NZ516932A

NZ516932A - Propulsion system based on Kepler's laws of planetary motion

Info

Publication number: NZ516932A
Application number: NZ51693202A
Authority: NZ
Inventors: Thomas Alexander Robert Davis
Original assignee: Thomas Alexander Robert Harrie
Priority date: 2002-07-25
Filing date: 2002-07-25
Publication date: 2004-09-24
Also published as: WO2004011802A1; AU2003281735A1

Abstract

A method of propelling an object based on Kepler's laws of planetary motion. The object includes a thrust post (6) fixed to the object to be propelled, a mass (2), a connecting assembly (4) that freely rotates about the thrust post and which is connected to the mass, and a means for supplying a force to act upon the mass. The method is characterised by the steps of: (a) applying a first force to the mass to ensure that the mass achieves an angular velocity along a path; (b) removing the first force and allowing the mass to continue moving along the path; (c) applying a second force in a different direction to that of the first force to the mass to endure that the mass achieves an angular velocity along a path; (d) removing the second force and allowing the mass to continue to move along the path; and repeating steps (a) to (d) as required to propel the object.

Description

<div class="application article clearfix" id="description"> Intellectual fr°Perty Office of NZ - \ m 2W* PATENTS FORM NO. 5 Fee No. 4: $250.00 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No: 516932 Dated: 25 July 2002 PROPULSION SYSTEM I, Thomas Alexander Robert Harries Davis, a New Zealand citizen of Apartment 20, Waterford Estate, Tisdall Terrace, Hamilton, New Zealand hereby declare the invention for which I pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: 1 James & Wells Ref: 120017/25 VM PROPULSION SYSTEM Technical Field This invention relates to an improved propulsion system. Reference throughout the specification shall now be made to use of the present invention in relation to providing a propulsion system for vehicles. It should be appreciated however that this should not be seen to be a limitation on the present invention in any way as the present invention may be used to move any object to which it can be attached either directly or indirectly in a permanent or temporary manner. Background Art The propelling of objects, in particular vehicles, from one location to another, has been the force behind a multitude of systems, methods and apparata that have been designed through the ages. For wheel based vehicles such as cars, trucks, trains etc. the internal combustion engine fuelled by either petrol or diesel and either a manual or automatic gearbox, is the most common propulsion system available today. The twentieth century saw a revolutionary step forward for propulsion systems with the advent of the jet engine and with the design and introduction of highly efficient electric motors. Some vehicles such as large ships or submarines make use of nuclear reactors to provide them with the energy for their propulsion systems. The twentieth century also saw major developments in the field of rocketry, the use of rocke of a warhead to a military target, to the propelling of a -1 JUN 2.W* 2 James & Wells Ref: 120017/25 VM space vehicle into orbit and ultimately to the moon. Currently liquid and solid fuel based rockets are the only propulsion system available to transport a payload from the earth's surface to a point and speed where the earth's gravitational field will not cause the payload to fall back to ground. Whilst current rocket systems achieve their objective they do have significant drawbacks. One significant drawback with current rocket systems is that an immense amount of fuel is needed to propel a vehicle into orbit. Current rocket systems are only able to carry a 5% payload i.e.: they are 95% fuel. This is not only highly inefficient it is also extremely expensive and therefore puts the use of rockets out of reach to all but the most affluent of societies. Another significant drawback with this type of propulsion system is that the vast majority of the fuel is expended before the vehicle achieves an orbit and therefore any further propulsion of the vehicle will be limited. Due to the fuel constraints long distance space travel, particularly where the transportation of a large payload is desired, is currently not feasible. What is required is an alternative propulsion system that will not only allow for a larger payload to be carried but is also more fuel efficient and ideally would contain some level of propellant recycling. A number of previous attempts have been made to overcome these issues by developing a form of drive using centrifugal/centripetal forces. These systems attempt to make use of Kepler's Second Law however they all ignore Kepler's Third Law as they have assumed that if the Second Law was reversed so that the planetary mass went fast when it was meant to go slow and slow when it was meant to go fast, a considerable centrifugal force would develop in the semi-circle of InteHectual Pr°Perty Office of NZ 3 James & Wells Ref: 120017/25 VM -1 JUN 200*1 the orbit in which the mass went fast. They believed that this force acting on the driving axle would give forward motion to a vehicle attached to the axle. However, once Kepler's Third Law is taken into consideration it can be seen that this assumption was incorrect as Kepler's Third Law proves that no overall thrust would be 5 developed in any direction as the ratio of the velocity