Abstract:
A technique for controlling the pitch of a supercavitating projectile is disclosed. For example, the illustrative embodiment controls the pitch of a supercavitating projectile by shifting its center of gravity. The center of gravity of the projectile is shifted by moving a ferromagnetic mass inside the projectile forward or backward, depending on the desired pitch. In some embodiments of the present invention, the position of the ferromagnetic mass is directed by a controller that has a predetermined trajectory stored in its memory.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to underwater projectiles in general, and, more particularly, to supercavitating projectiles. 
       BACKGROUND OF THE INVENTION 
       [0002]    A supercavitating underwater projectile can achieve speeds of 150 knots, and, therefore, it is especially useful in naval applications. A supercavitating underwater projectile achieves these speeds because it comprises a blunt nose known as a “cavitator.” As the projectile travels through the water, the cavitator contacts the water in such a way as to create many small air bubbles. The small air bubbles then coalesce into one big air bubble that is large enough to completely encompass the projectile. The effect is that the projectile is traveling inside a giant air bubble. 
       SUMMARY OF THE INVENTION 
       [0003]    Controlling the trajectory of supercavitating projectiles is a challenging task because supercavitating projectiles travel inside a gaseous bubble underwater, and, therefore, the conventional mechanism for controlling projectiles in air and projectiles in water are often unsatisfactory. Therefore a need exists for a simple and dependable way for controlling the trajectory of a supercavitating projectile as it travels. 
         [0004]    The present invention provides a technique for controlling the pitch of a supercavitating projectile without some of the costs and disadvantages for doing so in the prior art. For example, the illustrative embodiment controls the pitch of a supercavitating projectile by shifting its center of gravity. The center of gravity of the projectile is shifted by moving a ferromagnetic mass inside the projectile forward or backward, depending on the desired pitch. In some embodiments of the present invention, the position of the ferromagnetic mass is directed by a controller that has a predetermined trajectory stored in its memory. 
         [0005]    The illustrative embodiment has a roll axis and comprises: a ferromagnetic mass that has a center of gravity on the roll axis; a first spring connected to the ferromagnetic mass; and a first magnet for displacing the ferromagnetic mass along the roll axis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  depicts a schematic drawing of the salient components of supercavitating underwater projectile  100  in accordance with the illustrative embodiment of the present invention. 
           [0007]      FIG. 2  depicts a schematic diagram of the salient components of supercavitating underwater projectile  100  as it travels in direction  201  that is different from its longitudinal roll axis  108  (i.e., supercavitating underwater projectile  100  is pitching up). 
           [0008]      FIG. 3  depicts a schematic diagram of the salient components of supercavitating underwater projectile  100  as it travels in direction  201  that is different from its longitudinal roll axis  108  (i.e., supercavitating underwater projectile  100  is pitching down). 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  depicts a schematic drawing of the salient components of supercavitating underwater projectile  100  in accordance with the illustrative embodiment of the present invention. Supercavitating underwater projectile  100  comprises: projectile body  101 , ferromagnetic mass  102 , springs  103 - 1  and  103 - 2 , backstops  104 - 1  and  104 - 2 , magnets  105 - 1  and  105 - 2 , sensor  106 , controller  107 , and longitudinal roll axis  108 . 
         [0010]    Projectile body  101  is a non-explosive, propelled object, such as a bullet, for imparting kinetic energy to a target (not shown). It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which projectile body  101  is an explosive object. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which projectile body  101  is a self-propelled object, such as a missile, rocket, or torpedo. 
         [0011]    Ferromagnetic mass  102  is an iron block that is connected to springs  103 - 1  and  103 - 2 . The movement of ferromagnetic mass  102  is constrained so that it can only move between backstops  104 - 1  and  104 - 2 . At each position between backstops  104 - 1  and  104 - 2 , the center of mass of ferromagnetic mass  102  is on longitudinal roll axis  108 . It will be clear to those skilled in the art how to make and use ferromagnetic mass  102 . 
         [0012]    In accordance with the illustrative embodiment, ferromagnetic mass  102  is centered on longitudinal roll axis  108 , but it would be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which ferromagnetic mass  102  is positioned elsewhere inside projectile body  101 . Although ferromagnetic mass  102  has one degree of freedom of movement, it would be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which ferromagnetic mass  102  has any number of degrees of freedom of movement. 
         [0013]    Spring  103 - 1  is a helical spring between backstop  104 - 1  and ferromagnetic mass  102 . The restoring force of spring  103 - 1  is co-linear with longitudinal roll axis  108 . Spring  103 - 2  is a helical spring between backstop  104 - 2  and ferromagnetic mass  102 . The restoring force of spring  103 - 2  is co-linear with longitudinal roll axis  108 . 
         [0014]    Although springs  103 - 1  and  103 - 2  are helical, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which one or both of springs  103 - 1  and  103 - 2  are another type of spring, such as for example and without limitation, a leaf-spring, a volute spring, etc. In accordance with the illustrative embodiment, each of springs  103 - 1  and  103 - 2  are a single spring, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which one or both of springs  103 - 1  and  103 - 2  comprises a plurality of springs or function in parallel with a damper (e.g., hydraulic piston, etc.). 
         [0015]    In accordance with the illustrative embodiment, springs  103 - 1  and  103 - 2  are identical, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which springs  103 - 1  and  103 - 2  are different (e.g., have different spring stiffness coefficients, are made of different materials, etc.). 
         [0016]    Magnet  105 - 1  is an electromagnetic that generates an attractive magnetic force on ferromagnetic mass  102 . The direction of the magnetic force is co-linear with the longitudinal roll axis  108 , and the magnitude of the force varies under the direction of controller  107 . Magnet  105 - 2  is an electromagnetic that generates an attractive magnetic force on ferromagnetic mass  102 . The direction of the magnetic force is also co-linear with the longitudinal roll axis  108 , and the magnitude of the force also varies under the direction of controller  107 . 
         [0017]    Sensor  106  is a device for measuring the speed of projectile  101  and conveying an indication of that speed to controller  107 . In accordance with the illustrative embodiment sensor  101  measures the speed of projectile  100 , however it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which sensor  106  senses another physical characteristic such as for example and without limitation, acceleration, pitch, yaw, tilt, roll, temperature, humidity, radiation, etc. Although, the illustrative embodiment comprises only one sensor, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which multiple sensors are used. 
         [0018]    Controller  107  is a processor that receives input from sensor  106  and generates signals to direct magnet  105 - 1  and  105 - 2 . In particular, controller  107  controls magnets  105 - 1  and  105 - 2  to move ferromagnetic mass  102 , which alters the center of gravity of projectile  100 , to achieve a desired pitch. It will be clear to those skilled in the art, after reading this disclosure, how to make and use controller  107  to control magnets  105 - 1  and  105 - 2 . 
         [0019]      FIG. 2  depicts a schematic diagram of the salient components of supercavitating underwater projectile  100  as it travels in direction  201  that is different from its longitudinal roll axis  108  (i.e., supercavitating underwater projectile  100  is pitching up). In this case, controller  107  has directed magnet  105 - 1  to move ferromagnetic mass  102  forward to restore the longitudinal roll axis to the direction of travel. 
         [0020]      FIG. 3  depicts a schematic diagram of the salient components of supercavitating underwater projectile  100  as it travels in direction  201  that is different from its longitudinal roll axis  108  (i.e., supercavitating underwater projectile  100  is pitching down). In this case, controller  107  has directed magnet  105 - 2  to move ferromagnetic mass  102  aft to restore the longitudinal roll axis to the direction of travel.