8 ms·

Axial stack battery design could unlock the era of supersonic electric airliners

86 points by adius 10y ago

lj3 10y ago
Luke Workman. Why am I not surprised to see that guy's name in this article? He took Zero Motorcycles from a battery pack that only went 40 miles to one that goes 120 miles while making the battery pack physically smaller. His work never ceases to amaze.
- dogma1138 10y ago
  >He took Zero Motorcycles from a battery pack that only went 40 miles to one that goes 120 miles while making the battery pack physically smaller. And what did he actually do? lithium ION batteries have been increasing in capacity over the years and quite considerably, 18650's are now nearly 4 times the capacity they were introduced in. I can't find anything he actually did other than hack batteries together to make "custom" packs, while this is some sort of an engineering achievement this is quite far from designing an actual battery.
  - lj3 10y ago
    > while this is some sort of an engineering achievement this is quite far from designing an actual battery. You build a better battery and I'll sing your praises, too. Until then, go be a debby downer somewhere else.
  - ryao 10y ago
    Those "packs" are batteries. The thing that he did not design are electrochemical cells. The term battery pack is a misnomer invented by people who do not understand the difference between a battery and an electrochemical cell.
dogma1138 10y ago
Luke Workman is "some guy" who works for zero motorcycles and hack's EV's together. "Some guy" is the best description I could come with because he isn't a scientists/researcher, he hasn't published a single paper, I can't find even a trace of his record as far as education or engineering achievements go besides soldering a couple of batteries and putting them in a motorcycle. All records I could find of him and his company are pretty much from News Atlas (their sources and references link to their own articles) or it's affiliates.
- flyinglizard 10y ago
  I've met plenty of researchers and paper publishes who're full of crap. The most prolific people I know have no papers behind them. If you do science, you're a scientist; and education in its own is no more of an achievement than raising VC money is. It's just a tool.
  - dogma1138 10y ago
    Your dismissal of actual science is quite absurd. I would still not count anyone who takes of the shelf batteries and soldered them together a scientists, maybe an engineer in the broadest sense of term. I've seen nothing of this guy that makes me think that he is even remotely qualified to design a battery that would go into an aircraft.
    - oldmanjay 10y ago
      I'm finding some humor in your accusation of dismissal considering that you are the only one expressing dismissal in this conversation. It's a very human sort of foible.
- b_emery 10y ago
  The chicken on his shoulder is not lending much credibility either. However, 'some guy' is perfectly fine if the idea is good. One would think that DARPA would be very interested in throwing some money at this idea, if it was a good one. While they are funding electric airplane research, it appears that they are not funding this. Ergo ...
jsprogrammer 10y ago
What if the battery terminal/wing is hit by lightning?
- dogma1138 10y ago
  You don't need to worry about lighting the contraction/expansion from pressure and thermal differences alone is going to be interesting to see, put a battery in a low pressure chamber and see what happens to it. I'm also wondering how they are going to deal with the temperatures and other aspects that can affect the batteries. Solar Impulse flew at 15,000ft, a subsonic or transonic jet would be flying at around 35,000ft, the pressure at those altitudes is about 22-23 kPa and the temperatures are around -55 to -60c, and if he's aiming for supersonic he'll have another issue which is the fact that the temperatures of the aircraft can reach several 100's degrees C from the forces of friction alone.
jpm_sd 10y ago
This is unbelievably stupid. (1) Supersonic airplanes get incredibly hot, just by flying. Largest battery fire the world has ever seen? (2) It would be impossible to manufacture. (3) It would be too heavy to fly.
- digerata 10y ago
  I don't believe he was intending the plane to fly supersonic. Instead he was talking about using the design of the wings because they have a larger volume.
  - triplesec 10y ago
    What's the use of a supersonic plane that doesn't fly supersonic? Edit. It's unclear what your defence of the concept using this tactic achieves. The whole article talks of this as for supersonic flight. There are fewer issues with subsonic flight for this idea, though many (see above and below) remain.
  - dogma1138 10y ago
    The wings of a wide body aircraft would have larger volume, the wing surface area of a 474 is about double that of a concord, the A380 is nearly triple.
- triplesec 10y ago
  Quite. Even Concorde's inner windows were hot to the touch at the end of a flight. The wings would be extremely hot. They even used the fuel as air consorting heat transfer fluid, in an interesting design choice.
nickff 10y ago
