Pulse plasma thruster

Abstract

To provide a pulse plasma thruster which can suppress a thrust generation in a direction other than a thrust direction and which can achieve a stable impulse bit for a long time.SOLUTION: A pulse plasma thruster includes an anode, a propellant, and a cathode, in which the anode, the propellant, and the cathode are aligned in a first direction. The anode and the cathode are fixed at relative positions, and the propellant can relatively move along the first direction with respect to the anode, and has an anode storage part formed on one side in the first direction and a cavity formed on the other side. The anode is arranged in the anode storage part. The cavity has an opening on the other side, and is formed in a shape of expanding from one side toward the other side. The cavity communicates with the anode storage part to be adjacent to the anode. The cathode has a through hole formed therein, and at least a part of the through hole is arranged to communicate with the cavity. The propellant is urged toward the other side.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pulsed plasma thruster.

Background Art

[0002] A pulsed plasma thruster (PPT) is a type of electric propulsion. In recent years, the number of small satellites launched has been increasing, and miniaturization and power saving of artificial satellites are desired. Since a solid propellant is used in a PPT, valves, tanks, etc. are not required, and the structure can be simplified, so it has high reliability and is lightweight. Due to the above characteristics, solid propellants are expected to be used as thrusters for small artificial satellites.

[0003] For example, Patent Document 1 discloses an electromagnetic acceleration type parallel plate PPT. This electromagnetic acceleration type parallel plate PPT obtains thrust by the Lorentz force generated by the current and magnetic field generated during discharge. Also, Non-Patent Document 1 discloses a electrothermal acceleration type coaxial PPT. This electrothermal acceleration type coaxial PPT obtains thrust by the pressure increase when plasma expands aerodynamically heated in a cavity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in an electromagnetic acceleration type parallel plate PPT, due to the structure in which the electrode side surface is open, there is a risk that the plume leaks from the electrode side surface, generating thrust in a direction other than the propulsion direction. In addition, in the case of a thermoelectric acceleration type coaxial PPT, as the operation continues, the volume of the cavity increases due to sublimation and the discharge density decreases, resulting in a problem that the stability of the impulse bit decreases.

[0006] The present invention has been made in view of such problems. The present invention provides a PPT that can suppress the generation of thrust in a direction other than the propulsion direction and can achieve a long-term stable impulse bit.

Means for Solving the Problems

[0007] The pulse plasma thruster according to an exemplary aspect of the present invention includes the following configuration. [1] A pulse plasma thruster including an anode, a propellant, and a cathode, wherein the anode, the propellant, and the cathode are arranged along a first direction, and the anode and the cathode have their relative positions fixed to each other. The propellant is relatively movable along the first direction with respect to the anode, and an anode accommodation portion is formed on one side in the first direction, and a cavity is formed on the other side. The anode is disposed in the anode accommodation portion, the cavity has an opening on the other side, is formed in a shape that expands from the one side toward the other side, and is configured to communicate with the anode accommodation portion so as to be adjacent to the anode. The cathode has a through hole formed therein, and at least a part of the through hole is disposed so as to communicate with the cavity, and the propellant is biased toward the other side. [2] The pulse plasma thruster according to [1], wherein the anode is rod-shaped, and the anode accommodation portion is a hole that penetrates in the first direction from the end portion on the one side of the propellant to the cavity. The pulse plasma thruster according to [3][1] or [2], further comprising a biasing member configured to bias the propellant toward the other side. The pulse plasma thruster according to any one of [4][1] to [3], wherein the taper angle of the cavity with respect to the first direction is 30°. The pulse plasma thruster according to any one of [5][1] to [4], wherein at the boundary between the cavity and the through hole, the inner diameter of the through hole is smaller than the inner diameter of the cavity. The pulse plasma thruster according to any one of [6][1] to [5], wherein the through hole is formed in a shape that expands from the one side toward the other side. The pulse plasma thruster according to any one of [7][1] to [6], wherein the material of the anode is tungsten. The pulse plasma thruster according to any one of [8][1] to [7], wherein the amount of wear of the other side of the anode due to wear of the anode is smaller than the amount of displacement of the one side of the propellant due to sublimation of the propellant. [Advantages of the Invention]

[0008] According to the PPT of the present invention, it is possible to suppress the generation of thrust in directions other than the propulsion direction, and to provide a PPT capable of achieving a long-term stable impulse bit. [Brief Description of the Drawings]

[0009]

Figure 1

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Figure 8

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Various characteristic matters shown in the following embodiments can be combined with each other. Also, an invention can be established independently for each characteristic.

