RU2267837C1 - Antenna fairing of rocket - Google Patents

Abstract

FIELD: rocketry, in particular, structures of antenna fairing of rockets with radar control system.

SUBSTANCE: the claimed antenna fairing has a radio transparent shell of porous quartz ceramics, whose inner side has a layer of ceramics with polymer introduced in the pores, and a moisture-resistant coating applied onto the outer surface. The shell represents a half-wave structure with annular trapezoidal channels having a depth of 0.003-0.01 of the operating antenna wavelength, the inner layer of ceramics with polymer has a thickness of 0.02-0.05 of the total thickness of the shell wall, and the carried-away moisture-resistant coating is applied onto the porous shell preliminarily blocked by acetone and has a thickness within 50 to 80μm. The ceramic shell is made of quartz ceramics with a porosity of 8.5 to 10.5%, bending strength of at least 50 Mpa, thermal conductivity not exceeding 1.3 W/mK, spread of values of dielectric permittivity in the shell radio transparent zone not exceeding 1%, and from shell to shell not exceeding 3%.

EFFECT: enhanced thermal stability and improved radio engineering characteristics at provision of the shell carrying capacity and moisture resistance.

2 cl, 1 dwg

Description

The invention relates to rocket technology, and more specifically to the design of antenna fairings with a radar control system made of quartz ceramics. It can be widely used to create missiles for various purposes.

It is known that antenna fairings made of quartz ceramics are one of the most promising due to such material properties as high heat resistance, low thermal conductivity, small size and stability of dielectric characteristics (ε and tqδ) in a wide range of temperatures and frequencies. However, low strength and open porosity of the material requires special measures to eliminate this drawback.

Known design of the antenna fairing, RF patent No. 2090956, IPC H 01 Q 1/42, 1994, containing a shell of quartz ceramics, transitional and docking frames, characterized in that the transitional frame is made of Invar, and the ceramic shell of the fairing is attached to it through a layer of sealant. The performance of the fairing during heating is ensured due to the proximity of the thermal expansion coefficients of quartz ceramics and Invar, as well as the elastic "floating" connection of the shell with the frame using a layer of sealant. However, the absence of sealing elements and hardening of the porous ceramic shell in the fairing design reduces the operational characteristics of the fairing. The closest technical solution is the rocket antenna fairing according to the patent of the Russian Federation No. 2209494, IPC H 01 Q 1/42 dated 07/27/2003, in which the ceramic shell of porous quartz ceramics consists of a radio-transparent internal power element with a polymer introduced into the pores of the ceramic and an external a heat-protective element made of porous quartz ceramics, the thickness of the internal strength element being 0.05-0.1 of the total wall thickness of the shell or evenly increasing from the toe to the base to a value corresponding to 0.1-0.9 of the total thickness s, and the thickness of the outer heat shield element varies inversely with preservation of the overall electrical wall thickness, wherein the outer surface of the heat shield element applied moisture barrier. The advantage of this design is that it provides for hardening and sealing of the porous ceramic shell, which increased the carrying capacity of the fairing made of quartz ceramics and ensured its moisture resistance.

The disadvantages of the prototype are:

- Introduction into the pores of the ceramic shell of the polymer to a depth of 0.9 of the total wall thickness worsens the high-temperature properties of the material. Pyrolysis of an organic polymer inside the wall without oxygen access during high-speed heating of the shell not only affects the dielectric characteristics of the fairing material, but can lead to its destruction. This is also facilitated by the absence of restrictions on the porosity and thermal conductivity of quartz ceramics in the shell.

- Due to the fact that the polymer introduced into the pores increases the dielectric constant of quartz ceramics by about 10%, and the thickness of the impregnated layer is significant and variable, the radio cone of the fairing is complicated, there is a need for individual radio conduction of the products after impregnation.

- The absence of restrictions on the external moisture-proof coating in terms of its thickness, and measures to prevent absorption of the coating material into the pores of the ceramic, worsen the radio characteristics of the fairing. In the case of applied coatings, the absorption of organic enamel by porous ceramics is unacceptable, since its thermal degradation during heating with the formation of carbon in the pores of the shell material can cause a sharp decrease in radar transparency of the fairing.

The noted shortcomings significantly worsen the technical characteristics of quartz ceramic fairings in terms of thermal stability and radio technical characteristics, and narrow the scope of fairings.

