GB2077197A

GB2077197A - Minehunting and disposal system

Info

Publication number: GB2077197A
Application number: GB8017191A
Authority: GB
Original assignee: Vosper International Ltd
Current assignee: Vosper International Ltd
Priority date: 1980-05-23
Filing date: 1980-05-23
Publication date: 1981-12-16
Also published as: EP0040988A3; EP0040988A2

Abstract

Mine cleaning is performed by a parent ship having support facilities for a plurality of operational craft and the operational craft are relatively small and provided with known mine detection and destruction equipment. The parent ship is preferably designed and equipped so as to be capable of carrying the operational craft on board, such that the operational craft may be transported to the area of deployment. The operational craft preferably have hulls providing a substantial portion of its buoyancy submerged together with a relatively small water plane area, for example a Small Water Plane Area Twin Hull type craft. This system reduces the number of personnel exposed to a single risk and the operational craft present a low magnetic signature and low noise generation due to their size and these endowments are particularly enhanced if the preferred form of hull is utilised. <IMAGE>

Description

1

GB 2 077 197 A 1

SPECIFICATION

Minehunting and Disposal System

The present invention relates to a minehunting and disposal system.

5" The conventional system for hunting for and disposing of marine mines consists of sending a relatively large ship normally 35 to 47 metres in length into the water area which is suspected of having been mined. The conventional 10 minehunting ship has a crew of the order of 30 members. Such ships are provided with sonar detection equipment which is used to locate mines together with mine destruction equipment which is used in order to dispose of the mines 15 once they have been located. Several disadvantages exist in the known system. There is relatively large number of personnel at risk, and the system is costly because the ships involved have to have a low magnetic signature together 20 with a low 'noise' generation.

With a view of mitigating at least one of the above mentioned disadvantages the present invention provides a minehunting and disposal system comprising a parent ship providing 25 support facilities for a plurality of operational craft, the operational craft being relatively small and being provided with known mine detection and destruction equipment.

Preferably, the operational craft have a hull 30 form which has a substantial portion of its buoyancy 'below the waves' together with a relatively small water plane area. Such semi-submerged hulls are known perse, examples being the 'semi-submersible' oil-rig and the 35 floating single leg hulls.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

40 Figures 1 a and b show, in diagrammatic form, side and end elevations respectively of an operational craft employing the 'semi-submersible' type of hull; and

Figures 2a and b show, in diagrammatic form, 45 side and end elevations respectively of an operational craft employing the 'floating single leg' type of hull.

« The exemplary minehunting and disposal system consists of a parent ship and a number of 50 smaller operational craft. The parent ship is ■ intended to be anchored in a safe area and to act as a general back up and refuelling ship for the operational craft. The operational craft are deployed for short periods in the area known to be 55 or suspected of being mined and return to the parent ship for refuelling or crew changes.

This system has many advantages over the conventional system which comprises one or several independent ships of relatively large size. 60 The operational craft need only carry basic facilities required for a single day's operations. Only a small crew is required to operate the mine detection and disposal equipment. Large supplies of fuel and munitions need not be carried and only basic amenities need be provided since the craft need only be deployed for short periods. Consequently the craft may be small and relatively inexpensive. The number of crew at risk is drastically reduced typically from the thirty or forty crew members of a conventional minehunting ship to the five or six crew members required to control one of the operational craft.

The parent ship can be a stern trawler or an offshore supply vessel which has been specially converted. The parent ship is less expensive than a conventional minehunting ship. The parent ship is provided with a crane structure together with sufficient space and stability to store the operational craft onboard. This enables the operational craft to be transported to the vicinity of the minehunting area by the parent ship.

The operational craft are small enough (length 9 to 12m, breadth 6 to 9m) and light enough (30 tonnes) to be taken onboard the parent ship. They are capable of providing a steady platform for sonar transducer equipment, used for mine detection, in rough seas. A typical maximum sea state in which the operational craft would function would be the top end of Beaufort Force 5 open sea. The crew of an operational craft would typically consist of six members consisting of 4 sonar operators, 2 on duty and 2 off duty at any one time, one helsman and one officer. Each operational craft is equipped with a known minehunting sonar and a known remotely controlled mine disposal vehicle. Six mine disposal weapons are carried and a spare charged battery for the mine disposal vehicle. There are no battery charging facilities on the operational craft as these are provided on the parent ship.

In order to provide an operational craft of the required weight, size and stability the hull is of the semi-submerged type. The hull has most of its buoyancy 'below the waves' and at the same time has a small waterplane area. Due to the utilization of such a hull the operational craft has a wave response which is reduced by an order of magnitude in comparision with an ordinary boat hull.

