7 ms·

I Sing the Airplane Electric

121 points by prostoalex 7y ago

rhombocombus 7y ago
There is a combination of increasing energy density of batteries and decreasing cost of high tech motors that I believe is a bellweather for electric flight experimentation, particularly on the LSA/ultralight end of aircraft. While I believe it is unlikely we will see energy densities on the level of gasoline anytime soon, I do think we will see a lot of innovative electric training aircraft soon. If lithium sulfur batteries live up to the hype then we might see even cooler designs.
- jeffreyrogers 7y ago
  I think there is some potential for hydrogen fuel cell powered planes since the energy density of hydrogen is significantly better than batteries.
  - bdamm 7y ago
    But not economic on any known horizon. For some reason fuel cells have repelled good economy (in dollars) for 15 years now.
  - tengbretson 7y ago
    The fact that H2 can't be stored as liquid, even under pressure makes me pretty doubtful. I suspect ethanol or plant-derived oil will beat out hydrogen for as long as batteries aren't up to the task.
    - jeffreyrogers 7y ago
      Yeah, I think that's more likely. But for all electric I think hydrogen makes more sense than batteries, since improving batteries enough for real applications requires new chemistries, while I think the obstacles for hydrogen are more about economics.
      - ecpottinger 7y ago
        No, look at the prices and requirements for a hydrogen storage tank, you either need a high pressure tank or one that can handle very low temperatures. Neither is cheap or simple.
        Hypx 7y ago
        For aviation purposes, it's cheap enough.
    - davedx 7y ago
      H2 can be stored as a liquid, it’s more difficult. Check out AeroDelft who are building a liquid hydrogen plane: https://aerodelft.nl/ https://aerodelft.nl/
    - sa1 7y ago
      There was some news about metal sponges earlier that may be able to hold high volumes of H2 under low pressure. https://www.bbc.com/news/science-environment-52328786 https://www.bbc.com/news/science-environment-52328786
      - mannykannot 7y ago
        You got me thinking, so I looked for some numbers. Hydrogen has a specific energy of 120 MJ/kg, while Kerosine has 46 MJ/kg. According to the abstract of the paper being discussed here, the new material has a deliverable capacity of 14% by weight, corresponding to about 17 MJ/kg - only a bit better than 1/3 that of kerosine, but considerably better than lithium ion batteries, which apparently achieve less than 1 MJ/kg, while the best-performing lithium-sulfur batteries are at about 1.8 MJ/kg. In addition, we must deal with this material only losing 14% of its weight as its hydrogen is used up, while kerosine loses all of its weight - a combustion-powered airplane becomes more efficient as its fuel is consumed. Furthermore, to get that 14% deliverable capacity, you have to start with it at 100 bar, so the tank containing it will have a substantial weight. So we have progress here, but not yet a substitute for liquid hydrocarbons.
    - Hypx 7y ago
      LH2 is a liquid. It's likely airplanes will use liquid hydrogen as a fuel.
  - snovv_crash 7y ago
    I think we're more likely to get working Lithium Sulphur batteries first, which would effectively relegate fuel cells to the garbage can. Between the fuel and the cells, batteries are just so much easier to operate once they're out in the field, there's no comparison.
    - Hypx 7y ago
      Lithium sulfur still has a tiny fraction the energy density of hydrogen. It's very unlikely, probably impossible, to ever beat hydrogen on energy density with a battery. Also, Li-S still has too low of energy density for airplanes, and given the long recharge time problem batteries fundamentally are a no-go in aviation.
      - snovv_crash 7y ago
        LiS is only 10x below gasoline. When you account for the difference in efficiency, and the the difference in weight for the motors, and then reliability and redundancy, it is roughly a factor of 2 away. That is fine for shorter routes. Recharging time isn't an issue, just have the batteries swappable.
- DoofusOfDeath 7y ago
  By training, do you mean for training beginner pilots? I would think there's a lot of benefit from learning on aircraft similar to what you'd pilot post-training.
  - jrockway 7y ago
    The fundamentals of flying can be learned in any aircraft. Pilots are already trained on "trainer" type aircraft, because they are more forgiving and more economical to operate than aircraft designed for another task. Yes, changing types will require some training, but it's a big savings if you can get your PPL in a plane with an operating cost of $1/hour. If you look at vendors that are selling production electric aircraft, they claim 70% savings on training operations. That's a big deal. (Link: https://www.pipistrel-aircraft.com/aircraft/electric-flight/alpha-electro/ https://www.pipistrel-aircraft.com/aircraft/electric-flight/...)