to the distance of any revolving mass from the centre of any circle is a constant. Examples of this can be seen in US Patent No. 4784006, 4744259, and 4631971 to name but a few. All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinence of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. disclosure of invention According to one aspect of the present invention there is provided a method of propelling an object, wherein the object includes a thrust post fixed to the object to be propelled, and '^teWectual Property Office of NZ a mass, and "' JUN 2004 received 4 James & Wells Ref: 120017/25 VM a connecting assembly that freely rotates about the thrust post and which is connected to the mass, and a means for supplying a force to enact upon the mass, characterised by the steps of a) applying a first force to the mass to ensure that the mass achieves an angular velocity along a path, and b) removing the first force and allowing the mass to continue moving along the path, and c) applying a second force, in a different direction to that of the first force, to the mass to ensure that the mass achieves an angular velocity along a path, and d) removing the second force and allowing the mass to continue moving along the path, and e) repeating steps a) to d) as required to propel the object. Within the present specification the terms "propelling", "to be propelled" and "to propel" should be understood to mean to drive or push in order to cause an object to move forwards. Also within the present specification the term "force" should be understood to mean a dynamic influence that changes an object from a state of rest to one of motion or changes its rate of motion. In preferred embodiments of the present invention the force is provided to the mass by the controlled expulsion of a propellant from the mass or from an article associated with the mass. Intellectual Property Office of NZ - 1 JUN 2004 5 It should be appreciated however that in some embodiments of the present invention the force can be provided in an alternative manner where there is no direct physical contact with the mass, such as by magnetic induction for example. It should also be appreciated that within the present specification the term "mass" should be understood to mean a coherent body of matter. It should be understood that the propulsive thrust generated by the present invention is based upon Kepler's Three Laws of Planetary Motion. 1. The orbits of planets are elliptical with the sun at one focus of the ellipse. 2. Each planet revolves around the sun so that an imaginary line (a radius vector) connecting the planet to the sun sweeps out equal areas in equal amounts of time. 3. The ratio of the square of each planet's sidereal period to the cube of its distance from the sun is constant for all the planets. Kepler's Laws established that centrifugal and centripetal forces of considerable magnitude are held in continuous check to stabilise the motion of the planets. These forces are in accordance with the following formula: T? 2 . F = mv - r In preferred embodiments of the present invention a mass is connected to a radial arm which freely rotates about a thrust post that is secured to the object to be propelled. Also within the present specification the term "path" should be understood to mean a course or direction transcribed by the angular movement of the mass about a fixed centrepoint. Intellectual Property Office of NZ - 1 JUN 2004 6 It should be appreciated that within preferred embodiments of the present invention the centrepoint of the locus will be the centrepoint of the thrust post. It should be understood that in some preferred embodiments of the present invention there are a plurality of radial arms that can freely rotate about at least one thrust post, each connected to a mass. It should be appreciated however that this should not be seen to be a limitation on the present invention in any way as in other embodiments the association of a mass to the object to be propelled can be in any form that allows the mass to freely rotate around at least one point on the object to be propelled. According to another aspect of the present invention there is provided a propulsion system, including Intellectual Prop Office of NZ a radial arm connected to the mass, and a thrust post that is secured to the object to be propelled and about which the mass and radial arm can freely rotate, characterised in that the propulsion system is configured so that force generated by the rotational movement of the mass about the thrust post will be transferred from the mass to the thrust post via the radial arm in order that the force is used to propel the object in a desired direction, when the propulsion system is operated in accordance with the method claimed in any one of claims 1 to 6. It should be appreciated that in some preferred embodiments of the present invention a set of gimbals is located between the thrust post and the radial arm in order that the direction of the force on the thrust post may be adjusted if desired. a mass, and - 1 JUN 2004 7 James & Wells Ref: 120017/25 VM It should also be understood that in some preferred embodiments of the present invention a set of gimbals is located between the mass and the radial arm in order that the direction of the propellant may be adjusted from being perpendicular to the axis of the radial arm if desired. 