JPH01159451A - Manufacture of end combustion type rocket motor by direct filling system - Google Patents

Abstract

PURPOSE:To keep off any deflection in a propellant based on a difference between a motor case and a thermal expansion characteristic of this propellant by inserting a deformable insulator, installing an angular projection on an inner surface in the axial direction, into the motor case, and making it partially contact with the case at a projection back part. CONSTITUTION:In an end combustion type rocket motor, a deformable insulator 8, formed with an angular projection 9 describing a smooth cirve on the inner surface in the axial direction of the rocket motor, is inserted into a motor case 1. Then, this insulator 8 is made partially contact with the motor case 1 at a projection back part, and a propellant is filled up in this insulator 8. The said projection 9 is installed for easing an concentrated stress when this concentrated stress due to contraction of the propellant has occurred in a bonded part terminal between the motor case 1 and the insulator 8, and bottom length (b) of this projection 9 should be larger than bonding line length (a) in the circumferential direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing an end-burning rocket motor manufactured by a direct loading method.

[Prior Art] In general, a rocket motor has a propellant 2 placed in a motor case 1 as shown in FIG. It's gaining thrust. This thrust is determined by the amount of gas emitted from the nozzle per unit time, which is equal to the amount of propellant burned per unit time, and the thrust is controlled by the amount of propellant burned, that is, the product of the burning area and burning speed. By controlling the Therefore, in order to obtain a large thrust, it is necessary to install the bar 1 with a large product of combustion area and combustion speed. In order to increase the combustion area, the shape is generally called an internal combustion type, that is, a hole is provided in the center of the propellant 2, as shown in FIG. 6, and the surface area of the hole is increased. However, in this case, since the holes are essential, the propellant filling rate inevitably decreases, and is limited to about 88%. In order to improve this point, in recent years research has been carried out on so-called end-burning type rocket motors, as shown in Figure 7, in which a propellant with a high burning speed is made and the propellant is burnt from the end face without providing a hole in the propellant. In this end-burning rocket motor, the filling rate is 90.
% or more, but because the thermal expansion coefficients of the propellant and motor case are different and they are packed tightly, cracks may occur due to thermal stress, especially at low temperatures, and the rocket motor may explode during combustion. Therefore, this thermal stress must be alleviated.

For this reason, a so-called free-standing method was used in which the motor case and propellant were not glued together at all, in other words, the propellant with side restrictive toughness was separately manufactured and later assembled into the motor case. Normally, as shown in FIG. 7, the motor case 1 needs to have an inner surface protrusion at both ends or one end thereof to attach a rear or front mirror plate 3.6 with screws or the like.

If this protrusion exists, only a propellant with a diameter smaller than the protrusion can enter, and the rocket motor will have many gaps, making it impossible to fill it with a large amount of propellant. In order to improve this, it was considered to apply the so-called direct loading method to this edge-burning rocket motor, in which the insulator is directly glued to the motor case and the propellant is poured and hardened afterwards.
Because the thermal expansion characteristics of the motor case and the propellant are different, at low temperatures, thermal stress causes separation between the motor case and the propellant, resulting in combustion abnormalities. Furthermore, when assembling the propellant into the motor case, if the propellant length is long, the propellant may deflect and cause defects in the propellant, or if there are irregularities on the sides, it may be difficult to assemble the propellant, which may require modification. Met.

[Problems to be Solved by the Invention] The present invention provides an end-burning rocket motor that prevents deflection of the propellant due to the difference in thermal expansion characteristics between the motor case and the propellant, and has a large propellant filling rate. This is what I am trying to do.

[Means for Solving the Problems] That is, the present invention provides an edge-burning rocket motor in which a deformable insulator having a chevron-shaped protrusion drawing a smooth curve on the inner surface in the direction of the axis of the rocket motor is placed inside the motor case. Insert it, and at the back of the protrusion,
The present invention relates to a method for manufacturing an edge-burning rocket motor using a direct loading method, which is characterized by partially adhering to a motor case and filling the inside of this insulator with propellant.

Although the insulator in the present invention is partially bonded in the axial direction of the rocket motor, it is preferable that the bonding between the motor case and the insulator be uniform to avoid applying an asymmetrical force to the propellant. The number of bonding points may be one or more as shown in Figure 1, preferably multiple to disperse stress, and more preferably as shown in Figures 2-a and 3-a. Odd numbers are good because the propellant contraction positions are not opposed to each other. In addition, the adhesive ratio to the circumference must be such that the propellant can be held sufficiently against the acceleration applied to the rocket motor, but since the thermal expansion coefficients of the motor case and the propellant are different, when the temperature is lowered, the adhesive interface Since a very large stress is applied, it is preferable that the ratio of the bonded area is 50% or less. Further, it is necessary to adopt a structure that allows combustion gas to enter the unbonded portion. Further, the insulator of the present invention may be further bonded to a motor case in which an insulator material is bonded to the entire inside of the motor case to protect the motor case. In addition, the protrusion 9 of the insulator is provided to relieve the concentrated stress that occurs at the end of the bond between the motor case and the insulator due to contraction of the propellant, as shown in Figure 2-b. , the bottom length of the projection 9 needs to be larger than the adhesive line length a in the circumferential direction. Furthermore, the number of protrusions may be one or more as shown in Figures 1 to 3-b, for example. At this time, if the radii r1 to r3 of the constituent arcs are small, stress will be concentrated there, and if the radius is less than 2 mm, the stress will be very large, so the radius is preferably 2 mm or more. In addition, the upper limit can be selected depending on the height C of the protrusion and the filling rate of the propellant.The material of this insulator bonding part is not particularly limited, but it must be able to deform freely to relieve thermal stress, so it may be made of plastic or rubber. is preferred. In addition, since the edge-burning type rocket motor is subject to ablation by high-temperature combustion gas for a long period of time, especially on the rear end plate side, it is preferable to use a material that can withstand this ablation. For example, there is a method of using plastic, rubber, or the like containing a heat reducing agent such as magnesium carbonate or a heat resisting agent such as asbestos as a filler for the adhesive portion.

