JP4815601B2 - Electric thermal rocket propulsion device - Google Patents

Description

  The present invention relates to a spacecraft propulsion device, and more particularly to a rocket propulsion device for maintaining or changing the position, posture, and speed of a spacecraft to a predetermined value.

  Spacecraft such as artificial satellites are equipped with small, low-thrust thrusters for maintaining or changing orbits and controlling attitude. The propulsion device has a chemical propulsion device that uses the chemical energy of the propellant as a propulsion source. However, the performance of the chemical propulsion device is limited by the type of propellant, and the propulsion force (specific thrust) per propellant consumption rate is not high.

In order to eliminate the poor performance of chemical propulsion devices, electric propulsion devices that electrically heat or accelerate the propellant have been put into practical use. An electrothermal propulsion device is a type of electric propulsion device that obtains propulsive force by electrically heating a propellant and converting the thermal energy obtained by the propellant into kinetic energy through a nozzle. The main electric-heated propulsion units in practical use include an arc jet propulsion unit that heats the propellant by arc discharge, and heat transfer to the propellant by heat conduction and radiation via a heat exchanger using an electric heater. There are two types of resist jet propulsion machines that transmit hydrazine, and hydrazine is mainly used as a propellant.
PCT / JP2006-309443 Mitat A. Birkan, “Arcjets and Arc Heaters: An Over view of Research Status and Needs”, JOURNAL OF PROPULSION AND POWER Vol. 12, no. 6, (1996) Junichi Kuriki, Yoshihiro Arakawa, Introduction to Electric Propulsion Rockets, page 92, University of Tokyo Press (2003)

Problems to be solved by the invention

  Hydrazine has been mainly used as a propellant for electrothermal propulsion machines because of its long experience in use. However, since hydrazine is extremely toxic and needs to be considered for its effects on the human body or the environment, handling procedures on the ground are complicated, and safety measures and processing are costly. Also, when hydrazine is used as a propellant for an electrothermal propulsion device, it must first be decomposed with a catalyst, which complicates the system and causes catalyst loss due to vibration during launch and catalyst penetration into the propellant injector. The reliability of the propulsion unit is also reduced due to concerns such as a decrease in flow rate and catalyst deterioration due to long-term use. Furthermore, Shell405, which is an effective catalyst for hydrazine decomposition, relies on overseas production, and there is no guarantee of stable availability. From the above, the electrothermal propulsion device using hydrazine as a propellant has many problems.

  In order to solve these problems, the inventors of the present invention used a chemical propellant using hydroxylammonium nitrate (HAN) as an oxidant and ether or the like as fuel in PCT / JP2006-309443, or the like. A chemical rocket is proposed. According to PCT / JP2006-309443, there is an effect that a propellant and a propulsion device that are low in toxicity and do not require a catalyst are established, but on the other hand, a complicated apparatus such as an extra oxidant tank is required, There is also the problem of low performance limitations due to chemical reactions.

In view of the above problems, an object of the present invention is to propose a new effective substance as an option for a propellant for an electrothermal propulsion device, and to provide an electrothermal propulsion apparatus using the substance.

Means to solve the problem

In view of the above problems, the inventors have completed the present invention by devising an electrothermal propulsion device using an organic compound or an organic compound in combination as a propellant for an electrothermal propulsion device and using the propellant. It was. That is, the present invention is a propellant that uses any one or a mixture of two or more selected from ethers, natural gas, and petroleum gas having a vapor pressure of 1 atm or more at room temperature stored in a tank. However, by opening a valve connected to the propulsion unit from the storage tank, the propellant itself is supplied to the propulsion unit by the vapor pressure of the propellant itself, and then given thermal energy by arc discharge or an electric heater in the propulsion unit. An electrothermal propulsion device is characterized in that the propellant obtained by obtaining a propulsive force by being gas-dynamically accelerated through a nozzle.

  The present invention is the electrothermal propulsion device according to claim 1, wherein dimethyl ether is used as a propellant.

The invention's effect

  The present invention can provide an electrothermal propulsion device in which the propellant is replaced with an organic compound from the current hydrazine, thereby solving problems such as handling on the ground and adverse effects on the environment due to the toxicity of the propellant. . In addition, since the electrothermal propulsion device according to the present invention does not require a catalyst, problems of catalyst loss due to vibration, reduction of the propellant flow rate due to the catalyst entering the injector, and deterioration of catalyst performance due to long-term use can be avoided. Reliability is also improved.