5 In embodiments where one or more set of gimbals are fitted the controlled altering of the angle of the developed thrust against the thrust post can alter the direction of travel or the velocity of the object to which the propulsion system is attached. Also in preferred embodiments of the present invention the radial arm contains at least one channel through which the propellant can travel. 10 It should be noted however that this should not be seen to be a limitation on the present invention as in some embodiments a propellant channel can be affixed to the outer surface of the radial arm or may be connected separately between the propellant exit aperture and the propellant source. It should be appreciated that the distal end of the channel is configured as a propellant 15 exit aperture through which the propellant leaves the channel. Hence, the orientation of the aperture with respect to the axis of the radial arm will determine the direction in which the force is enacted. Also within preferred embodiments of the present invention the thrust post assembly contains at least one set of slip rings that can be used to control the time during which 20 the propellant leaves a propellant exit aperture and through which propellant exit aperture the propellant is expelled. Once again this should not be seen to be a limitation on the present invention in any way as in other embodiments different forms of control for the direction and release of the propellant jet stream may be used. Intellectual Property Office of NZ -1 JUN 2004 James & Wells Ref: 120017/25 VM It should be appreciated that in the normal operation of the present invention the propellant is expelled from a propellant exit aperture in a controlled stream in which the initial propellant pressure, flow rate and duration of flow are all controlled. This should also not be seen to be a limitation on the present invention in any way as in 5 other embodiments the propellant may be expelled in a manner other than as a constant stream, one example of this would be as a pulse or series of pulses. In preferred embodiments of the present invention the propellant used will be steam or any other material that can be changed from a liquid to a gaseous or vapour form and then returned to a liquid. 10 By using steam or a material with similar properties it is envisaged that the propellant will be changed from its liquid to vapour (or gaseous) form and be expelled from the propellant exit aperture in this form, once expelled the material will re-condense to its liquid form so that it can be collected and returned to a reservoir in order for it to be reused. 15 It is envisaged that in preferred embodiments of the present invention that make use of steam, the condensate formed when the steam cools back to a liquid phase will be drained from the drive assembly via at least one drain hole by the use of a vacuum pump. It should be appreciated that in embodiments of the present invention that remain 20 within the earth's gravitational field the condensate may be gravity fed to a pump chamber from whence it can be pumped back to a reservoir from where it can be withdrawn when needed. In embodiments of the present invention where the force of gravity cannot be relied upon, such as in space travel, a vacuum or low pressure pump is needed to help 25 remove the condensate from the drive assembly and send it to a reservoir so that it is InteHectual Property Office of NZ - 1 JUN 2004 9 James & Wells Ref: 120017/25 VM available for reuse. Once again this should not be seen to be a limitation on the present invention as in other embodiments other methods of removing the condensate from the drive assembly can be used. 5 It should be understood that the use of steam ( or materials with similar phase-change characteristics) as a propellant should not be seen to be a limitation on the present invention as in other embodiments where the recycling of propellant is not a requirement then any suitable material could be used as a propellant. Examples of this would be liquids or compressed gases. 10 It should also be appreciated that in preferred embodiments of the present invention the overall direction of movement produced by the propulsion system can be adjusted by altering the position of the slip rings on the thrust post assembly. It is also envisaged that an object propelled by the present invention can be slowed or stopped by reversing the position of the slip rings so that the overall force produced by 15 the present invention is in the opposite direction. However this should not be seen as limiting the invention in any way as in some embodiments the propulsion system can be rotated to alter the direction in which the overall force is applied. It should be appreciated that in embodiments where a plurality of mass/radial arm 20 assemblies are fitted, the relative timing of the movement of the assemblies can be adjusted so as to control the propulsion system "thrust" characteristics. It is envisaged that the characteristics can be adjusted to anywhere between all the masses moving through the direction of travel simultaneously - to give a large "pulsed" acceleration, to a position where the overall effect is a substantially smoothed 25 propulsion. Intellectual Property Office of NZ -1 JUN 2004 10 James & Wells Ref: 120017/25 VM From the foregoing description it can clearly be seen that the present invention has some significant advantages over any of the currently available systems. One great advantage is that due to the propellant being recycled a far smaller quantity of propellant is needed as the only excess volume of propellant necessary over what is 5 used (before the initial propellant is recycled and available for use again) is a volume of propellant that is stored to replace any lost due to leakages. Another great advantage of the present invention is that due to the recycling of the propellant, the propulsion system can be used to undertake far longer journeys than would otherwise be achievable. This has particular relevance to space travel as it will 10 now make long distance space travel a viable proposition. This is also a great advantage for other craft such as ocean going vessels (ships, submarines, etc) and for other crafts such as long distance aircraft, as they would no longer need to carry such huge quantities of fuel which will reduce costs and improve their safety. 