Abstract:
An unmanned autonomous submarine which can float, dive and move in water to perform various tasks. The submarine includes a pressurized cabin which is necessary for the diving and flotation system to work properly. This also helps to increase its sealing power against water leakage into the cabin. The submarine is autonomous, that is automatic and self controlled. It is propelled by water jet propulsion. It can be programmed to dive to preset depths, move along preset trajectories, and return to the base after completing the assigned tasks. A remote control option is provided in order to perform special tasks. The submarine is equipped with several sensors that can measure depth, orientation, attitude, location and speed. It is also equipped with an underwater video camera that can send wireless video pictures from underwater to a monitor above water surface.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/726,498, filed Oct. 12, 2005, and U.S. Provisional Application No. 60/778,004, filed Feb. 28, 2006, the contents of which are incorporated by reference herein and made a part of this application. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to submersible vehicles, and particularly to unmanned autonomous submarines, and sometimes referred to as “small” submarines.  
       BACKGROUND OF THE INVENTION  
       [0003]     There have been numerous unmanned submarines designed to explore or perform other underwater tasks and functions, as required. The submersible vehicle (i.e., a submarine) includes various systems, such as a ballast system for submersing or floating the submarine, a propulsion system for propelling the submarine, a navigation or steering system for maneuvering the submarine, and various sensors and controllers for controlling the submarine and providing information regarding the underwater environment.  
         [0004]     For example, U.S. Pat. Nos. 1,571,833, 5,235,930, 5,711,244, and 6,655,313 disclose a submarine body from separate sections that are joined together and include seals. U.S. Pat. Nos. 1,310,877, 1,488,067, 3,379,156, 3,478,711, 3,667,415, 3,800,722, 3,818,523, 3,943,869, 3,946,685, 4,029,034, 4,265,500, 5,129,348, 6,371,041 and 6,772,705 disclose ballast means combining water and air through a system of valves and piping for controlling the depth direction of a submarine. U.S. Pat. Nos. 3,122,121, 3,176,648, 3,474,750, 3,492,965, 3,550,386, 6,065,418, 6,807,921 and 6,581,537 disclose fluid propulsion of a vessel through the handling of the fluid from the bow to the stem of the vessel. U.S. Pat. Nos. 3,561,387, 6,269,763, 6,484,660, 6,662,742 and U.S. Publication No. 2002/0134294 disclose use of a plurality of sensors and structural concepts and relate generally to the state of the art. U.S. Pat. Nos. 6,926,567, 6,800,003, 6,716,075, 6,629,866, 6,453,835, 3,301,132, 340,237, U.S. Patent Publication No. 2001/0010987 and Japanese Pat. Application No. 356071694 relate to fluid deflection.  
         [0005]     None of the known patents or publications disclose or suggest an unmanned autonomous submarine as disclosed and claimed herein.  
       SUMMARY OF THE INVENTION  
       [0006]     In general, it is an object of the present invention to provide an unmanned autonomous small size submarine as described herein. This submarine is a surface/underwater vehicle which can float, dive and move in water to perform various tasks. One important feature of the submarine is the pressurized cabin which is necessary for the diving and flotation system to work properly. This also helps to increase its sealing power against water leakage into the cabin. The submarine is autonomous, that is, automatic and self controlled. It is propelled by water jet propulsion. It can be programmed to dive to preset depths, move along preset trajectories, and return to the base after completing the assigned tasks. In addition to the autonomous part, a remote control option is provided for emergency situations or in order to perform special tasks. The submarine is equipped with several sensors that can measure depth, orientation, attitude, location and speed. It is also equipped with an underwater video camera that can send wireless video pictures from underwater to a monitor above water surface.  
         [0007]     Various objectives of the unmanned autonomous submarine are to perform several tasks above and under water replacing human divers who can be subjected to danger in such environment; minimize the cost of underwater operations such as exploration, rescue, photography, and inspection of submerged structures, such as ship hulls, oil rigs, dams, etc.; monitor various objects under water and transmit live video and pictures to the operator on board of a commanding boat above water; be used as a carrier and base for underwater robotics, among other undersea functions and tasks.  
         [0008]     In one embodiment, the unmanned autonomous submarine comprises a hull formed by at least two hull sections and defining an interior cabin therein and adapted to retain pressurized air. A plurality of fasteners are affixed to the hull sections and adapted for joining the at least two hull sections. The plurality of fasteners can e internally and/or externally affixed to opposing connecting ends of the hull sections.  
         [0009]     A plurality of hydrofoils is attached to opposed external side surfaces of the hull sections for providing stability and maneuverability of the hull. The submarine further includes a propulsion system for providing propelling force to the hull.  
