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Title:
VEHICLE PROPULSION AND PROTECTION SYSTEM
Document Type and Number:
WIPO Patent Application WO/2011/083330
Kind Code:
A2
Abstract:
A propulsive and/or protective system for a craft having an outer skin comprising: an array of resistive or superconducting electromagnets or permanent magnets disposed in operable proximity to the skin; an activation and control sub-system for activating the electromagnets and controlling the activation sequence of electromagnets; and dynamic magnetically responsive material responsive to dynamic field patterns, in operable proximity to the array of electromagnets and to a fluid or surface in or upon which the craft is disposed, whereby the craft is propel-able by activating the electromagnets in concert or in via passage of electric current through the magnetically responsive material. In certain embodiments the system solely provides a protective implementation.

Inventors:
YONG, Matthew (171 Jalan 5/45, Petaling Jaya, Selangor, 46000, MY)
Application Number:
GB2011/050012
Publication Date:
July 14, 2011
Filing Date:
January 06, 2011
Export Citation:
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Assignee:
YONG, Matthew (171 Jalan 5/45, Petaling Jaya, Selangor, 46000, MY)
International Classes:
F41H5/04; B60L13/10; B62D57/04; F41H5/007
Attorney, Agent or Firm:
APPLEYARD LEES (15 Clare Road, Halifax West, Yorkshire HX1 2HY, GB)
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Claims:
CLAIMS

1. A propulsion system for a craft having an outer skin comprising:

an array of resistive or superconducting electromagnets disposed in operable proximity to the skin;

an activation and control sub-system for activating the electromagnets and controlling the activation sequence of electromagnets; and

dynamic magnetically responsive material responsive to dynamic field patterns, in operable proximity to the array of electromagnets, whereby the craft is propel-able by activating the electromagnets in concert with such activation being arranged to propel the craft.

2. The system of claim 1 , wherein the craft is disposed upon or in a surface.

3. The system of any preceding claim, wherein the dynamic magnetically responsive material includes particles.

4. The system of any preceding claim, wherein the dynamic magnetically responsive material is a movable fluid. 5. The system of any preceding claim, wherein the dynamic magnetically responsive material comprises a magnetic pseudo-fluid.

6. The system of any preceding claim, wherein the dynamic magnetically responsive material is responsive over a substantial portion of the wetted surface of the craft.

7. The system of claim 5, wherein the magnetic pseudo-fluid is a ferrofluid.

8. The system of claim 5, wherein the magnetic pseudo-fluid is a magneto- rheological fluid.

9. The system as claimed in any preceding claim further comprising a protection system wherein the activation and control sub-system is adapted to arrange the dynamic magnetically responsive material in relation to an incoming threat.

10. The system of any preceding claim, wherein the array of electromagnets is constituted by one or more rails for producing the dynamic field to propel the magnetic pseudo fluid.

1 1. The system of claims 5 to 10, wherein the magnetic pseudo-fluid comprises a ferromagnetic material, a paramagnetic material, or combination thereof.

12. The system of claim 1 1 , wherein the material includes any one selected from the group containing: nano or micro-scale dust; macroscopic particles; hollow objects including substantially spherical shells; solid spheres; or a combination thereof.

13. The system of claim 12, wherein the hollow objects contain one or more fillings.

14. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is recirculated, at least partially within the craft.

15. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is adapted to enhance their wear resistance. 16. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is surface treated.

17. The system of claim 16, wherein the surface treated is treated by carburisation.

18. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is treated to improve its acoustic damping. 19. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is coated with an elastomer.

20. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is treated to improve its corrosion resistance.

21. The system as claimed in any preceding claim, wherein the magnetic pseudo fluid includes particles and at least some of the particles are treated to improve their flow capability.

22. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is coated with a fluoro-polymer.

23. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is adapted to provide energy absorption. 24. The system as claimed in any preceding claim, wherein at least some of the dynamic magnetically responsive material is either hollow; or completely or partially filled with a ceramic material or foam.

25. The system as claimed in any preceding claim, adapted to change or lack an acoustic signature by altering the activation patterns of the electromagnets.

26. The system as claimed in any preceding claim, wherein the electromagnets are arranged in a grid. 27. The system as claimed in any preceding claim, wherein the skin comprises a smooth outer surface.

28. The system as claimed in any preceding claim, wherein the craft is a land vehicle.

29. The system as claimed in any preceding claim, wherein the craft is an aquatic vessel.

30. The system of any preceding claim, wherein at least some of the dynamic magnetically responsive material are projected outward toward the incoming threat.

31. The system of any preceding claim, wherein at least some of the dynamic magnetically responsive material comprises particles, the particles including an explosive or reactive capability to aid in neutralizing the incoming threat.

32. The system of any preceding claim, further comprising a mechanism to transfer at least some of the dynamic magnetically responsive material between to a second craft. 33. The system as claimed in any preceding claim wherein the dynamic magnetically responsive material comprises cilia-like appendages, the cilia-like appendages having ferromagnetic particles embedded therein.

34. A dynamic protection system for craft against a threat, the craft having a skin, the system comprising:

an array of resistive or superconducting electromagnets disposed in operable proximity to the skin; an activation and control sub-system for activating the electromagnets and controlling the activation sequence of electromagnets; and

dynamic magnetically responsive material responsive to dynamic field patterns, in operable proximity to the array of electromagnets, whereby the dynamic magnetically responsive material is positionable via activation of the electromagnets in response to the threat.

35. The system of claim 34, wherein the craft is dispose upon or in a surface. 36. The system of claim 34 to 35, wherein the dynamic magnetically responsive material is a movable fluid.

37. The system of claim 34, wherein the movable fluid is a magnetic fluid. 38. The system of any preceding claim, wherein the dynamic magnetically responsive material comprises a magnetic pseudo-fluid.

39. The system of claims 34 to 38, wherein the magnetic pseudo-fluid is a ferrofluid.

40. The system of claims 34 to 39, wherein the magnetic pseudo-fluid is a magneto-rheological fluid.

41. The system of claims 34 to 40, wherein the array of electromagnets is constituted by on or more rails arranged for producing the dynamic field to propel the particles.

42. The system of claims 34 to 41 , wherein the magnetic pseudo-fluid comprises a ferromagnetic material, a paramagnetic material, or combination thereof.

43. The system of claims 34 to 42, wherein the material includes any one selected from the group containing: nano or micro-scale dust; macroscopic particles;

hollow objects including substantially spherical shells; solid spheres; or a combination thereof.