[0011] 1. First Embodiment 1.1 Overall Configuration of PPT1 Hereinafter, PPT1 of this embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic cross-sectional view of PPT1 according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the propellant 30 of PPT1 according to the first embodiment of the present invention. And FIG. 3 is a schematic cross-sectional view of the cathode 50 of PPT1 according to the first embodiment of the present invention.

[0012] PPT1 according to an embodiment of the present invention includes a fixing member 10, an anode 20, a propellant 30, a biasing member 40, a cathode 50, an igniter 60, a power source (not shown), and a capacitor 70. Here, in the following description, as shown in FIG. 1, the longitudinal direction of the anode 20 and the propellant 30 is defined as the front-rear direction (axial direction) as the first direction, and the direction perpendicular thereto is defined as the up-down direction. PPT1 has a configuration in which the anode 20, the propellant 30, and the cathode 50 are coaxially arranged. Here, being coaxially means that the portions forming the discharge space (the cavity 32 of the anode 20 and the propellant 30 and the through hole 51 of the cathode 50, which will be described in detail below) are coaxially, and includes a slight eccentricity due to machining accuracy.

[0013] 1.1.1 Fixing Member 10 The fixing member 10 fixes the relative positions of the anode 20 and the cathode 50. The fixing member 10 in FIG. 1 includes, as an example, a base portion 11, an anode fixing portion 12, and a cathode fixing portion 13. The anode fixing portion 12 is formed to extend upward on the front side as one side of the base portion 11 and is configured to be able to fix the anode 20. The cathode fixing portion 13 is formed to extend upward on the rear side as the other side of the base portion 11 and is configured to be able to fix the cathode 50. However, the fixing member 10 can adopt any configuration and material as long as it can fix the relative positions of the anode 20 and the cathode 50.

[0014] 1.1.2 Anode 20 The anode 20 is an electrode that causes discharge by functioning together with the cathode 50. The anode 20 is formed in a rod shape that extends in a columnar shape along the front-rear direction. However, if the anode 20 can have a constant size along the front-rear direction, it can have any shape, such as a prism. The front side of the anode 20 is fixed to the anode fixing part 12, and the rear side is disposed so as to be relatively movable in the anode accommodating part 31 of the propellant 30 (details will be described later). The diameter of the anode 20 is 1 mm to 2 mm (millimeter: the same hereinafter), preferably 1 mm. From the viewpoints of strength and resistance, the material of the anode 20 is preferably tungsten, which is less likely to be worn by discharge. However, if it is another material that can suppress wear due to discharge, the material of the anode 20 is not limited to tungsten.

[0015] 1.1.3 Propellant 30 The propellant 30 is a raw material of the exhaust substance for obtaining thrust during the operation of the PPT1. The propellant 30 is formed of a material generally used for solid propellants, such as PTFE (Polytetrafluoroethylene: Teflon (registered trademark)). As shown in FIG. 2, the propellant 30 has an anode accommodating part 31 formed on the front side and a cavity 32 formed on the rear side.

[0016] In FIG. 2, a broken line is attached to the boundary between the anode accommodating part 31 and the cavity 32 for easy understanding, but the anode accommodating part 31 is a hole that penetrates axially from the front end of the propellant 30 to the cavity 32. As described above, the anode 20 is disposed in the anode accommodating part 31 so as to be relatively movable along the axial direction with respect to the propellant 30. Specifically, the arrangement relationship between the anode 20 and the propellant 30 is preferably in a fitting structure with a relative movement such that a large gap is not formed between the propellant 30 and the anode 20, that is, a clearance fit state. Thereby, the movement of the propellant 30 in the direction perpendicular to the axis is restricted with respect to the anode 20 fixed by the fixing member 10, and only the movement in the front-rear direction is allowed.

