Powering Planes with Microwaves Is Not the Craziest Idea
spectrum.ieee.org
spectrum.ieee.org
I think a better headline would be that it isn't "crazy" to suggest you could power an airplane with microwaves, but you probably wouldn't want to do it from the ground. Powering it from a solar power satellite has its own issues as well (it would tend to blind satellite receivers on the ground as the plane flew past).
(Of course if satellites have secretly been launching with ginormous notch filters on their receivers for the last 10 years in anticipation of this that might be a thing. :-))
A lower cruise speed would also decrese these numbers. There is a point in the efficiency curve when it increases the total energy used, but still decreases the power. Maybe it's not a big difference, but using the takeoff power seems unnecessarily pessimistic.
Nuclear? It has been researched in the past.
And I imagine that compared to the 50s people would now be much less open to the idea of nuclear reactors flying over their heads. Nuclear reactors that could at any point in time crash due to any number of reasons.
Now, back in the day the NB program was experimenting with nuke aviation, but this is 1951, they don't have electric anything. No, they had DAC as one option, which is compressing the air through an open core, then the heated air gushes out the back. This was, incredibly, even judged unsafe by 1951 standards. IAC - indirect air - was using a heat exchanger to heat the air, then it shoots out the back, but this engine - the HTRE - had a pile of other problems, and was insanely wasteful in comparison.
One of the enduring problems of these (and the SLAM PLUTO nuke ramjet) was using compressed gases as the cooling - it's very hard to make the flows consistent enough to get that precision cooling, because reactor control isn't very fine tuned. There's a definite lag time when changing reactor power. The consequences of a "compressor stall" sort of failure in an air-cooled reactor, where the fluid flow blocks up, were just too horrible. And of course DAC and ramjet nuke engines were basically Chernobyl on wings[1] - they're not going to be landing anywhere.
Nuke-electric though, with a self-contained reactor making tons of juice, and then using distributed propulsion and laminar control to hack the lift/drag - that's where it's at.
[1] Well, not really all that bad, because they're not chucking an entire Home Depot's worth of building materials into an open reactor. Still, any optimistic notions of the airflow being free of fission materials is a frickin' pipedream. It's going to be spewing out some nasty stuff, even if it doesn't damage itself, just by sucking in dust and other passing doodads.
It might also accidentally fry low-earth satellites.
1. OP didn't give a reason for why we should slow down, but
2. if we presume environmental, then equating it to something else widely criticized for being wasteful and environmentally injurious isn't persuasive. At best, it is as bad, but we're well short of the best case, because
3. miles flown don't replace miles driven anywhere near one for one. The alternative to a cross-Atlantic flight isn't a cross-Atlantic drive. It's probably not even a cross-Atlantic cruise. More likely, it's a trip not taken at all, or as often. (Which is a bummer, of course!)
4. Both highways and air travel have conspired to chill investment in rail, which is the cleanest of the three.
5. Air travel is an economically-stimulating activity. I'd be very surprised if the net effect isn't more--probably many, many more--miles driven overall.
Of course there are lots of upsides to air travel and economic activity in general, but I feel like that's obvious!