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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?

Dagelf
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    If the heat shield is inside, what protects the outside? – Jon Custer Dec 02 '23 at 16:14
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    @JonCuster ... if the heat shield is inside, it rapidly becomes the outside. – Woody Dec 02 '23 at 16:26
  • Perhaps the idea is that heat shield ingredients would be stored inside, and then expelled to form the actual heat shield before or during reentry? – Charles Staats Dec 02 '23 at 16:33
  • @Woody - well, yes, that was the implication… – Jon Custer Dec 02 '23 at 16:41
  • @JonCuster ... in X-speak that would be Rapid Unplanned Ablation – Woody Dec 02 '23 at 19:00
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    normally we ask people to only ask one question at a time, but that's a hell of a second question – Erin Anne Dec 02 '23 at 20:59
  • @Woody - or, ‘fire all the engineers involved’ – Jon Custer Dec 03 '23 at 00:34
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    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. – Steve Pemberton Dec 03 '23 at 07:11
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    The most advanced rocket engines can only withstand the heat of operation because they are actively cooled by circulating cryogenic fuel through them. SpaceX considered doing something similar with re-entry cooling through the skin of the spacecraft, but it turns out it would take so much fuel to protect even heat-resistant stainless steel on re-entry that it would be impractical. – antlersoft Dec 03 '23 at 17:47
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    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. – Organic Marble Dec 03 '23 at 21:57
  • Building and attaching a non ablative heat shield as a single piece without any tiles will be very difficult if not impossible. – Uwe Dec 05 '23 at 16:33
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    I assume you mean ceramic tiles. Tiles are just a form factor, not a material. – Darth Pseudonym Dec 06 '23 at 21:01

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