Axial stack battery design could unlock the era of supersonic electric airliners | Hacker News Reader

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

newatlas.com

86 pointsadius104 comments

> 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.

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....

Which makes me think that the military must be very interested in electric jets, given how stealthy they could be.

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.

Think of the noise a vacuum cleaner makes :-(

you have to remember that a lot of gain come from economy of scale, making bigger planes, the gains are realized only if passenger traffic increase (hence total pollution).

See https://en.wikipedia.org/wiki/Jevons_paradox

You can reduce flight count and have the same amount of passengers to have a net gain in efficiency and a reduction in pollution.

The 757 was about the same size as the 727, but 35% less fuel burn. The gains I cited were for the same size aircraft. (I worked on the 757 engineering.) The gains are real, and the airliners fell all over themselves to replace the old, inefficient jets with the new ones, because the operational cost savings were immense.

Ever notice the little vertical "winglets" on the wing tips? They increase the wing efficiency. They worked so well that Boeing produced kits so older aircraft could get them, too. They're just one example. The plastic skin used on the 787 is for weight saving, another example of reduced fuel burn.

I should mention that 40% of an airliner operating cost is fuel burn, if I recall correctly. That makes fuel efficiency a BFD to airlines and therefore Boeing and the engine makers. They'll spend a metric ton of money for even small improvements.

If you calculate the share of airliner operating costs - possibly. But it is smaller fraction of total ticket price. According to this video it's only 3% https://www.youtube.com/watch?v=6Oe8T3AvydU.

Noise is also reduced massively:

http://www.bdl.aero/media/filer_public/46/16/4616cefd-aa12-4...

Comparing 1960s 737 vs 1990s 737. And 787

or here: http://www.airbus.com/fileadmin/media_gallery/photogallery/b...

a380 with hushkit compared to 747-400 (first flight 1989)

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.

> 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 (Although my primary source is the book "Skunk Works" by Ben R. Ritch and Leo Janos.)

Zing! I, too remember this from "Skunk Works". What a great book!

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

The sun adds 1000 watts per square meter, and black body radiation is the fourth power of temperature difference. If you're heating the skin say 5000 watts per square meter due to friction or compression, then the 1000 watts from the sun isn't bad. But if it's only say 500 watts, well, then the sun dominates. They operated at different speeds and altitudes so it's not entirely surprising to me that they had different strategies.

Note that they were using titanium, and while I'm not sure what the fuel cells were made of, until they heated up it leaked quite a bit. One of the first orders of business after takeoff was getting a refuel, which included changing the type of fuel, see e.g. http://iliketowastemytime.com/facts-you-didnt-know-about-sr7...

re: "... dark colours would have taken heat absorption out of limit!"

The SR-71 Blackbird was black because that color dissipates heat. [1] The plane was also made from titanium, not aluminum so there may be other factors but black dissipates heat as well as it absorbs it.

[1] http://www.lockheedmartin.com/us/100years/stories/blackbird....

I thought the black was paint impregnated with tiny iron oxide balls to absorb radar energy?

edit: they say that farther down the page

"...and a radar-absorbing element was added to the paint."

It couldn't an electric fly way higher and avoid that friction because it has no need for oxygen?

That's the other benefit of electric planes.

Um. If we reach a height of no friction, what are the electric jets compressing?

If there's air there's friction, if there's no air there's no thrust. Rockets take their own oxidant.

The height limit isn't because engines need oxygen. It's because in order to fly in less dense air, you need to have higher air speed to generate the same amount of lift, and above typical jet cruising altitudes you hit the speed of sound and run into issues.

Supersonic aircraft fly at higher altitudes in general - the Concorde cruised at 56000 feet.

Even if it doesn't need oxygen it will still need reaction mass. The engine won't produce thrust if there's nothing to shoot out the back.

> They were always white as that was part of the spec - dark colours would have taken heat absorption out of limit!

Since radiant (photons) heat emission follows radiant heat absorption: Black absorbs better, but also emits it better.

