FIELD

The present invention relates to a system comprising an underwater vessel, submarine or submersible and a surface vessel.

BACKGROUND

Underwater vessels are well known in the art and are provided for a variety of different uses ranging from underwater exploration, environmental monitoring, surveillance and warfare. The size of such vessels also varies greatly from an autonomous vessel having no crew and being controlled remotely or via an in-built program, up to a nuclear-powered submarine having a crew numbered in tens of personnel.

For any type of underwater vessel except for the very smallest, transporting the vessel from a base to a target destination can be troublesome. The vessel is usually too large to be transported on board a vessel or aircraft and can only travel relatively slowly, thereby rendering a speedy deployment all but impossible.

A further complication arises due to the generally curved profile of the hull of the underwater vessel leading to a lack of stability in certain situations, such as when out of the water.

It is an aim of embodiments of the present invention to addresses issues in the prior art, whether mentioned herein or not.

SUMMARY

According to an aspect of the present invention, there is provided a system comprising: a first, underwater, vessel provided with a substantially flat lower surface; and a second, surface, vessel, comprising a floodable well deck arranged to receive and accommodate the first vessel. In an embodiment, the flat lower surface has a length in the range 80 to 90% of the overall length of the entire underwater vessel.

In an embodiment, the flat lower surface has a width in the range 20 to 30% of the widest part of a body of the underwater vessel.

In an embodiment, the underwater vessel is provided with a coupling point located towards the front of the vessel to facilitate docking of the underwater vessel in a mother vessel.

In an embodiment, the underwater vessel is provided with a plurality of further coupling points to tether the underwater vessel in place within the second vessel.

In an embodiment, the well deck of the second vessel is provided with a plurality of rollers or skid beams in its floor to facilitate docking of the first vessel.

In an embodiment, the plurality of rollers are able to be locked to prevent rolling.

In an embodiment, the well deck is provided with an innermost surface which is provided with a buffer region to protect both the first and second vessel during a docking operation.

According to an aspect of the present invention, there is provided a method of docking the first vessel of claim 1 in the well deck of the second vessel of claim 1 comprising the steps of: flooding the well deck; attaching a tether to the second vessel; and winching the second vessel into the well deck.

In an embodiment, the winching causes the lower flat surface of the first vessel to contact at least one roller provided in a floor of the well deck.

In an embodiment, there is a further step of securing a plurality of additional tethers to a plurality of coupling points on an exterior of the second vessel and securing the additional tethers to a plurality of anchor points in the well deck.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will now be described by way of example only with reference to the figures, in which:

Figure 1 shows a longitudinal view of an underwater vessel according to an embodiment of the invention;

Figure 2 shows a partial view of an LPD and underwater vessel according to an embodiment of the present invention; and

Figure 3 shows a method according to an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention provides a system comprising a submarine or underwater vessel, the underwater vessel being able to operate independently and to operate underwater to perform one or more functions, such as surveillance, environmental monitoring, seabed surveys or military operations.

The underwater vessel is able to operate for extended periods. It may be provided with a crew or it may be arranged to operate substantially autonomously.

The underwater vessel is preferably fuelled by rechargeable battery cells, which may be charged before or during a particular operation begins.

The underwater vessel is provided with a substantially flat lower surface. This is provided to allow the vessel to remain for a period on the seabed. A typical prior art submarine has a substantially cylindrical profile and is substantially circular or elliptical in cross-section. In any event, a prior art submarine does not have a substantially flat lower surface. Due to their curved outer profile, prior art submarines are unable to sit on the seabed without toppling. Further, prior art submarines would typically have difficulty sitting on the seabed without risking structural damage, high ground pressures on the hull and digging into the seabed. Embodiments of the present invention are able to sit for extended periods on the seabed, without such problems.

In order to deploy an underwater vessel to a particular location, problems will be encountered if the destination is further away than the vessel can travel to in an allowed period of time. The time take may be longer than desirable and/or the distance may be beyond the range of the vessel. In either case, it can be necessary to transport the vessel to the destination by means of a further vessel. In the present case, the further vessel is a part of the system which forms an embodiment of the invention. The further vessel, arranged to transport the underwater vessel is a surface vessel, usually known as a Landing Platform/Dock, LPD, or Amphibious Transport Dock. Such a vessel has a so- called well deck located, usually, at the rear of the vessel. The well deck can be flooded, usually by means of a large door at the rear of the ship. The well deck can then receive and discharge amphibious vehicles and landing craft.

