Ship propulsion and steering systems

A propulsion and steering system for reducing water mounding along and under a bow and hull of a mono-hull ship thereby enhancing displacement of water by the hull and permitting increase of the beam to length ratio of the ship comprising two or more thrust chambers, each of the thrust chambers passing lengthwise through the hull below a waterline of the ship, each of the thrust chambers having an open bow end and an open stern end, and a bow of the ship configured to channel water into the bow ends of the thrust chambers. Preferred configurations of the bow are disclosed. A propeller or turbine thruster is preferably positioned in each of the thrust chambers for propelling water through the thrust chamber. Each of the thrust chambers preferably has one or more outlet ports passing through an outer wall thereof, the outlet ports positioned aft and adjacent the propeller or turbine thruster, and a gate pivotally secured in the thrust chamber aft and adjacent the outlet ports such that the gate can be pivoted to permit selective channeling of propelled water through the outlet ports to thereby contribute to steering and maneuvering the ship. The gate may be sized and configured to substantially seal the thrust chamber.

FIELD OF THE INVENTION
 The present invention relates to ship propulsion and steering systems, and
 more particularly to a ship propulsion and steering system for reducing
 water mounding along and under a bow and hull of a mono-hull ship, thereby
 enhancing displacement of water by the hull and permitting increase of the
 beam to length ratio of a ship.
 BACKGROUND OF THE INVENTION
 Conventional large ships are generally monohull, with the single hull
 consisting basically of a bow or forward section, a main or midships
 section, and a rear or stern section. Propulsion is generally by one or
 more propellers situated behind or under the stern section, turned by
 shafts rotated by engines conveniently situated at the bottom of the ship,
 usually near the stern section in cargo ships and towards midships in
 passenger and other ships. Steerage is accomplished by one or more large
 rudders situated behind the propellers, with incorporation in some ships
 of thrust chambers containing propellers or pumps situated across the beam
 in the forward and/or aft sections of a ship, and powered by separate
 motors or engines, for maneuvering the ship in harbors and other
 restricted areas. The forces involved in propelling and steering many
 large conventional ships do not permit gears for the reversal of the
 rotation of propeller shafts and/or require a lengthy period of time to
 accomplish reversal of rotation by gears or reversal of engine rotation.
 Without bow and/or stern thrusters, reliance by conventional ships on
 rudders and engine controls may become hazardous under certain
 circumstances (i.e., a ship proceeding downstream during periods of swift
 currents when there are speed and maneuvering restrictions in river ports
 and other restricted areas).
 The bow sections of conventional ships are generally in the form of a wedge
 which divides the water as equally as possible along a central line of the
 bow to displace the water down and along the sides. In doing so, displaced
 water is added to other water forward of the bows, creating a mound, or
 "hill", requiring additional energy to surmount. The mound of water
 basically remains at the bow until the excess water travels away from the
 ship in the form of waves, or "wakes." Increasing the speed of a
 conventional ship increases the volume of water displaced by the bows in a
 given period of time which increases mounding, and also has the effect of
 reducing the volume of water at the midsections of the ship, with a
 resulting mounding of water along the rear portions of the midsections and
 at the stern. Due to the need to reduce friction on the bows and the area
 of forward mounded water, conventional ships are generally constructed
 with a smaller beam to length ratio, with constraints on length resulting
 from torsion and other forces on structural materials requiring deeper
 drafts of hulls to increase cargo and other capacities.
 The limitations imposed by the water displacement process of conventional
 ships, requiring increasing factors of power for smaller increments of
 increased speed, and/or requiring reductions of speed to conserve fuel or
 lessen hazards by its wakes to other ships and marine equipment, shores
 and shore installations, has resulted in a number of concepts and designs.
 To minimize displacement of water at increased speed, marine craft have
 been designed for many years to lift a hull higher in the water, and more
 recent power sources have permitted hulls to have minimum displacement by
 "planing" and/or use of entrapped forced air to lift the hull above the
 water (i.e., hovercraft). Power and construction requirements limit the
 size and/or carrying capacity of such marine craft.