Maybe they didn't care about emitting heat, they just didn't want the sun adding heat?

> Like the intense friction, and heating

The heating does not come from friction. If a gas is compressed, it heats up. Moving through air compresses it in front. There's a point on the leading edge where the air is actually still. That's the point of maximum compression, and maximum heat (and minimum friction!). (Pitot tubes work on this principle, they are simply air pressure gauges calibrated to read as speed rather than PSI.)

This misattribution is one of my pet peeves. <grump>

Thanks for your on point technical replies on aircraft engineering here. Really fascinating stuff.

> They were always white as that was part of the spec - dark colours would have taken heat absorption out of limit!

Wouldn't the color only matter when it comes to heating due to absorption of electromagnetic radiation?

For heat transfer by direct contact with the heat source (in this case gases that were heated when compressed by the plane's motion), wouldn't color be irrelevant?

Does the math work out if you ditch the "supersonic" part? Supersonic is pretty niche anyway, since you can't do it anywhere near populated areas; but substantially reducing per-passenger costs for subsonic planes could change a lot.

I think the math doesn't work out with subsonic since those huge delta wings are only efficient for supersonic flight. For subsonic a conventional swept wing (like on a 747) is much more efficient.

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.

> 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.

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.

> 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/

This idea of an electrical-arc jet engine is new to me. Can you point to any published material on such a design or prototype? Very intriguing.

Nobody who has taken a course in energy conversion (an second or third level thermodynamics course) would even bother to propose this. It is not coincidental that all mechanical engineers take this course, and mechanical engineers are also the people who design engines.

If you take a course in energy conversion, and also an economics course, then you would consider this.

https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

Some joules are more expensive than others :)

The nuclear aircraft did not fail because nuclear power was too expensive, they failed because reactors were too heavy. If you read more about the American nuclear aircraft programs, you will find that they were most interested in using the heat from Nuclear reactions to warm up air; they did not propose to generate electricity with which to heat or push air (because it is too complex and inefficient).

Right. A nuclear reactor generates massive amounts of heat from fission, then uses that heat to boil water (sometimes heavy water for better radiation shielding) to make steam to cause turbines to spin, which generates the electricity. (in fact, fossil fuel burning plants also use this steam-electric model)

If the end goal is to generate heat, then there's no good reason to add those additional steps.

Using an RTG producing electricity as a heat source in a Brayton-cycle engine was on my Jet-Pro final exam in college.

>"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."

Turning chemical energy (low entropy energy) into electrical energy (low-medium entropy) into thermal energy (high entropy) to make mechanical energy (of intermediate) would be incredibly inefficient. Combustible fuels are much better than batteries at making things hot; I don't have the time to run the numbers right now, but what you are saying is incredibly wasteful. Please take a thermodynamics course.

Fans are commonly used on supersonic aircraft. Most modern fighter aircraft use medium or low bypass turbofans, which are using fans to go supersonic. Turbofans are less efficient than turbojets over Mach ~1.6-1.8 (or in reheat), but a ducted fan could probably do better.

You are correct that it's wasteful, if one joule of electric energy and one joule of chemical energy cost the same.

But if you are getting electric energy for free from solar panels, and you're getting chemical energy by pumping taxed dinosaur carbon into the air, then you might find that the electric energy could be more efficient.

You're absolutely correct that it's wildly inefficient by any metric now. But if clean electric energy became wildly abundant, that would change.

In computing, there are all kinds of wildly wasteful things (web browsers) that are the best way to do things because computation is extremely cheap. It's very interesting to think about what kinds of devices would make economic sense if electric energy had the same price collapse that computation has done.

The fact that we "burn electricity" in electric water heaters, stoves, and toasters rather than only using high-entropy energy sources like gas water heaters and gas stoves is an example where present-day electric energy supply chains have beaten out the theoretical advantages of only using high-entropy energy sources when it is possible to do so.

