JP7180210B2 - rocket motor - Google Patents

Description

The present invention relates to a rocket motor that obtains rocket propulsion by burning fuel.

There are two types of rocket motors: a type that burns solid fuel to generate propulsion, and a type that burns liquid fuel to generate propulsion. Rocket motors equipped with solid fuels have simpler structures than rocket motors equipped with liquid fuels because they do not require a structure to prevent liquid leakage. Moreover, solid fuel (propellant) can be stored for a long time in a state filled in a case compared to liquid fuel.

Patent Literature 1 discloses an example of a rocket motor loaded with solid fuel. As shown in FIG. 9, this rocket motor 11 has a bottomed cylindrical motor case 12 and a solid propellant (solid fuel) 16 housed in the motor case 12 . The motor case 12 has a case lid 13a, and the case lid 13a is provided with a cylindrical nozzle 13b. The solid propellant 16 has a first end face 16a facing the nozzle 13b and a second end face 16b opposite to the first end face 16a. Only the first end surface 16 a of the solid propellant 16 burns within the motor case 12 . As a result, combustion gas is generated at a constant rate, and the rocket motor 11 generates a constant driving force for a constant period of time.

Such a rocket motor 11 is also called an end face combustion type rocket motor. As shown in FIG. 9, the end-firing rocket motor 11 has a heat-insulating structure in order to prevent the motor case 12 from burning out or to suppress the temperature rise of the solid propellant 16 . The heat insulating structure of the conventional rocket motor 11 is a two-layer structure, and has a restrictor 15 covering the outer peripheral surface of the solid propellant 16 and a case heat insulating material 14 covering the inner peripheral surface of the motor case 12 . The restrictor 15 and the case heat insulating material 14 have a predetermined thickness in order to obtain heat insulating properties and desired strength. However, the two-layer structure has the problem that the amount of propellant to be accommodated in the motor case 12 is small, or the number of parts is large.

JP 2006-46145 A

A structure in which the heat insulating structure is a single layer structure, that is, a structure in which the restrictor and the case heat insulating material are integrated is also conceivable. However, there is a difference in thermal shrinkage between the propellant and the motor case. Therefore, the contraction of the motor case cannot catch up with the contraction of the propellant at low temperatures, and additional force is applied to the structure. This may cause peeling of the propellant from the insulator or cracks inside the propellant.

When the flame during combustion reaches this peeled portion or crack, the flame spreads to the peeled portion or crack, and the actual burning area increases more than the planned burning area. An increase in the combustion area results in an increase in pressure within the motor case. As a result, a problem called burst, such as breakage of the motor case or breakage of the screw joint, may occur. Therefore, there has been a need for a motor case containing a large amount of propellant, a small number of parts, and suppressing the occurrence of burst.

According to one aspect of the present disclosure, a rocket motor has a propellant for propelling the rocket, a motor case containing the propellant, and an insulator. The motor case has a nozzle at one end. The insulator has an inner peripheral surface facing the propellant and an outer peripheral surface facing the motor case. The inner peripheral surface of the insulator has an insulator bonding area that is bonded to the entire outer periphery of the propellant. The outer peripheral surface of the insulator has a case-bonded region that is bonded to the inner peripheral surface of the motor case and a case-unbonded region that is not bonded to the inner peripheral surface of the motor case. A propellant charge has an end face facing the nozzle and extends longitudinally. The case unbonded region is formed over substantially the entire length of the propellant in the longitudinal direction.

The case unbonded areas thus allow the insulator to move with the propellant relative to the motor case. Therefore, the difference in thermal deformation between the motor case and the propellant caused by the difference between the thermal expansion coefficients of the motor case and the propellant is absorbed by the non-bonded area of the case. As a result, the transmission of the external force caused by the difference in thermal deformation to the propellant is reduced. The reduction of the external force suppresses the separation of the propellant from the insulator. Alternatively, it is possible to suppress cracks occurring inside the propellant due to heat shrinkage. A so-called burst can be suppressed by suppressing the portion of the propellant that is separated from the insulator or the crack of the propellant. Moreover, the insulator has a single-layer structure. Therefore, by making the insulator thinner, the inner diameter of the insulator becomes larger, and the amount of propellant can be increased. The insulator also has fewer parts than the conventional two-layer structure.

