Single-propellant thruster

Abstract

To provide a monopropellant thruster which comprises catalysts in a catalyst layer and enables whole of the catalysts to be substantially uniformly heated up to a catalyst reaction temperature from normal temperature by small power in a short time, and enables an initial temperature (reaction start temperature) of the catalyst layer to be exactly set.SOLUTION: A monopropellant thruster 100 comprises a cylindrical catalyst layer 10, a thruster main body 20, a heater 30 and a thermocouple 40. The catalyst layer 10 is formed of a catalyst C for catalyst-decomposing a liquid propellant 1. The thruster main body 20 has a hollow cylindrical combustion chamber 22 having the catalyst layer therein. A heat generation portion 32a of the heater 30 and a temperature detection portion 42a of the thermocouple 40 are fixed to a cylindrical outer periphery 22a of the combustion chamber. Also, the heat generation portion 32 of the heater and the thermocouple 40 are spirally wound around the cylindrical outer periphery 22a with axial an axial interval, and soldered to the cylindrical outer periphery at the same pitches.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a single - liquid thruster used for spacecraft and the like.

Background Art

[0002] A "single - liquid thruster" is a propulsion device that uses a single liquid propellant as fuel. The single - liquid thruster depends on a chemical reaction to generate thrust. When the chemical bonds of the molecules of the chemical substances constituting the liquid propellant are broken, energy corresponding to the bond energy is released, and high - temperature gas is ejected, thereby propelling by the recoil. Such a single - liquid thruster is disclosed in, for example, Patent Document 1.

[0003] A single - liquid thruster (hereinafter, "thruster") has a catalyst layer composed of a catalyst for catalytically decomposing a liquid propellant. However, since the activity of the catalyst depends on its temperature, it is necessary to pre - heat (preheat) the catalyst layer to enhance the activity of the catalyst before operating the thruster. For this purpose, for example, Patent Document 2 is disclosed.

[0004] The "catalytic decomposition thruster" of Patent Document 2 includes a catalyst layer having a catalyst for catalytically decomposing a liquid propellant, a heating device for heating the catalyst layer, and an injector for supplying the liquid propellant to the catalyst layer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 2 discloses a heating device, for example, a tape heater made by processing an electric heating wire into a tape shape. Furthermore, the heating device is installed by wrapping the tape heater around the outside of the reactor (hereinafter referred to as the "combustor") near the catalyst layer, and heating the catalyst layer using the heat transfer of the combustor. However, conventional heating devices had the following problems:

[0007] (1) In order to achieve a stable catalytic reaction, it is necessary to ensure sufficient contact time between the liquid propellant and the catalyst, to preheat the entire catalyst substantially uniformly, and to accurately set the initial temperature of the catalyst (reaction start temperature). The catalyst layer in Patent Document 2 is a thin disc shape, with a thin thickness compared to its diameter, resulting in a short contact time with the liquid propellant. Furthermore, because only the outer periphery of the disc-shaped catalyst layer is heated, uniform preheating of the entire catalyst layer is difficult. Furthermore, because there is a heating device (tape heater) on the outer periphery of the catalyst layer, temperature measurement is only possible on the upstream or downstream side of the catalyst layer. Therefore, accurately setting the initial temperature (reaction start temperature) of the catalyst layer is difficult. Furthermore, it is necessary to continuously measure the reactor temperature even while the thrusters are operating after the catalytic reaction has started. Even if the temperature measuring part of a thermocouple is fixed to the upstream or downstream side of the catalyst layer, the vibration load during rocket launch, or thermal expansion and vibration during repeated use, may cause the fixing point (e.g., brazing) to detach. Furthermore, if the catalyst layer is made thicker to ensure sufficient contact time between the liquid propellant and the catalyst, and the entire catalyst layer is surrounded by tape heaters, it becomes difficult to attach thermocouples or similar devices.

[0008] (2) Monopropellant thrusters used in spacecraft and the like are required to be usable repeatedly for several thousand to over 10,000 cycles. Therefore, they are required to be able to heat the catalyst layer in the shortest possible time within a limited power range, and to be robust enough to prevent damage. In Patent Document 2, only the outer periphery of the disc-shaped catalyst layer is heated, resulting in significant heat dissipation from other areas and low thermal efficiency.

