Non-burning solid propellant and method of making and propulsion system

Abstract

A non-combustible solid propellant, a preparation method thereof and a propulsion system, the solid propellant rapidly reacts under the action of an initiator to generate carbon dioxide gas at normal temperature and high pressure as a working substance, and a preparation method of the solid propellant, and a jet propulsion system comprising the solid propellant. The solid propellant has the characteristics of no open flame, no high-temperature heat source, low noise, green environmental protection, simple structure, low cost and high safety, and has application value in many fields such as military, scientific research monitoring and model aircraft. The solid propellant is composed of a solid mixture of anhydrous citric acid (C6H8O7) and sodium bicarbonate (NaHCO3), and the two components are dried and uniformly mixed; the propellant is stable at normal temperature and does not react naturally, and when water is used as an initiator, a double decomposition reaction occurs to generate carbon dioxide gas as a working substance.

Description

[0001] This invention belongs to the field of propulsion technology, specifically relating to a propellant that uses a solid propellant to rapidly react under the action of an initiator to generate room-temperature, high-pressure carbon dioxide gas as the working substance, its preparation method, and a jet propulsion system containing the propellant. Background Technology

[0002] Traditional propulsion systems for vehicles such as torpedoes, aircraft, and ship models primarily rely on the high-temperature, high-pressure gas generated by fuel combustion, which expands through a nozzle to produce thrust. These technologies typically generate significant mechanical noise and substantial heat emissions.

[0003] In military applications or specific sensitive detection scenarios, the above-mentioned propulsion method has obvious drawbacks: the thermal radiation generated by combustion is easily detected and tracked by enemy infrared reconnaissance systems; at the same time, the acoustic signals generated by the mechanical moving parts and the combustion process itself are also easily captured by sonar and other equipment, thereby exposing the vehicle's position and reducing its stealth performance and survivability.

[0004] Furthermore, in youth science and technology innovation education, model competitions, or specific civilian applications (such as underwater photography and environmental monitoring), traditional small-scale powered models often use electric motors or combustion engines. Electric motor drives suffer from problems such as short battery life and noise; combustion engines pose safety hazards such as the risk of burns from high temperatures, exhaust pollution, and complex operation, and are difficult to meet the environmental protection requirements of "carbon peaking and carbon neutrality".

[0005] Existing technologies include propulsion methods based on the phase change of liquid carbon dioxide, which generate thrust by heating liquid carbon dioxide to cause it to vaporize instantaneously. Although this method is a physical process without combustion, it requires a precise insulated container and an instantaneous heating module, resulting in a complex system structure, high cost, and stringent requirements for sealing and temperature control. It is not suitable for low-cost, disposable, or simple model applications.

[0006] Other electrically controlled solid propellant technologies control the combustion reaction of energetic materials through voltage, but they are still essentially combustion processes, producing flames and high-temperature products. Furthermore, their formulations often include oxidizers such as perchlorates and nitrates, and the reaction products may pollute the environment. While simulated solid propellant technology possesses non-flammable properties, it is primarily used for performance simulation testing in non-combat environments and does not involve actual thrust generation mechanisms.

[0007] Therefore, developing a new type of propellant and its propulsion system that is flameless, heat-free, low-noise, environmentally friendly, simple in structure, low in cost, and highly safe has significant practical implications and application value. Summary of the Invention Technical issues

[0008] This invention aims to solve the following technical problems existing in the current propulsion technology: 1. Traditional combustible propellants generate high-temperature heat sources and open flames, making them easily detectable by infrared sensors and resulting in poor stealth performance; 2. Traditional propulsion processes are accompanied by loud mechanical and combustion noise, which are easily detected acoustically; 3. Combustion products often contain toxic and harmful substances or greenhouse gases, causing serious environmental pollution; 4. Existing carbon dioxide propulsion systems based on physical phase change are complex in structure and expensive, making them unsuitable for simple models or single-use scenarios; 5. The dynamic models commonly used in youth science and technology innovation activities have problems such as safety hazards, short battery life, or poor environmental performance. Solution

[0009] To achieve the above objectives, the present invention provides the following technical solutions: Technical Solution 1: A non-combustible solid propellant The solid propellant is characterized by being composed of a solid mixture of anhydrous citric acid (C6H8O7) and sodium bicarbonate (NaHCO3), both of which are dried and mixed uniformly. The propellant is stable at room temperature and does not react spontaneously. When it comes into contact with water as an initiator, it undergoes a metathesis reaction to generate carbon dioxide gas as the working substance.