This 'proposal' seems to assume that the rest of the aircraft would be almost unaffected by the change, which is very unlikely. Existing engines are designed to compress air, combust fuel, and recover energy from the exhaust to push air (to propel the aircraft) then compress more (to keep the cycle going). Once you are no longer combusting fuel, all of that compression is simply wasted energy. An electric aircraft is much more likely to have single-stage axial fans, with a much larger diameter than jets like the Concorde (because larger and slower fans are more efficient). This difference in propulsion will probably affect various other elements of airframe design. As an aside, Elon Musk has mentioned VTOL as a possible feature of electric aircraft, and this makes a lot of sense. If the fans can be tilted (to provide part of the 'lift' for takeoffs and landings), it means that the airplane could have very small wings, which are usually good for efficiency, but cause problems while landing conventionally.
- scoot 10y ago
  > it means that the airplane could have very small wings, which are usually good for efficiency This is all well and good under normal flight conditions, but the glide ratio in the event of motor failure would not lend itself well to commercial flight. Short wing aircraft are fine for military use where low occupancy and ejector seats provide emergency egress. Passenger aircraft - not so much.
  - nickff 10y ago
    It depends on the reliability of the motors and how many of them there are. With electric aircraft, you could have many more engines spread along the wing (which has some benefits), so the redundancy may be enough to guarantee some power for landing. In addition, there is no 'safe' aircraft, and all of them can fall out of the sky; glide ratios don't help you if the wing breaks at the fuselage. If the motors are as reliable as the wings, then making them more critical seems reasonable.
- etwigg 10y ago
  > Once you are no longer combusting fuel, all of that compression is simply wasted energy. Not true. Instead of burning fuel, you can use electricity (something like an arc welder) to generate heat. And the efficiency with which that heat is turned into mechanical power will be dependent on the compression ratio, regardless of whether the thermal energy is coming from electricity or burning fuel. Thermal energy in chemical fuel and the potential energy in a battery or a raised weight have the same units, but there's actually a difference. You can turn energy in a battery or a raised weight into mechanical energy with 100% efficiency - not achieved in practice, but there's no theoretical limit. When you turn thermal energy into mechanical energy (via Otto cycle in a car or Brayton cycle in a jet), the peak efficiency you can achieve has a theoretical limit based on how much you can compress the working fluid (air) before injecting thermal energy (burning fuel or an electric arc). So if you've got electic energy that you can turn into mechanical energy in a fan with 100% efficiency, why would you take the thermodynamic losses of "burning" that electricity? Because we don't know how to go supersonic speeds with a fan or propeller - the only way we know how, for now, is with a jet running on the brayton cycle. And all the advances we've made in high compression fuel-burning jets would apply to electric jets just as well. If you're okay limiting your top speed to ~Mach 0.7, then you're correct spinning a large propeller using electricity is absolutely a better way to go, and you can make that propeller a lot bigger if you're able to tilt it. Karem Aircraft has done extremely interesting work on figuring out how to tilt rotors, and much of their research would apply to electric motors as well: http://karemaircraft.com/ http://karemaircraft.com/
digerata 10y ago
Wings flex while in flight. Either the cells need to handle that stress or the wing needs to be super rigid. Neither is particularly easy to achieve.
- dogma1138 10y ago
  Wings can't be rigid, the fluttering would shred them to pieces or worse transfer to the main body and shred it pieces (tho at 35-40K ft it doesn't really matter what breaks apart ;)).
bArray 10y ago
I had to squint to look at the images on that site. The designs may or may not be a good idea, but if we can't read them then it doesn't matter. Bit of a poor show from whoever published the article. Looking at the accompanying text, there are some problems with his ideas. Some of that "supporting" material is also about fail-safe design and heat distribution. A copper plate running through the middle of a battery will draw the heat out nicely. These batteries are all good and well until they fail, at which point you have a huge problem. With fuel, you can dump it. What do you do with you battery wing? One of the massive problems is energy density, but that's not the only problem. With the batteries embedded into the wings, you need you to figure out how to effectively charge them too. Planes can't afford to sit for hours on the ground between flights and swapping wings over is not going to fly with safety regulations very well. The intentions are good but I'm not convinced there is something viable here.
- Declanomous 10y ago
  Planes might be able to afford sitting for hours if batteries are that much cheaper than aviation fuel.
  - dogma1138 10y ago
    This has nothing to do with the cost of fuel, an aircraft can't afford to be sitting for hours because the aircraft is very expensive (so you need to pretty much fly all the time) and the space at an airport is at a premium. Airports don't have unlimited apron space and the costs are pretty high the apron costs for LGA for examples are: For the first 15 minutes or fraction thereof $ 50.00 For each additional 15 minutes or fraction thereof $100.00 source: http://www.panynj.gov/airports/pdf/scheduleofcharges-lga.pdf http://www.panynj.gov/airports/pdf/scheduleofcharges-lga.pdf And even with these charges apron space is still a "premium" and it's not designed to be constantly used (this is why airlines usually have a home airport where they can actually reserve space).
