JPS6219400B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to composite propellants. More specifically, the object is to provide a composite propellant having an improved composition so as to obtain a high specific impulse. Conventionally, composite propellants have as their basic ingredients rubber or plastic (e.g., polybutadiene, polyurethane, polysulfide, etc.) as a fuel and binder, ammonium perchlorate as an oxidizing agent, and a compound that increases the combustion temperature. Contains metal powder, such as aluminum powder, as a combustion aid to stabilize combustion. The most important performance of a solid rocket motor is its specific impulse (thrust Kgf).
× combustion time sec/propellant weight Kg), and when developing propellants, a standard rocket motor for testing is used to measure the specific impulse of the test propellant and analyze its performance. . Hereinafter, the specific impulse under the standard conditions will be referred to as the specific impulse of the propellant. Therefore, in order to obtain even higher specific impulse, in recent years, a fourth type of composite propellant has been added.
Various attempts have been made to include nitramine such as cyclotrimethylenetrinitramine (ie, RDX) and cyclotetramethylenetetranitramine (ie, HMX) as the second basic component.
[AIAA-81-1582 Combustion of Nitramine
Composite Propellants (July 27-29 1981)]. However, when adding these nitramines to a composite propellant, theoretically, as the nitramine content is gradually increased, the specific impulse will gradually increase, and the specific impulse at a nitramine content of about 20% by weight will reach the maximum. However, when the nitramine content is increased beyond about 5% by weight, a phenomenon occurs in which the specific impulse of the propellant gradually decreases. When the cause of this was investigated, it was found that the metal powder was made flame retardant by the addition of nitramine, and the metal powder was ejected from the nozzle without being fully combusted. For example, in spherical rockets where the average distance from the combustion surface of the propellant to the nozzle throat is short, relatively small metal powder with an average particle size of about 7 microns is generally used to improve combustion completion. However, if nitramine is added, even such small metal powders cannot be completely combusted. Therefore, the content of nitramine has to be reduced, which further restricts the performance improvement of the propellant. On the other hand, composite gas generating agents have an average particle size of
It was discovered in Japanese Patent Application Laid-Open No. 1983-1982 that the amount of gas generated can be increased by adding metal particles of 0.2 microns or less.
It is known from Publication No. 62880. However, the use of such fine metal particles in combination with nitramine;
Furthermore, by using nitramine in combination with coarse metal particles, the specific impulse of the propellant can be increased to its theoretical maximum value, which can prevent the decrease in specific impulse that would occur when the nitramine content is increased. It was not previously known that this was possible. Incidentally, an in-gas evaporation method is known as a method for producing metal powder, for example, aluminum powder.
This method vaporizes aluminum in a high vacuum and solidifies the extremely dilute aluminum gas particles.During solidification, aluminum particles are prevented from coming together and increasing in particle size, resulting in extremely fine particles. Aluminum powder is produced. The particle size of aluminum powder obtained by this method is up to 0.5
Micron, the smallest is about 0.07 micron. In a composite propellant containing nitramine, for example, the present invention creates a good combustion atmosphere for conventional metal powder with an average particle size of 7 microns to achieve complete combustion of the metal powder, and thereby The specific impulse of the propellant is increased by increasing the specific impulse of the propellant. That is, the present invention provides a composite propellant containing a nitramine such as cyclotrimethylenetrinitramine or cyclotetramethylenetetranitramine and a metal powder, in which the metal powder has an average It is a composite propellant characterized by consisting of fine metal powder with a particle size of 0.5 microns or less and coarse metal powder with a larger particle size. Conventionally, coarse metal powders selected from the group of aluminum, boron, nickel, and silver have been preferably used. The fine metal powder of the present invention also contains one of these metals.
- Two or more types can be appropriately selected and used.
Such fine metal powder is usually produced by the above-mentioned in-gas evaporation method, and the fine metal powder can be used in the present invention. Here, the total composition of fine metal powder and coarse metal powder (relative to the propellant) is determined based on the calorific value required for the propellant, as well as the physical properties or manufacturability of the propellant, especially the raw materials. It is determined by taking into account the particle size of the slurry. According to the present invention, since fine metal powder with an average particle size of 0.5 microns or less is blended into a composite propellant containing nitramine and metal powder (the above-mentioned coarse metal powder), the propellant burns from its surface. During this process, fine metal powder is first released on or from the surface and then rapidly completes combustion, releasing a large amount of thermal energy into the combustion chamber in a short period of time, which heats the combustion gas to a high temperature. As a result, a good oxidizing atmosphere is provided to the coarse metal powder. Therefore, this coarse-grained metal powder can also complete combustion within the combustion chamber, thereby reducing energy loss even in the case of the spherical rocket, and improving the combustion of such metal powder. As shown in the examples described later, it is possible to increase the blending ratio of nitramine up to the theoretical maximum value, and by doing so, it is possible to increase the specific impulse of the propellant. As is clear from the above explanation, fine metal powder causes the atmosphere in the combustion chamber to tend to oxidize, so the burning rate of the fuel and binder tends to increase, and the burning rate of the propellant also tends to increase. Therefore, when planning the combustion speed to be within the normal range, for example around 10 mm/sec, the content of fine metal powder should be 0.5 to 0.7% by weight of the propellant, and if more emphasis is placed on combustion stability.
A suitable amount is 0.5 to 5% by weight. Hereinafter, the present invention will be explained in detail with reference to Examples. Note that the average particle diameter in the present invention is a value measured using a light transmission type particle size analyzer. Note that this measuring device can also measure particle size distribution (weight ratio). Also, the burning speed and specific impulse of the propellant (actually measured values)
was measured using a small rocket motor loaded with a test propellant grain of an internal end-face combustion type with an outer diameter of 80 mm, an inner diameter of 40 mm, and a length of 140 mm. Example 1 and Comparative Example 1 Polyurethane obtained by blending polyisocyanate and a small amount of chain extender with polybutadiene having a hydroxyl group end was used as a fuel and binder, and (a) 11% by weight of fuel and binder. , (b) 49% by weight of ammonium perchlorate, (c) Metallic aluminum powder with an average particle size of 7 microns or less (labeled as coarse Al powder) and metal aluminum powder with an average particle size of 0.2μ (labeled as fine Al powder) (d) HMX20 with an average particle size of 200μ
A composite propellant grain having a composition of % by weight was prepared and its combustion test was conducted. Details of the propellant composition, slurry viscosity of the raw material for producing propellant grains, and combustion tests of the propellant grains are shown in Table 1. For comparison, Table 1 also shows the performance of propellants that do not contain nitramine and have the same content of fuel/binder and aluminum powder.