[0010] Furthermore, the molar ratio of the anhydrous citric acid to sodium bicarbonate is 1:2, and the mass ratio is calculated according to the reaction equation C6H8O7 + 2NaHCO3 → C6H5O7Na2 + 2CO2↑ + 2H2O.

[0011] Furthermore, the anhydrous citric acid and sodium bicarbonate are dried to constant weight in an oven at 60-80°C for at least 2 hours to ensure the removal of water of crystallization and to prevent slow reaction during storage.

[0012] Furthermore, the solid propellant is packaged in sealed, moisture-proof packaging, each portion weighing 9 grams, containing approximately 4.8 grams of anhydrous citric acid and approximately 4.2 grams of sodium bicarbonate. This ratio is calculated based on the ideal gas equation and can produce approximately 0.05 mol of carbon dioxide gas in a 300 ml reaction vessel at a safe operating pressure of 0.4 MPa.

[0013] Technical Solution 2: A jet propulsion system comprising the solid propellant described in claim 1 Its features include: At least one reaction vessel for containing the solid propellant; An initiator container or injection mechanism for containing and metering water as an initiator; The jet pipe, connected to the outlet of the reaction vessel, is used to guide the injection of carbon dioxide gas to generate recoil force; An automatic separation device is used to automatically discard the reaction vessel after the working material in the reaction vessel has been used up, based on the pressure difference.

[0014] Furthermore, the jet pipe adopts a Laval jet pipe structure, which accelerates the expansion of carbon dioxide gas under subsonic conditions and converts the bubble bursting force into secondary thrust.

[0015] Furthermore, the system includes multiple reaction vessels arranged in series or parallel, and is equipped with an automatic start-up device to achieve multi-stage propulsion.

[0016] Furthermore, the system also includes a barometer for monitoring the pressure inside the reaction vessel; when the pressure reaches a preset safety value (e.g., 0.4 MPa), the vehicle is released to obtain the optimal initial velocity.

[0017] Technical Solution 3: A propulsion method based on the solid propellant described in claim 1 Its characteristic is that it includes the following steps: 1. Dry anhydrous citric acid and sodium bicarbonate are mixed evenly at a molar ratio of 1:2 to prepare a solid propellant; 2. Load the solid propellant into the reaction vessel and seal it for storage; 3. When thrust is required, water is injected into the reaction vessel as an initiator; 4. Citric acid reacts rapidly with sodium bicarbonate in water to produce carbon dioxide gas at room temperature; 5. High-pressure carbon dioxide gas is injected directionally through the jet pipeline, generating recoil thrust; 6. After the gas pressure inside the reaction vessel decreases, the empty vessel is discarded by an automatic separation device to reduce the load. Beneficial effects

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. No heat source, high stealth capability The propellant of this invention produces carbon dioxide gas through an acid-base neutralization reaction. The reaction process takes place at room temperature, without combustion, open flame, or high-temperature heat source generation. The temperature of the produced gas is essentially the same as the ambient temperature, and it has no infrared radiation characteristics, effectively evading infrared detection and tracking.

[0019] 2. Low noise characteristics The reaction process involves no explosive combustion, resulting in relatively stable gas production. The jetting process can be optimized using Laval jet nozzles to reduce turbulence noise. Overall mechanical noise is significantly lower than that of traditional combustible propellants, which is beneficial for acoustic stealth.