15 Another great advantage is that the present invention may be used with various types of power plant that can provide a source of propellant, these can include plants powered by conventional fuels such as petrol or diesel, or even solar energy in some applications, but it is envisaged that a suitably sized nuclear generator would be used -certainly for long distance space travel. 20 Another advantage of the present invention is that due to the propellant system being a closed system it is far more environmentally friendly as no propellant is discharged to the atmosphere during take-off (or during use if it is to be used for a terrestrial or marine application). One significant advantage of the present invention over the current systems available is 25 that a far greater payload would be able to be carried. InteHectual Propertv Office of NZ -1 JUN 2004 it James & Wells Ref: 120017/25 VM Brief description of Drawings Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: 5 Figure 1 is a diagrammatical representation of a plan view of one preferred embodiment of the present invention; Figure 2 is a diagrammatical representation of the drive unit of figure 1 showing the drive and free spin areas of the mass's rotation. Figure 3 is a diagrammatical representation of a graph showing the curve 10 produced by the acceleration of a mass over a distance. Best Modes for Carrying out the Invention With reference to the figures there is illustrated a propulsion system generally indicated by arrow 1. The rotational motion of the mass 2 is restricted to the forward semi-circle A-A of the 15 drive assembly 3. This has the effect of concentrating the developed thrust in a generally forward direction. A mass 2 is attached to a radial arm 4 which is in turn attached by a frictionless sleeve 5 to a thrust post 6. The sleeve 5 is able to be freely rotated around the thrust post 6 if desired, with 20 minimal or no friction between the sleeve 5 and the thrust post 6. The clockwise and anti-clockwise propellant channels 7 and 8 are located through the length of the radial arm 4 and exit the leading and trailing faces of the mass 2 via the propellant exit apertures 9 and 10 respectively. Intellectual Property Office of NZ - 1 JUN 2004 12 James & Wells Ref: 120017/25 VM receded The operation of the propulsion system is as follows: START UP The mass is moved to a position in the drive unit either between B and C or D and E, it does not matter which. 5 It is preferable to have the mass closer to B than C or E than D as this will allow for a longer thrust time before the propellant will be shut off. For this example we will assume that the mass 2 is moved to point B. The mass 2 is rotationally accelerated towards point C by the controlled discharge of a propellant along propellant conduit 7 and out from the mass 2 through the propellant 10 discharge aperture 9. When the centre line of the mass 2 reaches point C the jet stream of propellant is turned off. Due to the forces enacting upon it the mass 2 will continue to rotate around the thrust post 6 in a clockwise direction. 15 When the centre line of the mass 2 passes point D a volume of propellant travels along the propellant conduit 8 and exits as a jet stream of propellant from the propellant exit aperture 10. This stream of propellant will cause the mass to decelerate and eventually stop at point H. 20 The jet stream of propellant exiting from the propellant exit aperture 10 will continue until the centre line of the mass passes point D in an anti-clockwise direction. At this point the propellant flow is shut off. Once again due to the forces enacting upon it the mass 2 will continue to rotate, this intellectual Property Office of NZ - 1 JUN 2004 13 James & Wells Ref: 120017/25 VM time in an anti-clockwise direction around the thrust post 6. When the centre line of the mass passes point C propellant will once again pass along the propellant conduit 7 and exit the mass 2 at the propellant exit aperture 9. The jet stream of propellant from the propellant aperture 9 will decelerate and stop the 5 mass 2 at point G on the drive unit, the force provided by this stream of propellant will then cause the mass 2 to once again move in a clockwise direction around the thrust post 6, This will complete one oscillation of the drive assembly. Under normal operating conditions, subsequent oscillations of the mass 2 will be from 10 point G to point H unless a change in direction is required. The forces produced by the oscillating action of the mass 2 and radial arm 4 assembly will cause the propulsion system 1 and hence the object to which it is affixed to be propelled in direction F. If only one radial arm 4 and mass 2 are used, the movement of the object will be 15 "wobbly" as