 Other designs use multihulls, with two or more long narrow hulls reducing
 the displacement of water, again increasing speed but with diminished load
 capacities. More recently there has been the concept of a monohull fast
 ship by producing a high pressure area at the bottom portion of the stern.
 U.S. Pat. No. 5,832,856 (Giles).
 Many years ago there were concepts for modifications of the designs of
 ships by incorporating one or more tubes from bows to stern with
 propellers situated both within and outside of the forward and rear ends
 of the tubes. U.S. Pat. Nos. 14,589 (Arnold); 815,270 (Davids); 1,161,453
 (Court). While those earlier concepts had merit, they were based on then
 existing technologies, materials and ship designs, without systematic
 development of an integrated ship propulsion and steerage design,
 requiring total evolution of concepts and design of ships to maximize the
 benefits of reduction of the energy necessary to displace water and use of
 the energy of the displaced water in the propulsion and steerage of a
 ship. In addition, the development of turbine thrusters or "pumps"
 significantly enhance the propulsion of water when contained and operated
 in thrust chambers, compared to enhanced conventional propellers.
 There is thus a need for a ship propulsion and steering system for reducing
 water mounding along and under a bow and hull of a mono-hull ship, thereby
 enhancing displacement of water by the hull permitting increase of the
 beam to length ratio of a ship and enhancing the steering maneuvering of a
 ship, according to the following objectives and description.
 OBJECTS AND SUMMARY OF THE INVENTION
 1. In order to reduce the energy necessary to displace water from the bows
 of a large ship, and to use the energy of the displaced water in the
 propulsion and steerage thereof, a basic objective of the present
 invention is to configure the bows to channel water forward thereof into
 two or more tubes or chambers situated on the bottom, outer sides of a
 ship having a greater beam to length ratio compared to conventional ships,
 propelling the displaced water by means of propellers or turbine thrusters
 within the chambers to flow the water from the forward or bow ends of the
 tubes or chambers through those chambers to the stern section, where
 additional propellers or turbine thrusters would propel the water from the
 stern of the ship for propulsion thereof, and steerage by variation of the
 rotation and/or the angle of the blades of the propellers or turbine
 thrusters.
 2. Another objective is to reduce the friction of water on the outer sides
 of a ship by incorporation of the aforesaid propulsion system in a ship to
 permit a greater beam to length ratio compared to conventional large
 ships.
 3. Another objective is to permit greater stability of a large ship and the
 security of its cargoes by use of a wider beam resulting from the use of
 the aforesaid propulsion system.
 4. Another objective is to reduce the length of a ship, and to minimize the
 reduction of water supporting the midsections of a ship, in order to
 minimize the torsion and other forces induced on conventional ship
 structures due to reduced water support and length thereof, and to reduce
 the mounding of water forward of the bows and along the rear of the
 midsections and stern experienced by conventional ships.
 5. Another objective is to utilize the strength necessary for the chambers
 channeling propelled water within the bottom, outer sides of a ship, to
 provide the basic internal support structures, or "keels", of a ship.
 6. Another objective is to provide electrical and/or hydraulically powered
 motors situated in the vicinity of the propellers or turbine thrusters in
 the chambers, which motors would be powered by a conveniently situated
 engine or engines with electrical generators and/or hydraulic pumping
 systems, and which could provide braking force on the propeller shafts and
 could be rapidly reversed in direction to reverse the rotation of
 propellers or turbine thrusters.
 7. Another objective is to permit incorporation of engines and related
 propulsion equipment, as well as other equipment, navigation and crew
 quarters and other facilities, at convenient locations in a cargo or other
 ships, and in particular to allow unhindered movement of cargo to and from
 the midsections of the ship and/or over and through the stern portions
 thereof.
 8. Another objective is to permit design and construction of the bows of a
 large ship to channel water into the tubes or chambers in the most
 beneficial manner, reducing the friction and other hydrostatic forces
 affecting conventional ships, while also using that water to cushion the
 effect of waves and to provide lifting forces on the bows when
 encountering waves, both within a wave and in the valley between waves.
 9. Another objective is to reduce wakes created by a conventional ship when
 displacing water, which represent wasted energy and are hazardous to other
 ships and marine craft and to shores and installations thereon.