[0020] 3. Green and environmentally friendly The reactants, citric acid and sodium bicarbonate, are common, food-grade substances that are non-toxic and harmless. The reaction products are sodium citrate, water, and carbon dioxide. Carbon dioxide emissions can be precisely controlled by the propellant dosage and originate from the reaction itself, not from the combustion of fossil fuels, aligning with the environmentally friendly principles of "carbon peaking and carbon neutrality." In contrast, traditional propellants often contain perchlorates, nitrates, etc., and their reaction products are environmentally unfriendly.

[0021] 4. High security The propellant is stable at room temperature in a dry state, does not react spontaneously, and has high safety during storage and transportation; The maximum charge amount can be accurately calculated using the ideal gas equation to ensure that the pressure inside the reaction vessel does not exceed the safety threshold. Install partial pressure gas storage tanks or multi-stage reaction vessels to avoid excessively high gas pressure in a single vessel. The air pressure detector is set up for real-time monitoring, and the vehicle can be released before overpressure occurs; All propellant raw materials are food-grade, posing a low risk of accidental contact or ingestion, making them particularly suitable for science and technology education activities for teenagers.

[0022] 5. Simple structure and low cost The propellant raw materials of this invention are readily available and inexpensive; the reaction vessel can be a low-cost container such as a commercially available beverage bottle; there is no need for complex heating modules, insulation systems or high-pressure gas storage tanks, the overall system structure is simple, and it is suitable for single-use or low-cost models.

[0023] 6. Multi-stage propulsion and high energy efficiency By using an automatic separation device to promptly discard containers that have completed the reaction, the ineffective load is reduced and the energy utilization rate is improved. Laval jet nozzles convert the energy of gas expansion and bubble bursting into secondary thrust. The curved surface design of the hull utilizes the dynamic pressure effect to reduce sailing resistance and further improve energy efficiency.

[0024] 7. Suitable for multiple scenarios This invention is not only applicable to science and technology innovation education activities for teenagers, but can also be extended to underwater exploration equipment, small unmanned vehicles, model rockets and other scenarios with special requirements for stealth and environmental protection. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the solid propellant reaction principle of the present invention; Figure 2 This is a schematic diagram of the propulsion system structure of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of the multi-stage automatic separation device of the present invention. Figure 4This is a schematic diagram of the Laval jet pipe structure of the present invention; Figure 5 This is an external view of an application example of the propulsion system of the present invention on a pneumatic ship. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, but this should not be construed as limiting the present invention. Various modifications and improvements can be made to the present invention by those skilled in the art without departing from the spirit and essence of the invention.

[0027] Example 1: Preparation of solid propellants Step 1: Drying the raw materials Weigh 500g of anhydrous citric acid (analytical grade, content ≥99.5%), spread it evenly in an enamel dish, place it in a 70℃ constant temperature oven, dry for 3 hours, and immediately place it in a desiccator to cool to room temperature.

[0028] Weigh 500 grams of sodium bicarbonate (analytical grade, content ≥99.5%), dry it in a constant temperature oven at 70℃ for 3 hours, and then place it in a desiccator to cool to room temperature.

[0029] The purpose of drying is to remove any adsorbed moisture and prevent slow reactions during storage.

[0030] Step 2: Calculation of proportions Calculate based on the reaction C6H8O7 + 2NaHCO3 → C6H5O7Na2 + 2CO2↑ + 2H2O: Molecular weight of citric acid: 192.14; Molecular weight of 2 molecules of sodium bicarbonate: 2 × 84.01 = 168.02.

[0031] Mass ratio: Citric acid: Sodium bicarbonate = 192.14 : 168.02 ≈ 1.144 : 1, that is, every 1 gram of sodium bicarbonate requires about 1.144 grams of citric acid.

[0032] In this embodiment, 4.8 grams of citric acid and 4.2 grams of sodium bicarbonate were used, with a mass ratio of approximately 1.143:1, which conforms to the theoretical ratio.

[0033] Step 3: Mixing and Packaging Weigh the dried citric acid and sodium bicarbonate according to the above ratio, place them in a ball mill jar and mix for 30 minutes to ensure the material is fully homogeneous.