  - bityard 7y ago
    Almost every pilot starts their training in a Cessna because the basics of flight apply to every aircraft, and operating a small simple aircraft is far less cognitive load than sitting in the glass cockpit of a jumbo jet. An electric plane removes the complexity of operating the engine which is not insubstantial, even in the smallest of general aviation aircraft.
    - dreamcompiler 7y ago
      I kind of hate Cessnas. They feel dramatically underpowered to me. Sailplanes OTOH feel great because they have no engine at all. It--focuses the mind. I've probably learned a lot more about pure flying from sailplanes than from Cessnas. It just feels safer to me to have no engine and a good glide ratio than a small (potentially unreliable) engine and a poor glide ratio. Of course nobody's going to be commuting in a sailplane, but they're awesome for pure fun and learning piloting skills.
  - GuB-42 7y ago
    Managing the engine is not the most important part of flying, especially for ultralight aircraft. And in fact, the best pilots tend to be also experienced glider pilots. Also, one specificity of ultralight flying, or at least the way I was taught, is to not trust the engine, no matter how reliable it is supposed to be. One aspect is to make the final approach unpowered. Of course, the engine is still running, but ideally, you should pull the throttle all the way back and leave it here, as if the engine had failed. This is in contrast to the 3° slope commonly taught in general aviation. Of course, a pilot who only flew on an electric plane needs some time with a flight instructor in order to learn the quirks of gas engines, but that should be quick compared to the time it takes to actually learn how to fly.
- spitfire 7y ago
  Better still with an electric motor you have more options for motor placement. You don't have a big fat engine that has to be placed in the front[1]. The batteries don't have to sit in the wings, they can theoretically sit at the bottom of the plane making weight easier to manage. You also get more options for blade types. Like ducted fans. In short, your plane doesn't have to be designed around a fat gasoline engine and tanks. There's still constraints, but you get much more creative freedom. I expect when we see planes designed around the motor/batteries we'll see aerodynamics get electric planes into GA territory. EDIT: aerodynamic efficiencies. [1] Yes there's that tractor/pusher Cessna, no one liked it.
  - sokoloff 7y ago
    In a lot of ways, you prefer the battery weight to be in the wings. The main one is that it reduces the load on the critical wing-fuselage junction (the source of zero-fuel-weight limitations in larger aircraft).
    - spitfire 7y ago
      But now you have that choice. You can package things however you want, even in weird shapes. Not "has to allow liquid to flow downhill, even in rate 2 turn". I'll bet there's still wins to be found even with putting batteries in wings.
- jillesvangurp 7y ago
  Yes definitely. Most electrical planes currently in the process of certification are hardly using the latest & greatest in terms of battery technology. The reason for this is not that the technology is not there but that resetting the process of certifying the airplane and batteries extends the time to market by years and everybody is scrambling to get certified now so they can start fulfilling orders. Like with EVs, demand is not a problem for any of these manufacturers. This is true for Bye's eflyers, the Eviation Alice, the Pipistrel models, etc. These have modest but usable ranges (currently advertised) and are far enough in the development process that they might hit the market in some modest numbers in the next few years. But that's with battery technology of basically a few years ago. There's obvious room for improvement by simply updating the battery technology. 2-3x over the next decade is not an unreasonable expectation; the biggest hurdle is certification. The real thing to look for with electrical planes is range & operational cost. Yes it's annoying to not be able to fly 5 ours straight. But 2 hours is still pretty good. This would require doubling the power/kg for this plane, which sounds like it should be feasible; if not now than maybe in a few years. Also, turning a 100$ hamburger into a 5$ latte flight is going to be quite literally be the difference between being able afford to fly or not at all for a lot of people. GA flight is a really expensive hobby currently. I think what will happen is the experimental market exploding pretty soon. There's a critical mass of technology coming on the market and it's going to be very tempting for people to start building kit planes they can actually afford to fly. There are some fine examples of some daredevils on youtube flying some DYI contraptions already.
- edraferi 7y ago
