Abstract:
A helical field device that accelerates an object to high velocity by converting rotational kinetic energy in the device into linear kinetic energy in the object, and alternatively, that decelerates objects from high velocity by converting the linear kinetic energy in the object into rotational kinetic energy in the device. The device transfers kinetic energy between the device and an object through the use of a localized high pressure field in the form of a helix having a variable pitch along the length of the device, which couples the object to the device without the pressure field itself significantly contributing energy into the system. Instead, the energy that is used to accelerate the object comes from the kinetic energy imparted to the device by an outside source, such as an engine, or a potential energy storage device.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/514,487, filed Oct. 24, 2003, the entire contents of which are herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates in general to a device that accelerates an object or a fluid, and in particular to a device that accelerates an object to high velocity by a helical force field that converts rotational kinetic energy in the device into linear kinetic energy in the object or fluid, and alternatively, that decelerates an object or a fluid from high velocity to low velocity by converting the linear kinetic energy into rotational kinetic energy. 
   2. Description of the Related Art 
   There are many different types of accelerating devices. For example, a railgun is a device in which electrical current is made to flow cross-wise through a conductive projectile, causing the projectile to become magnetized. Because magnetic fields and electrical current are repelled by each other, and because this repulsive force always acts in a direction perpendicular to the flow of the electrical current, the projectile is made to accelerate forward in response to this current flow. 
   Because railguns are powered by electricity, they require heavy and complex systems to store this electrical energy, and to produce and condition their huge electrical power pulses. For example, the University of Texas Center for Electromagnetics is creating an experimental rail gun for the US Marines that will accelerate a 2 kg projectile to 2.5 km/s. The railgun requires a power system that produces a 30 GigaWatt electrical pulse, stores hundreds of megajoules of energy, and weighs many tens of tons. 
   Railguns operate at extreme current densities. As a comparison, a resistance welder, which uses electrical current to melt and weld material, operates at a fraction of the current density of typical high energy railgun. The high current density required by railguns causes extreme wear on the rail and barrel, and as a result, practical railguns can achieve projectile velocities of no more than about 2.5 km/s. Railguns that do reach greater velocities are typically single-shot, or nearly single-shot. 
   In a railgun, the accelerating magnetic field is produced by what is essentially a single-turn coil. Generating the required high magnetic-flux density using such a coil requires an extremely high current density, combined with a relatively low voltage. However, concerns over the maximum current carrying capacity of the conductors typically limit a railgun&#39;s magnetic flux density to approximately 5 Tesla, which in turn limits a railgun&#39;s accelerating force. 
   Railguns use an arc of plasma to make the electrical contact between the projectile and the rails. Therefore, it is essential that this plasma arc accelerates at the same rate as the projectile. However, with existing railgun technology, it is not possible to control the plasma arc in a repeatable manner when operating at very high velocities and power densities. As a result, the plasma arc typically either lags behind the projectile, or passes it, further limiting the efficiency and maximum velocity that a railgun can attain. 
   In a coilgun, also known as a “mass driver”, or “co-axial accelerator”, a projectile is made to pass through a series of electromagnetic coils, or solenoids. These solenoids are precisely controlled to turn on, or become magnetic, as the projectile is approaching, and to turn off the instant the projectile passes, allowing the projectile to be pulled forward by the next solenoid in the series. 
   The magnetic pressure that is applied to an object by a solenoid decreases with the square of the distance between the object and the solenoid&#39;s center. Therefore, to get the maximum efficiency out of a coilgun, the projectile must be allowed to approach as closely as possible to the center of each soil (solenoid) before the coil is turned off. However, if the projectile is allowed to pass through the center of the coil before the coil is completely turned off, the magnetic force that was previously accelerating the projectile will now be pulling it back, causing the projectile to slightly decelerate. As the ultimate velocity of the projectile increases, the turn-off time of each coil must decrease for the efficiency of the accelerator to be maintained. However, it is a fundamental characteristic of magnetic coils to create self-generated magnetic fields, which act to keep the coils partially energized (and thus partially magnetized) even when there is no current flowing to them. This characteristic of magnetic coils makes it very difficult to turn them off quickly enough. As a result, the efficiency of the coilgun decreases rapidly with increasing projectile velocity, and coilguns that operate at practical energy density levels are even more limited in their velocity than railguns. 
   In a conventional (explosive) gun, expanding gas from a chemical explosion pressurized the inside of a barrel behind the projectile. Because the projectile forms a sliding seal between itself and the barrel, it is accelerated by the pressurized gas behind it. 
