Preparation method of solid propellant containing alkali metal
By adding sodium nitrate, an alkali metal additive, to solid propellants, along with plasticizers and curing agents, the problem of traditional propellants being insensitive to microwave plasma response has been solved, achieving more efficient thrust control and improved safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-24
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional aluminum-containing solid propellants are not sensitive enough to the effects of microwave plasma, and cannot respond efficiently and quickly, resulting in insignificant burning rate control and affecting the thrust regulation effect of solid rocket engines.
By adding sodium nitrate, an alkali metal additive, to a solid propellant, along with plasticizers, curing agents, and other additives, and through homogenization treatment, a propellant with a faster and more efficient response to microwave energy can be prepared.
This improves the response speed of solid propellants to microwave energy, enhances the safety and maneuverability of solid rocket engines under complex flight conditions, and reduces costs.
Smart Images
Figure CN121850818A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid rocket engine propellant preparation technology, specifically to a method for preparing an alkali metal-containing solid propellant. Background Technology
[0002] Solid propellant is an energetic composite material with specific properties that powers solid rocket engines and plays a crucial role in the development of missiles and aerospace technology. With the advancement of aerospace technology, thrust control of solid rocket engines has gradually become a research hotspot. Currently, based on their working principles, thrust adjustment of solid rocket engines mainly involves two methods: one is to change the nozzle throat area through structural modifications, and the other is to control the combustion process of the solid propellant in the combustion chamber. However, structural modifications face severe ablation problems, making it difficult to maintain the propellant profile and limiting their applicability. Therefore, the focus of thrust control research has gradually shifted to controlling the solid propellant combustion process.
[0003] Recent studies have shown that collisions between high-energy electrons and neutral molecules in plasma can cause the dissociation, excitation, and even ionization of reactive molecules, generating a large number of active atoms and groups. This, in turn, affects the chemical equilibrium of the combustion system and accelerates the chemical kinetics of combustion. However, traditional aluminum-containing solid propellants are not sensitive enough to the effects of microwave plasma and cannot produce an efficient and rapid response to microwave energy, resulting in insignificant combustion rate control. Summary of the Invention
[0004] To overcome the shortcomings of the existing technology, this invention provides a method for preparing alkali metal-containing solid propellants. This method involves adding sodium nitrate, an alkali metal additive, to the solid propellant to act as a microwave plasma energy deposition site. Plasticizers and curing agents are added to improve the propellant's processing performance. Various combinations are added sequentially and thoroughly stirred to ensure the uniformity of the components in the solid propellant. This method allows for the preparation of solid propellants with faster and more efficient microwave energy response at a lower cost, which is of great significance for the safety and maneuverability of solid rocket engines under complex flight conditions.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for preparing an alkali metal solid propellant includes the following steps;
[0007] Step 1: Mix and stir the adhesive, aluminum powder, ammonium perchlorate, alkali metal salt powder, tris(2-methyl-1-aziridine)phosphine oxide and polymerizer to obtain a slurry;
[0008] Step 2: The slurry is poured under negative pressure to obtain a medicine column;
[0009] Step 3: Dry, solidify, and demold the propellant grain to obtain an alkali metal solid propellant.
[0010] In step 1, the adhesive is hydroxyl-terminated polybutadiene. Using this substance as an adhesive provides excellent mechanical properties, resistance to acids and alkalis, resistance to hydrolysis, and wear resistance, thus providing a good matrix for the propellant.
[0011] In step 1, the alkali metal salt is sodium nitrate, sodium sulfate, or lithium carbonate.
[0012] In step 1, the polymerizing agent is toluene diisocyanate. Toluene diisocyanate has low toxicity and can improve the mechanical properties of the propellant, enhance its elasticity, and extend its lifespan.
[0013] Step 1 also includes a plasticizer.
[0014] The plasticizer is dioctyl sebacate. Using this substance as a plasticizer, dioctyl sebacate has low volatility and improves the propellant's cold resistance and insulation ability.
[0015] In step 1, aluminum powder serves as fuel, providing energy. Perchloric acid acts as an oxidant, supporting combustion. The role of phosphorus trioxide (MAPO) is to act as a crosslinking and curing agent, enhancing the propellant's elastic properties and ballistic performance.
[0016] The ammonium perchlorate is a graded material, composed of coarse and fine ammonium perchlorate. The coarse ammonium perchlorate has a particle size of 200±20 micrometers, and the fine ammonium perchlorate has a particle size of 70±5 micrometers. The alkali metal salt powder also has a particle size of 70±5 micrometers. The purpose of gradation is to create sub-pocket structures within the propellant's pocket structure, which facilitates complete combustion of the propellant.
