JPH0441964A - Double thrust solid rocket motor - Google Patents

Abstract

PURPOSE:To obtain a double thrust rocket motor having high reliability with the same manufacturing process as that for a single thrust rocket motor by arranging a cylindrical and metal permiable forming member as an inner layer of an inner combustion type propellant. CONSTITUTION:A one-chamber two-layer double thrust solid rocket motor is provided with at least a propellant 1, a metal permeable foaming member 2, an ignitor 3, a rocket motor combustion chamber 4, and a resctictor 5. For manufacturing, the metal peamiable forming member 6 which has a space on its center of a cross-sectional face, a metal die 8 which has the same cross-sectional shape and made of aluminum or the like is fitted to the space 7, to form a propellant charging molding core. The above-mentioned molding core is arranged on a center of a rocket motor combustion chamber 9. After the slurrey of the propellant 1 is charged and heated for hardening, the aluminum metal die is drawn. End parts are treated by the restrictor 5, and the manufacturing is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single-chamber, two-layer, two-stage thrust solid rocket motor that exhibits a large thrust at the time of takeoff and maintains a low thrust thereafter.

[Problems to be solved by conventional technology and the invention] Rocket motors generate large thrust in the initial stage (boost period) for the purpose of increasing flight stability during takeoff, and then generate a low thrust cruise (
There are systems that add a booster auxiliary rocket to the outside of the cruise rocket in order to perform (sustainer stage), systems that maintain a high-thrust booster rocket motor and a small-thrust sustainer rocket motor in series, etc. The structure is complicated, large and expensive.

On the other hand, a two-stage thrust solid rocket motor, which has a single combustion chamber and two internal internal combustion propellant layers, with a high combustion velocity propellant in the inner layer and a low combustion velocity propellant in the outer layer, is simple. Although they are small and inexpensive, high-flame propellants have fine solid oxidizer particles and a large amount of solid oxidizer, and also contain a large amount of high-flame catalysts, which reduces their mechanical strength and causes the inner surface to deteriorate at low temperatures. This generates large tensile stress, which causes fatal crack defects in the propellant. In addition, in the manufacturing process, the cylinder of high-flame propellant that will become the inner layer is hardened and molded in advance, and this is placed in the center of the rocket motor combustion chamber, and the outer layer is placed between the outside and the inner wall of the combustion chamber. After injecting a low-burning propellant, it is hardened and molded, which doubles the manufacturing process. Furthermore, there is a risk that the propellant between the inner and outer layers will separate, and advanced techniques are required to maintain the adhesive force between the two layers.

An object of the present invention is to obtain a highly reliable two-stage thrust rocket motor using almost the same manufacturing process as a single-stage thrust rocket motor.

[Means to solve the problem]

The present inventors have completed the present invention as a result of intensive studies to achieve the above object.

That is, the present invention provides a one-chamber, two-layer, two-stage thrust solid rocket motor characterized in that a cylindrical metal breathable foam is disposed as an inner layer of an internal combustion propellant. This is what we provide.

In the present invention, only one type of propellant can be used as the internal combustion propellant, and there is no need to intentionally use a high-burning-speed propellant; instead, a cylindrical, metal, breathable foam is used as the inner layer of the propellant in the center of the combustion chamber. Two-stage thrust can be obtained by simply arranging the propellant, and even when exposed to low temperatures, the inner surface of the propellant does not crack, improving environmental resistance. Of course, if it is necessary to increase the thrust ratio between the booster stage and the sustainer stage, a high combustion rate propellant can be used as the inner layer propellant of the internal combustion type propellant. The foam also has the effect of preventing cracks from forming on the inner surface of the propellant at low temperatures.

To explain the details of the present invention with reference to the drawings, FIG. 1 is a schematic cross-sectional view of a one-chamber, two-layer, two-stage thrust solid rocket motor according to the present invention, and FIG. It is. In FIG. 1, 1 is a propellant, 2 is a metal breathable foam, 3 is an igniter, 4 is a rocket motor combustion chamber, and 5 is a rest lifter.

To explain the manufacturing method of the rocket motor according to the present invention,
A metal breathable foam 6 having a beam-shaped space in the center of its cross section as shown in FIG. 3 is prepared in advance, and a metal such as aluminum as shown in FIG. A metal mold 8 having the same cross-sectional shape is fitted to form a propellant casting core. An example of the breathability of the metal foam used is:
Thickness: 1 cm, average pore diameter: 3.2 mm, air flow rate: 2 m/s
ec, the pressure loss is about 7 mmt1g.

As the pore size increases, pressure loss decreases, air permeability improves, and propellant castability improves. As the metal constituting the foam, aluminum and silver are preferable, and the material of the aluminum is pure aluminum, A6101. A10
Aluminum alloys such as 70, AC2A, AC4C)I can also be used. The apparent density of metal foam is 0.05g/c
sff, and its thermal conductivity is about twice that of copper by weight. A high thrust ratio during the booster and sustainer phases can be achieved by reducing the thickness of the metal cell walls or by using silver, which has a higher thermal conductivity.