   Due to gas dynamics limitations, a chemical-explosive gun cannot accelerate a projectile to a velocity that exceeds the blastwave velocity of the explosive being used. The highest blastwave velocity attainable with a chemical explosive is 2 km/sec. Therefore, even if provided with an infinitely long barrel, a conventional gun cannot accelerate a projectile beyond 2 km/s. Furthermore, the tremendous amounts of ammunition that would be required to operate a conventional gun for extended periods at high rates of fire would make it highly impractical for applications involving continuous operation, such as cutting or drilling. 
   A light gas gun uses a chemical explosive to produce the energy used to accelerate the projectile. However, a light gas gun circumvents the blastwave velocity limitations of a conventional gun by using its explosive to first accelerate a specific volume of low density gas, or “light gas”, such as hydrogen, which is held in a series of stages behind the projectile. Upon discharge, a sliding piston, driven by the expanding gas from the conventional explosion, compresses the lower density gas in front of it, creating a second blastwave. However, unlike the relatively massive byproducts that make up the conventional explosive&#39;s blastwave, the lower mass of the “light” gas allows it to be driven to a much higher velocity by the same amount of energy. As a result, projectiles fired from light gas guns can reach velocities of 8 km/s or more. 
   Each shot of a light gas gun requires extensive manual preparation. For example, they typically use an exploding metal valve between each stage, which must be replaced after each shot, making continuous firing impractical. Furthermore, because barrel length and piston mass increase rapidly with projectile mass and velocity, light gas guns do not scale well to larger sizes. This characteristic limits the use of light gas guns to highly specialized research applications, within controlled laboratory environments. 
   SUMMARY OF THE INVENTION 
   The inventor of the present invention has recognized these and other problems associated with conventional accelerating devices, and has developed a cost-effective and energy efficient device for accelerating (and decelerating) an object are extremely high speeds. 
   In one embodiment of the invention, a helical field accelerator comprises one or more rotating members having outer surfaces in close proximity of each other; and a conduit disposed on the outer surface of one of the rotating members in the form of a helix, the conduit having a fluid disposed therein, wherein the conduit is influenced by the other one of the rotating members to transmit rotational kinetic energy of the one or more rotating members to a projectile disposed within the conduit, thereby converting rotational kinetic energy of the rotating members to linear kinetic energy of the projectile. 
   In another embodiment of the invention, a device comprises a first magnetic structure in close proximity to a second magnetic structure that produces a localized magnetic field having a variable pitch, wherein rotational kinetic energy of the magnetic structures is converted into linear kinetic energy in an object. 
   In yet another embodiment of the invention, an accelerator for accelerating an object comprises a plurality of structures, one of said plurality of structures comprising at least one rotating structure that interacts with another one of said plurality of structures to produce a helical field upon an object to cause the object to accelerate along said plurality of structures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  shows a plan view of a structure for producing a localized pressure field is arranged in a helical, or spiral, pattern having a constant pitch. 
       FIG. 2  shows a plan view of a structure for producing a localized pressure field is arranged in a helical, or spiral, pattern having a variable pitch. 
       FIG. 3  shows a plan view of the structure of  FIG. 2  mounted in proximity to one or more similar structures. 
       FIG. 4  shows a plan view of the structure of  FIG. 2  mounted in proximity to one or more linearly arranged structures. 
       FIG. 5   a  shows a plan view of the structure of  FIG. 3  mounted in proximity to one or more similar structures when both structures are rotating in the same direction. 
       FIG. 5   b  shows a plan view of the structure of  FIG. 4  mounted in proximity to one or more linearly arranged structures when one of the structures is rotating. 
       FIG. 6  shows a perspective view of a helical fluid-pressure accelerator in the form of two parallel, elongated cylinders. 
       FIG. 7  shows a perspective view of the helical fluid-pressure accelerator of  FIG. 6  with a conduit disposed on one of the cylinders. 
       FIG. 8  shows an end view of alternate embodiment of the helical fluid-pressure accelerator of  FIG. 6  having multiple cylinders rotating about a single cylinder. 
       FIG. 9  shows an end view of another alternate embodiment of the helical fluid-pressure accelerator of  FIG. 6  having multiple conduits on one cylinder. 
       FIG. 10  shows a perspective view of the helical fluid-pressure accelerator of  FIG. 6  with an alternate embodiment of the conduit disposed within a groove of one of the cylinders. 
       FIG. 11  shows a cross-sectional view of a conduit according to an embodiment of the invention. 
       FIG. 12  shows a cross-sectional view of a method of attaching a conduit to one of the rotating cylinders according to the invention. 
       FIG. 13  shows a cross-sectional view of a method of disposing a conduit within a groove in one of the rotating cylinders according to the invention 
       FIG. 14  shows a fluid-pressure accelerator with a plurality of rotating cams according to an alternate embodiment of the invention. 
       FIG. 15  shows a fluid-pressure accelerator with a plurality of rams according to yet another alternate embodiment of the invention. 