 10. Another objective is to provided gates within the forward and rear
 portions of the thrust/propulsion chambers to manifolds or outlet ports in
 the outer portions of the chambers and direct the propelled displaced
 water from the chambers through the outlet ports in a controlled manner
 and perpendicular to the sides of the ship to provide additional steerage
 of the ship and lateral movements and other maneuvering of the ship.
 11. Another objective is to reduce water friction and weight on the stern
 section of a ship by avoiding the necessity of a rudder, steering the ship
 by means of the propellers or turbine thrusters situated in the chambers
 along the bottom sides of a ship of wider beam, and/or by the water
 propelled from the sides of the ship though manifolds/outlet ports in the
 tubes or chambers.
 12. Another objective is to incorporate electronic systems to control the
 propulsion, steering and maneuvering systems of the ship by a single
 person at various convenient locations on the ship, with each of the
 propeller motors controlled in speed, direction (forward and reverse)
 and/or angle of blades of the propellers, and each of the side thruster
 gates controlled as to volumes of water exiting through the
 manifolds/outlet ports, to provide lateral movements of the ship and
 maximum control of all movements of the ship.
 13. Another objective is to permit closure of gates in the tubes or
 chambers for the purpose of evacuation of water during inspection,
 maintenance and repair of the ship and propellers, and/or to provide
 buoyancy for the vessel and partial double-hull protection of the sides
 and bottom of a ship.
 14. Another objective is to permit design and construction of the stern
 section to permit maximum thrust of displaced water through fixed
 structures of the stern and/or to install gates or other equipment to
 control that thrust.
 15. Another objective is to incorporate equipment and/or substances for the
 generation of electrical and/or hydraulic power for powering propeller
 motors in the event of failure of the main engine or engines.
 In order to achieve the aforesaid objectives, the present invention is
 characterized as a ship propulsion and steering system comprising a
 monohull having bows or a forward section designed and constructed to
 channel all or most of the water forward of the bows in the most
 beneficial manner into two or more tubes or chambers situated within the
 bottom, outer sides (below water lines) of the ship where propellers or
 turbine thrusters situated within the forward parts of the chambers propel
 the water aft through the chambers to the stern section of the ship where
 other propellers or turbine thrusters propel the water from the ship. By
 reducing the mounding of water forward of the bows and the friction and
 other hydrostatic effects of water on the bows, this embodiment permits
 the design and construction of a ship with a greater beam to length ratio
 compared to conventional large ship of the same or lesser displacement,
 having the beneficial effects of reducing friction of water on the sides
 of the ship, reducing torsion and other effects affecting longer
 conventional ships with bows and stern sections lifted by mounds of water
 and with reduced midships water support, and providing enhanced stability
 of the ship and security of cargoes.
 The propulsion chamber systems would be constructed of sufficient strength
 to contain and channel the displaced water, which would also provide the
 basic internal support structures ("double keels") of the ship. The
 propellers or turbine thrusters would be located within the chambers to
 provide the most beneficial movements of displaced water, forward or aft,
 rotated by electrical or hydraulic motors situated in the vicinity of the
 propellers, which could be controlled to brake the rotation of the shafts,
 propellers or turbine thrusts and to be rapidly reversed to reverse the
 rotation of propellers, or turbine thrusters, and/or the angle of the
 blades of propellers could be changed to maximize their thrust of water,
 both forward and aft. The motors would be powered, electrically or
 hydraulically, by an engine or engines conveniently located in the ship
 with related electrical generating and/or hydraulic pumping equipment,
 and, in particular, allowing location of engines and related equipment,
 navigation and crew quarters, and other ship facilities in the forward
 part of a cargo ship, allowing unhindered movements of cargoes to and from
 midsections of the ship and/or through and over the stern portions
 thereof. By channeling forward water through the chambers and propelling
 those waters through the stern sections, the energy of the displaced water
 may be utilized in propulsion of the ship, while reducing the quantity,
 size and speed of wakes which are hazardous to other ships and marine
 craft, shores and shore installations.
 In this embodiment, the propulsion system would achieve the first nine
 objectives (1-9) stated above.
