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Supercavitation
wikipedia.org
Supercavitation

Supercavitation is the use of cavitation effects to create a bubble of gas inside a liquid large enough to encompass an object travelling through the liquid, greatly reducing the skin friction drag on the object and enabling achievement of very high speeds. Current applications are mainly limited to projectiles or very fast torpedoes, and some propellers, but in principle the technique could be extended to include entire vehicles. This phenomenon can also be produced by the very fast strike of the appendages of the crustacean mantis shrimp Odontodactylus scyllarus, that uses it to attack and kill its prey.[1]
Physical principle

In water, cavitation occurs when water pressure is lowered below the water's vapour pressure, forming bubbles of vapour. That can happen when water is accelerated to high speeds as when turning a sharp corner around a moving piece of metal such as a ship's propeller or a pump's impeller. The greater the water depth (or pressure for a water pipe) at which the fluid acceleration occurs, the lesser the tendency for cavitation because of the greater difference between local pressure and vapour pressure. (The non-dimensional cavitation number is a measure of the tendency for vapour pressure bubbles to form in a liquid, calculated as the difference between local pressure and vapour pressure, divided by dynamic pressure.) Once the flow slows down again, the water vapour will generally be reabsorbed into the liquid water. That can be a problem for ship propellers if cavitation bubbles implode on the surface of the propeller, each applying a small force that is concentrated in both location and time, causing damage.
A common occurrence of water vapour bubbles is observed in a pan of boiling water. In that case the water pressure is not reduced, but rather, the vapour pressure of the water is increased by means of heating. If the heat source is sufficient, the bubbles will detach from the bottom of the pan and rise to the surface as steam. Otherwise if the pan is removed from the heat the bubbles will be reabsorbed into the water as it cools, possibly causing pitting or spalling on the bottom of the pan as the bubbles implode.
A supercavitating object is a high speed submerged object that is designed to initiate a cavitation bubble at the nose which (either naturally or augmented with internally generated gas) extends past the aft end of the object, substantially reducing the skin friction drag that would be present if the sides of the object were in contact with the liquid in which the object is submerged. A key feature of the supercavitating object is the nose, which may be shaped as a flat disk or cone, and may be articulated, but which likely has a sharp edge around the perimeter behind which the cavitation bubble forms.[2] The shape of the object aft of the nose will generally be slender in order to stay within the limited diameter of the cavitation bubble. If the bubble is of insufficient length to encompass the object, especially at slower speeds, the bubble can be enlarged and extended by injection of high pressure gas near the object's nose.[2]
The great speed required for supercavitation to work can be achieved temporarily by a projectile fired under water or by an airborne projectile impacting the water. Rocket propulsion can be used for sustained operation, with the possibility of tapping high pressure gas to route to the object's nose in order to enhance the cavitation bubble. An example of rocket propulsion is the Russian Shkval supercavitating torpedo.[3][4] In principle, maneuvering may be achieved by various means such as drag fins that project through the bubble into the surrounding liquid[5] (p. 22), by tilting the nose of the object, by injecting gas asymmetrically near the nose in order to distort the geometry of the cavity, by vectoring rocket thrust through gimbaling for a single nozzle, or by differential thrust for multiple nozzles.[2]
Applications

