JP2571863B2 - Railgun type electromagnetic accelerator with distributed electrodes - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electromagnetic accelerator.

[Conventional technology]

Railgun-type electromagnetic accelerators (hereinafter referred to as railguns) that accelerate a macroscopic object at high speed using electromagnetic force are 10 kg / s per second, which is difficult to achieve using a method that uses the explosive force of combustion gas of explosives or high-pressure gas. It is possible to obtain the above flying object speed, and it has been paid attention in recent years.

Two types of materials are used for railgun armatures: solid metal and plasma. Particularly, the method using plasma armatures is used to accelerate a small flying object weighing several grams at ultra-high speed. Mainly used, for example, as an accelerator for generating an impact ultra-high pressure of 10 million atmospheres or more due to collisions between materials, as a simulation device for meteorite collision problems in outer space, and as a solid hydrogen to the fusion reactor It is expected to be used for fuel pellet driving devices and the like, and development for practical use is being actively conducted.

Regarding the research and development of railguns and their utilization technology,
EE Transactions on Magnetics, vol.Mag-20 (198
9), ibid, vol.Mag-19 (1987), and ibid, vol.Mag-1
6 (1985).

FIGS. 7 (a), (b) and (c) show the acceleration principle and structure of a conventional rail gun using a plasma armature.
FIG. 7 (a) shows a general sectional shape of a conventional rail gun. An acceleration hole 2 for accelerating the flying object and the plasma electron is formed in a space between the two rail-shaped electrodes 1 and the insulator support body 2, and the inner surface of the rail electrode is directly exposed in the acceleration hole 2. To form a cross section of the accelerating hole. As shown in FIG. 7 (b), a flying object 3 of an insulator is installed in the acceleration hole, and a metal plate or a metal foil 4 for forming a plasma electron is installed behind the flying object 3, and a space between the two rail electrodes is provided. Make electrical contact. In this state, power supply 5 such as a capacitor bank is
When the power supply voltage is applied by connecting the switch 6 to the rail and closing the switch 6, the metal plate or the metal foil is turned into plasma by a large current as shown in FIG. 7 (c). The plasma 7 receives an electromagnetic force according to the law of electrode induction while applying a force to the flying object and accelerates while maintaining the current between the rails. The plasma moves together with the flying object and always serves as an armature located behind the flying object, and continues to accelerate the flying object with a force proportional to the square of the current.

In this way, in the railgun, the flying object should be accelerated as long as current is supplied to the formed plasma element, but actually, when the flying object speed becomes 5 km / s or more,
It is known that the electromagnetic force acting on the flying object is significantly reduced from the value expected from the current value, and the acceleration efficiency is rapidly reduced. Therefore, as a result of detailed observation of the behavior of the plasma electron inside the acceleration hole, the following three types of phenomena are considered to be factors that reduce the acceleration force by the electromagnetic force.

(1) Since the plasma element has a length corresponding to the spatial distribution of the current, when the plasma element moves at high speed in the accelerating hole, turbulence flows in the gas due to the viscosity of the plasma gas. As a result, a resistive force proportional to the length of the plasma armature and proportional to the square of the velocity acts on the entire plasma armature. The viscous drag forces further increase the length of the plasma armature, and the total drag increases rapidly.

(2) With the passage of the plasma electron, the material of the inner surface of the acceleration hole is taken into the plasma by evaporation, ablation, etc., and the age of the plasma electron increases, resulting in the movement speed and weight of the electron. A deceleration force proportional to both the rate of increase acts on the armature.

(3) The moving speed is slow behind the plasma element due to an increase in the length of the plasma element, that is, diffusion of the current distribution and restriking caused by dielectric breakdown between the rail electrodes after the element has passed. The following current distribution occurs. As a result, the plasma electron current rapidly shifts to the secondary current distribution, and the electromagnetic force acting on the flying object is rapidly attenuated.

Measures currently being taken to solve the above problems include: (A) the initial speed of the electron-accelerated flying object by hydrogen gas compressed to high pressure, and the moving speed of the plasma armature at the beginning of electromagnetic acceleration As much as possible to reduce evaporation and ablation of the inner surface of the acceleration hole shown in (2) above,
By converting the hydrogen gas into plasma to form a low-viscosity plasma armature, the viscous resistance shown in the above (1) is reduced, and the high-pressure hydrogen gas existing behind the plasma armature is changed to a rail electrode behind the armature. Increase the withstand voltage between
Method for preventing the occurrence of secondary current distribution due to restriking shown in (3) above (eg, RSHAWKE, et al., IEEE, Transactions o
n Magnetics, vol.25, No.1, p219 (1989)), (B) One of the rail electrode surfaces in the acceleration hole is covered with an insulating film, and a number of thin metal plates with a length of about 100 mm are covered inside. Each metal sheet and the rail electrode are connected via a fuse in a state where they are insulated from each other, and the fuse connected to the metal sheet while the plasma armature passes through the area of one sheet metal. When activated, when the plasma armature reaches the area of the next metal sheet, all the metal sheets in the previous area are insulated from the rail electrode to prevent re-ignition ( Example:
JVParker, IEEE, Transactions on Magnetics, vol.25,
No. 1, p412 (1989)).

