RU2360849C2 - System of spacecraft thermal protection - Google Patents

Abstract

FIELD: transportation; heating.

SUBSTANCE: system of spacecraft thermal protection comprises screen-vacuum heat insulation (SVHI). For SVHI device is arranged to provide for its strength and thermal characteristics in the form of through drain holes that are evenly installed along insulation surface. Heat-reflecting screens are installed above drain holes with clearances relative to SVHI. Drain holes communicate interlayer volumes of insulation and volume of gas medium under SVHI between each other and to environment. Total efficient areas of drain holes in SVHI and gaps between it and screens are defined with account of total volume of gas medium in interlayer volumes of insulation and underneath. At that gas medium pressure drop that is maximum in trajectory of carrier rocket flight and affects SVHI is also taken into account.

EFFECT: preserved strength of heat protection and its thermal characteristics during spacecraft bringing to space by carrier rocket, increased reliability of board systems and device units operation.

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Description

The invention relates to rocket and space technology, can be used in the design and creation of spacecraft (SC), launched by the launch vehicle (LV) into outer space, and is intended to protect the spacecraft body, its elements, systems and assemblies located in the spacecraft, from thermal effects of the environment.

Known and widely used in rocket science are devices for thermal protection of a fuel tank with cryogenic fuel and its pipelines [1], [2] containing screen-vacuum thermal insulation (EVTI) [3] installed on their surface to reduce losses due to evaporation of cryogenic fuel .

Possessing high thermal insulation properties, EVTI is a package consisting of sequentially arranged interlayer screens with a minimum degree of blackness, thermally insulated from each other by spacer strips. Reflective shields limit most of the heat flux due to radiation, and dividing shields reduce thermal conductivity between adjacent shields.

The effectiveness of such insulation, in addition to the properties of the materials of the screens and gaskets, is determined by the pressure in the heat-insulating layer, as well as the technology of its manufacture and installation on the elements (fuel tanks, spacecraft) of the rocket-space system (CS). Moreover, for the regular functioning of the EVTI requires the creation of a deep vacuum (up to 10 ^-4 mm Hg), since when it decreases, the thermal conductivity increases sharply [4].

According to the technical solution [1], EVTI is installed on a fuel tank with cryogenic fuel, intended for long-term storage of cryogenic fuel and its refueling in LV tanks. In this case, the fuel tank with EVTI is enclosed in a casing (thermal shell) installed with a gap with the fuel tank forming a closed sealed heat-insulating cavity between the fuel tank and the casing. To evacuate this cavity to a predetermined residual pressure, a corresponding vacuum tooling and pressure control in the cavity are provided, which significantly complicates the design of this device, which is functionally designed to operate it in ground conditions.

According to the technical solution [2], the EVTI is installed on the fuel line, also enclosed in a casing with the formation of a heat-insulating cavity evacuated to a predetermined residual pressure, and also intended for operation of the line in ground conditions.

Spacecraft thermal protection devices [5], [6] are also known and widely used in rocket science, containing EVTI installed on the surface of a spacecraft made in the form of a spacecraft (SC) and designed to heat protect compartments, systems and assemblies of spacecraft from the thermal effects of aerodynamic flow in the active phase of the LV flight, as well as during the operation of the spacecraft in autonomous flight under conditions of prolonged stay in outer space.

QC can be performed in transport-cargo (spacecraft "Progress") [5] or manned versions (spacecraft "Soyuz") [6] and consist of a system of interconnected compartments of frame and shaped structure.

The disadvantages of these technical solutions include the increased aerodynamic loads acting on the EVTI spacecraft, and the possibility of its damage in the process of launching the spacecraft into outer space. As shown by a visual inspection of the surface of the Soyuz spacecraft in outer space, the EVTI has local "swellings" and even exfoliation of its individual elements. This reduces the reliability of the operation of the EVTI and, therefore, systems and assemblies located in the compartments of the spacecraft.

As part of the Soyuz spacecraft and the Progress spacecraft, the spacecraft is installed underneath the vented fairing of the space head part (KGCh) of the spacecraft to protect it from aerodynamic flow.

The technical solution [6] is the closest to the proposed and accepted by the authors as a prototype.

The objective of the invention is to increase the structural strength of the thermal protection of the spacecraft while maintaining its thermophysical characteristics when the spacecraft is launched into outer space by a launch vehicle, as well as during the autonomous operation of the spacecraft in outer space.

