United States Patent (19) 11 Patent Number: 4,966,884 Hilal 45 Date of Patent: Oct. 30, 1990

54 DC POWERED HYBRD COL GUN 4,432,333 2/1984. Kurherr ...... 89/8 EMPLOYING SUPERCONDUCTING FOREIGN PATENT DOCUMENTS ELEMENTS 1332109 6/1963 France ...... 89/7 (75) Inventor: Mohammed A. Hilal, Madison, Wis. Primary Examiner-Stephen C. Bentley (73) Assignee: International Superconductor Corp., Attorney, Agent, or Firm-Herbert Dubno Riverdale, N.Y. 57) ABSTRACT 21) Appl. No.: 300,282 A device and apparatus, consisting of a standard barrel, 22 Filed: Jan. 19, 1989 a superconductive magnet winding wrapped around the 51 Int, C...... F41B 6/00 barrel, a large mass piston and a projectile. This device (52) U.S. C...... 505/1; 89/8; is a direct-current powered hybrid coil gun which oper 124/3; 505/876 ates to accelerate projectiles to high velocity without (58) Field of Search ...... 89/8; 124/3; 310/13; the requirement of gigawatt power pulses. The device 505/876, 1 also lowers the cost of power required per shot and makes possible extended life of the individual parts of 56 References Cited the apparatus. U.S. PATENT DOCUMENTS 2,870,675 l/1959 Salisbury ...... 89/8 18 Claims, 5 Drawing Sheets

U.S. Patent Oct. 30, 1990 Sheet 1 of 5 4,966,884

s

U.S. Patent Oct. 30, 1990 Sheet 2 of 5 4,966.884

U.S. Patent Oct. 30, 1990 Sheet 3 of 5 4,966,884 U.S. Patent Oct. 30, 1990 Sheet 4 of 5 4,966,884 SE||?-JEIS CJELICENNOD

