To recap, based on financial statements the company:
used to be a "waste management" company that failed and was sold as a "public shell" to enable the formerly private company to go public and sell shares (the waste management business it was engaged in was an effort to commercialize a process to treat low-level nuclear waste developed by Russian scientists)
has $64 mil in debt apparently unrelated to aviation
has spent $3.8 mil on R&D for this project
has 8 R&D employees
only 2 of those 8 have any evident experience related to designing aircraft (pretty apparent from the "design").
Having recently watched several engineering videos on the limitations for electric flight I was surprised to see this article. As your comment points out, it certainly appears too good to be true.
Yeah, I see this kind of thing repeated any time Eviation comes up.
I don't believe them. The design is sound, if radical in the decision to be mostly-battery. And I think that's partly why people are so skeptical: it definitely goes counter to the industry grain. But it IS the right way to build a serious electric aircraft for regional/commuter passenger travel. Pressurized, extremely high lift-to-drag ratio, very high battery mass fraction, focus on high propulsive efficiency by ingesting boundary layer with the pusher propeller and countering wing-tip vortices with wing-tip propeller. The passenger count is also right, at the limit of FAR-23, allowing you to use a single pilot.
The only thing I would do differently is probably have a higher cruise altitude and higher aspect ratio wings (and probably counter-rotating dual-motor pusher propellers) instead of using wing-tip propellers and gettin, but theirs is a valid design choice as well.
So much group-think especially with the larger aerospace companies. They insist on hybrids for flight (notice how whenever Airbus or Boeing buy one of these exciting electric flight startups, they all of a sudden switch to hybrid?), which ends up compromising the design and adding a whole new propulsion system to validate and certify. Others have a valid approach of retrofitting electric onto older airframes, but that is not going to get anywhere near the operational efficiencies of a clean-sheet design. And still others insist on VTOL, but I have my doubts as to whether the focus on VTOL by so many of these electric flight startups is going to really be worth it in the end except for niche cases.
The design is "sound" ? It is ridiculous! Those engines are at each end of a wing. That is a 100% no no. They are feet from the ground, and would make one engine out operation impossible. Even someone with a cursory understanding of aerodynamic could see this is a ridiculous design.
The key is that the Alice aircraft is capable of take-off with just the rear propeller. That's possible because electric motors (unlike jet engines) can operate at much higher power for short periods of time. It was addressed recently at the Paris airshow Q&A for Eviation. If a wingtip motor (not engine) fails, the other side is designed to immediately stop (electric motors such as these respond immediately to input) and flight continues with the remaining tail motor.
Additionally, electric motors are fundamentally more reliable than jet engines.
Compare the number of propellers on NASA’s version. They have serious backup in the event any single engine fails.
Being able to take off with one engine that’s rapidly overheating, does not mean is safe to continue a flight with a single engine. Electric aircraft don’t get lighter in flight because they don’t burn fuel.
It’s possible that that could be the case, but it’s a poor assumption that it will be the case. Especially as it’s such a useful feature they likely would have mentioned it.
1. Rear prop strikes.
2. Wing tip prop strikes.
3. Wing tip inertia
4. Prop wash over a wing is a good thing
If (big if) this thing ever flies, it won't be in this form
Prop wash over a wing is good if you're lift-starved at take-off (which you aren't with this design). But otherwise it actually increases drag. Pusher configuration is superior in that you can ingest boundary layer air which has been slowed down by the fuselage and get an increase in efficiency. That efficiency gain is partially why pushers are often used in long-duration drones.
I had the impression that pushers were typically less efficient than pullers.
A puller takes advantage of the volume behind the prop taken up by the body of the aircraft to offset the loss of air volume caused by accelerating the air (Bernoulli's theorem). A pusher can't do that.
The opposite is true. The accelerated airflow over the body of the aircraft actually increases the drag whereas a pusher ingests the boundary layer from the fuselage and the suction also helps keep flow attached. The problem, however, is that turbine engines need a smooth airflow in order to operate efficiently, therefore they aren't suited for pushers as the wings (etc) produce an uneven airflow into the turbine core.
>Those engines are at each end of a wing. That is a 100% no no.
I assume they are at the end of the wings on purpose to deliberately interact with the wingtip vortices. The back prop is power, those wingtips are for drag reduction.
As someone who regularly pilots a piston-single, I'm looking forward to what hybrid or full electric can do for us little guys. The takeoff phase of flight is a high-risk situation in events such as fuel contamination which could prove fatal.
Having a small buffer, even a few minutes of battery power to rely on while trying to get back to the field to land the "impossible turn" [1] would make me feel a lot better and could be the difference between life and death.
There are various groups (Pipstrel[2], Diamond[3]) that I'm aware of that are working on electric GA aircraft. For young pilots that are looking to train, the cost of jumping in a Cessna 172, the gold standard in GA trainers will cost at best $120-200/hr. Electric costs should be 1/5 (or better) of that in reality due to the absolute bargain of replacing a TBO electric engine, scheduled maintenance and relatively low level of complexity.
As someone with a similar background, I find the cost argument idealistic: I can fly a 172 for 100 EURO/hour ($110) any time, while a smaller plane (Cessna 152 or an LSA) are about the same price, even if the LSA fuel consumption is half or less. I am looking at options to fly cheaper for a decade, there is very little elasticity in the price per hour versus fuel price, especially in Europe; the market is not competitive enough, the offer is small, the demand is small, the prices are staying high no matter what.
Electric trainers should be a dream - cheap and safe; but they are not :(
I've seen the Pipistrel at EAA a few times. It seems to be a real product, but flight time is quite short, even though it's basically a sailplane with an engine. That's why they're billing it as a trainer.
As others have noted, electric flights require a major breakthrough in the battery technology. Here are energy density numbers for gasoline, jet fuel, and lithium-ion batteries:
Gas and jet fuel specific energy density ~= 45 MJ/kg;
Lithium-ion specific energy density < 1 MJ/kg
Even worse, a jet engine is much better at generating power. A modern high-bypass turbofan engine can generate 10 kW/kg whereas an electric motor is around 1 kW/kg.
In short we need much better batteries and much lighter motors. This is not going to happen anytime soon. A more reasonable option is to create carbon-neutral fuels (biofuels, carbon sequestration, etc.).
This is constantly repeated, but it's not true. I work in the field of electric motors for electric aircraft, and the amount of nonsense constantly repeated on the Internet about how electric flight cannot be done without a breakthrough is breathtaking.
Electric motors can achieve FAR greater than 1kW/kg. Here's one used sometimes on electric aircraft capable of 10kW/kg, same as a jet engine: https://emrax.com/products/emrax-268/
The specific energy of lithium-ion is poor, but jet fuel's USEFUL specific energy is more like 10-15MJ/kg due to needing to be burned. There's also some efficiency improvement possible, i.e. from airliner lift-to-drag of 16-20 (and like 8-10 for a Cessna) to a more glider-like L/D of 25-35 (the best gliders can do 70). Additionally, improved modern materials means you can just have most of your take-off mass be battery, compensating for the poorer specific energy (general aviation craft are only like 10-15% fuel, but 777s can be almost 50% fuel, and electric aircraft could be 60% battery).
So if you combine efficiency improvements and high battery mass, sure, electric planes still may have a tenth the range of jet liners. But jets like the 777 have a range of 10,000 to 15,000km. A tenth of that is still over 1000km! Quite doable for a very large portion of domestic flights. Since domestic flights often involve multiple hops anyway (due to hub and spoke model), you could fly basically anywhere up and down the eastern seaboard in just the typical two hops. And faster than high speed rail.
But of course, there are already better lithium batteries that are available in small quantities, like lithium-sulfur, metal electrode lithium batteries, solid-state batteries, or batteries that combine those various features. ~1.5MJ/kg cells are already demonstrated and you can buy them on an evaluation basis. ~2MJ/kg is feasible as well, enabling single-hop flights all over the eastern seaboard and enabling multi-hop transatlantic flights (as low as 1200km is the minimum range needed for transatlantic flights if you really wanted to do it).
> jet fuel's USEFUL specific energy is more like 10-15MJ/kg due to needing to be burned.
