I've heard that aerogel [0] is an alternative. Don't know enough details to elaborate. I guess it's way more expensive than helium, at least for now. [0]: http

I've heard that aerogel [0] is an alternative. Don't know enough details to elaborate. I guess it's way more expensive than helium, at least for now. [0]: https://www.nasa.gov/topics/technology/features/aerogels.html https://www.nasa.gov/topics/technology/features/aerogels.htm...