[Table] From the comparison of Experiment Nos. 1 and 2, although theoretically the specific impulse should increase when HMX is mixed,
The specific impulse actually obtained is lower, and the efficiency of specific impulse is 92.5 in experiment number 1 (without HMX mixed).
%, but in Experiment No. 2 (20% HMX mixed), it decreased to 88.8%, which shows that the combustion efficiency is getting worse. Experiment number 3 is a propellant containing HMX with fine Al particles.
With the powder containing 0.5% by weight, the specific impulse efficiency increased significantly compared to Experiment No. 2, and the specific impulse actually obtained recovered to almost the same level as Experiment No. 1, and the combustion rate was lower than that of Experiment No. 1. It has the advantage of being lower than number 1. As shown in experiment numbers 4 to 7,
As the content of fine Al powder increases, the efficiency of specific impulse gradually increases and can even be made higher than the value of Experiment No. 1, and the increase in specific impulse actually obtained is quite remarkable. However, in Experiment No. 7, the viscosity of the slurry increased significantly, making it difficult to produce propellant grains with complex shapes, and the burning rate also tended to be somewhat too high. Example 2 (a) 11% by weight of the same fuel and binder used in Example 1, (b) 49% by weight of ammonium perchlorate, the same as used in Example 1, (c) the same as used in Example 1. Coarse grain
18% by weight of Al powder and 2% by weight of aluminum powder with an average particle size of 0.5μ or less but different in average particle size (indicated as fine Al powder), total 20% by weight, (d) Same as used in Example 1. A composite propellant grail with a composition of 20% by weight of HMX was prepared and a combustion test was conducted to investigate the influence of the average particle size of fine Al powder. The test conditions are the same as in Example 1. The results obtained are shown in Table 2. For comparison, the results of Experiment No. 2 (Comparative Example 1) are also listed in Table 2.