New turbofans have efficiencies close to 50%, so it's more like 20 MJ/kg. Also, you need to take into account the prop efficiency for electric planes. Beyond Mach 0.5, the efficiency degrades very rapidly. So it's not just electric motor vs jet engine.
> more glider-like L/D of 25-35 (the best gliders can do 70).
This is not limited to electric planes. The reason no one has done it so far is the aeroelastic divergence.
> improved modern materials means you can just have most of your take-off mass be battery, compensating for the poorer specific energy
Again, this can be done for any aircraft, not just the electric ones.
> as low as 1200km is the minimum range needed for transatlantic flights
Do you really believe there is a market for 1200km hops at Mach 0.5. We already have ATR 72 and Bombardier Q400. Why no one is using them for long haul flight?
>New turbofans have efficiencies close to 50%, so it's more like 20 MJ/kg.
Depends if we're talking LHV or HHV. Additionally, we're talking smaller jet fueled vehicles which rarely have access to state-of-the-art efficiency.
>Beyond Mach 0.5, the efficiency degrades very rapidly.
In this case, we're talking Mach 0.5 or less.
>this can be done for any aircraft, not just the electric ones.
Didn't imply otherwise. The highest performance jet plane can fly literally around the world. But this is far more performance than anyone needs in an aircraft. And for whatever reason (partially because of aging fleets, at least for very small commuter aircraft), generally there have been efficiencies left on the table still, just the same as conventional car makers left efficiencies on the table which Tesla and the like have taken advantage of.
> Do you really believe there is a market for 1200km hops at Mach 0.5.
For domestic flights, yes. For transatlantic, no, not a large market. Not as long as jet planes aren't paying for their climate externalities.
>We already have ATR 72 and Bombardier Q400. Why no one is using them for long haul flight?
Because those have the same maintenance requirements and use the same fuel as jets, which are just as efficient and faster.
I don't think we'll do many transatlantic electric passenger flights until the climate externalities are priced-in for the cost of air travel or until lithium-air or similar. But now we've moved the goal posts to long-haul and transoceanic flight. Electric flight is clearly possible and for domestic flights it'll likely be cost-competitive even without fully accounting for climate externalities, particularly for these 9 passenger FAR-23 electric aircraft competing with fuel-guzzling and maintenance-heavy 40 year old fleets.
> > improved modern materials means you can just have most of your take-off mass be battery, compensating for the poorer specific energy
> Again, this can be done for any aircraft, not just the electric ones.
Not only that: you burn the fuel, so for the second half of the flight you only need to carry half the fuel. But you have to carry the full battery mass (modulo E=mc^2) all the way.
Well, that’s in part a point for the batteries, though. You spend a lot of energy to lift all that fuel that you just blow out with all its potential energy up in the air, whilst the batteries provide you with that very potential energy on the way down as well.
Glider planes quiet commonly are filled with water to make them heavier so they can make more use of the potential energy they gain from the externally powered take off and so that they can bridge longer distances without lift generating upwind.
Would electric towplanes be doable for passenger aircraft? (Long or short haul, electric or otherwise).
If one of the downside of electric planes is the range, while fuel is cheap, making them cheaper to operate, and take-off uses a significant portion of the total energy, I could see very powerful electric towplanes as a way to reduce the amount of fuel needed for takeoff. This would:
* Allow to travel longer distances with the same amount of fuel (enabling electric airplanes to fly longer distances). Alternatively, allow planes to fill up with less fuel for the same distance.
* Improve fuel efficiency of big airliners, and their carbon footprint if you consider regular ones.
One last question: aircraft that fly shorter routes typically embark less fuel, but would that be doable with electric planes?
Actually, gliders with water ballasts have the same L/D full or empty. The difference is that they can fly faster when the tanks are full, but they don’t travel larger distances
That's not a point for batteries. I cannot imagine a circumstance where, during cruise or even descent, you'd wish that you'd be carrying more mass (except possibly to have a higher AoA and thus higher V_a if you want to fly through turbulence faster).
Indeed, there are various ways to handle "staging" of aircraft, including parachuting batteries, electric towplanes, assisted groundlaunch, piggyback, etc. These may have niche uses, particularly for cargo flights, but I suspect that will only happen if 1) jet air travel pays for its full climate cost and 2) we stop making any progress in battery technology.
Taking seriously the idea for a moment: you don't consume batteries one at a time, they are in various degrees of parallelism. Also the balance of the plane is affected by mass ejection.
Transatlantic electric flights wouldn't be too hard. 1200km minimum hops could be done with next-gen battery tech and plenty of margin.
...Transpacific (i.e. reaching Asia from North America) wouldn't be too hard as you can hop along Alaska and the Aleutians, but reaching Hawaii is a major challenge. To get to Hawaii from LA takes 3800km (at the edge of what you can do with L/D of ~40-50 and 500Wh/kg batteries). Taking the long way from the Aleutians to Midway cuts that down to 2600km for the minimum hop distance, which is perhaps feasible with a sailplane-like L/D and the next-generation lithium-metal and/or lithium-sulfur batteries (that are already demonstrated at the lab scale).
Lithium-air is the breakthrough in battery tech people want, which will enable much easier transpacific flights at transonic speeds (rather than the ~Mach 0.50 speeds you'd be limited to for the most extreme high performance airfoils), like what people are used to already. Lithium-air would also potentially enable long distance supersonic electric passenger aircraft.
I haven't seen the 1.5MJ/kg batteries but that is still pretty far from 10MJ/kg. Your first paragraph seems pretty hostile considering this fact.
Look, we all want electric aircraft. I can't wait for them. But to say that it doesn't require a major (honestly several major) breakthrough (s) is an extreme understatement and does not requisite the hostility you are giving.
The key thing often missed is that jet fuel is much better than it needs to be, particularly for domestic flights.
Batteries don't need to equal jet fuel in order for electric air travel to be viable.
We have airplanes capable of 15,000km trips. But we were making transatlantic flights back when our aircraft could only do about 2000km range reliably. Going from from Labrador, Canada to Greenland to Iceland to England, the minimum hop distance is about 1200km. https://en.wikipedia.org/wiki/Transatlantic_flight#/media/Fi...
I don't expect electric air travel to operate Transatlantic flights with 1.5MJ/kg batteries as major competitor to jet travel unless there's a very hard clampdown on greenhouse gas emissions. The logistics of adding major stops in Greenland and northern Canada to enable transAtlantic electric flight just likely won't be worth it. But for domestic flights (which are the majority of flights), electric air travel will be common.
Most of these discussions I see, at least on HN, seem to understand efficiency. Yeah, a lot of fuel goes into heat and not into power for the engine. People understand that. But another thing that many people don't, is that heating isn't wasted energy. It is reclaimed for heating the cabin and deicing. Which icing is a HUGE problem on aircraft. Heating is also fairly power intensive.
But still, until we get into that efficiency range of batteries vs direct power of jet fuel, it is far from solved. But like you mention with greenhouse gasses, it does have to be solved. I have yet to see anyone here that is doubtful that electric aircraft will exist. I just see people (at least on HN) that are either bearish or bullish. But don't be hostile to people that are being bearish. We need both camps.
Also -- it's pretty easy to be negative. "That's dumb, it's not going to work", etc... I really appreciate this poster remaining positive in the face of OVERWHELMING negative feedback on this thread.
Batteries don't produce nearly as much heat. And like I said, we need both camps.
And I don't think you should take my comments as "that's dumb, it's not going to work." You should take them more as "we still got a way to go but we've made a lot of progress. But don't bet all your money on this horse."
It's not negligible for its weight. You can always scale up an electric motor. The largest machines in the world (such as bucket wheel excavators) are driven by electric motors. Additionally, electric motors are much simpler to cluster into a distributed propulsion configuration than jet turbines are. That's why NASA's building the X-57 electric aircraft.
I think the biggest point that you and others that bring this up is missing, is not just how electric designs gives you higher efficiency and close the gap (as others have mentioned).