Further, the case unbonded region allows the propellant to move with respect to the motor case over substantially the entire length of the propellant in the longitudinal direction. As a result, the difference in thermal deformation between the propellant and the motor case is absorbed over the entire longitudinal length of the propellant. Thus, separation of the propellant from the insulator and occurrence of cracks inside the propellant can be suppressed more effectively.

According to another feature of the present disclosure, the case bond region may have a longitudinally extending bond region circumferentially adjacent to the case unbonded region and extending longitudinally of the propellant charge. The insulator thus retains the propellant charge by means of the case bond area. For example, the case adhesive region can restrain the propellant from rotating in the circumferential direction with respect to the insulator.

According to another feature of the present disclosure, the case bonding area has an annular bonding area formed along the entire circumferential circumference of the inner peripheral surface of the motor case. Therefore, the annular adhesive region can suppress combustion gas from entering between the motor case and the insulator. Therefore, it is possible to suppress the melting of the inner peripheral surface of the motor case by the high-temperature combustion gas.

According to another feature of the present disclosure, the annular bond region may be formed closer to the nozzle than the burning end of the propellant charge. Therefore, the annular adhesive region suppresses combustion gas from entering between the motor case and the insulator at a location closer to the nozzle than the combustion end face of the propellant. As a result, the melting of the inner peripheral surface of the motor case can be suppressed more reliably.

According to another feature of the present disclosure, the annular adhesive region can have a width in the longitudinal direction of the propellant charge that is less than or equal to one-half the length of the propellant charge. That is, the annular adhesive region has a relatively short width in the longitudinal direction. Conversely, the longitudinal length of the case unbonded region is long. Therefore, the case unbonded region can reliably allow the insulator to move with the propellant relative to the motor case.

1 is a perspective view of a rocket motor according to an embodiment; FIG. FIG. 4 is an exploded perspective view of the rocket motor in the middle of the manufacturing process; FIG. 2 is a cross-sectional view taken along line III-III of FIG. 1; 4 is a cross-sectional view taken along line IV-IV of FIG. 3; FIG. 4 is a cross-sectional view taken along line VV of FIG. 3; FIG. FIG. 6 is a cross-sectional view showing a state in which the propellant in FIG. 5 is contracted; 1 is a cross-sectional view of a rocket motor in a combustion state; FIG. It is a sectional view of the rocket motor concerning other embodiments. 1 is a cross-sectional view of a conventional rocket motor; FIG.

An embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the rocket motor 1 has a motor case 1a, an insulator 4 housed in the motor case 1a, and a propellant 5 arranged (included) in the insulator 4. As shown in FIG. The motor case 1 a has a case body 2 and a case lid 3 that closes the opening of the case body 2 .

As shown in FIG. 3, the case main body 2 has a cylindrical shape with a bottom, and has a cylindrical side peripheral wall 2a and a disk-shaped case bottom wall 2b covering the bottom surface. The case body 2 is made of a material, such as metal, having a strength capable of withstanding high pressure during propellant combustion.

As shown in FIGS. 1 to 3, the case lid 3 has a panel 3a and a nozzle 3b. The end plate 3 a is disc-shaped and thicker than the case body 2 . The rear surface of the end plate 3a (corresponding to the lower surface in FIG. 3) is heat-resistant so as not to be melted by the combustion gas. A nozzle 3b is provided in the central portion of the end plate 3a. The nozzle 3b protrudes cylindrically from the outer peripheral surface of the end plate 3a. That is, the nozzle 3b is provided at one end of the motor case 1a.

