On Sat, Feb 10, 2018 at 05:45:08PM -0500, Caleuche wrote:
> And setting aside acceleration, at 30km altitude my 800 Dton
> spherical ship modeled here has a maximum velocity equal to about
> Mach 45

Damage to structures on the surface (and people!) could be significant
if such a ship actually moved that fast within a hundred kilometres or
so of an inhabited area.  The speed, size and altitude are comparable
with those of the Chelyabinsk meteor, except that the ship would not
break up but continue to dump kilotons of TNT per second power into
the atmosphere during its whole trajectory.

> (compared to about Mach 9.6 at 10km altitude).

Although the total power would be less, that would cause even more
severe damage on the ground.  If there is any semblance of traffic
control, such speeds would not be permitted anywhere near any
habitation.

- Tim