         [0010]     A ballast system is included for raising and submersing the hull. The ballast system comprises a ballast tank adapted to receive a predetermined level of water externally from the submarine and a predetermined amount of the pressurized air from the cabin; and a compressor coupled to the ballast tank to form a closed loop system. The compressor is adapted to force air into the cabin from the ballast tank to increase the water level in the tank and thereby cause the hull to submerge, and the compressor being adapted to force air into the ballast tank from the cabin to decrease the water level in the tank and thereby cause the submarine to ascend.  
         [0011]     In one embodiment, the submarine includes a sealable opening formed in the upper portion of one of the hull sections. The sealable opening provides access into the interior cabin.  
         [0012]     In one embodiment, the plurality of fasteners includes a plurality of clamps. Alternatively, the plurality of fasteners can include a plurality of bolts positioned on one of the connecting ends of a hull section and threaded into a corresponding plurality of nuts affixed to an opposing connecting end of an adjacent hull section.  
         [0013]     In one embodiment, the submarine further comprises an o-ring inserted between each adjacent hull section. In an alternative embodiment, the submarine includes a reinforcing ring inserted between each adjacent hull section, either with or without the o-ring.  
         [0014]     In one embodiment, the ballast tank comprises a plurality of partitions to prevent water in the tank from destabilizing the submarine. Further, the ballast tank can include a sealable opening formed at its bottom for controlling flow of water in or out of the tank. Additionally, the ballast system can include at least one solenoid valve for controlling air flow between the cabin and the ballast tank.  
         [0015]     In one embodiment, the propulsion system includes a first water pump positioned in the cabin, a forward inlet port formed in a forward hull section of the hull sections and coupled to the pump via a first conduit, and an aft outlet port formed in an aft hull section of the hull sections and coupled to an output of the first pump via an aft conduit. The first pump draws water external to the hull through the forward inlet port and first conduit, and forces the water through the aft outlet port to propel the submarine in a forward direction. Alternatively, the first water pump draws water external of the hull through the aft outlet port and the aft conduit, and forces the water through the forward inlet port to propel the submarine in a reverse direction.  
         [0016]     The propulsion system can further include a second aft outlet port formed in the aft hull section and coupled to the first pump via a second aft conduit. The aft conduits are regulated to control water flow therethrough to provide steering of the submarine.  
         [0017]     In another embodiment of the propulsion system, a second water pump is serially coupled to the first water pump. The second water pump is deactivated while the first pump is activated to propel the submarine in the forward direction. Similarly, the first pump is deactivated while the second pump is activated to draw water external to the hull through the aft outlet port and aft conduit, and force the water out of the forward inlet port to propel the submarine in a reverse direction.  
         [0018]     In yet another embodiment of the submarine, a plate is pivotably attached in a vertical direction in the aft outlet port. The vertically positioned plate is rotatable to direct the water jetted out of the aft outlet port at a predetermined angle to steer the submarine. Preferably, a vertical rudder rotatable attached to the aft hull section, and a link coupled between the rudder and vertical plate. Rotation of the plate is controlled by rotation of the rudder.  
         [0019]     In yet another embodiment of the propulsion system, the propulsion system includes a forward water pump positioned in the cabin, a forward inlet port formed in a forward hull section of the hull sections and coupled to the forward pump via a forward conduit, and a pair of parallel water pumps positioned in the cabin. The parallel pumps are coupled to the forward water pump via a Y-shaped conduit. A pair of aft outlet ports is formed in an aft hull section of the hull sections. Each aft outlet port is coupled to a corresponding one of the parallel water pumps via a second conduit.  
         [0020]     At least one of the parallel water pumps draws water external to the hull through the forward inlet port and forward conduit, and forces the water out of the corresponding aft outlet port to propel the submarine in a substantially forward direction. Preferably, the forward water pump is deactivated when the pair of parallel water pumps is activated to propel the submarine in a substantially forward direction. Alternatively, the pair of parallel pumps can be deactivated while the forward pump is activated to draw water external to the hull through the aft outlet ports and Y-shaped conduit, and force the water out of the forward inlet port to propel the submarine in a reverse direction.  
         [0021]     In another embodiment, the pumps can be utilized to steer the submarine. In particular one of the parallel pumps is either throttled back or deactivated while the other parallel pump is activated to steer the submarine in a predetermined direction.  
         [0022]     In one embodiment, the submarine further includes a vertical rudder rotatably attached to the aft hull section of the hull sections for steering the submarine. Further, the plurality of hydrofoils can include a pair of aft hydrofoils rotatably attached to opposing side surfaces of an aft hull section of the hull sections. The rotatably attached hydrofoils enable the submarine to submerge and ascend. Additionally, the plurality of hydrofoils can include a pair of forward hydrofoils fixedly attached to the opposing side surfaces proximate a forward hull section of the hull sections. The fixedly attached hydrofoils provide stability for the submarine. Alternatively, the pair of forward hydrofoils is rotatably attached to the opposing side surfaces proximate a forward hull section of the hull sections. The rotatably attached hydrofoils enable the submarine to submerge and ascend.  