[0009] (3) The thruster operation causes the reaction chamber (hereinafter referred to as the "combustion chamber") to become hot in a short time. For example, the combustion chamber is heated from approximately 160°C to over 700°C within 60 seconds after the start of the reaction. Conventional tape heaters (or ribbon heaters) have heating wires sewn into a ribbon-like strip of cloth, and tape heaters with heat resistance of 700°C or higher use, for example, silica glass cloth with a high heat resistance temperature. However, the coefficient of thermal expansion of the metal that makes up the combustor (for example, stainless steel) is greater than that of silica glass cloth. Therefore, in order to withstand thousands of uses, or even more than 10,000 cumulative uses, it is necessary to loosely wrap the tape heater before heating (for example, at room temperature) to prevent excessive tensile stress from being generated in the tape heater at high temperatures (above 700°C).

[0010] (4) Before the thruster can be activated, the entire catalyst layer must be heated from room temperature to the catalytic reaction temperature (e.g., about 160°C) in a short time (e.g., within 10 minutes). However, conventional heating devices (for example, tape heaters) are loosely wrapped around the outside of the combustor, resulting in significant heat loss (i.e., heat dissipation) from the tape heater to the combustor, and excessive power is required for short-term heating. (5) To solve this problem, it is also conceivable to construct a ring-shaped or rod-shaped heating element from a metal having the same coefficient of thermal expansion as the combustor, incorporate a heater inside it, and fix (for example, fasten) the heating element to the outer surface of the combustor. However, in this case, if the size of the heating element is smaller than the heating area, the entire catalyst cannot be heated, and heating will take a long time. Also, if the heating element is made larger to surround the entire catalyst layer, the heat capacity of the heating element becomes excessive, making short-time heating difficult.

[0011] The present invention was devised to solve the above-mentioned problems. Specifically, the first objective of the present invention is to provide a monopropellant thruster that can heat (preheat) the entire catalyst layer from room temperature to the catalytic reaction temperature substantially uniformly in a short time with less power than conventional thrusters, and that can accurately set the initial temperature (reaction start temperature) of the catalyst layer. The second objective is to provide a robust monopropellant thruster that can be used stably without damage even when the combustion chamber is repeatedly heated from the catalytic reaction temperature to high temperatures for thousands to more than 10,000 cumulative times. [Means for solving the problem]

[0012] According to the present invention, a cylindrical catalyst layer comprising a catalyst for catalytically decomposing a liquid propellant, A thruster body having a hollow cylindrical combustion chamber containing the catalyst layer inside, A heater with a heating element fixed to the cylindrical outer surface of the combustion chamber, The thermocouple comprises a thermocouple with a temperature detection unit fixed to the cylindrical outer surface, The heating element of the heater is wound in a spiral shape around the cylindrical outer surface, covering the entire length of the catalyst layer, and brazed to the cylindrical outer surface. A one-propellant thruster is provided, in which the thermocouple is wound spirally around the cylindrical outer surface of the heater at the same pitch as the heating element, at an axial distance from the heating element, and brazed to it. [Effects of the Invention]

[0013] According to the configuration of the present invention, the heating element of the heater is wound in a spiral shape around the entire length of the catalyst layer on the cylindrical outer surface of the combustion chamber and brazed to the cylindrical outer surface. This makes it possible to heat (preheat) the entire catalyst layer from room temperature to the catalytic reaction temperature substantially uniformly in a short time with less power than in the conventional method.

[0014] Also, the thermocouple is spirally wound around the cylindrical outer peripheral surface of the combustion chamber at an axial interval from the heat generating part of the heater with the same pitch as the heat generating part and brazed thereto. As a result, since the temperature detection part is brazed to the cylindrical outer peripheral surface of the combustion chamber, the outer surface temperature of the combustion chamber can be measured without being directly affected by the heat generating part of the heater, and the initial temperature (reaction start temperature) of the catalyst layer can be accurately set.

[0015] Furthermore, since both the heater and the thermocouple are spirally wound around the cylindrical outer peripheral surface and brazed to the cylindrical outer peripheral surface, their respective outer surfaces substantially have the same temperature as the cylindrical outer peripheral surface of the combustion chamber and can expand and contract thermally integrally. As a result, since the internal stress generated in the brazed part is small, the combustion chamber has robustness that can be stably used without damage even when repeatedly heated from the catalyst reaction temperature to a high temperature, thousands of times to more than 10,000 times in total.

