Solid rocket propellant
The use of glycidyl azide polymer and lithium fluoride in solid rocket propellants addresses the issue of alumina residue formation and reduces combustion rate, enhancing safety in space applications.
Patent Information
- Application Number
- JP2023192229
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-10
- Publication Date
- 2025-05-22
AI Technical Summary
Existing solid rocket propellants containing aluminum generate alumina lumps as combustion residues, which pose a danger in outer space, and there is a need for a propellant with a binder other than HTPB that can reduce combustion rate.
A solid rocket propellant using glycidyl azide polymer as the binder main component and lithium fluoride, where the lithium fluoride content is between 1 part by mass and 10 parts by mass per 100 parts by mass of the glycidyl azide polymer.
The propellant effectively reduces the combustion rate of solid rocket propellants, providing a safer option for space applications by minimizing alumina residue formation.
Smart Images
Figure 2025079509000001
Abstract
Description
Technical Field
[0001] The present invention relates to solid rocket propellants.
Background Art
[0002] Conventionally, solid rocket propellants contain hydroxyl-terminated poly butadiene (HTPB) of a binder rubber, ammonium perchlorate, and aluminum. When the solid rocket propellant contains aluminum, after the combustion of the solid rocket propellant, lumps of alumina are generated as combustion residues. Such lumps of alumina become debris that pollutes outer space and may collide with spacecraft, space stations, astronauts working in outer space, etc., posing a significant danger.
[0003] Therefore, a solid propellant has been proposed that includes a binder main component made of glycidyl azide polymer from which aluminum has been excluded, and an oxidizer component made of ammonium perchlorate. Aiming to expand the combustion rate range for its practical application, one of the considerations is to reduce the combustion rate. As a method for reducing the combustion rate of a solid rocket propellant, for example, a method of adding an alkali metal such as lithium fluoride to the propellant composition is known (see, for example, Non-Patent Document 1). In this method, the alkali metal melts due to the heat during the combustion of the solid rocket propellant, and the alkali metal absorbs the heat of fusion from the solid rocket propellant, thereby reducing the combustion temperature of the solid rocket propellant and lowering the combustion rate.
Prior Art Documents
Non-Patent Documents
[0004]
Non-Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, Non-Patent Document 1 only describes the effect of reducing the combustion rate by an alkali metal when using terminal hydroxyl group butadiene (HTPB) as the main component of the binder, and does not describe the effect of reducing the combustion rate by an alkali metal when using other binders.
[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a solid rocket propellant containing a binder other than terminal hydroxyl group butadiene (HTPB) and capable of reducing the combustion rate.
Means for Solving the Problems
[0007] The present invention has the following aspects. [1] A solid rocket propellant containing a binder main component composed of glycidyl azide polymer and lithium fluoride. [2] The solid rocket propellant according to [1], wherein the content of the lithium fluoride with respect to 100 parts by mass of the glycidyl azide polymer is 1 part by mass or more and 10 parts by mass or less.
Effects of the Invention
[0008] According to the present invention, it is possible to provide a solid rocket propellant containing a binder other than terminal hydroxyl group butadiene (HTPB) and capable of reducing the combustion rate.
Brief Description of the Drawings
[0009] [Figure 1] It is a figure which shows the result of the combustion experiment of a solid rocket propellant.
Embodiments for Carrying Out the Invention
[0010] Embodiments of the solid rocket propellant of the present invention will be described. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.
[0011] [Solid rocket propellant] A solid rocket propellant according to one embodiment of the present invention includes a binder base of glycidyl azide polymer and lithium fluoride (LiF).
[0012] Glycidyl azide polymer (GAP) is a type of high-energy polymer. The azide group (-N3) contained in the molecule is the source of high energy, and when the azide group decomposes, nitrogen (N 2 ) A large amount of thermal energy is generated when gas is released. Examples of the glycidyl azide polymer include tetra-ol glycidyl azide polymer (tetra-ol GAP), di-ol glycidyl azide polymer (di-ol GAP), tri-ol glycidyl azide polymer (tri-ol GAP), etc. Among these, tetra-ol GAP is preferred because it is easier to form urethane bonds three-dimensionally compared with di-ol GAP and tri-ol GAP, making a crosslinking agent unnecessary, and because it requires a smaller amount of curing agent compared with di-ol GAP and tri-ol GAP, it has excellent mechanical properties.
[0013] The binder main component contains, in addition to the glycidyl azide polymer, a curing agent for curing the glycidyl azide polymer, a curing catalyst, and a diluent.
