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Are tiles that much more cost effective as a thermal protection system?

What other novel methods have been tried? The obvious issues seem to be different thermal properties and rigidity and how to attach them, and weight.

Non-ablatives/erosives are of course required for reuse. After some research I found fibre-glass with novel resins (Mercury reentry heat shields; material composition, manufacturing process and explanation of all those concentric ridges?), reinforced carbon, glass and aerogel as alternatives.

First question: Which novel materials have been conceived and if not tested yet, what technical challenges prevented that? Eg. Fibreglass blankets (does it even have to be attached?), or paints and resins containing things like aerogels or glass, or simply steels with higher temperature tolerances - what are the limits here?

Why not use the existing rocket engines, that seem to be able to take much more heat, as heatshield?

Follow-up question moved here: Why does the heatshield have to be on the outside?

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    $\begingroup$ If the heat shield is inside, what protects the outside? $\endgroup$
    – Jon Custer
    Commented Dec 2, 2023 at 16:14
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    $\begingroup$ @JonCuster ... if the heat shield is inside, it rapidly becomes the outside. $\endgroup$
    – Woody
    Commented Dec 2, 2023 at 16:26
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    $\begingroup$ normally we ask people to only ask one question at a time, but that's a hell of a second question $\endgroup$
    – Erin Anne
    Commented Dec 2, 2023 at 20:59
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    $\begingroup$ Regarding the second question (heat shield on the inside) you are probably thinking in terms of insulation, but that's not the main job of the heat shield. The heat shield's job is to reflect heat as well as emit heat that it has absorbed. The most visual example of this are ablative heat shields which literally carry the heat away from the spacecraft. Non-ablative heat shields attempt to do the same thing in terms of getting rid of heat, but without losing material. But they need to be on the outside to do their job effectively. $\endgroup$ Commented Dec 3, 2023 at 7:11
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    $\begingroup$ This kind of "why" question always boils down to tradeoffs. What system weighs more? What system costs more? What system meets the reuse requirements (if any)? Everything you've mentioned has been thought of and studied to death (you don't mention active cooling, which has also been studied to death). If your alternatives were not used, they were not the best choice for a given system, given the tradeoffs. If you have a specific question about a particular system, it could probably be answered, otherwise the answer is tradeoffs. For the specific case of tiles: light weight and reusable. $\endgroup$ Commented Dec 3, 2023 at 21:57

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