Isn't cruising power much lower than takeoff power? Having enough batteries for takeoff would make these number much smaller.

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.

Takeoff could even be wired (to be dropped at take off), or power could be delivered through a pantograph-like contraption.

Hah, oh and blind every satellite in low earth orbit sure. :-)

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).

Satellites are 10x higher up than planes -- that probably helps.

Of course, the inverse square law, but given they are not designed to deal with multi-megawatt transmitters shining a light in their eyes, well that would be an issue.

(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. :-))

>nothing developed so far can store energy as cheaply and densely as fossil fuels, or fully meet the needs of commercial air travel as we know it

Nuclear? It has been researched in the past.

US version couldn't keep the airplane in the air, USSR version cooked it's pilots, had dirty exhaust and probably still couldn't keep the airplane in the air.

In the age of strategic bombers it got some research, but the weight of radiation shielding makes it challenging.

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.

Nuclear-electric, with electric ducted props all over the airframe, is probably the best heavy-lift aviation propulsion system. Same as or better power density, insane efficiency, virtually unlimited range, 10-100x less maintenance.

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.

I have a probably stupid question, but would microwaves like this heat water in the air in any sort of substantial manner? Perhaps with negative climate effects?

It's not a stupid question. And yes. It'd be fairly localized, but the absorption losses would be somewhat proportional to the amount of water in the air, so, uh, don't do this on a rainy day. But the climate effects are probably minimal -- the energy is getting turned into heat when the aircraft flies anyway to overcome air friction.

It might also accidentally fry low-earth satellites.

Commercial air travel is the craziest idea. We need to slow down. Nobody should be flying except in emergencies.

That's absolute nonsense. Numbers vary, but domestic airliners have an industry average of about 51 miles per gallon of fuel per passenger. That puts it right around the average car trip (1.5 passengers).

High speed rail could dethrone that, but it would take a lot of infrastructure.

The best time to build that infrastructure was a long time ago. The next best time is now.

The personal automobile is an abomination.

Not saying air travel is bad but to play devil's advocate,

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!

Perhaps this could be solved by having the planes run at ground level, using some sort of guideway, and using either the guideway itself or overhead wires to transmit the power by direct contact?

They looked into this concept a while back and came to the conclusion that unless the population density was great enough along the guideway, the maintenance cost was too high.

The U.S. seems to be able to maintain a quite impressive railroad system for freight purposes, in what is still the largest rail transport network of any country in the world. Passenger transport withered away as long-distance road travel and cheap air flights out-competed it. With sufficient ingenuity and capital expenditure, I wonder if perhaps it could be revived?

That would never work! :-)

Of course not. How would they be able to get over mountains? Or through the English Channel?

* The Swiss and the Channel Tunnel just joined the conversation

No way, that's just for filthy plebs. Us elites need to find the coolest way to move our bodies to places to meet other like-minded elites.

Yeah, trains don’t run over the ocean.

This proposal doesn't either. Unless you are at a strait less than 200km wide. You could hop over the English channel, but if you want to go LA to London you have to take the long way around over the Bering strait.

They could.

https://en.wikipedia.org/wiki/Submerged_floating_tunnel