RU2449263C1 - Apparatus and method of controlling radiation flux when conducting ground-based thermal-vacuum tests on spacecraft - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: apparatus has a radiation energy receiver made from two thin-wall plates placed next to each other. The working surfaces of the thin-wall plates are coated with a thermal control coating - on the first plate with a low solar absorption factor and high thermal emissivity, and on the second plate with a high solar absorption factor and high thermal emissivity. A heat sensitive element is placed on each nonworking surface of the plates. The nonworking surface of each thin-wall plate having a heat sensitive element is coated with a thermal control coating with high solar and thermal radiation reflecting power.

EFFECT: possibility of controlling radiation flux based on spectra of radiation falling on spacecraft in the region of interest of a thermal-vacuum chamber.

2 cl, 3 dwg

Description

The invention relates to space technology, namely, to control the heat transfer of space objects with a space environment simulated in terrestrial thermal vacuum chambers (TCEs) during thermal vacuum tests (TWI).

TWI are aimed at determining the health and resource of space objects (spacecraft), for example, a spacecraft (SC) or its components, at an ambient pressure corresponding to the region of radiation heat transfer, and when exposed to electromagnetic radiation in the wavelength range corresponding to the region of thermal radiation [1 , p.11]. It is accepted that for a complete study of the thermal regime of spacecraft it is enough to reproduce the following basic factors of outer space: high vacuum, solar radiation, planet radiation, “cold” and “blackness” of space outside the solid angles occupied by the planet and the Sun [2, 127]. In this regard, when designing TCEs simulating space conditions or thermal conditions of spacecraft, the question always arises of the maximum permissible error in reproducing external radiant fluxes and cosmic vacuum. The solution to this problem is especially important when testing QoS with a passive thermal control system, where increased accuracy of reproduction of incident radiant fluxes is required. This primarily refers to the spectrum, the uniformity of the radiation density in volume and angular distribution. The deviation of these characteristics from field values leads to a distortion of the temperature field of the KO design [2, p.12].

As a rule, TWI is subjected to KO with a very complex configuration of the external surface, the temperature of which is entirely determined by the heat balance with the surrounding elements and internal heat sources. Moreover, the outer surface of the CO can be substantially heterogeneous in its optical radiation characteristics (for example, the coefficients of thermal radiation (ε _t ) and absorption of solar radiation (α _s )), which affects the reaction of different parts of its external surface to different regions of the spectrum of the incident radiant flux. In TCEs, the position of the CO is modeled, and its orientation with respect to external energy sources, in particular, solar radiation simulators (ICI), the design of which includes a radiation source and a collimating reflector [1, p. 38].

Given the above, the fundamental moment in the organization of ground-based TWEs is the control of radiant fluxes, taking into account the emission spectra, on a space object. The results of the control of radiant fluxes, taking into account the emission spectra, allow us to answer the question of the permissibility of errors in imitation of external influences. Their information to the values that provide in total a small effect on the output results, or to the values that provide the possibility of their accounting or compensation [1, p. 75].

Note the main sources that make up the imitation errors. In a number of ISI systems, re-reflection of CO radiation is present. Those. own radiation of the radiation emitted in the direction of the collimating reflector of the ICI partially returns to the radiation back [1, p. 39]. In addition, the intrinsic thermal radiation of a collimating specular reflector determines another component of the error in simulating solar radiation. Even the most advanced elements of optical circuits absorb up to (10-15)% of the radiation incident on them [1, p. 39]. A cooling system can be used to remove thermal loads from the mirror reflectors that appear when some of the radiant flux incident on them is absorbed. Usually it is performed at temperature levels of about 300 K (when cooled by water) or about (120-150) K (when cooled by liquid nitrogen) [1, p. 43]. In addition, in the TCEs, the “cold” and “blackness” of outer space is imitated using heat-absorbing cryoscreens (CE). However, the absence of sufficiently technologically advanced black coatings having a degree of blackness ε _m > (0.8-0.95) [1, p.28] leads to the reflection of the CE part of the thermal radiation incident on them. Thus, the FE radiation and reflected radiation can lead to significant radiant fluxes emitted by FE inside the TCE.

