a flat nylon strip or strips (not shown) attached to it. These strips can extend partially or substantially along the lateral width of the trailing edge. In use, the nylon strip(s) protect the fragile and exposed trailing edge of the structure 2 during launch and recovery. In one example, the nylon strips are attached to the trailing edge with bolted connections. In this way, they can be easily replaced when damaged. Other attachment approaches may also be used as will occur to the person skilled in the art.

[0084] Returning to the structure 2 of the apparatus 1 shown in FIG. 1, each sensor housing section 20 is configured to releasably house a sensor (not shown), the sensor being a sensor suitable fordetecting (alone, or in combination with other sensors) a subsea object. That is, each sensor housing section 20 is configured such that a sensor can be enclosed by, and releasably held within, it. Each sensor housing section 20 has a nose section 22 and a joining section 23, as described in more detail in reference to FIG. 4 and FIG. 5.

[0085] In the shown implementation, the apparatus 1 includes sensors which are suitable for ferromagnetic material detection. As a result, the apparatus 1 is suitable for the detection of unexploded items of ordinance (UXOs). Specifically, the apparatus 1 includes magnetometers. Each magnetometer is housed in a sensor housing section 20. In other implementations, the sensor(s) can additionally include one or more acoustic sensors. The use of acoustic sensors in conjunction with magnetometers allows for better quality of survey data.

[0086] In other implementations, the apparatus 1 may include any combination of sensors suitable for detection of the subsea object or objects of interest. Accordingly, each sensor housing section 20 may be arranged to house (and, in use, house) a suitable sensor type. In some examples, each sensor housing section 20 houses the same type of sensor. In other examples, one or more of the sensor housing sections 20 houses a different type of sensor to one or more others of the sensor housing sections 20. In some examples, one or more of the sensor housing sections does not house a sensor. That is, it is empty. This advantageously allows the apparatus 1 to be customised for a specific detection requirement.

[0087] Turning again to the implementation shown in FIG 1, the structure 2 has four end sections 70. Each tier of the structure 2 has two - that is, a pair - of the four end sections 70. The end sections 70 in each pair are arranged at laterally opposite ends of the apparatus 1 to each other. That is, the end sections 70 are arranged such that they are located at the outermost lateral positions of the apparatus 1. Each end section 70 is releasably connected to a sensor housing section 20.

[0088] In the implementation shown in FIG. 1, the apparatus 1 also has four tow arms: two first tow arms 41, and two second tow arms 42. In this example, the tow arms 41, 42 are identical, but in other examples there may be differences. The first and second tow arms 41, 42 are, in this implementation, formed from aluminium tubes. In an implementation, the first and second tow arms 41, 42 may be formed from a composite material. The first and second tow arms 41, 42 connect the structure 2 to the ROTV 5 such that, in use, the structure 2 can be towed through the water by the ROTV 5. The first tow arms 41 are arranged and couple with one lateral side of the structure 2, while the second tow arms 42 are arranged and couple with the other lateral side of the structure 2. There is one first tow arm 41 and one second tow arm 42 per tier of the structure 2. In more detail: one end of each first tow arm 41 is releasably coupled to a respective end section 70. Meanwhile, the other end of each first tow arm 41 is releasably coupled to the ROTV 5. Similarly, one end of each second tow arm 42 is releasably coupled to a respective end section 70 on the laterally opposite side of the structure 2 to the first tow arms 41. Meanwhile, the other end of each second tow arm 42 is releasably coupled to the ROTV 5. In the shown implementation, the first 41 and second 42 tow arms have substantially the samecross-sectional shape and each end section 70 has an opening which corresponds to the shape of that cross-sectional shape. Due to the outermost lateral positioning of the end sections 70, the first and second tow arms 41, 42 are arranged such that they are positioned laterally outside of the outermost sensor housing sections 20.