[0034] The mixed solid propellant was dispensed into 9.0-gram portions (approximately 4.8 grams of citric acid + approximately 4.2 grams of sodium bicarbonate) into sealed aluminum foil bags, desiccant was added, the bags were heat-sealed, and the production date and batch number were labeled.

[0035] Step 4: Quality Inspection Randomly selected samples were tested for moisture content (Karl Fischer method), and the moisture content was required to be <0.5%; Conduct a reactivity test: Take one part of propellant (9.0 g) and place it in a 300 ml reaction flask, add 50 ml of water, and measure the maximum pressure and reaction completion time. The pressure should be above 0.4 MPa and the reaction time should be < 30 seconds.

[0036] Example 2: Safety Calculation of Maximum Charge This embodiment details the calculation method for matching propellant charge with the safety of the reaction vessel.

[0037] Reaction vessel: 300ml Pepsi plastic bottle, with a measured ultimate compressive strength of 1.0-1.5MPa and a set safe operating pressure of 0.4MPa.

[0038] Ambient temperature: 10℃ (283K), a common daytime temperature in Guangdong Province during winter.

[0039] According to the ideal gas law: PV = nRT P = 0.4 × 10 6 Pa V = 3.0 × 10⁻ 4 m³ (300ml) R = 8.314 J / (mol·K) T = 283 K The calculation yields: n = (0.4 × 10 6 × 3.0×10⁻ 4 ) / (8.314 × 283) = 120 / 2353.86 ≈0.051 mol According to the reaction equation, 1 mol of citric acid and 2 mol of sodium bicarbonate are required to produce 2 mol of CO2.

[0040] Therefore, to produce 0.051 mol of CO2, the following is required: Citric acid: 0.051 / 2 = 0.0255 mol × 192.14 g / mol = 4.90 g Sodium bicarbonate: 0.051 mol × 84.01 g / mol = 4.28 g Considering the following factors, the amount of explosives can be appropriately increased: 1. Some CO2 dissolves in the water produced in the reaction, forming a saturated solution, and does not participate in the generation of gas pressure; 2. It begins to release gas for navigation when the air pressure reaches 0.4 MPa, without needing to generate all the gas; 3. The reaction process is not instantaneous; it is released while reacting, and the actual peak pressure may be lower than the theoretical calculation value.

[0041] After comprehensive consideration, the amount of propellant in each sample was determined to be 4.8 grams of citric acid and 4.2 grams of sodium bicarbonate, for a total of 9.0 grams.

[0042] Example 3: Assembly and Application of Jet Propulsion Systems This embodiment uses the "Silk Road Sail" carbon dioxide jet-powered ship as an example to illustrate the specific application of the propulsion system of the present invention.

[0043] 1. Hull production Take a piece of foam plastic (400mm×100mm×100mm), cut and polish it according to the streamlined hull shape, and design the bottom as a slightly curved surface to reduce sailing resistance by utilizing the dynamic pressure effect.

[0044] 2. Reaction system installation Use five 300ml Pepsi bottles as reaction vessels, and install custom caps on the bottle mouths. The caps integrate the following functions: One-way injection port (for injecting initiator) Gas outlet (connected to the jet pipe) barometer interface Automatic separator interface 3. Propellant loading Each reaction flask was filled with 9.0 g of solid propellant prepared according to Example 1, and the cap was tightened to seal the flask.

[0045] 4. Jet system installation The gas outlet is connected to the Laval jet nozzle via a pressure-resistant hose. Jet nozzle parameters: inlet diameter 8mm, throat diameter 4mm, outlet diameter 12mm, expansion section length 30mm, expansion angle 15°. These parameters are suitable for subsonic flow conditions, maximizing the conversion of gas kinetic energy into thrust.

[0046] 5. Multi-stage propulsion and automatic separation device Five reaction flasks are connected in series via an automatic separation device. The working principle of the automatic separation device is as follows: Figure 3 As shown: Automatic switching is achieved using pressure difference. When the pressure inside the first-stage reaction bottle is higher than that of the second stage, the one-way valve closes, and the first stage operates independently. After the gas in the first stage is exhausted, the pressure inside the bottle drops, and the pressure inside the second-stage bottle pushes the one-way valve open, starting the second stage operation. Simultaneously, the mechanical separation mechanism automatically discards the empty bottle after the pressure in the first stage returns to zero, reducing the load.