         [0023]     In one embodiment, the hull sections include a forward hull section, an aft hull section, and a middle hull section attached therebetween the forward and aft hull sections via the plurality of fasteners.  
         [0024]     In yet another embodiment of the propulsion system, the propulsion system includes a pair of forward inlet ports formed in a forward hull section of the hull sections, and a pair of parallel water pumps positioned in the cabin. Each parallel pump is coupled to a corresponding one of the pair of forward inlet ports via a forward conduit. A pair of aft outlet ports is formed in an aft hull section of the hull sections, where each aft outlet port is coupled to a corresponding output of one of the parallel water pumps via an aft conduit. At least one of the parallel water pumps draws water external of the hull through the corresponding forward inlet port and forward conduit, and forces the water out of the corresponding aft outlet port to propel and steer the submarine in a substantially forward direction. Alternatively, at least one of the parallel water pumps draws water external to the hull through the corresponding aft outlet port and aft conduit, and forces the water out of the corresponding forward inlet port to propel and steer the submarine in a substantially reverse direction.  
         [0025]     In any of the aforementioned embodiments, the submarine can further include a programmable controller for controlling operations of the submarine. Additionally, one or more sensors can be installed on the submarine for providing electrical signals to the controller for further controlling the submarine operations. The one or more sensors can include depth sensors, GPS system sensors, pressure sensors, position and orientation sensors, speed sensors, leakage sensors, audio sensors and video sensors, among other sensors. Further, at least one robotic arm can be mounted to the hull and electrically coupled to the controller.  
         [0026]     In any of the aforementioned embodiments, the submarine can further include at least one battery for providing power to the submarine. In one embodiment, the at least one battery is rechargeable. Further, an array of photovoltaic cells can be mounted to the exterior surface of the hull. The array of photovoltaic cells can be used to provide charge to the rechargeable batteries or provide power to the one or more systems in the submarine.  
         [0027]     In one embodiment, the submarine includes a receiver for receiving remote command signals to control operations of the submarine. Further, a transmitter can be provided for sending operational information to a remotely located receiver.  
         [0028]     Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]      FIG. 1  is an enlarged front top perspective view of an embodiment of an unmanned autonomous submarine according to the present invention having a plurality of hull sections according to one embodiment of the invention;  
         [0030]      FIG. 2  is a front and top perspective view of the unmanned autonomous submarine of  FIG. 1  having the hull sections assembled by a plurality of internal clasps;  
         [0031]      FIG. 3  is a front and top perspective view of the unmanned autonomous submarine of  FIG. 1  having the hull sections assembled by a plurality of external clasps;  
         [0032]      FIG. 4  is a side perspective view of a plurality of reinforcing rings for coupling the hull sections of  FIG. 1 ;  
         [0033]      FIG. 5  is schematic diagram of the reinforcing rings of  FIG. 4 ;  
         [0034]      FIG. 6  is a graphical view illustrating the depth and maximum tangential component of stress affecting the submarine of  FIG. 1 ;  
         [0035]      FIG. 7  is a schematic diagram of a pneumatic circuit for effecting the ascend and descend of the submarine of  FIG. 1  in a water environment;  
         [0036]      FIG. 8  is a schematic diagram of a first embodiment of a propulsion system of the submarine of  FIG. 1 ;  
         [0037]      FIG. 9  is an external perspective view of a front port of the propulsion system of  FIG. 8  formed in the forward hull section of the submarine of  FIG. 1 ;  
         [0038]      FIG. 10  is an internal perspective view of the front port of the propulsion system of  FIG. 8 , formed in the forward hull section of the submarine of  FIG. 1 ;  
         [0039]      FIG. 11  is an external perspective view of a rear port of the propulsion system of  FIG. 8 , formed in the aft hull section of the submarine of  FIG. 1 ;  
         [0040]      FIG. 12  is an internal perspective view of the rear port of the propulsion system of  FIG. 8 , formed in the aft hull section of the submarine of  FIG. 1 ;  
         [0041]      FIG. 13  is a top plan view illustrating the rudder, stabilizers and elevators of a maneuvering system of the submarine of  FIG. 1 ;  
         [0042]      FIG. 14  is a side view of the maneuvering system of the submarine of  FIG. 1 ;  
         [0043]      FIG. 15  is a front and top perspective view of the maneuvering system of the submarine of  FIG. 1 ;  
         [0044]      FIG. 16  is a front and top perspective view of one of the side elevators of the maneuvering system of  FIGS. 13-15 ;  
         [0045]      FIG. 17  is a cross-sectional view of the hydrofoil of  FIG. 16  illustrating the flow of water about the elevator;  
         [0046]     FIGS.  18 A-C are respective side views of the aft hull section illustrating various maneuvering positions of the elevators of the submarine of  FIG. 1 ;  
         [0047]      FIG. 19  is a side view of the aft hull section having a thrust vector system for steering the submarine of  FIG. 1 ;  
         [0048]      FIG. 20  is a cross-sectional view of the aft hull section and thrust vector system of  FIG. 19 ;  
         [0049]      FIG. 21  is a top side perspective view of the thrust vector system of  FIGS. 19 and 20 ;  
         [0050]      FIG. 22  is a rear and top perspective view of the aft hull section and thrust vector system of  FIG. 19 ;  
         [0051]      FIG. 23  is a schematic diagram illustrating maneuvering the submarine of  FIG. 1  using the propulsion system and thrust vector system of  FIGS. 8-12  and  19 - 22 , respectively;  
         [0052]      FIG. 24  is a schematic diagram of an alternative embodiment of a propulsion system suitable for use in the submarine of  FIG. 1 ;  
         [0053]      FIG. 25  is a front top perspective view of the unmanned autonomous submarine of  FIG. 1  having a plurality of photovoltaic cells installed on the exterior surface of the hull; and  
         [0054]      FIG. 26  is a schematic diagram of a controller and sensor array for controlling the unmanned autonomous submarine of  FIG. 1 . 