[0089] In the shown implementation, the first 41 and second 42 tow arms each have a first straight section 45 and a second straight section 47, with a bend 46 located between them. That is, with a bend 46 between the first 45 and second 47 straight sections. The arrangement is such that the second straight section 47 is orientated at a non-zero angle with respect to the first straight section 45. That is, at an angle between 0 and 90 degrees (perpendicular) to the first straight section 45. In the implementation shown in FIG. 1, the angle of the bend is around 135 degrees. In other examples, the angle of the bend may be different.

[0090] In the shown implementation, the structure 2 has two inner tow arms 43. The inner tow arms are formed in this example from aluminium tubes. In an implementation, the inner tow arms may be formed from composite tubes. The inner tow arms 43 are generally arranged laterally between the first and second tow arms 41, 42. The inner tow arms 65 are configured to connect the structure 2 to the ROTV 5. One end of each inner tow arm 43 is releasably coupled to a bridging connection 65. The other end of each inner tow arm 43 is releasably coupled to the ROTV 5. In the shown implementation, the inner tow arms 43 are shorter than the first and second tow arms 41 , 42.

[0091] The structure 2 and apparatus 1 overall is generally symmetrical about its axis of travel.

[0092] The first 41, second 42 and inner 43 tow arms are connected to the ROTV 5 by means of clamps and nylon bearings. As such, a swivelling (pitch) motion of the first 41, second 42 and inner 43 tow arms around the ROTV 5 is possible.

[0093] In operation, the modular sections are assembled to form the structure 2 of apparatus 1. In the shown implementation, the modular sections slide together to form overlap sections. The modular sections are then attached together, at the overlap sections, using brass bolts. Other types of material may further be used, such as steel, titanium, magnesium, or the like. In an advantageous implementation the materials are able to withstand salt-water corrosion. In an implementation, the modular sections may be attached together using a latched connection. The latched connection may be provided by latching a locking arm on a first modular section over a receiving section on another modular section. The locking arm them provides a pulling force using a mechanical lever system to lock the locking arm in the receiving section to join the two modular sections together. As already discussed, in the shown implementation, sensors - specifically here, magnetometers - are inserted into and housed in the sensor housing sections 20. Each sensor is housed either in the nose section 22 or the joining section 23 of its respective sensor housing section 20. The sensors are for example held in position by rubber lined clamps. The rubber protects the sensors from damage. Each sensor typically has a sensor cableconnected to it which connects the sensor to adjacent sensors. The sensor cables can be easily internally routed through the modular sections of the structure 2.

[0094] Once a sensor is in position in its sensor housing section 20, either in the nose section 22 or the joining section 23 of the sensor housing section 20, the nose section 22 and the joining section 23 are attached together using brass bolts. As such, the sensor is enclosed by the sensor housing structure 20.

[0095] Still considering the operation of the apparatus 1, in operation, the structure 2 is connected to the vehicle 5 by first 41 and second 42 tow arms and by the inner town arms 43, as previously described. More specifically, the tow arms 41, 42, 43 are attached to the structure 2 using bolts, and to the ROTV 5 using clamps and nylon bearings.

[0096] The structure 2, and indeed apparatus 1, is generally assembled out of the water. In some examples, the structure 2 (and apparatus 1) is assembled on a boat. In an example, the apparatus 1 is deployed from the boat into the water by means of an A-frame with a sheave in combination with a deck winch. The apparatus 1 is brought over the stem in the lateral direction. The A-frame is then brought in her outermost position and the apparatus 1 is rotated around 90 degrees in a counterclockwise direction, such that the span of the structure 2 and apparatus 1 is positioned alongside the edge of the boat. The apparatus 1 is then lowered into the water.

[0097] The structure 2 is towed through the water by the ROTV 5. The ROTV 5 controls the altitude of the structure 2 above the seabed. The ROTV 5 has small steerable fins which enable the ROTV 5 to climb or descend quickly to maintain a constant altitude above the seabed. When the structure 2 is towed through the water, the magnetometers it houses and carries detect variations in both vertical and transverse magnetic gradients, allowing the location of UXO to be identified.