       FIGS. 16   a  and  16   b  show a cross-sectional view of an alternative embodiment of a rigid conduit according to the invention in an open, unsealed position and a closed, sealed position. 
       FIGS. 17   a  and  17   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having two rotating helical magnetic structures or cylinders according to an embodiment of the invention. 
       FIGS. 18   a  and  18   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having one rotating helical magnetic structure and one linear magnetic structure according to an alternate embodiment of the invention. 
       FIGS. 19   a  and  19   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having one rotating helical magnetic structure and two linear magnetic structures according to an another alternate embodiment of the invention. 
       FIGS. 20   a  and  20   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having one rotating helical magnetic structure and three linear magnetic structures according to yet another alternate embodiment of the invention. 
       FIGS. 21   a  and  21   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having two rotating helical magnetic structures and one linear magnetic structure according to still yet another alternate embodiment of the invention. 
       FIGS. 22   a  and  22   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having one rotating helical magnetic structure and a rotating linear magnetic structure according to still yet another alternate embodiment of the invention. 
       FIGS. 23   a  and  23   b  show a side view and a front view, respectively, of a magnetic-pressure accelerator having two concentric rotating helical magnetic structures according to still yet another alternate embodiment of the invention. 
       FIGS. 24   a  and  24   b  show a side view and an end view, respectively, of a magnetic-pressure accelerator having two concentric rotating helical magnetic structures surrounded by a magnetic field according to yet another alternate embodiment of the invention. 
       FIGS. 25   a  and  25   b  show a side view and an end view, respectively, of a magnetic-pressure accelerator having two concentric rotating helical magnetic structures surrounded by a magnetic field according to still yet another alternate embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The principles of the invention will now be described. In general, a helically configured structure  1 , or an array of structures capable of producing a localized pressure field is arranged in a helical, or spiral, pattern, is shown in  FIG. 1 . A helically configured structure  2 , in which the pitch of this helix, or the distance that a point on the helix will advance in one rotation, is made to vary from relatively low at its beginning, to relatively high at its end, is shown in  FIG. 2 . 
   Referring now to  FIG. 2 , when one such helically configured structure  2  is mounted in proximity to one or more similar structures  2 , or alternatively, when one such helically configured structure  2  is mounted in proximity to one or more linearly arranged structures  3  ( FIG. 4 ), regions of high pressure are formed at the point or points  4  (designated by the ‘X’) where the structures  2  are nearest each other. 
   When the helically configured structure or structures  2  are made to rotate relative to each other (indicated by the arrows in  FIG. 5   a ), the regions of high pressure travel along the structures  2  in a direction substantially parallel to the axes of rotation, A, effectively forming a series of traveling pressure waves  5 . Similarly, when the helically configured structure  2  is made to rotate relative to linearly arranged structure  3  (indicated by the arrow in  FIG. 5   b ), the regions of high pressure travel along the structures  2 ,  3  in a direction substantially parallel to the axes of rotation, A, effectively forming a series of traveling pressure waves  5 . 
   The pressure waves travel down the structures  2 ,  3  at a rate that is related to the pitch of the helix at any particular point. In a region of the helix where the pitch is lower than 1:1, or less than 45°, the speed of the traveling pressure wave will be some fraction of the rotational surface-speed of that point on the helix. In a region of the helix where the pitch is higher that 1:1, or greater than 45°, the speed of the traveling wave will be some multiple of the rotational surface-speed of that point on the helix. Thus, assuming a constant speed of rotation, in a region of low helix pitch, the pressure wave moves slowly; in a region of high pitch, the pressure wave travels more rapidly. 
   Because the pitch of the helix varies from relatively low at its beginning, to relatively high at its end, the resulting pressure waves travel relatively slowly at the beginning of the helix and progress down it at an ever increasing rate. When the final pitch ratio of the helix is very high, for example 50:1, extremely high pressure-wave velocities can be produced using relatively moderate rotational speeds. 
   When a pressure-responsive object is placed in or near one of these traveling pressure waves  5 , the object will be accelerated, or decelerated, depending on whether the pressure wave is traveling in the direction of increasing pitch, or decreasing pitch, along the helix. 
   In the case where the device is being used as an accelerator, this variation in the speed of the pressure waves allow the device to accelerate an object gradually, ensuring that the force holding it within the pressure wave is not exceeded. Furthermore, by matching the helix pitch and helix rotation speed to the mass of the object, the pressure wave can be made to accelerate the object at the highest rate that object&#39;s inertia will allow. This direct control that the device allows over the velocity of the pressure wave makes it possible to precisely match the acceleration rate of the pressure wave to the maximum possible acceleration rate of the object, ensuring that the pressure wave does not leave the object behind. 