As shown in FIG. 3, the case lid 3 has a through hole 3c and a spout 3d that are continuous. The through hole 3c extends from the rear surface of the end plate 3a toward the front surface (corresponding to the upper surface in FIG. 3), and gradually decreases in diameter. The ejection port 3d extends from the through hole 3c to the tip of the nozzle 3b and gradually widens in diameter. The through hole 3c and the ejection port 3d allow the combustion gas to be ejected from the inside of the motor case 1a through the nozzle 3b. The shape of the through hole 3c and the ejection port 3d allows combustion gas to be ejected at a very high speed.

As shown in FIGS. 1 to 3, the insulator 4 has a substantially cylindrical side wall 4a and a bottom wall 4b closing the bottom of the side wall 4a. The insulator 4 is made of a material that has some degree of flexibility and heat insulation. The composition of the material used for the insulator 4 is not particularly limited, but in addition to the elastomer functioning as a binder, it generally contains a filler and a flame retardant to improve mechanical properties and impart heat resistance. target. Preferably, the elastomer is a vulcanizable elastomer. For example, natural rubber (NR) having a polyisoprene structure, chemically synthesized isoprene rubber (IR) having the same polyisoprene structure as natural rubber, and ethylene having unsaturated bonds and capable of sulfur cross-linking - Propylene-diene terpolymer (EPDM), acrylonitrile-butadiene rubber (NBR) which is a copolymer of acrylonitrile and butadiene, liquid butadiene rubber (1,2-butadiene rubber, 1,4-butadiene rubber) ( BR), liquid isoprene rubber (1,4-isoprene rubber) (IR), liquid styrene-butadiene rubber (SBR), liquid polybutene (IM), and liquid urethane rubber (EU). These elastomers can be used as a single type of rubber, or as a blend of these rubbers in order to take advantage of the advantages of each rubber. Preferred vulcanizable elastomers are ethylene-propylene-diene terpolymers (EPDM).

As the filler, aromatic polyamide pulp fiber, aromatic polyamide fiber, carbon fiber, glass fiber, carbon black, asbestos, granular silica and the like are used. These may be used alone or in combination of two or more.

Flame retardants include antimony trioxide, zinc sulfide, phosphorus compounds, chlorine compounds, bromine compounds, metal hydroxides, and hydrated metal salts. Antimony trioxide is preferred, and antimony trioxide is particularly preferred. These may be used alone or in combination of two or more.

Other additives can optionally be added to the constituent materials of the insulator in order to perform various functions. For example, softeners and plasticizers to adjust the hardness of rubber products and improve kneadability and workability, anti-aging agents to prevent deterioration of rubber, kneading of rubber, workability during rolling, etc. There are processing aids and tackifiers to improve and obtain appropriate tackiness, and vulcanizing or cross-linking compounding agents to form chain rubber molecules into a three-dimensional structure. These additives can be used by appropriately selecting a combination of additives suitable for the elastomer or filler to be used and the manufacturing method of the rubber.

Mineral oil-based softeners and vegetable oil-based softeners can be used as softeners and plasticizers. Mineral oil softeners include, for example, paraffin softeners, aromatic softeners, and naphthenic softeners. Vegetable oil softeners include, for example, fatty acids such as stearic acid or salts thereof, rapeseed oil, and palm oil. , fatty oils such as coconut oil, pine oil, rosin, factice (sub) and the like.

As anti-aging agents, for example, amine-based anti-aging agents, phenol-based anti-aging agents, sulfur compounds, and phosphites can be used as secondary anti-aging agents.

Processing aids that can be used include stearic acid, metal salts of stearic acid, stearylamine, high-melting waxes, and low-molecular-weight polyethylene glycols.

As tackifiers, coumarone resins, phenols, terpene resins, petroleum hydrocarbon resins, rosin derivatives and the like can be used.

The total content of the vulcanizable elastomer and other additives is not particularly limited, but is preferably 30 to 90% by mass, more preferably 38 to 83% by mass, and still more preferably 46 to 76% by mass. is. In addition, the description of 〇〇 to XX in this specification indicates 〇〇 or more and XX or less unless otherwise specified.

The content of other additives contained in the insulator is not particularly limited, but is preferably 20% by mass or less, more preferably 2 to 12% by mass, and still more preferably 4 to 5% by mass.