[0098] After operation, the apparatus 1 is retrieved from the water by means of the A-frame with a sheave in combination with a deck winch. As the apparatus 1 is raised from the water it is orientated such that that the span of the apparatus 1 (and structure 2) is positioned alongside the edge of the boat. Once raised to a height above the deck, the apparatus 1 is rotated around 90 degrees in a clockwise direction. The apparatus is then brought over the stem and lowered onto the deck. The modular sections of the stmcture 2 can be easily disassembled by untightening the brass bolts. During maintenance, damaged modular sections can be quickly replaced. Sensors can be easily removed and installed by untightening the brass bolts and removing the respective nose section 22 to easily gain access to the sensor. This is the case whether the sensor is in the nose section 22 or the joining section 23.

[0099] Referring to FIG. 2, a three-dimensional view of an implementation of the disclosure showing the stmcture 2 of the apparatus 1 is shown. FIG. 2 shows the modular sections of the stmcture 2.

[0100] In the implementation shown in FIG. 2, the stmcture 2 has two tiers, as in the implementation shown in FIG. 1. These may be referred to as the first and second tiers. Each of the firstand second tiers has five sensor housing sections 20, and four longitudinal sections 30. The first and second tiers are connected by bridging sections 60. There are five bridging sections 60. Each of the bridging sections 60 is releasably coupled to, and extends between, a sensor housing section 20 of the first tier and a sensor housing section 20 of the second tier. This arrangement is such that the longitudinal sections 30 of the tiers are arranged substantially parallel to each other.

[0101] The longitudinal sections 30 of the first tier may be referred to in this disclosure as the longitudinal sections 30, while the longitudinal sections 30 of the second tier may be referred to as further longitudinal sections 30. Similarly, the sensor housing sections 20 of the first tier may be referred to as the sensor housing sections 20, while the sensor housing sections 20 of the second tier may be referred to as further sensor housing sections 20.

[0102] In the shown implementation, the bridging sections 60 are oriented substantially perpendicular to the longitudinal sections 30 and the further longitudinal sections 30 such that the plane extending between the longitudinal sections 30 and the further longitudinal sections 30 is oriented substantially vertically. That is, the two tiers are vertically stacked, one on top of the other.

[0103] In other examples, the bridging sections 60 may be oriented at a non-perpendicular angle to the longitudinal sections 30 and the further longitudinal sections 30. That is, at an angle between 0 and 90 degrees (perpendicular) to the longitudinal sections 30 and the further longitudinal sections 30 such that the plane extending between the longitudinal sections 30 and the further longitudinal sections 30 is oriented at a non-zero angle to the vertical. That is, such that the two tiers are arranged at a nonzero angle with respect to each other. For example, an angle of between 0 and 90 degrees.

[0104] In the shown implementation, the bridging sections 60 are shorter than the longitudinal sections 30 (or further longitudinal sections 30). In other examples, the bridging sections 60 may be longer than the longitudinal sections 30 (or further longitudinal sections 30).

[0105] In other implementations, the structure 2 may have a different number of tiers. For example, the structure 2 may have at least one further tier. It may therefore have three tiers. The modular sections of the structure 2 are configured such that any appropriate number of tiers may be constructed. In one example, the structure 2 has four tiers. An additional tier may be added by incorporating additional, and in some case different, modular sections to the structure 2. This is discussed in more detail below.

[0106] In the shown implementation, some of the bridging sections 60 are bridging connections 65. Specifically, two of the bridging sections 60 are bridging connections 65. Each bridging connection 65 is configured to releasably couple to an inner tow arm 43, as described in reference to FIG. 1. The bridging connections will be described in more detail with reference to FIG. 6.

[0107] As an example, the structure 2 may have a total width - that is, span - of between 5,000mm and 7,000mm.

[0108] Finally, FIG. 2 shows that, in this implementation, each of the nose sections 22 has an aperture 90. The apertures 90 are discussed in more detail below with reference to FIG. 4.

[0109] Referring now to FIG. 3, an exploded view of an implementation of the disclosure showing a subset of the modular sections of the structure 2 is shown. Specifically, a subset of the modular sections of one tier of the structure 2 is shown. Features described in relation to the subset of modular sections shown in FIG. 3 are not restricted to the specific subset shown in FIG. 3. Instead, features described in relation to a particular modular section may apply to all or some modular sections of that same kind.