The objective of the invention is to increase the technical characteristics of the antenna fairings made of quartz ceramics under conditions of high-temperature heating and, in particular, to increase thermal stability, improve radio-technical characteristics while ensuring the necessary bearing capacity of the ceramic shell and moisture resistance. This is important, first of all, for high-speed missiles operating at speeds of 8-12 M.

This object is achieved in that the antenna cowl, comprising a radiolucent sheath of porous quartz ceramics, on the inside of which contains a layer of ceramic with a polymer introduced into the pores, and a moisture-proof coating is applied on the outer surface, characterized in that the shell is a half-wave design with ring trapezoidal grooves with a depth of 0.003-0.01 of the working wavelength of the antenna, the inner layer of ceramic with polymer has a thickness of 0.02-0.05 of the total shell wall thickness, and gozaschitnoe coating is applied to the pre-blocked with acetone porous coating and has a thickness of 50-80 microns.

The ceramic shell is made of quartz ceramics with porosity of 8.5-10.5%, bending strength of at least 50 MPa, thermal conductivity of not more than 1.3 W / m · K, the spread of dielectric constant in the radiolucent zone of the shell is not more than 1% , and from shell to shell - not more than 3%.

In the claimed technical solution, the high technical characteristics of the fairing during operation in a wide temperature range (from -60 ° C to + 1800 ° C on the surface) are achieved by choosing the design and properties of the shell material, eliminating the deep impregnation of the porous ceramic shell with polymer, and applying a moisture-proof coating onto a porous membrane previously blocked with acetone.

The authors performed heat-strength calculations, bench tests, and natural tests showed that half-wave fairings made of quartz ceramics with the indicated strength and thermophysical properties ensure the shell's resistance to the effects of the required heat and power loads without additional hardening. This is due to the fact that during high-temperature heating (above 900 ° C) in a material optimized by properties and production technology, the effect of stress relaxation arises and the high-temperature strength of the material increases. So, if at room temperature the flexural strength of quartz ceramics TU 1-596-195-84 with a porosity of 8.5-10.5% is 50-85 MPa, then at a temperature of 1100 ° C it is 90-110 MPa. In this case, the upper limit of porosity (10.5%) is limited by the permissible bending strength (50 MPa), and the lower (8.5%) - by the allowable thermal conductivity. The ceramic shell of the half-wave design with a thermal conductivity of not more than 1.3 W / m · K provides sufficient thermal protection of the antenna unit and the metal frame. Shells made of denser quartz ceramics (porosity less than 8.5%) are not recommended for the manufacture of antenna fairings also because of the low crack resistance, which is already manifested during the machining of a thin-walled shell with a diamond tool.

In contrast to the prototype, the impregnation of the surface of the polymer, for example, titanium methylphenylsiloxane oligomer TMFT (TU 6-02-933-74), is carried out to a depth of 0.02-0.05 of the total thickness of the half-wave wall and serves to seal the shell, as well as control and healing surface defects of the ceramic shell. The thickness of the polymer-impregnated layer is selected for the following reasons:

- it provides sealing of the porous membrane with a minimum depth of impregnation;

- does not affect the radio characteristics of the fairing, since the change in electrical thickness does not exceed 0.1%;

- the polymer is in the surface layer inside the shell, in the zone of minimum heating during high-speed mode of the fairing.

Good radiotechnical characteristics (PTX) of the fairings were achieved by profiling the walls with trapezoidal grooves to a depth of 0.003-0.01 of the antenna radiation wavelength, which is carried out depending on the dielectric constant of the material at the stage of machining of the ceramic shell. The wall profile is selected experimentally taking into account the provision of PTX in the entire range of operating frequencies, and the reproducibility of the radio characteristics of the fairings is ensured by the stability of the dielectric constant (ε) of the fairing material (the spread of ε in the shell is not more than 1.0%, and from shell to shell not more than 3% ) The trapezoidal profile of the grooves is also selected to exclude undercuts of the ceramic shell and to eliminate the occurrence of stress concentrators in the product.