  The article says Lithium Ion batteries deliver 1/15 the power per pound of traditional aviation fuel. That leaves a lot of room for improvement...
  - sojournerc 7y ago
    They also don't get lighter as they lose energy, which is key to large passenger jet operations. Large plants often take off heavier than the plane is rated to land normally expecting to burn that weight in flight.
    - llukas 7y ago
      We built fuel burning planes for last 100+ years. They're optimized to take advantage of burning fuel, it doesn't mean it is only option.
      - NikolaeVarius 7y ago
        What kind of HN comment is this? They're optimized for energy efficiency? Yes? What does this gotcha response even mean?
        llukas 7y ago
        All parts of plane are optimized to work with jet engine. For plane designed from ground up as electric fact that jets land lighter than take off is not relevant. It is only relevant if you want to retrofit electric engine on jet engine optimized chassis - which is not only possible way. Bit more info on how thought process goes: https://spectrum.ieee.org/aerospace/aviation/how-i-designed-a-practical-electric-plane-for-nasa https://spectrum.ieee.org/aerospace/aviation/how-i-designed-...
        mannykannot 7y ago
        Batteries have a much lower specific energy that hydrocarbon fuels to start with, and then that fact that the aircraft weight does not decrease over the duration of the flight is one more disadvantage (currently a second-order issue, given the first difference.) These are constraints that can be designed around, and you have more freedom to do so when designing from scratch, but doing so is not a optimization, it is a straightforward trade-off between weight and duration. There's no optimal hump on that line.
- msandford 7y ago
  If you weren't so worried about having a reasonably-sized airframe or high speed we're getting pretty close to significantly increased duration/range via solar. http://thundergull.com/specifications.htm http://thundergull.com/specifications.htm It's got 95sqft of wing and a top speed of 63mph. Drag is usually with velocity squared so going 1/2 as fast might only require 1/4 as much power. They state in the article that it takes 10kw to fly level. With 100sqft and an average 10W/sqft you're at 1kw. But cut the speed down to 30mph (2500W) and double the wing area (2000W) and you're very nearly at breakeven. The 11kw battery might then last you 10+ hours after accounting for the power required to climb out. Yes it'll end up being much more of a power glider than a "proper" airplane but that might be a lot of fun.
  - sokoloff 7y ago
    Drag force is quadratic with speed. Drag power is cubic with speed. (Power is force times an additional velocity term).
    - msandford 7y ago
      DOH! So if you went ~30MPH and had 25% bigger wings you'd probably have a solar glider then. Or ~40MPH (2/3 the speed) and double the wing size. Turns out that this is a thing: https://www.solar-flight.com/ https://www.solar-flight.com/
cagenut 7y ago
throwing a zero powertrain into a thundergull is exactly the kind of shit i'd do if I were one decimal place richer.
atourgates 7y ago
A bit more info on the specific setup here: http://sustainableskies.org/sas-2019-gabriel-devaults-clean-commute-electric-adventures/ http://sustainableskies.org/sas-2019-gabriel-devaults-clean-... Apparently, the entire setup is doable for less than $40K. Given the right circumstances (like, an airport at both ends and living in a place with generally nice, warm weather), it could be a fantastic tool for an affordable, fast commute. Here's another story by Gabriel about completing a 100-mile journey: http://inspire.eaa.org/2020/01/09/99-miles-on-batteries/ http://inspire.eaa.org/2020/01/09/99-miles-on-batteries/ (with recharging stops). It looks like the maximum range of his setup is 60-miles, but with what he considers a "safe" amount of margin, he limits his trips to 40.
- Shivatron 7y ago
  > ... it could be a fantastic tool for an affordable, fast commute. I understand the attraction to owning your own plane and buzzing merrily above the wheel-bound masses below on the daily, but I have to think it's a bad idea (avgas or electric). I think of all the times I've overslept, needed to be at the office unexpectedly, forgot to put some air in the car tires, should get that warning light looked at, etc... phrases that are usually at the start of an NTSB report. The beauty of airlines and charters is that you're paying them, at least in part, to tell you "no, we're not flying right now." Turns out it can be hard to do for yourself when your job depends on it.
  - vvanders 7y ago
    Yeah, as I've heard it described from other private pilots is that you should never have a hard requirement be in place X at Y time. In other words you should always be willing(and able) to cancel a flight under any circumstances or areas of caution.
    - toss1 7y ago
