Magical Thermal Insulation Material - Aerogel
Since 1975, the United States has successfully conducted 7 missions on the surface of Mars, namely the "Pirates" 1 and "Pirates 2" Mars Surveyors, the Mars Pathfinder, the Mars Rover, the Phoenix Lander and the Mars Science laboratory. From Mars Pathfinder to Mars Laboratory, the United States has gone through three generations of navigators, namely the "Pathfinder" tour of Mars Pathfinder, the "Courage" and the "Opportunity" and the "Curiosity".
However, the surface temperature of Mars is much lower than the Earth, the lowest temperature is about -123 ℃. In such a low temperature environment, the detector how to solve the insulation problem?
Viking lander thermal control system for thermal control of the equipment within the tank isothermal, all the equipment installed in the center cabin equipment board, the use of fiberglass insulation for insulation, the formation of equipment and cabin environment Thermal insulation material between.
"Sojourn" rover thermal control system uses a centralized arrangement of unified thermal management design. All of the equipment in the cabin is centrally installed in the electronic warmer (WEB), and the nano-airgel and the fiberglass board are coated on the outside of the electronic warmer to thermally isolate the electronic warmer from the external environment.
Mars rover also uses the insulation structure shown in the figure, the use of aerogels in the structural board.
However, multi-layer insulation components only have a good thermal insulation properties in a vacuum, the Mars surface of about 800Pa carbon dioxide gas environment, its thermal insulation effect is lost. This is why rovers use airgel insulation.
So what is the magic of aerogel?
The first is good thermal insulation. The thermal conductivity of polytetrafluoroethylene for thermal insulation is 0.27 W / mK, while the thermal conductivity of nano-aerogel is generally 0.02 W / mK, only 1/13 of that of polytetrafluoroethylene. This is because the small gap in the atmospheric environment stagnates the CO2 gas, so convection heat does not develop, the microstructure of aerogel is relatively thin, heat transfer path is long, reducing the heat conductivity. Aerogel is therefore known as a magical thermal insulation material.
The second is light weight. The density of iron is 7.8 × 103 kg / m3, that is to say 1 cubic meter of iron, weighing up to 7.8 tons; the density of the air is 1.29 kg / m3, that is to say 1 cubic meter of air, weighing 1.29 kg. The density of aerogel is 15kg / m3, which is about 12 times that of air. The liquid in gel during aerogel production is replaced by gas, resulting in a large number of voids and structural cells. Therefore, it has very low density. This is why aerogel is called frozen smoke or solid air.
The third is stable performance. Aerogels are available in a wide variety of materials. The aerogel components used in rovers are silica. In space radiation environments, they are highly resistant to high-energy radiation in space and do not degrade in performance, making them particularly suitable for Space use.
In fact, aerogels are not only used for thermal insulation material. In the latest research, the adsorption capacity of aerogel powders has been developed and utilized for sewage treatment.