  Furthermore, in the present invention, it is not necessary to cause a chemical reaction between the propellant and the oxidant as proposed in PCT / JP2006-309443, and in a satellite environment where electric power can be procured, start and stop and Ease of power can be increased by turning on / off electric power such as arc discharge and adjusting the input power, and high performance represented by specific thrust is achieved, so the position, attitude and speed of the flying object are maintained. Alternatively, sufficient propulsive force can be obtained to change the predetermined.

  Since the organic compound of the present invention is supplied to the working part by its own vapor pressure, it does not require a pressurized gas for supplying a propellant or a gas tank, and as a result, the weight of the propulsion device can be reduced.

  Further, by using the organic compound used as the propellant as a hydrogen carrier of the fuel cell at the same time, a new effect is brought about such that the propellant can be shared by the propulsion system and the power supply system. In particular, dimethyl ether can be converted to hydrogen at a lower temperature than other organic compounds, and is very promising as a hydrogen carrier for fuel cells because it has less impurities such as sulfur compounds.

  An embodiment of the present invention is shown below, but the present invention is not limited to this. In the present invention, ethers, natural gas, and petroleum gas are used as the organic compound. Examples of ethers include, but are not limited to, dimethyl ether, ethyl methyl ether, diethyl ether, ethyl vinyl ether, and the like. Natural gas and petroleum gas are constituents of methane, ethane, propane, butane, etc., and when these are used as propellants, they may be single compounds such as dimethyl ether, ethers, natural gas. It may be used as a mixture of petroleum gas.

  Among these organic compounds, dimethyl ether is most preferred because it is low in toxicity and excellent in handling and storage on the ground, and is less expensive in terms of safety measures and treatment than hydrazine. In addition, since the freezing point of hydrazine is as low as 1.4 ° C., the freezing point of dimethyl ether is as low as −138.5 ° C., so that the propellant can be kept in a liquid state without using a heater to prevent freezing. it can.

  Furthermore, since dimethyl ether has a very low boiling point of −24.8 ° C. and has a vapor pressure of about 6 atm at room temperature, for example, when it is stored in a tank near room temperature, it is a preferable pressure as a supply pressure to the propulsion device autonomously. Is maintained, and a gas for pressurization for pumping a normally required propellant is not required. Furthermore, dimethyl ether can take out hydrogen by reforming and can be converted to hydrogen at a lower temperature than other organic compounds. Since it has features such as low impurities such as sulfur compounds, it is very promising as a hydrogen carrier for fuel cells, and it is possible to share fuel in both the propulsion system and the power supply system.

From the above advantages, the propellant selected by the present invention is preferably dimethyl ether alone or a mixture containing dimethyl ether as a main component. When the propellant is a mixture, the weight ratio of dimethyl ether is preferably 80% or more. Since this electrothermal propulsion device mainly uses electric energy as a propulsion power source and does not use a combustion reaction, an oxidant is not necessary.
The propellant mixed with dimethyl ether is not particularly limited as long as there is no problem with mixing with dimethyl ether, but specific examples include ethers, natural gas, and petroleum gas. If the weight ratio of dimethyl ether is less than 80%, it is not preferable from the standpoint that discharge characteristics are deteriorated and substances such as soot are adversely affected.

  The mass flow rate of the propellant can be selected in a wide range according to the desired propulsive force, but the propulsive force necessary for changing the satellite's orbit, which is the main purpose of the propulsion device, attitude control, etc. In this case, since it is about 1N at the maximum, the range is about 100 mg / second or less. In addition, the power that can be used in outer space is limited, and a low-power electric thermal propulsion device that operates in the range of several tens to 500 W is demanded. Therefore, the power used in the present invention is preferably in the range of several tens to 500 W, and is preferably up to about 3 kW. However, this does not particularly limit the power used for the propulsion device.