In 1960, the USSR started developing a project under the codename Squall run by NII-24 (Kiev) to develop a high-speed torpedo, an underwater rocket, four to five times faster than traditional torpedoes capable of combating enemy submarines. Several models of the device were made, the most successful – M-5 – was created by 1972. In 1972 to 1977, over 300 test launches were made (95% of them on Issyk Kul lake), by 29 November 1972 VA-111 Shkval was put into service with mass production started in 1978.
In 2004, German weapons manufacturer Diehl BGT Defence announced their own supercavitating torpedo, Barracuda, now officially named "Superkavitierender Unterwasserlaufkörper" or "supercavitating underwater running body" (English translation). According to Diehl, it reaches more than 400 kilometres per hour (250 mph).[6]
In 1994, the US Navy began developing a sea mine clearance system invented by C Tech Defense Corporation, known as RAMICS (Rapid Airborne Mine Clearance System), based on a supercavitating projectile stable in both air and water. These have been produced in 12.7 millimeters (0.50 in), 20 millimetres (0.79 in), and 30 millimetres (1.2 in) diameters.[7] The terminal ballistic design of the projectile allowed it to cause explosive destruction of sea mines as deep as 45 meters (148 ft) underwater with a single round.[8] In 2000, these projectiles were used to successfully destroy a range of live underwater mines when fired from a hovering Sea Cobra gunship at Aberdeen Proving Grounds. RAMICS is currently[when?] undergoing development by Northrop Grumman for introduction into the fleet. The darts of German (Heckler & Koch P11) and Russian underwater firearms,[9] and other similar weapons are also supercavitating.
In 2005, DARPA announced the 'Underwater Express program', a research and evaluation bid to establish the potential of supercavitation. The program's ultimate goal is a new class of underwater craft for littoral missions that can transport small groups of Navy personnel or specialized military cargo at speeds up to 100 knots. The contracts were awarded to Northrop Grumman and General Dynamics Electric Boat in late 2006.[citation needed] In 2009, DARPA announced progress via a new class of submarine.
The submarine's designer, Electric Boat, is working on a one-quarter scale model for sea trials off the coast of Rhode Island. If the trials are successful, Electric Boat will begin production on a full scale 100-foot submarine. Currently, the Navy's fastest submarine can only travel at 25 to 30 knots while submerged. But if everything goes according to plan, the Underwater Express will speed along at 100 knots, allowing the delivery of men and materiel faster than ever."[10]
Iran claimed to have successfully tested its first supercavitation torpedo on 2 April and 3 April 2006. Some sources have speculated it is based on the Russian VA-111 Shkval supercavitation torpedo, which travels at the same speed.[11] Russian Foreign Minister Sergei Lavrov denied supplying Iran with the technology.[12] Iran called this weapon the Hoot (Whale).
A prototype named the Ghost, designed for stealth operations by Gregory Sancoff of Juliet Marine Systems, uses supercavitation to propel itself atop two struts with sharpened edges. The vessel rides smoothly in choppy water and has reached speeds of 29 knots.[13]
Artist rendering of a supercavitating propeller in action
The supercavitating propeller is a variant of a propeller for propulsion in water, where supercavitation is actively employed to gain increased speed by reducing friction. They are being used for military purposes and for high performance boat racing vessels as well as model boat racing. The supercavitating propeller operates submerged with the entire diameter of the blade below the water line. Its blades are wedge-shaped to force cavitation on the whole forward face, starting at the leading edge, in order to reduce water skin friction. As the cavity collapses well behind the blade, the supercavitating propeller avoids the spalling damage due to cavitation that is a problem with conventional propellers.
Alleged applications
The Kursk submarine accident was rumored to have been due to a faulty Shkval torpedo,[14] though later evidence points to a faulty 65-76 torpedo - see Kursk submarine disaster.
References