    - sliverstorm 10y ago
      Well, he's kind of right, if fuel cost was suddenly zero, the profit margin would explode, and planes wouldn't need to fly as many flights to recoup the capital investment.
Animats 10y ago
Not a better battery, just one with slightly less packaging. That's nowhere near enough for aircraft. "Breakthrough" articles in the battery and "nanotechnology" (usually surface chemistry) fields need to be viewed with extreme skepticism. Those two fields seem to generate a high fraction of overhyped "breakthroughs".
myself248 10y ago
I can't imagine how this would deal with damage. A large amount of Tesla's safety comes from each cell having a micro-fuse connecting it to the module bus, so a failed cell simply disconnects itself. Large single battery plates might be lower-resistance, but they'd be incredibly susceptible to damage.
- ethbro 10y ago
  High performance, low maintenance and supply, fragile. Military hypersonic UAV, anyone?
PaulHoule 10y ago
Too dangerous. If the wing got smacked up a little and got bent, thus the positive and negative surfaces touch, you would have a massive short circuit, then heat-up and very possibly ignition of the electrolyte with a fire that is worse than a jet fuel fire.
anexprogrammer 10y ago
This proposal seems to ignore so much. Like the intense friction, and heating, supersonic flight produces. Concorde's service speed was limited by heat limits place on the aluminium alloy to ensure a decent service life. They were always white as that was part of the spec - dark colours would have taken heat absorption out of limit! Wing roots varied by >100C each flight if I remember right, and fuel was used as a heat sink. Are we going to use the batteries? If the outer surfaces are conductors, what are we doing about icing conditions? Concorde, or likely most SST, engines put out a lot of thrust in a very fighter-like profile (they were a continuation of a fighter engine, and had reheat). Electric fans aren't going to work efficiently in that profile and would probably be large diameter, which isn't very supersonic friendly. How are we now handling taxiing and subsonic? Edit: To expand the last point, Concordes were horribly inefficient subsonic, and burnt something like 2t of fuel to get to the runway. Reheat was used at takeoff and going transonic. They pumped tonnes of fuel after reaching supersonic - for weight and balance and reduced drag. They were basically really big fighters.
- msl 10y ago
  > They were always white as that was part of the spec - dark colours would have taken heat absorption out of limit! Interesting. The SR-71 Blackbird was dark (almost black) in order to radiate heat efficiently [1]. Then again, the Blackbird flew much higher (at around 26 km compared to Concorde's just over 18 km) so maybe convection plays a bigger part in Concorde's thermal management. [1] https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird (Although my primary source is the book "Skunk Works" by Ben R. Ritch and Leo Janos.)
  - chadgeidel 10y ago
    Zing! I, too remember this from "Skunk Works". What a great book!
  - anexprogrammer 10y ago
    Fascinating. Now I want to know why! Maybe at mach 3 more heat's coming from inside than being absorbed. Concordes were specced with Anti-flash White (high reflectivity as used by US and UK nuclear bombers), and the main reason I remember is there was some publicity when France painted one Pepsi blue (not wings) for a sponsorship. It had to have speed restrictions. Wikipedia has a little more (not much), but says the white finish reduced the skin temperature by 6 to 11 degrees Celsius. https://en.wikipedia.org/wiki/Concorde https://en.wikipedia.org/wiki/Concorde
kldavis4 10y ago
The article mentions grid level power storage but I don't see any comments around that. What would the feasibility of creating one of these batteries as some kind of fixed structure be?
- ars 10y ago
  What would be the point? For land power storage you don't care about weight (or volume). Just cost.
WalterBright 10y ago
> But the airline industry is still roughly as slow, and noisy, and expensive, and inefficient and dirty as it has been for the last 40 years This is not true. Dramatic gains in fuel efficiency have been made. Such gains are the primary driver of new airliner designs. The 757, for example, had (if I recall correctly) 35% more efficient engines, and a more efficient wing. The 787 has something like another 20% less fuel burn - again, due to better engines, wing shapes and weight reduction. You also don't see the black smoke trail anymore that was normal for the 707. The engines are much cleaner. There is a limit to how far this can be pushed, but Boeing and the engine makers have done an amazing job in improving the situation.
- hga 10y ago
  You also don't see the black smoke trail anymore that was normal for the 707. I suspect you can in part thank the DoD for that, the black smoke that the F4's engines created did not precisely increase their life expectancy over North Vietnam....
  - manmal 10y ago
    Which makes me think that the military must be very interested in electric jets, given how stealthy they could be.
    - gozur88 10y ago
      I doubt an electric jet engine would be much quieter than a conventional jet. The noise mostly comes from airflow over the airframe and the difference in pressure of the exhaust stream and ambient air. You'll still have both in an electric jet.
      - WalterBright 10y ago
        Think of the noise a vacuum cleaner makes :-(
- nraynaud 10y ago