U.S. Patent Oct. 30, 1990 Sheet 5 Of 5 4,966,884

4,966,884 1. 2 decelerate the piston and generate by induction a cur DC POWERED HYBRD COL GUN EMPLOYNG rent pulse for magnetically propelling the projectile; SUPERCONDUCTING ELEMENTS and means for applying a chemical propellant to the pis FIELD OF THE INVENTION ton to drive the piston through the closed-loop portion My present invention relates to direct-current pow of the coil means and the external field, whereby the ered hybrid coil guns employing superconducting coils, current pulse is induced, the closed-loop portion gener ating an external field of axially tapering field strength. and to a method of operating same. The discovery of high critical temperature ceramic BACKGROUND OF THE INVENTION 10 compositions having superconducting properties is of The history of guns and projectiles dates back at least recent origin. Originally, superconductivity was ob several thousand years to the original discovery of gun served in mercury at 4 K. by the Dutch scientist, Heike powder in China. Gunpowder is essentially a mixture of Onnes. solid chemicals comprised of an oxidizing agent plus The term, superconductivity, refers to the property reducing agents capable of being oxidized. If gunpow 15 wherein a normally resistive conductor abruptly loses der is confined in a small space in conjunction with a all resistance to electrical flow at a specific temperature projectile, i.e. a "bullet', and is then detonated, chemi to, called the critical temperature Tc. At this point, the cal energy changes the solids to hot gases almost instan resistivity of the normal conductor becomes zero, and taneously, and the chemical energy is converted to to conductor becomes superconducting. In more recent kinetic energy, causing the projectile to accelerate. 20 times, niobium metal alloys have been used in supercon In yet another version of a gun, the projectile is accel ducting coils at temperatures up to 23 K. It had previ erated by the use of coils situated on a barrel in such a ously been believed that superconductivity above 23 K. manner that the the coils can be energized in turn to was not possible. This belief was based on the theoreti produce an electromagnetic field and thereby acceler cal work of Bardeen, Cooper and Schieffer (BCS theo ate the the projectile. 25 ry-1946) which predicted such a limit. Several theoreti Electromagnetic and coil guns of prior art designs cal proposals were presented in the 1970's, suggesting require gigawatt electric power supplies to operate. The that the critical temperature for superconductivity weight and the complexity of these power supplies could be increased. However, the lack of any early severely limits the potential use of these guns. It is pro discoveries of superconductivity above 23 K. solidified hibitive to use these guns for systems which require low 30 the belief that indeed this temperature could not be weight such as space borne weapons or mobile systems. exceeded. The development of electromagnetic guns has also Thus, in November, 1987, when Bednorz and Miller been hindered by the factor of severe rail erosion. It is announced the discovery of a new ceramic supercon not clear after many year of development whether such ducting compound based on lanthanum, barium, and problems can be overcome. The most advanced rails 35 copper oxides, whose critical temperature for supercon developed to date are limited to a few shots. Yet ductivity was close to 35 K., (G. Bednorz and A. Mil weapon systems employing electromagnetic and coil ler, Z. Phys., B64 189 (1986)), the declaration was guns require that at least a few hundred shots be deliv greeted with considerable scepticism. Nevertheless, by ered without barrel replacement to be satisfactory. the following month, the critical temperature Tc, for the OBJECTS OF THE INVENTION onset of superconductivity was raised to nearly 80 K. by C.W. Chu and coworkers (M. K. Wu, J.R. Ashburn, It is an object of the invention to provide an im C.J. Tang, P.H. Hor, R.L. Meng, L. Gao, Z. J. Huang, proved electromagnetic gun which eliminates the need Y. Q. Wang and C. W. Chu, Phys. Rev. Lett. 58 908 for a gigawatt power supply. (1987). This was achieved by changing the composi I have also to provide a system in which barrel ero 45 tion to yttrium barium copper oxide, approximated by sion and rail damage is considerably lessened and/or nearly completely eliminated, so much so that the usage the formula: of said electromagnetic and coil guns become feasible as Y10 Ba1.8Cu3.0 O6.3 a weapon system. It is a further object to provide a coil gun which does 50 This formula, determined experimentally, is not ex not require the usage of inordinate amounts of powder. actly stoichiometric. It is believed that this lack of spe cific nonstoichiometry contributes most to the onset of SUMMARY OF THE INVENTION superconductivity. The so-called 1:2:3 compound, com These objects are attained in accordance with the posed of Y-Ba-Cu-O atoms, is prepared by the solid invention in a hybrid coil gun which comprises: 55 state reaction of the requisite oxides, vis: a projectile formed with at least one closed-loop electromagnet winding; a piston formed with at least one closed-loop electro magnet