the instantaneous force produced by the accelerating or decelerating mass 2 will have a sideways as well as a forwards component as the resultant force produced at any instant is directed perpendicularly to the tangent the mass is transcribing at that instant in time. In practice is has been found that once a few oscillations have taken place, even at a 20 repetition rate as low as one oscillation per second, that the wobbling effect is negligible. Therefore each radial arm/mass assembly 4,2 needs to have an equivalent radial arm/mass assembly 4,2 that is operating in a mirrored relationship about the line F-R. This action will cancel the sideways forces and summate the forwards forces, i.e.: Intellectual Property Office of NZ 14 James & Wells Ref: 120017/25 VM -1 JUN 2004 when one radial arm/mass assembly is at point C, the other will be at point D and travelling in the opposite direction to the assembly at point C. The amount of thrust produced by the propulsion system can be adjusted in a number of ways. 5 The overall thrust is dependent upon the size of the mass 2, the mean velocity of the mass 2 and the radius of the mass 2 from the thrust post 6. Therefore the amount of thrust can easily be adjusted by altering the length of the radial arm 4 and/or altering the mean velocity of the mass 2 during its oscillating cycle. The mean velocity of the mass 2 can be adjusted by altering the force produced by the 10 propellant applied to drive the mass 2. This could easily be achieved by altering the flowrate of the propellant from the propellant exit apertures 9 and 10. The mean velocity of the mass 2 can also be adjusted by altering the position of point C and point D with respect to point B and point E respectively. 15 The closer point C is to point B and point D is to point E then the greater the "free spin" time of the mass 2 as it is not under power between point D and point C. Hence the closer point C is to point D then the longer time the mass 2 is under the effect of a driving force produced by the propellant and this will therefore increase its means velocity. 20 The forward thrust achieved during an oscillation is, as stated previously, dependant on the mean velocity of the mass 2. * 2 2 Since F = mv + r where F = thrust, m = mass 2, v = velocity squared and r = the distance of the mass 2 from the thrust post 4, and both the mass and the radius (radial arm length) are in most embodiments of the present invention kept constant, then the Intellectual Property Office of NZ 1 mil* inrw James & Wells Ref: 120017/25 VM - 1 JUN 2004 rr t IVED thrust is proportional to v2 i.e.: F oc v2 therefore F oc a where a = the instantaneous acceleration of the mass 2. Figure 3 shows a typical acceleration graph where D is the distance from H to D or from G to C (we will assume H to D for this explanation, however it is equally 5 applicable for G to C) and v is the velocity of the mass 2. The units are arbitrary as this graph is a generalised representation and is not intended to provide data but only to show the relationship of the amount of thrust produced to the position of the accelerating mass 2. What the graph clearly indicates is that when the mass 2 is closest to point H the 10 resultant thrust is zero. As the mass 2 accelerates towards point D the thrust increases exponentially. Therefore, at points where the sideways component of the resultant force is greater than the forwards component, the resultant force generated by the mass 2 is minimal compared to points where the forwards component is greater than the sideways component. 15 For example: at V* of the distance from H to D the force is 9 units, most of which is the sideways component. Whereas at 3/4 of the distance from H to D the force is 81 units, most of which is the forwards component. This clearly demonstrates that the summation of the thrust produced by a single mass 2 during its acceleration from point H to point D has a far greater forward component 20 than its sideways component. The direction of point F, i.e.: the direction of movement, is adjusted by moving both of points C and D closer to either point B or point E as the direction of movement will be along the imaginary line transcribed from the centre point of the thrust post 6 through the mid point on the arc between point C and point D. Line A-A will automatically 25 move so that it remains perpendicular to the direction of movement, i.e.: point F or point R. Intellectual Property Office of NZ - 1 JUN 2004 16 James & Wells Ref: 120017/25 VM bpCEIVED When it is desired to slow or stop the vehicle/object to which the propulsion system is attached, the free-spin sector (C-D) and drive sectors (B-D, D-E) are placed into the rearward semi-circle of the drive assembly 3 so as to cause the developed thrust to be in the reverse direction to the present direction of movement i.e.: towards point R. 5 The object to which the propulsion system is attached will then be caused to decelerate. If the thrust is continued past the point at which the object stops it will cause the object to move back in the direction from whence it came. Any desired change of direction of the developed thrust can be easily achieved by altering the position of the slip-rings (not shown) around the thrust post 6, as it is the 10 slip-rings that control the timing and direction of the firing of the propellant. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims. Intellectual Property Office of NZ - 1 JUN 2004 17 James & Wells Ref: 120017/25 VM </div>