86 points by adius 10y ago

lj3 10y ago

Luke Workman. Why am I not surprised to see that guy's name in this article? He took Zero Motorcycles from a battery pack that only went 40 miles to one that goes 120 miles while making the battery pack physically smaller. His work never ceases to amaze.

dogma1138 10y ago
>He took Zero Motorcycles from a battery pack that only went 40 miles to one that goes 120 miles while making the battery pack physically smaller. And what did he actually do? lithium ION batteries have been increasing in capacity over the years and quite considerably, 18650's are now nearly 4 times the capacity they were introduced in. I can't find anything he actually did other than hack batteries together to make "custom" packs, while this is some sort of an engineering achievement this is quite far from designing an actual battery.
- lj3 10y ago
  > while this is some sort of an engineering achievement this is quite far from designing an actual battery. You build a better battery and I'll sing your praises, too. Until then, go be a debby downer somewhere else.
- ryao 10y ago
  Those "packs" are batteries. The thing that he did not design are electrochemical cells. The term battery pack is a misnomer invented by people who do not understand the difference between a battery and an electrochemical cell.

dogma1138 10y ago

Luke Workman is "some guy" who works for zero motorcycles and hack's EV's together. "Some guy" is the best description I could come with because he isn't a scientists/researcher, he hasn't published a single paper, I can't find even a trace of his record as far as education or engineering achievements go besides soldering a couple of batteries and putting them in a motorcycle. All records I could find of him and his company are pretty much from News Atlas (their sources and references link to their own articles) or it's affiliates.