   The above acceleration mechanism can employ a variety of pressure fields, including contact and non-contact fields. Examples of contact pressure fields include fluid pressure against a surface, and the pressure created by the direct mechanical contact between one surface and another. Examples of non-contact pressure fields include magnetic fields, and electrostatic fields. For the sake of convenience, however, the following device configurations will all contact pressure fields to be from fluid pressure, and all non-contact pressure fields to be from magnetic pressure. Among those configurations that employ fluid pressure, a distinction will be made between compressible and non-compressible fluids. 
   A Fluid-Pressure Accelerator 
   In general, in a helical accelerator that employs fluid pressure, the rotational kinetic energy in the device is transmitted to the projectile through the medium of a fluid, such as water, or the like, which acts as a buffer between the rotating members of the device and the projectile. This buffer fluid may be either a compressible or non-compressible fluid. 
   Referring now to  FIG. 6 , a helical accelerator  100  can take the form of two parallel, elongated cylinders  6  mounted in close proximity to each other. The cylinders  6  rotate axially on bearings  7 , and an engine or motor  8  is used to drive one or both of them either directly, or through a transmission  9 . It will be appreciated that the invention is not limited by the type of rotating means, and that the invention can be practiced with any desirable means for rotating the cylinders  6 . 
   Referring to  FIG. 7 , the helical accelerator  100  includes a conduit  10  having a cross-section of selectively reducible area and with a diameter significantly less than that of a driven cylinder  11 , is arranged in a helical or spiral pattern around the circumference of one of the cylinders  11 ,  12 . By definition, a conduit is a natural or artificial channel through which something, for example, a fluid, and the like, is conveyed. A conduit can be formed by an article of manufacture that is specifically designed for conveying a fluid, such as a hose, and the like. A conduit can also be formed two or more surfaces interacting with each other, such as, a channel formed by the space between an inside surface of an outer member and an outside surface of an inner member disposed within the outer member. For example, a conduit or channel can be formed between the space between a cylindrically-shaped inner member having a corkscrew-shaped raised surface on its outer surface and a cylindrically-shaped outer member having a relatively smooth inside surface. Other configurations for a conduit or channel are within the scope of the invention as is known to those skilled in the art. The helical pattern of the conduit  10  is such that its pitch, or the distance that a point on the helix will advance in one rotation, varies from relatively low at its beginning at one end, to relatively high at its other end. The diameter of the conduit  10 , or its height above the surface of the cylinder  11 , is such that when the conduit  10  is at the intersection point of the cylinders  11 ,  12 , it is forcibly compressed or pinched, thereby closing the conduit  10  to the passage of fluid. 
   The cylinders  11 ,  12  are driven rotationally in the direction of advancing helix pitch with the starting point of the helix being the end with the lowest pitch, and the final point of the helix being the end with the highest pitch. During rotation, the intersection of these two cylinders  11 ,  12  with the conduit  10  creates a traveling pinch-point (indicated by the ‘X’), which moves down the cylinders  11 ,  12  in the direction of increasing helical pitch. 
   When a controlled volume of fluid is introduced into the conduit  10  at the point of lowest pitch, this volume will be captured by and pushed ahead of this traveling pinch-point, thereby forcing the captured fluid to travel through the conduit at the same rate as this intersection point. Because the conduit  10  is arranged around the cylinder  11  in a helix of increasing pitch, the rate at which the pinch-point travels down the cylinder  11  increases accordingly, even though the rotation speed of the cylinders  11 ,  12  may be constant. 
   Referring now to  FIG. 8 , in an alternative embodiment of a fluid-pressure accelerator  100 , a fluid-pressure accelerator  110  increases the frequency of discharge by providing a plurality of cylinders  13  around a single cylinder  14  to which the conduit  15  is attached. As shown in  FIG. 9 , a similar effect can be achieved in another alternate embodiment of the fluid-pressure accelerator  100  by a fluid-pressure accelerator  120  that deploys a plurality of helical conduits  16  against a single cylinder  17 . Both of these approaches have the effect of increasing the net volume of fluid accelerated without requiring an increase in the cylinder&#39;s rotation speed. 
   The fluid may either be drawn into the conduit  10  under its own pumping action, or the fluid may be forcibly injected. In the case where a compressible fluid, or gas, is used, it may be desirable to introduce the gas into the conduit with an initial pressure, in a pre-compressed state. By pre-compressing the gas in this way, the accelerator is able to devote more of its length to the actual acceleration of the gas, rather than having to first compress it before bringing to bear the full accelerating force. This pre-compression may be accomplished either through the use of a separate pumping stage, or through a chemical reaction during injection, such as a chemical explosion. 
   In the case where a non-compressible fluid is used as the buffer fluid, it may be desirable to introduce the fluid into the conduit  10  with an initial velocity. Because the helical conduit would not have to accelerate the fluid from a standing start, this would allow a higher cylinder rotation speed and a correspondingly higher fluid exit velocity. 