[0047] 6. Initiator addition and startup Place the assembled powerboat in the dock and inject 50ml of water (containing 0.5ml of foaming agent to increase the amount of bubbles) into the first-stage reaction bottle through the water inlet, then quickly close the water inlet.

[0048] Observe the barometer reading. When the pressure reaches 0.4 MPa, pull the starter trigger to release the hull.

[0049] As the ship sails at high speed on the water, the bubbles expelled from the jet nozzles burst at the stern, generating secondary thrust.

[0050] 7. Experimental Results Experiments showed that under calm water conditions, the power ship can reach a maximum speed of 3.5 m / s and a maximum range of about 120 meters, with no significant noise or heat radiation during the voyage.

[0051] Example 4: Reaction Kinetics and Thermodynamics Analysis This embodiment provides a theoretical analysis of the reaction principle.

[0052] Citric acid is a tribasic acid, and its three ionization constants are as follows: Ka1 = 7.4 × 10⁻ 4 Ka2 = 1.7 × 10⁻ 5 Ka3 = 4.0 × 10⁻ 7 The first-order ionization constant of carbonic acid: Ka1 = 4.5 × 10⁻ 7 Because of the Ka3 of citric acid (4.0 × 10⁻ 7 Slightly smaller than the Ka1 of carbonic acid (4.5 × 10⁻) 7 The third proton of citric acid cannot displace hydrogen in carbonic acid; therefore, citric acid behaves only as a dicarboxylic acid in this reaction, and the product is disodium hydrogen citrate (C6H5O7Na2), not trisodium citrate. This is consistent with the experimentally measured pH change and product analysis results.

[0053] Heat effect of reaction: According to the calorimeter, the reaction is a slightly endothermic reaction, ΔH ≈ +15 kJ / molCO2. Therefore, the reaction process not only does not generate heat, but also absorbs heat from the environment, further ensuring the "heat source-free" characteristic.

[0054] Comparative Example 1: Comparison with Traditional Combustion Propellants We selected KNDX propellant (potassium nitrate + sorbitol) for commercially available model rockets as a comparison.

[0055] | Comparison Items | Propellant of this Invention | KNDX Propellant | |---------|------------|------------| | Reaction Type | Acid-Base Neutralization | Oxidation-Reduction Combustion | | Reaction Temperature | Room temperature (10-30℃) | >600℃ | Infrared radiation: None | Strong | Smoke Production | None | Obvious white smoke | Noise Level | Low (<60dB) | High (>90dB) | | Product toxicity | Non-toxic | Contains nitrogen oxides | | Storage Safety | High (Safe as long as there is no fire source) | Medium (Requires protection against moisture and impact) | Raw material cost | Low (food grade) | Medium (chemical raw materials) The comparative results show that the present invention has significant advantages in terms of stealth, environmental friendliness, and safety. Industrial applicability

[0056] The non-combustible solid propellant and its propulsion system provided by this invention have outstanding advantages such as readily available raw materials, simple preparation, safe use, and environmental friendliness, and can be widely used in the following fields: 1. Science and Technology Innovation Education for Youth: As an ideal vehicle for interdisciplinary practical activities involving physics, chemistry, and engineering, it cultivates students' scientific literacy and innovative abilities, such as the "Silk Road Voyage: Chemical Power" pneumatic boat design challenge mentioned in the background information.

[0057] 2. Underwater detection equipment: Propulsion systems for small unmanned underwater vehicles (UUVs), whose low noise and heat-free characteristics are conducive to covert underwater operations.

[0058] 3. Model rockets and aircraft models: serving as power sources for teaching demonstration models or competition models, avoiding the safety hazards of combustible propellants.

[0059] 4. Environmental monitoring buoys: used for the deployment and position adjustment of marine or lake environmental monitoring buoys, which will not cause chemical pollution to the water.