Ashley, Steven (May 2001). "Warp Drive Underwater". Scientific American: 70–79.
 http://www.articlesextra.com/supercavitation-torpedoes.htm
 http://www.periscope.ucg.com/mdb-smpl/weapons/minetorp/torpedo/w0004768.shtml#pictures
 http://www.aem.umn.edu/research/supercavitation/documents/thesis_eric.pdf
http://www.popsci.com/military-aviation-amp-space/article/2009-07/darpa-readies-ultra-fast-mini-sub [2] [3] [4] [5]
Caroline Winter (2014-08-21). "This Stealth Attack Boat May Be Too Innovative for the Pentagon". Bloomberg BusinessWeek.
Gertz, Bill (August 23, 2001). "Russian book sheds light on missile". Washington Times. p. A.4.
Office of Naval Research (2004, June 14). Mechanics and energy conversion: high-speed (supercavitating) undersea weaponry (D&I).
http://www.onr.navy.mil/
Savchenko Y. N. (n.d.). CAV 2001 - Forth Annual Symposium on Cavitation - California Institute of Technology Retrieved April 9, 2006, from
http://cav2001.library.caltech.edu/159/00/Savchenko.pdf
Hargrove, J. (2003). Supercavitation and aerospace technology in the development of high-speed underwater vehicles. In 42nd AIAA Aerospace Sciences Meeting and Exhibit. Texas A&M University.
Kirschner et al. (2001, October) Supercavitation research and development. Undersea Defense Technologies
Miller, D. (1995). Supercavitation: going to war in a bubble. Jane's Intelligence Review. Retrieved Apr 14, 2006, from http://www.janes.com/
Graham-Rowe, & Duncan. (2000). Faster than a speeding bullet. NewScientist, 167(2248), 26-30.
Tulin, M. P. (1963). Supercavitating flows - small perturbation theory. Laurel, Md, Hydronautics Inc.
External links
Supercavitation Research Group at the University of Minnesota
 http://cav.safl.umn.edu/
Diehl BGT Defence's "Barracuda" - a German supercavitating Torpedo
 http://www.diehl-bgt-defence.de/index.php?id=550&L=1
DARPA Underwater Express Program
 http://www.darpa.mil/sto/solicitations/underwaterexpress/
   
Global Security.org on Supercavitation
http://www.globalsecurity.org/military/systems/ship/systems/hsuw.htm
  
How to Build a Supercavitating Weapon, Scientific American
 http://www.sciam.com/article.cfm?id=how-to-build-a-supercavit&ref=sciam

http://www.tldm.org/News22/RussiasShkvalRocketTorpedoIs3To4TimesFasterThanAnythingElse.htm
Russia's Shkval Rocket Torpedo is 3 to 4 Times Faster than Anything Else...



Shkval Supercavitating Torpedo

 


Deagel.com reported on August 18, 2013:
The Shkval, 'Squall' in English, is a nuclear-capable underwater anti-ship missile designed for use by nuclear-powered submarines against large surface ships such as aircraft carriers. It comprises a rocket-assisted propeller, which allows a top speed of 220 mph and a maximum range of 6 nautical miles, and a torpedo warhead. The super-cavitating Shkval is considered silent and fast, up to 3-to-4 times over existing torpedoes. The underwater rocket produces a high-pressure stream of bubbles from its nose and skin, which coats the torpedo in a thin layer of gas and forms a local envelope of super-cavitating bubbles achieving low drag. It is not clear whether the lack of a guidance system or, if exists, how it works. Due to its unique characteristics, Shkval is deemed as one of the most advanced naval weapon systems currently deployed worldwide. The torpedo is assembled at the Dastan Torpedo Plant in Kyrgyzstan.
In addition to the Russian Navy, the Shkval rocket-assisted torpedo has been sold to India, Iran and Ukraine. In 2008 it was said that Iran may use the Shkval underwater rocket to target the US Navy's aircraft carriers in the Persian Gulf. According to some reports they may use small fast boats as launch platforms. Russia claims that Ukraine sold five brand-new Shkval underwater missiles to Georgia prior to August 2008 conflict. Its development started in times of the Soviet Union and was completed by Russia after 2000. This missile system has been pointed out as the source of the fatal accident that shrunken the Russian Navy's Kursk nuclear-powered boat in August 2000. Apparently, the missile was undergoing tests aboard the doomed submarine.

http://nosint.blogspot.com/2014/05/commander-iran-one-of-only-two-world.html



http://conpaper.tistory.com/21406
(Supercavitation)  Shanghai to San Francisco in 100 minutes by 'Chinese supersonic submarine'




https://www.flickr.com/photos/wil5oncle7us/8621120631/?rb=1
Chinese Super-Cavitating Torpedo
( Beijing Military Museum )