flyinglizard 10y ago
I've met plenty of researchers and paper publishes who're full of crap. The most prolific people I know have no papers behind them. If you do science, you're a scientist; and education in its own is no more of an achievement than raising VC money is. It's just a tool.
- dogma1138 10y ago
  Your dismissal of actual science is quite absurd. I would still not count anyone who takes of the shelf batteries and soldered them together a scientists, maybe an engineer in the broadest sense of term. I've seen nothing of this guy that makes me think that he is even remotely qualified to design a battery that would go into an aircraft.
  - oldmanjay 10y ago
    I'm finding some humor in your accusation of dismissal considering that you are the only one expressing dismissal in this conversation. It's a very human sort of foible.
b_emery 10y ago
The chicken on his shoulder is not lending much credibility either. However, 'some guy' is perfectly fine if the idea is good. One would think that DARPA would be very interested in throwing some money at this idea, if it was a good one. While they are funding electric airplane research, it appears that they are not funding this. Ergo ...

jsprogrammer 10y ago

What if the battery terminal/wing is hit by lightning?

dogma1138 10y ago
You don't need to worry about lighting the contraction/expansion from pressure and thermal differences alone is going to be interesting to see, put a battery in a low pressure chamber and see what happens to it. I'm also wondering how they are going to deal with the temperatures and other aspects that can affect the batteries. Solar Impulse flew at 15,000ft, a subsonic or transonic jet would be flying at around 35,000ft, the pressure at those altitudes is about 22-23 kPa and the temperatures are around -55 to -60c, and if he's aiming for supersonic he'll have another issue which is the fact that the temperatures of the aircraft can reach several 100's degrees C from the forces of friction alone.

jpm_sd 10y ago

This is unbelievably stupid. (1) Supersonic airplanes get incredibly hot, just by flying. Largest battery fire the world has ever seen? (2) It would be impossible to manufacture. (3) It would be too heavy to fly.

digerata 10y ago
I don't believe he was intending the plane to fly supersonic. Instead he was talking about using the design of the wings because they have a larger volume.
- triplesec 10y ago
  What's the use of a supersonic plane that doesn't fly supersonic? Edit. It's unclear what your defence of the concept using this tactic achieves. The whole article talks of this as for supersonic flight. There are fewer issues with subsonic flight for this idea, though many (see above and below) remain.
- dogma1138 10y ago
  The wings of a wide body aircraft would have larger volume, the wing surface area of a 474 is about double that of a concord, the A380 is nearly triple.
triplesec 10y ago
Quite. Even Concorde's inner windows were hot to the touch at the end of a flight. The wings would be extremely hot. They even used the fuel as air consorting heat transfer fluid, in an interesting design choice.

nickff 10y ago

This 'proposal' seems to assume that the rest of the aircraft would be almost unaffected by the change, which is very unlikely. Existing engines are designed to compress air, combust fuel, and recover energy from the exhaust to push air (to propel the aircraft) then compress more (to keep the cycle going). Once you are no longer combusting fuel, all of that compression is simply wasted energy. An electric aircraft is much more likely to have single-stage axial fans, with a much larger diameter than jets like the Concorde (because larger and slower fans are more efficient). This difference in propulsion will probably affect various other elements of airframe design. As an aside, Elon Musk has mentioned VTOL as a possible feature of electric aircraft, and this makes a lot of sense. If the fans can be tilted (to provide part of the 'lift' for takeoffs and landings), it means that the airplane could have very small wings, which are usually good for efficiency, but cause problems while landing conventionally.