[0017] In step 1,
[0018] According to the mass ratio, the following components are used: graded ammonium perchlorate as oxidant with a content of 52.5%–66%, metallic aluminum powder with a content of 16%, sodium nitrate with a content of 0–13.5%, hydroxyl-terminated polybutadiene with a content of 14.8%, dioctyl sebacate with a content of 1.1%, tris(2-methyl-1-aziridine)phosphine oxide with a content of 1.1%, and toluene diisocyanate with a content of 1%; when the perchloric acid content is 66%, the sodium nitrate content is 0%.
[0019] Step 1 specifically involves:
[0020] Weigh the corresponding materials according to the above proportions based on the required mass of solid propellant to be produced, and weigh an additional 10% of each material for later use.
[0021] The obtained ammonium perchlorate (AP) and sodium nitrate (NaNO3) were ground separately to obtain coarse ammonium perchlorate, fine ammonium perchlorate and sodium nitrate powder;
[0022] The aluminum powder, hydroxyl-terminated polybutadiene, and the three grinding materials obtained above were placed separately in a drying oven at 40-80 degrees Celsius and dried for 20-48 hours to obtain dried materials.
[0023] According to the mass ratio, crude ammonium perchlorate accounts for 40.5% to 50% of the total content, fine ammonium perchlorate accounts for 12% to 16% of the total content, and the remainder is sodium nitrate.
[0024] Step 2 specifically involves:
[0025] Place the mixing bowl on a balance and tare it. Then pour the preheated hydroxyl-terminated polybutadiene into the mixing bowl according to the formula ratio. Next, place the mixing bowl on a heating plate and stir thoroughly. The heating temperature is 40-70 degrees Celsius.
[0026] Repeat the above steps, adding the dried aluminum powder, coarse ammonium perchlorate, fine ammonium perchlorate, and sodium nitrate powder in sequence, stirring thoroughly after each addition;
[0027] Repeat the above steps while adding dioctyl sebacate, tris(2-methyl-1-aziridine)phosphine oxide, and toluene diisocyanate, and stir until a liquid propellant slurry containing alkali metal with good leveling properties is obtained. The slurry has no obvious particle feel inside and can form a smooth surface within 20-50 seconds after stirring is stopped.
[0028] Select the required propellant grain mold according to the needs, place the mold in the negative pressure casting equipment, and then cast the liquid propellant slurry under negative pressure. The negative pressure casting pressure is 0.1 atmospheres to 0.3 atmospheres.
[0029] Step 3 specifically involves:
[0030] Remove the propellant grain mold from the negative pressure casting equipment in step 2 and place it in a drying oven at 55-70 degrees Celsius for 72-148 hours to dry and cure. After the solid propellant is completely cured, demold it to obtain alkali metal solid propellant.
[0031] An alkali metal-containing solid propellant, by adding sodium nitrate, an alkali metal additive, to the solid propellant, allows the alkali metal to enter the pocket structure composed of fine AP (Grade I AP), making the pocket structure more complex and providing a focal point for microwave energy deposition, thereby improving the propellant's response speed to microwave energy.
[0032] An alkali metal-containing solid propellant, wherein the solid propellant contains an alkali metal.
[0033] The solid propellant has the following components:
[0034] According to the mass ratio, the following components are used: graded ammonium perchlorate as oxidant with a content of 52.5%–66%, metallic aluminum powder with a content of 16%, sodium nitrate with a content of 0–13.5%, hydroxyl-terminated polybutadiene with a content of 14.8%, dioctyl sebacate with a content of 1.1%, tris(2-methyl-1-aziridine)phosphine oxide with a content of 1.1%, and toluene diisocyanate with a content of 1%.
[0035] The beneficial effects of this invention are:
[0036] This invention proposes a method for preparing alkali metal-containing solid propellants. By adding sodium nitrate, an alkali metal additive, to the solid propellant to serve as a microwave plasma energy deposition site, and by adding plasticizers and curing agents to improve the propellant's processing performance, various combinations are added sequentially and thoroughly stirred to ensure the homogeneity of the components in the solid propellant. This method allows for the preparation of solid propellants with faster and more efficient microwave energy response at a lower cost, which is of great significance for the safety and maneuverability of solid rocket engines under complex flight conditions.
[0037] In plasma combustion enhancement mechanisms, thermal effects are generated to increase the temperature of the reaction zone; ionization is induced to produce a large number of active free radicals; and external force fields, such as gradients, Coulomb forces, and Lorentz forces, are applied to enhance the transport process.