[0110] The modular sections shown in FIG. 3 are two sensor housing sections 20, a longitudinal section 30 arranged therebetween, a bridging section 60 coupled to one of the sensor housing sections 20, and a bridging connector 65 coupled to the other of the sensor housing sections 20.[OHl] In the shown implementation, the longitudinal section 30 has a substantially airfoil-shaped cross-section. Specifically, the longitudinal section 30 has the cross-sectional shape of the NACA 0010 airfoil. Accordingly, the substantially airfoil-shaped cross-section is: substantially symmetrical about the airfoil chord; has a maximum thickness of around 10% of the chord length; and has no camber (that is, have a camber line coincident with the chord).

[0112] In some examples, the longitudinal sections 30 may have a span of between 1,000mm and 1,500mm.

[0113] In the implementation shown in FIG. 3, two sensor housing sections 20 are shown. The sensor housing sections 20 each have three protruding portions 50, two of which are visible in FIG. 3. The third protruding portions 50 which are not visible are not visible because they are inserted into the bridging section 60 or bridging connector 65.

[0114] In other implementations, the sensor housing sections 20 may have a different number of protruding portions 50. For example, there may be two protruding portions 50 (for example, for a sensor housing section 20 for a single tier structure 2), or four protruding portions 50 (for example, for a sensor housing section 20 for a middle tier of a three or more tier structure 2).

[0115] Each sensor housing section 20 has a hollow core having a substantially circular shaped cross-section. Each protruding portion 50 protrudes in the radial direction (relative to the circular shaped cross-section of the hollow core). More specifically, each protruding portion 50 protrudes from the joining section of each sensor housing section 20. In the shown implementation, each protruding portion 50 extends along around half the axial length of the sensor housing section 20. This is around the full axial length of the joining section. The protruding portions 50 have a cross-section which substantially matches that of the longitudinal section 30, the bridging section 60, the bridging connector 65, and the end sections. In the shown implementation, the protruding portions 50 are hollow.

[0116] In the shown example, the protruding portions 50, the longitudinal section 30, the bridging section 60 and the bridging connector 65 each have substantially matching cross-sections, the crosssections having an airfoil shape. Accordingly, the sections have an approximately similar chord length and thickness. In some implementations, the chord length and thickness of the protruding portions 50may be marginally (that is, slightly) smaller than the chord length and thickness of the other sections. Advantageously, this allows the protruding portions 50 to slide into the longitudinal section 30, the bridging section 60 and the bridging connector 65.

[0117] In the shown example, one of the protruding portions 50 of each sensor housing section 20 is configured to be releasably received by the longitudinal section 30 arranged therebetween. The longitudinal section 30 has openings at its longitudinal ends such that the protruding portions 50 can slide inside the longitudinal section 30 to create, at each end, an overlap between the respective protruding portion 50 and the longitudinal section 30. The opening in the longitudinal section 30 is configured to have a tight tolerance with the protrusions 50.

[0118] As described, in the shown implementation, the protruding portions 50 have a substantially airfoil-shaped cross-section such that the cross-section of the protruding portions 50 corresponds to the internal cross-section of the longitudinal section 30.

[0119] In use, each of the sensor housing sections 20 is attached to the longitudinal section 30 at the overlap formed between them using bolts.

[0120] In the shown implementation, one of the protruding portions (not visible) of the first sensor housing section 20 is releasably received by a bridging section 60. The bridging section 60 has an opening at each of its ends, each opening corresponding to the cross-sectional shape of the protruding portion 50. As such, the protruding portion 50 can slide inside the bridging section 60 to create an overlap between the protruding portion 50 and the bridging section 60.

[0121] In use, the sensor housing section 20 and the bridging section 60 are attached at the overlap formed between them using bolts.