scoot 10y ago
> it means that the airplane could have very small wings, which are usually good for efficiency This is all well and good under normal flight conditions, but the glide ratio in the event of motor failure would not lend itself well to commercial flight. Short wing aircraft are fine for military use where low occupancy and ejector seats provide emergency egress. Passenger aircraft - not so much.
- nickff 10y ago
  It depends on the reliability of the motors and how many of them there are. With electric aircraft, you could have many more engines spread along the wing (which has some benefits), so the redundancy may be enough to guarantee some power for landing. In addition, there is no 'safe' aircraft, and all of them can fall out of the sky; glide ratios don't help you if the wing breaks at the fuselage. If the motors are as reliable as the wings, then making them more critical seems reasonable.
etwigg 10y ago
> Once you are no longer combusting fuel, all of that compression is simply wasted energy. Not true. Instead of burning fuel, you can use electricity (something like an arc welder) to generate heat. And the efficiency with which that heat is turned into mechanical power will be dependent on the compression ratio, regardless of whether the thermal energy is coming from electricity or burning fuel. Thermal energy in chemical fuel and the potential energy in a battery or a raised weight have the same units, but there's actually a difference. You can turn energy in a battery or a raised weight into mechanical energy with 100% efficiency - not achieved in practice, but there's no theoretical limit. When you turn thermal energy into mechanical energy (via Otto cycle in a car or Brayton cycle in a jet), the peak efficiency you can achieve has a theoretical limit based on how much you can compress the working fluid (air) before injecting thermal energy (burning fuel or an electric arc). So if you've got electic energy that you can turn into mechanical energy in a fan with 100% efficiency, why would you take the thermodynamic losses of "burning" that electricity? Because we don't know how to go supersonic speeds with a fan or propeller - the only way we know how, for now, is with a jet running on the brayton cycle. And all the advances we've made in high compression fuel-burning jets would apply to electric jets just as well. If you're okay limiting your top speed to ~Mach 0.7, then you're correct spinning a large propeller using electricity is absolutely a better way to go, and you can make that propeller a lot bigger if you're able to tilt it. Karem Aircraft has done extremely interesting work on figuring out how to tilt rotors, and much of their research would apply to electric motors as well: http://karemaircraft.com/ http://karemaircraft.com/

digerata 10y ago

Wings flex while in flight. Either the cells need to handle that stress or the wing needs to be super rigid. Neither is particularly easy to achieve.

dogma1138 10y ago
Wings can't be rigid, the fluttering would shred them to pieces or worse transfer to the main body and shred it pieces (tho at 35-40K ft it doesn't really matter what breaks apart ;)).

bArray 10y ago

I had to squint to look at the images on that site. The designs may or may not be a good idea, but if we can't read them then it doesn't matter. Bit of a poor show from whoever published the article. Looking at the accompanying text, there are some problems with his ideas. Some of that "supporting" material is also about fail-safe design and heat distribution. A copper plate running through the middle of a battery will draw the heat out nicely. These batteries are all good and well until they fail, at which point you have a huge problem. With fuel, you can dump it. What do you do with you battery wing? One of the massive problems is energy density, but that's not the only problem. With the batteries embedded into the wings, you need you to figure out how to effectively charge them too. Planes can't afford to sit for hours on the ground between flights and swapping wings over is not going to fly with safety regulations very well. The intentions are good but I'm not convinced there is something viable here.

Declanomous 10y ago
Planes might be able to afford sitting for hours if batteries are that much cheaper than aviation fuel.
- dogma1138 10y ago
  This has nothing to do with the cost of fuel, an aircraft can't afford to be sitting for hours because the aircraft is very expensive (so you need to pretty much fly all the time) and the space at an airport is at a premium. Airports don't have unlimited apron space and the costs are pretty high the apron costs for LGA for examples are: For the first 15 minutes or fraction thereof $ 50.00 For each additional 15 minutes or fraction thereof $100.00 source: http://www.panynj.gov/airports/pdf/scheduleofcharges-lga.pdf http://www.panynj.gov/airports/pdf/scheduleofcharges-lga.pdf And even with these charges apron space is still a "premium" and it's not designed to be constantly used (this is why airlines usually have a home airport where they can actually reserve space).
  - sliverstorm 10y ago
    Well, he's kind of right, if fuel cost was suddenly zero, the profit margin would explode, and planes wouldn't need to fly as many flights to recoup the capital investment.

Animats 10y ago

Not a better battery, just one with slightly less packaging. That's nowhere near enough for aircraft. "Breakthrough" articles in the battery and "nanotechnology" (usually surface chemistry) fields need to be viewed with extreme skepticism. Those two fields seem to generate a high fraction of overhyped "breakthroughs".

myself248 10y ago

I can't imagine how this would deal with damage. A large amount of Tesla's safety comes from each cell having a micro-fuse connecting it to the module bus, so a failed cell simply disconnects itself. Large single battery plates might be lower-resistance, but they'd be incredibly susceptible to damage.

ethbro 10y ago
High performance, low maintenance and supply, fragile. Military hypersonic UAV, anyone?