     
    
       [0055]     To facilitate understanding of the invention, the same reference numerals have been used when appropriate, to designate the same or similar elements that are common to the figures. Further, unless stated otherwise, the drawings shown and discussed in the figures are not drawn to scale, but are shown for illustrative purposes only.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0056]     Reference will now be made to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings  FIGS. 1-26 . An exemplary embodiment of an unmanned autonomous submarine of the present invention is shown in  FIG. 1 , and is designated generally throughout by reference numeral  100 .  
         [0057]     Hull Configuration  
         [0058]     Referring to  FIGS. 1 and 2 , there is depicted in an enlarged view, with components separated for convenience of illustration, of a submarine hull  102  having a forward hull section  104 , a middle hull section  106 , and an aft ward hull section  108 . The preferred shape of the hull  102  is a slender axi-symmetric body of revolution, where the length is larger than the maximum diameter of the submarine. For example, in one embodiment, the hull  102  of the submarine is 1.645 m long, with a maximum outside diameter of 40 centimeters, although such dimensions are not considered limiting.  
         [0059]     Several alternative configurations of the hull (body)  102  of the submarine  100  are possible within the scope of the invention. The submarine  100  can be assembled from two, three, or more hull sections with appropriate sealing devices  120 . The most structurally efficient hull shape of the submarine is a circular cross-section. A hull  102  having a substantially circular cross-section is easy to fabricate and is streamlined for maximum drag reduction. The shape of the hull  102  is not limited to being circular, as other hull section shapes can be utilized to satisfy particular applications or purposes by the submarine  100 .  
         [0060]     In one embodiment as shown in  FIGS. 1 and 2 , the forward or nose section  104  is a hemisphere, and the aft or rear tail section  108  is a semi-ellipsoid of revolution. The hull sections  102  of the submarine can be fabricated by welding or otherwise fastening together sheet metal strips (e.g. 3 mm thick steel sheets). Alternatively, the hull sections can also be cast from any suitable material. For example, the hull sections  102  of the submarine can be made from steel, fiberglass, among other well known materials and/or a combination thereof which are capable of withstanding the water pressure when submersed at particular depths.  
         [0061]     In the embodiment shown in  FIGS. 1 and 2 , an opening  110  is formed in the upper side of one of the body sections (preferably the middle hull section  106 ) with a removable cover  112 . The opening  110  is provided for access to the cabin  140  during assembly and servicing of the submarine  100 . The removable cover  112  is provided to seal and protect the interior of cabin  140  of the submarine  100  from the external water environment. Additionally, as discussed in further detail with respect to  FIG. 2 , the opening  110  facilitates assembly of the hull sections  108  using internal clamps  116 . Further, although not shown in  FIGS. 1-3 , the hull  102  includes a number of fixed or rotatable lifting and steering surfaces preferably made from hydrofoils which provide stability and control (i.e., maneuverability) during operation of the submarine  100 , as is discussed below in further detail with respect to  FIGS. 13-19 .  
         [0062]     Referring to  FIGS. 2 and 3 , the hull sections  102  of the submarine  100  are shown assembled together and secured by internal or external clamps. Referring to  FIG. 2 , internal clamps  116  are preferably used, since they do not create any resistance to the submarine motion while submersed in the water and thus produce a smooth continuous surface. The open ends of the forward hull  104  and aft hull  108  sections include circular end ring portions  118  having a diameter substantially equal to the diameter of the middle hull section  106 , to thereby provide a continuous smooth exterior surface where the hull sections are secured together. All three hull sections are joined together within the interior of the submarine by suitable fasteners  116 , such as with spring clamps  116  for quick and easy assembly, or a number of bolt/nut combinations.  