winding; It is now established (C.N.Rao et al, Nature, 327 185 means defining at least one barrel receiving the pro (1987)) that high Tc superconductivity in the Y-Ba-Cu jectile and from which the projectile can be electromag O system originates from a compound of stoichiometry: netically propelled; YBa2Cu3O7-9, where “” is a value less than 1.0. This coil means on the barrel having at least a portion compound has the structure of the ideal perovskite, magnetically coupling to the closed-loop winding of the YBa2Cu3O9. Thus, the superconductor YBa2Cu3O7. projectile for magnetically propelling the projectile 65 has about 25% fewer oxygen atoms present in the lattice from the barrel, the coil means comprising a closed-loop as compared to the idealized cubic perovskite structure. portion generating an external field and magnetically This massive oxygen deficiency means that instead of coupling to the closed-loop winding of the piston to the conventional three-dimensional crystalline cubic 4,966,884 3 4. stacking array of the perovskite, a unique layered struc fired at elevated temperatures above about 950 C. The ture results. A loss of even more oxygen atoms in this induced solid state reaction causes the formation of the structure gives rise to the semiconductor YBa2Cu3O6. desired ceramic composition and structure. Further The chain of copper atoms associated with a chain of annealing in an oxygen atmosphere has been found to oxygen atoms is believed to be the key to superconduc- 5 improve the superconducting properties of the Y-Ba ting behavior. Yet the above description is an idealized Cu-O compound. The produced powder is then pro one and the actual distinct structural conformation has cessed by conventional means to form a bar (by com not yet been delineated. Note that there appear to be paction) which is then used as the superconducting extra oxygen atoms in the superconducting unit cell, medium. compared to that of the semiconductor. O I have found that my new invention employing high To date, most of the high-T superconducting ce critical temperature superconducting ceramics to form ramic compositions announced to date are based on the superconducting coils of the instant invention elimi cuprate compounds having Cu-O2 layers as part of the nates many of the problems associated with the design structure. Some of these have included: of electromagnetic and coil guns of the prior art. Bismuth Strontium Calcium Copper Oxide: 15 The DC powered hybrid coil gun consists of a stan dard barrel, a magnet winding wrapped around the Biz Sr3-x Cax Cu2O 8-y barrel, a large mass piston and a projectile. A conven T = 114 K. tional gun can be modified to operate as a direct-current powered hybrid-coil gun to accelerate projectiles to Thallium Calcium (Barium) Copper Oxide: 2O high velocities and frequencies which cannot otherwise be achieved. The gun arrangement of the instant inven Tl Ba2 Ca Cu2O7 tion facilitates collision between the large mass piston Tl Ba2 Ca2 Cu3 Og and a small mass projectile, thereby resulting in velocity T Ba2 Ca3 Cu4 Ol 25 amplification. Said collision is accomplished through Tl Ba2 Ca Cu5 O13 the magnetic field interaction between the piston and an T = 120 K. external field, between the projectile and the external winding, and between the piston and the projectile. The Lead Strontium Lanthanide Copper Oxide use of high critical temperature superconducting coils 30 eliminates the need for using liquid helium. The external field is charged prior to firing of the gun, using a DC power supply. The external field decay during firing has been found to be negligible and multiple shots can be In the last compound given, the CuO2 - sheets are fired, facilitated by the presence of the superconductive present but there is also a PbO-Cu-OPb sandwich as 5 external field winding. well, not observed in ceramic superconductors prior The main components of the direct-current powered thereto. The copper ions in this sandwich are monova hybrid-coil gun are: the gun barrel, the external magnet lent and each is coordinated, above and below, to two windings, the piston, and the projectile. oxygen atoms in the PbO layers. The copper atoms in The barrel has a standard conventional winding the CuO2 sheets have an average valence of about 2.25, which is tapered in the combustion region. It is only which is consistent with previously discovered cuprate subject to gaseous pressure and not to magnetic forces. compounds, given above. However, the presence of The barrel wall can thus be made thin if the gaseous Cut atoms lowers the average valence of copper ions in pressure is reduced. the new structure to below 2.0, which is atypical. In The magnet design consists of a selected supercon deed, preparation conditions needed to prepare these 45 ducting winding which produces an axially tapered compounds includes a mildly reducing atmosphere so as field. It can be made from conducting materials such as not to oxidize Pb2+ to Pb. metals, coated with a selected superconductor. Low There have also been some compositions announced, current and low voltage is acceptable to charge the based on a copper-free composition, vis: magnet if charging is done over a sufficiently long time. 50 The piston