The above-mentioned casting core is installed in the center of the rocket motor combustion chamber 9 in FIG. The end portion is finished with a rest lifter 5 to complete manufacturing.

When a rocket motor manufactured in this manner is combusted using an ignition signal using the normal method, the flame from the igniter ignites the inner surface of the propellant, but the inner layer from the inner surface of the propellant contains aluminum, silver, etc. with high thermal conductivity. A metal breathable foam is present, and the metal foil on the foam wall is in contact with the metal foam wall to rapidly transfer heat from the combustion zone in the direction of combustion of the propellant. The temperature increases, the burn rate increases, and the result is that the overall propellant containing the metal foam burns several times faster than one without the metal foam.

The use of silver wire or honeycombs has been proposed as a method to increase the burning speed of propellant by utilizing heat conduction in metals, but these methods are only applicable to end-face combustion, or the materials are too soft. For this reason, it was difficult to maintain a certain shape. Furthermore, the method of kneading metal foil pieces into the propellant in advance had many problems with casting and poor reproducibility.

On the other hand, since the metal foam used in the present invention has polygonal pores, it is three-dimensionally isotropic and has high rigidity, so it can be processed into any shape, and it can be processed into any shape other than the internal combustion method. It can also be applied to end-face combustion methods.

〔Example〕

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

As shown in FIG. 3, a cylindrical aluminum metal breathable foam (average pore diameter 6.4 +++ m) with an outer diameter of 6CI11 and a length of 20 cm, which has a beam-shaped space in the center, has a beam-shaped space 7. The aluminum metal mold 8 shown in Fig. 4 was fitted into the core, and placed in the center of a cylindrical rocket motor combustion chamber with an inner diameter of 8 cm and a parallel length of 20 cm. After casting the ammonium perchlorate-polybutadiene propellant slurry and curing it by heating at 65°C for 3 days, the center aluminum metal mold was pulled out and both ends of the core were restlifted with a heat-resistant material to create the rocket of the present invention. Completed motor manufacturing.

As a comparative example, an ammonium perchlorate-polybutadiene propellant with a viscosity of 12 kpoise and a burning rate of 25+++ w/sec was used, and a cylindrical booster propellant with an outer diameter of 6 cm and a length of 20 cm had a halo-shaped space in the center. was manufactured in advance and used as a casting core with the aluminum metal mold attached, and the inner diameter was 8ca+ and the parallel length was 20c+e.
An ammonium perchlorate-polybutadiene propellant with a viscosity of 2 kilovoids and a combustion speed of 7 mm/sec is installed as a sustainer propellant between the outside of the cast core and the combustion chamber wall. After casting the slurry and curing it by heating at 65°C for 3 days, the core was extracted and both ends were treated with a heat-resistant material to create a comparative rocket motor.

The rocket motor of the present invention and the rocket motor for comparison
After controlling the temperature to 0''C, we performed a vibration test at -60℃, and found that the comparative rocket motor had cracks along the motor shaft at the bottom of the inner halo-shaped space, indicating the risk of explosion. , it could not be subjected to a combustion test.

The rocket motor of the present invention showed no abnormalities in internal visual inspection and non-destructive inspection using X-rays, so after attaching an igniter and adjusting the temperature to -60°C, it was attached to a combustion stand and a combustion test was performed. A thrust of 292 kg was generated for 0.61 seconds during the booster phase, and a thrust of 97.4 kg was sustained for 1.83 seconds during the sustain phase, indicating normal two-stage thrust combustion.

〔Effect of the invention〕

As shown in the examples, conventional two-stage thrust solid rocket motors require multiple manufacturing steps, and cracks occur in the inner surface of the propellant due to insufficient strength in low-temperature environments, making them unusable.

On the other hand, the rocket motor of the present invention requires only one propellant casting process, which simplifies manufacturing and allows the rocket motor to operate at -60°C.
It can withstand low-temperature environments, exhibits normal combustion, and exhibits excellent performance.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of a rocket motor of the present invention, Fig. 2 is a schematic cross-sectional view of the rocket motor of the present invention in a direction perpendicular to the body, and Fig. 3 is a perspective view of a metal foam used in the present invention. , FIG. 4 is a perspective view of the metal mold, and FIG. 5 is a schematic cross-sectional view showing the rocket motor during the manufacturing process. 1... Propellant 2.6... Metal foam 3... Igniter 4.9... Combustion chamber 5... Restlift tough... Beam shaped space 8... Metal type

Claims (1)

[Scope of Claims] 1. A two-stage thrust solid rocket motor, characterized in that a cylindrical metal breathable foam is disposed as an inner layer of an internal combustion propellant in a one-chamber, two-layer, two-stage thrust solid rocket motor. motor. 2. The two-stage thrust solid rocket motor according to claim 1, wherein the metal breathable foam is made of aluminum or silver.