44. The system of claim 43, wherein the hollow objects contain one or more fillings. 45. The system of claims 34 to 44, wherein at least some of the dynamic magnetically responsive material is recirculated, at least partially within the craft.

46. The system of claims 34 to 45, wherein at least some of the dynamic magnetically responsive material is adapted to enhance their wear resistance.

47. The system of claims 34 to 46, wherein at least some of the dynamic magnetically responsive material is surface treated.

48. The system of claims 34 to 47, wherein the surface treated is treated by carburisation.

49. The system of claims 34 to 48, wherein at least some of the dynamic magnetically responsive material is treated to improve its acoustic damping.

50. The system of claims 34 to 49, wherein at least some of the dynamic magnetically responsive material is coated with an elastomer.

51. The system of claims 34 to 50, wherein at least some of the dynamic magnetically responsive material is treated to improve its corrosion resistance.

52. The system of claims 34 to 51 , wherein the magnetic pseudo fluid includes particles, and at least some of the particles are treated to improve their flow capability.

53. The system of claims 34 to 52, wherein at least some of the dynamic magnetically responsive material is coated with a fluoro-polymer.

54. The system of claims 34 to 53, wherein at least some of the dynamic magnetically responsive material is adapted to provide energy absorption.

55. The system of claims 34 to 54, wherein at least some of the dynamic magnetically responsive material is either hollow; or completely or partially filled with a ceramic material or foam.

56. The system of claims 34 to 55, adapted to change or lack a characteristic acoustic signature by altering the activation patterns of the electromagnets.

57. The system of claims 34 to 56, wherein the electromagnets are arranged in a grid.

58. The system of claims 34 to 57, wherein the skin comprises a smooth outer surface.

59. The system of claims 34 to 58, wherein the craft is a land vehicle.

60. The system of claims 34 to 59, wherein the craft is an aquatic vessel.

61. The system of claims 34 to 60, wherein at least some of the dynamic magnetically responsive material is projected outward toward the incoming threat.

62. The system of claims 34 to 61 , wherein at least some of the magnetic pseudo fluid comprises particles with explosive or reactive capability to aid in neutralizing the incoming threat.

63. The system of claims 34 to 62, wherein the dynamic magnetically responsive material has ferromagnetic particles embedded therein.

64. The system of claim 34 to 63, wherein the strength of the dynamic field pattern may be increased by flux compression.

65. The system of claim 64, wherein flux compression is activated by a signal from a sensor. 66. The system of claim 64 to 65, wherein flux compression is activated by crushing of one or more hollow conductive structures through which magnetic flux permeates.

67. The system of claims 34 to 66, wherein the strength of the dynamic field patterns may be increase by eddy current braking.

68. A method of propelling a craft having an outer skin comprising:

activating, in concert, a plurality of electromagnets on or in operable proximity to the skin of the craft in order to effect the movement of a dynamic magnetically responsive material is located on or in operable proximity of the electromagnets.

69. A method of protecting a craft having an outer skin comprising:

activating, in concert, a plurality of electromagnets on or in operable proximity to the skin of the craft in order to effect the movement of a dynamic magnetically responsive material which is located on or in operable proximity of the electromagnets..

70. A method of propelling a craft having an outer skin comprising:

locating an array of electromagnets along the skin of the craft;

disposing electromagnetically inducible material operably adjacent the array of electromagnets; and inducing a current on the array of electromagnets in a pattern to move the electromagnetically inducible material.

71. A fixed armour pack including two or more permanent magnets or electromagnets and a magnetic pseudo fluid positioned between the permanent magnets or electromagnets.

72. The fixed armour pack of claim 71 , wherein the magnetic pseudo fluid is disposed in a plurality of hollow structures.

73. The fixed armour pack of claim 72, wherein the magnets are positioned at an end of at least some of the hollow structures.

Description:
VEHICLE PROPULSION AND PROTECTION SYSTEM

FIELD OF THE INVENTION

The present invention relates to a combined propulsion and protective system, for land and aquatic vehicles; however also applicable for fixed structures.

BACKGROUND OF THE INVENTION

Propulsion:

At present, the mobility of land vehicles is achieved via tracked, wheeled or hover propulsion. Continuous tracks, common to tanks and certain tractors, consist of a flexible belt with connected rigid links that are mechanically moved in a closed circuit. Continuous tracks have a limited top speed, are mechanically complex and can damage the surfaces beneath them. Continuous tracks need regular maintenance and due to their mechanical complexity, can render the vehicle immobilized if damaged by wear and the like or hostile action, resulting in a mobility kill. However, as continuous tracks distribute their load over a wider area than wheels, they result in improved mobility over soft ground, better maneuverability and lower ground pressure.

In contrast, tires are ring-shaped components, which can be fluid filled or solid that fit around wheels to protect them and enhance their function. Wheeled propulsion for land vehicles tends to result in higher ground pressures compared to tracks. Wheels are typically powered by a combustion engine via an axle, driveshaft and gearbox, or independently powered using electric motors. Wheels allow for faster movement of the vehicle compared to tracks, but are also vulnerable to damage.

Hover propulsion for land or air vehicles entails lifting the vehicle off the ground using an air cushion (e.g. via fans), magnetic levitation or wing in ground (WIG) effect. The WIG effect refers to the reduction in drag experienced by an aircraft as it approaches a height approximately equal to the aircraft's wingspan above ground or other level surface, such as the sea. The effect increases as the wing descends closer to the ground, with the most significant effects occurring at an altitude of one half of the wing-span. A WIG boat is a boat with wings that cruises just above the water surface. The boat floats on a cushion of relatively high- pressure air between its wing and the water surface. By dramatically reducing ground friction, hover vehicles are fast and maneuverable. Hovercrafts are amphibious but their maximum weights are typically limited by the ability to maintain an air cushion.

The most common form of propulsion for aquatic/sea vehicles such as ships and submarines is in the form of submerged propellers. Underwater rocket propulsion utilizing supercavitation is a recent development. Propellers rely on displacing a small volume of water at a high velocity to provide a reactive and hence propulsive force on the vehicle. Unfortunately, propellers present a unique acoustic signature that cannot be altered easily by the vehicle using them. Furthermore, the aquatic vessel's maximum velocity is limited by cavitation effects around the blades, resulting in pitting and damage to the blades. The turbulence caused by propellers can also result in photo-luminescent plankton revealing the wake of the vehicle.

Protection of land vehicles:

The main threats to land vehicles come in the form of blast or impact threats. Blast threats can cause damage due to overpressures, shock effects, heat and fragmentation. I m pact threats can manifest themselves in the form of fragments, ballistic projectiles, explosively formed projectiles and shaped charges.