The main thing you're missing is that modern jet planes have absolutely ridiculous range, and a huge number of flights use only a fraction of that range. Electric planes don't need to match modern jet planes to be viable. They just have to compete on cost at a range that covers a significant amount of routes. And electric planes have a potential for huge cost advantages.
A related aspect is that electric planes are much more quiet. Being cheaper to operate and more quiet means you can fly smaller planes from smaller local airports to other small airports. You can create an entirely new market.
Electric planes are not going to take over transatlantic flights any time soon. But they don't have to in order to have a huge impact.
I do agree that carbon neutral fuels are important for long-haul flights for the coming decades. With batteries for land transport and short-range ships/ferries and planes and hydrogen for heavy trucks and ships, we might be able to sustainably make enough carbon-neutral fuels for long-haul planes.
> A related aspect is that electric planes are much more quiet.
I'm not so sure! Have you ever heard the sound of twin-turbo regional airplanes in small airports? That sound is not from the turboprop engine, but from the propeller itself. Electric planes do have propellers and propellers are usually very loud. Actually much louder than turbofans!
Making propellers quieter has been an active field of research in fluid dynamics for decades but it's a very hard problem.
Many smaller propellers can replace a few bigger ones. They'll make noise but not nearly as much as huge twin props. Another thing is that electrical propellers only make noise when you need them to produce thrust. Most traditional props produce noise just sitting on the ramp waiting for their oil temperatures to rise or while slowly taxiing to the runway. Another difference is that the high pitched whine of an electrical engine is very different from rumbling of a jet or piston engine. As I'm writing this, I hear a jet plane taking off from an airport 6 miles away from my house. I doubt I'd be able to hear an electrical plane from that distance.
Illustrative anecdote: when you hear a lightplane or ultralight with a high-rpm 2-stroke engine and a reduction drive turning a slower prop, up close you hear the high whine of the engine, but when it gets farther away you hear only the prop, a much lower sound. It's amazing how much of the sound is from the propeller.
Even medium range flying is tough to accomplish with near-term electric technology. A flight across the United States would involve 10 hours of flight time, assuming you did it in a single leg, which of course you cannot. Three stops, so probably 15+ hours total. People do seem willing to take one-stop jet rides across the U.S. now, but the gold standard is about 5.5 hours for a non-stop flight.
Why would a transcontinental flight be the relevant comparison here? The real disruptive/comparitive market is the DC <-> NYC <-> Boston corridor. I'm sure there are similarly busy and small corridors in the EU.
> flights use only a fraction of that range. Electric planes don't need to match modern jet planes to be viable. They just have to compete on cost at a range that covers a significant amount of routes.
You do know plane routes have diversions and holding pattern minimum times set by the FAA?
1 kW/kg for electric motors looks a bit on the low side for me. Tesla Model S with the highest power rating has 581 kW, and I don't think that its motors weigh in for more than half a ton combined.
I've found a statement that some version of their motors with 270 kW weigh 31 kg (70 pounds). Which amounts to 8.7 kW/kg and isn't far off from your 10 kW/kg estimate for modern turbofan engines. Also it's probably not the latest number for an electric motors, and newest motors have better power-to-weight ratio.
I stand corrected. I also found Emrax 268 which has a power to weight ratio of 10 kW/kg. But these are good only for small aircraft. It's much harder to maintain this power-to-weight ratio for larger motors. Emrax 268 is only 20kg, but a single engine of 777 weighs 8200kg. The ballpark for large motors at powerplants is currenly around 1 kW/kg [1]. But who knows; there might be a breakthrough in motors too.
You can stack Emrax motors on a shaft. Also, the technology scales up in diameter. Not that you really want _that_ large props necessarily, if you can get away with smaller ones. This combination should be enough, I guess.
Edit: I think I met the guy behind these. But I'm not sure, for lack of having asked for the name of the company. I certainly have seen a prototype that could have been the 348.
Generally you should prefer few large propellers over many small ones due to aerodynamic efficiency. Stacking up motors axially sounds like a very good idea though.
Electric motors can enable something which jet fuel and gasoline cannot: beamed power. There could be a new class of vehicles which only have a small onboard power store for emergency purposes. The weight savings would be about 20%.
Is this something that someone has actually fleshed out with real numbers? The infrastructure and efficiency problems involved seem at first glance to be extremely challenging.
The ATC systems required would be prohibitive, rest in peace any birds that fly into\through the beam, maintenance of the towers, and emitter tracking would all be huge problems.
Also, where/how is all that electricity getting generated/transmitted to the emitter, and what complications does that introduce? What about environmental conditions? How does that effect the efficiency? Does a storm front blowing through suddenly make regular ICE planes a better idea again?
Oh, yeah, don't forget the security aspect. Those emitters are more than 'interesting' enough to be weaponized in the wrong hands.
I mean, beamed power sounds cool and all, but you actually have to take into account a heck of a lot of variables first.
As long as we're discussing beamed power, why not have just enough power to reach cruising altitude (presumably above any clouds), then use solar panels to continue flight? This would admittedly limit long-distance flights to just daylight, but still better than what is currently possible.
Let's run the numbers for say a Boeing 767. It has a wing area of 290 m^2 and the main fuselage of 5 meter width and 60 meter length, so lets assume another 200m^2 of surface area. 490m^2 of solar panel can generate 0.2 * 490m^2 * 500W / m^2 = 49 kW.
Compare that to the 800kW that the APU in the tail supplies to keep electric and hydraulics running if the main engines fail or the well above 200 MW that the main engines put out.
i think battery swapping is much more realistic for planes than for cars and that would allow to use non-rechargeable or factory rechargeable batteries like the metal-air ones (my favorite is Al-air) which is order of magnitude better than rechargeable Li-ion, and that really gets us close to the gas/jet capabilities given the low thermodynamic efficiency (or extremely high price and complexity) of the combustion based engines.
>In short we need much better batteries and much lighter motors. This is not going to happen anytime soon.
this is exactly what is happening right now in front of our eyes :)
One interesting idea but not likely workable, have an electric launch platform that simply has the actual passenger plane as its cargo and once sufficient speed is reached it drops off to circle back on its own for another go.
could work with either propulsion method of the plane being lifted.
Making Methanol from electricity is not too hard. You can also make a kind of diesel with electricity as energy source. These processes have fairly terrible efficiency of course, compared to batteries, but are useful for applications where you absolutely need high energy density fuels.
What’s the reasoning behind your statement? I think both are already being done, the economics are just not there yet. Digging up free energy from the ground is just too cheap.
The scale of co2 that would need to be sequestered is massive, I don't think anyone has a vaguely viable plan of how that would be done.
Most attempts at biofuel are not even net positive on energy. if we did get there then the question is how much forest do we have to clear to grow biofuel AND eat, and what net effect does that have on co2.
There are a lot of things that electric planes will not be able to do unless there are drastic changes in battery technology. They can still fill a niche for short flights with very little cargo/person capacity.
Your analysis would be more compelling if you added some $$$ here and there. The savings in maintenance and fuel are really what's driving this technology.
By this logic, the several products in that are currently in the process of being certified are physically impossible. The more reasonable explanation is obviously that your numbers are in fact wrong (or at least your interpretation of them) and that within two years from now, several companies will be shipping the battery powered planes with exactly the ranges, weights, and specs they are currently advertising and that they are working to get certified.
E.g. the Eviation Alice carries ~8000 pounds of battery and provides its nine passengers a range of 650 miles. That's undeniably a lot of battery and the energy density is indeed not great. However, it doesn't prevent it from flying. Transporting 9 people over that kind of distance for the price of charging that battery is a very disruptive cost improvement over the state of the art that involves burning hundreds of dollars worth of fuel.
It's the cost of fuel that's going to kill jet and piston engines. It doesn't matter how energy efficient they are when the cost difference with battery electric in the first generation is already two orders of magnitude. And while we have pretty much peaked in terms of fuel cost efficiency (order of magnitude improvements seem unlikely), that is definitely not the case for battery electrical. Cheaper and lighter batteries are basically happening. 2-3x seems to be likely within a decade or so. More may come after that. Electricity prices are also not a constant and seem to be dropping rapidly. So, if it's economical now, it's going to be far more economical in a few more decades. I think another two orders of magnitude cost improvements are likely.