[0017] The cavity 32 has an opening on the rear side and is formed in a shape that expands from the front side toward the rear side. The cavity 32 can have any shape as long as it expands toward the rear. The cavity 32 can be, for example, in the shape of a frustum of a cone or a bell. At this time, the taper angle α of the cavity 32 is 15° to 85° (degrees: the same hereinafter). Specifically, for example, it can be 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, and can also be within the range between any two of the values exemplified here. Further, the taper angle α is preferably 15° to 50°. Specifically, for example, it can be 15, 20, 25, 30, 35, 40, 45, 50, and can also be within the range between any two of the values exemplified here. The taper angle α is more preferably 30°. By setting the taper angle α within the said range, a stable impulse bit can be obtained. Here, the taper angle α refers to the angle of the straight line connecting the front end portion and the rear end portion of the cavity 32 with respect to the front-rear direction. Further, the cavity 32 is configured to be adjacent to the anode 20 by communicating with the anode housing portion 31.

[0018] Here, as shown in FIG. 1, at the boundary between the cavity 32 and the through-hole 51 of the cathode 50 described later, the diameter of the portion where they communicate is defined as the sublimation surface diameter D of the propellant 30. That is, in the present embodiment, the sublimation surface diameter D is equal to the diameter of the through-hole 51 of the cathode 50. Here, the sublimation surface diameter D is, as an example in the present embodiment, in the numerical range of 2 to 7 mm, and may be appropriately selected according to the depth of the cavity 32, the distance between the anode 20 and the cathode 50, etc. so that a stable impulse bit can be obtained. This is because if the sublimation surface diameter D is smaller than the said numerical range in the present embodiment, the amount of the sublimated propellant will decrease and the impulse bit will decline. Also, if the sublimation surface diameter D is larger than the said numerical range, sublimation will not occur at the outer edge portion of the propellant 30 due to the decrease in the energy density inside the cavity 32, and the original shape of the cavity 32 (i.e., the shape before continuous operation) cannot be maintained when continuously operated.

[0019] 1.1.4 Biasing Member 40 The biasing member 40 is disposed between the fixing member 10 and the propellant 30 and is configured to bias the propellant 30 rearward. The biasing member 40 is, for example, supported at its front side by the anode fixing portion 12 of the fixing member 10 and is configured to push out the propellant 30 at its rear side. Here, as will be described later, the propellant 30 is consumed on the rear side as the discharge is repeated, and the propellant 30 is configured to be pushed out rearward by the biasing member 40. According to such a configuration, the sublimation surface position can be kept constant, so that the anode 20 can stably discharge. The biasing member 40 can be configured by a spring, for example.

[0020] 1.1.5 Cathode 50 The cathode 50 is an electrode that causes discharge by functioning together with the anode 20. As shown in FIG. 3, the cathode 50 is formed with a through hole 51 penetrating in the axial direction and an igniter installation hole 52. Also in FIG. 3, for easy understanding, a broken line is attached to the boundary of the space. In FIG. 1, a part of the propellant 30 is accommodated in the through hole 51 (referred to as the propellant accommodation portion 511) on the front side of the cathode 50. Further, at least a part (referred to as the plasma discharge portion 512) on the rear side of the through hole 51 is arranged to communicate with the cavity 32 of the propellant 30. However, the cathode 50 can adopt any arrangement as long as the plasma generated in the cavity 32 is discharged through at least a part of the through hole 51.