[0038] Although the composite solid propellant doped with a certain amount of alkali metal in this invention reduces the energy level of the solid propellant itself to some extent, the presence of alkali metal salt provides sites for microwave energy deposition, thus enabling it to respond more effectively to microwave energy feed-in. Attached Figure Description
[0039] Figure 1 This is a flowchart of the preparation process for alkali metal solid propellants.
[0040] Figure 2 These are microscopic images of four types of finished propellants after being sliced.
[0041] Figure 3 This is a schematic diagram of the elemental distribution on the cross-section of four propellant samples obtained using EDS. Detailed Implementation
[0042] The present invention will now be described in further detail with reference to the accompanying drawings.
[0043] A method for preparing an alkali metal solid propellant, the specific process of which is as follows:
[0044] like Figure 1 As shown: Example 1:
[0045] The first step is to pre-treat the raw materials by grinding and drying.
[0046] The mixture uses graded ammonium perchlorate as an oxidant (52.5%), aluminum powder as fuel (16%), sodium nitrate as an alkali metal additive (13.5%), hydroxyl-terminated polybutadiene as an adhesive matrix (14.8%), dioctyl sebacate as a plasticizer (1.1%), tris(2-methyl-1-aziridine)phosphine oxide as a curing agent (1.1%), and toluene diisocyanate as a polymer additive (1%).
[0047] Because the ammonium perchlorate and sodium nitrate required for this formulation have small particle sizes, they need to be ground first, and then the moisture in each raw material is removed by drying to ensure the quality of the solid propellant after molding.
[0048] Specific steps
[0049] (1) Weigh the corresponding materials according to the above proportions based on the required mass of solid propellant, and weigh an additional 10% of each material for later use.
[0050] (2) The obtained ammonium perchlorate AP and sodium nitrate NaNO3 were ground separately to obtain crude ammonium perchlorate accounting for 40.5% of the total content by mass, and fine ammonium perchlorate and sodium nitrate powder accounting for 12% of the total content by mass.
[0051] The coarse perchloric acid particles were approximately 200 micrometers in diameter, the fine perchloric acid particles were approximately 70 micrometers in diameter, and the sodium nitrate particles were approximately 70 micrometers in diameter.
[0052] (3) Place the aluminum powder, hydroxyl-terminated polybutadiene and the three grinding materials obtained above together in a drying oven at 70 degrees and dry for 24 hours to obtain the dried material.
[0053] The second step is the preparation of alkali metal liquid propellant slurry;
[0054] To ensure the uniformity of the components in the solid propellant, various materials must be added sequentially during the preparation of the alkali metal liquid propellant slurry, and the mixture must be thoroughly stirred according to the characteristics of different components to ensure that the resulting slurry has very good leveling properties.
[0055] Specific steps
[0056] (1) Place the mixing vessel on the balance and tare it. Then pour the preheated hydroxyl-terminated polybutadiene into the mixing vessel according to the formula ratio. Next, place the mixing vessel on the heating plate and stir thoroughly.
[0057] (2) Repeat the above steps to add the dried aluminum powder, coarse ammonium perchlorate, fine ammonium perchlorate and sodium nitrate powder in sequence. Each time the material is added, it must be stirred thoroughly.
[0058] (3) Repeat the above steps while adding dioctyl sebacate, tris(2-methyl-1-aziridine)phosphine oxide and toluene diisocyanate, and stir until a liquid propellant slurry containing alkali metal with good leveling properties is obtained.
[0059] The third step is the preparation of alkali metal liquid propellant grains;
[0060] Select the required propellant grain mold according to the needs, place the mold in the negative pressure casting equipment, and then cast the liquid propellant slurry obtained in the second step under negative pressure to obtain alkali metal liquid propellant grains.
[0061] Step 4: Preparation of alkali metal solid propellant grains;
[0062] Remove the propellant grain mold from the negative pressure casting equipment in the third step and place it in a drying oven at 70 degrees Celsius for 72 hours to dry and cure. After the solid propellant is completely cured, demold it to obtain alkali metal solid propellant grains.
[0063] Example 2:
[0064] Example 1:
[0065] The first step is to pre-treat the raw materials by grinding and drying.
[0066] The mixture comprises graded ammonium perchlorate as an oxidant (56%), aluminum powder as fuel (16%), sodium nitrate as an alkali metal additive (10%), hydroxyl-terminated polybutadiene as a binder matrix (14.8%), dioctyl sebacate as a plasticizer (1.1%), tris(2-methyl-1-aziridine)phosphine oxide as a curing agent (1.1%), and toluene diisocyanate as a polymer additive (1%).
