JP6790800B2 - Septum and multi-pulse rocket motor using it - Google Patents

Description

The present invention relates to a diaphragm for a multi-pulse rocket motor and a multi-pulse rocket motor using the diaphragm.

A multi-pulse rocket motor loaded with multiple solid propellants can generate thrust multiple times at any time by igniting and burning each propellant in turn, so a projectile equipped with a rocket motor The flight performance can be improved.

The propellant produces a pressure of several tens to over 100 atm and a temperature of over 3000 degrees when burned. Therefore, the motor case of the rocket motor and the unburned propellant are covered with a heat insulating material and a diaphragm having flexibility and high heat resistance in order to protect from the combustion flame of the propellant (see Patent Documents 1 and 2). ). In particular, as the diaphragm that protects the propellant, a rubber having high heat resistance mixed with heat-resistant fibers and a flame retardant is used to further improve the heat resistance.

In a multi-pulse rocket motor, when the first propellant is ignited and the diaphragm covering the second propellant is exposed to the combustion flame of the first propellant, the heat-resistant fibers and the flame retardant start thermal decomposition together with the rubber. During this thermal decomposition, carbides generated from rubber and heat-resistant fibers and thermal decomposition products of flame retardants form a thick carbide layer on the surface of the diaphragm. Once a carbide layer is formed on the surface of the diaphragm, the carbide layer blocks the flame, so that the amount of heat transfer to the rubber is reduced and the thermal decomposition rate is reduced. Therefore, by increasing the content of the heat-resistant fiber that plays a role of holding the carbide layer and the flame retardant that forms the carbide layer, the heat resistance of the diaphragm is improved, and as a result, the diaphragm can be made thinner and lighter. ..

When the first propellant finishes burning, the second propellant partitioned by the diaphragm is ignited and burned. When the second propellant is ignited, the diaphragm covering the second propellant is deformed and broken by the pressure of the combustion gas generated from the second propellant, and the combustion gas is ejected from the nozzle through the broken portion of the diaphragm. To. However, if the diaphragm breaks at multiple points, the broken diaphragm may separate from the motor case and flow to the nozzle together with the carbide layer on its surface, clogging the nozzle and affecting the injection of combustion gas. is there.

In order to solve such a problem, Patent Document 3 discloses a diaphragm in which a fragile portion is formed by laminating a plurality of rubber layers formed by abutting two rubber plates in a plane direction. .. The diaphragm protects the second propellant from flames during the combustion of the first propellant, and after the second propellant is ignited, it receives the pressure of the combustion gas generated from the second propellant and hits the fragile part. It is configured to break. As a result, the diaphragm can be broken at an arbitrary location, so that the diaphragm can be prevented from being detached from the motor case.

Japanese Unexamined Patent Publication No. 6-257514 Japanese Unexamined Patent Publication No. 2015-218624 Japanese Unexamined Patent Publication No. 2013-29100

However, even in the diaphragm of Patent Document 3, a large amount of generated carbide is retained on the surface of the diaphragm, so that if the diaphragm is broken even in a portion other than the fragile portion, a large amount of carbide will flow to the nozzle at once. May clog the nozzle.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the amount of carbides retained on the diaphragm surface so as not to become excessive when exposed to the combustion flame of a propellant. Is to provide a diaphragm that can.

The present invention is a diaphragm arranged between a first propellant and a second propellant of a multi-pulse rocket motor, and has a first heat-resistant layer and a second heat-resistant layer that form a carbide layer by thermal decomposition. However, the first heat-resistant layer has a higher holding power than the second heat-resistant layer, and the diaphragm is thermally decomposed during combustion of the first propellant and before combustion of the second propellant. Is a diaphragm in which the first heat-resistant layer and the second heat-resistant layer are laminated so as to reach the second heat-resistant layer from the first heat-resistant layer side.

The first heat-resistant layer preferably has a higher content of heat-resistant fibers than the second heat-resistant layer.

The first heat-resistant layer preferably has a longer average fiber length of heat-resistant fibers contained than the second heat-resistant layer.

The first heat-resistant layer and the second heat-resistant layer are preferably made of rubber containing the heat-resistant fibers and a flame retardant.

It is preferable that the first heat-resistant layer and the second heat-resistant layer are alternately laminated.

The multi-pulse rocket motor of the present invention is characterized by having the diaphragm.