Brief Description of the Drawings

[0016] [Figure 1] It is a first embodiment diagram of a monopropellant thruster according to the present invention. [Figure 2] It is a diagram showing the winding state of the sheath heater and the sheath thermocouple with respect to the cylindrical outer peripheral surface of the combustion chamber. [Figure 3] It is a second embodiment diagram of a monopropellant thruster according to the present invention. [Figure 4] It is a comparison diagram of the heating rates of the invention product and the conventional product. [Figure 5] It is a diagram showing the temperature of the catalyst layer and the time course of the thrust during the injection test of the invention product.

Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. In the drawings, the same reference numerals are given to the common parts in each figure, and duplicate explanations are omitted.

[0018] FIG. 1 is a first embodiment diagram of a monopropellant thruster 100 according to the present invention, (A) is an overall configuration diagram, and (B) is a partial enlarged view.

[0019] In Figure 1(A), the monopropellant thruster 100 comprises a catalyst layer 10 and a thruster body 20. In this figure, 2 is the propellant tank, 4 is the propellant valve, and 6 is the fixing bracket.

[0020] The propellant tank 2 contains liquid propellant 1. Liquid propellant 1 is, for example, hydrazine or hydroxylammonium nitrate ("HAN")-based liquid propellant. The propellant tank 2 and the propellant valve 4 are connected via a propellant supply pipe 3, and liquid propellant 1 is supplied from the propellant tank 2 to the propellant valve 4. The propellant valve 4 is a flow-controllable solenoid valve that supplies liquid propellant 1 to the thruster body 20 via the propellant tube 5. The fixing bracket 6 is secured to a fixing part (not shown) of a spacecraft or the like with bolts or the like. The fixing bracket 6 also secures the propellant valve 4 to its upstream side (left side in the diagram). Furthermore, the fixing bracket 6 has multiple support arms 6a extending downstream (right side in the diagram), the tips of which are fixed to the upstream outer surface of the thruster body 20, thereby supporting the thruster body 20.

[0021] In Figure 1(B), the catalyst layer 10 of the monopropellant thruster 100 consists of a catalyst C that catalytically decomposes the liquid propellant 1. Catalyst C is a granular catalyst, such as an alumina-supported catalyst bearing a precious metal (Pt, Ir, etc.). In this example, the catalyst layer 10 is cylindrical. Furthermore, the total length L of the catalyst layer 10 is longer than its diameter D to ensure sufficient contact time between the liquid propellant 1 and the catalyst C. In the embodiments described later, the ratio L / D of the total length L to the diameter D is 3 or greater.

[0022] The thruster body 20 has a hollow cylindrical combustion chamber 22 that houses a catalyst layer 10 inside. Inside the combustion chamber 22, permeable meshes 24a and 24b are fixed to the upstream and downstream sides of the catalyst layer 10 to prevent the catalyst C from scattering. The thruster body 20 further includes a propellant supply unit 25 to which the propellant tube 5 is connected, and an injection nozzle 26 for injecting the reaction gas G generated in the combustion chamber 22 to the outside. In this example, the injection nozzle 26 is of a straight type, so that the injection direction of the reaction gas G coincides with the axial direction Z of the thruster body 20. The combustion chamber 22, propellant supply unit 25, and injection nozzle 26 are made of heat-resistant metal (e.g., stainless steel, titanium alloy) that can withstand the temperature of the generated reaction gas G (e.g., 700°C or higher).

[0023] In Figure 1(B), a pressure detection port 27 is provided upstream of the injection nozzle 26 in the combustion chamber 22. A pressure detection tube (not shown) is attached to the pressure detection port 27 to detect the pressure upstream of the injection nozzle 26. By detecting the upstream pressure of the injection nozzle 26, the thrust of the monopropellant thruster 100 during the injection test can be calculated.

[0024] In Figure 1(A), the monopropellant thruster 100 is further equipped with a heater 30 and a thermocouple 40. In this example, heater 30 is a sheathed heater, and thermocouple 40 is a sheathed thermocouple. Note that heater 30 is not limited to a sheathed heater and may be other heating elements. Similarly, thermocouple 40 is not limited to a sheathed thermocouple and may be other temperature measuring elements. The following describes the case where the heater 30 is a sheathed heater 30 and the thermocouple 40 is a sheathed thermocouple 40.

[0025] Figure 2 shows the state in which the sheath heater 30 and the sheath thermocouple 40 are wrapped around the cylindrical outer surface 22a of the combustion chamber 22.