One example of an operational craft is illustrated in Figures 1 a and b. This embodiment utilizes the 'semi-submersible' type of hull. The operational craft comprises a platform 10 having a front cabin area 12 and a rear open deck area 14. The 'semi-submersible' hull 16 comprises a fore and an aft leg 18 on both sides of the platform 10. On each side of the platform 10 and fore and aft legs 18 are joined at their lower ends by a hull body 20 which houses a propulsion unit having a propeller 22 at its rear end. A structural strengthening and hydrodynamic cross member 26 interconnects the two hull bodies 20. The buoyancy of the hull 16 is such that the base of the platform 10 is held approximately one and a half metres (half of the maximum wave height) above the still water level 24. The hull bodies 20, which constitute the main buoyant volumes of the hull, float at slightly less than 3 metres below the still water level 24. Suspended from the platform

65

70

75

80

85

90

95

100

105

110

115

120

125

2

GB 2 077 197 A 2

10 beneath the cabin area 12 and centrally with respect to the breadth of the platform 10 is a further leg 28. At the lower end of the leg 28 is positioned the sonar transducer 30, signals to and 5 from which are transferred to and from the cabin 12. The leg 28 is strengthened by member 32 which inter-connects the leg 28 with the hull bodies 20. A mine disposal vehicle 34 is held by a suitable supporting means 36 at the rear of the 10 platform 10. The craft illustrated in Figures 1(a) and (b) is 12 metres in length, 9 metres in breadth and weighs 30 tons. It has a tons per foot (sinkage) of 1.07, a shortest natural period of motion of 7.7 seconds (heave) and a metacentric 15 height of 3.0 ft.

An alternative operational craft is shown in Figures 2(a) and [b). This embodiment is based upon the 'floating single leg' type of hull. The platform is generally similar to that shown in 20 Figures 1 (a) and (b) and is given the same reference numerals. The hull 40 comprises a single leg 42 positioned centrally with respect to the underneath of platform 10. A hull body 44 is attached to but laterally displaced from each side 25 of the leg 42. Each hull body 44 houses a propulsion mechanism and is provided at its rearward end with a propeller 46. The leg 42 extends below the level of the hull bodies 44 and is provided with a 'free flooding' tank 48, both 30 fore and aft, below the level of the hull bodies 44. The base of each 'free flooding' tank 46 is provided with ballast 50 which may be of a suitably heavy material such as uranium. Rearward of the leg 42 and below the level of the 35 hull bodies 44 is a fin 52. The buoyancy of the hull bodies 44 is such that the platform 10 is held approximately 1^- meters above the still water level 24 whilst the hull bodies are approximately the same distance below the still water level 24. 40 The leg 42 reaches to a depth of 6 or 7 metres and suspended from the bottom of the leg 42 is the sonar transducer 54.

The relatively small size of the operational craft together with the fact that most of the necessary 45 electrical equipment is positioned on the craft's platform, which is held out of the water, present several advantages of their use in a minehunting system. The operational craft have an extremely low magnetic signature and also produce very

50 little underwater noise as the main 'noise'

producing machinery is also situated out of the water. The amount of power being transferred to the propellers is small due to the size of the craft. Low 'noise' and low magnetic signature are

55 desirable features of a minehunting system since mines are known which may be triggered by the detection of such features exceeding a preset . threshold. Although the top speed of the operational craft is (approximately) only 6 knots,

60 this is adequate for minehunting purposes. The operational craft have a high shock resistance due to their size and the fact that most of the equipment is situated high above the water.

Claims

Claims

65 1. A minehunting and disposal system comprising a parent ship and a plurality of operational craft, the parent ship providing support facilities for the operational craft and the operational craft being relatively small and being

70 provided with mine detection and destruction equipment.
2. A minehunting and disposal system as claimed in claim 1, wherein the parent ship has sufficient space and stability and is provided with

75 apparatus for loading and unloading the operational craft such that the operational craft may be stored on the parent ship.
3. A minehunting and disposal system as claimed in claim 1 or 2, wherein each operational

80 craft has a hull which, when floating, has a substantial portion of its buoyancy submerged and presents a relatively small waterplane area.
4. A minehunting and disposal system as claimed in claim 3, wherein the hull of each

85 operational craft is of the Small Waterplane Area Twin Hull type.
5. An operational craft for a minehunting and disposal system as claimed in claim 3 or 4.
6. A minehunting and disposal system

90 substantially as herein before described with reference to and as illustrated in the accompanying drawings.
7. An operational craft for a minehunting and disposal system substantially as herein before

95 described with reference to and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.