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Modern space technology is characterized by structures that operate under conditions of intense, often extreme, thermal influences. The general trend in the development of technology is associated with an increase in the number of critical heat-loaded technical objects with rougher conditions for their thermal loading with simultaneously increasing reliability and service life, reducing material consumption. For spacecraft, ensuring thermal conditions is one of the most important sections of design, determining the main design decisions. Characteristic features of modern heat-loaded structures of space technology are nonstationarity, nonlinearity, multidimensionality, and the conjugate nature of heat and mass transfer processes. These features limit the possibility of using many traditional computational-theoretical and experimental research methods. Highly porous thermal insulation materials with low thermal conductivity are widely used in the thermal protection designs of modern space technology objects. These materials typically have an open-pore structure. This leads to the fact that the thermophysical properties of these materials depend significantly on the gas pressure of the medium in which heat-protective structures based on them operate. It can also be noted that as the ambient pressure increases, a more intense increase in the thermal conductivity coefficient is observed. The purpose of this work is to develop a complex of experimental and mathematical tools for a system of identification of the properties of highly porous materials operating under conditions of not only changing thermal loads, but also of variable pressure. [ABSTRACT FROM AUTHOR]

The authors have solved the problem of simultaneous determination of a set of coefficients of a mathematical heat-transfer model for semitransparent materials: the thermal conductivity of a material and the coefficient of its heat exchange with the external medium, the heat flux from the heater, that has been absorbed by the material, and the coefficient of linear absorption of the material. [ABSTRACT FROM AUTHOR]

Sensors for diagnosing thermal regimes of heat-loaded structures have been developed and tested. To process the results of these tests, use was made of computational methods based on solving inverse problems of heat conduction. Heat flux sensors made of high-temperature ceramics are considered. [ABSTRACT FROM AUTHOR]

The presented work is a continuation of the development of a computational and experimental method for determining the thermophysical characteristics (TPC) of the stator coils of a generator operating with the use of the phenomenon of high-temperature superconductivity (HTSC). The paper considers algorithms for identifying heat transfer models in the composite material of the stator coil winding. Using the discovered thermophysical properties, it is planned to study the electrothermal interaction in a high-temperature superconductor before its transition to a superconducting state. There is a significant variety of methods for solving the problems of identifying mathematical models of heat transfer, in particular, of determining the thermophysical characteristics of composite materials. As a result of the analysis of alternative methods for solving the identification problem, the iterative regularization method is used in this work. [ABSTRACT FROM AUTHOR]

This work is devoted to the development of a procedure for the calculation and experimental determination of the thermophysical characteristics of the stator coils of a generator operating using the phenomenon of high-temperature superconductivity. To realize the conditions close to operational ones, temperature regimes of cooling down the coil from 300 to 78 K with subsequent heating to 300 K were implemented during the experiment. The values of the thermophysical characteristics were calculated from the data of temperature measurements at the internal points of the samples. The paper presents a description of the experimental technique. [ABSTRACT FROM AUTHOR]

An experimental installation for laser heating (ULN-1) has been developed to implement a technique for identifying mathematical models of radiative-conductive heat transfer without using contact measurements. A substantiation of the choice of the system components and of the procedure for its application is given. Approbation of the installation and of the identification technique was carried out on the example of determining the thermophysical characteristics of a thin plate made of an opaque material. [ABSTRACT FROM AUTHOR]

Methods have been proposed for computational-experimental determination of thermophysical characteristics of gradient materials whose functional properties change systematically as a function of spatial coordinates. An algorithm has been proposed for calculating thermophysical characteristics of gradient materials, whose properties change in one direction. Experimental investigations have been conducted into specimens of Cerablanket fibrous industrial material made up of layers of various density. [ABSTRACT FROM AUTHOR]

Combined theoretical-experimental investigations of the processes of heat transfer in materials of complex structure are conducted for the case where it is impossible to measure the state of the system at internal points. The problem of simultaneous determination of the thermal conductivity of a nontransparent material and of the coefficient of its heat exchange with the external medium and with the heat flux absorbed by the material has been solved. [ABSTRACT FROM AUTHOR]

The present work is devoted to verification of the procedure of determining the thermophysical characteristics of highly porous fibrous thermoprotective materials under conditions resembling real ones. For creating conditions close to operational ones, temperature regimes of heating from 300 to 1200 K in vacuum at a pressure within the range 7.0·10–5–9.0·10–5 bar were realized in the process of experiment. The thermophysical characteristics were calculated using the data of temperature measurements at the internal points of thermoprotective material samples. A comparative analysis of the results obtained with the use of different quantities of thermocouples mounted in the samples is given. The computational algorithm for processing experimental data is based on the solution of the inverse heat transfer problem by the method of iteration regularization. [ABSTRACT FROM AUTHOR]

An analysis has been made of the problem of identification of mathematical heat-transfer models with lumped parameters that have a nonunique solution. The authors have investigated the possibility of restoring conditionally the uniqueness of a solution to such a problem with supplementary conditions for the selection of solutions in the form of linearly independent time functions of temperature that can be obtained in one experiment with relevant designing, Consideration has been given to the applicability of iteration-regularization methods with a vector regularization parameter to identifying a full set of functions of a thermal-state matrix of mathematical models with lumped parameters. On the basis of computational experiments, the capabilities of a variational principle of selection of solutions for conditionally correct identification problems have been demonstrated. [ABSTRACT FROM AUTHOR]

At present, the angular position of small spacecraft is determined using solar sensors, magnetometers, and angular-velocity pickups as a rule, whereas star trackers are used for complicated problems requiring high accuracy. Each individual system has its advantages and disadvantages. Therefore, combined systems are used to avoid them. Also, to improve the reliability of a craft, recourse to redundancy of the sensors must be had. All these subtleties result in the increased materials intensity and in the complicated mutual synchronization of the systems. In the present work, the authors analyze the possibilities of creating and using the main or alternative orientation system for small spacecraft with radiative-heat-flux sensors on the basis of the methodology of inverse heat-transfer problems. This system will allow checking and correcting the craft's angular position. [ABSTRACT FROM AUTHOR]

We have investigated the problem of identifying mathematical heat exchange models with lumped parameters for the computing-experimental method for thermal trial of space vehicles on the ground. We have developed a modified variational method of iteration regularization of the solution of identification problems and a combined method for determining the regularization parameter on the basis of minimizing the smoothing functional and the functional-residual of temperature for solving nonlinear problems. The mathematical models of individual systems of thermoregulation of space vehicles have been identified. [ABSTRACT FROM AUTHOR]

In designing heat-loaded structural elements of descent modules, information on heat loads (heat fluxes and surface temperatures) throughout the active stage of flight in the atmosphere is primary. When a spacecraft moves with hypersonic velocities, the level of temperature and processes occurring on the thermal-protection surface does not necessarily make it possible to use traditional tools to measure heat loads. In this case an alternative to direct measurements is provided by determining heat loads from the data of temperature measurements at several internal points of the structural elements of the thermal protection. The objective of the present work is to develop and evaluate sensors for measurement of the heat loading of thermal protection coatings of today′s descent modules. In the paper, consideration is given to heat-flux sensors for two classes of thermal protection materials: nondestructible fibrous materials and thermally destructible polymers. [ABSTRACT FROM AUTHOR]