5 ms·

Powering Planes with Microwaves Is Not the Craziest Idea

donatj 2y ago
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?
- dgacmu 2y ago
  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.
lambdaone 2y ago
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?
- deleted 2y ago
  [deleted]
- ChuckMcM 2y ago
  That would never work! :-)
  - dgacmu 2y ago
    Of course not. How would they be able to get over mountains? Or through the English Channel?
    - xandrius 2y ago
      * The Swiss and the Channel Tunnel just joined the conversation
- orson2077 2y ago
  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.
  - lambdaone 2y ago
    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?
- OldManAndTheCpp 2y ago
  Yeah, trains don’t run over the ocean.
  - wongarsu 2y ago
    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.
  - LargoLasskhyfv 2y ago
    They could. https://en.wikipedia.org/wiki/Submerged_floating_tunnel https://en.wikipedia.org/wiki/Submerged_floating_tunnel
- xandrius 2y ago
  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.
ChuckMcM 2y ago
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).
- thehappypm 2y ago
  Satellites are 10x higher up than planes -- that probably helps.
  - ChuckMcM 2y ago
    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. :-))
deleted 2y ago
[deleted]
afh1 2y ago
>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.
- M95D 2y ago
  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.
- wongarsu 2y ago
  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.
- MilStdJunkie 2y ago
  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.
thanatos519 2y ago
Commercial air travel is the craziest idea. We need to slow down. Nobody should be flying except in emergencies.
- ryandvm 2y ago
  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).
  - pennomi 2y ago
    High speed rail could dethrone that, but it would take a lot of infrastructure.
    - thanatos519 2y ago
      The best time to build that infrastructure was a long time ago. The next best time is now.
  - thanatos519 2y ago
    The personal automobile is an abomination.
  - Clamchop 2y ago
    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!
aidenn0 2y ago
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.
- throwaway89201 2y ago
  Takeoff could even be wired (to be dropped at take off), or power could be delivered through a pantograph-like contraption.

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?

dgacmu 2y ago
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.

lambdaone 2y ago

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?

deleted 2y ago
[deleted]
ChuckMcM 2y ago
That would never work! :-)
- dgacmu 2y ago
  Of course not. How would they be able to get over mountains? Or through the English Channel?
  - xandrius 2y ago
    * The Swiss and the Channel Tunnel just joined the conversation
orson2077 2y ago
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.
- lambdaone 2y ago
  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?
OldManAndTheCpp 2y ago
Yeah, trains don’t run over the ocean.
- wongarsu 2y ago
  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.
- LargoLasskhyfv 2y ago
  They could. https://en.wikipedia.org/wiki/Submerged_floating_tunnel https://en.wikipedia.org/wiki/Submerged_floating_tunnel
xandrius 2y ago
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.

ChuckMcM 2y ago

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).

thehappypm 2y ago
Satellites are 10x higher up than planes -- that probably helps.
- ChuckMcM 2y ago
  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. :-))

deleted 2y ago

[deleted]

afh1 2y ago

>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.

M95D 2y ago
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.
wongarsu 2y ago
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.
MilStdJunkie 2y ago
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.

thanatos519 2y ago

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

ryandvm 2y ago
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).
- pennomi 2y ago
  High speed rail could dethrone that, but it would take a lot of infrastructure.
  - thanatos519 2y ago
    The best time to build that infrastructure was a long time ago. The next best time is now.
- thanatos519 2y ago
  The personal automobile is an abomination.
- Clamchop 2y ago
  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!

aidenn0 2y ago

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.

throwaway89201 2y ago
Takeoff could even be wired (to be dropped at take off), or power could be delivered through a pantograph-like contraption.