GB2267142A - Electromagnetic rail launcher armatures - Google Patents

Abstract

This invention is concerned with improvements in the efficiency of Electromagnetic Rail Launcher armatures. The armature has two or more electrically conducting solid parts 10 in contact with the rails 11. Electric current flows from the rails to and from the armature between the adjacent rail and armature surfaces 14 and across the or each gap 12 by electric arcing between the conducting solid parts 10. The resulting electromagnetic forces on the armature accelerate it and any attached projectile along the rails. A member of insulating or high resistivity material located forward of the armature closes the or each gap 12 to confine the electric arcing across the smallest gap spacing to minimise the arc voltage and armature resistive losses. Exhaust chambers for the confinement and/or cooling of arcing erosion products are provided at the rear of the armature. <IMAGE>

Description

ELECTROMAGNETIC RAIL LAUNCHER ARMATURES This invention relates to improvements in the performance of Electromagnetic Rail Launchers by increasing their armature electrical efficiency and reducing the armature mass.

Electromagnetic Rail Launchers consist of stationary parallel rails, rail insulators and a moving armature positioned between them such that electric current flows from the end of one rail through the armature and back to the same end of the opposite rail. The resultant electromagnetic forces produced in the armature accelerate the armature and if present a projectile associated with it in the direction away from the ends of the rails supplied with current. To achieve a high conversion efficiency from power supply electrical energy to projectile kinetic energy requires the efficient transfer of current from the rails to and through the armature with minimum armature resistance and mass and without significant damage due to electric arcing and erosion at the rail and rail insulator surfaces.

Rail Launchers in present use have solid, plasma or hybrid armatures. Solid armatures are usually of solid metal and therefore have a relatively high mass and also have difficulty in maintaining a low resistivity metal-to-metal contact with the rail at high velocities as transition to arcing occurs.

Current conduction through a plasma armature is obtained by establishing electric arcs between the rails which result in a high armature resistance and significant erosion damage. The latter can also result in electrical breakdown between the rails behind the armature due to contamination by arcing erosion products. The hybrid armature is in principle a solid armature with small gaps between the rails and armature contact surfaces across which current flows by electric arcing. However experiments shew that the hybrid armature resistance is almost as high as that of plasma armatures and they also can have a high armature mass. Thus the efficiency of present Rail Launchers is significantly reduced by the use of armatures having a high electrical resistance and/or relatively high mass.

According to the present invention there is provided an Electromagnetic Rail Launcher having an armature intended to be accelerated between the stationary parallel rails of an electromagnetic rail launcher wherein the armature comprises electrically conducting solid parts providing one or more gaps therebetween, said parts being positioned such that, in use, electric current flowing from and to adjacent ends of the rails via the armature passes directly between adjacent rail/armature surfaces and by electric arcing across the or each gap.

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a representation of the present invention shewing in cross-section a Rail Launcher having an armature with two electrically conducting solid parts and one gap between them.

Figure 2 is an end view of the Rail Launcher similar to that described in Figure 1.

Figure 3 shews in cross-section the armature gap region with the forward end of gap closed.

Figure 4 shews in cross-section an alternative armature gap region with forward arc chamber.

Figure 5 shews in cross-section part of an armature with exhaust chamber.

Figure 6 shews in cross-section part of an armature with the gap sides closed.

Figure 7 shews in cross-section an armature with two parts, contoured to provide an exhaust chamber closed to the rear and a gap closed forwardly.

Figure 8 shews in cross-section a mainly circular armature with two parts contoured to provide an exhaust chamber closed laterally.

Figure 9 shews in cross-section two parts of an armature with rear projectile region forming an exhaust chamber closed to the rear.

Figure 10 shews a cross-section through an armature similar to that shewn in Figure 9 with an exhaust chamber closed laterally.

Figure 11 shews in cross-section an armature with two parts surrounding a cylindrical projectile.

Figure 12 is an end view of an armature similar to that shewn in Figure 11.

Figure 13 is a representation of the present invention shewing in cross-section a Rail Launcher having an armature with structural supports providing pressure contact at the rail/armature surfaces.

Referring to the drawings, Figure 1 shews in cross-section an Electromagnetic Rail Launcher having an armature with two electrically conducting solid parts 10 in contact with the rails 11 at the contact surfaces 14. Electric current flows as indicated by the arrows 15 from the rails to and from the armature between the adjacent rail and armature surfaces 14 and across the gap 12 by electric arcing as indicated by the arrow 13. The resulting electromagnetic forces on the armature accelerate it and any attached projectile (not shewn) in the direction of the arrow 16.