[0122] In the shown implementation, one of the protruding portions (not visible) of the second sensor housing section 20 is releasably received by a bridging connection 65. The bridging connection 65 has an opening at each of its ends, each opening corresponding to the cross-sectional shape of the protruding portion 50. As such, the protruding portion 50 can slide inside the bridging connection 65 to create an overlap between the protruding portion 50 and the bridging connection 65.

[0123] In use, the sensor housing section 20 and the bridging connection 65 are attached at the overlap formed between them using bolts.

[0124] In other implementations, the protruding portions 50 may not have a cross-section which substantially matches that of the longitudinal section 30. Instead, each protruding portion may, for example, comprise two or more fingers. In such implementations, the fingers are configured to be inserted into the longitudinal section 30 substantially as described in relation to the protruding portions 50. As for the protruding portions 50, there is a tolerance fit with the longitudinal section 30. Further, the fingers create the previously described overlap, at which bolts or other releasable coupling means may be used to attach the two sections together.

[0125] In other implementations, the sensor housing sections 20 - and specifically, the joining sections 23 - may be configured to releasably couple with one or more of the longitudinal sections 30, the bridging sections 60 and the end sections 70 via one or more snap-fit connections. Snap-fit connections are an example of releasable coupling means.

[0126] In other implementations, the sensor housing sections 20 - and specifically, the joining sections 23 - may be configured to releasably couple with one or more of the longitudinal sections 30, the bridging sections 60 and the end sections 70 via one or more clips. Clips are an example of releasable coupling means.

[0127] In other implementations, the sensor housing sections 20 - and specifically, the joining sections 23 - may be configured to releasably couple with one or more of the longitudinal sections 30, the bridging sections 60 and the end sections 70 via one or more latches. Latches are an example of releasable coupling means.

[0128] Referring now to FIG. 4, an exploded view of an implementation of the disclosure showing a different subset of the modular sections of the structure 2 is shown. As noted in respect of FIG. 3, features described in relation to the subset of modular sections shown in FIG. 4 are not restricted to the specific subset shown in FIG. 4. Instead, features described in relation to a particular modular section may apply to all or some modular sections of that same kind.

[0129] FIG. 4 shows modular sections from two tiers of the structure 2. Specifically, FIG. 4 shows a bridging section 60, two end sections 70, and two sensor housing sections 20.

[0130] In the shown implementation, the bridging section 60 has a substantially airfoil-shaped cross-section. In some examples, the bridging section 60 may have the same substantially airfoil-shaped cross-section as the longitudinal section 30. In some examples, the bridging sections 60 may have a span of between 100mm and 300mm.

[0131] In the shown implementation, as previously described, the sensor housing sections 20 each have a nose section 22 and a joining section 23. The nose section 22 and the joining section 23 are configured for releasable coupling with each other. In the shown implementation, corresponding holes are provided in the nose section 22 and the joining section 23 which are suitable for receiving brass bolts therethrough. In this way, the nose section 22 and the joining section 23 may be releasably coupled.

[0132] In other implementations, the nose section 22 and the joining section 23 may be screwed together; coupled by means of a snap-fit connection; coupled using clamps; or otherwise coupled using releasable coupling means.

[0133] In the shown implementation, the joining section 23 is substantially T-shaped. That is, and as has been previously described, the joining section 23 has a hollow core having a substantially circular shaped cross-section, and three radially protruding portions 50. Two of the radially protruding portions 50 are arranged substantially opposite each other, and the other of the radially protruding portions 50 isarranged substantially equidistant between the two opposing radially protruding portions 50. In the shown example, the radially protruding portion 50 which is arranged substantially equidistant between the two opposing radially protruding portions is configured to releasably couple to the bridging section 60. One of the opposing radially protruding portions is configured to releasably couple to an end section 70. The other of the two opposing radially protruding portions 50 is configured to releasably couple to a longitudinal section 30 (not shown in FIG. 4).

[0134] In another implementation, for example if the sensor housing section 20 is at a different position in the structure 2, both of the two opposing radially protruding portions may be configured to releasably couple to a longitudinal section 30.

