The proof of concept for space travel was NASA, the ESA, the CSA, RKA, etc. plus all science fiction plus space camps plus parabolic microgravity flights plus preselling seats.

In their case there are many rapid app builders so it isn't crazy talk to enter that market. What is crazy talk is they haven't entered the market but are forming up on the beachhead (waiting for what?) and (critically) applying for YC before they have tested the market.