      Indeed! Checklists are key, but the pilot must be willing & able to take appropriate action when a checklist item fails or cannot be completed -- i.e., stand down & cancel, instead of "it should be fine...". That failure to cancel is two of the three items usually needed for a crash (the failure itself and the bad pilot decision).
anonymoustarget 7y ago
Here's an electric trainer you can buy- https://electricflyer.com https://electricflyer.com The founder (a fighter pilot) originally built a civilian fighter jet with Israel Aerospace Industries years ago. He also built an advanced solar electric UAV which DARPA is using to "ambitiously" try to recharge drones with a laser.
- scribu 7y ago
  You mean pre-purchase. No word on the final release date.
kumarvvr 7y ago
Is it not possible to add an efficient internal combustion engine, couple to a generator, lower capacity batteries and an electric motor to power these planes? Battery energy density is very less, but having a constant speed small, optimised IC engine to generate electricity from fuel could increase range and capacity of these planes.
- 0x8BADF00D 7y ago
  If it's an ultralight, why do you need an ICE? All of this will add weight and impede your ability to glide.
addHocker 7y ago
I think we are doing something very wrong with electric airplanes- namely, the idea, that you have to have one craft that has to archieve vtol lift off. My Question: Why? Why not a tug drone, that gets a plane up to altitude in a VTOL way, fly with full battery capacity and then land with a rotor arrest like a helicopter - with the tug long detached and returned.
- bencoder 7y ago
  That's a cool idea. Though I see no need to make it VTOL. A simple tug plane, like a glider tug but for passenger aircraft. Really nice thought!
  - Leherenn 7y ago
    The issue is that if you cannot take off yourself, you cannot abort a landing. So if you have to keep it, you're trading a bit of efficiency for a lot of complexity.
    - _Microft 7y ago
      The tug could be more like a powerbank. It would not physically pull the aircraft up but assist by providing power. The aircraft could launch on its own but it is advantageous to use a tug because this increases the range or energy reserves that the aircraft itself has. (outline of a launch: aircraft and tug are connected by cable before launch, both lift-off, gain altitude, cable is detached, aircraft moves on and tug returns to launch site)
      - Leherenn 7y ago
        Except you probably have another aircraft already landing, the slots are tight. Maybe you could have another shorter landing strip just for the tug, but again, that seems like a lot of complexity (i.e risk) for maybe a 20% increase in efficiency at best.
        7y ago
ogre_codes 7y ago
One of the biggest reasons I gave up flying is due to the extremely expensive nature of the hobby. Something like this with its sub $2/ hour cost would be very appealing to me. Also since it's an ultralight with a steep rate of climb, I might be able to take-off and land on my driveway. I'm particularly curious about how this would work with a hybrid glider or other aircraft with long glide paths where you could use the electric to get up to elevation and glide the rest of the flight.
- sokoloff 7y ago
  I spend more than $2/hr on my prop maintenance and over $1/hr on tires (and that’s for several hours average per flight). I’m skeptical that electric propulsion will revolutionize basic aviation training or reduce the costs to make it a commonplace activity as it appears to have been in the heyday of the 60s and 70s, which was well before my time.
  - ogre_codes 7y ago
    Yes, I'm greatly overstating the costs involved. But reducing the fuel cost from $35/ hour for a Cessna burning 10 gallons/ hour to burning $3-5/ hour worth of electricity would be a pretty big deal.
    - sokoloff 7y ago
      A C172 rents (including fuel) for $155/hr with steam gauges and $175/hr with a glass panel at my local flight school. Way less than half of that is fuel, and no one's getting rich leasing C172s to flight schools. I think you might see rentals come from $155/hr to $125/hr. I doubt you'd see them go under $100/hr, and I'm not sure that's enough of a difference to drive a material increase in student traffic or affordability. Believe me, I wish it would. I started flying almost 25 years ago and it was much nicer when the airports were busy and when trade professionals (plumbers and electricians) could afford to fly. Now, I mostly see doctors and tech people at the airport as new student starts and that's not enough to really sustain vibrant airport businesses.
p1mrx 7y ago
> You have to be careful of people standing around because when the master switch ... is on, the motor ... can silently spring to life at an inadvertent bump of the throttle. The commercial version of this should probably "idle" the propellers at 30 RPM or something... fast enough to notice, without burning much power.