         [0063]     In an embodiment implementing a bolt/nut combination, a plurality of bolts are provided on one ring (e.g., on rings  120  formed on opposing ends of the middle hull section  106 ), and each bolt is inserted through thick washers welded to the same ring  120 . The bolts are threaded into mating nuts welded to a second mating ring, for example, circular end rings  118  formed on the forward and aft hull sections. An O-ring  130  is located between each two mating parts of the hull sections  102  in order to provide sealing power against water leakage. The bolts and internal clamps  116  are accessed during assembly through the central body opening  110 .  
         [0064]     Referring to  FIG. 3 , in an alternative embodiment, the submarine body  102  is assembled by using external clamps  122 . The external clamps  122  are provide easy assembly of the hull sections  102 .  
         [0065]     Referring to  FIGS. 4 and 5 , the three hull sections  104 ,  106  and  108  are joined together and assembled using O-rings  130 , such as rubber O-rings  132  for providing a watertight seal between the joined hull sections lO 2 . The O-rings  130  can optionally include steel reinforcement rings  134  to form a combined steel and rubber reinforcing/coupling O-ring. The steel/rubber O-rings serve as couplers between the hull sections, as well as stiffeners because they increase the rigidity and integrity of the body of the submarine against wrinkling and deformation.  
         [0066]     Referring to the graph  600  of  FIG. 6 , the relationship between the outside pressure at a certain depth and the maximum tangential component of stress affecting the inner radius of the cylindrical middle hull section  106  of the submarine&#39;s hull  102  is shown. Depths from 10 to 50 meters below sea level are considered. Typically, the weakest part of the submarine&#39;s hull  102  is the middle cylindrical hull section  106 , as the other elliptical hull sections  104  and  108  of the submarine&#39;s hull  102  are not subject to the same levels of radial and tangential stresses.  
         [0067]     The average value of axial stress affecting the body of the submarine (for example, a wall thickness of 3 mm) at a depth of 50 meters (corresponding to an external pressure of 5 bars), was observed to be equal to approximately 13.4 MPa (MegaPascals), while the internal cabin pressure in the submarine was approximately equal to 1 bar.  
         [0068]     The maximum value of the tangential stress affecting the submarine&#39;s cylindrical middle hull section  106  of the hull  102  can be found at the inner radius, and these values are much larger than those of the radial stresses affecting the submarine.  
         [0069]     Referring now to  FIG. 6 , it can be seen from the graph  600  that as the depth of the submarine increases, the tangential component of stress increases in compression. Comparing the stress to the yield strength (210 MPa) of steel (SAE 1020) used in building the hull of the submarine, it was found that the submarine&#39;s hull  102  can handle external pressures of 32 bars (i.e., corresponding to depth of approximately 320 meters).  
         [0070]     Ballast System  
         [0071]     Referring again to  FIG. 1 , the cabin  140  of the submarine is pressurized with air all the time during operation in water. This pressurization is necessary for the proper functioning of the diving and floatation system (ballast system), especially during surfacing of the submarine. Due to the design of the ballast system  700 , low values of gage pressures are necessary (less than 5 bars). This low pressure is sufficient for the operation of the ballast system even for maximum design operating depths for the submarine  100  under water where pressures are much higher. Cabin pressurization can be provided by either an external air pressure source (e.g., an air compressor or a pressure cylinder), or by operating the submarine compressor (i.e., in the ballast tank system) for a predetermined time prior to the submarine being placed in the water (i.e., when the ballast tank is empty, air is sucked from the atmosphere to the cabin  140  through the ballast tank). This pressurization increases the submarine strength and joint resistance against water leakage into cabin  140 .  
         [0072]     Referring to  FIG. 7 , the diving and floatation (ballast) system  700  includes a ballast tank  702 , a reciprocating air compressor  714 , a plurality of solenoid valves  711  and  715 , at least one check valve  722 , and piping for transferring air between the compressor  714  and ballast tank  702 . In one embodiment, the ballast tank  702  is cylindrical in shape and is installed on the bottom of the inside wall in the middle cylindrical hull section  106  of the submarine  100 . In one embodiment, the tank  702  has a convex cover which causes air inside it to accumulate and go through the air outlet  708 . The tank  702  contains several partitions (baffles) which restrict the motion of water to prevent the water in the tank from destabilizing the submarine. The tank has a small opening  706  at its bottom for water to flow into or out of the tank  702 .  
         [0073]     In one embodiment as shown in  FIG. 7 , a sealed box, located above the ballast tank  702 , contains the reciprocating air compressor  714 . The compressor  714  removes air from the enclosed space around it through an opening in the box&#39;s wall. The removed air can come from the top of the ballast tank  702  through a one-way valve  708  and a water trap, and pumps it to cabin  140  when the submarine is submersing. The same compressor  714  can be used to pump air from the pressurized cabin  140  back to the ballast tank  702  in order to force water out of the tank during the surfacing operation. The solenoid valves are used to accomplish these two processes. The solenoid valves form part of the pneumatic circuit  700 , which control the air flow in a manner which will cause either diving or surfacing of the submarine.  