  Further, instead of using a method for heating the propellant by electric discharge, the propellant can be heated electrically without using electric discharge by heating the propellant using an electric heater or the like. Furthermore, even if electrical heating cannot be used for some reason, the propellant used in the present invention has a high vapor pressure unlike hydrazine, so propulsion is achieved by converting the pressure into kinetic energy via a nozzle. The function as a machine can be maintained. Therefore, the electrothermal propulsion device of the present invention includes an arc jet mode using arc discharge and a resist jet mode in which a propellant heated by an electric heater and obtained thermal energy is accelerated by gas dynamics through a nozzle to obtain a propulsive force. , Cold jet mode in which propulsion is obtained only by vapor dynamic acceleration of the vapor pressure of the propellant without discharge or heating by an electric heater, and the above three modes can be operated simultaneously in any of the above three modes. Can be used as a multi-mode propulsion device.

  The arc discharge mode is suitable when there is sufficient electric power, and a large driving force can be obtained. The resist jet mode is suitable when the power that can be used is not sufficient, and a moderate driving force can be obtained. In the cold jet mode, it is possible to obtain thrust even when electricity is not available due to power outage or accident. If a heater wire is installed in the gas generator, the resist jet mode is set when the heater is turned on, and the cold jet mode is set when the power is not turned on. The arc jet mode can be combined with the resist jet mode or the cold jet mode, and the maximum propulsive force can be obtained by the combination of the arc jet mode and the resist jet mode.

  An electric heating propulsion device as shown in FIG. 1 was prototyped and an operation test was conducted using dimethyl ether as a propellant. The distance between the discharge electrodes here was set so that the cathode tip was the same as the inlet of the constructor, as shown in FIG. The propellant flow rate is 34 mg / second. By generating an arc discharge using the discharge power source 3 between the cathode 1 and the anode 2, the dimethyl ether is heated and expanded through the nozzle 4, so that the thermal energy of the propellant is converted into kinetic energy and a high-speed jet. As discharged. At this time, dimethyl ether is supplied from the propellant supply port 6 through the swirl vane 7 to the discharge unit in a state where the pressure is reduced to 4 atm by a regulator in order to obtain a stable supply pressure from the propellant tank 5. In the experiment conducted under the above conditions, the discharge current was 12 A, the discharge voltage was 24 V, and it was confirmed that the arc jet propulsion device of the present invention operates at 300 W class.

  The specific thrust of the electrothermal propulsion device and the composition of the exhaust jet when hydrazine, dimethyl ether and methane were used as propellants were analyzed by chemical equilibrium calculation under the conditions of the operating part pressure P = 4 atm and the nozzle expansion ratio ε = 100. 2 and 3 show the results. FIG. 2 shows that the decrease in specific thrust is only a few percent in both cases where dimethyl ether and methane are used as propellants compared to the case where hydrazine is used as a propellant. In order to prevent the propellant from freezing. In view of the fact that it is possible to eliminate the need for electric power, and that the structure of the propulsion device is simplified because no catalyst is used, the performance is sufficiently useful. FIG. 3 shows the composition of the exhaust jet when dimethyl ether is used as a propellant.

Industrial use

  The electrothermal propulsion device of the present invention uses a low-toxic organic compound as a propellant and does not require a catalyst or a propellant pressurizing gas, so that both production cost and reliability are improved. Therefore, it is suitable for a propulsion device for a space vehicle, and particularly suitable for a propulsion device used for changing or maintaining an orbit of an artificial satellite, attitude control, or the like.

  1 is a diagram showing an outline of the structure of an electrothermal propulsion device used in an operation test of Example 1. FIG.   It is a figure which shows the propulsion device performance obtained from the analysis of Example 2. FIG.   It is a figure which shows the composition of an exhaust jet when the propellant obtained from the analysis of Example 2 is dimethyl ether.

Explanation of symbols

1 Cathode 2 Anode 3 Discharge Power Supply 4 Nozzle 5 Propellant Tank 6 Propellant Supply Port 7 Swirling Feather

Claims (2)

A propellant using any one or a mixture of two or more selected from ethers, natural gas and petroleum gas having a vapor pressure of 1 atm or more at room temperature stored in the tank is propelled from the storage tank. After the propellant itself is supplied to the propulsion machine by the vapor pressure of the propellant itself by opening the valve connected to the machine, the propellant that has obtained thermal energy is given thermal energy by arc discharge or electric heater in the propulsion machine. An electrothermal propulsion device that obtains a propulsive force by being accelerated by gas dynamics through a nozzle.   2. The electrothermal propulsion device according to claim 1, wherein dimethyl ether is used as a propellant.

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