However, the larger types of LPD are of a size to receive and accommodate a relatively large underwater vessel and transport it more rapidly than would be possible if the underwater vessel were to travel under its own power.

In detail, Figure 1 shows a general longitudinal view of an underwater vessel 2 forming part of the system according to an embodiment of the present invention. The view is partly sectional and shows various features of the vessel, including bridge fin 22 and hydroplanes 23. The exact configuration of these components is not important in understanding embodiments of the present invention.

Most importantly, Figure 1 shows the substantially flat lower surface 21 of the vessel 2. The flat lower surface is arranged to run along a majority of the length of the vessel and is preferably in the range 80 to 90% of the overall length, Most preferably, the flat lower surface extends along all of the lower surface except for the fore and aft sections where the hull tapers. The flat lower surface is arranged to have a width in the range 20 to 30% of the overall width of the widest part of the body of the vessel. In the embodiment shown in Figure 1, the width of the flat lower surface is approximately 25% of the width of the widest part of the body of the vessel.

Figure 2 shows the well deck 10 of an LPD or surface vessel 1 which is arranged to accommodate the underwater vessel 2. The remainder of the LPD is not shown, for brevity and clarity. Figure 2 should be referred to in conjunction with Figure 3, which shows a flowchart relating to an embodiment of the present invention.

The well deck 10 is opened and flooded by means of door 14 at the rear of the vessel. From the configuration shown, where the underwater vessel 2 is stowed in the well deck 10, it can be released and launched by floating free from its moorings and can then set about its business.

When it comes time to dock again, the process is reversed with some differences. It would generally be unwise and possibly unsafe to attempt to manoeuvre the underwater vessel into the well deck whilst the underwater vessel is powered and moving at even quite a slow speed.

It should be noted that the underwater vessel 2 has a suitable amount of reserve of buoyancy (ballast tank volume) to enable it to reach surface draughts which are compatible with the surface vessel 1.

In order to dock, the well deck 10 is flooded 102. The underwater vessel 2 approaches the LPD 1 and a tether 13 is attached 104 to a coupling point provided on the underwater vessel 2 at or near its frontmost portion. The tether 13 is connected to a winch (not shown) and the winch operates 106 to pull the vessel 2 into the well deck 10.

In order to ease the docking procedure, a plurality of rollers 11 are provided in a floor of the well deck. These are arranged to lie across a substantial part of the width of the well deck and to rotate freely i.e. without power. The rollers contact the generally flat lower surface and during the winching operation 106, the vessel 2 is self-supporting. The rollers 11 may be replaced by skid beams which, rather than rolling, reduce the friction of an incoming vessel and produce substantially the same effect.

Once the first roller is encountered, the vessel 2 continues its entry into the well deck 10 as a result of the winching operation. Successive rollers 11 are encountered until the vessel 2 reaches the point of maximum ingress, as shown in Figure 2. At this point, the winch is stopped. The vessel 2 now rests on a plurality of rollers 11. The rollers may be locked into position to prevent further movement of the vessel. Additionally, further tethers or other mechanical devices, such as steadies or hold-fasts, may be attached 108 to one or more anchor points on the vessel and then secured to various points around the interior of the well deck 10 to prevent the vessel from moving as the LPD 1 travels to its destination.

Instead of the rollers 11, one or more longitudinal guide rails can be provided forming a sort of slipway to guide the vessel 2 into position. Other means of guiding the vessel into the well deck 10 will be apparent to the skilled person and the above examples are illustrative only and not intended to be limiting.

At the innermost part of the well deck 10, there is a buffer region 12, which comprises a relatively cushioned tor deformable region to protect both the vessel 2 and the LPD 1 in the event that the vessel 2 over travels during docking and strikes the forward part of the well deck 10. The tether 13 protrudes through the buffer region 12 and the winch is located behind the buffer region 12.

Once docked and secured, the well deck can be cleared of water and the LPD can go on its way. By means of a system comprising the LPD 1 and underwater vessel 2, the underwater vessel can be deployed relatively quickly where needed and is not limited by its own inherent range capacity. The system, comprising the underwater vessel 2 and surface vessel 1, is able to provide advantages in operational capability which neither vessel would be able to provide individually.