For the same reason, hybrid planes are not likely to be more than a stop gap solution. They'd still be burning a lot of fuel which would raise the cost relative to small battery powered planes. I do believe that they will have an important role for longer distances; for the simple reason they'd definitely provide better energy efficiency. Ultimately, synthetic fuels generated using dirt cheap electricity may help bring prices down here but this will take a while and is not likely to be a very efficient way of using electricity (compared to storing it in a battery and using it directly).
As soon as battery powered planes are range competitive, which for short haul is happening right now, orders of magnitude cost improvement means game over for traditional planes.
Here's some back of the envelope math for you for the Eviation Alice vs the A319. You can buy a state of the art A319 for about 110M $. That same amount of money buys you about 30 Eviations (at the announced price of 3M $). You only need about 18 to match the number of passengers of an A319 (160 passengers). The A319 is very popular on short haul flights that are well within the range of an Eviation Alice. The difference is that one burns thousands of dollars worth of fuel and the other has an operational cost measured in the lower tens of dollars. There are of course many other advantages replacing big A319s with small battery powered planes. E.g. they make less noise and they can fly to much smaller airfields. The point here is that we don't need an electrical version of the A319. Big planes are only interesting because of the fuel economy. Small electrical planes don't have that problem.
The biggest bottleneck is actually not going to be batteries, engine efficiency, maintenance, or electricity cost but pilot wages and production volume of these new planes: we'll need a lot of them and with the cost of electricity already being low, pilot cost is going to be the dominant thing. As cost drops, ranges improve, and production volumes go up, the business case for operating an A319 will rapidly disappear. The Eviation arguably already challenges that. Autonomous flight, which is another thing Eviation is working on, will accelerate this. IMHO most A319s shipping today will be retired years or decades before their normal projected end of life because of their operational cost vs the cost of products like this.
This is why Eviation has a full order portfolio. They'll be selling these things as fast as they can build them. Others will follow. This is only the first generation of their product. I expect great things from them and their competitors in the years to come.
I fly gliders. Absolutely can't wait until my local club finally decides to get an electric single-seat self-launching glider, preferably with enough endurance to do some additional tens of kilometers after the launch, in order to avoid landing out if the weather dies out. It's a gamechanger with regards to both costs and convenience. No towplane, towplane pilot, no outlandings.
How about a battery that can glide by itself? You attach a big battery for the launch and once you are up you disconnect and it glides back to the airfield. That should be possible today technically. Not sure how safety would work.
Oh, electric self launch planes are both viable and available already. It's just a question of manufacturers making them with slightly higher battery capacity, which seems perfectly feasible based on a napkin calculation. Current self-launch electric gliders can climb to cruise altitude and still have >20km of endurance as a contingency for recovery.
If that number was 100km with high reliability, it would almost qualify as a new type of aircraft. You could do cross-country flights that you'd never attempt in an unpowered glider, e.g. above big stretches of high, mountainous terrain. The Norwegian Hardanger plateau comes to mind as an example. Un-landable terrain, 1 km above sea level with a small window for unpowered navigation, national park and absolutely beautiful.
Well, we already have autonomous electric planes. I don't see why your idea shouldn't work. For the near term, remote control of the battery might be easier/more feasible.
I don't think so. You cant steer a parachute well and you don't want some bypasser to get hit by a heavy battery on a parachute. The descent speed on a parachute is very high so it will hurt or more.
I also started to fly gliders, and it would be lovely indeed to have electric self-launching glider, though unfortunately atm there are just too few of them, most popular are Arcus E and ASG 32 El, both are too new (cost a lot of money) and too rare. I wouldn't mind if our club get one, but it might be more economical to get a few other high performance gliders instead (like get two ASW 27 instead of one ASG 32 El) as it much easier to deal with them in a club context (doing 5+ launches per day, maintenance, etc).
Most likely a first viable step would be to get electrical tow plane first.
Self launching on batteries means carrying around a fair bit of dead battery weight for the entire flight. Electric sustainers (can't take off but can stay up) are pretty interesting because gliders take hardly any power to fly level. Example:
All this electric vehicle technology works really well for electric glider winches. You can get a whole lot of peak power off of a battery so you don't need a huge electric power feed.
I hope they get adopted by Formula E. A bank of ultra-capacitors in front of the main battery should make the cars lighter with stronger regenerative braking.
A battery fire is a scary prospect unless the fire can be effectively contained and the hot gases vented (I don't suppose extinguishing one is likely to be an option.) There has been at least one crash involving fire, though I have not been able to find out if it was a propulsion battery fire. [1]
In Eviation's Alice, the failure or shutdown of one of the wingtip's motors would require the shutdown of the other, on account of asymmetric thrust. It can be flown on the rear motor alone, but I do not know how well it would climb in the case of a motor failure on takeoff. Maybe an EE can step in and say whether electric motors can be over-powered for relatively short durations (in this case, a few minutes to return to the airfield) without much increase in the risk of it failing?
BTW, I see that this prototype is a tail-dragger, though rendered images show a tricycle gear.
Electric motors in their specs usually have an entry specifying a 30s or one minute window during which the motor can operate at around twice the power without damage.
In this state the motor cannot maintain temperature, so going beyond that time window will shorten its lifespan or cause damage if continued.
Hobbyst EVs often take advantage of this by having a small motor and overloading it when accelerating.
Parachutes. They are now a very practical option for GA aircraft. More than a few cessnas have been saved. The concept of "off-field forced landing" should too be going away.
"Q. How much damage will be done to my plane if I land it with a parachute?
A. In all likelihood the aircraft will suffer some significant damage. The terrain where you land will affect this greatly. Though the extent of damage has varied from plane to plane, most GA aircraft that have come down under a BRS deployment have eventually (or will soon) fly again."
Call me a skeptic until they provide hard numbers and details of what planes make it back into the sky v's scrapped, and those planes have a year or two of a service history showing they make it back into a reasonable service lifestyle, I'd be shocked to hear this is great at saving planes. I find a lot of the old 172's i fly have plenty of bumps and scratches, but wouldn't be super excited to trust the frame of a plane that went through an experience like this.
I like it from a safety perspective, but in my mind, the reward you get out of a system like this should be your life...I have zero expectations the plane will ever fly again.
It seems that, at least until fairly recently, most Cirrus aircraft that used their parachute were written off, and that is still the most likely outcome.
How many are written off is irrelevant. What matters is passenger lives. Success is measured in total number of not-dead people because of not crashing as violently.
In addition to the point verelo raised about the repair/replacement cost of having used a parachute (vs. replacing a motor), I was thinking specifically of a wingtip-motor failure at takeoff (typically the worst-case scenario), possibly too low for a parachute (some figures here: [1]).
This is a 9-passenger airplane, maybe too large for current recovery parachutes? (though I imagine that will change.)
Maybe, but that does not solve low-altitude problems, if indeed there is one. It is possible that two small-airplane sized parachutes will inflate faster than a single larger-airplane parachute, but apparently current small-airplane parachutes do not inflate fast enough to save you at low altitude.
Actually, this has me thinking: not all low-altitude situations are the same - an airplane with a downwards trajectory, such as one in a spiral dive, will need more height to save than one that is in a glide, such as after a power failure. This is why even a zero-zero ejector seat will not always save you, if you are descending rapidly at low altitude.
Even so, replacing a motor, if that is all it takes, is going to be cheaper than repairing or replacing an airframe that has undergone a parachute recovery.
With respect to engine failure at takeoff, low altitude begins at the point where, if the engine fails, you will not be able complete a landing on a runway (or overrun area, if there is one.) With respect to my original question, if the remaining engines give sufficient performance, using a parachute would not be the standard response even if you had the height and speed for it to work.
A quick google search shows a page from the FAA saying that typically a couple hundred planes crash each year, and a few hundred people die. There's an order of magnitude more GA planes than commercial airliners.
