A team of researchers, including the University of Southampton, has developed a new technology that could cause a significant change for a spacecraft or satellite.
Metamaterial optical solar reflectors (meta-OSR) are the coatings of the first surface on the outside of a spacecraft, designed to effectively radiate infrared heat and reflect most of the optical solar spectrum.
For a satellite or spacecraft, OSRs play a crucial role in the thermal control of the system. Attached to the outer skin of the radiator panels, the OSRs are designed to repel solar radiation and dissipate the heat generated on board.
OSRs are usually made of quartz plates that combine thermo-optical properties with the ability to resist the environment in space.
However, quartz tiles are heavy and brittle, significantly increase mounting and launching costs, and can not be applied to curved surfaces. Other commercial solutions based on polymer sheets suffer rapid degradation of performance and therefore are not suitable for missions that last more than three or five years.
The team demonstrated that a new meta-OSR coating is enabled by the use of metal oxide, a material commonly used for transparent electrical contacts, which, in this case, is modeled in a metamaterial with very strong infrared emissivity at the time which retains a low absorption of the solar spectrum.
The team also demonstrated an "intelligent" radiator based on its metamaterial design, which allows adjusting the radiative cooling of the spacecraft using another type of metal oxide.
Prof. Otto Muskens, of the University of Southampton and principal investigator of the study, said: "The meta-OSR technology is based entirely on durable and space-approved inorganic coatings, which can be applied to thin-film flexible substances with the potential to develop as a new technological solution
"Since the assembly and launch costs of OSR are several tens of thousands of US dollars per square meter, even small improvements in weight reduction can make a significant change in the space industry."
Backed by a two-year Horizon 2020 space technology project, the University of Southampton is a member of the META-REFLECTOR consortium, which also includes the Italian research center Centro Ricerche Elettro-Ottiche (CREO), the Danish developer of nanoprints NIL Technology and Thales Alenia Space.
the work of the consortium appears in ACS Photonics in two reports: & # 39; Smart Optical Solar Reflector based on Thermochromic Metamaterial VO2 & # 39; and & # 39; Metasurface optical solar reflectors using AZO transparent conductive oxides for radiative cooling of spacecraft & # 39;
Dr. Kai Sun, from the University of Southampton, added: "All the partners have actively collaborated to ensure that the design and manufacture are suitable for transfer to mass production, it is an exceptional research experience to transfer the idea of cutting-edge research. to a commercial product. "
The team is currently working on extending prototypes to larger areas through processes developed by NIL Technology, while preparing the first tests of metamaterials in space.
Dr. Sandro Mengali, from CREO who supported the study, said: "Passive control of thermal emissivity is important to preserve precious heat during start-up and eclipses and to maintain the temperature stability of the spacecraft."
"Currently, the thermal emissivity control requires bulky mechanical components such as blinds, which are extremely expensive and prone to failure, which represents a significant risk to the missions.
"Smart meta-OSR technology will offer a valuable new tool for spacecraft thermal engineers, of particular importance to the lightweight segment of the satellite market."
Image: preparation of the Parker solar probe for space
More information about the META-REFLECTOR consortium is available online: www.meta-reflector.eu/index.htm
Kai Sun et al. Smart Optical Solar Reflector based on Thermochromic Metamaterial VO2, ACS Photonics (2018). DOI: 10.1021 / acsphotonics.8b00119
Kai Sun et al. Optical solar reflectors Metasurface using AZO transparent conductive oxides for radiative cooling of spacecraft, ACS Photonics (2017). DOI: 10.1021 / acsphotonics.7b00991