The presence of the above systematic errors of imitation of external influences can be justified only when they are taken into account. This implies the need to develop devices and methods for controlling radiant fluxes, taking into account the emission spectra that make up the imitation error in terrestrial TWI of space objects.

There are devices and methods for determining the radiant flux in ground-based TWR of space objects, for example, the calorimetric method, thermoelectric method, photometric method [2, p. 300].

Calorimetric method based on measuring the quantity of heat enough perceived black (ε _r = 0,95-0,98) surface. It is achieved with the help of special black enamels in combination with such a geometry, which leads to repeated re-emission and absorption of all the rays incident on it within the receiver. The disadvantages of the calorimetric method include the large inertia and inconvenience of using devices implementing this method in TCEs.

The thermoelectric method is based on the use of thermoelectric radiation detectors - thermocouples, thermo columns or bolometers. The disadvantage of thermal receivers (especially thermocouples) is their low sensitivity [2, p. 301].

The photometric method is based on the use of solar cells that convert the radiation incident on them directly into electric current. However, these elements have significant selectivity in the spectrum of absorbed radiation, and their signal depends on the temperature of the element [1, p.131].

The aforementioned devices and methods cannot be used to control the radiant flux in terrestrial TWI of space objects, since they do not allow the separation of the radiated flux from the thermal (infrared) fluxes simulated in the TCEs from the TCEs that constitute the simulation error.

A prototype of the proposed device and method for monitoring radiant flux in ground-based TWI of space objects was not found.

The objective of the invention is to provide reliable simulation of external influences on a space object with the separation of radiant energy simulated by the solar emitter from the radiant fluxes of the TCE structure constituting an imitation error, while the device and method would have sufficient simplicity of monitoring.

The problem is solved by a radiant flux control device for ground-based heat-vacuum tests of space objects, in which a radiant energy receiver with heat-sensitive elements is made of two adjacent thin-walled plates of materials with high thermal conductivity in the form of a square or circle and mounted on stretch threads in the controlled area of the heat-vacuum chamber, thermoregulatory coatings are applied to the plates on both sides so that the total thickness of the plates with coatings h and the characteristic size of the plates L correspond to the ratio h << L, on the working surfaces of the plates installed in one plane perpendicular to the controlled radiant flux, thermoregulatory coatings are applied - on the first one with a low absorption coefficient of solar radiation (α _s11 ^min ) and a high coefficient of thermal radiation (ε _T11 ^max ) corresponding to the ratio α _s11 ^min / ε _T11 ^max << 1, on the second with high absorption coefficients of solar (α _s21 ^max ) and thermal (ε _T21 ^max ) emissions, corresponding to the ratio α _s21 ^max / ε _T21 ^max ≈ 1, and to the non-working one surface of the first and second pla the wafers are installed on an electrically insulated thermosensitive element, on the non-working surface of each thin-walled plate with a thermosensitive element, a thermostatic coating is applied with a high reflectivity of solar and thermal radiation, where the absorption coefficients of solar (α _s12 ^min ) and thermal (ε _T12 ^min ) radiation for the first thin-walled plate and the absorption coefficients of solar (α _s22 ^min ) and thermal (ε _T22 ^min ) radiation for the second thin-walled plate correspond to the relations α _s12 ^min / ε _T12 ^min ≈1 and α _s22 ^min / ε _T22 ^min ≈1, respectively.

