I want you to watch this fucker. Not because he's entirely relevant, but because he's kinda relevant (and awesome).

That's John Stapp, going ragged edge of mach the hard way. Asshole went 570mph in an open-topped jet just to see if it was safe.

This one's not much better:

Same track, 50 years later, NASA hitting 2800 m/s. Aerodynamics still not really factoring that much. There's no substitute for cubic inches, as they say. Still, we're less than halfway there.

Riddle me this - didja read?

The Gen-1 system proposes to accelerate unmanned craft at 30 g through a 130-kilometer (81 mi) long tunnel, with a plasma window preventing vacuum loss when the exit's mechanical shutter is briefly open, evacuated of air with an MHD pump. (The plasma window is larger than prior constructions, 2.5 MW estimated power consumption itself for 3 metres (9.8 ft) diameter).[12] In the reference design, the exit is on the surface of a mountain peak of 6,000 metres (20,000 ft) altitude, where 8.78 kilometres per second (5.46 mi/s) launch velocity at a 10 degree angle takes cargo capsules to low earth orbit when combined with a small rocket burn providing 0.63 kilometres per second (0.39 mi/s) for orbit circularization. With a bonus from Earth's rotation if firing east, the extra speed, well beyond nominal orbital velocity, compensates for losses during ascent including 0.8 kilometres per second (0.50 mi/s) from atmospheric drag.

131 km. The SSC was 87km; you wouldn't even need to go 'round twice. The optimization is for centrifugal force vs. circumference; that's the sort of thing one would want to test at small scale, I reckon.

So build it high and have a gradually increasing pressure as the vessel ascends in the tube? That's gonna make the Burj Khalifa look like child's play.

I think that messing with the pressure (positive or negative) is a great reason to do some testing. Either way, you're leaving the heavy shit on the ground. Besides, I know some of the guys who worked on the Burj. It's just a tall damn building.

If you're in the mood to investigate magnetic tube launch, the best place to start is to build a magnetic tube launcher. Reusable rockets are nice, but Elon has to have known from the beginning that they're an interim technology at best.

This is a guy who wants to colonize Mars. He ain't doin' that with hydrox.