         [0074]     In particular, the submarine  100  is designed to be floating when initially placed in water. Referring to schematic diagram of  FIG. 7 , the ballast tank  702  is flooded with water through a water opening  706  in the bottom  704  of the tank  702  by sucking air from the tank through the tank&#39;s air outlet  708  (water trap). The air from the tank flows through port  710 , through port  712 , then through the compressor  714 , then through port  716 , and through port  718  into the cabin  140  of the submarine  100 . The air removed from the tank  702  is pressurized and stored in the cabin  140  of the submarine  100  for usage during a reverse operation to force the water out of the tank  702 . The removal of air from the tank  702  creates low pressure inside the tank&#39;s body  702 , which in turn causes water to flow therein, thereby enabling the submarine  100  to gain mass and submerge in the water.  
         [0075]     During the surfacing or ascending operations of the submarine  100 , the air compressor  714  is operated along with the actuation of the two solenoid valves  711  and  715 , such that air is removed from the cabin  140  through port  713 , port  712 , through the air compressor  714 , through port  716 , through port  717 , through a check valve (non return valve)  722 , and then through the tank&#39;s air inlet  724  into the tank&#39;s body  702 . This operation causes air to be pressurized back into the tank  702 , thus creating high pressure therein the tank, which in turn causes the discharge of water through the tank&#39;s water opening  706  to reduce the mass of the submarine and cause it to ascend and/or float.  
         [0076]     In order to provide enough air for the surfacing operation, the interior of the submarine&#39;s body (i.e., cabin  140 ) is pressurized with air before any operation is started. Another advantage of the pressurization with air is that this technique increases the sealing power and the resistance against water leakage into the submarine&#39;s cabin  140 .  
         [0077]     Propulsion System  
         [0078]     Referring to  FIGS. 8-12 , propulsion of the submarine  100  is provided by a propulsion system  800  having least one water pump  802 . The system  800  provides forward motion to the submarine by sucking water from a first opening or port  804  in the forward hull section  104 , and pumping water from a second opening or port  806  formed in the tail hull section  108  of the submarine. The emerging jet would provide the force needed for the submarine to move.  
         [0079]     In one embodiment, a DC-motor-operated water pump  802 , located inside the submarine, sucks water from a front opening  804  in the nose  104  of the submarine via a first pipe  810  and ejects it from another opening in the far end of the tail  108  via a second pipe  812 .  
         [0080]     Stopping the submarine (while in forward motion) and giving it a backward motion is achieved using the same system as in described above but with a reverse water flow. This can be done by several means: (a) connecting another identical pump with the first pump back to back and operating the second pump only for the backward motion; (b) using a flow reversal water circuit with solenoid valves and pipe connections; or (c) having a parallel system to the first one but with a reversed flow direction.  
         [0081]     Referring to the embodiment of  FIG. 8 , the propulsion system  800  includes two pumps  814  and  816  that are used to provide forward and backward motion of the submarine  100 . In order for the submarine  100  to move in the forward direction, the first pump  814  is activated to suck water from the front water opening  804  via pipe  810  and pump the water through the second pump  816  and out of the rear water opening  806  via pipe  812 , which provides sufficient thrust for the submarine  100  to move in the forward direction. To propel the submarine in the reverse direction, the second pump  816  is activated to suck water from the rear water opening  806  through the first pump  814  via pipe  812 , and out of the front water opening  804  via pipe  810 . This reverse operation provides the submarine  100  with sufficient thrust to reduce and stop the forward motion, and then propel the submarine  100  in the reverse direction.  
         [0082]     Maneuvering System  
         [0083]     Referring to  FIGS. 13-15 , maneuvering of the submarine  100  is achieved by the use of a plurality of stabilizing fins  1302 , elevators  1304 , a rudder  1306 , and by water jet thrust vectoring, as described below in further detail. A pair of horizontal stabilizing fins  1302  is attached to opposing sides of the middle hull section  106 , and act as stabilizers to prevent the submarine  100  against rolling. In one embodiment, the fixed stabilizers  1302  are fixedly welded to the body of the submarine and do not move.  
         [0084]     A pair of rear elevator fins  1304  is rotatably attached to opposing sides of the aft hull section  108 . The rear elevator fms  1304  assist with maneuvering the submarine and controlling its motion, as well as providing depth stability to the submarine. The rudder  1306  is vertically attached to the aft hull section  108  of the submarine. The rudder  1306  is responsible for steering the submarine  100  in a sideways direction (e.g., left and right). One skilled in the art will appreciate that the forward horizontal pair of stabilizing fins  1302  can also be rotatably attached to the sides of the middle hull section  106  to provide additional maneuverability.  