The problem is solved by the method of controlling radiant fluxes during ground-based heat-vacuum tests of space objects, in which the thermal equilibrium states of both thin-walled plates of the radiant energy receiver are recorded, after which the temperatures of the first (T ₁ ) and second (T ₂ ) thin-walled plates are measured, and the control of radiant fluxes separating solar radiation (Q _s ) from infrared heat fluxes that make up the imitation error (Q _ir ), is determined by the ratios:

where E ₁ = ε _T12 ^min / ε _T11 ^max , E ₂ = ε _T22 ^min / ε _T21 ^max is the relative coefficient of thermal radiation of the first and second thin-walled plates with temperature-controlled coatings, respectively;

A ₁ = α _s11 ^min / ε _T11 ^max , A ₂ = α _s21 ^max / ε _T21 ^max - optical characteristic of the temperature-controlled coating of the working surface of the first and second thin-walled plates, respectively;

σ is the Stefan-Boltzmann constant.

It is proposed to install in a TCE two adjacent thin-walled plates (TP) of the radiant flux control device so that their working surfaces are in the same plane perpendicular to the controlled solar flux from the IRF, which is caused by the need for the incident radiation with the same spectral composition and radiation energy on the working surfaces of two TP .

It is proposed to make thin-walled plates in the form of a square or circle, corresponding to the ratio h << L, which is caused primarily by the requirements: low inertia of the radiant flux control device and minimal heat leakage through the lateral surfaces of the TP.

It is proposed to install thin-walled plates on stretch threads in the controlled area of TCEs, which is caused by the requirement of minimal heat leakage through the design of the TP fastening in TCEs (stretch threads). For the convenience of placing the radiant flux control device in the TCEs, it can be proposed to pre-install two thin-walled plates that make up the device using stretching threads on a frame, which is also installed using stretching threads in the controlled area of the TCEs.

It is proposed to carry out TP from materials with high thermal conductivity (for example, from metals or alloys based on them, which make it possible to produce sufficiently elastic thin-walled plates). Given the minimum heat loss through the lateral surface of the plates and through the stretching threads, this proposal makes it possible to obtain thin-walled plates close to isothermal, which is taken into account below in the heat balance of the TP of the radiant flux control device.

It is proposed to apply special thermostatic coatings (TRP) on the working surfaces of each of the two TPs (on the first thin-walled plate of the TPP with high ability to reflect solar energy and absorb energy in the infrared region of the spectrum, on the second thin-walled plate of the TPP with high absorption in the spectral region from ultraviolet rays to the far infrared region), which is caused by the need to separate the radiation from the IRR (Q _s ) from the thermal radiant fluxes of TCEs (Q _IR ), which constitute a simulation error.

It is proposed to apply on non-working surfaces of the first and second thin-walled TRP plates with high reflectivity in the entire spectrum interval from ultraviolet rays to the far infrared region, which is caused by the need to minimize the contribution to the thermal balance of each of the two TPs from the effective radiation from the structural elements of the TVK and KO.

Estimates of the temperatures of the elements of the KO, ISI reflector [1, p.12-13], show that the maximum heating of the surfaces of these elements at a level of up to (300-600) K is possible, i.e. at temperatures corresponding to radiant fluxes with a maximum radiation intensity, according to Wien's law [3, p.149], in the wavelength region starting from 4-5 microns and more. In addition, it is known that 99% of the energy of the solar spectrum lies within the wavelength range from 0.2 to 3 μm [2, p. 298], and in the range from 0.3 to 3 μm, 92% of the entire radiant energy of the Sun is concentrated [2 , p.20].

These circumstances make it possible, by selecting the appropriate TRP for the working and non-working surfaces of thin-walled plates, to isolate in the TCEs the radiant fluxes of ICI (the maximum total energy of which is limited by wavelengths from 0.2 to 3 μm) from infrared radiant fluxes from the designs of TCEs (whose radiation lies in the wavelength region starting from 4-5 microns or more).