[0067] Because the ammonium perchlorate and sodium nitrate required for this formulation have small particle sizes, they need to be ground first, and then the moisture in each raw material is removed by drying to ensure the quality of the solid propellant after molding.
[0068] Specific steps
[0069] (1) Weigh the corresponding materials according to the above proportions based on the required mass of solid propellant, and weigh an additional 10% of each material for later use.
[0070] (2) The obtained ammonium perchlorate AP and sodium nitrate NaNO3 were ground separately to obtain crude ammonium perchlorate accounting for 40.5% of the total content by mass, and fine ammonium perchlorate and sodium nitrate powder accounting for 12% of the total content by mass.
[0071] The coarse perchloric acid particles were approximately 200 micrometers in diameter, the fine perchloric acid particles were approximately 70 micrometers in diameter, and the sodium nitrate particles were approximately 70 micrometers in diameter.
[0072] (3) Place the aluminum powder, hydroxyl-terminated polybutadiene and the three grinding materials obtained above together in a drying oven at 70 degrees and dry for 24 hours to obtain the dried material.
[0073] The second step is the preparation of alkali metal liquid propellant slurry;
[0074] To ensure the uniformity of the components in the solid propellant, various materials must be added sequentially during the preparation of the alkali metal liquid propellant slurry, and the mixture must be thoroughly stirred according to the characteristics of different components to ensure that the resulting slurry has very good leveling properties.
[0075] Specific steps
[0076] (1) Place the mixing vessel on the balance and tare it. Then pour the preheated hydroxyl-terminated polybutadiene into the mixing vessel according to the formula ratio. Next, place the mixing vessel on the heating plate and stir thoroughly.
[0077] (2) Repeat the above steps to add the dried aluminum powder, coarse ammonium perchlorate, fine ammonium perchlorate and sodium nitrate powder in sequence. Each time the material is added, it must be stirred thoroughly.
[0078] (3) Repeat the above steps while adding dioctyl sebacate, tris(2-methyl-1-aziridine)phosphine oxide and toluene diisocyanate, and stir until a liquid propellant slurry containing alkali metal with good leveling properties is obtained.
[0079] The third step is the preparation of alkali metal liquid propellant grains;
[0080] Select the required propellant grain mold according to the needs, place the mold in the negative pressure casting equipment, and then cast the liquid propellant slurry obtained in the second step under negative pressure to obtain alkali metal liquid propellant grains.
[0081] Step 4: Preparation of alkali metal solid propellant grains;
[0082] Remove the propellant grain mold from the negative pressure casting equipment in the third step and place it in a drying oven at 70 degrees Celsius for 120 hours to dry and cure. After the solid propellant is completely cured, demold it to obtain alkali metal solid propellant grains.
[0083] like Figure 2The image shows the microstructure images of four types of finished propellant sections. These are: PF1: a basic propellant formulation without alkali metal addition; PF2: a propellant sample with 3.5% alkali metal addition; PF3: a propellant sample with 6% alkali metal addition; and PF2-AE: a sample obtained by soaking PF2 propellant in anhydrous ethanol to remove perchloric acid. Scanning electron microscopy and energy dispersive spectroscopy revealed that the vast majority of the added alkali metal fell into pocket structures composed of fine AP (Grade I AP) (P1, P2, and P3 in the image below), making the pocket structure more complex and providing a focal point for microwave energy deposition, thereby improving the propellant's response speed to microwave energy.
[0084] like Figure 3 As shown, elemental distributions on cross-sections of four propellant samples were obtained using EDS to more clearly depict the aforementioned bag-like structure. The green, orange, red, yellow, and blue areas in the figure represent the distributions of elements C, Al, O, Cl, and Na, respectively. In the figure, C, Cl, Al, and Na represent the propellant composition: HTPB(HO–[CH2CH=CHCH2]) n -OH), AP(NH4ClO2), aluminum powder and alkali metal additive NaNO3.
[0085] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A method for preparing an alkali metal solid propellant, characterized in that, Includes the following steps; Step 1: Mix and stir the adhesive, aluminum powder, ammonium perchlorate, alkali metal salt powder, tris(2-methyl-1-aziridine)phosphine oxide and polymerizer to obtain a slurry; Step 2: The slurry is poured under negative pressure to obtain a medicine column; Step 3: Dry, solidify, and demold the propellant grain to obtain an alkali metal solid propellant.
