5.4 Design Methodology
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of the lunar lander. The two important parameters of thermal control coating were
the solar absorptance α S and the infrared hemispherical emissivity ε H , which respectively represented the absorption ratio of solar radiation energy and the ability to
radiate energy.
There are many kinds of thermal control coatings, which can be classified into
external thermal control coatings and internal thermal control coatings. For the lunar
lander, external thermal control coating should generally have the characteristics of
low solar absorption ratio and high infrared emissivity. In addition, the effects of
lunar dust deposition on performance of thermal control coatings were different.
It was generally believed that the effect on the type of vacuum deposition thermal
coating was smaller than that of thermal paint. Based on above factors above, thermal
control coating of vacuum deposition was selected for external instruments. Available
products included glass second surface mirror of vacuum deposition, or flexible
thin-film second surface mirror of vacuum deposition which could be easily installed.
The spray-type thermal control coating was generally used for thermal control
coating in the module including the surface of structural plates and instruments, whose infrared hemisphere emissivity was high to improve the temperature
uniformity in the module.
When thermal control coating was determined, beside the α S and ε H , other factors
such as adaptability to temperature and environment should also be considered.
For example, for RHU, its temperature was relatively higher under high temperature conditions than the normal operating temperature of some coatings. Therefore,
thermal control coating with high temperature should be selected.
5. Selection of Multilayer Insulation
The multilayer insulation is composed of a high-reflectance screen and spacers of
low thermal conductivity laminated alternately. The layers reflect the radiation heat
flow to form a very high thermal resistance, which is a good insulation under vacuum
conditions. Because of its light weight, it is ideal for spacecraft.
According to the difference in application environment, multilayer insulation is
classified into low-temperature, medium-temperature and high-temperature multilayer thermal insulation. Different types of multilayer thermal insulation differ in the
highest temperature that the reflective screen and spacer materials can endure. The
reflectors and spacers of typical low-temperature multi-layer insulation are doublesided aluminum-plated polyester film and mesh respectively, which can be used in
environment temperature below 150 °C. The reflective screen and spacers of mediumtemperature multi-layer insulation are polyimide aluminum film and glass fiber cloth,
which can be used in environment temperature below 350 °C. The reflective screen
and spacers of high-temperature multilayer insulation assembly are nickel foil or
other metal foil and glass fiber cloth, which can be used in environment temperatures
below 900 °C.
Low-temperature multi-layer insulation was generally used for insulation on
surfaces and instruments in the modules of the lunar lander. Medium-temperature and
high-temperature multi-layer insulation were generally used for high-temperature
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of the lunar lander. The two important parameters of thermal control coating were
the solar absorptance α S and the infrared hemispherical emissivity ε H , which respectively represented the absorption ratio of solar radiation energy and the ability to
radiate energy.
There are many kinds of thermal control coatings, which can be classified into
external thermal control coatings and internal thermal control coatings. For the lunar
lander, external thermal control coating should generally have the characteristics of
low solar absorption ratio and high infrared emissivity. In addition, the effects of
lunar dust deposition on performance of thermal control coatings were different.
It was generally believed that the effect on the type of vacuum deposition thermal
coating was smaller than that of thermal paint. Based on above factors above, thermal
control coating of vacuum deposition was selected for external instruments. Available
products included glass second surface mirror of vacuum deposition, or flexible
thin-film second surface mirror of vacuum deposition which could be easily installed.
The spray-type thermal control coating was generally used for thermal control
coating in the module including the surface of structural plates and instruments, whose infrared hemisphere emissivity was high to improve the temperature
uniformity in the module.
When thermal control coating was determined, beside the α S and ε H , other factors
such as adaptability to temperature and environment should also be considered.
For example, for RHU, its temperature was relatively higher under high temperature conditions than the normal operating temperature of some coatings. Therefore,
thermal control coating with high temperature should be selected.
5. Selection of Multilayer Insulation
The multilayer insulation is composed of a high-reflectance screen and spacers of
low thermal conductivity laminated alternately. The layers reflect the radiation heat
flow to form a very high thermal resistance, which is a good insulation under vacuum
conditions. Because of its light weight, it is ideal for spacecraft.
According to the difference in application environment, multilayer insulation is
classified into low-temperature, medium-temperature and high-temperature multilayer thermal insulation. Different types of multilayer thermal insulation differ in the
highest temperature that the reflective screen and spacer materials can endure. The
reflectors and spacers of typical low-temperature multi-layer insulation are doublesided aluminum-plated polyester film and mesh respectively, which can be used in
environment temperature below 150 °C. The reflective screen and spacers of mediumtemperature multi-layer insulation are polyimide aluminum film and glass fiber cloth,
which can be used in environment temperature below 350 °C. The reflective screen
and spacers of high-temperature multilayer insulation assembly are nickel foil or
other metal foil and glass fiber cloth, which can be used in environment temperatures
below 900 °C.
Low-temperature multi-layer insulation was generally used for insulation on
surfaces and instruments in the modules of the lunar lander. Medium-temperature and
high-temperature multi-layer insulation were generally used for high-temperature