For working surfaces of two thin-walled plates, radiant flux control devices can be recommended TRP:

1) for the first TP, a TRP based on fiberglass from radiation-resistant glass with an internal reflective layer of silver or aluminum is proposed. So TRP with a reflective layer of silver has a coefficient of absorption of solar radiation α _s ^min = (0.06-0.08) and a coefficient of thermal radiation in the wavelength range of more than 4 μm, ε _t ^max = 0.9 [4, p.166 , 170];

2) for the second TP, it is proposed to perform TRP from loose "black", representing a metallic substance in a finely divided state, with a layer thickness reaching 30–40 μm or more, in accordance with the maximum wavelengths of the absorbed radiation. It is proposed that this coating layer be made, for example, of Au in the form of a loose "mobile", as having a maximum absorption coefficient in a wide range of wavelengths [5, p. 56]. You can also suggest to create a surface with the highest possible ε _t ^max and α _s ^{max to} use a coating made on the basis of black matte paint, under appropriate operating conditions [3, p.372-373].

For non-working surfaces of each of the two thin-walled plates, it is proposed to use a TRP made of a film aluminized on one side, metallized outward, covering the non-working surface of the plate together with a heat-sensitive element mounted on it. This TRP has a high reflectivity (α _s ^min and ε _T ^min ) in the entire range of the spectrum from ultraviolet to far infrared [6, p.780].

The electrically insulated heat-sensitive elements mounted on the non-working surface of the first and second TP can be made, for example, in the form of a spiral winding or in the form of a rectangular winding (zigzag) of a very thin conductive metal wire or tape made, for example, of Cu or Pt. Each electrically insulated thermosensitive element has a previously performed calibration characteristic, expressed by the dependence of the resistance on temperature. Through electrically insulated current leads, the thermosensitive element can be connected either to the bridge circuit or to the circuit with load resistance, which allows you to register a change in the resistance of the thermosensitive element.

The essence of the invention is illustrated in figures 1-3. Figure 1 and 2 shows the design of the proposed device. Figure 3 - the method of its application.

The radiant flux monitoring device 1 is made of two adjacent thin-walled plates (TP) 2 and 3 of materials with high thermal conductivity in the form of a square or circle and mounted on stretch braids 8 on frame 9 in the controlled area of the thermal vacuum chamber (TCE) 15, on TP 2 and 3, thermal control coatings (TRP) 12 and 13 are applied on both sides so that the total thickness (h) of TP 2 and 3, with TPP, and the characteristic size (L) of TP 2 and 3 correspond to the ratio h << L, on the workers surface 10 TP 2 and 3, installed in the same plane and facing in the same direction dikulyarno controlled solar radiant flux 14 applied TRP 12 - 2 on the first TP with low solar radiation absorption coefficient (α _s11 ^min) and high thermal emissivity (ε _T11 ^max), corresponding to the relation α _s11 ^min / ε _T11 ^max << 1 on the second TP 3 with high absorption coefficients of solar (α _s21 ^max ) and thermal (ε _T21 ^max ) radiation, corresponding to the ratio α _s21 ^max / ε _T21 ^max ≈1, and on the non-working surface 11 of the first TP 2 and the second TP 3 are installed on an electrically insulated temperature sensitive element 4 and 5 with current leads 6 and 7. thermosensitive elements 4 and 5 and non-working surface 11 of each TP 2 and 3 thermoregulatory coatings 13 with high reflectivity of solar and thermal radiation, where the absorption coefficients of solar (α _s12 ^min ) and thermal (ε _T12 ^min ) radiation for the first TP 2 and absorption coefficients solar (α _S22 ^min ) and thermal (ε _T22 ^min ) radiation for the second TP 3 correspond to the relations α _S12 ^min / ε _T12 ^min ≈1 and α _S22 ^min / ε _T22 ^min ≈1, respectively. TCEs 15 include: cryogenic screens (CE) 17; a solar radiation simulator (ISI), including an ISI 19 radiation source and an ISI 16 collimating reflector; space object under study (KO) 18; a radiant flux control device 1, installed in the controlled area of the TVK 15, on the working surfaces of the plates of which the radiant flux 14 from the collimating reflector ISI 16 falls.

A device and method for monitoring radiant fluxes during ground-based thermal vacuum tests of space objects operate as follows.