Marc Wilson : A Simple Interactive Program to Design Supercavitating Propeller Blades

[ PDF ]
Patents
HYDRODYNAMIC SUPER-CAVITATION APPARATUS
 US2014119155

A hydrodynamic supercavitation apparatus includes: a body having one side connected to a fluid supply line for supplying fluid and a section decreasing space portion whose cross sectional area is gradually decreased formed at the inside thereof, the section decreasing space portion having a large space portion formed on one side thereof in such a manner as to communicate with the fluid supply line and a small space portion formed on the other side thereof; an outlet cap coupled to one end of the body and having a first section increasing space portion formed on one side of the interior thereof in such a manner as to communicate with the small space portion of the body and a second section increasing space portion formed on the other side of the interior thereof in such a manner as to be gradually increased from a smaller cross sectional area than the first section increasing space portion toward a larger cross sectional area than the first section increasing space portion; a closing cap coupled to the other end of the body so as to close the other end of the body; and a center bar supportedly coupled to the closing cap on one end thereof and passed through the interior of the body in such a manner as to be extended to the second section increasing space portion of the outlet cap.

UNDERWATER MOVING BODY
 KR101353410

The present invention, comprising of a moving body; a disk-shaped cavity generator which is formed at the distal end of the moving body and a pairing unit which is formed adjacent to the rear of the cavity generator, provides an underwater vehicle. The invention enables high-speed traveling by allowing supercavitation to be extended to the rear of the moving body and provides an advantageous effect which enables a traveling direction to be easily changed in a supercavitation state.



Piecewise linear method for analyzing supercavitation navigation body kinetic characteristics
 CN103558009

A piecewise linear method for analyzing supercavitation navigation body kinetic characteristics includes the steps that step1, a supercavitation navigation body kinetic model is built; step2, piecewise linear fitting is performed on a non-linear sliding force function in the supercavitation navigation body kinetic model to obtain a linear sliding force function; step3, parameters of the supercavitation kinetic model are set; step4, the supercavitation kinetic model with the piecewise linear sliding force Fp function is adopted for obtaining a sole balance point of a supercavitation navigation body, linearization is performed on a system at the balance point to obtain a jacobian matrix of the system and a characteristic equation at the balance point, characteristic values of the system are obtained, and the balance point of the system is judged to be an unstable saddle focus. By the adoption of the piecewise linearization of the sliding force function, the supercavitation navigation body kinetic model is simplified, so that the balance point position and stability conditions of the model have concise analytical expressions, and the supercavitation navigation body kinetic characteristics are analyzed more conveniently.

UNDERWATER MOVING OBJECT USING SUPERCAVITATION
 WO2013187674

The present invention relates to a super-cavitating underwater movable object which moves while being partially dipped into water; which utilizes a supercavitaion phenomenon; and which includes a high-temperature unit capable of being heated in order to form a gaseous film caused by a Leidenfrost effect between the front end portion protruding from the water surface and water touching the surface of the front end portion and an energy supply system which supplies energy to the high-temperature unit to be heated.

Supercavitation generating device of restrained experiment
 CN203259327

The utility model discloses a supercavitation generating device of a restrained experiment. An organic glass inspection window is arranged on the back of a water tank; a through groove is arranged in and two oppositely-arranged Z-type guide rails are arranged on the center of the water tank in a length direction; a load-bearing slide block and the guide rails form a sliding pair; one end of a connecting rod is connected with the load-bearing slide block and the other end equipped with an experimental model stretches into the experimental water tank; one end of a steel wire is connected with the load-bearing slide block and the other end is connected with a hoisting wheel in a dragging device; two sliding strips are respectively arranged on the two guide rails near one side of the dragging device, and one end of each of the sliding strips and the corresponding guide rail form a revolute pair via a rotating shaft; an adjusting bolt is arranged on one side face of each of the two guide rails; two pressure sensors are respectively arranged on the two guide rails; a high-speed camera and a lamp are arranged in front of the window; and the high-speed camera is connected with an industrial personal computer. By using the high-speed camera to record a generating process and a developing process of the supercavitation around the experimental model, the supercavitation generating device of the restrained experiment provides precise and stable experimental speed in a certain range for different models.



