DE2633611A1 - PROCEDURE FOR NON-DESTRUCTIVE TESTING OF SOLID MISSILE FUEL ENGINES - Google Patents

Description

263361Ί

BAYERN-CHEMIE * &' Aschau _for July 26th, 1976

Aero-chemical propulsion company Pat / Dr.D / My with restricted inmate Case 392

Method for the non-destructive testing of solid rocket propellants

The invention relates to a method for non-destructive Testing of solid rocket propellants.

Errors can occur in the manufacture of solid propellant rocket engines and their introduction into the combustion chamber. which result in uncontrolled burn-up or decomposition. Therefore one has non-destructive testing methods for Quality control used, which guarantee a clear error detection, suitable for as many types of errors as possible and enable economical work.

Materials testing using X-rays has served as the standard procedure up to now. For some time now, too Microwaves, infrared light and ultrasound are used. These newer methods allow a high degree of automation to, but require a relatively large amount of equipment and therefore cause high material costs. Sensitivity too this procedure against various types of errors is not yet sufficiently secured.

The individual examination by means of X-rays requires little time at low cost. However, it proves to be disadvantageous the poor detection of various errors, such as detachments in the combustion chamber, which only have a very thin air gap between insulation / chamber wall or insulation / fuel. Such errors are particularly special undesirable.

The invention has the object of avoiding the disadvantages described and a safe and easy to implement

709885/0127

26336 1!

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Process that guarantees results and operates economically to propose. Here a method is used which is already known under the name "Thermography" in other technical and medical fields.

According to the invention, the object is achieved by so-called. Liquid crystals as indicators for defects on the with a light-absorbing underground provided engine are applied, the engine to a temperature below the mesophase of the liquid crystals is set and then uniformly heated to the temperature of the mesophase. as Indicator, a substance is used that forms a mesophase within a defined temperature range, which represents a liquid-crystalline state. The substance, which is colorless or only slightly colored in the liquid or solid state, appears colored and changes its color sensitively with temperature over the entire visible spectral range. The reflection colors that occur are only then clear to recognize when there is no additional reflection of the incident Light takes place through the subsurface; this is prevented by a light-absorbing layer. The relationship between Temperature and color are used in the suggested test. The engine to be examined is equipped with a suitable Provide a light-absorbing surface and then apply the indicator, e.g. using a spray gun. The indicator can be in the form of a solution, suspension or in a microencapsulated state. The engine is then brought to a temperature set below the mesophase, i.e. normally cooled, and then evenly heated on one side, whereby im A heat flow is created inside the engine. Is the test body homogeneous, then the heat flow is also uniform regardless of location and accordingly also the temperature on the Surface. If the rocket solid propellant motor contains defects, the heat dissipates differently and creates a corresponding temperature distribution on the surface. Is the

709885/0127

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Surface temperature in the area of the mesophase of the indicator, the temperature field appears as a color pattern Defect in the engine can be located.

Derivatives of cholesterol or mixtures thereof are preferably used as indicators. Their mesophases should generally encompass a color change range from 4 to 6 ^{° C.}

In a further embodiment of the invention, liquid crystals are used with mesophase within a range of 19-40 ⁰ C, preferably those whose color change is taking place from 31 to 35 ° C. With the new method, large-area defects can be identified particularly clearly. The cost of the procedure is no greater than that of the previous standard procedure of examination using X-rays.

The following exemplary embodiment is intended to illustrate the invention.

An intentional detachment between the chamber wall and the insulation of the solid propellant rocket engine, approximately 30 cm in length, is worked into an engine. The combustion chamber is first painted black and a 25% solution of microencapsulated liquid crystals of a cholesterol derivative, the liquid-crystalline range of which is between 31 and 35 ^° C., is applied to the paint layer with a spray gun. It is then cooled the engine to +5 ⁰ C, and then heated on a hot stage while rotating, to the color range of the indicator is reached. The incorporated detachment can be clearly seen as a colored spot in the black area. This error cannot be determined in a comparison test using an X-ray examination.

709885/0127

ORIGINAL INSPECTED

Claims (2)

Aschau, July 26, 1976 claims 1. Procedure for the non-destructive testing of solid rocket propellants, characterized in that liquid crystals as an indicator for defects be applied to the engine, which is provided with a light-absorbing substrate, the engine to a temperature set below the mesophase of the liquid crystals and then uniformly to the temperature of the mesophase is heated. 2. The method according to claim 1,
characterized, that liquid crystals with mesophases within a range from 19 to 40 ⁰ C are used, preferably those whose color change takes place between 31 and 35 ⁰ C. 709885/0127 ORIGINAL INSPECTED