Figure 2 shews an Electromagnetic Rail Launcher viewed from behind the armature in the forward direction (with respect to the direction of motion). The internal surfaces of the rails 11 and the rail insulators 20 form an internal circular space or bore through which the armature conducting solid parts 10 are accelerated. The gap 12 extends over the width of the armature conducting solid parts 10 across which the armature current flows by electric arcing as indicated by the arrows 13.

Alternatively a rectangular bore can be used in some applications.

Figure 3 shews the gap region of an armature in cross-section with a member 30 of insulating or high resistivity material closing the forward end 31 of the gap 12. This and the electromagnetic forces on the arc channels confine the current flow 13 mainly to the forward part of the gap where the gap length is small. Arc erosion products are mainly expelled to the rear of the armature from gap 12.

Figure 4 is an alternative method of closing the gap 12 in which a member 42 of insulating or high resistivity material forms a closed arc chamber 40 adjacent to the forward surfaces of the conducting solid parts 10 and communicating with gap 12. This allows current flow 41 to occur mainly through the arc chamber 40 and provides additional containment of the explosive arc pressure and erosion products.

Figure 5 shews in cross-section part of an armature in which the conducting solid parts 10 are shaped behind the gap 12 to provide an exhaust chamber 50 in which arc erosion products can expand and cool before moving into the rail bore behind the armature. The member 52 of insulating or high resistivity material has openings 51 such that the volume and internal surfaces of the open exhaust chamber 50 are increased. Alternatively member 52 without openings 51 can be used to close the exhaust chamber.

Figure 6 shews a cross-section through the exhaust chamber of an armature similar to that shewn in Figure 5 viewed in the forward direction. Members 61 of insulating or high resistivity material close the sides of the exhaust chamber 60 and are positioned in a rectangular or circular bore by being in contact with the rail insulator surfaces (see insulators 20 in Fig 2) at location 63. The combination of a member such as 52 with openings 51 in Figure 5 with members 61 in Figure 6 enables a larger exhaust chamber open to the rear to be achieved. Alternatively member 52 in Figure 5 without openings 51 can be used to close the exhaust chamber in Figure 6.

Figure 7 shews in cross-section an armature having conducting solid parts 10 whose surfaces facing gap 12 are contoured such that they form an exhaust chamber 72 which is closed at the rear by the rear portions 70 of the conducting solid parts 10. The latter have surface insulation 71 to confine current flow 13 to the gap 12. The assembly is split at the insulating layers 74.

Additionally, as shewn, the parts 10 can be contoured to provide forward portions 73 having surface insulation 74 which forwardly close the gap 12.

Figure 8 shews a cross-section through the exhaust chamber of an armature similar to that shewn in Figure 7 viewed in the forward direction. The side portions 80 of the conducting solid parts 10 with surface insulation 81 close the sides of the exhaust chamber 72. The outer insulation 83 of the portions 80 are positioned in the circular bore 82 near the mid-plane where they are in contact with the rail insulators (refer insulators 20 in Figure 2) such that the limited movement of the conducting parts 10 required to maintain pressure contact at the rail/armature surfaces 14 is possible. The combination of portions such as 70 and 71 in Figure 7 with portions 80 and 81 in Figure 8 enable a completely enclosed exhaust chamber to be achieved.Alternatively an exhaust chamber open to the rear can be obtained from a combination of the portions 80 in Figure 8 with conducting solid parts 10 such as in Figure 5. The assembly is split at the insulating layers 81.

Figure 9 shews in cross-section part of an armature having two conducting solid parts 90 and a central conducting solid part 91 being the rear region of a projectile (not shewn). These three parts 90 and 91 are separated by two gaps 92 in series. The exhaust chamber 95 is closed to the rear by portions 93 of the conducting solid parts 90 with insulated surfaces 94.

Figure 10 shews a cross-section through the exhaust chamber of an armature similar to that shewn in Figure 9 viewed in the forward direction. The central solid conducting part 91 is the rear region of a cylindrical projectile centred on axis 102. The side portions 100 of the conducting solid parts 90 with surface insulation 101 close the sides of the exhaust chamber (not shewn). Exhaust chambers completely enclosed or open to the rear can be obtained with the armature in Figure 10 in a similar manner to that discussed above with respect to Figure 8. The armature excluding the projectile 91 is split at the insulation layers 101.

Figure 11 shews in cross-section an electromagnetic rail launcher with rails 11 and an armature having two conducting solid parts 110 surrounding and insulated from a cylindrical projectile 111 extending both forward of and to the rear of the armature. The two conducting solid parts 110 are separated by two gaps 112 in parallel located on the mid-plane 115 on either side of the projectile 111. Insulation 113 between the solid conducting parts 110 and the cylindrical projectile 111 ensures that current flow 13 is across the gaps 112. The assembly excluding the projectile 111 is split along the mid-plane 115.