HIGH SPEED SURFACE CRAFT AND SUBMERSIBLE VEHICLE
 US8683937

A submersible vessel comprising: an elongated hull; at least one propeller mounted on a forward end of said hull and adapted to move said hull through water; said at least one propeller being of a size and configuration such that when it is rotated at an appropriate speed, it generates supercavitated water flowing from said at least one propeller and thence along an outer surface of said hull so as to diminish friction on the outer surface of said hull and facilitate high underwater speeds.

Plane supercavitation generation device
 CN202255830

The utility model discloses a plane supercavitation generation device. A water tank is arranged on a lower bottom plate; an organic glass window plate and a steel plate are arranged at front and rear same positions of the water tank; guide grooves and a long through groove which is communicated with the water tank are formed on the steel plate; a trolley is arranged between two guide grooves; one end of the trolley is connected with a spring; a firing trigger fixed on upright posts pulls the other end of the trolley; when the firing trigger is opened, a moving object connected with the trolley do high speed movement underwater; a high speed camera and an illuminating lamp are arranged outside one side of the organic glass window plate of the water tank; and the high speed camera is connected with an industrial personal computer. The water tank limits the development of supercavitation generated by the object due to high speed movement in the thickness direction of the water tank, so that a two-dimensional supercavitation shape is formed; the shape development characteristic of cavitation formed around the object when the object does high speed movement close to a liquid surface can be clearly observed by a high speed photography technology; the trolley device can ensure the linearity of object movement; and objects which have different head shapes and do high speed movement can be replaced to complete experimental data.



PROPELLER FOR SHIP
 US4789306

PURPOSE: To enhance the efficiency at low speeds without degrading the supercavitating section performance at high speed by providing hybrid blades in which cavitation is not caused in the radially inner section of each blade and supercavitation is caused in the radially outer section thereof. CONSTITUTION: In the body 11 of a plurality of propeller blades 10 supported by a hub 12, the sharp edge 38 functions as the front edge during rotation, and the edge 40 functions as the rear edge; and arc-shaped suction and pressurization side surfaces 24, 26 are formed so that the cavitation is not caused in the radially inner section 18 at the time of high speed rotation. Further, arc-shaped suction and pressurization side surfaces 34, 36 are formed so that the radially outer section 28 causes supercavitation. In other words, supercavitation is caused in each blade 10 at high speed, however, in addition to the outer section 28 where subcavitation is caused at low speed, the inner subcavitation section 18 is provided. Thus, the operation under the subcavitation of both sections in each propeller blade is enabled without impairing the function of the supercavitation sections at high speed, so that the efficiency at low speed can be improved.



SUPERCAVITATION PROPELLER AND ITS MANUFACTURE
 JPH08198182

PURPOSE: To provide high propeller efficiency by improving the front edge form of a propeller wing in a supercavitation propeller. CONSTITUTION: In a propeller wing 1, the cross-sectional form of its front edge section is provided with a cut surface 11 linking a point P on a virtual extending surface 12 to the front of a back surface 4 with the front edge 0 of a face 2 and a printed end formed by the front edge of the face 2 and the cut surface 11. Thus, since a negative pressure distribution on the wing back surface is almost the same as that in the case of a wing front edge having a pointed tip, propeller efficiency is improved and the strength of the wing front edge against impacts is increased because of a thickness (to formed in the wing front edge.