The method (A) is currently undergoing experiments, and its results are expected as effective countermeasures for all the problems (1), (2), and (3). However, this method requires a high-performance two-stage gas gun for compressing dangerous hydrogen gas to high pressure and initially accelerating several grams of a flying object to 5 km / s or more. There is a drawback that a method for reliably converting the flowing high-pressure hydrogen gas into plasma at a specific place has not been established. Regarding the method (B), from the results of the acceleration experiment using only the plasma armature,
Its principle effectiveness has been confirmed. However, when using this method to accelerate a projectile, the acceleration holes for smoothly accelerating the projectile while maintaining a strong electromagnetic force, and the structure around it become very complicated electrically and mechanically. This method is not practical for the development of a practical projectile accelerator.

In addition to the problems related to the properties of the plasma armature as described in (1), (2), and (3) above, the rail gun has the following problems due to its structure.

(4) Since a large current of arc plasma is generated in the accelerating hole, slight damage to the inner surface of the accelerating hole, especially the surface of the rail electrode, is unavoidable. Although the method of expanding the diameter of the acceleration hole by cutting has become common, it is actually difficult to precisely expand the diameter of the inner surface of the acceleration hole made of metal and insulator over the entire acceleration length, and it is enormous. It takes effort.

(5) When the inside of the acceleration hole is evacuated to avoid air resistance, the basic structure of the conventional rail gun is shown in FIG. 7 (a).
Because of the structure in which the rail electrode and the insulator support are bundled as shown in (1), a general sealing method using an O-ring or the like cannot be adopted. For this reason, a method is adopted in which the entire basic structure of the rail gun, including the rail electrodes, is housed in a vacuum vessel. This method not only makes it difficult to diagnose and maintain the acceleration condition of the rail gun, but also makes it difficult to maintain electrical insulation. Disadvantageous and undesirable in terms of security. Furthermore, the seventh
The structure of the rail gun as shown in FIG. 1A makes it difficult to mechanically and electrically design the connection part even when the rail gun is connected to another acceleration tube.

[Problems to be solved by the invention]

The present invention provides a method for positively controlling the current distribution of the plasma armature from outside the acceleration hole, and also repairs the inner surface of the acceleration hole and solves the problem inside the acceleration hole, in order to solve the above-mentioned problems relating to the plasma armature of the conventional railgun. The present invention provides a new rail gun structure to solve the conventional difficulties related to evacuation and connection with other accelerator tubes.

[Means for solving the problem]

In order to solve the above-mentioned problems, the inventors have conducted intensive studies, and as a result, have accomplished the present invention.

That is, in the configuration of the present invention, the railgun type electromagnetic accelerator has a circular or square acceleration hole for accelerating the insulator flying object and the plasma element without exposing the two rails directly in the acceleration hole. In addition, a large number of through holes drilled from both sides toward the center of the acceleration hole so that they are sensible along the acceleration hole and are symmetrical to the center of the acceleration hole, perpendicular to the center line of the acceleration hole. The insulator accelerating tube is installed so as to be sandwiched between two rail electrodes, and the other end of each of the through holes is electrically connected to the rail electrode directly or via a switching element such as a fuse. Inserting the branch electrodes exposed on the inner surface of the acceleration hole, forming a large number of dispersed electrode surfaces arranged in a sense such as facing each other on the inner surface of the accelerator hole, connecting the rail electrode to a power source, and forming the dispersed electrode facing the inner surface of the acceleration hole. A By generating arc discharge and accelerating the arc plasma as a plasma electron in the accelerating hole, the spatial distribution of the current of the plasma electron for accelerating the flying object is controlled by the switching element or the like, and furthermore, after the discharge. An electromagnetic accelerator characterized by facilitating repair of damage to the inner surface of the acceleration hole and facilitating the design of a gas sealing structure for reducing the pressure in the acceleration hole and a joint structure with another acceleration tube. That is, in the present invention, a large number of branch electrodes connected to the rail electrode directly or via a switching element such as a fuse in a comb-like manner, and the insulation provided in the accelerating hole of the dispersion electrode formed by the end face of each branch electrode. The problem was solved by adopting a body acceleration tube.