The problem is solved in such a way that in the thermal protection system of a spacecraft containing EVTI, according to the invention, EVTI has a device for ensuring its strength and thermophysical characteristics in the form of through drainage holes uniformly located on the insulation surface, communicating the interlayer volumes of the insulation and the volume of the gas medium under the insulation between each other and with the external environment, while above the drainage holes there are reflective screens with gaps relative to the insulation, and the total effective area of the drainage holes and Azor between the baffles and insulation are determined by the ratios:

Where:

S, S ₁ [cm ² ] - the total area of the drainage holes and the total area of the gaps between the reflective screens and insulation, respectively;

µ, µ ₁ - coefficient of discharge of drainage holes and coefficient of discharge of gaps between reflective screens and insulation, respectively;

V [m ³ ] - the total volume of the gas medium in the insulation and under the insulation;

ΔР [kgf / cm ² ] is the maximum differential pressure of the gaseous medium acting on the insulation along the flight path of the LV;

a, c - coefficients depending on the parameters of the LV flight path approximating the curve of the relative effective area of the drainage holes versus the maximum differential pressure path acting on the insulation.

The technical results of the invention are:

- reduction of pressure drops acting on the EVTI elements of the spacecraft (interlayer screens, gaskets) and the elements of its fastening to the spacecraft, while maintaining the thermophysical characteristics of the EVTI due to through drainage holes equipped with screens reflective from radiation heat fluxes;

- determination of the total effective area of drainage holes and the gaps between the reflective screens and EVTI, ensuring the flow of the gas medium from the interlayer volumes of EVTI and volumes under the EVTI into the external environment.

The invention is illustrated by the example of solving the problem in relation to the spacecraft, made in the form of spacecraft "Soyuz", the LV launched into outer space.

Figure 1 shows a diagram of a spacecraft consisting of a system of compartments of a frame and truss structure, on the surface of which an EVTI is installed, containing a device for ensuring its strength and thermophysical characteristics.

Figure 2 shows a fragment of EVTI KK with a device for ensuring its strength and thermophysical characteristics and its main elements. The diagram illustrates the flow of the gas medium from the interlayer volumes of the EVTI and from the volume under the EVTI into the external medium (the flow of the gas medium is shown by arrows).

In these figures:

1 - frame compartment;

2 - truss compartment;

3 - screen-vacuum thermal insulation (EVTI);

4 - shell frame compartment;

5 - truss compartment rods;

6 - drainage holes;

7 - reflective screens;

8 - interlayer screens;

9 - heat-insulating gaskets.

Figure 3 shows the dependence of the maximum along the flight path of the PH differential pressure of the gas medium ΔP acting on the EVTI package, on the relative effective passage area of the drainage holes µ · S / V.

CC (figure 1) consists of a system of interconnected frame compartments 1 and truss compartment 2. On its surface is installed thermal protection containing EVTI 3. EVTI 3 is made in roll form or in separate panels and attached to the shell of the frame compartment 4 and the rods of the truss compartment 5. The joints of its individual elements are sealed.

In EVTI 3, a device for providing strength and thermophysical characteristics in the form of through drainage holes 6, evenly spaced along its surface, which communicate the interlayer volumes of EVTI 3 and the volumes of the gas medium under it between themselves and with the external medium, and reflective screens 7 installed above the drainage devices, is made holes 6 with gaps relative to EVTI 3 (figure 2).

Since the through drainage holes 6 perform uniformly on the surface of the EVTI 3, they provide uniform or close to uniform distribution of pressure in the interlayer volumes of the EVTI 3 and, consequently, the pressure drops acting on its elements. Thus, stress concentrations in its individual elements are excluded from non-uniform pressure drops in the presence of hidden local non-flow of the gas medium in the interlayer volumes of EVTI 3, which leads to an improvement in the strength and conservation of the thermophysical characteristics of EVTI 3 both in the active part of the spacecraft flight as part of the LV and in his autonomous flight in outer space.

Reflective screens 7 installed above the drainage holes 6 with a gap relative to the EVTI 3 exclude thermal heating of the spacecraft elements through the drainage holes 6 in the EVTI 3 from radiation from space objects.

The total effective area µ · S of the drainage holes 6 is determined from relation (1) using the dependence shown in Fig. 3, taking into account the maximum allowable (from the strength condition) pressure drops ΔP _dop acting on EVTI 3 and the coefficients a , c, depending on the parameters of the LV trajectory (see the valid region "A" of the definition of μ · S). In this ratio, the total volume V of the gaseous medium for the frame compartment 1 is taken as the volume consisting of the volume of the gaseous medium in the EVTI 3 and the volume between the EVTI 3 and the shell of the frame compartment 4, and for the truss compartment 2 as the volume consisting of the volume of the gaseous medium in EVTI 3 and the volume of the gaseous medium in the truss compartment 2.

The total effective area µ ₁ · S _{1 of the} gaps between the reflective screens 7 and EVTI 3 is determined from the relation (2).