About the accident in Hungary: the police investigation has been apparently closed, and the cause was ruled to be pilot error (If I understand it correctly, they did a too severe turn too low). There was no sign of a fire before the crash, so even though the wreckage burned out, the crash was not due to electrical issues or fire. A hungarian news article: https://hvg.hu/itthon/20190401_magnus_aircraft_elektromos_ki... (Unfortunately I couldn't find an English article, and the accident investigation of the transportation safety organization might not be finished yet, since they only issued a preliminary report for now.)
Assuming battery swaps are the aviation "norm", it might be possible to design the aircraft so that the batteries could be jettisoned in an emergency. This would also give much better glide performance for the emergency, and make the possibility of parachute recovery a lot higher since suddenly there's half as much weight to bring down.
Why so few motors? Electric motors have low cost and low maintenance, so I would expect electrical planes to have many of them.
Overpowering the motor during the entire take-off would bring a high risk of having it fail too. But overpowering it to overcome the most common obstacles is perfectly viable in an emergency.
Anyway, about fires, they are a reasonably easy problem to deal with. Fires on liquid are much more dangerous than fires on solid, and batteries have a lower tendency of exploding and creating fumes than the gasoline that propels smaller planes. I imagine the largest problem of a fire would be on losing power. You can mitigate this by creating many independent battery banks, but this adds weight.
A fire in an airplane is a lot more scary than a loss of power (proportionally more so in a small airplane, where an off-field landing is feasible, and increasingly they have ballistic parachutes), while there is currently a well-known problem of fires (that can't be extinguished) in high-power-density batteries. Gasoline is dangerous, but we have learned how to handle it safely.
You could mount batteries on pods that could be released if needed. Additional benefit would be that the pods could be replaced on the ground by fully charged ones for faster turnaround.
One is actually supposed to use water for large lithium battery fires, Tesla recommends this. The lithium in batteries isn't elemental and thus does not react strongly with the water.
Interestingly most of the electric aircraft proposals and prototypes I've seen are basically scaled up quadcopters with multiple motors with directly attached props. Range is of course the big issue so the proposed companies are usually something like "fully autonomous aerial Uber", where you set a destination with an app on your phone and one of these big quadcopters flies over and lands near you. You get in and hit go and the thing flies to your destination, then back to a recharge pad. Only good for in-city trips, but potentially a quick (if expensive) way around traffic.
From the article: conventional fuel for a 100 mile flight costs $400, while electric energy would cost $12.
This seems like such a tremendous difference that the market would be in an arms race to make it a reality. Especially considering electric motors have fewer moving parts and so require less maintenance. Oh and it would be so quiet.
> Even assuming huge advances in battery technology, with batteries that are 30 times more efficient and "energy-dense" than they are today, it would only be possible to fly an A320 airliner for a fifth of its range with just half of its payload, says Airbus's chief technology officer Grazia Vittadini.
> "Unless there is some radical, yet-to-be invented paradigm shift in energy storage, we are going to rely on hydrocarbon fuels for the foreseeable future," says Paul Eremenko, United Technologies chief technology officer.
> The big problem with this is that 80% of the aviation industry's emissions come from passenger flights longer than 1,500km - a distance no electric airliner could yet fly.
The market would be in an arms race if energy density was sufficient for long haul flights. Electric flight is awesome but until energy storage/density gets closer to hydrocarbons, conventional planes aren't going anywhere for the majority of travelers and cargo.
A320 family range varies from 5500km to 8700km, so "a fifth of it's range" is around 1500km, which is 80% of the industry emissions.
I'm not sure of that quote either -- a lithium ion battery is currently about 1MJ/kg and 1MJ/litre. Jet fuel is 43MJ/kg and 35MJ per litre (values from from wikipedia)
So a battery that's 30 times more energy dense will be in the region of jet fuel, and thus would presumably be able to fly an A320 for its current range with its current payload.
To do current payloads at 1/4 range (what you'd need for those flights under 1500km) at A320 payloads, you'd need batteries to presumably be in the 5-10 times as dense level, and that's the range that lithium-air batteries would sit.
Don't forget that the fact that the fuel is burnt up as you travel is a big factor in the range of an aircraft. The weight of batteries does not go down during the flight.
How much does this affect an aircraft range? I assume the mechanism is that lighter aircraft needs less lift, and less lift means less drag, less drag - less power on the engines - less fuel consumption - more range.
I somehow always thought that more weight of an aircraft lessened its range almost only because it needs much more power to take off and gain a cruising altitude.
The 80% figure are flights longer than 1500 km. 1500 and less are the 20%.
So even if all those flights were switched to magic zero emission electricity, the aggregate improvement over the whole industry would barely beat the relative improvement between a 737 NG and a MAX. (yes, this is an apples to orchards comparison)
That's not strictly correct. There are MAX's flying every day. At this moment, there are two in the sky.
Grounded from carrying passengers, but not grounded entirely from flying, and certainly emitting in any case. The two on the map now are out of Boeing Field.
> Jet fuel is 43MJ/kg and 35MJ per litre (values from from wikipedia)
Jet fuel is really about 12-15 MJ/kg when you take thermodynamic losses into account. So you;d need a battery 10 times as dense. Which likely isn't happening any time soon, but still.
I think with full electric aircraft it's not a case of 'won't work' but how big of a niche they can carve out. Probably the sector they'd compete in are general aviation and puddle jumpers.
This is why I'm so excited for lithium-air batteries. Theoretically they'd carry ~40.1 MJ/kg, which is very competitive with gasoline's ~46.8 MJ/kg. Factoring in the higher efficiency of electric drives (95% vs. 35% for say a regular ICE car), you'd be getting effectively over double the energy per pound in terms of moving you around.
At nearly double energy efficiency, nobody will care much about the weight of the batteries. Some airplane design changes due to no longer being able to take off heavier than they are allowed to land (this is common on long hauls) but the design changes also likely change due to better placement of thrust and its weight (engines go almost anywhere the designer wants), and better control over location of the weight (batteries aren't liquid and don't slosh around, and a sloshing liquid also has negative aerodynamic effects.)
It's a game changer for airlines such as Harbour Air in British Columbia and Mokulele Airlines in Hawaii. These are small regional airlines which operate from the water or from small airports with flight times usually less than an hour, and most of their operational expenditures are in fuel costs. Typically for these airlines you show up 15 minutes before the flight and there is no security screening, so it's very hassle free.
Think of what it could do in other areas as well too though. Imagine a flight from the SF waterfront to Tahoe via seaplane in 45 minutes (instead of 4+ hours) with no TSA screening, or potentially even SF to LA in 90 minutes.
Unfortunately the battery weight is also currently prohibitive for small companies such as Harbour Air and Mokulele.
Several weeks before the Harbour Air / MagniX announcement I ran through an exercise to determine the range/payload of an electric Cessna 208 (Caravan) for a typical flight profile here in the bay area: the daily FedEx flight from Oakland International to some nearby city, such as Petaluma. This involves a 5min climb from take-off to 2000ft, some period of cruise flight (ultimately determined by range), and a 7min decent to land.
This calculation assumes that the C208 swaps the swaps its turbine (PT6A-114A) for the Magni500, saving 85lbs. It also accounts for the substantial increase in conversion efficiency between the MagniX and PT6 (roughly 0.94 from 0.32). Not accounted for are any differences in aircraft systems (de-ice, prop pitch, electric instruments, plumbing, etc).
The results are not surprising given what others have noted about the enormous difference between the specific energy densities of Jet A and LIB. At the specific energy density of today's production batteries, 250 w-hr/kg, the electric C208 could carry one 175lb pilot approximately 100mi in 39min. Due to FAA VFR regulations, this would in reality limit the flight to 9min (FAA requires daytime reserve of 30min), with the subsequent loss in range.
Let's consider the putative solid state battery at 500 w-hr/kg. Now a 60min flight time (really 30min plus 30min reserve) will allow 1080lb payload. Fantastic! That's a pilot plus 4-5 passengers. The catch, of course, is that the timeline for road worthy SS batteries is 5-10 years. How long for before an air worthy battery is available?
With this information parsing the press statements is a little easier. Will the Harbour Air / MagniX Beaver carry 6 passengers over a 30min flight? No. It may demonstrate electric flight of a utility category air frame with the pilot as the "soul" payload. After that both companies will likely be in the same position as the rest of us -- waiting on better battery technology.