2. The method for preparing an alkali metal solid propellant according to claim 1, characterized in that, In step 1, the adhesive is hydroxyl-terminated polybutadiene; In step 1, the alkali metal salt is sodium nitrate; In step 1, the polymerizing agent is toluene diisocyanate; Step 1 also includes a plasticizer; The plasticizer is dioctyl sebacate.
3. The method for preparing an alkali metal solid propellant according to claim 2, characterized in that, The ammonium perchlorate is a graded material composed of crude ammonium perchlorate and fine ammonium perchlorate. The crude ammonium perchlorate has a particle size of 200±20 micrometers, and the fine ammonium perchlorate has a particle size of 70±5 micrometers. The alkali metal salt powder has a particle size of 70±5 micrometers.
4. The method for preparing an alkali metal solid propellant according to claim 1, characterized in that, In step 1, According to the mass ratio, the following components are used: graded ammonium perchlorate as oxidant with a content of 52.5%–66%, metallic aluminum powder with a content of 16%, sodium nitrate with a content of 0–13.5%, hydroxyl-terminated polybutadiene with a content of 14.8%, dioctyl sebacate with a content of 1.1%, tris(2-methyl-1-aziridine)phosphine oxide with a content of 1.1%, and toluene diisocyanate with a content of 1%.
5. The method for preparing an alkali metal solid propellant according to claim 4, characterized in that, Step 1 specifically involves: Weigh the corresponding materials according to the above proportions based on the required mass of solid propellant to be produced, and weigh an additional 10% of each material for later use. The obtained ammonium perchlorate (AP) and sodium nitrate (NaNO3) were ground separately to obtain coarse ammonium perchlorate, fine ammonium perchlorate and sodium nitrate powder; The aluminum powder, hydroxyl-terminated polybutadiene, and the three grinding materials obtained above were placed separately in a drying oven at 40-80 degrees Celsius and dried for 20-48 hours to obtain dried materials. According to the mass ratio, crude ammonium perchlorate accounts for 40.5% to 50% of the total content, fine ammonium perchlorate accounts for 12% to 16% of the total content, and the remainder is sodium nitrate.
6. The method for preparing an alkali metal solid propellant according to claim 5, characterized in that, Step 2 specifically involves: Place the mixing bowl on a balance and tare it. Then pour the preheated hydroxyl-terminated polybutadiene into the mixing bowl according to the formula ratio. Next, place the mixing bowl on a heating plate and stir thoroughly. The heating temperature is 40-70 degrees Celsius. Repeat the above steps, adding the dried aluminum powder, coarse ammonium perchlorate, fine ammonium perchlorate, and sodium nitrate powder in sequence, stirring thoroughly after each addition; Repeat the above steps while adding dioctyl sebacate, tris(2-methyl-1-aziridine)phosphine oxide, and toluene diisocyanate, and stir until a liquid propellant slurry containing alkali metal with good leveling properties is obtained. The slurry has no obvious particle feel inside and can form a smooth surface within 20-50 seconds after stirring is stopped. Select the required propellant grain mold according to the needs, place the mold in the negative pressure casting equipment, and then cast the liquid propellant slurry under negative pressure. The negative pressure casting pressure is 0.1 atmospheres to 0.3 atmospheres.
7. The method for preparing an alkali metal solid propellant according to claim 6, characterized in that, Step 3 specifically involves: Remove the propellant grain mold from the negative pressure casting equipment in step 2 and place it in a drying oven at 55-70 degrees Celsius for 72-148 hours to dry and cure. After the solid propellant is completely cured, demold it to obtain alkali metal solid propellant.
8. An alkali metal solid propellant prepared by the method according to any one of claims 1-7, characterized in that, By adding sodium nitrate, an alkali metal additive, to the solid propellant, the alkali metal enters the pocket structure composed of fine AP (Grade I AP), making the pocket structure more complex and providing a focal point for microwave energy deposition, thereby improving the propellant's response speed to microwave energy.
9. The alkali metal solid propellant according to claim 8, characterized in that, Solid propellants contain alkali metals.
10. The alkali metal solid propellant according to claim 8, characterized in that, The solid propellant has the following components: According to the mass ratio, the following components are used: graded ammonium perchlorate as oxidant with a content of 52.5%–66%, metallic aluminum powder with a content of 16%, sodium nitrate with a content of 0–13.5%, hydroxyl-terminated polybutadiene with a content of 14.8%, dioctyl sebacate with a content of 1.1%, tris(2-methyl-1-aziridine)phosphine oxide with a content of 1.1%, and toluene diisocyanate with a content of 1%.