121 points by prostoalex 7y ago

There is a combination of increasing energy density of batteries and decreasing cost of high tech motors that I believe is a bellweather for electric flight experimentation, particularly on the LSA/ultralight end of aircraft. While I believe it is unlikely we will see energy densities on the level of gasoline anytime soon, I do think we will see a lot of innovative electric training aircraft soon. If lithium sulfur batteries live up to the hype then we might see even cooler designs.

jeffreyrogers 7y ago
I think there is some potential for hydrogen fuel cell powered planes since the energy density of hydrogen is significantly better than batteries.
- bdamm 7y ago
  But not economic on any known horizon. For some reason fuel cells have repelled good economy (in dollars) for 15 years now.
- tengbretson 7y ago
  The fact that H2 can't be stored as liquid, even under pressure makes me pretty doubtful. I suspect ethanol or plant-derived oil will beat out hydrogen for as long as batteries aren't up to the task.
  - jeffreyrogers 7y ago
    Yeah, I think that's more likely. But for all electric I think hydrogen makes more sense than batteries, since improving batteries enough for real applications requires new chemistries, while I think the obstacles for hydrogen are more about economics.
    - ecpottinger 7y ago
      No, look at the prices and requirements for a hydrogen storage tank, you either need a high pressure tank or one that can handle very low temperatures. Neither is cheap or simple.
      - Hypx 7y ago
        For aviation purposes, it's cheap enough.
  - davedx 7y ago
    H2 can be stored as a liquid, it’s more difficult. Check out AeroDelft who are building a liquid hydrogen plane: https://aerodelft.nl/ https://aerodelft.nl/
  - sa1 7y ago
    There was some news about metal sponges earlier that may be able to hold high volumes of H2 under low pressure. https://www.bbc.com/news/science-environment-52328786 https://www.bbc.com/news/science-environment-52328786
    - mannykannot 7y ago
      You got me thinking, so I looked for some numbers. Hydrogen has a specific energy of 120 MJ/kg, while Kerosine has 46 MJ/kg. According to the abstract of the paper being discussed here, the new material has a deliverable capacity of 14% by weight, corresponding to about 17 MJ/kg - only a bit better than 1/3 that of kerosine, but considerably better than lithium ion batteries, which apparently achieve less than 1 MJ/kg, while the best-performing lithium-sulfur batteries are at about 1.8 MJ/kg. In addition, we must deal with this material only losing 14% of its weight as its hydrogen is used up, while kerosine loses all of its weight - a combustion-powered airplane becomes more efficient as its fuel is consumed. Furthermore, to get that 14% deliverable capacity, you have to start with it at 100 bar, so the tank containing it will have a substantial weight. So we have progress here, but not yet a substitute for liquid hydrocarbons.
  - Hypx 7y ago
    LH2 is a liquid. It's likely airplanes will use liquid hydrogen as a fuel.
- snovv_crash 7y ago
  I think we're more likely to get working Lithium Sulphur batteries first, which would effectively relegate fuel cells to the garbage can. Between the fuel and the cells, batteries are just so much easier to operate once they're out in the field, there's no comparison.
  - Hypx 7y ago
    Lithium sulfur still has a tiny fraction the energy density of hydrogen. It's very unlikely, probably impossible, to ever beat hydrogen on energy density with a battery. Also, Li-S still has too low of energy density for airplanes, and given the long recharge time problem batteries fundamentally are a no-go in aviation.
    - snovv_crash 7y ago
      LiS is only 10x below gasoline. When you account for the difference in efficiency, and the the difference in weight for the motors, and then reliability and redundancy, it is roughly a factor of 2 away. That is fine for shorter routes. Recharging time isn't an issue, just have the batteries swappable.
DoofusOfDeath 7y ago
By training, do you mean for training beginner pilots? I would think there's a lot of benefit from learning on aircraft similar to what you'd pilot post-training.
- jrockway 7y ago
  The fundamentals of flying can be learned in any aircraft. Pilots are already trained on "trainer" type aircraft, because they are more forgiving and more economical to operate than aircraft designed for another task. Yes, changing types will require some training, but it's a big savings if you can get your PPL in a plane with an operating cost of $1/hour. If you look at vendors that are selling production electric aircraft, they claim 70% savings on training operations. That's a big deal. (Link: https://www.pipistrel-aircraft.com/aircraft/electric-flight/alpha-electro/ https://www.pipistrel-aircraft.com/aircraft/electric-flight/...)
- bityard 7y ago
  Almost every pilot starts their training in a Cessna because the basics of flight apply to every aircraft, and operating a small simple aircraft is far less cognitive load than sitting in the glass cockpit of a jumbo jet. An electric plane removes the complexity of operating the engine which is not insubstantial, even in the smallest of general aviation aircraft.
  - dreamcompiler 7y ago
    I kind of hate Cessnas. They feel dramatically underpowered to me. Sailplanes OTOH feel great because they have no engine at all. It--focuses the mind. I've probably learned a lot more about pure flying from sailplanes than from Cessnas. It just feels safer to me to have no engine and a good glide ratio than a small (potentially unreliable) engine and a poor glide ratio. Of course nobody's going to be commuting in a sailplane, but they're awesome for pure fun and learning piloting skills.
- GuB-42 7y ago
  Managing the engine is not the most important part of flying, especially for ultralight aircraft. And in fact, the best pilots tend to be also experienced glider pilots. Also, one specificity of ultralight flying, or at least the way I was taught, is to not trust the engine, no matter how reliable it is supposed to be. One aspect is to make the final approach unpowered. Of course, the engine is still running, but ideally, you should pull the throttle all the way back and leave it here, as if the engine had failed. This is in contrast to the 3° slope commonly taught in general aviation. Of course, a pilot who only flew on an electric plane needs some time with a flight instructor in order to learn the quirks of gas engines, but that should be quick compared to the time it takes to actually learn how to fly.