The total content of the filler and flame retardant contained in the insulator is not particularly limited, but is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and still more preferably 20 to 50% by mass. be. If the total content of the filler and the flame retardant is 70% by mass or less, sufficient flexibility of the insulator 4 can be ensured. If the total content of the filler and the flame retardant is 10% by mass or more, the insulator 4 has sufficient rigidity and can withstand high pressure during propellant combustion.

As shown in FIGS. 3 and 5, the bottom wall 4b of the insulator 4 has an inner bottom surface 4c facing the bottom surface 5b of the propellant 5 and an outer bottom surface 4d facing the bottom wall 2b of the case body 2. As shown in FIG. The side wall 4a of the insulator 4 has an inner side surface 4e facing the outer lateral surface 5a of the propellant 5 and an outer side surface 4f facing the inner peripheral surface of the side peripheral wall 2a of the case body 2. As shown in FIG.

As shown in FIGS. 2, 3 and 5, the outer surface 4f of the side wall 4a of the insulator 4 has a case non-bonded area 6a and a case bonded area 6b. The case non-adhered region 6a is on the same circumference as the case adhered region 6b but is not adhered (the inner portion of the two-dot chain line in FIG. 2, the thick line portion in FIG. 5). The case non-bonded area 6a extends in the longitudinal direction (base axis direction) of the rocket motor 1 or the propellant 5. As shown in FIG. The length in the longitudinal direction of the case non-bonded region 6a extends substantially over the entire length of the propellant 5 in the longitudinal direction. The proportion of the case non-bonded region 6a to the outer circumference of the insulator is about 40° (see angle A in FIG. 5).

As shown in FIG. 3, the case bond region 6b has a longitudinally extending bond region 6c and an annular bond region 6d. When the insulator 4 is accommodated in the case body 2 , the longitudinally extending bonding region 6 c contacts and is bonded to the case body 2 . The longitudinally extending bonding region 6 c is adjacent to the case non-bonding region 6 a in the circumferential direction of the insulator 4 .

As shown in FIGS. 2 and 3, the annular bonding area 6d is on the same circumference as the longitudinally extending bonding area 6c. The tip of the annular bonding region 6d and the tip of the longitudinally extending bonding region 6c are positioned at substantially the same radial distance from the axial center of the insulator 4. As shown in FIG. The annular bonding region 6d extends along the longitudinal tip edge of the insulator 4 and has an annular shape. As a result, the annular bonding region 6 d extends annularly along the side peripheral wall 2 a of the case body 2 in the vicinity of the case lid 3 .

The propellant 5 shown in FIG. 3 is for propelling a rocket, and is formed from the propellant raw material 5d shown in FIG. An insulator 4 is installed in the case body 2, and the propellant raw material 5d is put into the insulator 4. As shown in FIG. As shown in FIG. 2, a propellant raw material 5d is filled in the insulator 4 and hardened through polymerization or the like to form a solid propellant 5. As shown in FIG. Propellant 5 is a composite propellant or a double base propellant.

If the propellant 5 shown in FIG. 3 is a composite propellant, the propellant raw material 5d contains, for example, polybutadiene and/or ammonium perchlorate. When propellant 5 is a composite modified double base propellant, propellant raw material 5d comprises nitrocellulose and/or urethane. The propellant feedstock 5d can also be an energetic polyurethane material including glycidyl azide polymer (GAP) and the like. As the propellant 5, it is preferable to use a composite propellant that is less susceptible to cracking even when contracted than the base propellant.

As shown in FIGS. 1 to 3, the propellant 5 is solidified within the insulator 4 to have a shape corresponding to the internal shape of the insulator 4 . That is, the propellant 5 has a cylindrical shape extending in the longitudinal direction. The outer lateral surface 5a of the propellant 5 adheres to the insulator adhesion region 4g (inner wall 4e) of the side wall 4a of the insulator 4. As shown in FIG. The bottom surface 5b of the propellant 5 is adhered to the inner bottom surface 4c of the bottom wall 4b of the insulator 4. As shown in FIG. That is, the entire outer peripheral surface of the propellant 5 is adhered to the inner peripheral surface of the insulator 4 . Thus, the insulator 4 has an inner peripheral surface facing the propellant 5 and an outer peripheral surface facing the motor case 1a. As shown in FIG. 6, the propellant 5 may shrink due to a decrease in temperature, and the insulator 4 deforms following the shrinkage of the propellant 5 . Specifically, when the propellant 5 contracts, the insulator 4 also deforms following the contraction of the propellant. At this time, a gap 6e is formed between the case non-bonded area 6a and the case body 2. As shown in FIG.