[0026] A "sheath heater" refers to a heater covered with a sheath. In Figure 2, the sheath heater 30 of the present invention has a heater sheath 32 (outer pipe) with an outer diameter that can be wrapped around the cylindrical outer surface 22a of the combustion chamber 22 at least once, and a heater power input section 34 provided at the end of the heater sheath 32. In the embodiment described later, the outer diameter of the heater sheath 32 is 1.5 mm.

[0027] The heater sheath 32 consists of a heating element 32a provided near its tip and a power supply element 32b located between the heating element 32a and the heater power input element 34. The heater power input section 34 has an input terminal 34a for power supply. The heating element 32a is filled with a heating wire and electrical insulating material on its inside. The power supply unit 32b is filled with a conductor that connects the input terminal 34a and the heating element of the heating element 32a, as well as electrical insulating material. The heater power input section 34 should be fixed to a fixed part (not shown) of a spacecraft or the like, at a location away from the combustion chamber 22, which becomes hot.

[0028] The heater sheath 32 is made of heat-resistant metals such as stainless steel, Inconel, and titanium alloy. An example of an electrical insulating material is magnesium oxide. The heating element is, for example, a linear or strip-shaped nichrome wire.

[0029] In the present invention, the heating portion 32a of the heater sheath 32 is wound spirally around the gap of the heater 30 (heater sheath 32) in the area surrounding the entire length of the catalyst layer 10 on the cylindrical outer surface 22a of the combustion chamber 22, and is brazed to the cylindrical outer surface 22a. Furthermore, the heating element 32a is pre-bent into a spiral shape so as to be in close contact with the cylindrical outer surface 22a, and the bent portion is brazed to the cylindrical outer surface 22a.

[0030] A "sheathed thermocouple" refers to a thermocouple that is covered with a sheath. In Figure 2, the sheathed thermocouple 40 of the present invention has a thermocouple sheath 42 (outer pipe) with an outer diameter that can be wrapped around the cylindrical outer surface 22a of the combustion chamber 22, and an output terminal portion 44 provided at the end of the thermocouple sheath 42. The outer diameter of the thermocouple sheath 42 is preferably smaller than the outer diameter of the heater sheath 32, and in the embodiment described later, it is 1.0 mm.

[0031] The output terminal section 44 has an output terminal 44a for temperature detection. The thermocouple sheath 42 consists of a temperature detection unit 42a provided near its tip and a compensating conductor unit 42b located between the temperature detection unit 42a and the output terminal unit 44. The temperature detection unit 42a is filled with a thermocouple and electrical insulating material inside. The compensating wire section 42b is filled with a compensating wire that connects the thermocouple and the output terminal 44a, as well as electrical insulating material. The output terminal section 44 should be fixed to a fixed part (not shown) of a spacecraft or the like, at a location away from the combustion chamber 22, which becomes hot.

[0032] The sheath thermocouple 40 is brazed to the cylindrical outer surface 22a of the sheath heater 30, at a distance in the axial direction Z from the heating element 32a, by being wound spirally around it with the same pitch P as the heating element 32a.

[0033] In the present invention, the temperature detection part 42a of the thermocouple sheath 42 is brazed to the cylindrical outer surface 22a of the combustion chamber 22 at a different position (temperature detection position X) from the heater sheath 32 of the sheath heater 30. Furthermore, the compensating wire portion 42b near the temperature detection portion 42a is also separated from the heater sheath 32, spirally wound around the cylindrical outer surface 22a, and integrally brazed.

[0034] The temperature detection position X is preferably the cylindrical outer surface 22a corresponding to the center of the entire length L of the catalyst layer. The temperature detection position X may also be on the upstream or downstream side of the cylindrical outer surface 22a corresponding to the catalyst layer 10. Furthermore, the sheathed thermocouple 40 is not limited to one unit; multiple units may be used.

[0035] The winding direction and axial pitch Z of the spiral portion of the heating element 32a of the sheath heater 30 and the spiral portion of the temperature detection element 42a and compensating wire 42b of the sheath thermocouple 40 should be the same so as not to come into contact with each other.