Protection of personnel against overpressures resulting in barotraumas can be achieved through the use of sealed compartments or appropriate shelter. Improving the resilience of the vehicle against shock loading has historically been achieved via the use of crushable foams or a layered arrangement with minimal mechanical coupling between the layers, thus inhibiting shock propagation and encouraging shock reflection at the interfaces.

The current state-of-the-art protection against impact threats includes a laminate or composite made of a combination of hard, brittle layers and tough ductile layers, for example ceramic tiles encased within a metal matrix and bonded to a backing plate and several elastic layers. Unfortunately, the multi-hit capability of this type of armour is limited by fracture of the brittle ceramic as well as coincident impacts, particularly for tandem warheads. Furthermore, this passive, fixed protection system relies on having the right armour at the right place(s) at the time of manufacture, meaning that an enemy can observe weak spots in the armour and target those regions of the vehicle. Vehicles equipped with this passive armour are also vulnerable to improvements in projectile technology, such as tandem warheads and shaped charge jets. The latter consists of a rapidly moving stream of ductile metal that is explosively formed into a jet travelling at several kilometers a second. At these velocities, the mechanical strengths of the jet and armour are irrelevant, and the response is hydrodynamic.

Alternatively, protection through the use of Explosive Reactive Armour (ERA) packs/cassettes is becoming increasingly popular; see US Patent 4,741 ,244 (1988, Ratner). Such packs consist of a sandwich of explosive material between two metal plates. Upon impingement by a shaped charge jet, the explosive detonates and propels the faceplates apart. This results in the shaped charge jet being obstructed by fresh material and dispersed by the explosion. Unfortunately, ERA packs can pose a threat to nearby friendly infantry, can result in sympathetic detonation of neighboring cassettes, have no multi-hit capability at the explosion site and themselves present significant behind armour dynamic loading.

SUMMARY OF THE INVENTION

The present invention relates to a system for propelling land vehicles and aquatic/sea vessels (which hereinafter in the description and claims will typically be referred to collectively as: "craft"). In addition, the term "craft" shall include air craft, although most practical implementations of the invention are likely to be land and sea craft.

The present invention also relates to a system for protecting craft as well as fixed structures against attack; in particular against shaped charge jets , explosively formed projectiles and blast threats.

According to one aspect of the invention, there is provided a propulsion system for a craft having an outer skin comprising:

an array of resistive or superconducting electromagnets disposed in operable proximity to the skin;

an activation and control sub-system for activating the electromagnets and controlling the activation sequence of electromagnets; and

dynamic magnetically responsive material responsive to dynamic field patterns, in operable proximity to the array of electromagnets, whereby the craft is propel-able by activating the electromagnets in concert with such activation being arranged to propel the craft.

According to a further aspect of the present invention there is provided a dynamic protection system for craft against a threat, the craft having a skin, the system comprising:

an array of resistive or superconducting electromagnets disposed in operable proximity to the skin;

an activation and control sub-system for activating the electromagnets and controlling the activation sequence of electromagnets; and

dynamic magnetically responsive material responsive to dynamic field patterns, in operable proximity to the array of electromagnets, whereby the dynamic magnetically responsive material is positionable via activation of the electromagnets in response to the threat.

In some embodiments, the propulsion via the dynamic outer skin may be similar to biological peristalsis wherein a dynamic magnetic pseudo-fluid (MPF) moves over the outer hull/surface or appendages, at the outer hull are caused to move. The term appendages are, without limitation, for example cilia-like appendages, which may be referred to as "cilia" herein the description and claims to indicate any appendages appropriate for motility and/or protection of a craft or portion thereof. The skin or hull is preferably smooth.

The terms "skin", "outer skin", "outer layer", "hulf, "outer hulf, "outside of the hulf and the like may be used interchangeably; and such terms herein after in the specification and claims should be understood in their broadest sense to denote or comprise the outermost surface or layer of a craft or any such surface or layer that is in enough proximity to the outermost surface to facilitate propulsion; including appendages such as cilia, for example.

The terms: "array" "network' and "grid" may be used interchangeably; and such terms herein after in the specification and claims should be understood in their broadest sense to denote any arrangement whereby some or all the electromagnets have an influence on propulsion of the craft - or in some embodiments, whereby some or all the electromagnets have an influence on protection of the craft.

An array of electromagnets is arranged under the outer hull (or any other portion of the craft operably in contact with an environmental fluid, or the ground, against which the propulsion movement may react) of the vehicle or structure. A dynamic magnetic pseudo-fluid (MPF) comprising an aggregate of magnetic particles, or fixed protrusions (e.g. resembling biological cilia) from the outer surface of the hull, is moved or manipulated in position about the hull through the use of phased/controlled activation of the electromagnets.

Propulsion of land vehicles is achieved by phased activation of the electromagnets to form dynamic movement, which may include a rippling-like movement, of the MPF over the outside of the hull or motile cilia, resulting in a net reactive force against the ground. Biological precedents for this method of propulsion have been demonstrated in snails and slugs. For aquatic vehicles, the same principle is applied to entrain a volume, typically a large volume, of water over at least a portion of the wetted hull surface to achieve a propulsive force. Existing examples of magnetic-responsive fluids are ferrofluids and magneto-rheological fluids

For propulsive purposes, movement of the MPF is always outside the hull. For protective purposes (described below) the MPF may alternatively be located within a sandwich of an inner/outer hull.

The particles responsive to dynamic magnetic particles induced by the electromagnets are generally referred to herein as a magnetic pseudo-fluid (MPF) as the particles are envisioned to comprise an aggregate of different particles exhibiting both magnetic and fluidlike behavior; however this is not meant to exclude true fluids that are responsive to magnetic fields, such as plasmas and electrically conductive fluids with an electrical current passing through them.

According to various embodiments, features of the dynamic magnetic pseudo-fluid (MPF) can include the following:

1. Ferromagnetic and paramagnetic materials.

2. The MPF can comprise nano/microscale magnetic dust, as well as macroscopic magnetic particles (e.g. spheres), which may be hollow to save weight. Magnetic debris can also be used in an ad hoc manner.

3. The MPF may be treated for acoustic mitigation, wear and corrosion resistance, for example with rubber, carburisation and polymer coatings (e.g. fluoropolymers), respectively.

4. The MPF may be modified for energy absorption (e.g. hollow crushable spheres with foam cores) or impact resistance (e.g. hollow spheres with ceramic cores - for example against kinetic energy penetrators).