         [0085]     The installation of the rotatable hydrofoil fms  1302 ,  1304  and rudder  1306  creates three weak points which are susceptible to water leakage. Leakage problems at these points are solved using special sealing units. These seals provide a resilient, watertight opening for enabling the rotational motion of the hydrofoil fins and rudder in addition to preventing water leakage.  
         [0086]     Referring to  FIGS. 13-17 , the elevators  1304 , stabilizing fins  1302 , and rudder  1306  are formed, for example, by symmetric hydrofoil sections in order to reduce drag and enable the submarine to ascend (float) and submerge (dive) in the water environment during operation. Referring to  FIG. 17 , a circular shaft  1702  is provided at one end of the hydrofoil for attachment to a motorized gear box (not shown) for rotating the hydrofoil, as required.  
         [0087]     In one embodiment, the elevators  1304  and rudder  1306  are actuated by two DC motors; one for the elevators and the other for the rudder. In order to rotate the rudder  1306 , the motor is linked to the rudder via a friction disk. The disk is attached to a small shaft that is fixed to the rudder itself. The elevators are actuated by the second DC motor. In order to actuate both elevators at the same time, a power screw is linked to the motor. A nut near the other end of the power screw is then attached to a link which connects the elevators  1304 . Preferably, the elevators  1304  can move between −45 and +45 degrees as illustratively shown in FIGS.  18 A-C, although such range of movement is not considered limiting.  
         [0088]     Referring to  FIGS. 19 and 20 , in one embodiment, a thrust vectoring mechanism  1900  is installed proximate the second port  806  of the propulsion system which is provided at the rear hull section  108 . The thrust vectoring mechanism  1900  is provided to operate along with the rudder  1306  to assist with steering of the submarine  100 .  
         [0089]     Referring to  FIGS. 21 and 22 , the thrust vectoring mechanism  1900  includes a link member  1902  that moves a vertical circular plate  1904 , which is installed inside the rear port  806  of the propulsion system. The link  1902  is moved and actuated by the rudder  1306  with minimal motion delay. The small plate  1904  controls the angle at which the water jet leaves the rear port  806  of the submarine  100 , which causes the submarine  100  to change its direction of motion.  
         [0090]     Referring to  FIG. 23 , there are three possible directions for the water jet to leave the rear port  806  of the submarine  100 . If the water jet exits the rear port  806  along direction  2302 , then the submarine is propelled to the right. If the water jet exits the rear port  806  along direction  2304 , then the submarine is propelled in a straightforward path. Alternatively, if the water jet exits the rear port  806  along direction  2306 , then the submarine is propelled to the left.  
         [0091]      FIG. 24  illustrates another embodiment for supporting (or replacing) the rudder  1306  in steering the submarine  100 . In particular, two parallel pumps  2402  are provided, illustratively in the rear hull  108  to propel and steer the submarine  100 , instead of using only one pump as described above with respect to the embodiment of  FIGS. 8-12  and  23 . A third forward pump  2404  is located in the forward hull section  104 . The third forward pump  2404  is activated when stopping the submarine or backward motion is desired.  
         [0092]     In particular, the forward pump  2404  is connected between the front opening  804  formed in the forward hull section  104  and a Y-connection  2406  that is coupled to a pair of main pipes  2408 , which transfer water from the front opening  804  to the rear parallel pumps  2404 . Each of the pair of pumps  2404  is coupled by a conduit  2412  to a corresponding rear port  2410  formed at the aft hull section  108 .  
         [0093]     As shown in  FIG. 24 , water enters the submarine  100  from the front opening  804  and into the Y-connection  2406  which splits the flow into two parts delivered to two parallel pumps  2402 . The parallel pumps  2402  operate to force water out of the submarine through two rear ports  2410  to propel the submarine in a forward straight direction. Steering of the submarine can be effected by operating one of the parallel pumps  2402  while shutting down the other, which causes the water jet from the corresponding rear port  2410  to change the direction of the submarine  100 . One advantage of the parallel pump propulsion system  2400  of  FIG. 24  is that the thrust vectoring mechanism  1900  is not required, thereby eliminating any possible damage to the links  1902  and  1904  caused by unknown objects (e.g., rocks), which might occur while moving underwater.  
         [0094]     In an alternative embodiment, the submarine steering system includes two openings in the tail of the submarine separated by an appropriate distance and on both sides of the first central opening. The two emerging water jets are not parallel but they meet at a point downstream from the tail end of the submarine. Allowing more water to flow in one of these side openings than the other will cause the submarine to turn right or left as desired. One or two water pumps can be used for this configuration.  