When the thermal decomposition of the diaphragm reaches the second heat-resistant layer from the first heat-resistant layer side during the combustion of the first propellant, the diaphragm of the present invention has a first heat-resistant layer because the holding power of the carbide layer is low. Carbides generated by the thermal decomposition of the heat-resistant layer peel off and fall off from the diaphragm surface. This makes it possible to reduce the carbides retained on the surface of the diaphragm and prevent a large amount of carbides from flowing into the nozzle at once when the diaphragm is broken or detached.

It is a schematic cross-sectional view of the multi-pulse rocket motor which concerns on embodiment of this invention. It is a figure which shows the combustion state of the 1st propellant of the multi-pulse rocket motor. It is a figure which shows the combustion state of the 2nd propellant of the multi-pulse rocket motor. It is a schematic cross-sectional view which shows the state before combustion of the conventional diaphragm. It is a figure which shows the state of the combustion middle stage of the 1st propellant of the conventional diaphragm. It is a figure which shows the state of the combustion end stage of the 1st propellant of the conventional diaphragm. It is a schematic cross-sectional view which shows the state before combustion of the diaphragm which concerns on the said embodiment. It is a figure which shows the state of the combustion middle stage of the 1st propellant of the diaphragm which concerns on the said embodiment. It is a figure which shows the state of the final stage of combustion of the 1st propellant of the diaphragm which concerns on the said embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, the configuration of the multi-pulse rocket motor will be described, and then the diaphragm used therein will be described.

As shown in FIG. 1, the first propellant 22 and the second propellant 24, which are solid fuels, are loaded in the motor case 20 of the rocket motor 10, and the first propellant 22 and the second propellant 22 are loaded. It is separated from the drug 24 by a diaphragm 26. Further, on the front portion (left side in FIG. 1) of the motor case 20, a first ignition device 28 and a second ignition device 30 for igniting the first propellant 22 and the second propellant 24 are provided, respectively, and a motor is provided. A nozzle 32 for ejecting combustion gas is provided at the rear portion (right side in FIG. 1) of the case 20. The rocket motor 10 of the present embodiment has two propellants and two ignition devices, but may be three or more depending on the configuration of the rocket motor. In that case, a diaphragm is installed between each propellant.

The motor case 20 is formed into a substantially cylindrical shape, and high-strength high-strength steel, a lightweight aluminum alloy, an FRP case, or the like is used, and the inner surface thereof is made of heat-resistant rubber or FRP to protect it from flames. Insulation is glued. Further, graphite having high heat resistance is used for the nozzle 32 so as to withstand high temperature and high pressure combustion gas.

The first propellant 22 and the second propellant 24 are general composite propellants and double-base propellants, which are preformed into a predetermined shape or a motor case 20 loaded with a core and propellant. The slurry is cast and molded. In the present embodiment, the second propellant 24 is formed in a substantially cylindrical shape, and the first propellant 22 formed in a substantially cylindrical shape is concentrically arranged in the hollow portion thereof. The diaphragm 26 arranged between the first propellant 22 and the second propellant 24 is inside the motor case 20 so that the second propellant 24 is not burned by the flame during the combustion of the first propellant 22. It covers the entire surface of the second propellant 24 facing the space. Further, by adhering the end portion of the diaphragm 26 to the motor case 20, the combustion flame of the first propellant 22 is prevented from wrapping around the back side of the diaphragm 26.

Although not shown, the first ignition device 28 and the second ignition device 30 contain an initiator that ignites by passing an electric current and an ignition charge ignited by the flame of the initiator in an ignition charge case. The first propellant 22 is ignited when the first igniter 28 burns, and the second propellant 24 is ignited when the second igniter 30 burns.