5. Hollow objects such as spherical shells containing one or more different fillings and/or a coating, depending on operational requirements (e.g. an incoming threat). 6. Solid objects such as spheres.

7. The MPF may be modified to respond actively to incoming threats. For example hollow spheres with explosive cores could be used as a combined active protection system and Explosive Reactive Armour concept - for example against a shaped charge. The spheres can be ejected from the hull by suddenly reversing the polarity of the electromagnets or by relying on pulsed current to induce repulsive forces in accordance to Lenz' Law. According to certain embodiments, an embedded detonator will respond to radio or other such command means and detonate the MPF. Such a system is less vulnerable to typical sympathetic detonation of the spheres as the ejected portion would be physically separated from the bulk of the remaining MPF.

The MPF may additionally comprise;

1. hollow tubes or solid filaments;

2. cilia actuated through the use of external magnetic fields, as generated by present system, inherent elasticity, electro-active polymers, piezoelectric actuators or pressurisation of hollow tubes; and

3. shear thickening fluids, foams, ceramic particles or elastomers (e.g. natural or artificial rubber) to improve energy absorbed during impact and blast events.

The cilia may also be electrically conductive with an insulating sheath so that impact events involving two or more cilia would result in the insulation being destroyed, a massive short circuit and vaporisation of the impacting projectile, see International Patent Application WO 2006/085989 A2 (2006) by Garvey, A. et al.

The present propulsion system is amphibious. The system is inherently redundant in that the vehicle will still operate if it has lost some MPF, as compared with a wheeled or tracked vehicle that is typically incapacitated it loses one wheel/track; mechanically simple; and lacks any single point of mechanical failure, making it damage tolerant. Because the patterns of activated MPF propelling the craft are controlled by independent electromagnets, vehicles equipped with the present propulsion system would be highly maneuverable. Land vehicles using the technology would have a low ground contact pressure and could traverse different terrain easily. The electromagnets can also magnetically lock together through direct contact or through a MPF bridge between craft, allowing an even greater effective footprint to allow them to traverse particularly inhospitable terrain. Maximum speed is controlled by the rate at which electromagnets can be switched on/off, optimisation of the activation patterns and the magnetic field strength, which governs the thickness of the pseudo-fluid between the vehicle and the ground.

For aquatic vehicles, as a large volume of water is moved at a lower speed in comparison to moving a small volume of water at high speed, the system is relatively quiet; energy efficient owing to a high Froude efficiency; and not limited by a cavitation ceiling as with propellers. Furthermore, the activation patterns of the dynamic skin can be altered immediately, resulting in improved roll, yaw and pitch control of the vehicle even if initially at rest. Being able to alter the activation patterns of the dynamic skin/electromagnets would allow the aquatic vehicle to lack any characteristic acoustic signature.

Velocity of the vehicle is governed by the total volume and velocity of the entrained water; this is in turn determined by the field strength, wetted area and rate of activation of the electromagnetic grid. The MPF may be surface treated to protect it against corrosion as well as to act as an additional acoustic damping layer through the use of anechoic media such as foamed rubber.

In some embodiments, protection of vehicles equipped with the present system would be achieved by dynamically moving the MPF in anticipation of likely threat vectors, or in response to the trajectory of an incoming threat. Using the technology of the present invention, a relatively large quantity of material can be put in the path of an incoming threat. The degree of protection against specific threats depends on the responsiveness of the system, the strength of the magnetic fields and the composition of the MPF. The latter can be varied rapidly in the field by transferring MPF between vehicles in response to emerging threats or depletion of the MPF due to hostile action.

Incident blast-induced Shockwaves can be attenuated by expending energy in the crushing the MPF aggregates/particles; friction between the MPF aggregates/particles; crushing cellular MPF such as hollow spheres; doing work against the applied electromagnetic field and induced currents to disperse the MPF; and utilizing poor mechanical coupling between particles in the MPF to mitigate shock transmission to the underlying structure of the craft.

Kinetic penetrators and explosively formed projectiles can be arrested by direct obstruction of the path of the projectile by the MPF and incorporation of hard materials into the MPF (e.g. hollow metallic MPF with ceramic cores) to destroy, deflect or otherwise neutralize or mitigate the effects of the penetrators/projectiles, for example by causing tumbling and so on.

In some embodiments shaped charge munitions can be deflected or prematurely detonated by ejecting the MPF from the hull of the vehicle in the path of the oncoming munition by rapidly reversing the electromagnet polarity. In some of those embodiments, the MPF may also contain active constituents such as hollow spheres with explosive cores. Some of these active MPF spheres may be ejected in the path of an oncoming threat, to be detonated by the shaped charge jet or by remote control, or a portion of the MPF spheres moved in the path of the incoming jet without being ejected from the hull H. Having a thickened region of MPF 10 in anticipation of an impact improves impact resistance by distributing impact forces over a wider footprint due to nesting of the MPF and both momentum and energy are transferred from the projectile to the MPF. This technology adds magnetic field strength to the material strength in resisting penetration and blast threats.

Due to the dynamic nature of the armour, less total material is needed for the same level of protection against a directed threat compared to conventional passive armour which must take all possible attack trajectories into account. The electromagnet array is envisioned to act in both a propulsive and protective capacity. It is therefore expected that this system will offer weight savings over the conventional method of distinct propulsive and protective systems. Furthermore, as the MPF or cilia covering the vehicle is dynamic, it can be vibrated or moved so as to continually present fresh material for a projectile, see US Patent 5,866,839 (Ohayon).

According to a further aspect of the present invention there is provided a fixed armour pack for attachment to a craft, the fixed armour pack having two or more permanent or electromagnets and a magnetic pseudo fluid positioned between the permanent or electromagnets. In this way the protective capability of a craft can be enhanced by applying the fixed armour pack to the craft. Notably, in this aspect only a protective aspect is offered and no propulsive features are present.

According to a further aspect of the present invention there is provided a method of propelling a craft having an outer skin comprising:

activating, in concert, a plurality of electromagnets on or in operable proximity to the skin of the craft in order to affect the movement of a dynamic magnetically responsive material is located on or in operable proximity of the electromagnets.

According to a further aspect of the present invention there is provided a method of protecting a craft having an outer skin comprising:

activating, in concert, a plurality of electromagnets on or in operable proximity to the skin of the craft in order to affect the movement of a dynamic magnetically responsive material which is located on or in operable proximity of the electromagnets. Optionally, the electro magnets are operable to control the MPF over a substantial portion of the wetted surface area of the craft. Advantageously, the manoevurablity and defensive capability of the craft are improved.