   It should be noted that the friction between the fluid and the wall of the conduit  10  is proportional to surface area. It is therefore desirable to limit the volume of the buffer fluid in each uptake to only the amount needed to perform the work required by a particular application. As shown in  FIG. 10 , by limiting the length of each fluid element  18 , it is possible to minimize the energy lost between the fluid and the walls of the conduit  10  to friction losses. 
   The resulting pulsed characteristic of its operation distinguishes the device  100  from a conventional pump, where the intent is typically to produce continuous flow. As a result of its pulsed operation, the helical accelerator  100  is not subject to cavitation, in which a fluid is forced to separate into both its liquid and gas states. In a conventional continuous-flow pump, fluid is both drawn or “pulled” into the pump on the intake side, and expelled or “pushed” through the output side. It is during the intake stage that cavitation can occur, where the dramatic acceleration of the fluid subjects it to such low pressure that it partially vaporizes. Due to the resulting gas in the fluid stream, the pump now must act on a fluid which is elastic in nature. This elasticity limits the force that can be exerted on the fluid during the time it is within the pump, and therefore limits the acceleration that the fluid can undergo. In contrast, in the helical accelerator  100  of the invention, the primary acceleration of the fluid occurs while the fluid is under compression on the “push” side of the pump, which therefore makes cavitation impossible. This allows the device  100  to exert an extremely high accelerating force on the fluid. 
   One aspect of the device  100  is that no sliding contact occurs between the cylinders  11 ,  12  and the conduit  10  during compression. As a result, wear on the conduit  10  is minimized. 
   In one embodiment of the invention shown in  FIG. 11 , the conduit  10  may consist of an outer layer  19  of flexible high-tension material  19 , such as carbon fiber, Spectra fiber, or the like, and an inner lining  20  made from a flexible, heat resistant material, such as silicone, Teflon, or the like. 
   Referring to  FIG. 12 , a conduit  21  may be either situated on the outside of a driven cylinder  22 , or recessed within a helical grove or channel  23 , as shown in  FIG. 13  within a driven cylinder  24 . 
   As shown in  FIG. 12  where the conduit  21  is situated on the surface of the cylinder  22 , the conduit  21  can be affixed to the cylinder  22  in such a way so as to resist the shear force interaction between the conduit  22  and the compressing cylinder  27 . One method in which the conduit  21  can be affixed to the cylinder  22  as follows: The conduit  21  may be situated within a sling  25  of high tensile strength material, such as Kevlar, carbon fiber, Spectra fiber, or the like, so that the anchor point of the sling  26  is affixed to the driven cylinder  22  on the advancing side of the compressing roller  27 . Other ways of affixing the conduit  21  to the surface of the driven cylinder  22  may exist, and would work equally well in the device  100 . 
   As shown in  FIG. 13  where the conduit  21  is recessed within a groove  23  in the driven cylinder  24 , a raised feature  28  on the compressing cylinder  27  is synchronized to mesh within the groove  23 , by a means well-known in the art, such as through a gear train, by contact between the raised feature  28  and the sides of the groove  23 , or the like. Recessing the conduit  21  in this way allows the wall of the driven cylinder  24  to provide additional burst resistance to the conduit  21 . 
   In an alternate configuration of a device  100 ′ is shown in  FIG. 14 . In this configuration, the conduit  29  is fixed to a rigid linear member  30 , and a segmented cylinder  31 , which forms a continuous helical feature that is held against the conduit  29 . This helical feature may be comprised of a series of eccentric, freely rotating lobes or cams  31 , which sequentially come in contact with, and compress the conduit, thereby generating a traveling pinch-point. Because the conduit or channel can be formed by a space between two opposing surfaces, it is envisioned that the principles of the invention can be practiced by using an inner member having a helical feature, such as a raised peak, and the like, on its outer surface that is disposed within an outer member, such as a housing, and the like, having an inner surface opposing the outer surface of member. Such an arrangement is a three-dimension model of the principle of the invention shown in  FIG. 14 . In this three-dimensional model, the inner and outer members move relative to each other such that the helical feature generates a traveling pinch-point, thereby accelerating the fluid that is disposed within the conduit or channel formed by the inner and outer members. For example, the inner member may have an outer surface with a shape of a polygon, such as a Realeaux polygon, and the outer member may have an inside surface with a circular, an oblong, an oval shape, and the like. As in the other embodiments, the amount of acceleration can be selectively adjusted by varying the pitch of the helical feature. The pinch-point formed by the helical feature on the inner member interacting with the outer member may move linearly along the outer member as the inner and outer members move relative to each other. Alternatively, the pinch-point may move in a non-linear fashion, depending on the relative movement between the inner and outer member. It will be appreciated that the helical feature may be formed on the inside surface of the outer member, rather than on the inner member, and that the inner member may be relatively smooth, such as a cylinder, and the like. 
