[hn_throwaway_99]

> but the economics still don't work out. One day, they will.

This sounds like magical thinking to me. Supersonic travel will always be at a huge cost disadvantage to conventional airlines, and for the vast majority of people the benefits are not there.

I'm more curious about optical computing. I didn't realize there were costs in optical computing that make it fundamentally (i.e. at a physics level) more expensive than electronic computing; I thought the issue was mainly just that there was already over a half a century invested in electronic computing. What are the aspects of optical computing that make it inherently more expensive?