 The first embodiment would permit location of gates within the thrust
 chambers, to the rear of the forward propellers or turbine thrusters and
 to the rear or forward of the stern propellers or turbine thrusters, which
 gates may be rotated to reveal or expose outlet ports or manifolds in the
 outer sides of the thrust chambers and to divert a desired flow of the
 propelled water through those outlet ports perpendicular to the sides of a
 ship to provide lateral forces for the purposes of steerage of a ship and
 maneuvering thereof. Together with variation of rotation and/or the angle
 of the blades of the thrust propellers or turbine thrusters, both forward
 and reverse, this embodiment would avoid the need of a rudder, and achieve
 the tenth and eleventh objectives (10 and 11) stated above.
 The above embodiments would permit the electronic control of the aforesaid
 propulsion and steerage systems by one person using electronic control
 devises which may be physically connected to the electronic system at
 various locations and/or connected by radio, infrared, and other
 transmissions of control signals to that electronic system. This
 embodiment would achieve the twelfth objective (12) stated above.
 The above embodiments would permit the construction of the aforesaid gates
 in the thrust chambers to allow those to close against the sides of and
 seal the thrust chambers, permitting the evacuation of water from the
 portions of the chambers between the gates, for the purposes of
 inspection, maintenance and repair of the chambers, providing additional
 buoyancy for the ship as necessary, and providing partial double hull
 integrity for the ship. Additional gates could be incorporated forward of
 the forward propellers or turbine thrusters and aft or forward of the
 stern propellers or turbine thrusters, to permit evacuation of water from
 the area of the propellers or turbine thrusters to permit inspection,
 maintenance and repair thereof. This embodiment would achieve the
 thirteenth objective (13) stated above.
 To increase the trust of waters propelled from the stern of a ship, gates
 could be incorporated in the stern sections to vary the direction of flow
 of the water, to achieve the fourteenth objective (14) stated above.
 Additional electrical generator and hydraulic pumping equipment, and/or
 other forms of electrical generating substances and equipment, could be
 incorporated in the ship to provide a minimum power source for the
 propulsion motors and other equipment in the event of failure of the main
 engine systems, achieving the fifteenth objective (15) stated above.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
 The preferred embodiments of the invention will now be described with
 reference to the accompanying drawings. The embodiments stated in this
 description and shown in the drawings are representative of a particular
 cargo ship to exemplify the incorporation of the propulsion and steerage
 systems described, each of which may be modified in various ways for
 incorporation in a preferred manner in ships and marine craft, without
 intention to limit in the description and drawings the scope of the
 concepts inherent in the invention.
 As shown in FIGS. 1-7, the invention is a propulsion and steering system
 for reducing water mounding along and under a bow 2 and hull 110 of a
 mono-hull ship 100, thereby enhancing displacement of water by the hull
 110 and permitting increase of the beam to length ratio of the ship 100.
 As shown in FIG. 1, the propulsion and steering system of the invention
 consists generally of two or more thrust chambers 1, each of the thrust
 chambers 1 passing lengthwise through the outer hull below a waterline of
 the ship 100, and each of the thrust chambers 1 having an open bow end 1A
 and an open stern end 1B. The bow 2 of the ship 100 is configured to
 channel water into the bow ends 1A of the thrust chambers 1. For a
 particular ship, four or more thrust chambers 1, larger or smaller, may be
 incorporated, forming the sides of a ship 100 from bottom to waterline 5,
 which under circumstances may form a double hull or protective hull. In a
 preferred embodiment, at least one propulsion means 15,23 (see FIGS. 3-4)
 is positioned in each of the thrust chambers 1 for propelling water
 through the thrust chamber 1. One propulsion means 15 is preferably
 positioned adjacent the bow end 1A of the thrust chamber 1, and a second
 propulsion means 23 is preferably positioned adjacent a stern 1B end of
 the thrust chamber 1. In other embodiments, at least one propulsion means,
 such as 130, is positioned in the thrust chamber 1 between the bow
 propulsion means 15 and the stern propulsion means 23. The propulsion
 means 15, 23, 130 may preferably be selectively reversed to assist in
 maneuvering and steering the ship 100.