This is not about financial cost, it is about weight and complexity. It would be less costly and more efficient to separate water into hydrogen and oxygen (using solar power if you like), then use them to power a rocket engine.

Aircraft weight turns directly into fuel cost via induced-drag. If electric energy is wildly inexpensive, you can afford very heavy airframes.

See https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

There are two major problems with very heavy airframes:

1) Aircraft cost is proportional to empty weight.

2) Range is proportional to total stored energy / drag and drag is proportional to weight. If you have low specific energy, you cannot go far.

One more to add. Current commercial aircraft can jettison fuel to reduce the landing weight and minimize risk if the structure is compromised. Hard to see how this design would.

Jets also constantly lose weight while burning fuel. This results in airliners flying higher and more efficiently as the flight progresses. With batteries, you're kinda stuck with the weight.

And it's true that airliners take off with more weight than they are speced to land with. They have to dump fuel if landing before burning it off.

No reason I can think of why you can't drop empty batteries in an emergency situation. In fact, you probably want swapable batteries to begin with, don't want to waste time on the tarmac charging up.

One reason would be if they're built into the wing surfaces, as this article proposes. You probably don't want to jettison your wings.

> But if you are getting electric energy for free from solar panels

If you are getting electrical energy for free I have some WAY WAY better uses for it than an airplane.

Let's save hydrocarbon fuel for mobile installation (planes and cars), and use the solar power for fixed installations (houses, industry).

Maybe once you maxed out houses, we can come back to the mobile stuff.

Even if it's free, converting energy to thrust at say 1:0.95 mechanically you can go faster vs. 1:0.35 with a heat engine.

Very interesting! I had no idea we could convert our existing jet engine technologies to electric.

Could the Same conversion apply to scram jets?

You can do this, but it is roughly equivalent to using a battery pack to heat water for a steam engine; it is a very bad idea.

Which was seriously considered during the cold war: https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

As bad of an idea as using javascript to do addition rather than assembly. You're assuming electric energy is the same order of magnitude cost as electric energy. It's possible that could change some day.

Even if cost is not a factor, it is still a bad idea to heat water with electricity in weight and time-critical applications. For instance, if you want to heat water using solar power, you should focus sunlight on the water in a black container rather than using photovoltaic (PV) solar panels.

> Instead of burning fuel, you can use electricity (something like an arc welder) to generate heat.

Why go through all the trouble of using electricity as the heat source in a Brayton cycle engine instead of the obvious solution, using electric motors? Your statement that "we don't know how to go supersonic speeds with a fan or propeller" is clearly wrong, since supersonic aircraft have been flying with turbofans and no afterburners for almost five decades now.

When a jet engine burns fuel, some energy goes into turning the fan, and some energy goes into creating thrust.

At low-mach, the fuel burn is primarily producing torque which turns the fan. This fan could be turned by electricity.

At high-mach, the fuel burn is primarily producing pure thrust, and the fan portion hurts the engine's performance.

Supersonic turbofans are a compromise that have to produce thrust from takeoff through to high speed. I may be incorrect, but I don't believe we have ever built a ducted fan which can use pure torque to generate supersonic thrust, although I guess I don't see why it wouldn't be theoretically possible. We can put megawatts of energy into a fast-moving flow using thermal energy and a brayton cycle. In order to put megawatts of energy into fast-moving flow using rotors would require a totally new design - nothing like the supersonic turbofans currently in production.

You have to distinguish the conventional (high efficiency) cycle of a jet engine at low Mach, from the reheat (low efficiency) operation usually used for high Mach.

No engine (of which I am aware) has air flowing past the fan blades at supersonic speeds, because the trans-sonic transitions tear engines apart. There is one prototype aircraft (a naval derivative of the F-84) which did have a supersonic propeller, but it was very inefficient and loud. All jet engines compress sub-Mach 1 flows, then expand them at the very back of the engine to produce supersonic exhaust.

> You have to distinguish the conventional (high efficiency) cycle of a jet engine at low Mach, from the reheat (low efficiency) operation usually used for high Mach.