A space object 18 is placed in the TCE 15, equipped with cryogenic screens 17 and a solar radiation simulator, including an ISI 19 radiation source and an ISI 16 collimating reflector. For example, xenon lamps can be used as an radiation source of ISI 19. The spectral curve of the xenon lamp goes close to the solar curve, starting from the ultraviolet end of the spectrum and to the infrared region. Using special filters (not shown in the figure), it is possible to bring the spectrum of the lamp even closer to the spectrum of the Sun [2, p. 289]. To control the solar radiant flux from the collimating reflector ISI 16 and infrared radiant fluxes (not shown) from the structural elements of the TVC 15 and the collimating reflector ISI 16, which constitute an error in simulating the external conditions in the controlled area of the TVC 15, install a device for monitoring radiant flux 1. Device control radiant flux 1 is performed from two adjacent thin-walled plates 2 and 3, mounted on the strands-braces 8, or directly in the TCE 15 or on the frame 9, in the controlled area TCE 15. The working surfaces of 10 plates 2 and 3 are installed in the same plane and turned in one direction perpendicular to the controlled solar radiant flux 14. In order to minimize the effect on the processes of radiant heat exchange used in the experiment, the radiant flux control device 1, its characteristic size should be much smaller than the characteristic size of the controlled portion of the space object 18. After performing operations to prepare the space object 18 and TCE 15 for TWI, the thermal vacuum chamber 15 is closed, sealed and begin to provide in TCE 15 Operating conditions 18 KO's close to space. Upon reaching the required pressure in TCEs in the range of (10 ^-3 -10 ^-4 ) Pa and cooling the cryogenic screens, for example, to the temperature of liquid nitrogen, an experiment is started. The radiation source ISI 19 is turned on. After switching on the radiation source ISI 19, reflected from the collimating reflector ISI 16, the radiant flux 14, close to the spectrum of the Sun, and the infrared flux (not shown), from the TCE structural elements, fall onto the working surfaces 10 of the first TP 2 and a second 3 TA radiant flux control device 1. since the working surface of the first TP 2 TRP covered with low solar radiation absorption coefficient (α _s11 ^min) and a high coefficient of thermal emission (ε _T11 ^max), then this surface is max mally reflect the solar radiant flux 14 of ICI and the maximum absorbing infrared radiant fluxes from TCEs structural elements. And the working surface of the second TP 3, covered with TRP with a high coefficient of absorption of solar radiation (α _s21 ^max ) and a high coefficient of thermal radiation (ε _T21 ^max ), will absorb radiation from the collimating reflector ISI 16 and infrared rays from the structural elements of TVK 15 to the maximum. The non-working surfaces of the first TP 2 and the second TP 3 absorb a negligible fraction of the radiant energy incident from the structural elements of the TVC 15, in particular KE 17, and KO 18, due to the TPP deposited on these surfaces with a minimum coefficient of absorption of solar radiation and with a minimum coefficient of thermal radiation. The radiant fluxes from the ISI and TCEs absorbed by the first TP 2 and the second TP 3 of the radiant flux control device 1 evenly heat each TP due to the high thermal conductivity of the TP material, the use of stretch threads and the fulfillment of the condition h << L. The conductive metal strip or wire (not shown in the figure) of the temperature-sensitive element 4 and 5 of each TP 2 and 3 is heated to the corresponding average equilibrium temperature for each TP. A conductive metal strip or wire of thermosensitive elements 4 and 5 is connected using current leads 6 and 7 to a small current circuit. In this case, the voltage at the ends of the tape or wire, which varies depending on the temperature of the medium (temperature TP 2 and 3), is fed to a fixing device (not shown in the figure). After reaching the equilibrium thermal state of each TP 2 and 3, the electrical resistance of the tape or wire of the thermosensitive elements 4 and 5 is simultaneously measured and the temperature of the first TP 2 (T ₁ ) and second TP 3 (T ₂ ) of the radiant flux monitoring device are determined by the calibration characteristic. in relations (1) and (2), the known optical characteristics of the TRP for the working and non-working surfaces of the first TP 2 and the second TP 3, as well as the recorded values of T ₁ and T ₂ . Control radiant flux separating solar radiation (Q _s) from ICI thermal (infrared) flow (Q _ik) TCEs 15 constituting simulation error is determined from the relations (1) and (2).

