Editing Radiative cooling (section)

===Heat shields===
[[High emissivity coatings]] that facilitate radiative cooling may be used in [[Heat shield |reusable thermal protection systems]] (RTPS) in spacecraft and [[hypersonic]] aircraft. In such heat shields a high emissivity material, such as [[molybdenum disilicide]] (MoSi<sub>2</sub>) is applied on a thermally insulating ceramic substrate.<ref name="Shao2019"/> In such heat shields high levels of total [[emissivity]], typically in the range 0.8 - 0.9, need to be maintained across a range of high temperatures. [[Planck's law]] dictates that at higher temperatures the radiative emission peak shifts to lower wavelengths (higher frequencies), influencing material selection as a function of operating temperature. In addition to effective radiative cooling, radiative thermal protection systems should provide damage tolerance and may incorporate self-healing functions through the formation of a viscous glass at high temperatures.