Subsequently, the configuration of the diaphragm 26 will be described. As shown in FIG. 7, the diaphragm 26 is composed of two layers of the first heat-resistant layer 26A and two layers of the second heat-resistant layer 26B alternately laminated. Although the detailed composition and the like will be described later, both the first heat-resistant layer 26A and the second heat-resistant layer 26B are formed of a material that forms a carbide layer by thermal decomposition, and the first heat-resistant layer 26A is the second heat-resistant layer 26B. It is formed so that the holding power of the carbide layer is higher than that of the carbide layer. The holding power of the carbide layer means the property that the carbides forming the carbide layer are not easily separated or peeled off from the surface of the heat-resistant layer. That is, the higher the holding power of the carbide layer, the more difficult it is for carbides to fall off from the surface of the heat-resistant layer, and as a result, many carbide layers are formed and remain on the surface of the heat-resistant layer. The diaphragm 26 is designed so that the thermal decomposition of the diaphragm 26 reaches the second heat-resistant layer 26B from the first heat-resistant layer 26A side during the combustion of the first propellant 22 and before the combustion of the second propellant 24. The thickness, shape, and the like of the first heat-resistant layer 26A and the second heat-resistant layer 26B can be appropriately changed according to the usage mode. The first heat-resistant layer 26A and the second heat-resistant layer 26B of the present embodiment each have two layers, but each layer may be one layer or three or more layers. However, it is necessary to arrange the diaphragm 26 so that at least one second heat-resistant layer 26B is located closer to the second propellant 24 than at least one first heat-resistant layer 26A.

The diaphragm 26 needs to be flexible in order to withstand deformation when pressure is applied, but it also needs to have high heat resistance to withstand the high temperature flame of the first propellant 22 and protect the second propellant 24. is there. Therefore, for the diaphragm 26, a composition is used in which a rubber having flexibility and heat resistance is used as a base material, and heat-resistant fibers, a flame retardant, a vulcanizing agent and other additives are arbitrarily mixed therein.

Examples of the base rubber include ethylene propylene diene rubber (EPDM), neoprene rubber, butadiene rubber, natural rubber, butyl rubber, nitrile rubber, and urethane rubber, which have flexibility and heat resistance, and among them, EPDM and neoprene rubber. Rubber having high heat resistance and cold resistance is preferable. The advantage of using rubber having high cold resistance is that the flexibility of the diaphragm 26 can be guaranteed even in a low temperature environment.

Examples of the heat-resistant fiber include aramid fiber, carbon fiber, polyimide fiber, polyallylate fiber, glass fiber, and polyphenylene sulfide fiber, and aramid fiber that is carbonized by heat is preferable. The average fiber length of the heat-resistant fibers used is usually 0.5 to 3 mm. In the present invention, the description of "○○ to △△" indicating the numerical range means the numerical range including the upper limit and the lower limit thereof unless otherwise specified. That is, "○○ to △△" means "more than ○○ and less than △△".

Examples of flame retardants include antimony trioxide, zinc sulfide, phosphorus compounds, chlorine compounds, bromine compounds, metal hydroxides, and hydrated metal salts, and antimony trioxide, zinc sulfide, chlorine compounds, bromine compounds, and phosphorus compounds. Preferably, antimony trioxide is particularly preferred.

Examples of the vulcanizing agent include sulfur and organic peroxides. In addition, examples of other additives include chlorinated paraffin, halogenated hydrocarbon, carbon black, zinc oxide, and hydrocarbon resin, and the addition of chlorinated paraffin and halogenated hydrocarbon enhances flame retardancy. Is advantageous.

The first heat-resistant layer 26A of the present invention may be configured to have a higher holding power of the carbide layer than the second heat-resistant layer 26B, and the means thereof is not particularly limited. As such a means, for example, the heat-resistant fiber contained in the first heat-resistant layer 26A has a higher content rate in the first heat-resistant layer 26A than the second heat-resistant layer 26B of the heat-resistant fiber that plays a role of holding the carbide layer. In the first heat-resistant layer 26A, the heat-resistant fibers are arranged perpendicular to the layer, and in the second heat-resistant layer 26B, the heat-resistant fibers are arranged parallel to the layer. It can be mentioned to rank. In the present embodiment, since the means for increasing the content of the heat-resistant fiber in the first heat-resistant layer 26A is higher than that in the second heat-resistant layer 26B, the first heat-resistant layer 26A and the second heat-resistant layer 26B are described below. The composition ratio of the components will be described.

The first heat-resistant layer 26A of the present embodiment contains 40 to 65% by mass of rubber, 4 to 20% by mass of heat-resistant fibers, 8 to 15% by mass of flame retardant, and 10 to 35% by mass of vulcanizing agent and other additives. It is formed from a rubber composition containing%.