The derivation of functional dependencies (1) and (2) is made under the following assumptions:

1) the energy of radiant fluxes perceived by thin-walled plates is removed through the working and non-working surfaces of the TP into the environment only by radiation;

2) heat loss through the lateral surfaces of the TP, stretching threads and current leads of thermally sensitive elements are negligible and are not taken into account in the heat balance;

3) each TP is considered isothermal with the steady thermal state of the system in question;

4) the radiant energy absorbed by the non-working surfaces of each thin-walled plate is considered small in comparison with the absorbed surfaces of the working surfaces, and TP is not taken into account in the heat balance.

We present the heat balance equations for two thin-walled plates of a radiant flux control device placed in a controlled region of a TCE. On the working surfaces of the first and second TP, installed side by side in the same plane, a controlled solar radiant flux Q _s from the ISI falls perpendicular to these surfaces. In addition, on the working and non-working surfaces of each transformer substation and on their side surfaces, infrared radiation from the structural elements of the TCEs, including from the structural elements of the ICI, is incident.

Taking into account the assumptions made, the system of heat balance equations for the first and second TP, with the steady state of each plate placed in a TCE with ISI, we write in the following form:

- for the first thin-walled plate

- for the second thin-walled plate

In equations (3) and (4) on the left side shows the absorption of radiation (solar infrared Q _s and Q _ik) working surfaces of each TP, and the right side - the intrinsic radiation from the working and non-working surfaces of each TA.

Using the relative parameters E ₁ = ε _T12 ^min / ε _T11 ^max , E ₂ = ε _T22 ^min / ε _T21 ^max , A ₁ = α _s11 ^min / ε _T11 ^max , A ₂ = α _s21 ^max / ε _T21 ^max , the system of equations ( 3) and (4) we transform to the form:

- for the first thin-walled plate

- for the second thin-walled plate

Solving the system of equations (5) and (6), we obtain expressions (1) and (2) for the radiant fluxes Q _s and Q _ir controlled in this TCE region.

We give a calculated example of the application of the radiant flux control device during thermal vacuum tests of space objects and the method for its implementation.

The dimensions of all parameters in the calculation example are given in the International system of units.

We place the CO in a TCE equipped with cryogenic screens and a simulator of solar radiation, including an ISI radiation source and an ISI collimating reflector. To simulate the solar spectrum, we use a xenon lamp as the radiation source of the ICI, the spectral curve of the xenon lamp goes close to the solar curve, starting from the ultraviolet end of the spectrum and to the infrared region. Using special filters (not shown in the figure) we further approximate the spectrum of the lamp to the spectrum of the Sun [2, p. 289].

To control the solar radiant flux from the ISI and infrared heat fluxes from TCEs, which constitute an error in the simulation of external conditions, we install a radiant flux control device in the controlled area of the TCEs. The radiant flux monitoring device is made of two adjacent thin-walled plates, each of which is assumed to be made of BrB2 bronze alloy (solid state) [6, p. 59] in the form of a square with a side suppose L = 20 mm and thickness h = 0.1 mm installed on stretch threads made of sewing thread [7] in the controlled area of TCEs. We apply TRP to the working surface of the first TP, suppose, based on fiberglass made of radiation- _resistant glass with an internal reflective layer of silver with a solar radiation absorption coefficient α _s11 ^min = 0.06 and thermal radiation coefficient, in the wavelength range of more than 4 μm, ε _T11 ^max = 0 9 [4, p. 166, 170]. Suppose that on the working surface of the second TP we apply TRP using a coating made on the basis of black matte paint with ε _T21 ^max = 0.98 and α _s21 ^max = 0.99 [3, p.372-373]. For non-working surfaces of each of the two thin-walled plates, suppose we use a TRP made of a film aluminized on one side, metallized outward, covering the non-working surface of the TP together with a heat-sensitive element mounted on it. Suppose that this TRP has a high reflectivity (α _s ^min and ε _T ^min ) in the entire spectrum range from ultraviolet to far infrared with α _s ^min = 0.08 and ε _T ^min = 0.025 [6, p. 780]. Taking into account the accepted assumption (4), in the derivation of dependencies (1) and (2), we take into account in the calculation example only ε _T ^min = ε _T12 ^min = ε _T22 ^min = 0.025.