[0021] Further, the through hole 51 has two inner diameters in the propellant accommodation portion 511 and the plasma discharge portion 512, and the inner diameter of the plasma discharge portion 512 is smaller than that of the propellant accommodation portion 511. That is, at the boundary between the cavity 32 and the through hole 51, the inner diameter of the through hole 51 is smaller than the inner diameter of the cavity 32. The step formed by this different inner diameter is defined as the stopper portion 513. According to the present embodiment shown in FIG. 3, by adopting a configuration having the stopper portion 513, the propellant 30 can be accommodated in the propellant accommodation portion 511 and can serve as a stopper for the propellant 30 pushed out by the biasing member 40, which contributes to maintaining the shape of the cavity 32 substantially the same as that before continuous operation. Further, according to such a configuration, for example, due to individual differences in manufacturing or uneven volatilization at the opening of the cavity 32 of the propellant 30 due to the operation of PPT1, even if a gap is formed between the propellant 30 and the cathode 50 for some reason, it is possible to prevent the intrusion of the sublimated gas into the gap.

[0022] The igniter installation hole 52 is formed to communicate with the plasma discharge portion 512 of the through hole 51, and the igniter 60 is installed therein.

[0023] 1.1.6 Igniter 60 The igniter 60 is a member that functions as an ignition discharge for volatilizing the propellant 30. The igniter 60 is installed in the igniter installation hole 52, but can be arranged at any position as long as it can perform the function, and an existing igniter can be used.

[0024] 1.2 Operating Principle The specific propulsion generation principle will be described. The propulsion generation principle of PPT1 forms one shot according to the following operating sequences (1) to (4), and by repeating this, the propulsion function of a spacecraft (for example, an artificial satellite) can be ensured. (1) The capacitor 70 is charged by a power source (not shown). (2) The igniter 60 generates a trigger discharge. As a result, the propellant 30 is vaporized in a very small amount in the cavity 32 and then turned into plasma. (3) The plasma generated by the sublimation of the propellant 30 spreads between the anode 20 and the cathode 50, forming a highly conductive space (discharge space) between the anode 20 and the cathode 50. As a result, the anode 20 and the cathode 50 are short-circuited, and the main discharge occurs as the charges in the discharge space flow to the cathode 50 all at once. Due to the occurrence of the main discharge, the propellant 30 further sublimates and is turned into plasma. (4) The self-induced magnetic field is formed by the main discharge current. Due to the interaction between the current and the magnetic field, a Lorentz force is generated between the anode 20 and the cathode 50. When the generated Lorentz force acts, the sublimated plasma is discharged from the plasma discharge portion 512 of the through-hole 51. Then, as a reaction force of such plasma discharge, the PPT1 obtains thrust. Also, in the cavity 32, since the propellant material turned into plasma by sublimation undergoes Joule heating by the main discharge current flowing through the discharge space, thermal expansion occurs, increasing the pressure in the cavity 32. Therefore, since the plasma is also discharged from the plasma discharge portion 512 of the through-hole 51 due to such thermal expansion, as a reaction force of the plasma discharge, the PPT1 obtains thrust.

[0025] 1.3 Operating effects According to the PPT1 according to the above-described embodiment, the anode 20 is accommodated in the anode accommodation portion 31 adjacent to the cavity 32, and the cavity 32 is configured to communicate at least partially with the through-hole 51 penetrating axially in the cathode 50, so that the generation of thrust in directions other than the propulsion direction can be suppressed. Also, two thrusts, namely the thrust caused by the Lorentz force generated by the interaction between the current and the magnetic field occurring during discharge and the thrust caused by the pressure increase when the plasma expands by heating in the cavity 32, are used, and it is possible to suppress the generation of thrust in directions other than the propulsion direction.

[0026] As described in the above operating principle, in the PPT1 according to the present embodiment, the presence of the cavity 32 enables the thrust by electrothermal acceleration to be obtained. Therefore, in a PPT in which the cavity 32 is not formed in advance, no thrust by electrothermal acceleration can be expected at the start of operation. In a PPT without the cavity 32, the sublimation of the propellant 30 due to continuous operation gradually forms a bell-shaped depression. As the depression is formed, the axial discharge increases, and with the addition of electrothermal acceleration, the impulse bit gradually increases. On the other hand, according to the PPT1 according to the present embodiment, for example, by pre-forming the cavity 32 in the propellant 30 in the state of the parts before assembly, it is possible to obtain a constant impulse bit from the start of operation to during continuous operation.