[Table] From the above results, the average particle size of fine Al powder is 0.5μ.
All of the following materials significantly improve specific impulse efficiency (and therefore combustion efficiency), but it can be seen that among them, those with a smaller average particle diameter have a greater improvement effect. Example 3 (a) 11% by weight of the same fuel and binder used in Example 1, (b) 49% by weight of ammonium perchlorate, the same as used in Example 1, (c) the same as used in Example 1. Coarse grain
A total of 20 metal powders, including 19% by weight of Al powder and 1% by weight of other metal powders (indicated as fine metal powders) with an average particle size of 0.2μ
(d) A composite propellant grain having the same composition of 20% by weight of HMX as used in Example 1 was prepared and a combustion test was conducted to examine the influence of the type of metal in the fine metal powder. The test conditions are the same as in Example 1. The results obtained are shown in Table 3. For comparison, the results of Experiment No. 2 (Comparative Example 1) are also listed in Table 3.

【table】

[Table] In Table 3, the specific impulse of experiment numbers 11, 12, and 13 in which fine metal powder other than aluminum was mixed is not exactly 258.4 [Kgf・sec/Kg], but considering the purpose of the present invention, The basic principle lies in the propellant containing aluminum powder, and if the amount of fine metal powder is reduced or not added at all, aluminum powder should be added instead, so as a theoretical value (= ideal value), fine powder The value when the metal powder is metallic aluminum powder was adopted. From the results in Table 3, it can be seen that the specific impulse efficiency (and therefore the combustion efficiency) can be significantly improved even if metals other than aluminum are used as fine metal powder with an average particle size of 0.5 microns or less. Example 4 and Comparative Example 2 This example uses RDX instead of HMX as nitramine.
This study investigated the effects of using . (a) 11% by weight of the same fuel/binder used in Example 1, (b) 49% by weight of ammonium perchlorate, the same as used in Example 1, (c) Same coarse particles as used in Example 1.
A composite having a composition of a total of 20% by weight of Al powder (average particle size 7 μm) and the same fine Al powder used in Example 1 (average particle size 0.2 μm), and (d) 20% by weight RDX with an average particle size of 200 μm. We created propellant grains and conducted combustion tests. The test conditions are the same as in Example 1. Details of the propellant composition and combustion test results are shown in Table 4. For comparison, Table 4 also shows the data of Experiment No. 4 (Example 1), which had the same composition as this example except that HMX was used instead of RDX.

[Table] From the results in Table 4, it can be seen that the effects of the present invention can be obtained even when RDX is used instead of HMX.

Claims (1)

[Scope of Claims] 1. A composite propellant containing a nitramine such as cyclotrimethylenetrinitramine or cyclotetramethylenetetranitramine and a metal powder, wherein the metal powder is a fine metal powder with an average particle size of 0.5 microns or less. and coarse-grained metal powder with a larger particle size. 2. The composite propellant according to claim 1, wherein the content of fine metal powder having an average particle diameter of 0.5 microns or less is 0.5% to 5% by weight based on the propellant. 3 Fine metal powder with an average particle size of 0.5 microns or less,
The composite propellant according to any one of claims 1 to 2, characterized in that it is made of one or more metals selected from the group consisting of aluminum, boron, nickel, and silver. .