[0036] The number of turns of the heating element 32a of the sheath heater 30 around the cylindrical outer surface 22a is preferably at least one turn (one rotation) in order to heat the entire length L of the catalyst layer. Furthermore, the pitch P of the heating element 32a should be at least twice the outer diameter d of the heating element 32a so that at least one thermocouple sheath 42 can be wound around it. Furthermore, for example, when three thermocouple sheaths 42 are wound between the pitch P of the heating element 32a, it is preferable that the pitch d be at least four times the outer diameter d of the heating element 32a. Even if this pitch P is constant, it may differ between the upstream and downstream sides in the axial direction Z.

[0037] Figure 3 is a diagram of a second embodiment of the mono-propellant thruster 100 according to the present invention. In this figure, the injection nozzle 26 is of the cant type, in which the injection direction of the reaction gas G is perpendicular to the axial direction Z of the thruster body 20. The other configurations are the same as in the first embodiment.

[0038] (Example 1) A monopropellant thruster 100 of the first embodiment shown in Figure 1 was manufactured. The specifications of this monopropellant thruster 100 are as follows. Diameter of combustion chamber 22: 10mm Combustion chamber 22 length: 35mm Type of catalyst C: Alumina-supported catalyst with a precious metal (Pt, Ir, etc.) supported on it. Form of catalyst C: Granular catalyst Reaction initiation temperature of catalyst C: 150°C or higher Outer diameter of sheath heater 30 (heater sheath 32): 1.5 mm Outer diameter of sheathed thermocouple 40 (thermocouple sheath 42): 1.0 mm Type of solder: Gold solder

[0039] Figure 4 is a comparison diagram of the heating speeds of the one-propellant thruster 100 of the present invention (hereinafter referred to as the "invention") and a conventional one-propellant thruster (hereinafter referred to as the "conventional product"). The invention is a mono-liquid thruster 100 of the first embodiment shown in Figure 1. In contrast, conventional products consist of a pair of heater holders, each having a semi-cylindrical recess, which are fitted into the cylindrical circumferential surface of the combustion chamber to fix the pair of heater holders, and heaters are inserted into each heater holder.

[0040] Figure 4 shows that the time it took for the combustion chamber surface temperature to reach 160°C from room temperature by heater heating in the inventive product was approximately 360 seconds, compared to approximately 1200 seconds for the conventional product. Furthermore, the required power consumption of the inventive product was approximately 0.81 Wh, compared to approximately 1.60 Wh for the conventional product. These results show that monopropellant thrusters need to heat the catalyst layer 10 as early as possible within a limited power range, and the invented product can raise the temperature with approximately half the power consumption of conventional products. Furthermore, in order to achieve a stable combustion reaction, it is necessary to preheat the entire catalyst layer, and therefore it is necessary to accurately control the initial temperature of the catalyst layer. In this invention, the preheating temperature of the catalyst layer 10 can be controlled with high precision by directly measuring the combustion chamber surface temperature of the heating region.

[0041] (Example 2) Figure 5 shows the temperature of the catalyst layer 10 and the time course of the thrust during an injection test of the invention. As shown in this figure, the temperature of the catalyst layer 10 reaches approximately 450°C after 10 seconds and approximately 700°C after 60 seconds following the start of liquid propellant 1 supply. It can also be seen that the thrust remains constant at approximately 0.5N immediately after the start of liquid propellant 1 supply. The thrust remains constant because, although the pressure increases as the reaction progresses from the start of injection, there is a point where the energy generated by the combustion gas, the velocity of the injected gas (thrust), and the amount of heat dissipated are in balance. In the case of Figure 5, this balance occurs at 0.5 N, resulting in a constant thrust value.

[0042] Furthermore, after repeating pulsed injection more than 32,000 times, there was no peeling of the heating element 32a of the sheath heater 30, and it remained usable. The heating element 32a of the sheath heater 30 reached a high temperature of over 700°C, but it maintained its integrity. Furthermore, "pulsed injection" can be achieved by turning the propellant valve shown in Figure 1(A) ON / OFF at regular time intervals. For example, by repeatedly turning it ON for 0.1 seconds and OFF for 0.9 seconds, a pulsed injection with a 1-second cycle can be achieved.

[0043] According to the embodiments of the present invention described above, since the total length L of the cylindrical catalyst layer 10 is longer than the diameter D, it is possible to ensure sufficient contact time between the liquid propellant 1 and the catalyst C.