We determine the relative coefficients of thermal radiation of the first and second TP with temperature-controlled coatings:

,

,

.

.

We determine the optical characteristics of the thermostatic coating of the working surface of the first and second TP:

,

,

.

.

We install the working surfaces of TP in one plane and turn in one direction perpendicular to the controlled solar radiant flux.

After completing the operations to prepare the space object and the thermal vacuum chamber for the TWI, we close the heat vacuum chamber, seal and begin to provide in the TCE the operating conditions of the space object that are close to the space ones. Upon reaching the required pressure in TCEs in the range of (10 ^-3 -10 ^-4 ) Pa and cooling the cryogenic screens, for example, to the temperature of liquid nitrogen, we begin the experiment. ISI radiation source is turned on.

After turning on the radiation source of the IRR, the radiant flux reflected from the collimating reflector of the IRR, close to the spectrum of the Sun, and the infrared flux from the structural elements of the TCEs fall on the working surfaces of the first and second TPs of the radiant flux control device.

Since the working surface of the first TP is covered with TRP with a low coefficient of absorption of solar radiation (α _s11 ^min ) and a high coefficient of thermal radiation (ε _T11 ^max ), this surface will reflect the radiant flux of the ICI to the maximum and absorb infrared radiant flux from the structural elements of the TCE to the maximum. And the working surface of the second TP, covered with TRP with a high coefficient of absorption of solar radiation (α _s21 ^max ) and a high coefficient of thermal radiation (ε _T21 ^max ), will absorb radiation from the collimating reflector of the ICI and infrared rays from the structural elements of the TVC to the maximum. The non-working surfaces of the first and second TP absorb a negligible fraction of the radiant energy incident from the cryoscreens and the space object due to the TPD installed on these surfaces with a minimum coefficient of absorption of solar radiation (α _s ^min ) and with a minimum coefficient of thermal radiation (ε _T ^min ).

The radiant flux absorbed by the first and second TPs of the radiant flux control device uniformly heats each TP due to the high thermal conductivity of the TP material, the use of stretch threads with minimal heat loss through them, and also the fulfillment of the condition h << L, which allows to obtain minimal heat loss through the side surfaces of the TP.

The conductive metal strip or wire of the thermosensitive element of each TP is heated to the average equilibrium temperature corresponding to each TP. After reaching the equilibrium thermal state of each TP, the electrical resistance of the tape or wire of thermosensitive elements is simultaneously measured and the temperature of the first TP (put T ₁ = 263 K) and the second TP (put T ₂ = 403 K) of the radiant flux control device are determined by the calibration characteristic.

We substitute into the relations (1) and (2) the known optical characteristics of the TRP for the working and non-working surfaces of the first and second TP, as well as the fixed values of T ₁ and T ₂ :

,

,

where σ = 5.67 · 10 ^-8 W / (m ² · K ⁴ ).

The application of the proposed design of the radiant flux control device for ground-based thermal vacuum tests of space objects and the method for its implementation allow:

1) to control the magnitude of the radiant flux, taking into account certain areas of the radiation spectra incident on the space object in the place of interest in the thermal vacuum chamber;

2) to separate the simulated radiant fluxes of the ISI from the heat fluxes of the TCEs, which constitute the imitation error;

3) reduce the cost of ground-based experimental testing of space objects, under the conditions of modeling cosmic radiation and vacuum in TCEs, due to the simplicity of the design of the device and its implementation;

4) determine the magnitude of the intensity of the radiant flux from the proposed functional dependencies, including the minimum number of process-controlling parameters that affect the accuracy of measurements;

5) automate the process of experimental determination of radiant fluxes in a heat-vacuum chamber, using information from the corresponding heat-sensitive elements.