   Alternatively, this same effect may be achieved by the use of a series of pistons or rams  32  arranged linearly along the conduit  33 , which are actuated in a controlled sequence to produce the effect of a virtual helix, as shown in  FIG. 15 . These rams  32  may be powered by a chemical explosion, by hydraulic force, electrostatic force, magnetic force, or the like. 
   When a fluid pressure accelerator is used to directly accelerate an object traveling within the conduit, a rigid, non-elastomer conduit may be preferable, due to its ability to guide and stabilize the projectile within its walls. 
   One such method of implementing a rigid conduit  102  with a reducible cross section is shown in  FIG. 16   a  and  FIG. 16   b . A trough or channel  38  of rigid material, such a metal, or the like, is enclosed by a strip or roof  35  of flexible material. The strip  35  is made to be flexible along its longitudinal direction, while being inflexible across its span. The strip  35  is fitted into the trough  38  and retained by overhanging projections  36  to resist internal pressure. A sliding seal  37  exists between the sides of the strip  35  and the walls of the channel. The seal  37  may be created through close tolerances between the two members, or through the use of a separate seal. As shown in  FIG. 16   a , fluid is allowed to pass through the trough  34 . However, when the roof  35  of the conduit  102  is compressed ( FIG. 16   b ), the roof  35  slides to the bottom of the trough  34  and forms a seal with the floor of the trough  34 , thereby preventing fluid to pass therethrough. 
   It may be appreciated that the invention can be practiced with other methods for producing a rigid conduit with a reducible cross section, and can be employed by the device  100  with no change to its essential principle of operation. 
   Modes for Accelerating a Projectile 
   There are several methods through which the above device  100  can use the energy from a high velocity fluid stream to accelerate a projectile. Four methods are given below. 
   Buffer fluid pushing a projectile ahead of it: 
   In this mode, a projectile is injected into the conduit  10  with the buffer fluid, and is pushed forward by the buffer fluid. Here, both the buffer fluid and the projectile are accelerated, but it is only the kinetic energy imparted to the projectile that is of interest. 
   Buffer fluid directed against a projectile: 
   In this mode, the buffer fluid is accelerated and then directed against the projectile, so that the kinetic energy of the fluid is imparted to the projectile through a momentum transfer. 
   Buffer fluid pressurizing an enclosed chamber: 
   Here, a compressible fluid is explosively injected into an enclosed chamber such as a gun barrel, thereby raising the pressure within the chamber and expelling a projectile contained within. 
   Buffer fluid as the projectile: 
   In this mode, the device  100  behaves strictly as a pump, and the buffer fluid itself serves as the projectile. 
   In all of the above operation modes, the rotation of the cylinders  11 ,  12  may be of a constant speed, or of a pulsed or intermittent nature. When the device  100  is used as a pump, as in the last configuration, a constant speed of rotation may be preferable. However, when the device  100  is used to accelerate an object, as in the first three modes given above, an intermittent rotation which allows energy to be injected into the device  100  in a single pulse may be preferred. 
   An Internal Combustion Engine 
   It is a fundamental principle of the device  100  that if rotation can cause compression, then expansion can cause rotation. This characteristic of the device  100  allows it to function as an internal combustion engine. By introducing a second cylinder or roller into the device  100 , the conduit  10  may be closed in multiple locations simultaneously. This allows a gas and fuel mixture contained within it to be selectively compressed, ignited, and decompressed in a controlled sequence before exiting the device  100 . In this configuration, the cylinders are self-powered, and a transmission is used to extract torque from the device  100 . Unlike a reciprocating engine or a turbine engine, a helical internal combustion engine can operate efficiently at a very small scale due to its ability to provide arbitrarily long combustion cycles, regardless of the engine&#39;s scale. With reciprocating engines and turbine engines, the time available for combustion decreases as the engine&#39;s scale decreases. 
   A Magnetic-Pressure Accelerator 
   Referring now to  FIGS. 17   a  and  17   b , as with the fluid-pressure accelerator  100 , a magnetic pressure accelerator  200  can take the form of two parallel, elongated cylinders  39  mounted in close proximity to each other. The cylinders  39  rotate axially on bearings  40 , and an engine or motor (not shown) is used to drive one or both of them directly, or through a transmission. 
   A localized magnetic field  41  is generated at the surface of each cylinder  39  and is made to wrap around each cylinder  39  to form a helical or spiral pattern (helix). The pitch of this helix varies in a specific manner, from relatively low at its beginning at one end, to relatively high at its other end. When these cylinders are made to rotate in the same direction, the magnetic pressure wave that is produced by the convergence of their helical fields travels down the structures at a rate that is related to the pitch of the helixes at any particular point. In a region of low helix pitch, the pressure wave moves slowly; in a region of high pitch, the pressure wave travels more rapidly. Thus, given a fixed rotation speed, the magnetic pressure wave will move relatively slowly at the beginning of the helix and progress down it at an ever increasing rate. 