[Action]

More specifically, FIG. 1A is a conceptual diagram of the present invention. A large number of branch electrodes 8 are connected to the rail electrode 1 at regular intervals directly or via switching elements 9 such as fuses. The end face of each branch electrode is connected to the accelerating hole 2 of the insulator accelerating tube 10 installed between the two rail electrodes.
To form dispersed electrode surfaces which are exposed to each other and face each other at equal intervals. When this rail electrode is connected to a power source and an arc discharge is generated between the opposing electrodes in the accelerating tube by any method, the arc current acts as a plasma armature 7 which moves by receiving an electromagnetic force, and the insulator flying object 3 To accelerate. In this case, as shown in FIG. 1 (b), the fuse 9 operates one after another as the armature passes to insulate the branch electrode from the rail electrode, so that the current distribution of the armature is always limited behind the flying object. Is trapped in the area that has been set. According to this method,
Not only can the occurrence of the secondary current distribution described above be prevented, but also the operating speed of the fuse can be adjusted to finely control the length of the current distribution, and the viscosity and mass of the plasma gas can be controlled. The length of the plasma armature can be optimized so that the attenuation of the acceleration force due to the increase is minimized. Further, as shown in FIG. 2, since the insulator accelerating tube 10 between the rail electrodes can be formed of an integral insulator, other accelerating tubes can be formed.
The mechanical / electrical design of the connection part with the O-ring 12 becomes easy, and the evacuation of the inside of the accelerating hole is performed by using an O-ring 12 as a gas sealing method at the connection part with each branch electrode and other accelerating tubes.
And other standard methods can be adopted. Further, as shown in FIG. 3, since each branch electrode can be formed into a screw structure, when the end face of each branch electrode is damaged by a large current, the branch electrode is rotated to slightly project the end face into the inside of the acceleration hole. By cutting only the protruding part from inside the acceleration hole with a reamer, etc.,
The electrode surface can be easily repaired.

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to examples.

As shown in Fig. 4, an acceleration experiment using only a plasma electron was performed under atmospheric pressure using a distributed electrode type rail gun with a total length of 400 mm and an acceleration length of 255 mm and a 1500 μF capacitor bank charged to 6 kV. The behavior of the plasma armature and the effect of the fuse were examined, and compared with the conventional railgun. 5 (a) and 5 (b) are a partially enlarged view and a sectional view of the distributed electrode type rail gun shown in FIG. The rail electrodes 1 were made of copper having a cross section of 20 mm × 20 mm, and 13 branch electrodes 8 each made of a copper bar having a diameter of 4 mm were attached to each rail electrode at intervals of 20 mm. These branch electrodes are 5m thick
Exposed to the inner surface of the FRP accelerating hole with a cross section of 20 mm x 14 mm through the FRP layer of m, the dispersed electrode was not directly bonded, but was insulated with a polycarbonate tube 13, and then passed through a 0.8 mm diameter copper thin wire fuse 9. Connected. In addition to the distributed electrode type railgun with a fuse, a distributed electrode type railgun without a fuse in which the rail electrode and the branch electrode were directly connected without using a fuse, and a conventional railgun having no branch electrode were also used. The arc discharge was generated by guiding the initial discharge current of the capacitor to the line explosion circuit 14 on the side of the acceleration hole, and blowing the plasma generated by the line explosion from the pore on the side of the acceleration hole. Observation of the current distribution of the plasma armature
Using the search coils 15 arranged at six places along the acceleration hole, the time change of the magnetic field at each point due to the armature current was obtained, and the state of the current distribution was qualitatively evaluated.

As a result, the results shown in FIGS. 6 (a), (b) and (c) were obtained. FIG. 6 (a) shows the experimental results of the conventional railgun, showing the total current waveform 22 on an arbitrary scale together with the magnetic field changes 16 to 21 at each point. From the magnetic field waveform at each point,
Under the conditions of this experiment, it was found that no secondary current distribution was generated, and a plasma electron having a polarized current distribution was formed and moved at about 2.6 km / s.

FIG. 6 (b) shows the results of the distributed electrode type railgun without a fuse. It can be seen that the discharge between the dispersed electrodes propagates at about 2.5 km / s from the fine bending of the magnetic field waveform, but the current distribution is shown in FIG. It can be seen that the light diffuses widely and symmetrically with respect to FIG.

FIG. 6 (c) shows the result of a distributed electrode type railgun with a fuse, in which up to eleventh of the thirteen fuses were activated. It was found that the current distribution was poled to the same degree as that of the conventional railgun due to the function of the fuse, and the movement speed was increased, albeit slightly. This result shows that, according to the present invention using a distributed electrode structure with a fuse, a plasma armature having a current distribution equivalent to that of a conventional railgun is obtained.
It shows that it can be formed under active external control.