> The XF-84H was almost certainly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as the "Mighty Ear Banger". On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away. Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down.
It would make about as much noise as it makes now. Nearly all the noise of a commercial aircraft is caused by the air being pushed to propel it, not by the engine internals.
(You can reduce noise and increase efficiency by pushing more air at a smaller speed. You do that by having more engines or larger ones. I would expect electrical planes to have more engines, but that's a small secondary effect.)
I think the big question would be how much the base equipment costs and the significant power density limitations. It takes time to get established against a very mature technology and batteries are a big limiting factor:
“Even assuming huge advances in battery technology, with batteries that are 30 times more efficient and "energy-dense" than they are today, it would only be possible to fly an A320 airliner for a fifth of its range with just half of its payload, says Airbus's chief technology officer Grazia Vittadini.”
I'm sure everyone would like to switch for environmental reasons but that sounds like a really big gap to fill.
Own a single engine piston that's fuel efficient. In my plane 100 miles would be about $40 in fuel conservatively. Amortized maintenance costs are much higher than $40, but still not even close to $400. The article mentions a Caravan which is a bigger single engine turbine, not piston.
Fewer moving parts doesn't mean reliable and not subject to catastrophic unforeseen failures. If it hasn't been out for five years you're a test pilot.
REDMOND, WA and VANCOUVER, B.C. – March 26, 2019 – magniX, the company powering the electric aviation revolution, and Harbour Air, North America’s largest seaplane airline, today announced a partnership to transform Harbour Air seaplanes into an all-electric commercial fleet powered by the magni500, a 750 horsepower (HP) all-electric motor.https://news.ycombinator.com/item?id=19539796
Um, that’s comparing a jet engine to an electric prop. Apples and walnuts - the two propulsion methods couldn’t be much more dissimilar. A more equivalent prop plane (with similar capacity) would be well under $100 for fuel costs, potentially even under the $50 range.
I wonder if with electric we can fly higher like much higher maybe 80k to 90k since we don’t have to worry about the engine stalling. Could this also make the flight times comparable or faster? For sure less turbulence. As someone who lives on a flight path I’m eager for the change in noise pollution too- though I’m worried the transition will take decades...
You can't really go above the Armstrong limit (~60k feet) in a passenger airplane without adding huge complexity in handling the event of cabin pressure loss.
Pressurized cabins are going to be essential for electric flight to have any kind of reasonable speed (and range).
It shows that the most impressive electric aircraft specs are for the pressurized Eviation Alice (1000km, minus margin for contingency, and 250 knots cruise). If you stay low enough to not require pressurization, then you have to compromise the lift to drag in order to have a decent cruise speed or you have to tolerate a really low cruise speed.
Altitude is essential. Bite the bullet and build a pressurized cabin so we can get on with replacing fossil fuel aviation with full electric. https://www.eviation.co/alice/
Doesn't have to be above the Armstrong Limit, but it sure does help to be above 10,000 feet.
Eventually we'll have supersonic electric aircraft. To have sufficient efficiency, they'll need to be at or above the Armstrong Limit, like Concorde. (And perhaps higher, like the 96,000 feet record holder for horizontal powered flight, NASA's Helios... which just happens to be electrically powered. https://en.wikipedia.org/wiki/Helios_Prototype .)
EDIT: High altitude enables you to use an extremely efficient airframe with sailplane-like lift to drag but STILL achieve high cruise speeds. For instance, the Perlan II glider actually has no engine and is able to soar higher than any towplane, above 76,000 ft where it flies at about 250 knots (actual airspeed). Without any engine at all. https://www.youtube.com/watch?v=NnpE5xS1g80
All passenger jets have pressurized cabins, but they are working at lower pressure differentials than what you need above 60k feet, and they sometimes fail, with oxygen masks being the fail-safe.
If you go above 60k, and the plane experiences a rapid loss of cabin pressure, you have 60 seconds to restore cabin pressure before the passengers start dying. So the failsafe system will have to be massive. That increase in weight and complexity isn't worth the efficiency gains.
You mention Concorde, and indeed it had a very substantial failsafe system even though it only touched the lower end of the limit. Concorde had really small windows, so even with two windows gone it took some time to equalize pressure. The pilots had positive pressure oxygen masks, and the plane had the ability to drop altitude immensely fast in an emergency.
I see that does making exceeding 60k pretty scary. I was from London to Denmark and we had cabin pressure loss I think we were maybe at 30k and dropped pretty fast to 20 if I recall correctly. The sensation that I remember was slow motion and shock from the flight attendant as the masks did not deploy. Later after landing the captain told us during preflight they set the cabin pressure incorrectly such that as we went too high an emergency system kicked in the prevent the cabin from exploding... I was maybe 12 so the details are fuzzy but definitely the take away is cabin pressure loss is no joke
Hard to puzzle the details there without knowing the aircraft type, but in the pressurized piston plane I fly, there is a main outflow valve used to regulate pressure that's under my (indirect) control and a safety outflow valve that's set just over the rigged max pressure differential (such that it partly dumps the cabin if that pressure is exceeded).
Given that your flight didn't get the "rubber jungle" of deployed masks, the cabin pressure probably never dropped precipitously low, but rather started to oscillate as the safety valve dumped and closed, but never dumped enough to deploy the masks and the crew declared and descended in order to sort things out.
A small number aircraft (non-airliners) are lost each year due to pressurization issues. It's a serious business, even in the high 20s and 30s (of 1000' MSL).
Single pilots are required to continuously wear O2 mask at/above FL350 (35000') and one pilot of a two pilot crew must continuously wear O2 over FL410. Between FL350 and FL410, two pilot crews may rely on quick-donning masks. This is believed to be a commonly violated regulation (in that air crews regularly do not wear the required mask when things are operating smoothly).
> This is believed to be a commonly violated regulation
I believe that is an understatement. I've heard it described as the most commonly violated rule in aviation. There are a number of youtube pilots who commonly violate this rule seemingly without too much worry.
"Engines stalling" is not really the factor that limits altitude. The problem is that the thinner the air, the faster you have to go to stay up. Eventually the required speed enters the transsonic region, and you start needing way more power. There comes a point where your engines just don't have the oomph to push you fast enough to stay up. If you want to go higher, there are basically two ways - more oomph, and better wing loading (i.e. less weight or bigger wings.)
Electric aviation has many merits, but being a lightweight source of plentiful oomph is not currently among them.
Engines don't stall, planes do. Plane stalls are about aerodynamics, and nothing to do with the engine.
Current engine designs operate poorly at higher altitudes for a number of reasons: less air density meaning less oxygen to burn and less air to push against. Turbine engines can flame out, which maybe that's what you were referring: https://en.m.wikipedia.org/wiki/Flameout
Stalling is a term also used with engines, and it's pretty clear he's talking about engines not working at altitude so "stall" is probably the correct term
Yeah I’d imagine most of the reasons sited from this hat wiki article don’t apply to an electric plane. But yeah air density would definitely be an issue but I thought the nasa Helios flight showed 90k to be the upper limit? So figured pushing to bear that altitude could be achieved and possibly beneficial since it would avoid bad weather and reduce drag... I guess was imagining the bulk of the engine power would be consumed at the start of the flight to reach altitude and then from there mostly glide until descending to land... but I’m not an aviation engineer at all just dreaming of quieter sky’s and less pollution
In my estimation, the shortest practical path to less pollution (at least less net carbon emission) is to use electricity to synthesize jet-fuel. Take yesterday's carbon dioxide, turn it into tomorrow's jet fuel, making the fuel carbon-neutral.
Although electric motors are capable of very high power density. If the flight is substantially shorter than the full range, flying at a faster speed, or higher altitude may be practical.
I know nothing about Eviation other than what this article says. They're claiming 650 miles of range with nine passengers on batteries, and to that I will not say I'm merely skeptical. I'm saying they are flat-out liars selling bullshit, and I'll stake my engineering reputation on that statement.