has a conductive winding which is ther BaO. KO - BiO3 mally insulated from the high temperature combustion This compound is said to become superconducting at products. This can be achieved by embedding a metallic about 30 K. While copper-oxide superconductors ex winding in a ceramic matrix. The piston also has a con hibit layered structures that carry current efficiently 55 ductive windings and requires no insulation since it is only along certain planes, this new material is a three-di not in contact with the combustion products. mensional network of bismuth and oxygen with proper Propellants or explosives are used to power the gun ties that are much less sensitive to crystallographic and the following sequence of events takes place during direction. It is hoped that compositions will be discov operation: ered in this system with temperature properties that (a) The piston is accelerated by the high pressure gas rival those of copper-bearing compounds. generated in the barrel. The main advantage to superconducting composi (b) The piston, reaching a certain velocity, ap tions with higher T values is that they can operate at proaches the external solenoid region. The piston is thus liquid nitrogen temperatures (78 K), thus avoiding the subjected to a positive field gradient and is thus subject need to use liquid helium. Superconducting ceramic 65 to a decelerating magnetic force. compositions are normally prepared by weighing out (c) Current is induced in the piston windings as it specific quantities of selected oxides. The combination moves in the external magnetic field. Initially, the cur is thoroughly mixed by conventional means and then rent in the piston will be in the opposite direction to the 4,966,884 5 6 current in the external windings. The external magnet the barrel a generally tapered field strength characteris current also increases. tic of the type shown in FIG. 3A in which the field (d) The increase in the solenoid current induces cur strength is plotted as a function of distance along the rent in the projectile windings. The projectile is placed barrel. in a low field gradient region near the center of the A projectile b is received within the barrel down magnet windings, so as to have sufficient time for stream from a propellant mass 4 which can be ignited by charging its coil. an igniter 5. In general, the mass 4 can begun powder (e) The currents induced in the piston and the projec or the like ignited by a spark from the igniter 5, al tile windings are initially in the same direction. The though any other selectively detonatable means for current in the external winding flows in the opposite 10 producing propellant gases can be used. direction. Located specifically downstream of the midpoint of (f) The projectile is initially placed in a negative field the field strength characteristic is a projectile c which gradient producing accelerating magnetic forces. can be magnetically propelled as will be described in The operation described above is equivalent to the greater detail hereinafter. The coils 1-3 can be ener collision of two objects and is defined here as magnetic 15 gized by a direct-current source 6 which charges these collision. This will result in velocity multiplication and coils. The coils are composed of wire, film, bands or the projectilevelocities in excess of 4 km/s. Such system is like of one of the high-temperature superconductive also suitable for space launching. materials previously described. The application of high critical temperature super The portion receiving the coil means 1, 2, 3 can be conductors makes the use of the direct-current powered 20 enclosed in a chamber 7 which can be supplied with hybrid-coil gun of my new invention practical since no nitrogen or some other coolant, e.g. from a tank 8, the liquid helium will be required. It is preferred, but not latter representing cooling means for bringing the coil necessary, to use a superconducting winding for the temperature to superconductivity temperature, i.e. a piston, and/or the projectile, since they carry current temperature below the critical temperature T of the for a short time. 25 superconductor. The cooling means 7, of course, also In the operation of my new invention, current in the serves to cool the piston b and the projectile c to the piston windings decreases as the piston moves away critical temperature T of their respective superconduc from the positive field gradient region into the negative tor windings described in connection with FIGS. 2A field gradient region. The piston is first accelerated and and 2B. is then decelerated as the current reverses. A switch is 30 The projectile can be, for example, a satellite to be opened when the velocity reaches zero so that said launched by the motion into space or any other projec piston can be retrieved and repetitively used. tile. Simultaneous multiple firing is also possible . The In operation, with the coil means 1, 2, 3 charged to external solenoid winding decelerating the piston is create a magnetic field as shown in FIG. 3A, the firing used to charge a number of solenoids. These solenoids 35 of the propellant mass will generate propellant gases to are used to simultaneously accelerate the multiple pro