On the other hand, as the second heat-resistant layer 26B having a low carbide layer holding power, a rubber composition having a lower heat-resistant fiber content than the combined first heat-resistant layer 26A is used. However, in order to effectively reduce the carbide layer retained on the surface of the diaphragm 26, the second heat-resistant layer 26B contains 3% by mass or less of heat-resistant fibers, 2 to 10% by mass of flame-retardant, and heat-resistant fibers. The total amount of the flame retardant is preferably 2 to 13% by mass, more preferably 1 to 2% by mass of the heat resistant fiber, 5 to 8% by mass of the flame retardant, and the total amount of the heat resistant fiber and the flame retardant. It is 6 to 10% by mass. The rubber layer containing 0% of both the heat-resistant fiber and the flame retardant has a very low holding power of the carbide layer and exhibits a characteristic of being inferior in heat resistance. However, if the heat resistance required for the diaphragm 26 can be sufficiently satisfied by laminating this rubber layer with the first heat resistant layer 26A having high heat resistance, such a rubber layer is used as the second heat resistant layer 26B. You can also do it.

In order to manufacture the diaphragm 26 in which the first heat-resistant layer 26A and the second heat-resistant layer 26B are laminated, each of the two types of rubber compositions is molded into a sheet shape, and the laminated state is passed through a rotating roller to generate air bubbles. A method of crimping while removing the rubber or crimping with a flat plate press can be used. By charging the rubber having a laminated structure thus produced into a mold and press-vulcanizing it, a diaphragm 26 having a laminated structure having a predetermined shape can be produced.

Next, the operating mechanism of the rocket motor 10 will be described with reference to FIGS. 1 to 3. FIG. 1 shows a state before the rocket motor is ignited. When the first ignition device 28 is ignited in this state, the first propellant 22 burns, and the combustion gas is ejected from the nozzle 32 to generate a predetermined thrust (see FIG. 2). During this time, the second propellant 24 is protected by the diaphragm 26. When the second ignition device 30 is ignited after a lapse of a predetermined time, the second propellant 24 burns, the diaphragm 26 is broken by the pressure of the generated combustion gas, and the combustion gas is ejected from the nozzle 32 to generate thrust (FIG. 3). The white arrows in FIGS. 2 and 3 indicate the flow directions of the combustion gas, respectively.

Subsequently, a state in which the conventional diaphragm 40 and the diaphragm 26 of the present embodiment are burnt while the first propellant 22 is burning will be described with reference to FIGS. 4 to 9. The white arrows in FIGS. 5, 6, 8 and 9 indicate the flow direction of the combustion gas. 4 to 6 are views showing a process in which the conventional diaphragm 40 is burnt by a combustion flame. As shown in FIG. 4, the diaphragm 40 made of rubber containing a large amount of heat-resistant fibers is arranged so as to cover the second propellant 24. Then, when the combustion of the first propellant is started, the surface of the diaphragm opposite to the second propellant 24 is exposed to the flame as shown in FIG. 5, and the carbide generated by the thermal decomposition of the rubber is the diaphragm 40. The carbide layer 42 is formed by being held on the surface of the material. Then, near the end of combustion of the first propellant, a very thick carbide layer 42 is formed on the surface of the diaphragm 40, as shown in FIG. When the diaphragm 40 is deformed or broken by the combustion of the second propellant 24, it may flow into the nozzle together with a large amount of retained carbide and clog the nozzle.

On the other hand, FIGS. 7 to 9 show a process in which the diaphragm 26 of the present embodiment is burnt by a combustion flame. As shown in FIG. 7, the diaphragm 26 is arranged so that the second heat-resistant layer 26B is located on the second propellant 24 side. Then, when the combustion of the first propellant 22 is started, the carbide layer 42 is formed on the surface as the first heat-resistant layer 26A is thermally decomposed by the flame (see FIG. 8), but the second heat-resistant layer is formed. At the site where the burnout reaches 26B, the carbide layer 42 gradually peels off, so that a large amount of carbide is not retained on the surface of the diaphragm 26 (see FIG. 9). Therefore, since the amount of carbides that fall off when the diaphragm 26 is broken can be reduced, there is no risk of the nozzle 32 being clogged.