Optionally the strength of the dynamic field pattern may be increased by flux compression. Flux compression may be achieved by the crushing of one or more hollow conductive structures through which magnetic flux permeates. The hollow conductive structures being arranged to be crushed by an incoming projectile. Advantageously, flux compression can be activated by the incoming projectile.

Optionally the deceleration of electrically conductive projectiles may be increased by eddy current braking. Advantageously eddy current breaking acts to provide a force which opposes the vector of an incoming projectile.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the following drawings, in which: Figs. 1A and 1 B are schematic side views of two examples of craft propelled using prior art systems; a tank and a submarine, respectively;

Fig. 2 is a schematic side view of a tank fitted with an embodiment of a propulsion system of the present invention;

Fig. 3 is a schematic side view of a submarine fitted with an embodiment of a propulsion system of the present invention similar to the system of Fig. 1 ;

Fig. 4 is a schematic side sectional view illustrating a positioning of electromagnets of the propulsion system of the present invention;

Fig. 5 is a schematic illustration of an exemplary array of electromagnets of the propulsion system of the present invention in accordance with some embodiments;

Figs. 6A and 6B are schematic side and perspective views, respectively, showing an exemplary embodiment of a protection aspect of the present system;

Fig. 7 is a schematic top view of two tanks showing the transfer of electromagnetic particles of the present system between the tanks;

Figs. 8A and 8B are schematic side views of an embodiment of the present system comprising a cilia-like propulsion feature also illustrating threat protection;

Figs. 9A-9C schematically depict a computer simulated of a typical (prior art) projectile impact at various stages;

Figs. 10-13 schematically illustrate embodiments of an armour pack of the invention, wherein Fig. 10 shows a perspective view of the armour pack with a partial cutaway; Figs. 1 1- 13 are side view of a tube of the armour pack, with Figs. 12 and 13 illustrating the reaction of the tube to an impact;

Figs. 14-16 schematically illustrate embodiments of the propulsion system using an electrical current to induce propulsion, wherein Fig. 14 shows a known (prior art) technology of a railgun, employed in these embodiments; and Figs. 15 and 16 illustrate further embodiments of the invention related to propulsion; and

Fig. 17 shows the distribution of magnetically responsive fluid under a hull of a vehicle at two different activation times of adjacent electromagnets. The following detailed description of the invention refers to the accompanying drawings referred to above. Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Referring first to Figs. 1A and 1 B, there is shown two examples of craft propelled using prior art systems; a tank and a submarine, respectively. The propulsion mechanism of the tank (Fig. 1A) comprises a pair of continuous tracks T (only one visible). Most continuous tracks are made of a number of rigid units that are joined to each other with a hinge. This allows the track T to be flexible and wrap around a set of wheels W to make the endless loop; however, some tracks are made of a flexible belt for such a purpose. An engine (not seen) provides the power to propel the tank by spinning drive wheels W (located adjacent the tank's hull H), thus turning the track T. The tank is turned or steered by controlling the relative speed of the tracks T.

The propulsion mechanism of the submarine (Fig. 1 B) comprises a propeller P, powered by an engine (not seen), to propel the submarine, and one or more rudders, for example rudder R, typically hinged outside the submarine's hull H, as well as one or more fins F, for steering.

Figs. 2-5 show embodiments of a propulsion system of the present invention comprising: a dynamic magnetic pseudo-fluid (MPF) 10 including an aggregate of magnetic particles in the form of hollow magnetic spheres 12 (Fig. 2); and an array of electromagnets 14 disposed on the inside surface of the hull H of a craft (or on suitable internal surface in the case of craft having a double hull, schematically illustrated in Figs. 6A and 6B, or other hull variation). The propulsion system further comprises a control and activation sub-system 16, for controlling the activation sequence of the electromagnets 14 that are activated.

Exemplary implementations of the propulsion system are shown with respect to a tank and a submarine (Figs. 2 and 3, respectively). To propel and maneuver the tank (Fig. 2), hollow magnetic spheres 12 of the MPF 10 (the particles constituted for example by ceramic- filled hollow spheres), are caused to "flow" about the tank's hull H, by controlled activation of electromagnets 14 (not visible in Fig. 2) at various locations along the hull. Thus movement of the tank is caused by friction between the ground and the hollow magnetic spheres 12. Arrows A1 indicate the exemplary direction, which in this case is in a generally straight and forward direction. The hollow magnetic spheres 12, and any such magnetic particles, can comprise particles of varying sizes/diameters, for example to allow better packing thereof.

In particular embodiments of the present propulsion system, the electromagnets 14 are locatable and activatable to move the MPF 10 to maneuver the craft in more than one and in certain embodiments any suitable manner (e.g. forward, backward, rotating, to the right, to the left and even sideways; and in the case of a craft such as a submarine or aircraft, the craft can be moved up or down - potentially even straight up, mutatis mutandis). With regard to certain craft, such maneuverability can be aided by an auxiliary steering device, for example a rudder, wheel, flap or the like (not shown).

The present embodiment illustrates an external circulation of the MPF 10 wherein the hollow magnetic spheres 12 leaving the rear are re-circulated out of contact with the ground. It should be understood that the high bulk contact area of the MPF 10 with the ground provides for a low ground pressure, which can prove advantageous for traversing irregular and/or soft terrain. In theory, recirculation is not necessary as biological organisms such as worms and snails are able to move by peristalsis without such recirculation. However, a propulsion system comprising a recirculation scheme may permit higher top speeds, though perhaps at the expense of increased noise.

Fig. 3 shows a submarine modified with an embodiment of the propulsion system of the present invention. The particles responsive to dynamic field patterns are constituted by an aggregate of acoustically damped magnetic beads 12a. For clarity, only some of the beads 12a are depicted. It is anticipated that there would be a sufficient amount of beads to more or less completely cover the submarine's hull H and moreover enough beads to provide a redundancy in the event of loss, detachment or destruction of some beads.

In some embodiments, such as illustrated in Fig. 3, acoustically damped beads 12a are circulated internally within one or more MPF passageways 18. Arrows A2 indicate a general flow direction of the beads 12a, however the beads can be moved across the hull H in different patterns by different activation patterns to not only achieve propulsion, but also to control pitch, yaw and roll control - whether the submarine is in motion or at rest. Movement of the submarine is generally due to water entrainment by the beads 12a of the MPF 10.