[ Coanda Effect ]

Structure for control of super-cavitation in guide blade turbine of hydraulic turbine
 CN2888113

The utility model relates to a supercavitation flow control mechanism inside of the hydraulic turbine guide vane. Separate head, middle and tail air supplying chambers are produced inside of the guide vane and three chambers are configured on a layer to form an air supplying chamber layer to divide the interior of the guide vane into a ventilating layer and a guide vane air supplying layer; the three air supplying chambers communicate with the outside air supplying device through air supplying holes; a guide vane clearance boss is provided at the bottom of the guide vane air supplying holes layer; and on the concave of the boss, several clearance air supplying holes are produced at the corresponding positions of the head, middle and tail air supplying chambers for communicating with the relative chamber. Through supplying air for the three chambers separately, the pressure and flux of each air supplying hole is regulated and the clearance flow of the guide vane end plane is stopped so as to solve the problem of vane damage due to the supercavitation.



Supercavitation gas-liquid multi-phase water spray propeller
 CN1911729

The present invention is one kind of water-jetting propulsion system utilizing supercavitation in realizing vapor-liquid two phase propulsion. The water-jetting propulsion system consists of a water uptake chamber, a supercavitation impeller, an impeller chamber, a kinetic energy converter and a shafting. The supercavitation impeller with vanes designed based on Tulin supercavitating foil principle can operate normally under cavitation and supercavitation condition. Both the vapor phase and the liquid phase in the back of the impeller are converted in the kinetic energy converter before being jetted via the thruster to produce thrust in the outlet of the thruster. The kinetic energy converter can guide the flow of both the vapor phase and the liquid phase and convert the rotation kinetic energy of both the vapor phase and the liquid phase in the outlet of the impeller into axial flow kinetic energy without increasing the pressure of the two phase flow. The present invention realizes great power thrusting under cavitation condition.



SUPERCAVITATION WEAPONS LAUNCHER
 WO2008105930

A projectile launch opening is submersed in water, a projectile ejector ejects the projectile from the projectile launch opening, and a gaseous cavity ejector ejects a gas to form a gaseous launch cavity covering the launch opening, synchronized with the projectile ejection, such that a leading surface of the projectile initially impacts the water at an inner surface of the gaseous launch cavity spaced above the launch opening, at an impact velocity initiating a supercavitation, the supercavitation substantially encapsulating the entire projectile within the water.



FLEET PROTECTION ATTACK CRAFT
 US8408155

A marine vessel comprising: a command module; first and second buoyant tubular foils; and first and second struts for connecting the first and second buoyant tubular foils to the command module, respectively; wherein the first and second buoyant tubular foils provide substantially all of the buoyancy required for the marine vessel; and wherein the marine vessel further comprises first and second engines enclosed within the first and second buoyant tubular foils, respectively, and first and second propulsion units connected to the first and second engines, respectively, for moving the marine vessel through the water.

Telescoping cavitator
 US7966936

A high speed underwater projectile configuration that includes a cylindrical telescoping cavitator design capable of providing projectile nose shape change where such change to the projectile nose tip geometry results in supercavitation and a concomitant vaporous cavity in the water that reduces projectile drag resistance while maximizing projectile range and where the projectile nose tip further includes a retractable cavitator piston feature. The projectile nose is designed to house a cylindrical cavitator piston that protrudes forward from the projectile and is held in place until launch. Velocity induced hydrodynamic forces on the forward face of this cavitator piston cause the piston to start moving aft and to gradually cause the piston to retract into the projectile nose, until a larger, secondary cavitator is exposed to the vaporous cavity.




Supercavitating Water-Entry Projectile
 US7779759

A water-entry projectile capable of supercavitation and spin-stabilization comprises a forward section having one or more forward stepped sections, each stepped section being symmetrical in rotation about an axis and having a radius at an aft end that is different from a radius of a front end of an adjacent rearwardly located stepped section; an aft section having an aft stepped section, the aft stepped section being symmetrical in rotation about the axis and having a maximum radius larger than a maximum radius of the forward section; and wherein the aft section is located substantially aft of a center of gravity of the projectile.
   