[0027] By setting the taper angle α of the cavity 32 to be formed to 15° to 85°, preferably 15° to 50°, and more preferably 30°, the shape of the depression formed by continuous operation when the impulse bit is maximized can be reproduced, so that it is possible to obtain the maximum impulse bit from the start of operation. Also, in the cavity 32 of this shape, the outer edge portion on the cathode side (rear side) and the inner surface near the anode 20 are sublimated with substantially the same amount of change. Therefore, even if the operation continues, the propellant 30 is sublimated while maintaining the shape of the cavity 32 constant. From the above, according to the present embodiment, since the volume of the cavity 32 is kept constant, a decrease in the impulse bit can be suppressed, and a stable impulse bit can be obtained in the long term.

[0028] In PPT1, the relative positions of the anode 20 and the cathode 50 are fixed to each other, the propellant 30 is arranged to be relatively movable with respect to the anode 20, and the propellant 30 is pressed backward by the biasing member 40. With this configuration, when the anode 20 is made of a material that is less likely to be worn out or when the discharge energy is small, that is, when the amount of wear on the rear side of the anode 20 due to the wear of the anode 20 is small compared to the amount of displacement on the front side of the propellant 30 due to the sublimation of the propellant 30, it is possible to suppress the anode 20 from protruding into the cavity 32, so that the shape of the cavity 32 can be maintained. Further, as a result of the anode 20 protruding into the cavity 32, it is possible to avoid the sublimation of the plasma and the exhaust of the plasma from being inhibited.

[0029] Furthermore, in PPT1, the propellant 30 is configured to be pressed backward by the biasing member 40. That is, even if the propellant 30 is sublimated and consumed, the sublimation surface of the propellant 30 with respect to the igniter 60 can be kept constant. Therefore, due to the continuous operation of PPT1, it is possible to suppress the shots from stopping as a result of insufficient sublimation caused by the sublimation surface of the propellant 30 moving away from the igniter 60. As described above, in the present embodiment, the shape of the cavity 32 can be maintained by fixing the anode 20 and pressing only the propellant 30, so that a long-term stable impulse bit can be obtained.

[0030] 2. Second Embodiment With reference to FIG. 4, the PPT1A according to the second embodiment of the present invention will be described. In the following description, the differences from the first embodiment will be mainly described. FIG. 4 is a schematic cross-sectional view of the PPT1A according to the second embodiment of the present invention.

[0031] 2.1 Configuration of the Cathode 50 In this embodiment, the through hole 51 of the cathode 50 also has a tapered shape. Specifically, the plasma emission portion 512 of the through hole 51 is formed in a shape that expands from the front side toward the rear side. The taper angle β of the through hole 51 is 15° to 85°. Specifically, for example, it is 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, and it may also be within the range between any two of the values exemplified here. Further, the taper angle β is preferably 15° to 50°. Specifically, for example, it is 15, 20, 25, 30, 35, 40, 45, 50, and it may also be within the range between any two of the values exemplified here. The taper angle β is more preferably 30°.

[0032] 2.2 Function and Effect According to the PPT1A according to this embodiment, by providing the taper within the above range also in the through hole 51 of the cathode 50, it is possible to suppress a decrease in impulse bits caused by the adhesion and deposition of carbon-based substances derived from the propellant sublimates on the wall surface of the plasma emission portion 512.

[0033] 3. Modification Example A modification example based on the above-described embodiment will be described.

[0034] 3.1 Arrangement Configuration The PPT does not have to be coaxially arranged as long as a discharge space can be formed by the anode 20, the propellant 30, and the cathode 50. Specifically, if a part of the cavity 32 of the propellant 30 is adjacent to the anode 20 and a part of the through hole 51 of the cathode 50 communicates with the cavity 32, it can be arranged offset in a direction perpendicular to the axial direction.