Claims

<div class="application article clearfix printTableText" id="claims"> WHAT I CLAIM IS:

1. A method of propelling an object, wherein the object includes a thrust post fixed to the object to be propelled, and a mass, and a connecting assembly that freely rotates about the thrust post and which is connected to the mass, and a means for supplying a force to enact upon the mass, the method characterised by the steps of a) applying a first force to the mass to ensure that the mass achieves an angular velocity along a path, and b) removing the first force and allowing the mass to continue moving along the path, and c) applying a second force in a different direction to that of the first force to the mass to ensure that the mass achieves an angular velocity along a path, and d) removing the second force and allowing the mass to continue to move along the path, and repeating steps a) to d) as required to propel the object.

2. A method of propelling an object as claimed in claim 1 wherein the force is provided to the mass by the controlled expulsion of a propellant from the mass. IniaJL'Jtual P-v^'srLy O'y'f-p O'' Z. 2 2 J'JL O ,;T,8 - i; \/ ' James & Wells Ref: 120017/25 VM

A method of propelling an object as claimed in claim 1 wherein the force is provided to the mass by the controlled expulsion of a propellant from an article connected to the mass.

A method of propelling an object as claimed in claim 1 wherein the force is provided to the mass without any direct physical contact with the mass.

A method of propelling an object as claimed in claim 4 wherein the force is provided by magnetic induction.

A method of propelling an object as claimed in any previous claim wherein the timing of the application of a force to the mass is governed via a set of slip rings.