[0044] Furthermore, the heating element 32a of the heater 30 (sheath heater 30) is wound spirally around the area surrounding the entire length L of the catalyst layer on the cylindrical outer surface 22a of the combustion chamber 22 and brazed to the cylindrical outer surface 22a. This allows the entire catalyst of the catalyst layer 10 to be heated (preheated) substantially uniformly from room temperature to the catalytic reaction temperature in a short time with less power than in the conventional method.

[0045] Furthermore, the thermocouple 40 (sheath thermocouple 40) is brazed to the cylindrical outer surface 22a of the combustion chamber 22, at an axial distance from the heating element 32a of the sheath heater 30, by being wound spirally around it with the same pitch P as the heating element 32a. As a result, the temperature detection unit 42a is brazed to the cylindrical outer surface 22a, so the temperature of the cylindrical outer surface 22a can be measured without being directly affected by the heating element 32a of the sheath heater 30, and the initial temperature (reaction start temperature) of the catalyst layer 10 can be accurately set.

[0046] Furthermore, since both the sheath heater 30 and the sheath thermocouple 40 are spirally wrapped around the cylindrical outer surface 22a and brazed, their respective outer surfaces (sheaths) reach substantially the same temperature as the cylindrical outer surface 22a of the combustion chamber 22, allowing them to expand and contract integrally. As a result, the internal stress generated at the brazed joint is small, providing robustness that allows the combustion chamber 22 to be repeatedly heated from catalytic reaction temperature to high temperatures for thousands to over 10,000 cumulative times without damage.

[0047] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. [Explanation of Symbols]

[0048] C Catalyst, G Reaction gas, P Pitch, X Temperature detection position, Z Axis axis, 1. Liquid propellant, 2. Propellant tank, 3. Propellant supply pipe, 4. Propellant valve, 5 propellant tube, 6 fixing bracket, 6a support arm, 10 catalyst layer, 20 Thruster body, 22 Combustion chamber, 22a Cylindrical outer surface, 24a, 24b Net, 25 Propellant supply unit, 26 Spray nozzle, 27 Pressure detection port, 30 Heater (sheath heater), 32 Heater sheath, 32a Heating element, 32b Power supply unit, 34 Heater power input unit, 34a Input terminal, 40 Thermocouple (sheathed thermocouple), 42 Thermocouple sheath, 42a Temperature detection unit, 42b Compensation wire unit, 44 Output terminal unit, 44a Output terminal, 100 Single-propellant thruster

Claims

1. A cylindrical catalyst layer consisting of a catalyst that catalytically decomposes liquid propellant, A thruster body having a hollow cylindrical combustion chamber containing the catalyst layer inside, A heater with a heating element fixed to the cylindrical outer surface of the combustion chamber, The thermocouple comprises a thermocouple with a temperature detection unit fixed to the cylindrical outer surface, The heating element of the heater is wound in a spiral shape around the cylindrical outer surface, covering the entire length of the catalyst layer, and brazed to the cylindrical outer surface. A one-propellant thruster, wherein the thermocouple is wound spirally around the cylindrical outer surface of the heater at the same pitch as the heating element, at an axial distance from the heating element of the heater, and brazed to it.

2. The heater is a sheath heater having a heater sheath with an outer diameter that can be wrapped around the cylindrical outer surface of the combustion chamber one or more times, and a heater power input section provided at the end of the heater sheath. The monopropellant thruster according to claim 1, wherein the heater sheath comprises a heating element provided near its tip and a power supply element located between the heating element and the heater power input element.

3. The one-component thruster according to claim 2, wherein the heating element is pre-bent in a spiral shape so as to be in close contact with the cylindrical outer surface, and the bent portion is brazed to the cylindrical outer surface.

4. The thermocouple is a sheathed thermocouple having a thermocouple sheath with an outer diameter that can be wrapped around the cylindrical outer surface of the combustion chamber in the gap of the heater, and an output terminal portion provided at the end of the thermocouple sheath. The monopropelled thruster according to claim 1, wherein the thermocouple sheath comprises a temperature detection unit provided near its tip and a compensating conductor unit located between the temperature detection unit and the output terminal unit.

5. The temperature detection unit is brazed to the cylindrical outer surface at a position different from that of the heater. The compensating wire portion near the temperature detection portion is separated from the heater and wound spirally around the cylindrical outer surface and brazed, as described in claim 4, for the one-propellant thruster.

6. The winding direction and axial pitch of the helical portion of the heater and the thermocouple are the same. The monopropellant thruster according to claim 1, wherein the pitch is constant or differs between the upstream and downstream sides.

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