Exactly. At high mach, almost all of the energy being put into the flow is from expanding combustion gases - not the compressor stage. If you wanted to go at supersonic speeds using only spinning fans, you will need a heck of a lot of fans. Maybe we could do it! But we haven't so far.

I suppose one way to do so is to build an electro-thermal equivalent of a low-bypass turbofan, with a jet section to deliver high-velocity thrust and a fan section to deliver low-velocity thrust.

> supersonic aircraft have been flying with turbofans and no afterburners for almost five decades now

But part of a turbofan's thrust is from gasses from burning jet fuel and air expanded by the heat form that isn't it? Nobody has flown supersonic without burning fuel except in a dive, have they?

https://en.wikipedia.org/wiki/Fastest_propeller-driven_aircr...

So you can have an electric motor to power the fan, but what about the turbine part?

> Instead of burning fuel, you can use electricity (something like an arc welder) to generate heat.

Egads, no. Please get out of the business of being limited by thermodynamics in your engines. The Carnot cycle is a hard stop whenever heat is being coaxed into doing mechanical work. You don't want that.

Just convert electricity into mechanical work directly.

That's a great goal to have! But if you're putting energy into a flow using a propeller or fan, aerodynamic stall means that each propeller can only put a limited amount of energy in. This is why jet engines have so many compressor stages - each one adds as much energy as it can without stalling out:

https://en.wikipedia.org/wiki/Gas_turbine#/media/File:J85_ge...

In the engine pictured, which has 8 compressors in a row, the energy which those fans are able to put into the flow is miniscule compared to the energy that you can dump in by burning fuel (or electricity) in the tiny combustion chamber.

F-16 in afterburner is consuming 64,000 pounds of fuel per hour = 18 pounds per second A pound of Jet-A has 20 MJ per pound.

So that's 360 MW of thermal power. Even if you're only turning 10% of that into usable thrust, that's 36MW of power.

Here's what a 35MW power plant looks like: http://www.power-technology.com/projects/ctds_chp/ctds_chp5....

The people working on electric jets are well aware of the Carnot limit, and it's true that they don't want that. But for now, we'd need a lot of new tech to put 35MW of thrust power into a flow using electric motors and fans. Heck, we need a lot of new tech to put 350MW of power electronics onto an airplane!! My only point is that I don't think we should look down our noses at the people working on thermodynamic machinery. Until we can do better, they're the best we've got :)

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.

Planes might be able to afford sitting for hours if batteries are that much cheaper than aviation fuel.

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

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).

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.

Profit margins exploding is shortly followed by profit margins declining as everyone gets busy competing on cost. By any measure an airplane is a high cost asset, and increasing (or maintaining) utilization will be important.

> if fuel cost was suddenly zero

See my post here: https://news.ycombinator.com/item?id=12591666 electrical costs are higher than typical fuel costs.

A Concorde-load of fuel costs around $40k (100000 liters * $0.40/liter). From your numbers, a 90-minute recharge costs $550. So apron costs don't seem like the deciding factor.

> 100000 liters

That works out to approximately 1GWh. At $0.10/KWh divided by two because of worse efficiency, that's $50,000 worth of electricity.

So the electricity at $50k costs more than the $40k for gasoline. (Or about the same depending on the exact price.)

The bigger issue is a 90 minute recharge of .5GWh would require 333MW of power, which about half the total output of a typical power plant. i.e. not a chance in the world of that happening.

Can you imagine just grabbing the power lines on a typical power plant and plugging them in here and there?

There's also some consideration needed here of jet plane vs electric plane efficiency. From what I've read about Rolls Royce jet engines - it's a very serious contender. Anything that runs fast, hot and a lot of power needs very careful design.

My prediction is that you would need cooling for such large motors travelling at such high speeds and that too would drop your efficiency. The airframes get pretty got at those speeds and every electrical component with high power will generate it's fair share of heat too. You won't be able to keep the thing cool enough to fly for any period of time. I have MX Dynamixels sitting beside me that sometimes weld themselves shut because of the immense heat they generate. The bigger they are, the bigger the problem.