PaulHoule 10y ago

Too dangerous. If the wing got smacked up a little and got bent, thus the positive and negative surfaces touch, you would have a massive short circuit, then heat-up and very possibly ignition of the electrolyte with a fire that is worse than a jet fuel fire.

anexprogrammer 10y ago

This proposal seems to ignore so much. Like the intense friction, and heating, supersonic flight produces. Concorde's service speed was limited by heat limits place on the aluminium alloy to ensure a decent service life. They were always white as that was part of the spec - dark colours would have taken heat absorption out of limit! Wing roots varied by >100C each flight if I remember right, and fuel was used as a heat sink. Are we going to use the batteries? If the outer surfaces are conductors, what are we doing about icing conditions? Concorde, or likely most SST, engines put out a lot of thrust in a very fighter-like profile (they were a continuation of a fighter engine, and had reheat). Electric fans aren't going to work efficiently in that profile and would probably be large diameter, which isn't very supersonic friendly. How are we now handling taxiing and subsonic? Edit: To expand the last point, Concordes were horribly inefficient subsonic, and burnt something like 2t of fuel to get to the runway. Reheat was used at takeoff and going transonic. They pumped tonnes of fuel after reaching supersonic - for weight and balance and reduced drag. They were basically really big fighters.

msl 10y ago
> They were always white as that was part of the spec - dark colours would have taken heat absorption out of limit! Interesting. The SR-71 Blackbird was dark (almost black) in order to radiate heat efficiently [1]. Then again, the Blackbird flew much higher (at around 26 km compared to Concorde's just over 18 km) so maybe convection plays a bigger part in Concorde's thermal management. [1] https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird (Although my primary source is the book "Skunk Works" by Ben R. Ritch and Leo Janos.)
- chadgeidel 10y ago
  Zing! I, too remember this from "Skunk Works". What a great book!
- anexprogrammer 10y ago
  Fascinating. Now I want to know why! Maybe at mach 3 more heat's coming from inside than being absorbed. Concordes were specced with Anti-flash White (high reflectivity as used by US and UK nuclear bombers), and the main reason I remember is there was some publicity when France painted one Pepsi blue (not wings) for a sponsorship. It had to have speed restrictions. Wikipedia has a little more (not much), but says the white finish reduced the skin temperature by 6 to 11 degrees Celsius. https://en.wikipedia.org/wiki/Concorde https://en.wikipedia.org/wiki/Concorde

kldavis4 10y ago

The article mentions grid level power storage but I don't see any comments around that. What would the feasibility of creating one of these batteries as some kind of fixed structure be?

ars 10y ago
What would be the point? For land power storage you don't care about weight (or volume). Just cost.

WalterBright 10y ago

> But the airline industry is still roughly as slow, and noisy, and expensive, and inefficient and dirty as it has been for the last 40 years This is not true. Dramatic gains in fuel efficiency have been made. Such gains are the primary driver of new airliner designs. The 757, for example, had (if I recall correctly) 35% more efficient engines, and a more efficient wing. The 787 has something like another 20% less fuel burn - again, due to better engines, wing shapes and weight reduction. You also don't see the black smoke trail anymore that was normal for the 707. The engines are much cleaner. There is a limit to how far this can be pushed, but Boeing and the engine makers have done an amazing job in improving the situation.

hga 10y ago
You also don't see the black smoke trail anymore that was normal for the 707. I suspect you can in part thank the DoD for that, the black smoke that the F4's engines created did not precisely increase their life expectancy over North Vietnam....
- manmal 10y ago
  Which makes me think that the military must be very interested in electric jets, given how stealthy they could be.
  - gozur88 10y ago
    I doubt an electric jet engine would be much quieter than a conventional jet. The noise mostly comes from airflow over the airframe and the difference in pressure of the exhaust stream and ambient air. You'll still have both in an electric jet.
    - WalterBright 10y ago
      Think of the noise a vacuum cleaner makes :-(
nraynaud 10y ago