 FIG. 1 is a cross-sectional top view of a bottom of a ship 100 showing the
 basic configuration of thrust chambers 1 within the bottom, outer sides of
 a ship 100. The thrust bows 2 in the forward chamber are configured to
 divide and channel water into the forward portions, or bow ends, 1A of the
 thrust chambers 1. Propellers or turbine thrusters 15 in the forward parts
 of the thrust chambers (not shown in FIG. 1; see FIG. 3) force the water
 towards the stern 3 where the water is further propelled by propellers 23
 (not shown in FIG. 1; see FIG. 4) in the stern section 3 through the stern
 thrust chambers 4. The thrust chambers 1 may be configured for a
 particular application, or gates may be incorporated to vary the thrust of
 the propelled water, as will be described in further detail below.
 FIG. 2 is a front view of the thrust bows of a ship 100 configured below
 the water line 5 with plates 6-11 forming "thrust bows" to channel water
 into the forward parts 1A of two thrust chambers 1. As shown in FIG. 2, in
 a preferred embodiment, the configuration of the bow 2 includes, on either
 is side of a central line 112 of the hull 110, a substantially rectangular
 plate 6, 7 depending downward below the waterline 5, a lower end of the
 rectangular plate 6, 7 positioned substantially above a bow end 1A of one
 of the thrust chambers 1; a substantially triangular plate 8, 9 depending
 downward below the waterline 5, an edge of the triangular plate 8, 9
 positioned substantially along the waterline 5, a second edge of the
 triangular plate 8, 9 contiguous with a keel-ward edge of the rectangular
 plate 6, 7; and a keel plate 10, 11, the keel plate 10, 11 being
 contiguous with (a) the central line 112 of the hull 110, (b) a third edge
 of the triangular plate, and (c) a keel-ward edge of the thrust chamber.
 The rectangular plate 6, 7, the triangular plate 8, 9, and the keel plate
 10, 11 are together angled to direct water from the bow 2 into the bow end
 1A of the thrust chamber 1.
 In lieu of flat plates, the forward thrust bows 2 may be curved, as shown
 in FIG. 6 with representative curved lines 120 of the bow, to provide
 maximum effective channeling of water into the thrust chambers 1 of a
 particular ship. In the configuration of FIG. 2, the flat plates may be
 designed and constructed for the particular ship 100 with the plates
 angled, with top end forward and bottom end aft, to provide more
 cushioning and lifting (vertical) force on the bow section when
 encountering waves, with excess wave water thrust forward to cushion and
 lift the bows 2 in the valleys between waves. Also in this embodiment, the
 thrust chambers 1 are shown as square, which may be modified to round the
 thrust chambers, in whole or part. The bow sections 12 above the waterline
 5 are shown in a configuration designed to divide forward water, primarily
 waves, to thrust that water away from the bows and sides of a ship 100,
 rather than down and along the bows and sides of a conventional ship.
 FIGS. 3-4 show top views of forward and stern portions, respectively, of a
 starboard thrust chamber 1 with the top side removed to show preferred
 embodiments of the propulsion means. In a preferred embodiment, the
 propulsion means comprises a water-tight compartment 40 (see FIG. 5)
 positioned above the thrust chamber 1, an electric or hydraulic motor 29
 (see FIG. 5) positioned in the water-tight compartment 40, a drive shaft
 13, 21 of the motor extending downward into the thrust chamber 1 and into
 a gear unit 14, 22 to change the rotation of the drive shaft 13, 21 (e.g.
 from vertical to horizontal), and a propeller or turbine thruster 15,23
 rotatably mounted on the drive shaft 13, 21 via the gear unit 13, 21 to
 thereby propel water through the thrust chamber 1. In the embodiment shown
 in FIG. 7, a second propeller or turbine thruster 130 is rotatably mounted
 on the lower end of the drive shaft 132 via the gear unit 132, in a manner
 well known to those of ordinary skill in the art, to thereby assist the
 first propeller or turbine thruster 130 in propelling water through the
 thrust chamber 1. The propellers 15, 23, 130, 131 may be replaced by more
 efficient turbine thrusters to reduce cavitation and increase the thrust
 of propelled water. Additional propulsion units may also be incorporated
 midships, as shown in FIG. 7, as desired for a particular ship, with or
 without similar side thruster gates 134 and manifolds 135 with side hull
 flap covers 136.