[0035] 3.2 Fixing Member 10 In the above embodiment, one fixing member 10 fixes the anode 20 and the cathode 50. However, a first fixing member for fixing the anode 20 and a second fixing member for fixing the cathode 50 may be provided respectively. Further, a third fixing member for supporting the biasing member 40 may be provided. Alternatively, without providing the fixing member 10, the anode 20 and the cathode 50 may be directly attached to the members included in the spacecraft (e.g., artificial satellite) on which the PPT1 (1A) is mounted.

[0036] 3.3 Cathode 50 The cathode 50 may not be arranged to accommodate the propellant 30, that is, the through hole 51 may not have the propellant accommodation portion 511, and the propellant 30 and the cathode 50 may be arranged to be in contact with each other. Also in this case, at the boundary between the cavity 32 and the through hole 51, it is preferable that the inner diameter of the through hole 51 is smaller than the inner diameter of the cavity 32.

[0037] 3.4 Biasing member 40 The biasing member 40 may be arranged such that, for example, the rear side of the biasing member 40 is supported by the cathode 50 and the propellant 30 is pulled on the front side of the biasing member 40. Also with this configuration, the propellant 30 can be biased in the rearward direction.

[0038] 4. Experiment Hereinafter, the experimental results regarding the influence on the impulse bit by the formation of the cavity according to the above-described embodiment and the comparison with the electromagnetic acceleration type parallel plate PPT will be described.

[0039] 4.1 Regarding the consumption of the propellant and the change in the impulse bit In this experiment, the consumption of the propellant and the change in the impulse bit were investigated. Using a propellant with a sublimation surface diameter of 7 mm and no cavity formed in advance, the impulse bit up to 80,000 shots was measured.

[0040] The measurement results in the case of a discharge energy of 8 J are shown in Fig. 5. Fig. 5 is a graph showing the change in impulse bit with respect to the number of shots. The horizontal axis represents the number of shots, and the vertical axis represents the magnitude of the impulse bit (μNs: micro-newton seconds). As can be seen from this graph, the impulse bit increased up to about 30,000 shots and then tended to be kept constant.

[0041] Also, the cross-sectional views of the propellant in each shot are shown in Fig. 6. Fig. 6 is a cross-sectional view of the propellant 30 during the experiments at 10,000 shots, 30,000 shots, 50,000 shots, and 80,000 shots. By continuous operation, it was found that a bell-shaped depression (dashed line) was formed. In the depression formed by operation at 10,000 shots during the rising process of the impulse bit, the depth of the depression in the axial direction was 3.9 mm. At 30,000 shots when the impulse bit began to stabilize, the depth of the depression was 4.9 mm, then at 50,000 shots it was 6.7 mm, and at 80,000 shots it was 5.8 mm. Therefore, it was found that the impulse bit stabilizes when the depth of the depression of the propellant is about 4.9 - 6.7 mm. The taper angle of the depression at this time was about 27 - 36°.

[0042] 4.2 Comparison of Impulse Bits with and without Cavity Formation In this experiment, continuous operation was performed using a propellant without a formed cavity and a propellant with a frustum-shaped cavity with a taper angle of 30° formed in advance, and the transition of the impulse bit was compared.

[0043] The measurement results in the case of a discharge energy of 8 J are shown in Fig. 7. Fig. 7 is a graph showing the results of a comparative experiment of impulse bits with and without a cavity. In the case of a propellant without a formed cavity, the impulse bit at the start of operation was low, and the impulse bit increased up to about 20,000 shots and then maintained approximately a constant value. On the other hand, in the case of a propellant with a cavity formed in advance, it was found that a high impulse bit could be obtained from the start of operation and an approximately constant impulse bit was maintained thereafter.

[0044] 4.3 Comparison with electromagnetic acceleration type parallel plate PPT In this experiment, an electromagnetic acceleration type parallel plate PPT (Parallel plate PPT) with an input energy of about 2J having a structure as disclosed in Patent Document 1 and a PPT of the same 2J level in which a cavity is formed in the propellant and a taper is formed on the cathode (equivalent to PPT1A described above with reference to Fig. 4: Propellant with taper, Chanel with taper - Case, hereinafter referred to as PPT with cavity and taper) were compared in terms of their operating states. In this experiment, the taper angle of the cavity formed in the propellant is about 30°.