〔The invention's effect〕

As described above, a large number of branch electrodes connected to the rail electrode directly or via a switching element such as a fuse in a comb-like manner, and an insulating material having a dispersion electrode formed by the end face of each branch electrode in its acceleration hole. The present invention, which employs a body acceleration tube, not only enables external control of the plasma electron current distribution, which greatly affects the efficiency of electromagnetic acceleration, but also facilitates repair of damage to the inner surface of the accelerating hole after discharge. In addition, it is possible to easily design a gas sealing structure for evacuating the inside of the acceleration hole and a joint portion with another acceleration tube.

[Brief description of the drawings]

FIGS. 1 (a), (b) and FIGS. 2, 3 are schematic diagrams for explaining the present invention, and FIGS. 4, 5 (a), (b) are experiments of the embodiment. FIGS. 6 (a), (b) and (c) are explanatory diagrams of the results of the embodiment, and FIGS.
(A), (b), (c) is a schematic diagram showing the acceleration principle and general structure of a conventional rail gun. 1: rail electrode, 2: acceleration hole, 3: flying object, 4: plasma forming material, 5: power supply, 6: switch, 7: plasma armature, 8: branch electrode, 9: fuse, 10: insulator accelerating tube , 11: other accelerator tube, 1
2: O-ring, 13: polycarbonate tube, 14: wire explosion circuit, 15: search coil, 16-21: magnetic field waveform at each search coil position, 22: total current waveform.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuzo Fujiwara 1-1, Higashi, Tsukuba City, Ibaraki Prefecture Inside the Institute of Chemical Technology, Institute of Industrial Technology (72) Inventor Katsutoshi Aoki 1-1-1, Higashi, Tsukuba City, Ibaraki Prefecture, Japan Inside the Technical Research Institute (72) Inventor Masanori Yoshida 1-1-1 Higashi, Tsukuba, Ibaraki Pref.Industry and Technology Research Institute Chemical Research Laboratory (72) Inventor Yozo Kakudate 1-1-1 Higashi, Tsukuba, Ibaraki Pref. 72) Inventor, Hyoha Prefecture 1-1, Higashi, Tsukuba, Ibaraki Pref., Industrial Technology Institute, Research Institute of Chemical Technology (72) Inventor, Masahiro Miyamoto 2-2-1 Nagasaka, Yokosuka City, Kanagawa Prefecture, Fuji Electric Research Institute, Ltd. (72) Inventor: Kimi Morita 2-2-1 Nagasaka, Yokosuka City, Kanagawa Prefecture Inside Fuji Electric Research Laboratory Co., Ltd. (72) Norihiro Hiroshige 1-1, Tanabeshinda, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Akira Kubota 1-2-1, Yurakucho, Chiyoda-ku, Tokyo Asahi Kasei Kogyo Co., Ltd. (72) Inventor Tada Actual Examiner, Nichicon Co., Ltd., Nichicon Co., Ltd. Examiner Yasumitsu Tsuchiya, 3rd floor, Uehara Bldg.

Claims (1)

(57) [Claims] 1. A railgun type electromagnetic accelerator having a circular or rectangular accelerating hole for accelerating an insulator flying object and a plasma element without exposing two rails directly in the accelerating hole. An insulator having a large number of through-holes drilled from both sides toward the center of the acceleration hole so as to be symmetrical with respect to the center of the acceleration hole at equal intervals along the acceleration hole and perpendicular to the center line of the acceleration hole An acceleration tube is installed so as to be sandwiched between two rail electrodes, and one end of each of the through holes is electrically connected to the rail electrode directly or via a switching element such as a fuse, and the other end is connected to the inner surface of the acceleration hole. Insert the exposed branch electrodes, form a large number of dispersed electrode surfaces facing each other at equal intervals on the inner surface of the acceleration hole, connect the rail electrode to the power supply, and arc discharge between the dispersed electrodes facing the inner surface of the acceleration hole. Occurs Then, the arc plasma is accelerated as a plasma electron in the acceleration hole by the interaction between the magnetic field in the acceleration hole and the arc discharge current, so that the current distribution of the plasma electron that accelerates the flying object is changed by the switching element or the like. Dispersion characterized by facilitating control and repairing damage to the inner surface of the accelerating hole after discharge, and facilitating the design of a gas-sealed structure and a joint structure with other accelerating tubes for reducing the pressure in the accelerating hole. Railgun type electromagnetic accelerator with electrodes.