A method of propelling an object as claimed in any previous claim wherein the characteristics of the developed thrust are altered by a use of a set of gimbals.

A propulsion system for an object, including a mass, and a radial arm connected to the mass, and a thrust post that is secured to the object to be propelled and about which the mass and radial arm can freely rotate, characterised in that the propulsion system is configured so that force generated by the rotational movement of the mass about the thrust post is transferred from the mass to the thrust post via the radial arm in order that the force is used to propel the object in a desired direction, when the propulsion system is operated in accordance with the method claimed in any one of claims 1 to 7. -x,,; rv. .;::y omxh o* mx if 2 2 lames &-Wells Ref: 120017/25 VM

A propulsion system as claimed in claim 8 wherein a set of gimbals is located between the thrust post and the radial arm.

A propulsion system as claimed in either claim 8 or claim 9 wherein a set of gimbals is located between the mass and the radial arm.

A propulsion system as claimed in any of claims 8 to 10 in which a plurality of radial arms are fitted and which freely rotate about at least one thrust post, wherein each radial arm is connected to a separate mass.

A propulsion system as claimed in any of claims 8 to 11 wherein the radial arm contains at least one propellant channel which ends as a propellant exit aperture and through which a propellant can travel.

A propulsion system as claimed in any of claims 8 to 11 wherein a propellant channel which ends as a propellant exit aperture is affixed between the mass and the source of a propellant without passing through the radial arm.

A propulsion system as claimed in any of claims 8 to 13 wherein the thrust post contains a set of slip rings configured to control the time during which a propellant leaves a propellant exit aperture and through which propellant exit aperture a propellant is expelled.

A propulsion system as claimed in any of claims 8 to 14 configured to expel propellant from a propellant exit aperture in a controlled stream in which the initial propellant pressure, flowrate and duration of flow are all controlled.

A propulsion system as claimed in any of claims 8 to 14 configured to expel propellant from a propellant exit aperture in a pulsed manner.

A propulsion system as claimed in any of claims 12 to 16 wherein the propellant is steam. 7--.—- -

18. A propulsion system as claimed in any of claims 12 to 16 in which the propellant is a material that can be changed from a liquid to a gaseous or vapour phase and then returned to a liquid.

19. A method of propelling an object as claimed in either of claims 2 or 3 wherein the propulsion system is configured so that the propellant is a) changed from its liquid phase to a vapour phase in order to be expelled in this phase, and b) once expelled the material recondenses to its liquid phase, and c) collected and returned to a reservoir in order for it to be available for reuse.

20. A method of propelling an object as claimed in claim 19 wherein the condensate formed when the vapour cools back to a liquid phase is drained from the propulsion system via at least one drain hole by the use of a vacuum pump.

21. A method of propelling an object as claimed in claim 19 wherein the condensate formed when the vapour cools back to a liquid phase is drained from the propulsion system via at least one drain hole under the effects of gravity.

22. A method of propelling an object as claimed in either of claims 2 or 3 or in any of claims 19 to 21 wherein the propellant is discarded once it has exited from the propulsion system.

23. A method of propelling an object as claimed in any of claims 1 to 7 or claims 19 to 22 wherein the propulsion system is configured so that the overall direction of movement of the object connected to the propulsion system is 21 adjusted by altering the position of the path along which the mass moves in relation to the overall position of the propulsion system. A method of propelling an object as claimed in claim 6 wherein the propulsion system is configured to be slowed or stopped by altering the position of the slip rings on the thrust post to a position where the overall force produced by the propulsion system is in a substantially opposite direction to the initial direction. A method of propelling an object, substantially as herein described, with reference to and as illustrated by the accompanying drawings. A propulsion system substantially as herein described, with reference to and as illustrated by the accompanying drawings. THOMAS ALEXANDER ROBERT HARRIES DAVIS by his Attorneys ■TAMES & WELLS </div>