[0045] Fig. 8 is a graph showing the results of a comparative experiment between an electromagnetic acceleration type parallel plate PPT and a PPT with cavity and taper. In Fig. 8, the vertical axis represents the impulse bit (μNs), and the horizontal axis represents the number of shots. As can be seen from Fig. 8, the impulse bit of the PPT with cavity and taper (i.e., 2J - level PPT1A) was about three times larger than that of the electromagnetic acceleration type parallel plate PPT at the start of operation.

[0046] Also, although the impulse bit of the PPT with cavity and taper tended to decrease after the start of operation, it operated stably for 90,000 shots or more. Therefore, in terms of the number of operations, it also meets the specification standards of the target small demonstration satellite.

[0047] Moreover, the average impulse bit at 90,000 shots was about 21.2 μNs for the electromagnetic acceleration type parallel plate PPT and about 68.7 μNs for the PPT with cavity and taper, and the latter was about 3.2 times larger than the former. Therefore, it can be said that the PPT with cavity and taper according to this experiment was able to improve the impulse bit of the 2J - level PPT.

[0048] 4.4 Conclusion From the above results, it was found that if a cavity with a taper angle of about 30° is pre-formed in the state of the parts before PPT assembly, an effect similar to the depression formed when obtaining the maximum impulse bit by continuous operation for a general propellant without a cavity can be reproduced. Therefore, by forming a cavity in the propellant in the state of the parts before operation and assembly, a high impulse bit can be obtained from the first shot, so a stable impulse bit can be achieved.

Explanation of Signs

[0049] 1 : PPT 1A : PPT 10 : Fixed member 11 : Base part 12 : Anode fixing part 13 : Cathode fixing part 20 : Anode 30 : Propellant 31 : Anode housing part 32 : Cavity 40 : Biasing member 50 : Cathode 51 : Through hole 52 : Igniter installation hole 60 : Igniter 70 : Capacitor 511 : Propellant housing part 512 : Plasma discharge part 513 : Stopper part α : Taper angle β : Taper angle D : Sublimation surface diameter

Claims

1. A pulse plasma thruster comprising an anode, a propellant, and a cathode, wherein the anode, the propellant, and the cathode are arranged along a first direction, the relative positions of the anode and the cathode are fixed to each other, the propellant is relatively movable along the first direction with respect to the anode, and an anode housing portion is formed on one side in the first direction and a cavity is formed on the other side, the anode is disposed in the anode housing portion, the cavity has an opening on the other side and is formed in a shape that expands from the one side toward the other side, and is configured to communicate with the anode housing portion so as to be adjacent to the anode, the cathode has a through hole formed therein, and at least a part of the through hole is arranged to communicate with the cavity the propellant is biased toward the other side, the pulse plasma thruster.

2. The pulse plasma thruster according to claim 1, wherein the anode is rod-shaped, and the anode housing portion is a hole penetrating in the first direction from one end on the one side of the propellant to the cavity, the pulse plasma thruster.

3. The pulse plasma thruster according to claim 1 or claim 2, further comprising a biasing member, wherein the biasing member is configured to bias the propellant toward the other side, the pulse plasma thruster.

4. The pulse plasma thruster according to claim 1, wherein a taper angle of the cavity with respect to the first direction is 30°, the pulse plasma thruster.

5. The pulse plasma thruster according to claim 1, wherein at a boundary between the cavity and the through hole, an inner diameter of the through hole is smaller than an inner diameter of the cavity, the pulse plasma thruster.

6. The pulse plasma thruster according to claim 1, wherein the through hole is formed in a shape that expands from the one side toward the other side, the pulse plasma thruster.

7. The pulse plasma thruster according to claim 1, wherein a material of the anode is tungsten, the pulse plasma thruster.

8. The pulse plasma thruster according to claim 1, A pulse plasma thruster in which the amount of loss of the other side of the anode due to the depletion of the anode is small with respect to the amount of displacement of the one side of the propellant due to the sublimation of the propellant.

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