Landing craft with fixed and retractable azimuthing drives

Abstract

A marine vessel used for loading and offloading vehicles and cargo that has both excellent seakeeping and beaching properties. The vessel is provided with azimuthing or steerable thrusters below the waterline at the bow and stern of the ship, with the stern end thrusters being retractable into the hull during beaching operations. Because the vessel is beached "stern first" the bow may be designed with better wave breaking and seakeeping features than are on prior landing craft designs.

Description

[0001] 1. Field of Invention[0002] This invention relates to a marine vessel, and more particularly, to a landing craft that uses fixed and retractable azimuthing drives in combination with an improved bow shape to obtain both excellent seakeeping and beaching abilities.[0003] 2. Description of Prior Art[0004] Throughout the history of modern military operations, there has been a requirement to transfer men and materials from ships to a beachhead. Without docking facilities, such transfers are difficult to accomplish. In the twentieth century, particularly during the Second World War, specialized landing craft were developed to facilitate such transfers. Unfortunately, such craft were limited to transporting a relatively small group of men, one or two vehicles, or an inadequate amount of cargo, due to their limited size and cargo weight capacity. Larger marine vessels were limited for such operations due to their inability to effectively and safely "beach" themselves to unload cargo...

AI Technical Summary

Benefits of technology

[0015] The marine vessel described herein has the ability to travel in multiple directions, particularly stern forward, during landing operations on a beach or other unimproved water / land interface. The high maneuverability of the disclosed marine vessel is accomplished through the use of conventional steerable or azimuthing drives mounted below the waterline on the bow and stern portions of the craft.

[0017] The first advantage of this system is it allows a "drive-through" cargo deck. Vehicles, such as tanks, trucks, and humvees, are driven into the cargo area at a loading depot from the bow. The front of the vehicles will then face towards the stem of ship. Once the ship is beached at the designated landing zone, the vehicles can drive off the ship, right onto the beach in a forward gear. By unloading vehicles and other cargo astern of the vessel, the bow of the ship can be designed for excellent seakeeping and wave breaking ability since it is not used for beaching. This feature is also effective for getting on and off the beach since the effects of high surf near the beach are minimized because the efficient, wave breaking bow of the vessel is pointed towards the surf. This eliminates the problem with past landing craft and logistic support vehicles that have had problems getting on and off the beach due to the flat stern slamming into the surf or being pushed by the surf while beaching.

[0018] The azimuthing drive propulsion system adds two advantages over traditional drive systems. First, the bow azimuthing drives provide the capability of full bollard thrust in both directions and are therefore extremely effective for powering off a beach. Second, with at least three drives operating (bow and stern), the vessel has full dynamic position capability while at sea.

Problems solved by technology

Without docking facilities, such transfers are difficult to accomplish.

Unfortunately, such craft were limited to transporting a relatively small group of men, one or two vehicles, or an inadequate amount of cargo, due to their limited size and cargo weight capacity.

Larger marine vessels were limited for such operations due to their inability to effectively and safely "beach" themselves to unload cargo and then return to normal seakeeping operations.

An obvious disadvantage of using one ramp is that vehicles must be "rolled-on" in reverse, such that they can be driven off the vessel in a forward orientation so that they can be immediately used.

When loading / unloading ramps are provided at both the bow and the stern of the ship, such vessel still suffer from several disadvantages, particularly if used during beaching operations.

However, the use of ramps and other offloading systems located on the ship's bow affected the seakeeping ability of the ship as design compromises must be made to the hull design which affect the ability to sail through the water and break waves.

Furthermore, due to the compromised designs of such hulls, the bow ramps would suffer damage from the force of wave impacts, beaching and general sailing operations.

Prior art landing craft are also destabilized by the surf slamming into the flat stern of the ship when beached.

Operation of the propulsion system in this manner is inefficient and taxing on the mechanical systems.

This is difficult in rough surf and can result in loss of vessels during combat operations.

However, there is no discussion in Veronesi et al. of utilizing the disclosed thrusters in combination with a vessel configuration which is appropriate for both seagoing and beaching operations.

While incorporating conventionally known z-axis drives to increase maneuverability , the disclosure of Gulling, et al. does not contribute to the problems associated with prior art landing craft.

Again, while the use of steerable drives is discussed, the apparatus and method of Arpiainen does not disclose how such drives, or the hull configuration of the ship, can be used to accomplish beaching operations while maintaining good seakeeping abilities.

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