Supercavitation generator for boat
 CN201235909

The utility model discloses a supercavity generator for ships, which is composed of an air compressor and air transmission and exhaust pipes, wherein the air transmission and exhaust pipes are distributed along keel lines outside a ship body, and air exhaust holes are evenly distributed on both sides of each air transmission and exhaust pipe; the air compressor is positioned in a cabin and is communicated with the air transmission and exhaust pipes, and pressure-air is driven into the air transmission and exhaust pipes distributed along the keel lines outside the ship body by the air compressor; and when the air pressure is higher than the water pressure, the air is exhausted from the air exhaust holes arranged on both sides of each air transmission and exhaust pipe, and the exhausted air acted by the water pressure forms a layer of air membrane between a ship bottom and water so as to reduce the friction between the water and the ship body, thus the ships provided with the supercavity generator can be faster driven with the same power.



AERATOR DEVICE AND METHOD
 US3846516

An aerator device and method of aerating which comprises a hollow-bladed axial impeller means to effect supercavitation below the surface of the liquid and to produce a downward, swirling flow of gas and liquid; means for admitting a flow of gas to and through a first venturi and out through the blades of the propeller; wall means surrounding said blade means for cooperatively forming therewith an effective second venturi adjacent the blades; and means for preventing gas having passed the blades from reentering the blade area before being dissolved in the liquid.



Supercavitation ventilation control system
 US6684801

A supercavitation ventilation control system is disclosed and includes a vehicle body having a fore end and an aft end. A cavitator is fit to the fore end of the vehicle body, the cavitator generating a gas cavity around the vehicle body. A cavity control ring is slidably positioned at the aft end of the vehicle body, the cavity control ring selectively adjusting a terminal end of the cavity formed by the cavitator. A stop ring is adjustably positioned on the vehicle body forward of the cavity control ring for managing a reentrant jet generated by the cavity control ring. Each of the stop ring and cavity control ring are moveable by separate actuators and a single control system.



Method and apparatus for propelling a surface ship through water
 US6725797

A method and apparatus for propelling a surface vehicle through the water comprised of a submerged portion, including both a stern propulsion unit and a bow propulsion unit. Either unit may be a pumpjet, the bow unit may include a counter-rotating nose hub having attached spirally wound, twin centrifugal propeller blades. The foremost bow propeller is dedicated to stealth and the next-in-line bow propeller is dedicated to supercavitation. Specially-designed vortex loops that connect the pressure side to the intake side of a propulsion unit may be included in the blades, shroud or hub areas. Further, slightly diverged jet exhaust and variable special surface texturing reduce surface friction drag on the vehicle body.; The submarine propulsion system is used to power a surface vessel, supported by two or more hydrofoils which combine a submerged midcraft foil with a wave-piercing variety. The surface craft has the capability of submerging and maneuvering.

Bow mounted system and method for jet-propelling a submarine or torpedo through water
 US6701862

A jet propulsion system for a submersible vehicle, such as a submarine includes a propulsion unit mounted away from the stem of the submersible. Generally, the propulsion system consists of a set of blades secured to a hub within a shroud. Combining such a propulsion system with a surface texture treatment greatly reduces overall drag while improving the submersible's efficiency. Further, such an arrangement contributes to the submersibles stealthy characteristics. An additional hub and set of high-speed blades capable of generating a supercavity may be added to achieve supercavitation. The propulsion system can be varied to include a pumpjet and/or a centrifugal force blade system.



Projectile with tail-mounted gas generator assembly
 US7373883

A projectile is provided that includes a body having a front tip portion and a rear end portion. A combustion chamber base plate is operatively arranged with the rear end portion of the body and defines a combustion chamber. At least one radial discharge aperture is partially defined by the combustion chamber base plate and is arranged in fluid communication with the combustion chamber. A gas generated by igniting a combustible material is discharged through the at least one radial discharge aperture. The discharged gas impinges against a wall of a cavity formed by the moving projectile to form a reactive force that stabilizes the projectile thereby reducing the occurrence of tail-slap.