As described above, the rocket motor 1 has the case non-bonded area 6a where the insulator 4 is not bonded to the motor case 1a, as shown in FIGS. The case unbonded region 6a allows the insulator 4 to move with the propellant 5 relative to the motor case 1a. Therefore, the difference in thermal deformation between the motor case 1a and the propellant 5 caused by the difference in thermal expansion coefficient between the motor case 1a and the propellant 5 is absorbed by the case non-bonded area 6a.

As a result, the transfer of the external force to the propellant 5 caused by the difference in thermal deformation is reduced. By reducing the external force, the propellant 5 is suppressed from coming off the insulator 4 . Alternatively, the occurrence of cracks inside the insulator 4 due to thermal contraction can also be suppressed. By suppressing the propellant 5 from peeling off from the insulator 4 or the propellant 5 from cracking, so-called burst can be suppressed.

Moreover, as shown in FIG. 3, the heat insulating structure provided between the motor case 1a and the propellant 5 is a single layer structure composed of the insulator 4. As shown in FIG. On the other hand, the heat insulation structure of the conventional rocket motor 11 shown in FIG. Therefore, by making the insulator 4 thinner, the inner diameter of the heat insulating structure (insulator 4) is increased, and the amount of the propellant 5 can be increased. Also, the number of parts of the heat insulating structure of the rocket motor 1 is reduced.

As shown in FIG. 3, the case unbonded region 6a is formed over substantially the entire length of the propellant 5 in the longitudinal direction. Therefore, the case non-bonded area 6a allows the propellant 5 to move with respect to the motor case 1a over substantially the entire length of the propellant 5 in the longitudinal direction. As a result, the difference in thermal deformation between the propellant 5 and the motor case 1a is absorbed over the entire length of the propellant 5 in the longitudinal direction. Thus, separation of the propellant 5 from the insulator 4 and occurrence of cracks inside the propellant 5 can be more effectively suppressed.

As shown in FIGS. 3 and 5, the case adhesive region 6b has a longitudinally extending adhesive region 6c adjacent to the case non-bonded region 6a in the circumferential direction and extending in the longitudinal direction of the propellant 5. As shown in FIG. Therefore, the insulator 4 holds the propellant 5 by the case adhesion area 6b. For example, the case adhesion region 6b can suppress the propellant 5 from rotating in the circumferential direction with respect to the insulator 4 .

As shown in FIGS. 3 and 4, the case adhesive area 6b further has an annular adhesive area 6d. Therefore, as shown in FIG. 7, the annular adhesion region 6d can suppress combustion gas from entering between the motor case 1a and the insulator 4. As shown in FIG. Therefore, it is possible to suppress the melting of the inner peripheral surface of the motor case 1a by the high-temperature combustion gas G.

As shown in FIG. 3, the combustion end face 5c is formed at a position farther from the nozzle 3b of the case lid 3 than the annular adhesion region 6d of the insulator 4 is. That is, the annular adhesion region 6d is formed at a position closer to the nozzle 3b than the combustion end face 5c. Therefore, the annular adhesion region 6d prevents combustion gas from entering between the motor case 1a and the insulator 4 at a location closer to the nozzle 3b than the combustion end surface 5c of the propellant 5. As a result, the melting of the inner peripheral surface of the motor case 1a can be suppressed more reliably.

The motor case 1a does not need to have the cylindrical shape shown in FIGS. 1 to 3, and may have, for example, a polygonal tubular shape. The shape of the case lid 3 can also be changed into various shapes according to the shape of the motor case 1a.

