The paper considers two ways of maintaining temperature of the instrumentation equipment: using the heat pipes equipped with thermoelectric cooling plate on the compensation cavity and the control valve installed at the outlet of the evaporating radiator. Since the temperature of the contour heat pipe is mainly controlled by the temperature of the compensation cavity positioned behind the evaporator, maintaining the high-precision temperature mode of this device is an urgent task for the entire spacecraft thermal regime. In the first method, the evaporating radiator is heated or cooled depending on the plate device polarity. In the second, the compensation chamber temperature could be changed using the steam supplied to the compensation cavity by a regulator installed at the outlet of the evaporator. Temperature control using a valve is due to the fact that the steam of the working fluid enters the bellows under pressure, which depends on the temperature in the evaporator. Pressure difference between steam and gas causes the bellows to contract and expand, while the valve associated with it partially closes the openings in the housing, through which the steam enters the condenser and the compensation cavity. Detailed description of these devices operation is provided, and thermal hydraulic models of the contour heat pipes equipped with these two devices are compiled.

Growing heat release in spacecraft accompanied by simultaneous increase in its amount set the task of developing thermal control systems using the two-phase boiling coolant. It accumulates heat in the form of latent vaporization heat making it possible to transfer much larger amount of heat per the coolant unit mass flow rate than at using a single-phase coolant. In addition, introduction of heat transfer at boiling allows maintaining the object temperature in almost the entire circuit close to the boiling temperature of the selected coolant. All heat transfer processes that occur, when the substance aggregation state changes, are much more intensive than with the conventional convective heat transfer; therefore, the mass of heat exchangers, fittings and control elements of the two-phase circuit would be significantly lower than their mass in a single-phase coolant circuit. Capillary or mechanical pumps should pump the coolant in two-phase systems to ensure the thermal regime. At high power, it is more advantageous to use the two-phase boiling coolant with a mechanical pump. Creation of thermal control systems based on the two-phase circuit should be preceded by elaboration of an adequate mathematical model of the two-phase boiling coolant. Mathematical model is proposed that could be used to analyze operation of the two-phase boiling coolant and calculate hydrodynamic, heat and mass transfer processes.

The paper considers issues of calculating the thermal regime of a spacecraft on the Moon surface. A method for calculating the external radiant fluxes is provided for this case. Geographical position of the spacecraft on the Moon surface and the initial date were set as the initial data for calculation. The spacecraft thermal regime was calculated by the method of thermal balances on the Moon surface taking into account the specular-diffuse heat transfer for cases, where the nature of the outer surface reflection of the screen-vacuum thermal insulation (SVTI) is diffuse or specular. The calculation showed that the nature of reflection (specular or diffuse) of the SVTI outer surface for the case under consideration was not affecting the SVTI surface temperature and the spacecraft temperature, and its operating temperature ranged from 80 to 400 K.

At present, there exists a trend for spacefaring countries to use methane as fuel for the first stages of launch vehicles. Russia is currently developing a promising launch vehicle known as Amur LNG. However, due to methane being a hazardous (flammable and explosive) substance, it is poorly suited for fuel tank strength tests conducted using existing equipment. In this regard, we face an urgent issue of developing a safe method for simulating liquid methane temperature during strength testing of methane tanks. We propose to cool the tank with a nitrogen vapour-liquid mixture. To estimate cooling time for a cryogenic tank treated with a nitrogen vapour-liquid mixture as per the method proposed, along with determining the amount of refrigerant to be used, we solved its thermal state problem using the method of isothermal nodes. This approach may also be used for oxygen tanks.