spitfire 7y ago
Better still with an electric motor you have more options for motor placement. You don't have a big fat engine that has to be placed in the front[1]. The batteries don't have to sit in the wings, they can theoretically sit at the bottom of the plane making weight easier to manage. You also get more options for blade types. Like ducted fans. In short, your plane doesn't have to be designed around a fat gasoline engine and tanks. There's still constraints, but you get much more creative freedom. I expect when we see planes designed around the motor/batteries we'll see aerodynamics get electric planes into GA territory. EDIT: aerodynamic efficiencies. [1] Yes there's that tractor/pusher Cessna, no one liked it.
- sokoloff 7y ago
  In a lot of ways, you prefer the battery weight to be in the wings. The main one is that it reduces the load on the critical wing-fuselage junction (the source of zero-fuel-weight limitations in larger aircraft).
  - spitfire 7y ago
    But now you have that choice. You can package things however you want, even in weird shapes. Not "has to allow liquid to flow downhill, even in rate 2 turn". I'll bet there's still wins to be found even with putting batteries in wings.
jillesvangurp 7y ago
Yes definitely. Most electrical planes currently in the process of certification are hardly using the latest & greatest in terms of battery technology. The reason for this is not that the technology is not there but that resetting the process of certifying the airplane and batteries extends the time to market by years and everybody is scrambling to get certified now so they can start fulfilling orders. Like with EVs, demand is not a problem for any of these manufacturers. This is true for Bye's eflyers, the Eviation Alice, the Pipistrel models, etc. These have modest but usable ranges (currently advertised) and are far enough in the development process that they might hit the market in some modest numbers in the next few years. But that's with battery technology of basically a few years ago. There's obvious room for improvement by simply updating the battery technology. 2-3x over the next decade is not an unreasonable expectation; the biggest hurdle is certification. The real thing to look for with electrical planes is range & operational cost. Yes it's annoying to not be able to fly 5 ours straight. But 2 hours is still pretty good. This would require doubling the power/kg for this plane, which sounds like it should be feasible; if not now than maybe in a few years. Also, turning a 100$ hamburger into a 5$ latte flight is going to be quite literally be the difference between being able afford to fly or not at all for a lot of people. GA flight is a really expensive hobby currently. I think what will happen is the experimental market exploding pretty soon. There's a critical mass of technology coming on the market and it's going to be very tempting for people to start building kit planes they can actually afford to fly. There are some fine examples of some daredevils on youtube flying some DYI contraptions already.
edraferi 7y ago
The article says Lithium Ion batteries deliver 1/15 the power per pound of traditional aviation fuel. That leaves a lot of room for improvement...
- sojournerc 7y ago
  They also don't get lighter as they lose energy, which is key to large passenger jet operations. Large plants often take off heavier than the plane is rated to land normally expecting to burn that weight in flight.
  - llukas 7y ago
    We built fuel burning planes for last 100+ years. They're optimized to take advantage of burning fuel, it doesn't mean it is only option.
    - NikolaeVarius 7y ago
      What kind of HN comment is this? They're optimized for energy efficiency? Yes? What does this gotcha response even mean?
      - llukas 7y ago
        All parts of plane are optimized to work with jet engine. For plane designed from ground up as electric fact that jets land lighter than take off is not relevant. It is only relevant if you want to retrofit electric engine on jet engine optimized chassis - which is not only possible way. Bit more info on how thought process goes: https://spectrum.ieee.org/aerospace/aviation/how-i-designed-a-practical-electric-plane-for-nasa https://spectrum.ieee.org/aerospace/aviation/how-i-designed-...
        mannykannot 7y ago
        Batteries have a much lower specific energy that hydrocarbon fuels to start with, and then that fact that the aircraft weight does not decrease over the duration of the flight is one more disadvantage (currently a second-order issue, given the first difference.) These are constraints that can be designed around, and you have more freedom to do so when designing from scratch, but doing so is not a optimization, it is a straightforward trade-off between weight and duration. There's no optimal hump on that line.
msandford 7y ago
If you weren't so worried about having a reasonably-sized airframe or high speed we're getting pretty close to significantly increased duration/range via solar. http://thundergull.com/specifications.htm http://thundergull.com/specifications.htm It's got 95sqft of wing and a top speed of 63mph. Drag is usually with velocity squared so going 1/2 as fast might only require 1/4 as much power. They state in the article that it takes 10kw to fly level. With 100sqft and an average 10W/sqft you're at 1kw. But cut the speed down to 30mph (2500W) and double the wing area (2000W) and you're very nearly at breakeven. The 11kw battery might then last you 10+ hours after accounting for the power required to climb out. Yes it'll end up being much more of a power glider than a "proper" airplane but that might be a lot of fun.
- sokoloff 7y ago
  Drag force is quadratic with speed. Drag power is cubic with speed. (Power is force times an additional velocity term).
  - msandford 7y ago
    DOH! So if you went ~30MPH and had 25% bigger wings you'd probably have a solar glider then. Or ~40MPH (2/3 the speed) and double the wing size. Turns out that this is a thing: https://www.solar-flight.com/ https://www.solar-flight.com/