[0135] In another implementation, any of the radially protruding portions 50 may be configured to releasably couple to any of the modular sections. That is, each of the radially protruding portions 50 may be configured to releasably couple to: a bridging section 60; a longitudinal section 30; a bridging connection 65; or an end section 70, such that the structure 2 may be arranged as desired.

[0136] In another implementation, the joining section is substantially X-shaped. For example, the joining section has a hollow core having a substantially circular shaped cross-section, and four radially protruding portions arranged substantially equally around the core. In this implementation, The four radially protruding portions may be configured to releasably couple to any of the modular sections. That is, each of the four radially protruding portions 50 may be configured to releasably couple to: a bridging section 60; a longitudinal section 30; a bridging connection 65; or an end section 70, such that the structure 2 may be arranged as desired.

[0137] In another implementation, rather than having three radially protruding portions, the joining section has two radially protruding portions. The two radially protruding portions are arranged around the core with any non-zero angle between them. For example, with an angle of around 120 degrees between them, or with an angle of around 180 degrees between them. The radially protruding portions may be configured to releasably couple to any of the modular sections. That is, each of the radially protruding portions may be configured to releasably couple to: a bridging section 60; a longitudinal section 30; a bridging connection 65; or an end section 70, such that the apparatus 1 may be arranged as desired.

[0138] Returning to the shown implementation, in the shown implementation, the nose section 22 of the sensor housing section 20 is a rounded-cone shape. This streamlined shape allows the water to flow smoothly around the nose section 22.

[0139] In the shown implementation, the apparatus 1 has a cable router 80 configured to internally arrange the sensor cables within the apparatus 1. The cable router 80 is an annular component with a plurality of radially spaced holes. The holes are configured such that sensor cables can be fed through them and thus arranged. In the shown implementation, the cable router 80 is located in the nose section22 of the sensor housing section 20. The cable router 80 is positioned centrally with respect to the hollow nose section 22.

[0140] In another implementation, the cable router 80 is located in the joining section 23 of the sensor housing section 20. In another implementation, one or more cable routers 80 may be additionally or alternatively located within other hollow modular sections of the structure 2. For example, a cable router 80 may additionally be located within one or more longitudinal sections 30, bridging sections 60, and / or bridging connections 65.

[0141] Referring to FIG. 5, a three-dimensional view of an implementation of the disclosure showing an internal section of two sensor housing sections 20 and a bridging section 60 is shown. The two sensor housing sections 20 each have a nose section 22 and a joining section 23, as previously described. In the shown implementation, the joining section 23 is configured to releasably receive and / or hold the sensor. The sensor is held in position by rubber lined clamps in the joining section 23. The nose section 22 is configured to releasably couple to the joining section 23 such that, when coupled, the sensor is enclosed by the nose section 22 and the joining section 23. As a result, in use, the sensor is housed within the sensor housing section 20. However, when access to the sensor is needed or wanted, the nose section 22 may be easily removed and the sensor accessed. In the shown example, the nose section 22 is secured to the joining section 23 by a plurality of bolts (not shown).

[0142] Alternatively, in another implementation, the nose section 22 may be configured to releasably receive and / or hold the sensor. Accordingly, in this implementation, the sensor may be held in position by rubber lined clamps in the nose section 23. The nose section 22, including the held sensor, may be configured to couple to the joining section 23 such that the sensor is enclosed and housed within the sensor housing section 20.

[0143] In other implementations, different means for holding the sensor in position within the nose section 22 or joining section 23 may be used.

[0144] In the shown implementation, the sensor housing sections 20 each have an aperture 90. Each aperture 90 allows water to flow into, and drain out of, the respective sensor housing section 20. The aperture 90 is large enough to allow water to enter whilst maintaining the structural integrity of the sensor housing section 20. For example, the aperture 90 may have a diameter of between 50mm and 100mm. In the shown implementation, the aperture 90 is located in the nose sections 22 of the sensor housing sections 20.