In contrast to the typical characteristic noise signature common to the propulsion system of present day submarines, the present propulsion system can produce a variable acoustic signature, depending upon activation patterns of the electromagnets 14. Because of the acoustic signature of the propulsion system depends on the electromagnetic array activation patterns, in addition to the properties of the MPF 10, the system can be rendered stochastic. The MPF 10 can also act as an additional acoustic mitigation layer instead of or in addition to anechoic tiles often used on submarines. Additionally or optionally, particles of the MPF 10 can be treated for corrosion or wear resistance, for example by coating or processing in a carburisation heat treatment.

It is possible for a small portion of MPF 10 to be detached from the hull H of the submarine (or relevant craft) to act as autonomous decoys. This is because any grid of electromagnets, suitably controlled and powered, with a MPF coating would have basic propulsive capability. These autonomous decoys could move themselves in the path of oncoming torpedoes/depth charges and detonate/trigger mines and even seek out opposing vessels (craft), and attach themselves to those vessels and self-destruct.

Fig. 4 is a schematic side sectional view illustrating an exemplary positioning of electromagnets 14 of the propulsion system of the present invention. The electromagnets 14 are spaced apart and disposed in proximity to the hull H, typically attached thereto. Also illustrated are exemplary magnetic particles constituted by energy absorbent ceramic-filled magnetic spheres 12b filled with ceramic material 20. The electromagnets 14 are activated and deactivated sequentially to move the ceramic-filled magnetic spheres 12b of the MPF 10 along the hull H over the ground G; for example with an activation order of electromagnet 14a then 14b followed by 14c. The speed and sequence of activation of the electromagnets 14 in conjunction with environmental conditions determines the velocity of the MPF 10 and thus the velocity of the craft.

It should be understood that regardless the examples of the magnetically responsive particles, i.e., hollow magnetic spheres 12 (Fig. 2); acoustically damped magnetic beads 12a (Fig. 3); and ceramic-filled magnetic spheres 12b (Fig. 4) illustrated in the figures, according to some embodiments those particles could be of a variety of designs and, for example, be non- homogeneous being of different types and having different, heterogeneous, sizes. For example, the MPF 10 could comprise a mixture of any of nano-scale and micro-scale magnetic dust, magnetic debris, and macroscopic spheres, which may be hollow or filled.

In particular embodiments, it is envisioned that the MPF 10 would be distributed to provide a propulsive force along the entire contact area with the ground, for land vehicles, or wetted area in the case of an aquatic vessel and does not have any single point of failure.

Fig. 5 schematically illustrates an exemplary array of electromagnets of the propulsion system of the present invention in accordance with some embodiments. The schematic figure shows five electromagnets 14 spaced apart along a portion of the hull H of a craft and positioned along conducting channels, for example orthogonal conducting channels 22. According to some embodiments the propulsion system comprises dozens and potentially hundreds or more electromagnets 14. It should also be understood that the activation of the electromagnets 14 can be in any direction and in more than one direction at a time whereby propulsion of the craft can be in a variety of directions including a side to side direction which is difficult if not impossible for most craft.

Figs. 6A and 6B schematically depict an embodiment of a protection aspect of the present system, exemplified in double hulled craft, i.e. having an outer hull H1 and an inner hull H2. Upon receiving information of a threat (for example, an incoming missile threat M, depicted by an arrow as so labeled) the MPF 10 can be redistributed to the location of the expected impact, in this example by activating the center electromagnet 14. Controlling the active strength of electromagnets 14 located in one (or more) areas causes the MPF 10 to be concentrated in the particular area(s) of the craft to provide enhanced protection in that/those areas against the incoming threat. The MPF 10 can also be redistributed between craft (described below).

In addition, by control of the electromagnets 14, in particular sudden reversal of polarity, the MPF 10 can be projected outward toward the threat M. With the use of MPF 10 comprising explosive magnetic particles (for example, hollow magnetic spheres 12 with explosive cores), threat protection with explosive reactive armour capability is provided. In some embodiments the present system comprises an embedded detonator which responds to a radio or other command to detonate the MPF 10. As such, the system provides an aspect of armour to the craft in addition to propulsion thereof.

Fig. 7 illustrates a transfer mechanism for transferring electromagnetic particles of the MPF 10 between two craft (two tanks). Transfer of MPF 10 between craft can be accomplished by strong activation of one or several electromagnets 14 at one or more MPF receiving portions 24 of an MPF-receiving craft R in concert with turning down the field strength of a donor craft D. Magnetic flux lines 26 can thereby be attained between the two tanks. The MPF 10 will redistribute itself along the flux lines 26.

Alternatively or optionally, for such purpose, the tanks can comprise or be fitted with transfer tubes (not shown) that attach to the present system (and pump/blower or the like - not shown).

Transfer of MPF 10 can be desired for a variety of reasons, for example, to replace lost MPF 10 by a tank, or provide increased MPF to aid in maneuverability or improve protection against a specific threat. Furthermore, the transfer of MPF 10 can be used to help protect (schematically depicted) soldiers 28 in the area.

Figs. 8A and 8B illustrate embodiments of the present system comprising a propulsion feature including a plurality of appendages such as cilia-like projections or cilia 30, as well as a protection feature (Fig. 8B). In accordance with some embodiments, some of the cilia 30 are non-motile (i.e. not actuated/manipulated using electromagnets 14). As such, the non-motile cilia may act as "dumb" fur. Actuation and movement of the motile cilia may be accomplished by external magnetic fields, inherent elasticity, electroactive polymers, piezoelectric actuators or pressurisation of hollow tubes. This actuation and movement can be to provide propulsion, and/or, for protection from an incoming missile threat M, as illustrated in Fig. 8B. The cilia 30 may be further modified to meet certain blast and impact threats, such as being filled or coated with a shear thickening fluid, foam, ceramic particles, cladding and elastomers, or a combination of such modifications (treatments). For example, "smart motile cilia", which are magnetically responsive, would, in certain embodiments, have ferromagnetic particles embedded in them. In particular embodiments the cilia 30 have an insulating sheath with a conductive core so as to help neutralize incoming shaped charge jets by inducing a short circuit. In other embodiments, the cilia 30 may also be electrically charged but isolated from each other so that penetration of two cilia 30 by a projectile would result in a large electrical discharge and vaporisation of the incident projectile.

