There are three companies I take seriously for making true spacefaring (ie including Mars because I’m a Mars Firster) truly accessible: SpaceX, Blue Origin, And Masten Space Systems. I would have taken XCOR seriously, but unfortunately they went bankrupt.
The other three:
1. SpaceX. By far the top of my list. Fast execution, well-capitalized when they need to be, sustainable, good business plan to scale up to $100 billion level, and great architecture. Actually hard to improve on this one. But SpaceX got where it is on the shoulders of Elon Musk and by taking a lot of risks. The flip side of that is one of their bets could go far south, or something happens to Elon. Don’t want to rely on one, particularly risk-taking, company.
2. Blue Origin. Somewhat a mystery, but ridiculously well capitalized. Sustained by brute force money injections, not (much) actual business yet. Similar near-term architecture to SpaceX, but slower & not quite as aggressively low cost. Not easily extendable to other planetary bodies without separate development (which apparently they’re doing with Blue Moon). Moon and free space focused, so I wonder if they’ll even get around to Mars before I’m elderly.
3. Masten Space Systems. Very small, poorly capitalized, but actually pioneered a lot of the reusable tech SpaceX uses. More experience with reusable rocket vehicles than anyone. Was looking like a real possibility for highly reusable launch before Boeing sadly won the XS-1 DARPA bid. Now has pulled back and seems focused on small commercial lunar landers. But unlike XCOR, they’re still in the game.
Plan D? Still thinking about it. But I think a rapid return to launch pad thing like BFR and Masten is a good plan, although ambitious. Fast integration of upper stage is key as well. I like Jon’s idea of an oxygen-rich hydrolox architecture.