Figure 1 2 shews a view from behind an armature similar to that shewn in Figure 11 viewed in the forward direction., The cylindrical projectile 111 and the rail surfaces are centred on the axis 1 20.

Open or completely enclosed exhaust chambers can be achieved as discussed above with reference to Figures 6 and 8. The assembly excluding the projectile 111 is split along the mid-plane 115.

Figure 13 shews in cross-section an electromagnetic rail launcher with rails 11 and an armature having two conducting solid parts 10 with rear and forward supports 132 and 134 respectively, made of insulating or high resistivity material. The supports 132 and 134 are in compression to provide pressure contact at the adjacent rail/armature surfaces 14. The forward support 134 which can be part of the projectile 137 provides the necessary closure to the forward part of gap 12 or alternatively can form an arc chamber (not shewn) as in Figure 4. The rear support 132 forms extensions 131 to the exhaust chamber 130 which can be closed at the rear by member 133. A completely enclosed exhaust chamber can also be achieved as discussed above with reference to Figures 6 and 8. To improve contact stability at the rail/armature surfaces 14 stabilisers 136 are provided mounted on support arms 135. The stabilisers 136 also seal the space between the armature and bore surfaces to prevent arcing erosion products leaking forward of the armature. To withstand the large electromagnetic and thermal forces that are usual in rail launchers the armature conducting solid parts 110 and insulating or high resistivity supports 132 and 134 can be arranged as a combined assembly which, nevertheless, allows movement of the armature conducting solid parts 110 as required to maintain pressure contact at the adjacent rail/armature surfaces 14.

Claims (18)

1. An armature intended to be accelerated between the stationary parallel rails of an electromagnetic rail launcher wherein the armature comprises electrically conducting solid parts providing one or more gaps therebetween, said parts being positioned such that, in use, electric current flowing from and to adjacent ends of the rails via the armature passes directly between adjacent rail/armature surfaces and by electric arcing across the or each gap.

2. An armature as claimed in claim 1 wherein the or each gap is closed forwardly (relative to the intended direction of movement of the armature) of the said parts.

3. An armature as claimed in claim 2 wherein the forward closure comprises at least one member of electrically insulating or high resistive material.

4. An armature as claimed in claim 3 wherein the forward closure is contoured to provide an arc chamber.

5. An armature as claimed in any one of claims 2 to 4 wherein at least one member of electrically insulating or high resistivity material is provided on each side of the or each gap to laterally close said gap or gaps.

6. An armature as claimed in any one of claims 2 to 5 wherein the solid parts are contoured such that the or each gap diverges rearwardly to form an exhaust chamber for arc erosion products.

7. An- armature as claimed in claim 6 wherein at least one member of electrically insulating or high resistivity material is provided rearwardly of the or each exhaust chamber.

8. An armature as claimed in claim 7 wherein said member(s) provides a rearward extension of the or each exhaust chamber.

9. An armature as claimed in claim 7 wherein said member(s) provides rearward closure of the or each exhaust chamber.

10. An armature as claimed in claim 6 when dependent on claims 2 to 4 wherein the conducting solid parts are further contoured such that the or each exhaust chamber is laterally closed by material of the solid parts in association with insulating layers.

11. An armature as claimed in claim 6 or claim 10 wherein the conducting solid parts are further contoured such that the or each exhaust chamber is rearwardly closed by material of the solid parts in association with insulating layers.

12. An armature as claimed in claim 6 or claim 10 wherein the conducting solid parts are further contoured such that the or each gap is forwardly closed by material of the solid parts in association with insulating layers.

13. An armature as claimed in claim 6 or claim 11 wherein one of the electrically conducting solid parts is provided by the rear of an associated projectile.

14. An armature as claimed in claim 13 wherein said projectile rear is positioned between other of the conducting solid parts such that a pair of gaps is defined.

15. An armature as claimed in claim 2 wherein the electrically conducting solid parts are contoured to provide an axially extending passage with, extending laterally therefrom, diametrically opposed gaps, the passageway accommodating the insulated rearwardly extending portion of an associated projectile.

1 6. An armature as claimed in claims 3, 5 or 7 wherein the or each member acts as a structural support which, in use, maintains pressure contact at the adjacent rail/armature surfaces.

17. An armature as claimed in any preceding claim split such that it divides into discrete parts on discharge from an electromagnetic rail launcher.

18. An armature substantially as described herein and as shewn in the accompanying drawings.