The carried-out moisture-proof coating, for example, based on fluoroplastic enamel, applied to a porous ceramic shell 50-80 μm thick previously blocked with acetone creates a moisture protection of the fairing under ground conditions and is easily carried away under conditions of an autonomous rocket flight. The capillary-active pores of ceramics are blocked by spraying acetone on the surface of the shell or by wetting the shell with a tampon before coating. Evaporating, acetone creates excess pressure in the pores of the ceramics, which prevents the absorption of the material of the applied coating. Such a coating provides moisture protection of the antenna cowl and does not impair the radio technical characteristics of the cowl both after coating and after its ablation.

The manufacturing technology of antenna fairings according to the proposed technical solution includes the following steps:

- the manufacture of a ceramic shell by water slip casting in gypsum molds, followed by drying and firing to obtain a porosity of 8.5-10.5%, thermal conductivity not higher than 1.3 W / m K;

- mechanical processing of the shell with a diamond tool to a predetermined wall thickness and profile of the product with radio wrap around the ring with trapezoidal grooves according to a given program depending on the dielectric constant of the material in the shell;

- sealing the shell by impregnation on the inner surface of the shell to a depth of 0.02-0.05 of the total wall thickness with an acetone solution of organosilicon polymer TMFT with a density of 0.960-0.980 g / cm ³ and subsequent polymerization at a temperature of 220 ± 10 ° C;

- docking the shell with the frame on a special slipway and gluing the shell with the frame using sealant, for example, VIKSINT U-2-28;

- application of acetone to the outer surface by spraying or with a tampon to block the capillary-active pores of the ceramic, then a moisture-proof coating, consisting of one layer of epoxy primer EP-0101 and 3-6 layers of fluoroplastic enamel FP-566, to a total thickness of 50-80 microns.

The proposed design of the antenna cowl is shown in the drawing. It consists of a radiolucent shell made of quartz ceramic 1, Invar frame 2, connected to the ceramic shell with a layer of sealant 3.

Radiolucent sheath 1 is a half-wave design with annular grooves 4 of a depth of 0.003-0.01 working wavelength made of quartz ceramic TU 1-596-195-84 with a porosity of 8.5-10.5%, bending strength of at least 50 MPa, thermal conductivity coefficient of not more than 1.3 W / m · K, the spread of dielectric constant in the radiolucent zone of the shell is not more than 1%, and from shell to shell not more than 3%. The inner layer of the ceramic shell 5, for the purpose of sealing, is impregnated to a depth of 0.02-0.05 of the total wall thickness of the shell with a polymer, for example, TMFT organic titanium-silicon oligomer (TU 6-02-933-74). On the outer surface of the ceramic shell, a moisture-proof, abrasive coating 6 with a thickness of 50-80 μm is applied, for example, based on FP-566 fluoroplastic enamel.

Antenna fairings made according to the proposed technical solution can be used in aircraft of various purposes operating in flight modes with a bending moment on the fairing up to 5000 kgm, with a temperature on the fairing surface up to 1800 ° C, with a safety factor of at least 1 , 3.

The combination of design, technological, material science solutions allows to obtain high radio technical characteristics (according to angular errors at the level of 0.015 degrees / degree) in a wide range of temperatures and frequencies. The high stability of the dielectric characteristics of the fairing material, the reproducibility of the PTX of the fairings allows the use of hardware-based bearing error compensation in aircraft control systems.

Information sources

1. RF patent No. 2090956, IPC H 01 Q 1/42, 1994

2. RF patent No. 2209494, IPC H 01 Q 1/42, 2003

Claims (2)

1. Antenna fairing of a rocket, including a radiolucent sheath made of porous quartz ceramics, on the inside of which there is a ceramic layer with a polymer introduced into the pores, and a moisture-proof coating is applied on the outer surface, characterized in that the shell is a half-wave structure with circular trapezoidal grooves with a depth of 0.003 -0.01 of the working wavelength of the antenna, the inner layer of ceramic with polymer has a thickness of 0.02-0.05 of the total thickness of the shell wall, and the carried-out moisture-proof coating is applied to porous membrane that is digested with acetone and has a thickness of 50-80 microns. 2. The rocket antenna fairing according to claim 1, characterized in that the ceramic shell is made of quartz ceramic with porosity of 8.5-10.5%, bending strength of at least 50 MPa, thermal conductivity of not more than 1.3 W / (m · K), the scatter of the dielectric constant in the radiolucent zone of the shell is not more than 1%, and from shell to shell no more than 3%.