   Situated in the gap between the two cylinders  39  is a tube or similar containment structure  42  made of a rigid, magnetically transparent material, such as ceramic or the like. The structure  42  serves to guide and stabilize an object  43  being acted upon by the magnetic pressure wave. Alternatively, the helical magnetic cylinders  39  can be used by themselves to contain and stabilize the object  43 , thereby making a separate guide unnecessary. 
   In another alternate configuration of the device  200 , a device  210 , shown in  FIGS. 18   a  and  18   b , includes a single rotating helical magnetic structure  44  mounted in proximity to a stationary, linear magnetic structure  45 . The linear structure  45  acts as a track upon which an object  46  being accelerated is magnetically levitated to prevent mechanical contact. With this configuration, more than one linear structures  45  may be arranged around a single helical structure  44 , allowing multiple objects to be accelerated simultaneously. As with the preceding configuration, a tube or similar containment structure  47  made from a magnetically transparent material is located between the helical structure  44  and the linear structure  45  to guide and stabilize the object  46  being acted upon. Alternatively, the linear and helical magnetic structures  44 ,  45  themselves may be used to contain and stabilize the object  46 , making a separate guide unnecessary. 
   In a variation on the preceding configuration, a magnetic-pressure accelerator  220  includes two linear magnetic structures  48  may be used, rather than a one, effectively forming a magnetic “trough” for the projectile  49 , as shown in  FIGS. 19   a  and  19   b . These two linear structures  48  are angled so that their magnetic pressure counteracts the side-forces that are exerted on a projectile  49  by a helical magnet  50 , so that only the axial, or forward component of the force remains. 
   As a further modification to the device  200 , a magnetic-pressure acceleration  230  includes a third linear magnetic structure  51  is mounted on the opposite side of the helix to balance the side forces that are imposed on the helical structure by the lower magnetic structures, as shown in  FIGS. 20   a  and  20   b . Using this arrangement, side forces on the helix are greatly reduced, allowing for a lighter and less rigid helical structure. 
   As with the previous configuration, this configuration allows several magnetic structures  48 ,  51  to be arranged around a single rotating helix  50 , making it possible to accelerate multiple objects simultaneously. When this is the case, the side forces on the helix can be balanced by arranging these magnetic structures symmetrically around the helix, thereby making it unnecessary to use a separate magnetic structure specifically for this purpose. 
   Elements of the preceding configurations may be combined to form yet another configuration of a magnetic-pressure accelerator  240 , as shown in  FIGS. 21   a  and  21   b . In this arrangement, two helical magnetic structures  52  rotate in opposite directions, and a linear magnetic structure  53  is placed to one side of an object  54  being accelerated. As in the preceding configurations, this may function with or without the structure  53  to guide and stabilize the object  54 . 
   In yet another configuration of a magnetic-pressure accelerator  250 , as shown in  FIGS. 22   a  and  22   b , one or more linear magnetic structures  56  revolve around a single, stationary helical magnetic structure  55 . A containment structure  57 , in this case one that revolves with one of the linear magnetic structures  56  (as indicated by the dashed lines in  FIG. 22   b ), guides and stabilizes an object  58  being accelerated. Alternatively, the linear and helical magnetic structures  55 ,  56  themselves can be used to contain and stabilize the object  58 , making a separate guide unnecessary. 
   In still another possible configuration of a magnetic-pressure accelerator  260 , as shown in  FIGS. 23   a  and  23   b , one helical magnetic structure  59  is mounted concentrically within another helical magnetic  60  structure, and the two structures  59 ,  60  are driven in opposite directions relative to each other. Other iterations of this same configuration include a stationary inner structure with a revolving outer structure, and a stationary outer structure with a rotating inner structure. As with the preceding configurations, the object being accelerated  61  can be guided by a magnetically transparent tube  62  or similar containment structure located between the two magnetic structures. Alternatively, the magnetic structures  59 ,  60  themselves can be used to contain and stabilize the object, making a separate guide unnecessary. 
   In a variation on the preceding configuration, a magnetic-pressure accelerator  270  is shown in  FIGS. 24   a  and  24   b . In this configuration, the accelerator  270  is surrounded by a strong magnetic field  63 . In place of helical magnetic structures as in the previous embodiments, the cylinders  67  bear a magnetically shielding material, such as a super-conductive metal alloy or metal. Helical slots or perforations  64  through the shielding allow the ambient magnetic field  63  to pass through to the axis of the cylinders  67  at points corresponding to the slots  64  in the shields. When the cylinders  67  are made to rotate in opposite directions, these points of correspondence form regions of magnetic flux which move rapidly along the axis of the cylinders  67  along a traveling intersection between the slots  64  in the shields. A magnetically reactive object  68  placed at the axis of the cylinders  67  will therefore be accelerated along this traveling intersection. 