 The force of propelled water through the opened manifolds 17A, 26A, 135
 provides lateral thrust to the ship 100 for steerage and for lateral
 maneuvering thereof. When proceeding in reverse, maneuvering may be
 accomplished by selectively varying the rotation and/or the angle of the
 blades of one or more of the propellers 15, 23, 130, 131. Additional
 manifolds and gates may be incorporated to provide lateral thrust though
 similar manifolds for maneuvering a particular ship when reverse movements
 are frequently expected.
 FIG. 3 is a top view of the forward part of a starboard thrust chamber 1
 with the top side removed. In the forward part of the chamber is a
 propulsion means. In a preferred embodiment, the propulsion means
 comprises a vertical shaft 13, support strut and gear box 14, and a single
 propeller 15 rotated by an electric or hydraulic motor (not shown in FIG.
 3; see FIG. 5, component 29) situated in a water tight compartment 40 (see
 FIG. 5) over the shaft 13 and top side of the thrust chamber 1. To the
 rear, or aft, of the propeller 15 is a gate 16, hinged to the inside of
 the thrust chamber and turned by an electric or hydraulic motor (not shown
 in FIG. 3; see FIG. 5, component 34) situated in a water tight compartment
 40 over the shaft 16A of the gate. Each of the thrust chambers 1
 preferably has one or more outlet ports 17A, 26A passing through an outer
 wall 1C thereof. The outlet ports 17A, 26A are positioned aft and adjacent
 the propulsion means 23. A gate 16, 24 is pivotally secured in the thrust
 chamber 1 aft and adjacent the outlet ports 17A, 26A. An
 electro-mechanical pivot means 16A, 24A is provided for pivoting the gate
 to thereby permit selective channeling of propelled water through the
 outlet ports 17A, 26A to thereby contribute to steering and maneuvering
 the ship.
 Each gate 16, 24 may be preferably sized and configured to substantially
 seal the thrust chamber 1. A stop 18, 25 may be preferably provided on an
 inner wall 1D of the thrust chamber 1, the stop 18, 25 being positioned to
 engage a stern-ward side 16B, 24B of the gate 16, 24 when the gate 16, 24
 is pivoted to a closed position, to thereby permit selective closure of
 the thrust chamber 1 aft the respective gate 16, 24. The gate 16 is
 configured in this embodiment to the dimensions of the thrust chamber 1,
 and is shown partially opened to channel water propelled by the propellers
 15 to force the water through one or more manifolds or outlet ports 17A
 situated vertically through the outer side/outer wall 1C of the thrust
 chamber 1.
 As shown in FIG. 3, the manifolds/outlet ports 17A may be closed by a flap
 valve cover 17 (shown partially open) hinged on the outside of the thrust
 chamber forward of the outlet port 17A, held over and closing the manifold
 by springs and water pressure when the gate 16 is closed against the side
 of the thrust chamber 1, and opening when the gate 16 is opened and water
 is propelled through the manifold/outlet port 17A. In a preferred
 embodiment shown in FIGS. 3-4, a flap valve cover 17, 26 is provided. The
 flap valve cover 17, 26 is sized and configured to close the flap valve
 cover's 17, 26 respective outlet port 17A, 26A. The flap valve cover 17,
 26 is hinged to an outside surface of the outer wall 1C fore and adjacent
 the outlet port 17A, 26A. A spring means 17B, 26B is provided, the spring
 means 17B, 26B being positioned to close the flap valve cover against the
 outlet port when the gate 16, 24 is pivoted to the closed position. The
 spring means 17B, 26B permits the outlet port 17A, 26A to open when the
 gate 16,24 is pivoted to channel propelled water through the outlet port
 17A, 26A. In this configuration there is also a lip or stop 18 installed
 on the inner sides of the thrust chamber 1 against which the gate 16 may
 be closed. If closure of the thrust chamber 1 by a large gate 16 is not
 necessary for a particular ship, a smaller gate 16 or other mechanical
 closure of the manifolds may be incorporated.