drive the piston b to the right. The tapering magnetic jectiles. field encountered by the coil of the winding of the piston induces a current flow therein and the resulting BRIEF DESCRIPTION OF THE DRAWING magnetic field induces a current pulse in the coil means The above and other objects, features and advantages which is superimposed upon the direct-current field of the present invention will become more readily ap thereof and induces a magnetic pulse which drives the parent from the following description, reference being projectile c to the right with amplified velocity and made to the accompanying drawing in which: without, of course, any direct contact between the pis FIG. 1 is a cross-sectional view through a hybrid coil ton and the projectile. gun utilizing superconducting elements; 45 Switch means represented diagrammatically at 9 can FIG. 2A is a cross-sectional view of a piston for use be actuated to deenergize the coils 1-3 or to quench the in the apparatus of FIG. 1; superconductor, or field reversal may be generated to FIG. 2B is a cross-sectional view of a projectile draw the piston b back into its original position for the adapted to be ejected from a smaller diameter portion of firing of another projectile and a fresh mass of propel the barrel receiving the piston of FIG. 2A; 50 lant material can be introduced through a breach in the FIG. 3A is a diagram of the magnetic field distribu barrel (now shown) or by any other means. tion in which magnetic field strength is applied along As can be seen from FIG. 2A, the piston b can com the ordinate versus displacement along the abscissa for prise a body (e.g. of ceramic) 10 formed with a closed the region surrounded by the solenoid coils; loop winding 11 composed of one of the high-tempera FIG. 3B is a diagram showing the coil arrangement 55 ture superconductors previously described whereas the associated with the diagram of FIG. 3A; projectile c of FIG. 2B is likewise composed of a body FIG. 4 is a diagrammatic cross-sectional view illus 12 (e.g. of ceramic) and a closed-loop superconductor trating a reduced recoil hybrid coil gun according to winding 13. the invention; and As can be seen from FIG. 4, the coil means need not FIG. 5 is another diagrammatic cross section show comprise the coil assembly shown in FIG. 1 in which ing a multiple projectile coil gun. tapered fields tapered in opposite directions lie on oppo site sides of a median plane, but can comprise spaced SPECIFIC DESCRIPTION apart coils. For example, here the barrel means is FIG. 1 shows a hybrid coil gun according to the formed by two barrels 20 and 21, respectively receiving invention in which the barrel a of a nonmagnetic mate 65 the piston b and the projectile c. rial which can be a ceramic or a metal having low mag The barrel 20 is surrounded by the coil 22 composed netic susceptibility is surrounded by three coils d re of a superconductor and series connected with a coil 23 spectively represented at 1, 2 and 3 to generate, along surrounding the barrel 21 so that the current pulse gen 4,966,884 7 8 erated by propellant of the piston is transmitted by 7. The hybrid coil gun defined in claim 6 wherein conductors 24 to the coil 23 to propel the projectile. both of said closed-loop windings are composed of a The means for charging the coils 22 and 23, namely, a superconductor. direct-current source, and for cooling the gun to a tem 8. The hybrid coil gun defined in claim 6 wherein said perature below the critical temperature T of the super superconductor of said one of said closed-loop windings conductors may be the same as has been illustrated in is a low critical temperature superconductor, further FIG.1. The downstream portion of the barrel faces in a comprising means for cooling said means defining said direction opposite a direction in which the upstream at least one barrel. portion faces and the upstream and downstream por 9. The hybrid coilgun defined in claim 6 wherein said tions can be mechanically connected together to mini 10 superconductor of said one of said closed-loop windings mize recoil. is a high critical temperature superconductor, further The principle of FIG. 4 is also applicable to the firing comprising means for cooling said means defining said of a plurality of projectiles. Here the barrel means com at least one barrel. prises a piston barrel 30 and projectile barrels 31, 32. 10. The hybrid coil gun defined in claim 1 wherein The piston b, driven by a propellant as previously de 15 said closed-loop winding of said piston is thermally scribed but not illustrated in this Figure, cooperates insulated from said means for applying a propellant to with the magnetic field of coil 33 to generate the cur said piston. rent pulse which is applied by the conductors 34 and 35 11. The hybrid coil gun defined in claim 11 wherein to the coils 36 and 37, respectively, surrounding the said means for applying a propellant to said piston in barrel portions 31 and 32 to magnetically propel the 20 cludes a combustion chamber in said means defining said at least one barrel and means for initiating detona projectile c within these barrels to the right. The closed tion of an explosive composition received in said cham loop portion of the coil means