For now, the only viable method I see is low-speed, short journeys as somebody else suggested. Maybe these sorts of flights would be more viable where solar panels can be utilized to also work off some of that money and make recharging quicker and adding less weight.

I think your math is faulty.

An electric plane wouldn't need as much energy as a fuel burning jet because you only need to be turning the fan blades. Where a jet loses a lot of energy compressing the air, a electric jet would probably be more like a propfan or a ducted fan. The best jets are about ~35% efficient at turning energy in to forward speed. Assuming an electric motor is 80% efficient and the propulsion is 80% efficient, you'd be looking at 64% efficiency.

It's possible there are other factors reducing the efficiency of an electric motor, but I doubt they are worse than parity with the existing jets. Using your numbers, that means an electric plane would use $25,000 worth of electricity.

The typical plant outputs much more than 333 MW as well. As we move toward less fossil fuel use, infrastructure will better support our increased energy usage. When internal combustion engines were first introduced, someone easily could have said "Do you realize how many billions of gallons of fuel it will take to power all of that? Not a chance in the world of that happening!"

The state I live in has well over 100,000 MW of generating capacity. Given that scale, supplying energy to planes doesn't seem so ridiculous.

I'm willing to bet that we won't just be slapping electric motors in place of fuel turbines anyways. Plane designs will probably progressively move towards better suitability for alternative energy. Maybe electronic motors for extra energy during take-off, with enough reserve power for emergencies?

> Where a jet loses a lot of energy compressing the air

It does not loose energy from this. The compressed air expands afterward, returning almost all the energy.

> The best jets are about ~35% efficient at turning energy in to forward speed.

Where are you getting these numbers? I'm seeing much much higher numbers than that then I google it.

> Assuming an electric motor is 80% efficient and the propulsion is 80% efficient, you'd be looking at 64% efficiency.

Again, those numbers don't sound in the slightest bit correct.

> Using your numbers, that means an electric plane would use $25,000 worth of electricity.

What? Run your numbers again. I assumed 50% efficiency for Jets and 100% for electrical.

> The state I live in has well over 100,000 MW of generating capacity. Given that scale, supplying energy to planes doesn't seem so ridiculous.

It's not about the energy usage, it's about how do you connect the thing to an airplane. Do you plan to move cables the size of telephone poles? 100,000 volts?

Have you seen electrical substations? Does that look like the kind of thing you would put on an airplane?

On electric you have transmission losses, charge losses, discharge losses, losses in the motor controller and losses in the motors. Most batteries aren't better than about 80% charging and about the same discharging. So 0.8 to the fourth, or about 40%

How could parking "only the wings" for charging be significantly cheaper than parking the whole plane? In the unlikely case of superbattery airliners, infrastructure and logistics would change as much as the planes.

>> "...swapping wings..."

If you were going to do this, you wouldn't swap wings. Instead, you'd swap passenger compartments in and out of various airframes, probably with some kind of automated gantry. This would reduce airfield turnaround times by allowing boarding to be finished before deplaning begins and by removing baggage handling from the critical path of getting the plane back in the air. Then the batteries would be charged during maintenance on the tarmac or in a hangar. Though overall I'm a skeptic of electrical aviation.

Whether the economics of having two or more airframes would work remains to be seen. That's two of all the expensive bits.

I can see short haul, lower speed routes working with less radical battery approaches. Probably have to have multiple battery locations per plane for weight and balance.

I'm incredibly sceptical of SST and replacing Concorde.

> 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.

Remove the ?amp=true from the URL and you'll get the proper desktop version.

I don't understand why that's set, but thanks.

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.

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".

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.

High performance, low maintenance and supply, fragile. Military hypersonic UAV, anyone?

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.

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.

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.

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.

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.

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.

>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.

> 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.

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.

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.

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.

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.

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.

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 ...

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.

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 ;)).

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?

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

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

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.

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