[0060] 5. Power source for special occasions: Temporary power needs in situations where fire and heat sources are strictly restricted (such as dangerous environments like coal mines and oil depots).

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A non-flammable solid propellant, characterized in that, It consists of a solid mixture of anhydrous citric acid (C6H8O7) and sodium bicarbonate (NaHCO3), both of which are dried and mixed evenly. The propellant is stable at room temperature and undergoes a metathesis reaction when it comes into contact with water as an initiator, generating carbon dioxide gas as the working substance.

2. The solid propellant according to claim 1, characterized in that, The molar ratio of anhydrous citric acid to sodium bicarbonate is 1:

2. The mass ratio is calculated based on the reaction equation C6H8O7 + 2NaHCO3 → C6H5O7Na2 + 2CO2↑ + 2H2O.

3. The solid propellant according to claim 1, characterized in that, The anhydrous citric acid and sodium bicarbonate were dried to constant weight in an oven at 60-80℃ for no less than 2 hours.

4. The solid propellant according to claim 1, characterized in that, The solid propellant is packaged in sealed, moisture-proof packaging, each portion weighing 9 grams, containing 4.6-5.0 grams of anhydrous citric acid and 4.0-4.4 grams of sodium bicarbonate.

5. A jet propulsion system comprising the solid propellant according to any one of claims 1-4, characterized in that, include: o At least one reaction vessel for containing the solid propellant; o Initiator injection mechanism, used to inject water as an initiator into the reaction vessel; o Jet line, connected to the outlet of the reaction vessel, used to guide the injection of carbon dioxide gas to generate recoil force; o Automatic separation device, used to automatically discard the reaction vessel based on the pressure difference after the working material in the reaction vessel is exhausted.

6. The jet propulsion system according to claim 5, characterized in that, The jet pipeline adopts a Laval jet pipe structure, including a contraction section, a throat, and an expansion section, which is used to accelerate the expansion of carbon dioxide gas and convert the bursting force of the bubble into secondary thrust.

7. The jet propulsion system according to claim 5, characterized in that, The system includes multiple reaction vessels arranged in series or parallel, and is equipped with an automatic start-up device to achieve multi-stage propulsion; the automatic separation device is based on the pressure difference between each stage of the reaction vessel to achieve sequential start-up and empty container disposal.

8. The jet propulsion system according to claim 5, characterized in that, The system also includes a barometer for monitoring the pressure inside the reaction vessel; when the pressure reaches a preset safety value, the vehicle is released to obtain the optimal initial velocity; the preset safety value is calculated and determined based on the maximum pressure resistance of the reaction vessel and the safety factor.

9. A propulsion method based on the solid propellant according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Dry anhydrous citric acid and sodium bicarbonate are mixed evenly at a molar ratio of 1:2 to prepare a solid propellant; (2) Load the solid propellant into the reaction vessel and seal it for storage; (3) When thrust is required, water is injected into the reaction vessel as an initiator; (4) Citric acid reacts rapidly with sodium bicarbonate in water to produce carbon dioxide gas at room temperature; (5) High-pressure carbon dioxide gas is injected directionally through the jet pipeline to generate recoil thrust; (6) After the gas pressure inside the reaction vessel decreases, the empty vessel is discarded by an automatic separation device to reduce the load.

10. The propulsion method according to claim 9, characterized in that, The method also includes the step of calculating the maximum safe charge amount using the ideal gas equation: PV = nRT, where P is the safe operating pressure of the reaction vessel, V is the volume of the reaction vessel, T is the ambient temperature, and R is the gas constant. The amount of carbon dioxide n is calculated and then converted into the mass of citric acid and sodium bicarbonate according to the reaction equation.

11. A type of aircraft, characterized in that, It includes the jet propulsion system as described in any one of claims 5-8.

12. The aircraft according to claim 11, characterized in that, The vehicle is a pneumatic boat, an underwater vehicle, or a model rocket; the bottom of the vehicle is designed with a curved surface, which generates a dynamic pressure effect when traveling at high speed, reducing the draft and reducing the resistance of the water.

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