cagenut 7y ago

throwing a zero powertrain into a thundergull is exactly the kind of shit i'd do if I were one decimal place richer.

atourgates 7y ago

A bit more info on the specific setup here: http://sustainableskies.org/sas-2019-gabriel-devaults-clean-commute-electric-adventures/ http://sustainableskies.org/sas-2019-gabriel-devaults-clean-... Apparently, the entire setup is doable for less than $40K. Given the right circumstances (like, an airport at both ends and living in a place with generally nice, warm weather), it could be a fantastic tool for an affordable, fast commute. Here's another story by Gabriel about completing a 100-mile journey: http://inspire.eaa.org/2020/01/09/99-miles-on-batteries/ http://inspire.eaa.org/2020/01/09/99-miles-on-batteries/ (with recharging stops). It looks like the maximum range of his setup is 60-miles, but with what he considers a "safe" amount of margin, he limits his trips to 40.

Shivatron 7y ago
> ... it could be a fantastic tool for an affordable, fast commute. I understand the attraction to owning your own plane and buzzing merrily above the wheel-bound masses below on the daily, but I have to think it's a bad idea (avgas or electric). I think of all the times I've overslept, needed to be at the office unexpectedly, forgot to put some air in the car tires, should get that warning light looked at, etc... phrases that are usually at the start of an NTSB report. The beauty of airlines and charters is that you're paying them, at least in part, to tell you "no, we're not flying right now." Turns out it can be hard to do for yourself when your job depends on it.
- vvanders 7y ago
  Yeah, as I've heard it described from other private pilots is that you should never have a hard requirement be in place X at Y time. In other words you should always be willing(and able) to cancel a flight under any circumstances or areas of caution.
  - toss1 7y ago
    Indeed! Checklists are key, but the pilot must be willing & able to take appropriate action when a checklist item fails or cannot be completed -- i.e., stand down & cancel, instead of "it should be fine...". That failure to cancel is two of the three items usually needed for a crash (the failure itself and the bad pilot decision).