 A bar grating 19 may preferably be lowered within the forward part of the
 thrust chamber 1 from a watertight compartment 40 above the thrust chamber
 1, such as when the ship 100 may encounter logs or other large objects
 (e.g., when the ship 100 is maneuvered in a river port without cargo or
 ballast, exposing the thrust bows to floating logs etc.), and selectively
 lifted up into the compartment 40 to reduce water resistence. In a
 preferred embodiment, a grating 19 is positioned forward of the bow
 propulsion means 15. The grating 19 provides a water permeable barrier for
 preventing logs and other water-borne debris from passing through the
 thrust chamber 1. The grating 19 is preferably removable or retractable by
 an electrical or hydraulic motor, e.g. 29 in FIG. 5. Logs or other objects
 may be removed through a side hull flap 20 and manifold/outlet port 20A
 (shown partially open), and/or by reversal of the propeller. If
 beneficial, a removable sealing gate (not shown) may be incorporated
 forward of the bar grating 19, which may be lowered from a water tight
 compartment in the upper hull to be supported by and against the bar
 grating 19 to permit evacuation of water in the thrust chamber when aft
 gate 16 is closed for inspection, maintenance and repair of a propeller or
 turbine thruster.
 FIG. 4 is a top view of a propulsion unit in the stern section of a
 starboard thrust chamber 1, comprising a vertical shaft 21, support strut
 and gear, box 22, single propeller 23, gate 24 (shown partially open), lip
 or stop 25 for closure of the gate 24, and flap valve cover 26 (shown
 partially open), in the stern section of the starboard thrust chamber 1.
 In this embodiment the gate 24, manifold/outlet port 26A and flap valve
 cover 26 are shown situated to the rear of the propeller 23, which could
 be installed forward of the propeller 23 if preferred. Also in this view,
 a rudder gate 27 (shown partially in the stern thrust chamber) is
 installed in the starboard stern thrust chamber 1, hinged 28 adjacent the
 stern end 1B and turned by an electric or hydraulic motor 34 (FIG. 5) to
 vary the thrust of the water exiting the stern, for the purpose of
 optimizing the thrust under particular circumstances and further assisting
 in steering and maneuvering the ship 100. In this embodiment and in FIG.
 3, there are single propellers 15, 23 in each propulsion unit, which may
 be modified, as shown in FIG. 7, to install dual propellers 130, 131, one
 forward and one aft of the shaft 132 and gear box, on the propulsion
 units, which could increase thrust of and modify the flow of propelled
 water.
 FIG. 5 is a top view of a ship 100 with the midships and stern decks
 removed to show the thrust chambers 1 with electrical motors 29 situated
 in water tight compartments over the shafts 13, 21 and propellers 15, 23,
 the forward superstructure 30 for navigation of the ship 100, electronic,
 electrical and other equipment and controls, crew quarters and other
 facilities (not shown), together with an engine and control compartment 31
 aft of the superstructure 30, containing in this embodiment a large
 electrical generating unit 32 and axillary electrical generating units 33.
 From control panels 34 in the compartment 31, electricity would be
 transmitted to power the propulsion motors 29, gate motors 34, and other
 motors by means of transmission wires in conduits (not shown). As stated
 before, one or more additional propulsion units may be installed in the
 midship sections of the thrust chambers 1, as shown in FIG. 7, depending
 on the design and intended use of a particular ship.
 Also shown in FIG. 5 is a preferred embodiment in which a bottom deck 35 is
 situated over beams fixed to and connecting the thrust chambers 1, which
 are also covered by bottom plates (not shown), forming a continuous double
 bottom hull from bow to stern. Also shown on the stern is a large ramp 36
 similar to ramps on conventional "roll on-roll" off ships, for the purpose
 of loading and unloading cargoes on pallets or in containers, track
 trailers and rail cars, through the stern of a ship, which may be enhanced
 due to the wider beam of the depicted ship.
 Although the present invention has been described in terms of specific
 embodiments, it is anticipated that alterations and modifications thereof
 will no doubt become apparent to those skilled in the art. It is therefore
 intended that the following claims be interpreted as covering all such
 alterations and modifications that fall within the true spirit and scope
 of the invention.