Yeah, I've always wondered about aerogel airships.
Make a lot, cover with a skin that won't leak, fill from the bottom. Hydrogen gas is less leaky that helium (as He is monatomic).
So, would the aerogel slow the rate of combustion if there was an incendiary accident at a puncture site due to there being a less of an interface with the atmospheric oxygen compared to a balloon? Well, probably not with a paper aerogel, say a silicon one.
And how would the reaction progress through the aerogel? If it was slow enough/not fatally toxic it would make the hydrogen gas safe.
"Attention passengers, we have a fire in the top forward gelsac, we will be landing shortly. Passengers will then disembark into inflatable life-rafts."
Any physicists care to comment?