[0145] In other implementations, the aperture 90 may be located in the joining sections 23 of the sensor housing sections 20. In other implementations, some sensor housing sections 20 may have an aperture 90 in their nose section 22, whilst other sensor housing sections 20 may have an aperture 90 in their joining section 23. In still other implementations, the aperture 90 may be located in both the nose section 22 and the joining section 23. That is, it may span the two sections.

[0146] In some implementations, the aperture 90 may be positioned such that an acoustic sensor housed within the sensor housing section 20 has an undisturbed path of view to the seabed (or vice versa - i.e., the acoustic sensor may be positioned such that is has an undisturbed path of view to the seabed via the aperture 90).

[0147] Referring to FIG. 6, a three-dimensional view of an implementation of the disclosure showing a bridging connection 65 is shown. In the shown implementation, the bridging section 60 has a substantially airfoil-shaped cross-section.

[0148] In some examples, the bridging connection 65 may have the same substantially airfoilshaped cross-section as the longitudinal section 30. In other examples, the bridging connection 65 may have a different substantially airfoil-shaped cross-section to the longitudinal section 30.

[0149] In the shown implementation, the bridging connection 65 is configured to releasably couple to, and extend between, a sensor housing section 20 in the first tier of the structure 2, and a sensor housing section 20 in the second tier of the structure 2. In arrangements comprising more than two tiers, the bridging connection 65 may generally extend between two sensor housing sections 20 of adjacent tiers. As such, the bridging connection 65 is configured to releasably receive, at each of its ends, a protruding portion 50 of a sensor housing section 20. That is, the bridging connection 65 has two openings in its longitudinal direction which correspond to the cross-sectional shape of a protruding portion 50.

[0150] As previously described, the bridging connection 65 is further configured to releasably couple to an inner tow arm 43. Accordingly, the bridging connection 65 has a cylindrical opening 67 having a cross-sectional shape which corresponds to the cross-section of the inner tow arm 43. In use, a portion of the inner tow arm 43 is inserted into the cylindrical opening 67 and attached to the bridging connection 65 using bolts.

[0151] The modular sections described with reference to FIG. 1 to FIG. 6 may constitute a kit of parts. The kit has a plurality of modular sections configured to be assembled to form the structure 2. The modular sections include: sensor housing sections 20; longitudinal sections 30; and bridging sections 60. As has been described, each of the sensor housing sections comprises two sections: a nose section 22; and a joining section 23. The modular sections may further include: end sections 70; and bridging connections 65.

[0152] One or more of the modular sections of the structure 2 may be formed from a composite material. In some examples, the composite material may be a glass fibre reinforced composite. In another example, the composite material may be a carbon fibre reinforced composite. In another example, other composite materials exhibiting the desired material properties may be used. Important, and thus desired, material properties include sufficient mechanical stiffness and impact strength. Further, the material must not be too brittle. Sufficient ductility is therefore important. This is to avoidcrack formation and / or failure in the case of impact. Finally, material density is important: the weight in water of the material chosen should preferably be smaller rather than larger.

[0153] Referring to FIG. 7, a flowchart of a method 100 for manufacturing the apparatus 1 is shown. More specifically, the method 100 is a method for manufacturing the structure 2 and, in turn, the modular sections. The method 100 is thus also a method for manufacturing the modular sections for the kit of parts previously described.

[0154] The method 100 involves forming one or more of the modular sections using a moulding process. The method 100 may further include a first step 110, a second step 120, and a third step 130. In the first step 110, composite material is layered up in a mould. In the second step 120, the composite material is treated to form a composite modular section. In the third step 130, the composite modular section is removed from the mould.

[0155] The moulds for manufacturing the modular sections are, in this example, computer numerical control (CNC) machined aluminium moulds. The moulds define the outer shape of the modular sections. A variety of different moulds may be used to produce a variety of different modular sections with differing dimensions and characteristics. As such, the geometry of the sections can be changed if needed, and so the vertical and / or lateral distance between sensors carried by the structure 2 (and apparatus 1) can be adjusted.

[0156] In the first step 110, reinforcement material can be arranged to provide local reinforcement for highly loaded areas of the modular pieces. That is, additional reinforcement material can be added in specific regions.

