I'm not an aerospace engineer, so don't read too much into this, but: In James Fallows' China Airborne, there's a paragraph or so where he talks about how building a modern airliner is harder than building a rocket ship. Roughly it's because 1) rocket ships are allowed to fail on occasion and 2) planes are subject to constant use and are not subject to the kind of preflight inspections rockets are.
In the case of SpaceX, consider their last launch failure. The general consensus seemed to be "well, rockets are really hard. And it was the strut manufacturer's fault to some extent. They'll do better next time, and they're still changing the world. Anyway, SpaceX rockets are 4x cheaper than any competitor so even with the occasional launch failure it's still the best option!"
Can you imagine the reaction today if e.g. a Boeing plane blew up on launch? In fact, recall all the criticism Boeing received after issues with the 787's batteries...
But again, I certifiably don't really know. Someone could write about energy requirements and wet/dry mass and how thin rocket skins are and aerodynamic forces and easily convince me rockets are harder.
Even in the case of rockets, once you work out all the kinks, you can get very high reliability. When was the last time you heard a Soyuz rocket fail or one of ULA's launch vehicles.
Just my guess: You can blow up a rocket from time to time and it's OK. Even if it's manned it's more acceptable for astronauts to die than civilian passengers.
Building a totally new passenger airplane just seems a hugely complex thing. Getting it to fly is one thing but you need safety, long-term maintenance, fuel efficiency, international regulation and many other factors.
At least from the outside a rocket looks simpler to me.
We have a lot more experience building planes of various types that can fly. This is well understood science. The difficulty with rockets are the razor thin margins and the extreme conditions it needs to handle.
The science is probably well understood. But getting a plane approved in different markets must be a massive undertaking. I work for a medical device company and even getting a simple device to market takes a huge amount of money, effort and experience. Now scale that up a few hundred times and you have something that only somebody like Boeing, Airbus or a state sponsored company can do. Add to that changing oil prices and other factors you need a lot of money to finish that effort. Virgin is not even flying their Spaceship Two yet and that certainly is a much simpler development.
Don't get me wrong. I would love to see them succeed but it seems really, really, really hard. Much harder than anything any of the current unicorns has achieved.
It seems to me that most of your doubts stem from the financing side of things and not really from the technical ones. That's a valid point.
From a technical POV, I don't think this is anywhere near unicorn territory. In fact, I think they are aiming too low. I'd ideally want a supersonic plane that is quiet enough to fly over land and cheap enough that your average traveler can afford if they want to trade price for speed. Full autonomous capability so that the plane itself can have thousands of flight hours under its belt before a human test pilot gets on-board.
Maybe this is a dumb question, but why? If you were building an aircraft like this from scratch, why design it to require a present human pilot? Satellite latency too long?
Sure but "earlier in the process"? SpaceX is trying to become passenger-safe as well, they just have the luxury of being able to sell something human-less in the meantime.
As far as I know the cost for going supersonic is extremely high compared to subsonic. There probably isn't much cargo that really needs to be there a few hours earlier. Even the military doesn't have supersonic cargo planes. All (most?) bombers are subsonic too.
The military has used supersonic aircraft on cargo missions in exceptional cases, actually. Their supersonic aircraft tend to be vastly less efficient than even Concorde, though.
The only long range strategic bomber developed after the 50s that wasn't supersonic was the B-2 stealth bomber (not that there have been very many strategic bombers developed after the 50s).