anonymoustarget 7y ago

Here's an electric trainer you can buy- https://electricflyer.com https://electricflyer.com The founder (a fighter pilot) originally built a civilian fighter jet with Israel Aerospace Industries years ago. He also built an advanced solar electric UAV which DARPA is using to "ambitiously" try to recharge drones with a laser.

scribu 7y ago
You mean pre-purchase. No word on the final release date.

kumarvvr 7y ago

Is it not possible to add an efficient internal combustion engine, couple to a generator, lower capacity batteries and an electric motor to power these planes? Battery energy density is very less, but having a constant speed small, optimised IC engine to generate electricity from fuel could increase range and capacity of these planes.

0x8BADF00D 7y ago
If it's an ultralight, why do you need an ICE? All of this will add weight and impede your ability to glide.

addHocker 7y ago

I think we are doing something very wrong with electric airplanes- namely, the idea, that you have to have one craft that has to archieve vtol lift off. My Question: Why? Why not a tug drone, that gets a plane up to altitude in a VTOL way, fly with full battery capacity and then land with a rotor arrest like a helicopter - with the tug long detached and returned.

bencoder 7y ago
That's a cool idea. Though I see no need to make it VTOL. A simple tug plane, like a glider tug but for passenger aircraft. Really nice thought!
- Leherenn 7y ago
  The issue is that if you cannot take off yourself, you cannot abort a landing. So if you have to keep it, you're trading a bit of efficiency for a lot of complexity.
  - _Microft 7y ago
    The tug could be more like a powerbank. It would not physically pull the aircraft up but assist by providing power. The aircraft could launch on its own but it is advantageous to use a tug because this increases the range or energy reserves that the aircraft itself has. (outline of a launch: aircraft and tug are connected by cable before launch, both lift-off, gain altitude, cable is detached, aircraft moves on and tug returns to launch site)
    - Leherenn 7y ago
      Except you probably have another aircraft already landing, the slots are tight. Maybe you could have another shorter landing strip just for the tug, but again, that seems like a lot of complexity (i.e risk) for maybe a 20% increase in efficiency at best.
      - 7y ago

ogre_codes 7y ago

One of the biggest reasons I gave up flying is due to the extremely expensive nature of the hobby. Something like this with its sub $2/ hour cost would be very appealing to me. Also since it's an ultralight with a steep rate of climb, I might be able to take-off and land on my driveway. I'm particularly curious about how this would work with a hybrid glider or other aircraft with long glide paths where you could use the electric to get up to elevation and glide the rest of the flight.

sokoloff 7y ago
I spend more than $2/hr on my prop maintenance and over $1/hr on tires (and that’s for several hours average per flight). I’m skeptical that electric propulsion will revolutionize basic aviation training or reduce the costs to make it a commonplace activity as it appears to have been in the heyday of the 60s and 70s, which was well before my time.
- ogre_codes 7y ago
  Yes, I'm greatly overstating the costs involved. But reducing the fuel cost from $35/ hour for a Cessna burning 10 gallons/ hour to burning $3-5/ hour worth of electricity would be a pretty big deal.
  - sokoloff 7y ago
    A C172 rents (including fuel) for $155/hr with steam gauges and $175/hr with a glass panel at my local flight school. Way less than half of that is fuel, and no one's getting rich leasing C172s to flight schools. I think you might see rentals come from $155/hr to $125/hr. I doubt you'd see them go under $100/hr, and I'm not sure that's enough of a difference to drive a material increase in student traffic or affordability. Believe me, I wish it would. I started flying almost 25 years ago and it was much nicer when the airports were busy and when trade professionals (plumbers and electricians) could afford to fly. Now, I mostly see doctors and tech people at the airport as new student starts and that's not enough to really sustain vibrant airport businesses.

p1mrx 7y ago

> You have to be careful of people standing around because when the master switch ... is on, the motor ... can silently spring to life at an inadvertent bump of the throttle. The commercial version of this should probably "idle" the propellers at 30 RPM or something... fast enough to notice, without burning much power.