I was reading the article with stunned disbelief at the BBC's lack of fundamental feasibility verification. And then I was unpleasantly surprised that I had to scroll down so far here on HN to see someone call out the bullshit.
From the exaggerated numbers for aviation fuel cost to the ridiculously low cost of electricity all the quoted numbers are obvious lies.
Not to mention that a back-of-the envelope calculation shows that the aircraft would never be able to take off due to the weight of batteries required for a 650 mile range.
You would be absolutely right in staking your engineering reputation on calling bullshit and I would happily join you.
> I'll stake my engineering reputation on that statement
Such forceful claims should not be made anonymously. I'm with you on the claim itself but feel that if you want to make that statement and stand by it that you should do so with your name and 'engineering reputation' attached to the claim itself.
I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene.
The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.
Yeah I have wondered about this option as well. Hydrogen fuel cell cars make very little practical sense for a lot of reasons, but most of those reasons don't seem to apply so much when you're dealing with air travel:
- It'll be a long time before fuel cells are cost competitive with gas or electric cars, but for planes the cost of fuel and operation is much more significant than with a car, so the upfront cost for building the plane seems less significant in comparison
- Refueling infrastructure is much easier to implement at a (relatively) small number of airports than it is to build many small consumer refueling stations everywhere
- Space is more important than weight in a car, but the opposite may be true for a plane
- Crash safety is a much bigger problem for cars than planes - plane crashes are rare, and if a plane crashes there's a good chance everyone dies anyway, but if you're designing a car you're going to have to be really careful to make sure every other fender bender doesn't result in a hydrogen explosion
Of course there's the issue that most hydrogen today is created from fossil fuels, but perhaps there are ways to generate it sustainably and still remain competitive with the cost of jet fuel?
Electric cars can be a very competitive alternative to gasoline cars, but electric batteries are not yet energy-dense enough to make long-distance air travel viable, so it feels like hydrogen planes might be the least bad solution if we want to get off of fossil fuels.
> if a plane crashes there's a good chance everyone dies anyway
That's actually not the case. Overall your odds of surviving an accident in a plane are something like 95%. Still above 50% for "serious" incidents. Sure, if the plane drills the ground everyone is going to die, but planes crash somewhat regularly with most/all surviving.
Also one of the most dangerous places to be in a plane, statistically, is on the ground. A surprisingly large proportion of historic fatalities in air accidents have been crashes on the taxiway or runway between two aircraft (eg plane lands on top of another or taxis across a live runway when it shouldn't do).
I wonder what a YC application with such an idea might look like. Design the plane and the fuel containment/loading systems at 2 airports. Start America's first "carbon free" aviation route. Maybe move freight instead of people at first for an easier regulatory pipeline. It's absolutely crazy and would almost certainly fail but so are most of the revolutionary startup ideas that deal with earth heating in any meaningful way.
We can basically have "carbon free" aviation today if we want it by manufacturing synthetic liquid hydrocarbon fuels using renewable power. The US military has already run successful experiments. It works fine, it's just more expensive than burning fossil fuels.
To store enough hydrogen to be useful you probably need it in liquid form like rockets use. Hydrogen is energy dense by mass, but not by how much space it takes up compared to liquid fuels.
Otherwise you'll have a really giant bag of gaseous hydrogen which does help your bouyancy, but then you've made an airship instead of a plane and a spark accidentally turns it into the Hindenburg.
Liquified is the only option, I think. Compressing it into cylinders or storing it as a metal hydride is probably way too much weight.
Until recently, making hydrogen by electrolysis was not a benefit, environmentally, as a lot of the electricity would have come from fossil fuels. I think decomposition of methane is an option that would allow the carbon to be sequestered.
As a gas at 1 atmosphere, wikipedia says 0.011 MJ/L, compared to jet fuel at 35 MJ/L. You'd save weight (it weighs less than air so this would make you float) but need 3000x as much space if it's not compressed.
Compressed at 690 bar (about 680 atmospheres) it goes all the way up to 5 MJ/L, only 7x as much volume of fuel required compared to jet fuel. But the tanks to pressurize something that much are presumably very heavy and not a reasonable solution in an airplane.
Liquifying it gets that up to 10 MJ/liter and I don't think you need as much pressure to store that (as long as you keep it very very cold).
Per weight instead of volume you beat jet fuel (by 3-4x), so that aspect is a win. Having enough volume to store it and keeping the storage equipment light are the challenges.
Counterintuitively enough liquid ammonia packs more hydrogen than liquid hydrogen per unit volume - also it condenses at -33C (-27.4F), so it actually wouldn't require cooling once in the air.
It can be burned in a gas turbine, but for now the NOx emissions are pretty horrible.
The penalty for more volume is rising with higher speed, whereas the penalty for more weight is staying pretty much constant. In a fast plane, volume is just as important as weight, if not more.
Its so bad that only the largest space rockets use liquid H2. All the others use kerosene or the like.
Either way, the Soviets tried gaseous fuels in the 80s - See Tu-155. They ran on liquid H2, CNG.
If I recall, the weight increase didn't make it practical. On the other hand it was a turbine powered plane. It might work out with fuel cells (although you'd need a big and heavy compressor to run it)
1kg of kerosone can be kept in a plastic tank that weighs nothing. 1kg of hydrogen has to be kept in a pressurized, pure-lead 70kg bottle, and even then hydrogen will diffuse through it in just few weeks. So to take 1kg of hydrogen with you you're taking a lot of weight in the tanks too.
Some rockets use hydrogen and their pressure vessels aren't so heavy as to keep them stuck on the ground. You only need to contain the hydrogen for hours, not weeks.
Few though, and only the largest ones and they have incredibly complicated and long (and dangerous - imagine having to deal with refueling a cyrogenic liquid after every leg) fueling.
Most rockets use hydrocarbons for this very reason.
The relative weight of the tank decreases with volume and the aircraft doesn't need to hold the fuel for more than the duration of the flight. The idea is not without merit.
Shape will be more interesting - storing the fuel within the wings is not a very bright idea in this case.
Yes, and they could be supplied by electric conductors just as easily.
The ones that aren't supplied by pipelines have trains or fleets of trucks supplying them. Those would see a gain on using water, electricity and some mildly expensive machinery.
Of all the very relevant problems of using hydrogen on planes, long term storage is not one of them.
When you do steam methane reforming to produce hydrogen, separating out the CO2 is a necessary step in the process. Then it's just a matter of storing it underground, rather than just emitting it.
Are there any commercial examples of carbon sequestration? We've heard that line for decades now, if it's real there should be plenty of production sites by this point.
It would be much harder to engineer: you'd need a hefty tank; cryogenic fuel handling to increase density and lower tank weight.
Safety is critical on aircraft. Hydrogen is difficult to contain, and has very low viscosity due to its small molecules. It burns with an almost invisible yet very hot ultraviolet flame. It easily mixes with air to form an explosive mixture and has a very low minimum ignition energy (about a tenth of gasoline).
Combustion of hydrogen in a heat engine for propulsion would be very inefficient compared to a battery electric. Fuel cells are in between, at about 40-60% efficiency, but have a substantial weight cost.
Rather than mess around with hydrogen, with the proper mandates a lot of jets could switch over to renewable jet fuel. One of the main leaders here is, surprisingly, the US Navy: http://www.altenergy.org/new_energy/seawater-into-jet-fuel.h... directly from seawater and nuclear energy from a ship's reactor, or various other biofuel initiatives.
The Navy does a lot of this. They funded a program to make biofuels from algae.
But don't forget that the stated purpose of funded research is often a lie[0] and this is not necessarily viable outside the lab.
[0] You get other benefits from the research including subsidizing your national industry, training your workforce, doing research you're interested in with a more politically palpable purpose.
My dad worked at a company that was researching hydrogen (probably for scram jets). Problem he said with hydrogen is the size of the fuel tanks starts negatively impacting the amount of payload you can carry.
Hydrogen production is either not carbon neutral (from ?natural gas?) or isn't particularly efficient to produce once you tack on transport with electrolysis losses.
liquefied methane/natural gas would be a much better choice. The energy density per volume is about 2/3rds that of jet fuel and higher per weight. It's slightly less efficient to produce from electricity than hydrogen.