Thus, there has been described a system and method for propelling craft and as well as providing protection against blast and impact threats. The system/method inherently imparts amphibious capability to such craft. Vehicles propelled and protected by present system would require a source of electrical energy. Craft propelling themselves with the disclosed system can vary their acoustic signatures in the field. Furthermore, the technology allows craft to dynamically adapt their protective coverage depending on developing threats and permits craft equipped with the technology to transfer protective material between themselves so that elements more exposed to attack, such as frontal units, can receive additional armour. The protective nature of the technology is regenerative and will permit craft thusly equipped to potentially survive multiple attacks in the same region of their skin/hull. Furthermore, the technology of the present system is well suited to for use in future electric craft.

Figs. 9A-9C schematically depict a smoothed particle hydrodynamics simulation of typical (prior art) scenario wherein a 2x10m steel projectile 40 strikes a 9mm thick aluminum plate 42 at 1 km/s using a transient dynamic finite element program; the figures showing the approach, impact to about half penetration and complete penetration, respectively. As seen in Fig. 9B, at 28 micro-seconds post-contact, the projectile has penetrated about half way into the aluminum plate 42. In this scenario, where a projectile strikes an unmodified plate, cohesion of the plate material is solely a material property. Further, at very high impact velocities such as a few km/s, the projectile/plate response is hydrodynamic and can be reliably predicted using fluid dynamics rather than mechanical properties. As can be seen, there is no inward restoring force on the plate-material to restore (close) the developing penetration channel (Fig. 9C) and thus no mechanism for repairing or mitigating the hole produced by the penetration. Therefore, the penetration channel persists.

In order to remedy the aforementioned situation, another exemplary embodiment of the system, termed "fixed armour packs" is now described. The fixed armour pack embodiment is not designed to provide the adaptability, propulsive and stealth characteristics of the approach using the grid or array of electromagnets 14 on the vehicle or craft, existing craft can be retrofitted with such armour packs at low cost whilst maintaining some aspects of earlier described embodiments of the system, namely, regenerative capability and improved resistance against blast and impact threats.

With reference to Figs. 10-13, according to one embodiment, the present armour pack takes the form of hollow structures such as cells or tubes 50, sandwiched by magnetic face plates 52. The hollow tubes 50, which are not necessarily of circular cross-section, have walls or a casing 54. At the ends of some or all of tubes 50 are disposed magnets 56, which according to some embodiments are permanent magnets; and in other embodiments are electromagnets, such as electromagnets 14; or a combination thereof. In tubes 50 with magnetic ends, the hollow portion of the tubes is filled with MPF 10. The presence of the hollow portion in the sandwich armour structure also offers weight savings whilst improving specific energy absorption of the hybrid structure, for example through tube bending and crushing.

Fig. 10b illustrates the internal composition of a hollow tube 50 under a missile threat M. An electromagnet array 14 or permanent magnets maintains the MPF 10 between the poles. In this embodiment the MPF 10 comprises hollow magnetic particles 12; ceramic filled hollow magnetic particles 12b; metallic/polymeric foam-filled magnetic particles 12c; supercritical fluid filled particles 12d to facilitate break-up of a projectile through a micronisation process known as "Rapid Expansion of Supercritical Solutions"; and explosive-filled particles 12e. The particles are of different geometries (spheres, spheroids) and characteristic dimensions. Fig. 11 illustrates a schematic side view of one hollow tube 50 wherein it is seen that the polarity of the magnetic ends is arranged such that a magnetic field flows from the inner face of one end to the other end of the tube 50. The majority of the resultant flux (depicted by arrow 58) will be contained within the hollow portion of casing 54 if the casing is made out of a material with low magnetic permeability while it is filled with a material of high magnetic permeability. Due to the fluid-like behavior of the magnetic MPF aggregates or particles within the cell or tube 50, the MPF particles of each tube act to align themselves so as to minimize their magnetic reluctance. This is the principle behind the reluctance motor, for example as disclosed in US Patent 6,121 ,706.

Therefore, mechanical forces will exist to move low reluctance materials such as MPF

10 toward regions of higher flux. This behavior results in self-repair of any perforations or channels through the tube 50 and also provides a crack-closing force should any crack attempt to traverse the MPF 10, for example through wear and tear to weapons fire. The shear strength can be modified by strengthening the magnetic fields, increasing the magnetic permeability of the contents and altering the geometry and composition of the MPF aggregate. At very high impact velocities where localisation of the response occurs, the material properties will become increasingly irrelevant. In some embodiments, MPF 10 comprises hollow ferromagnetic spheres containing explosives to counter shaped charge jets , and ceramic fillings to counter hard/dense penetrators and explosively formed projectiles.

Fig 12 illustrates a scenario where the target plate, for example plate 42, has a high magnetic permeability, the projectile (e.g. projectile 40) does not, and a magnetic field exists between the two ends of the tube. As the modified armour ("armour pack") gets perforated, i.e. a tube 50 of the armour pack comprising MPF 10, the magnetic field lines become confined to a region of high magnetic permeability. This encourages cohesion of the material (MPF 10) ahead of a projectile, such as projectile 40, and closure of the material along the circumference of the projectile, thereby improving resistance to perforation. Optionally additional impact resistance can be conferred to the armour pack from flux compression effects and/or eddy current braking. Flux compression can be used to increase the magnetic field strength in response to a projectile, and thereby enhance the resistive capability of the MPF when impacted by a projectile. Eddy current braking can be used to increase the rate of deceleration of the projectile. These effects are discussed in more detail in "Potential Micrometeoroid and orbital debris protection system using a gradient magnetic field and magnetic flux compression," Giffin, A. et al Applied Physics Letters 97 [2010]

Fig. 13 depicts the regeneration of a penetration channel following an impact event. Should perforation occur, the penetration channel is quickly re-sealed due to the fluid-like behavior of the MPF 10 and its tendency to line up along the flux lines to minimize magnetic reluctance.

Shaped charge jets exhibit armour piercing capability owing to their high impact velocities, typically several kilometers per second, resulting in a hydrodynamic impact response. Both the jet and target material behave in a fluid-dynamic manner. Crucially, shaped charge jets exhibit their armour piercing capabilities due to being able to concentrate a large amount of kinetic energy on a small cross sectional area. An efficient armour system would therefore seek to disperse this kinetic energy over a wider area.

Cohesion of a shaped charge jet can be disrupted through the presence of ferromagnetic particles in a strong magnetic field, generated either by permanent magnets or electromagnets, superconducting or otherwise. Rapid displacement of the ferromagnetic or electrically conductive particles within a magnetic field would induce Foucault eddy currents in neighboring conductors to oppose the change (and vice versa), in line with Lenz's law where induced currents will act to oppose the motion or change causing it.