[0157] The preceding detailed description is merely exemplary in nature and is not intended to limit the disclosure and its uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the detailed description.

[0158] Those skilled in the art will recognise that a wide variety of modifications, alterations, and combinations can be made with respect to the above described examples without departing from the scope of the disclosed concepts, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the disclosed concepts.

[0159] Further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific examples have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

24CLAIMS1. An apparatus for use with one or more sensors to detect a subsea object, the apparatus comprising:a structure configured to be towed in water by a vehicle, the structure comprising modular sections, the modular sections comprising:a first sensor housing section;a second sensor housing section; andat least one longitudinal section, and wherein:the first sensor housing section is releasably coupled to one end of the longitudinal section;the second sensor housing section is releasably coupled to the other end of the longitudinal section; andeach of the first and second sensor housing sections is arranged to house a sensor for detecting the subsea object.

2. The apparatus of any preceding claim, wherein at least one of the sensor housing sections comprises a nose section and a joining section, and one of the joining section or the nose section is arranged to house the sensor.

3. The apparatus of claim 2, wherein the nose section and the joining section are releasably coupled to each other.

4. The apparatus of any preceding claim, wherein the modular sections further comprise:at least two bridging sections;a further longitudinal section;a first further sensor housing section; anda second further sensor housing section, and wherein:the first further sensor housing section is releasably coupled to one end of the further longitudinal section;the second further sensor housing section is releasably coupled to the other end of the further longitudinal section;each of the first and second further sensor housing sections is arranged to house a sensor for detecting the subsea object; andeach of the at least two bridging sections is releasably coupled to, and extends between, a respective one of the sensor housing sections and a respective one of the further sensor housing sections such that the longitudinal section is arranged substantially parallel to the further longitudinal section.

5. The apparatus of claim 4, wherein one or more of the bridging sections is configured to releasably couple to a tow arm.

6. The apparatus of any preceding claim, wherein one or more of the sensor housing sections comprises an aperture for the flow of water into the respective sensor housing section.

7. The apparatus of any preceding claim, wherein:the apparatus has an axis of travel, the axis of travel being substantially perpendicular to a longitudinal axis of the at least one longitudinal section, and wherein the axis of travel and the longitudinal axis of the at least one longitudinal section extend in substantially parallel planes to each other; andthe apparatus has a lateral axis, wherein the lateral axis is:substantially perpendicular to the axis of travel of the apparatus; and substantially parallel to the longitudinal axis of the at least one longitudinal section.

8. The apparatus of claim 7, wherein the apparatus comprises at least a first and second tow arm, the first and second tow arms being releasably coupled to the apparatus at laterally opposite sides of the apparatus to each other.

9. The apparatus of claim 8, wherein the modular sections comprise at least two end sections, and wherein:the end sections are arranged at laterally opposite sides of the apparatus to each other; and each of the first and second tow arms is releasably coupled to a respective one of the end sections.

10. The apparatus of claim 8 or claim 9, wherein at least a portion of each of the first and second tow arms extends laterally beyond a respective one of the outermost sensor housing sections.

11. The apparatus of any preceding claim, wherein the vehicle is a remotely operated towed vehicle ROTV’.

12. The apparatus of any preceding claim, wherein one or more of the modular sections is formed from a composite material.

13. A method of manufacturing the apparatus of any preceding claim, the method comprising: forming the modular sections using a moulding process.

14. The method of claim 13, wherein the moulding process comprises:layering up composite material in a mould;treating the composite material to form a composite modular section; andremoving the composite modular section from the mould.

15. A kit of parts for use with one or more sensors to detect a subsea object, the kit comprising:a plurality of modular sections configured to be assembled to form a structure, the modular sections comprising:a first sensor housing section;a second sensor housing section; andat least one longitudinal section, and wherein:the first sensor housing section is configured to be releasably coupled to one end of the longitudinal section;the second sensor housing section is configured to be releasably coupled to the other end of the longitudinal section; andeach of the first and second sensor housing sections is arranged to house a sensor for detecting the subsea object.

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