Formula (1) contains a mathematical description of the dependence of the relative total effective area of the drainage holes µ · S / V on the maximum differential pressure path ΔР along the flight path of the LV and obtained from the analysis of the gas medium flow in a closed volume consisting of gasdynamically interconnected interlayer volumes of EVTI 3 and volume under EVTI 3.

In rocket science, interlayer screens 8 are made of aluminum foil several microns thick or aluminized polymer film, and heat-insulating linings 9 are made of various fiberglass materials (glass paper, fiberglass, fiberglass, etc.). Reflective screens 7 are made of a material with a minimum degree of blackness, for example, aluminum foil.

The functioning of EVTI 3 in the QC is as follows.

Since, unlike the prototype, through-hole drainage holes 6 are evenly made on the surface of EVTI 3, the gas medium flows from the volume under EVTI 3 and its interlayer elements through through-hole drainage holes 6 into the external environment (Figs. 1, 2).

The outflow of the gaseous medium into the external medium occurs at subsonic speeds with non-locking in the drain holes 6, since the total effective area µ ₁ · S _{1 of the} gaps between the reflective screens 7 and EVTI 3 is made greater than or equal to the total effective area µ · S of the drain holes 6 ( µ ₁ · S ₁ ≥µ · S) in accordance with relation (2).

During the flight of the spacecraft as a part of the OGC on the active site of the LV flight in the interlayer volumes of insulation, a pressure close to the pressure under the cowl of the OGC is established. In this case, the gas medium from the interlayer volumes of EVTI 3 and from the volume below it flows into the volume under the KGC fairing and then through the drainage device in the KGC fairing to the atmosphere, the geometric characteristics of which are set such that the pressure under the KGC fairing becomes close to atmospheric (static ambient atmosphere) )

In an autonomous flight of spacecraft in the interlayer volumes of EVTI 3 and under it, an internal pressure close to atmospheric is established. The pressure drops in the composition of the KGCH and the autonomous flight of the spacecraft, while acting on the interlayer screens 8 and heat-insulating gaskets 9 EVTI 3, are close to zero. Reflective screens 7 mounted above the through drainage holes 6 exclude the influence of heat flux on the spacecraft elements from radiation from space objects.

Thus, they increase the structural strength of thermal protection by reducing the aerodynamic loads acting on the EVTI, and preserve its thermophysical characteristics, ensuring the thermal mode of operation of devices, systems and units located in the compartments of the spacecraft, which leads to the achievement of the task. Thereby increase the reliability of the QC operation.

Currently, the technical solution has been tested experimentally and is being implemented at Soyuz spacecraft. Requirements for the drainage of EVTI are introduced in the OST and are an integral element in the technological cycle of production of spacecraft.

The technical solution can be used for various types of spacecraft, near-Earth, interplanetary, cargo, manned and other spacecraft, launched by spacecraft and other means of launching spacecraft into outer space.

Literature

1. The spaceport. Ed. prof. A.P. Volsky, VI of the Ministry of Defense of the USSR, M., 1977, p. 160-161, Fig. 5.3, 5.4.

2. Ibid., P. 164, fig. 5.6.

3. Cosmonautics: Encyclopedia. / Ed. V.P. Glushko. M .: Soviet Encyclopedia, 1985, p. 394.

4. Handbook of the physical and technical foundations of cryogenics. / Ed. prof. M.P. Malkova. M .: Soviet Encyclopedia, 1973, p. 236-237.

5. Cosmonautics: Encyclopedia. / Ed. V.P. Glushko. M .: Soviet Encyclopedia, 1985, pp. 304-305.

6. Ibid., P. 369-370.

Claims (1)

A spacecraft thermal protection system containing screen-vacuum thermal insulation, characterized in that the said insulation has a device for providing its strength and thermophysical characteristics in the form of through drainage holes evenly spaced along the insulation surface, communicating the interlayer volumes of the insulation and the volume of the gas medium under the insulation between themselves and with the external environment, while reflective screens with gaps relative to insulation are installed above the drainage holes, and the total effective the area of the drainage holes and the gaps between the reflective screens and insulation are determined from the ratios

,

,
S, S ₁ [cm ² ] - the total area of the drainage holes and the total area of the gaps between the reflective screens and insulation, respectively;
µ, µ ₁ - coefficient of discharge of drainage holes and coefficient of discharge of gaps between reflective screens and insulation, respectively;
V [m ³ ] - the total volume of the gas medium in the insulation and under the insulation;
ΔР [kgf / cm ² ] is the maximum differential pressure of the gaseous medium acting on the insulation along the flight path of the launch vehicle;
а, в - coefficients depending on the parameters of the flight path approximating the curve of the effective area of the drainage holes versus the maximum differential pressure path acting on the insulation.

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