Development of the passive thermal control systems with heat pipes for the typical tasks of space instrument-making
The equalizations of thermal balance for the system «space vehicle – device – thermal control system – space environment» for a thermosensitive device taking into account heat transmission , realized by heat pipes, are theoretically grounded. On the basis of analysis of these equalizations for the boundary conditions of device function a new thermal conception of construction of the effective thermal control system of class of scientific devices, which have not own heat generation is offered and experimentally researched. The system is passive and uses for functioning only the heat of the external source – the Sun. The use of the offered principle allows to narrow the range of change of the device temperature to 10 – 20 K at a temperature level of 290 K at the change of mounting place temperature of 253 – 323 K in the range of the solar constant 500 – 1400 W/m2 at the possible maneuvers of space vehicle in a angle of 20 degrees relatively to direction to the Sun.
A new thermal scheme of the passive radiation thermal control system is created for cooling of receivers of radiation of the scientific optical systems at a temperature level of 213 – 243 K. Proposed principle of organization of heat exchange of the passive radiation thermal control system supposes thermal connection of a few radiators, oriented in the space by defined way. The function of thermal conductor is executed by heat pipes with diode properties. Change of thermal resistance of thermodiodes from the direct mode (Rdir) to reverse (Rrev) one and vice versa takes place autonomously. At the values Rrev/Rdir > 50 – 100 K/W the region of functioning of the thermal control system widens on the value of absorbed heat flux in ten times at arbitrary placing of device relatively to sunbeams on orbits from the Earth to the Venus. The given system allows to stabilize the temperature of receiver at a temperature level of 233 K at external disturbances, namely change of solar constant and temperatures of mounting places.
The methods of research of the systems with thermal pipes in conditions imitating operating are developed.
With the use of the developed mathematical algorithm the results of 10-years-old successful exploitation on the near-Earth orbit of the thermal control system on heat pipes of the NTUU “KPI” development on the German microsatellite BIRD are generalized.