The majority? That would be at least 18,000 MPH/sqrt(2), wouldn’t it? Around 12,700 MPH. Yeah, that sounds total feasible anywhere the atmosphere is thick enough to breath.

To give you an idea of the g-loads involved, a typical modern artillery shell (hollow filled with explosive) is in the order of 40,000 g’s. for a muzzle velocity of circa 2700 fps (M777 155mm Howitzer firing Charge 8 Super). Modern tank guns firing solid shot have velocities in the order of 5000 fps and up (M900 APFSDS-T from M68 105mm gun as mounted on US M60 tank, MV = 1505 m/s = 4940 fps and US M829 APFSDS-T “Silver Bullet” from M256 120mm as mounted on M1A1 tank, MV = 1679 m/s = 5510 fps). I have no idea what they translate into in terms of g force, but I don’t think “epic” covers it !

As for “liquifying your giblets”

The manual says “The overpressure from the 120mm cannon can kill a dismounted infantryman within a 90° arc extending from the muzzle of the gun tube out to 200 meters.”

Which partially explains why I was a tanker at the other end of the gun

One potentially “rational” approach I can see would be to use a large vertical coil gun that is fed by a bank of massive flywheels that convert all their energy to electricity in a fraction of a second.

A variation on this theme that might be easier to engineer would be a vertical Heinlein-esque “booster gun” in which the bank of massive flywheels each have a smaller coil gun that accelerates a piston into a cylinder filled with an inexpensive noble gas like argon. These would be “ripple-fired” to provide initial boost-from-rest momentum to the rocket projectile/payload and to keep up or even increase the driving pressure as said projectile rises in the main gun tube toward its release into the atmosphere – probably through a burst disc over the muzzle.

Of course SpinLaunch may have something entirely different than either of these spitballs of mine in mind.

However they figure to do things, it’ll be a heckuva thing to watch – from a suitable distance and with adequate protection. Observers would be well-advised to watch only through some armored-glass port in a massive bunker. Mach 10 sonic booms at ground level might just liquify your giblets even fairly far away if encountered in the open. I wonder a bit about the fate of all that nice curtain glass in the Virgin Galactic terminal.

Ecuador is waiting! Mountains and a perfect location for zero degree inclination trajectories. There’s more to grow there than guerrillas and coffee and narcotics!