LITERATURE

1. O. B. Andreychuk, N. N. Malakhov. Thermal tests of spacecraft. - M.: Mechanical Engineering, 1982.

2. Modeling the thermal conditions of the spacecraft and its environment. Ed. Acad. G.I. Petrova. - M.: Mechanical Engineering, 1971.

3. M.A. Mikheev. The basics of heat transfer. Gosenergoizdat, 1956.

4. L.A. Novitsky, B.M. Stepanov. Optical properties of materials at low temperatures. Directory. - M.: Mechanical Engineering, 1980.

5. Physical encyclopedic dictionary. - M.: Soviet Encyclopedia, 1983.

6. Physical quantities. Handbook Ed. I.S. Grigorieva, E.Z. Meilikhova. - M .: Energoatomizdat, 1991.

7. GOST 6309-93 "Sewing cotton and synthetic threads. Technical conditions."

Claims (2)

1. A radiant flux control device for ground-based heat-vacuum tests of space objects, characterized in that the radiant energy receiver with heat-sensitive elements is made of two adjacent thin-walled plates made of materials with high thermal conductivity in the form of a square or circle and mounted on stretch threads in the controlled heat-vacuum region chamber, thermo-regulating coatings are applied to the plates on both sides so that the total thickness of the plates with coatings h and the characteristic plate size L from correspond to the ratio h << L, on the working surfaces of the plates installed in one plane perpendicular to the controlled radiant flux, thermoregulatory coatings are applied - on the first with a low absorption coefficient of solar radiation (α _s11 ^min ) and a high coefficient of thermal radiation (ε _T11 ^max ), corresponding to the ratio α _s11 ^min / ε _T11 ^max << 1, to the second with high absorption coefficients of solar (α _s21 ^max ) and thermal (ε _T21 ^max ) radiation, corresponding to the ratio α _s21 ^max / ε _T21 ^max ≈ 1, and to the idle surface first and second plast s mounted on electrically insulated thermal sensing element in a non-working surface of each thin-walled plate with a thermosensitive element coated with thermal control coating with high reflectivity of solar and thermal radiation, wherein the absorption coefficients of sunlight (α _s12 ^min), and thermal (ε _T12 ^min) radiation for a first thin-walled plates and the absorption coefficients of solar (α _s22 ^min ) and thermal (ε _T22 ^min ) radiation for the second thin-walled plate correspond to the relations α _s12 ^min / ε _T12 ^min ≈1 and α _s22 ^min / ε _T22 ^min ≈1, respectively. 2. A method for controlling radiant fluxes during ground-based thermal vacuum tests of space objects, characterized in that the thermal equilibrium states of both thin-walled plates of the radiant energy receiver are recorded, after which the temperatures of the first (T ₁ ) and second (T ₂ ) thin-walled plates are measured, and the control of radiant fluxes separating solar radiation (Q _s ) from infrared heat fluxes that make up the imitation error (Q _IR ), is determined by the ratios:
Q _s = σ ·  (1 + E ₂ ) · T ₂ ⁴ - (1 + E ₁ ) · T ₁ ⁴  / (A ₂ -A ₁ ),
Q _ir = σ · (1 + E ₂ ) · T ₂ ⁴ -Q _s · А ₂ ,
where E ₁ = ε _T12 ^min / ε _T11 ^max , E ₂ = ε _T22 ^min / ε _T21 ^max is the relative coefficient of thermal radiation of the first and second thin-walled plates with temperature-controlled coatings, respectively;
A ₁ = α _s11 ^min / ε _T11 ^max , A ₂ = α _s21 ^max / ε _T21 ^max - optical characteristic of the temperature-controlled coating of the working surface of the first and second thin-walled plates, respectively;
σ is the Stefan-Boltzmann constant.

Images