Lenz's law can therefore be used in a hybrid armour system incorporating magnetic fields and electrical conductors to offer improved resistance to penetration. It is worth noting that the majority of shaped charge jets to date are made of electrically conductive metals, and would therefore be subject to induced Foucault currents when penetrating a magnetic field, in line with Lenz's law.

Figs. 14-16 schematically illustrate embodiments of the propulsion system using an electrical current acting on a MPF 10 as a source of propulsion.

Fig . 14 shows a known (prior art) technology of a railgun, employed in these embodiments. A railgun consists of two firmly mounted parallel electrically conductive (e.g. metal) rails 60 connected to an electrical power supply (not shown). When a conductive object 62 (schematically indicated by a line bridging between the metal rails 60) is inserted between the rails, starting from the end connected to the power supply, it completes the circuit. Electrons flow from the negative terminal of the power supply up the negative rail, across the projectile, and down the positive rail, back to the power supply; the electron flow or current represented by arrows 64. This current makes the railgun behave as an electromagnet, producing a powerful magnetic field in the region of the rails 60 up to the position of the object 62. In accordance with the right-hand rule, the magnetic field circulates around each conductor, i.e. the metallic rails 60. Since the current is in opposite direction along each rail 60, the net magnetic field between the rails is directed vertically, direction B in Fig . 14. In combination with the current (I) across the object 62, this produces a Lorentz force which accelerates the projectile along the rails 60. There are also forces acting on the rails 60 attempting to push them apart, but since the rails are mounted firmly, they cannot move. The object 62 slides up the rails 60 away from the end with the power supply.

A very large power supply (not shown) providing on the order of one million amperes of current will produce a tremendous force on the object 62, accelerating it to a speed of many kilometers per second (km/s). Speeds as high as 20km/s have been achieved with small objects explosively injected into a railgun. Although these speeds are possible theoretically, the heat generated from the propulsion of the object 62 is enough to erode the rails 60 rapidly. Such a railgun would require frequent replacement of the rails 60, or use a heat resistant material that would be conductive enough to produce the same effect.

Fig. 15 schematically illustrates a lower surface 66 (of an exterior surface) of a vehicle using MPF 10 can be propelled using electrical current in conjunction with the MPF for propulsion, to provide additional acceleration. Lower surface 66, which is in contact with the ground, has substantially parallel conductive rails 68 analogous to the rails in Fig 14. The MPF 10 acts as the conductive object 62 referred to with respect to Fig 14, and is propelled parallel to the parallel conductive rails 68 by action of the Lorentz force.

The MPF 10 itself, although intended to be ferromagnetic, can also be constructed to be electrically conductive, for example by being a mixture of ceramic spheres of different radii coated with an ferromagnetic shell and combined with micro-scale or nano-scale ferromagnetic dust.

Figs. 16A and 16B illustrate a modification or alternative method of propelling a vehicle equipped with a MPF such as MPF 10, through a magneto-hydrodynamic (MHD) effect.

With reference to Figure 17 the process of propelling the craft will now be described in more detail. In this example there are two electro magnets, however it should be appreciated that the process may be extended to cover any number of magnets greater than two all of which are operable to act in concert. In figure 17 a horizontal lower surface of the craft located at position y = 0. A hard pavement is positioned at y = -1 and a soft deformable ground is positioned between y = 0 to -1. The soft deformable ground envelopes the MPF. An electromagnet at position x = 2 is activated at time = 1. This causes a localized bulging of the MPF under the activated electromagnet. At a later time = 2, the electromagnet at position x = 4 is activated while the electromagnet at position x = 2 is deactivated. This draws the MPF from position x = 2 to x = 4. A reactive force is thus experienced by the craft at the contact points between the MPF and the hard or soft ground, resulting in propulsion in the negative x direction. The direction of propulsion can be altered arbitrarily by changing the activation patterns of the electromagnets, for instance, reverse motion can be achieved by activating the electromagnet at x = 2 after the electromagnet at x = 4.

The magneto-hydrodynamic drive works only in seawater W which is conductive. The herein-referred to MPF 10 that flows around the hull H of the craft (land or aquatic vehicle) can also be made to be electrically conductive as well as magnetically responsive so that it forms a suitable working fluid for propelling craft via magnetohydrodynamic propulsion in addition to the other methods described herein. Using a MPF instead of seawater would allow the vehicle to work in freshwater and on land, providing amphibious capability. Resistive or superconducting electromagnets 14 or permanent magnets 69 provide the necessary magnetic field B, while electrodes 60 on either side of the vessel's hull H provide the current flow I. Aquatic media 70 is entrained by the moving MPF 10, or is itself moved through a MHD effect if it is conductive, such as seawater in accordance with Fleming's Right Hand Rule. In summary, analogous to a railgun propelling a projectile via the interaction of a magnetic field created by its rails, and the magnetic field created by the conductive projectile, a propulsive embodiment of the present invention can be achieved by replacing the rails with long conductive strips on the exterior surface, and using an electrically conductive MPF in place of the projectile

A magnetohydrodynamic drive works by creating a magnetic field through magnets on the hull H of the vehicle and sending a current through seawater. In this case, the need for long conducting strips to interact with the projectile/seawater/MPF is removed via the use of dedicated magnets, which may be permanent magnets or electromagnets. The need for conductive seawater is removed by using a MPF, suitably modified for electrical conductivity.

In one embodiment of the present invention the electro magnetics are operable to control the MPF over a substantial portion of the wetted surface of the craft. Optionally the substantial portion may comprise 50% or more of the wetted surface area. This may be achieved by positioning a plurality of magnets over the wetted surface area. Advantageously, the efficiency and maneuverability of the craft is improved.

In a further embodiment of the present invention the magnetic field strength of the protection system may be enhanced using flux compression as discussed in Griffin, A. et al [2010]. Flux compression may be activated by the crushing of one or more hollow conductive structures through which magnetic flux permeates. Advantageously, an incoming projectile that crushes the hollow electrically conductive shells containing magnetic flux and automatically activates flux compression. Alternatively flux compression is activated by a signal from a sensor. The signal being activated in response to an incoming projectile sensed by the sensor.

In a further embodiment of the present invention additional impact resistance can be conferred to the vehicle protection system from eddy current braking.

It should be understood that the above description is merely exemplary and that there are various embodiments of the present invention that may be devised, mutatis mutandis, and that the features described in the above-described embodiments, and those not described herein, may be used separately or in any suitable combination (e.g., various types of particles composing the MPF can be used, including in combination); and the invention can be devised in accordance with embodiments not necessarily described above.