Reply To: General thought on old coal mines.

[zapkitty]

vansig 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?

That was just me using “default” 5MWe FF boxes for aircraft concepts equivalent to current commercial turboprops. A “go anywhere at any time” electric aircraft.

Turboprops such as the Tu-95 have gone as high as Mach 0.92 in tests.

vansig wrote:
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?

And that brings us back to the question of whether using the excess alpha output for direct heating of air would be more efficient. Your design is for 400 MWe, right? Are you omitting the 640 MWt “waste” heat from your calculations? What if there was no “onion” and you tried to use the x-rays as a heat source as well?