Well to increase safety one can use a fuel like ~methanol with a regular ICE, no need for electric conversion or reformation, just a new carburetor! i was suggesting NH3 because it is much more dense and involves NO carbon at all. Like i said farmers regularly deal with NH3 ... so it can be safely handled.
Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would be nice if for some reason it will happen sooner.
PS: *small in capacity. I do know that for example Solar Impulse is the biggest aircraft by wingspan.
>I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes.
The whole point of electrifying flight is that it makes small aircraft economical for airlines. The future of inter-city transport will be light aircraft with less than 20 passengers flying out of of small regional airports. Driving to LAX and waiting in security to get on a huge jet and fly for 90 minutes to SF sucks, but so does the drive. We're stuck with two terrible options there. Driving to a tiny airfield and hopping directly onto an electric plane that costs the price of a bus ticket will change everything about the way people live. They will never replace turbine engines for long haul routes, but the vast majority of commuter flights will be completely electric within 30 years.
The answer is - railway ;) . I doubt that small craft (any prop type) will ever be so quick overall - they are aircrafts and require all aircraft related checks and control, safety for passengers, safety from passengers etc. And about price I don't know, maybe it will be slightly cheaper than jets. So you'll have slightly cheaper businessjet prices, which are still astronomical.
Rail is an option in less developed countries, or places like Europe and Japan where the easements have existed for centuries. But building a new high-speed rail line in the US is basically a nonstarter at this point.
Electrified aviation will be more than 10x cheaper vs turbine based. Practically the entire cost of aviation is in the engine, with its' associated fuel logistics, maintenance requirements, and pilot training.
No, the longer we wait, the more expensive it will become. The population of the US is increasing and it's almost all going to cities. We should be building rail ASAP to meet the needs of now and the future.
Maybe we need federal legislation to make it less of a hassle to build a new rail line but we should focus on actually solving the problem. I don't see how thousands of 20-person electric airplanes is a scalable solution.
High-capacity / High-speed rail is a non-starter over low-capacity planes with a bunch of low-capacity airfields littering the country? Density is the future and a bunch of small electric planes will not come anywhere close to meeting the demands necessary.
It will take a lot longer than 30 years to develop and certify such aircraft, then build out the infrastructure. Small general aviation airports just aren't set up to handle a bunch of passengers. A minor decrease in fuel costs won't have a transformational effect. And passenger security screening will still be required.
Flights are cheap because airlines cram hundreds of people into a huge plane. That's the only way jet travel is economical; small jets are incredibly expensive to operate by comparison. The entire need for security arises from the fact that you are being put in a massive plane with hundreds of other people. If you make light aircraft travel economical, you get rid of the need for security as well.
Electric wheel propulsion on aircraft seems like an entirely unnecessary feature. Airplanes have no difficulty using their primary form of propulsion - moving air - to move on the ground, and it takes very little energy to do it compared to the energy required to move through the air while off the ground.
No, that's exactly backwards -- jet engines are far less efficient at low speed than at cruise speed. Various numbers I found say 100-300 kg of fuel used taxiing for single aisle planes like 737 [0][1] all the way up to two tons of fuel for large aircraft like 747 at large airports like JFK [0].
This can be extremely relevant for shorter flights: "[taxiing] aircraft fuel burn which is estimated to be as high as 27% of total fuel burn for a 90-minute flight where waiting in queue adds to the time on the ground" [2]
The taxi fuel is not primarily used for motivation of the airplane around the airfield, but just from idling the engines. (It's about minutes of ground operation more than miles of ground operation.)
Electric drive wheels don't eliminate that unless you don't start the engines until near the hold short line (in which case, you don't have air conditioning or electric power, meaning you end up running the APU [itself a small jet engine] to provide that power).
Yes, you'd need at least enough battery power to power not just the drive wheels, but the other things that engine power provides for like air conditioning. I wonder how large a pack would actually be required (of course there are huge differences between airports - some of them youre in the air only a few minutes after leaving the gate, some it can be 20-30 minutes).
If it was a large amount of battery, it would be cool if the batteries were in a small autonomous vehicle that disconnected from the plane when it was time to spin up the main engines and returned on its own to be recharged. Seems like a solvable problem.
Anecdote, but relevant, we were on the ground in Las Vegas in a 787-400 (an all-electric, no-bleed airplane) and due to a 15 minute ground hold while they sorted an issue with a brake indication, the APU powered pack alone was not able to keep up with the Vegas environmentals. (They couldn't run a main engine because they were doing maintenance in that area.) They were able to bring in ground-based chillers to take some of the edge off, but it was uncomfortably hot in the cabin with an APU running.
A 787 may be ideal for an electric conversion (since it's already a no-bleed airplane). Even then, you probably might as well run the APU for electrics on the ground, since you're going to be carrying around that amount of weight anyway.
That's an another win for electric and hybrid electric designs. For the latter if you can safely take off on battery power you don't need to idle the engine before take off. Saves fuel, reduces noise, and localized pollution.
Propelling air to move on the ground is far less efficient than wheel propulsion. You have to give the air at least as much momentum as the vehicle, and without a very large propeller, this requires accelerating it to a high velocity, giving it much more kinetic energy than the vehicle itself. The energy use while taxiing can be substantial, and the range of electric planes is critical.
Wheel propulsion on the other hand can impart momentum at very high efficiency, as well as regeneratively brake.
I read years ago when it was first announced that price saving should be significant, also less machine hours for engines (longer maintenance intervals), less safety checks on the ground etc.
Would it make sense to jettison the discharged batteries shortly after takeoff to reduce cruising weight? The "takeoff battery pack" could be in some sort of autonomous drone that pilots itself back to the airport so it could be jettisoned after reaching cruising altitude.
Does weight make a significant difference once the aircraft is at cruising altitude?
Yes, planes for ages jettisoned any fuel before landing because of the weight. Keeping the landing weight down to a minimum does wonders for the airframe design.
Nowadays they just do a better job of loading only the fuel necessary, and circle pointlessly to burn excess fuel before landing. It's still an issue, they just don't dump the fuel on the neighborhood below like they used to.
I was thinking more about helping with the energy density issue, by discarding the discharged, yet just as heavy as when charged, batteries after reaching the energy intensive climb to cruising altitude.
A human can put out ~200W to the pedals (or 400 for an hour if you are among the best in the world). The amount of heat they put out when doing that is much more. The human body is about 30% efficient so if you are doing 200watts to the pedals you are putting out over 400w of heat. This can be a challenge for strong athletes on bike trainers in doors. you need a big fan, with somewhere for the air tog o.
Lack of turbine lag with an electric powered fan is probably a big deal. Means when the pilot decides he needs power now he gets it now. Not in a few seconds.
This plane wouldn’t even be capable of getting me to the closest aircraft hub at its maximum range, let alone with a safety margin (I live an hour and a half, by jet, from Denver). Not to mention it will be slow and badly impacted by storms (since it has an operating ceiling of 10,000 ft).
Which indicates that the "age of electric flight is not finally upon us". People have been putting electric engines in gliders for a lot more mileage and flight time for years.
They'd have to be shorter than 400 miles to be safe. At which point, it's probably just as fast to drive (or faster, given it's a prop plane whose speeds are in the ~200mph range).
My GF's sister lives in central Nebraska. 300 miles from Denver, 120 miles from Omaha. An electric airplane with 600 miles range would be 'fine'. Driving would cost about $150 when you include fuel, maintence, and depreciation.
https://twitter.com/BenBrelje_says/status/106485722028904038...
https://twitter.com/BenBrelje_says/status/106491195862390374...
To recap, based on financial statements the company:
used to be a "waste management" company that failed and was sold as a "public shell" to enable the formerly private company to go public and sell shares (the waste management business it was engaged in was an effort to commercialize a process to treat low-level nuclear waste developed by Russian scientists)
has $64 mil in debt apparently unrelated to aviation
has spent $3.8 mil on R&D for this project
has 8 R&D employees
only 2 of those 8 have any evident experience related to designing aircraft (pretty apparent from the "design").