         [0095]     In the one-pump system, the output of the pump is branched into two pipes to the two openings in the back of the submarine. The flow rate of water in each branch can be controlled via throttling valves. Alternatively, in the two-pump system, two identical water-jet pump systems are installed parallel to each other. The nose of the submarine can have either a common opening or two openings. The flow rate in each branch can be controlled by the voltage supplied to each pump, or alternatively by throttling one branch for a short time to cause a turning moment on the submarine.  
         [0096]     Control and Power Systems  
         [0097]     Referring to  FIG. 26 , an illustrative controller  2600  is provided to control the submarine  100  such that it is completely autonomous. The controller  2600  includes a microprocessor  2602 , support circuitry  2604 , memory  2606  a plurality of sensors  2608  and one or more bus lines (conductors) for providing electrical signals therebetween. In one embodiment, a (Motorola 68HC11A8) microcontroller is chosen to serve as the main control unit of the submarine. The microcontroller utilizes programs and routines stored in memory  2606  to control the submarine and translate the electrical signals from the various sensors  1608  into electrical signals delivered to the various actuators of the submarine&#39;s systems.  
         [0098]     The microcontroller  2602  can be programmed with special programs that enable the submarine  100  to perform various special tasks. The programs can set certain trajectories for the submarine to follow during its motion. For example, the microcontroller  2602  can be programmed to guide the submarine  100  around a docked ship and inspect the submerged part of its hull. The microcontroller  2602  can also be programmed to direct the submarine  100  to cruise while submerged in the water to search for one or more objects and then surface after finding the object. During its operation, the sensors  2608  enable the submarine to detect obstacles and decide for itself whether to stop, pull back or change its direction of motion to avoid collision.  
         [0099]     The support circuitry  2604  can include power supplies, logic circuitry, cache, I/O circuitry, among other conventional support circuits. The memory  2606  can be cache memory, RAM, ROM, programmable memory, and can be apart from and/or integrated with the microcontroller  2602 .  
         [0100]     The plurality of sensors  2608  are used to sense the environment and the physical properties surrounding the submarine  100 , such as the surrounding water pressure, and to convert these quantities into electrical signals that can be used by the control media of the submarine  100  to decide a sequence of operation according to the inputs.  
         [0101]     The sensors  2608  that can be used and installed in the submarine can include SONAR sensors, used for obstacle detection and for scanning the seabed; a pressure transducer, used for depth measurement; speed measurement sensors; as well as a GPS system, to keep track of the submarine&#39;s location; an attitude sensor which keeps track of the direction of motion.  
         [0102]     In addition, a video camera and audio equipment can be attached to the submarine  100  to transmit images and sounds to the operator at the surface. The video camera can further be used for control purposes by linking it to the controller  2600  of the submarine, and using some image processing principles.  
         [0103]     Further, the submarine can be programmed to perform more specialized tasks by installing additional special links and equipment, such as a manipulator (robotic) arm, which can be used for gathering samples for research and for retrieval of sunken objects; laser sensors for detecting faults and cracks in underwater structures like dams, bases of oil rigs, and underwater pipes and cables; special equipment for detecting faults in submerged parts of ship hulls at seaports; underwater welding equipment, among other specialized devices and equipment suitable for underwater operations.  
         [0104]     In order to increase the reliability of the submarine, a remote control (RC) system  2612  is installed in the submarine  100 . The remote control system  2612  includes at least a receiver, and preferably a transmitter and receiver (transceiver)  2614  that enables the operator to override one or more programs of the controller  2260  to take full control of the submarine, for example, in the case of emergency situations.  
         [0105]     The receiver  2614  of the RC system  2612  is installed inside the submarine  100  with an insulated antenna  2616  sticking out of the hull  102 . Furthermore, the antenna  2616  can be linked to a floating antenna by a reeling wire in order to guarantee that the signal transmission can not be interrupted as the submarine dives deeper and deeper due to the dispersion of electromagnetic waves in water.  
         [0106]     Source of Power:  
         [0107]     In one embodiment, the submarine includes a plurality of batteries as the main power source of the submarine. In one embodiment, the batteries include a set of several 12-Volt sealed lead acid rechargeable batteries. These batteries can provide enough power for the systems of the submarine for reasonably long missions. If more power is needed for lengthy missions, special Lithium batteries can be used which can provide more power for such missions.  
         [0108]     Referring to  FIG. 25 , in one embodiment, photovoltaic cells  2502  are provided to recharge the batteries during the floating period of the submarine  100 , and thus make the submarine more independent for long missions. The photovoltaic cells  2502  are used in a sealed panel that cover the top surface of middle hull section  106  of the submarine. Additional photovoltaic cells  2502  can be installed on the forward and aft hull sections  104  and  106  as well. The photovoltaic cells  2502  can charge the batteries or run the various power components in the submarine during daytime when the sun is shining even when it is diving at shallow depths.  
         [0109]     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.