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Reading about aerogels again, they seem to be some of the greatest thermal insulators ever made, which is weird because they are so light. When I read about a very lightweight material with very high efficiency in something, I immediately think spaceflight.

So here it is. Can aerogels be used for ablative heatshields? It could be re-entry heatshields. It could be ablative material placed inside an engine chamber, throat, or nozzle, to help keep the walls cool. Is any of this possible?

As an important starting point tho, what is normally the material used for ablative heatshielding inside rocket engines?

I'm not a materials scientist and don't know how to figure out all the properties needed to "know" something. Maybe someone here can lend a hand.

Deer Hunter
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DrZ214
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  • Wondering if it would make sense for the question or answer to address the comparison between aerogels and thermal tiles of the type used on the Space Shuttle. Were Space Shuttle tiles a sort of high density aerogel? They were designed to insulate, withstand the aerodynamic forces encountered in launch, re-entry, and landing, and be durable in re-entry conditions (not ablate). So, would an aerogel modified to withstand re-entry forces simply amount to a reproduction of Space Shuttle tile technology? – Anthony X Jun 07 '15 at 23:02
  • I always had the impression that aerogel was very fragile (don't quote me on this), so it would make an excellent insulator, but not a strong heatshield. – 2012rcampion Jun 08 '15 at 01:28
  • @2012rcampion yea i have the same impression. However, the shuttle tiles were also pretty fragile in the sense of impact resistance, so it might still be possible to use as a heat shield. Shuttle tiles are one thing, but inside a combustion chamber, I think we won't have to worry about any foreign debris impacts. – DrZ214 Jun 08 '15 at 02:11
  • @AnthonyX Good question, but we're not even sure yet if an aerogel modified to withstand re-entry is necessary. They might be able to withstand it without modifications. My impression is that they are brittle and have little impact resistance, but can handle huge loads spread out across their surface---in other words, high pressure. – DrZ214 Jun 08 '15 at 02:18
  • You should ask the question about common ablatives in a new post and avoid broadening the question on the fly. Voting to put on hold for the time being. – Deer Hunter Jun 08 '15 at 07:46

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No. The glass would just melt and disappear in very short order if it were the first thing presented to the flow. I'd love to see the arc jet test of that. I bet that the survival time of the aerogel would be measured in milliseconds.

Maybe it could be an insulator between a usable heat shield and the structure to reduce the temperature the structure sees, but there would need to be passthroughs to carry the load since the aerogel would just crush under the load. The passthroughs would be thermal shorts that might negate the benefit of the aerogel as an insulator.

Mark Adler
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  • maybe i should have started with: what is the normal ablative heatshield used in rocket engine chambers, throats, and nozzles? I added that to my OP. Also, I like your idea of an insulator around the combustion chamber, but the pressure load would be borne by the tensile strength of the spherical metal combustion chamber, not the outside aerogel, right? – DrZ214 Jun 08 '15 at 05:07
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    @MarkAdler, what about aerogel made from graphene? Wouldn't that be strong enough? (complete layman here) – Vedant Chandra Jun 08 '15 at 05:35