Rocket motor 1 may have insulator 7 shown in FIG. 8 instead of insulator 4 shown in FIG. The outer shape of the insulator 7 is substantially the same as the outer shape of the insulator 4, but has a case non-bonded region 8a instead of the case non-bonded region 6a. The length of the case non-adhesive region 8a is set to be half or less of the total length of the propellant in the longitudinal direction of the propellant 5 . That is, the annular adhesive region 8d has a relatively short width in the longitudinal direction. Conversely, the length in the longitudinal direction of the case non-bonded region 8a is longer than that of the longitudinally extending bonded region 6c. Therefore, the case unbonded region 8a can reliably allow the insulator 7 to move together with the propellant 5 with respect to the motor case 1a.

Although the case bonding area 6b in the rocket motor 1 described above has the annular bonding area 6d, the annular bonding area 6d may not exist and only the longitudinally extending bonding area 6c may exist.

The case unbonded region 6a is formed over substantially the entire length of the propellant 5 in the longitudinal direction. It can be shorter, longer, or shorter.

Further, in the rocket motor 1 described above, the number of case non-bonded areas 6a is three as shown in FIG. Although the proportion of the case non-bonded region 6a to the outer circumference of the insulator is about 40° (angle A in FIG. 5), it can be about 30 to 90°. The total range of the non-bonded region of the case on the outer circumference of the insulator can be set to about 90° to 180°. Within this range, peeling of the propellant from the insulator and cracking of the propellant can be sufficiently suppressed without reducing the adhesion of the insulator to the motor case.

The case non-adhered region 6a is a portion not adhered to the motor case 1a, but can be formed by, for example, not applying adhesive when the case and insulator are adhered, or by applying a release agent.

In the rocket motor 1, the case bonding area 6b has the annular bonding area 6d formed along the entire circumferential direction of the inner peripheral surface of the motor case. % or more, and can be formed in a C shape with a slight gap.

In the rocket motor 1, the annular adhesion region 6d is formed at a position closer to the nozzle 3b than the combustion end face 5c of the propellant 5, but the combustion end face 5c and the annular adhesion region 6d may be at the same position. .

1 Rocket motor 1a Motor case 4 Insulator 4g Insulator adhesion area 5 Propellant 5c Combustion end faces 6a, 8a Case non-adhesion area 6b Case adhesion area 6c Longitudinal extension adhesion area 6d, 8b Annular adhesion area

Claims (5)

A rocket motor,
a propellant for propelling the rocket;
a motor case containing the propellant and having a nozzle at one end;
a single-layer insulator having an inner peripheral surface facing the propellant and an outer peripheral surface facing the motor case;
The inner peripheral surface and the outer peripheral surface of the insulator are both cylindrical and have a curvature that curves radially outward over the entire circumference,
The inner peripheral surface of the insulator has an insulator adhesion region that is directly adhered to the entire outer peripheral surface of the propellant,
The outer peripheral surface of the insulator has a case-bonded region that is directly bonded to the inner peripheral surface of the motor case and a case-unbonded region that is not bonded to the inner peripheral surface of the motor case,
the propellant charge has a combustion end facing the nozzle and extends longitudinally;
The rocket motor, wherein the case unbonded region is formed over substantially the entire length of the propellant in the longitudinal direction.

A rocket motor according to claim 1, comprising:
The rocket motor, wherein the case bond region has a longitudinally extending bond region circumferentially adjacent to the case non-bond region and extending in the longitudinal direction of the propellant charge. A rocket motor according to claim 2, wherein
The rocket motor, wherein the case bonding area has an annular bonding area formed along the entire circumferential direction of the inner peripheral surface of the motor case. A rocket motor according to claim 3, wherein
A rocket motor, wherein the annular adhesion region is formed at a position closer to the nozzle than the combustion end face of the propellant. A rocket motor according to claim 3 or 4,
A rocket motor, wherein the annular adhesive region has a width in the longitudinal direction of the propellant charge that is less than or equal to one-half the total length of the propellant charge.

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