The results of the evaluation test of the diaphragm 26 of the present embodiment are shown below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Creation of septum>
Ethylene propylene diene rubber (EPDM) is 47% by mass as the base rubber, Kevlar fiber with an average fiber length of 1 mm is 14% by mass as the heat resistant fiber, antimony trioxide is 12% by mass as the flame retardant, and organic peroxide is used as the vulcanizing agent. On the first heat-resistant layer having a thickness of 2 mm containing 4% by mass of a product (manufactured by Nichiyu Co., Ltd .: Perhexa V40) and 23% by mass of chlorinated paraffin as another additive, 59% by mass of EPDM as a base rubber 2% by mass of Kevlar fiber with an average fiber length of 1 mm as a heat-resistant fiber, 7% by mass of antimony trioxide as a flame retardant, and 4% by mass of organic peroxide (manufactured by Nichiyu Co., Ltd .: Perhexa V40) as a vulcanizing agent. A second heat-resistant layer having a thickness of 3 mm containing 28% by mass of chlorinated paraffin as another additive was laminated and pressure-bonded to each other by a rotating roller. Then, the crimped rubber laminate was placed in a mold and press-vulcanized under the condition of a temperature of 140 ° C. to form the diaphragm of Example 1.

The diaphragms of Examples 2 to 4 and Comparative Examples 1 and 2 having the compositions shown in Table 1 below were prepared in the same manner as the diaphragm of Example 1 above. The exact unit of composition in Table 1 is mass%.

The following torch burner test was performed in order to evaluate the heat resistance of the obtained diaphragm and the holding power of the carbide layer.

<Torch burner test>
The diaphragms of each Example and Comparative Example were cut out to a size of 10 cm square, and the obtained sample was attached to a metal frame. Propane gas: Air was mixed at a ratio of 1:10, and this sample was roasted for 120 seconds from the first heat-resistant layer side using a gas burner adjusted to a gas flow rate of 2.8 L / s to obtain the first heat-resistant layer. Was completely burnt down, and the second heat-resistant layer was burnt down halfway. Then, the amount of the carbide layer formed on the surface of the second heat-resistant layer (holding power of the carbide layer) and the heat resistance (burning rate) were evaluated. The evaluation results are shown in Table 1 above.
The amount of the carbide layer formed was evaluated by scraping off the carbide remaining on the sample surface, measuring the mass of the carbide, calculating the amount of carbide per unit area, and evaluating it in the following four stages.
Less than 20 mg / cm ² : Very low 20 mg / cm ² or more, 25 mg / cm Less than ² : Low 25 mg / cm ² or more, 30 mg / cm Less than ² : High 30 mg / cm ² or more: Very high Heat resistance is carbide The difference between the thickness of the sample scraped off and the thickness of the sample before the test was taken as the burnout thickness, and the burnout rate per minute was calculated and evaluated in the following four stages.
Less than 1 mm / min: Very good 1 mm / min or more and less than 2 mm / min: Good 2 mm / min or more and less than 3 mm / min: Bad 3 mm / min or more: Very bad

With reference to the results of the torch burner test shown in Table 1, in Examples 1 to 4, the amount of the carbide layer formed was small and the heat resistance was also good. On the other hand, in Comparative Examples 1 and 2, although the heat resistance was good, the content of the heat-resistant fibers in the first heat-resistant layer was the same as that in the second heat-resistant layer, so that the amount of the carbide layer produced was very large.

10 Rocket motor 20 Motor case 22 First propellant 24 Second propellant 26 Diaphragm 26A First heat-resistant layer 26B Second heat-resistant layer 28 First ignition device 30 Second ignition device 32 Nozzle

Claims (6)

It is a diaphragm arranged between the first propellant and the second propellant of the multi-pulse rocket motor, and has a first heat-resistant layer and a second heat-resistant layer that form a carbide layer by thermal decomposition.
The first heat-resistant layer has a higher holding power of the carbide layer than the second heat-resistant layer.
The first heat-resistant layer and the first heat-resistant layer so that the thermal decomposition of the diaphragm reaches the second heat-resistant layer from the first heat-resistant layer side during the combustion of the first propellant and before the combustion of the second propellant. A diaphragm in which a second heat-resistant layer is laminated. The diaphragm according to claim 1, wherein the first heat-resistant layer has a higher content of heat-resistant fibers than the second heat-resistant layer. The diaphragm according to claim 1, wherein the first heat-resistant layer has a longer average fiber length of heat-resistant fibers contained than the second heat-resistant layer. The diaphragm according to any one of claims 1 to 3, wherein the first heat-resistant layer and the second heat-resistant layer are made of rubber containing heat-resistant fibers and a flame retardant. The diaphragm according to any one of claims 1 to 4, wherein the first heat-resistant layer and the second heat-resistant layer are alternately laminated. A multi-pulse rocket motor having a diaphragm according to any one of claims 1 to 5.

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