A new concept of space radiator for thermal control had its patent granted to INPE on October 6, 2020. Registered with the National Institute of Industrial Property (INPI) under the number PI 1003427-7 the patent is entitled TWO STAGE RADIATOR WITH VARIABLE EMITANCE FOR VACUUM USE. The radiator, called VESPAR (Variable Emittance SPAce Radiator), is of the variable emission type, that is, it automatically modifies its ability to emit heat into space according to the need. That is, when the thermal dissipation inside the satellite increases, the radiator increases the heat radiated into space, not allowing the equipment’s temperature to rise. In a cold condition, the radiator reduces the emission of heat into the space, maintaining the appropriate temperature of the equipment, avoiding, or significantly reducing, the need to use heaters. VESPAR operates completely passively, without moving parts and without the need for temperature sensors.
A satellite, seen from the outside, has most of its surface covered with super-insulating blankets (MLI – Multi-Layer Insulation). They have a yellowish visual characteristic, easily recognized in satellite photos. MLIs prevent uncontrolled heat exchange with the orbital environment, the effective temperature of which can vary widely, approximately between -270 ° C and 230 ° C. However, any equipment when it works, dissipates heat. That is why it is not possible to isolate the satellite completely, covering its entire external area with MLI, which would cause the internal temperature to rise excessively. In order to prevent this overheating, the thermal project includes radiation windows: space radiators. They throw excess heat into space and thus provide the necessary cooling for the internal equipment. These radiators are generally flat, rectangular surfaces, located on the outer faces of the satellite, covered with material with high emissivity and high reflectivity to the incident solar flux (such as white paint or OSR – solar optical reflector). They can be recognized in satellite photos as white or mirrored areas, usually surrounded by areas covered with MLI blankets.
A characteristic of these conventional radiators is that their emissive power is uncontrolled which can lead, under cold conditions, to overcooling equipment inside the satellite. In order to prevent these situations, electric heaters are used, but they consume energy from the satellite, in addition to increasing the complexity of thermal control. covered with material with high emissivity and high reflectivity to the incident solar flux (such as white paint or OSR – solar optical reflector). They can be recognized in satellite photos as white or mirrored areas, usually surrounded by areas covered with MLI blankets. A characteristic of these conventional radiators is that their emissive power is uncontrolled which can lead, under cold conditions, to overcooling equipment inside the satellite. In order to prevent these situations, electric heaters are used, but they consume energy from the satellite, in addition to increasing the complexity of thermal control. covered with material with high emissivity and high reflectivity to the incident solar flux (such as white paint or OSR – solar optical reflector). They can be recognized in satellite photos as white or mirrored areas, usually surrounded by areas covered with MLI blankets.
A characteristic of these conventional radiators is that their emissive power is uncontrolled which can lead, under cold conditions, to overcooling equipment inside the satellite. In order to prevent these situations, electric heaters are used, but they consume energy from the satellite, in addition to increasing the complexity of thermal control. They can be recognized in satellite photos as white or mirrored areas, usually surrounded by areas covered with MLI blankets. A characteristic of these conventional radiators is that their emissive power is uncontrolled which can lead, under cold conditions, to overcooling equipment inside the satellite. In order to prevent these situations, electric heaters are used, but they consume energy from the satellite, in addition to increasing the complexity of thermal control. They can be recognized in satellite photos as white or mirrored areas, usually surrounded by areas covered with MLI blankets.
A characteristic of these conventional radiators is that their emissive power is uncontrolled which can lead, under cold conditions, to overcooling equipment inside the satellite. In order to prevent these situations, electric heaters are used, but they consume energy from the satellite, in addition to increasing the complexity of thermal control. VESPAR consists of two stages that are thermally coupled to each other by exchanging heat with radiation, using fins positioned on their internal surfaces, as shown schematically in Figure 1. The fins must be covered with material of variable emissivity. The internal stage is mounted on an external surface of the satellite, while the external stage has its external surface exposed to space.
Figure 1 – Illustration of the internal and external stages of VESPAR, for a trapezoidal configuration. The internal surfaces of the radiator must be covered with material of variable emissivity.(Source: www.inpe.br)
A model of development of the radiator was built and its concept validated experimentally in thermo-vacuum tests carried out at the Integration and Testing Laboratory (LIT) of INPE. Figure 2 shows the development model inside a thermal vacuum chamber at LIT.
Figure 2 – Development model of VESPAR inside a vacuum-thermal chamber, at LIT / INPE.(Source: www.inpe.br)
The inventors Valeri Vlassov and Fabiano L. de Sousa, from the Division of Space Mechanics and Control (DIMEC) at INPE, believe that there are many possibilities for using VESPAR, from the customization of its concept for different space applications. It can be adapted to be used in both large and small satellites, and potentially even in cubesats. In this case, in addition to its thermal function, it can contribute to increase the satellite’s reliability, providing additional protection to the internal electronics against cosmic radiation. It could also be adapted to receive solar cells on its external face, incorporating itself into the energy subsystem of a cubesat. Information and guidance on the procedures for submitting an intellectual creation for protection at INPI – National Institute of Industrial Property, whether it be a patent, computer program, brand, industrial design, etc., can be obtained from the Project Management and Technological Innovation Coordination – INPE COGPI. Interested parties are requested to contact Mr. Renato Henrique Ferreira Branco and / or Mr. João Ávila.
