Reply To: General thought on old coal mines.

[vansig]

zapkitty wrote:
An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85…

What I still don’t get is, why is Mach 0.72 an upper bound?

We’re not limited by mass; 80 anodes tesselating a sphere yields 20 tonnes, not 160 tonnes.

We’re not limited to propeller or turbo-prop configuration.

Fusion powered jet does not require a turbine; we don’t have to slow the airstream down or compress it, to heat it, as a ramjet does, since we don’t have to inject chemical fuels.

Scramjet configuration seems to be the simplest engine architecture. and it’s highly efficient, *if* we have a way to heat air with electricity. which we do: i propose to build a high-wattage infrared laser, emitting at a wavelength that air strongly absorbs, yet engine materials do not absorb.

What remains, that could keep this below high Mach numbers and altitudes of 35km or more?