is here connected electri ber. cally in parallel to a plurality of further windings on 12. A hybrid coil gun, comprising: respective downstream portions of the means defining 25 a projectile formed with at least one closed-loop the barrel for propelling respective projectiles there electromagnet winding; from. a piston formed with at least one closed-loop electro I claim: magnet winding; 1. A hybrid coil gun, comprising: means defining at least one barrel receiving said pro a projectile formed with at least one closed-loop 30 jectile and from which said projectile can be elec electromagnet winding; tromagnetically propelled; a piston formed with at least one closed-loop electro coil means on the barrel having at least a portion magnet winding; magnetically coupling to said closed-loop winding means defining at least one barrel receiving said pro of said projectile for magnetically propelling said jectile and from which said projectile can be elec 35 projectile from said barrel, said coil means com tromagnetically propelled; prising a closed-loop portion generating an exter coil means on the barrel having at least a portion nal field and magnetically coupling to said closed magnetically coupling to said closed-loop winding loop winding of said piston to decelerate said pis of said projectile for magnetically propelling said ton and generate by induction a current pulse for projectile from said barrel, said coil means com magnetically propelling said projectile; and prising a closed-loop portion generating an exter means for applying a chemical propellant to said nal field and magnetically coupling to said closed piston to drive said piston through said closed-loop loop winding of said piston to decelerate said pis portion of said coil means and said external field, ton and generate by induction a current pulse for whereby said current pulse is induced, said closed magnetically propelling said projectile; and 45 loop portion of said coil means being located along means for applying a chemical propellant to said an upstream portion of said barrel and being con piston to drive said piston through said closed-loop nected to a further winding on a downstream por portion of said coil means and said external field, tion of said barrel for propelling said projectile. whereby said current pulse is induced, the closed 13. The hybrid coil gun defined in claim 12 wherein loop portion generating an external field of axially 50 said downstream portion of said barrel faces in a direc tapering field strength. tion opposite a direction in which said upstream portion 2. The hybrid coil gun defined in claim 1, further faces and said upstream and downstream portions are comprising a direct-current source connectable across mechanically connected together to minimize recoil. said closed-loop portion of said coil means for charging 14. The hybrid coil gun defined in claim 13 wherein said external field. 55 said closed-loop portion of said coil means is connected 3. The hybrid coil gun defined in claim 2 wherein at electrically in parallel to a plurality of further windings least said closed-loop portion of said coil means is com on respective downstream portions of said means defin posed of a superconductor. ing said barrel for propelling respective projectiles 4. The hybrid coilgun defined in claim3 wherein said therefrom. superconductor is a high critical temperature supercon 15. A method of operating a hybrid coil gun which ductor. comprises the steps of: 5. The hybrid coilgun defined in claim3 wherein said (a) firing a combustible composition to produce a superconductor is a low critical temperature supercon gaseous propellant; ductor, further comprising means for cooling said coil (b) driving a piston formed with at least one closed 3S 65 loop electromagnet winding through a means de 6. The hybrid coil gun defined in claim 3 wherein at fining at least one barrel receiving a projectile and least one of said closed-loop windings is composed of a from which said projectile can be electromagneti superconductor. cally propelled and through a coil means on said 4,966,884 10 barrel having at least a portion magnetically cou superconductor having a critical temperature Tc) 23 pling to a closed-loop winding of said projectile for K. and cooling at least said coil means below said criti magnetically propelling said projectile from said cal temperature. barrel, said coil means comprising a closed-loop 17. The method defined in claim 15 wherein said portion generating an external field and magneti current pulse is applied to a plurality of windings, each cally coupling to said closed-loop winding of said propelling a respective projectile. piston to decelerate said piston and generate by 18. The method defined in claim 16, further compris induction a current pulse for magnetically propel ing the steps of forming at least one of said closed-loop ling said projectile; and windings as a superconductor and cooling it below the (c) maintaining said field charged. 10 critical temperature of the superconductor forming said 16. The method defined in claim 15 wherein said field one of said closed-loop windings. is maintained charged by forming said coil means of a ak k k :

15

20

25

30

35

45

50

55

65