Reply To: General thought on old coal mines.

[zapkitty]

vansig wrote: here is an article detailing scaling parameters for EHD thrusters.

http://www.wbabin.net/physics/borg1.pdf

… but energy density is still the problem. Even with the most optimistic shielding estimates you still have to have over 4.2 metric tons of water with each power module in addition to the FF cores, caps, onion etc… and both safety and cooling mean that you will not be able to squeeze all the cores into one module.

The notional N3-X in the example I cited will require over 80 MWe and it’s just a small subsonic transport (… but that’s still way better than the 400 MWe that I had originally estimated for jet-style propulsion 🙂 )

No one seems optimistic at this time about getting much over 5 MWe per core and limiting the shielding will mean that the craft will not be able to get within 800 meters of anyone or anything.

So will FF, with the parameters as currently stipulated, have a place in aviation? I believe so… a truly revolutionary place as I’ve detailed elsewhere in this thread. And the recent work on distributed electric propulsion and MHD seems to emphasize the advantages of FF and even allow the possibility of FF supersonic transports… but…

… but…

… the two turbogenerators of that N3-X and the fuel to power them will fit in a couple of standard 2x2x3 meter FF “boxes.”

I was shocked 🙂

FF has advantages. All-electric, not air-breathing, never runs out of fuel (as far as standard aircraft operations are concerned), clean and green as all get out… but power density is not one of those advantages.

In atmosphere, that is. Get one into orbit and you’d better get out of the way because it ain’t going to wait around for you 🙂

I will continue with my attempts to see where this all leads and lay out my figures here… but the curves indicate an area between supersonic and orbital where shielded FF by itself is not competitive with chemical.

And those designs I mentioned upthread that emphasized a combination of fusion and chemical for spaceplanes now make a lot more sense to me…