When manufacturing this insulator, a mold is generally used. Since an insulator containing such a filler has low fluidity, it may be difficult to form a target protrusion shape. In this case, since this protrusion does not play the role of an insulator, it may be replaced with highly fluid rubber. In addition, the thickness of the insulator depends on the combustion flame temperature, gas flow rate,
It is necessary to decide based on combustion time, etc. In the case of an end-burning rocket motor, the insulator on the rear head plate side is exposed to flame for a longer time than the front head plate side, so it should be made thicker, and the insulator should be made thicker to provide scent from the front head plate side to the rear head plate side to increase the filling rate. Can be done. As a method of partially adhering this insulator to the motor case, there is a method of applying a release material to the non-adhered parts of the insulator or motor case, applying adhesive to the adhering parts, and applying pressure with an air bag or the like to adhere the parts.

The feature of the present invention is that the motor case and the insulator are partially bonded in the axial direction, and the propellant is prevented from cracking due to concentrated stress, and there are no particular restrictions on the structure of the parts that are not bonded. For example, the fourth
Hard FRPII or the like may also be used as shown in figure -a.

Further, the propellant may be any propellant that can be generally used for direct loading. Examples include composite propellants such as CTPB series and HTPB series, double base propellants, and composite double base propellants.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 The materials used and test conditions for the specimen are as follows.

First, the motor case has an outer diameter of 216 mm and an inner diameter of 200 mm.
The total length of the insulator is 120 mm as shown in Figure 5.
The thickness was 1 mm on the front end plate side and 3.5 mm on the rear end plate side, and the protrusion structure was as shown in Figures 2-a and 2-b.

The material of the insulator was EPDM (ethylene propylene rubber). Furthermore, the adhesive between the motor case and the insulator was a urethane adhesive. The length a of the adhesive line between the motor case and insulator is 13 mm at each location.
The protrusion has a height C of 7 mm, a peak radius r1 of 7 mm, a base radius r2 of 45 mm, and a base length of 2.
It was set to 6 mm.

Propellant: 13% binder, 70% ammonium perchlorate
, an HTPB-based composite propellant containing 17% aluminum powder.

MIL-3 was applied to this specimen in the range of -30''C to 40'C.
3 cycles of temperature cycles according to TD-810G, then low temperature (turbulence) according to the conditions of MI L-8TD-810 at -30°C.
A combustion test was conducted.

Example 2 The materials used and test conditions for the specimen were the same as in Example 1, the cross section of the insulator was as shown in Figures 3-a and 3-b, and the adhesive line length a was 20 mm at each location. , the height C of the protrusion is 5 mm, and the radius r1 of the peak and base.
, r2 is 5mm, rx is 5mm, base length is 4om
And so.

Example 3 Same as Example 2. However, the adhesive line length a of the insulator was 52 mm at each location, and the base length of the protrusion was 72 mm.

Comparative Examples 1 to 3 In Comparative Examples 1 and 2, the motor case and the insulator were bonded over the entire surface, and in Comparative Example 2, the same protrusion as in Example 1 was provided. In Comparative Example 3, no protrusion was provided, and the adhesive portion a between the motor case and the insulator was the same as in Example 1.

Table 1 shows the test results for the above examples.

Table 1 1: Cracks were observed in the insulator and propellant from 1/3 to 172 laps over the entire length of the propeller.

[Effects of the Invention] It has been found that the direct injection type end-face combustion rocket motor of the present invention has the following effects.

1) It is possible to increase the propellant filling rate. In this embodiment, the ratio was approximately 86% in the conventional method, whereas it was approximately 96% in the method of the present invention.

2) A rocket motor with such a high filling rate has large thermal stress, and comparative examples other than those of the present invention cracked during temperature cycling and were unusable, but the product of the present invention had no defects and was superior to conventional products. It was found that the filling rate could be improved by about 10%.

3) Since cracks appeared in the comparative example during temperature cycling, we photographed only the inventive product at low temperatures, where the thermal stress is the most severe, and the results were also good with no abnormalities observed. found.

[Brief explanation of the drawing]

1 to 4-b are cross-sectional views of the insulator of the present invention, and FIG. 5 is a vertical cross-sectional view thereof. Figures 6.7 are schematic diagrams of conventional internal combustion and edge combustion rocket motors, respectively. 1... Motor case or motor case with insulator material, 2... Propellant, 3... Rear head plate, 4... Nozzle,
5... Igniter, 6... Front end plate, 7... Side rest lifter, 8... Insulator, 9... Projection, 10...
Adhesive part between motor case and insulator, 11...FRPo Patent applicant Director of Technology Research Headquarters, Agency of Defense (and 2 others)

Claims (1)

[Claims] In an edge-burning rocket motor, a deformable insulator having a chevron-shaped protrusion drawing a smooth curve on the inner surface in the axial direction of the rocket motor is inserted into the motor case, and a portion A method for manufacturing an edge-burning rocket motor using a direct loading method, which is characterized by adhesively bonding the insulator to a motor case and filling the inside of the insulator with propellant.