I am looking for paint or in an extreme case a coating material on inAtmosphere flying object to reduce the heat dissipation caused by aerodynamic heating for a relatively longer period, considering the speed range of upper hypersonic range.
Dear Shantanu P. Gawande, this heating is due to friction. There is exist paints based on drag reducing compounds such as polymers. Some polyacrylamides have such a feature and they are used for decades in planes and ships. My Regards
Dear Shantanu P. Gawande, these bibliographic material I Guess worth to read. My Regards
https://www.researchgate.net/publication/235149328_Permanent-Change_Thermal_Paints_for_Hypersonic_Flight-Test
https://www.researchgate.net/publication/269247584_Development_of_Temperature-Sensitive_Paint_with_High_Performance_and_Responsibility_for_Aerodynamic_Heating_Measurement
https://www.nature.com/articles/srep38459
At the speeds you cite (upper hypersonic), most of the heating comes from the shock wave heating just ahead of the body which creates a high temperature gas that surrounds the body and convectively raises the temperatures to very high values. It is essential that the surface is smooth and aerodynamic, which I assume your know. Given that, the characteristics of the coating that would be most effective are, in approximate order of importance,
1. anything that can ablate or transpire some material from or through the surface. I am not sure of the application, but if you can pump, vaporize, or ablate any substance through or from the surface, that will be more effective than almost anything else.
2. something that radiates light (e.g. something black in the near IR and surrounding regions), assuming the body is in an environment that is much cooler than its surface.
3. something that has a low thermal conductivity, which usually means it has high porosity with small pores.
Thank you Larry L. Baxter for your so valuable insight, I actually have consideration of through surface but I was thinking strong adhesive paint will be another layer of protection. If you have something in mind do tell me.
Thermal Coating Paints are being used for turbine blades by all turbine manufacturers including Siemens, GE, etc. They have very low thermal conductivity. However, the very small thickness of paints when applied to metal, limits the resistance to the conduction heat transfer.
Shantanu P. Gawande , in addition to the suggested options, you may look at an array of ceramic coatings. Ceramic Matrix Composites (CMC) and Ultra-High-Temperature-Ceramics (UHTC) are candidate materials for heat shields on hypersonic, re-entry vehicles. These materials can be made porous as well, making them a potential injector material for the purpose of transpiration cooling, which can further reduce surface heating. Feel free to look at the literature on my profile, which has relevant references on this topic.
https://iopscience.iop.org/article/10.1088/1757-899X/1114/1/012051/meta
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