[0014] Examples of the curing agent include hexamethylene diisocyanate, isophorone diisocyanate (IPDI), etc. Among these, hexamethylene diisocyanate is preferred from the viewpoint of safety in chemical use.
[0015] The content of the curing agent relative to 100 parts by mass of the glycidyl azide polymer is preferably 5 parts by mass to 15 parts by mass, more preferably 9 parts by mass to 12 parts by mass. If the content of the curing agent is less than the lower limit, the curing time becomes longer or the curing does not occur, whereas if the content of the curing agent exceeds the upper limit, the high reactivity when mixed with the curing catalyst leads to foaming of the elastomer.
[0016] Examples of the curing catalyst include organotin compounds such as dibutyltin diuranate, and organobismuth compounds such as triphenylbismuth (TPB). Among these, dibutyltin diuranate is preferred because of its high catalytic effect.
[0017] The content of the curing catalyst relative to 100 parts by mass of the glycidyl azide polymer is preferably 0.0020 parts by mass or more and 0.0023 parts by mass or less. If the content of the curing catalyst is less than the lower limit, the curing time becomes longer, and if the content of the curing catalyst exceeds the upper limit, degassing in the propellant becomes difficult due to high reactivity when mixed with the curing agent.
[0018] The diluent is used to dilute the curing catalyst. The diluent may include dioctyl adipate.
[0019] The content of the diluent per 100 parts by mass of the glycidyl azide polymer is preferably 0.03 parts by mass or more and 0.0345 parts by mass or less. If the content of the diluent is less than the lower limit, the operation of dropping the curing catalyst becomes difficult, whereas if the content of the diluent exceeds the upper limit, the amount of the curing catalyst required increases, and degassing in the propellant becomes difficult due to high reactivity when mixed with the curing agent.
[0020] The content of lithium fluoride per 100 parts by mass of the glycidyl azide polymer is preferably at least 1 part by mass. If the content of lithium fluoride is less than the lower limit, no significant difference appears in the linear burning rate of the GAP.
[0021] According to this embodiment, in a solid rocket propellant containing lithium fluoride and having a glycidyl azide polymer as a binder main component, the burning speed can be reduced more than that of a solid rocket propellant not containing lithium fluoride. In addition, since the negative catalytic action on the glycidyl azide polymer was found, a substance having a negative catalytic action on the oxidizer component was generally added when expanding the burning speed range of a solid propellant. According to this embodiment, the burning speed can be reduced for various solid propellants using a glycidyl azide polymer as a binder and for propulsion systems using a glycidyl azide polymer that is not limited to solid propellants. EXAMPLES
[0022] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.
[0023] [Example] <Production of solid rocket propellants> A mixture was prepared by mixing 91% by weight of glycidyl azide polymer, which is the main binder component, and 9% by weight of hexamethylene diisocyanate, which is the curing agent. Lithium fluoride was added in an amount of 1 part by mass, 5 parts by mass, or 10 parts by mass to 100 parts by mass of the above mixture to obtain a 6 mm x 6 mm x 60 mm sample (commonly called a strand propellant). The results of the combustion experiment are shown in Figure 1.
[0024] <Solid rocket propellant combustion experiment> An ignition fuse was placed about 5 mm from the top of the strand propellant, and break-wires were placed at 10 mm, 20 mm, 30 mm, and 40 mm from the top. The strand propellant was ignited by an ignition wire 5 mm from the top, burned downward to cut the break-wire, and the time difference between the cuts was measured. The burning rate was calculated by dividing the 10 mm distance between the break-wires by the cutting time. In order to perform this evaluation under pressure in a nitrogen atmosphere, the test was carried out using a combustion vessel called a chimney-type combustor, which can maintain a constant pressure during strand propellant combustion.
[0025] [Comparative Example] <Production of solid rocket propellants> A glycidyl azide polymer, which is the main binder component, was mixed at 91% by weight with hexamethylene diisocyanate, which is the curing agent, at 9% by weight to obtain a 6 mm x 6 mm x 60 mm sample (commonly called a strand propellant).
[0026] <Solid rocket propellant combustion experiment> A combustion experiment was carried out in the same manner as in the example, and the results are shown in FIG.
[0027] The results shown in Figure 1 confirm that the burning rate of solid rocket propellants containing lithium fluoride and with glycidyl azide polymer as the main binder component is reduced.
Claims
1. A solid rocket propellant comprising a binder base of glycidyl azide polymer and lithium fluoride.
2. 2. The solid rocket propellant according to claim 1, wherein the content of the lithium fluoride relative to 100 parts by mass of the glycidyl azide polymer is 1 part by mass or more and 10 parts by mass or less.