   As with the other configurations, this traveling-intersection effect can be achieved through the use of a helical feature  65  and linear feature  66  in a magnetic-pressure accelerator  280  as shown in  FIGS. 25   a  and  25   b , rather than through two helical cylinders  67  shown in  FIGS. 24   a  and  24   b.    
   Some, but not all, possible configurations of a helical magnetic structure used in combination with other helical or linear structures are described. Instead, this description refers to any configuration in which a helically-patterned magnetic field interacts with a magnetically responsive object in such a way that relative rotational motion between them causes the object to be either accelerated or decelerated. Additionally, this device is not limited to magnetic structures that are arranged on a cylinder, but can employ any structure which generates a helically-patterned magnetic field at the point of interaction with a magnetically responsive object, regardless of how the field is produced. For example, this device does not require the helical magnetic pattern to be geometrically continuous, but rather the pattern may be comprised of an array of multiple, discrete magnetic sources, such that the net effect upon the object is that of a helix. 
   Performance Parameters 
   The device of the invention has multiple applications, spanning a diverse range of fields, and each of these applications has its own optimal projectile characteristics. These characteristics primarily involve projectile mass, projectile velocity, and rate of fire. 
   Projectile mass and projectile velocity are determined by specific physical characteristics of the device itself, such as the helix surface speed (the speed at which every point on surface of the helix is traveling axially), the final helix pitch (the distance that a point on the helix advances during one rotation), and the length of the helix (the accelerating distance available). Other characteristics include the pressure field strength, or ‘flux density’, at the point of interaction with the projectile, and the size of the power source used to rotate the helix or other components. 
   As a result, the basic physical parameters of the accelerator can vary widely depending on its application. Indeed, one of the principle benefits of this device is its ability to be scaled up or down to virtually any power level. 
   Although specific requirements for each application will be addressed separately, they all share a general range of performance criteria, which allows for a generalized version of the device to be described in the following terms: 
   Projectile velocity: Most of the applications for this device require a projectile velocity in excess of 3 Km/sec, with some requiring velocities of up to 150 Km/sec or more. For comparison, the velocity of a typical rifle round is approximately 1 Km/sec, and the velocity of a satellite in low earth orbit is approximately 7 Km/sec. Materials research has demonstrated that a ‘universal damage criteria’ exists at an energy density of 10,000 Joules/cm 2 , and a projectile that is able to impart a net energy of 12,000 Joules to its target will vaporize one cubic centimeter of virtually any known material upon impact. Since many of the device&#39;s intended applications call for a complete removal of the target material, this velocity is used as a minimum benchmark for many of the projected versions. 
   Projectile mass: For most applications, the projectile will be traveling through air (as opposed to vacuum) during all, or part, of its flight. This requires that the projectile have a certain minimum mass to maintain its velocity through the air over the required distance. Therefore projectile mass ranges from milligrams for short range, low energy applications, to hundreds of kilograms or more for longer range and higher energy applications. 
   Surface speed: Due to the centrifugal forces involved, it is desirable to limit the surface speed of the helix and other rotating components to roughly 500 meters/sec (1.5 times the speed of sound) or less. However, it may be necessary to use higher surface speeds in certain applications. 
   Final helix pitch: Due to the above limitation on the surface speed of the rotating components, projectile velocity is largely determined by the final pitch of the helix. A helix pitch in the range of 7:1 (approximately 8°) is used in low velocity applications, and a pitch of up to 500:1 (approximately 0.11°) or greater is used in higher velocity applications. 
   Helix length: Since many applications require the device to be portable, a typical helix length might be in the range of 8 to 15 meters (25 to 50 ft). However, much shorter and much longer configurations can be produced for specific applications. 
   Magnetic flux density: The strength, or ‘flux density’, of the magnetic pressure wave determines the accelerating force that can be brought to bear on the projectile without the projectile breaking free from, and being left behind by, the traveling wave. For example, given a helix length of 8 meters, a flux density of 6.5 Tesla would be required to accelerate a 10 gram iron projectile to a velocity of 5,000 m/sec. This flux density is well within the range of existing resistive electromagnets and superconducting magnets. 
   Power source: Because this device uses rotational kinetic energy directly, without the need to first convert the energy into electrical form, it can be driven by a wide range of conventional power sources, including gas turbines, electric motors, and diesel engines. For example, a device that can accelerate a continuous stream of 10 g projectiles, at a rate of ten per second, to a velocity of 5,000 m/sec would require a power source of about 750 hp. A wide variety of power sources currently exist that are able to provide this level of output while still being suitably compact and inexpensive. 
   While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.