Why battery-powered aircraft will never have significant range

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daveklingler

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We have a huge, mature and well figured sorted infrastructure to deliver fossil fuels to the point of use with little geographic spacing. How that got to be such a bad thing eludes me still. Saving the planet with Teslas is not happening.
You went from airplanes to ships to cars. Like other engineering projects, airplanes and watercraft require a question first: "What is the mission?" For a given mission, one evaluates the options and then makes a choice, if possible. As batteries continue to improve (and the amount of research going on is like no other race I've ever witnessed), the options will improve.

With regard to cars, and your comment, we have another "huge, mature and well figured sorted infrastructure" (sic) to deliver electricity to the point of use with little geographic spacing. It's even more flexible and ubiquitous than gas stations.
 
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Speedboat100

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Assumptions again. So why isn't anyone doing it?

Dan I don't have a definite answer to that...I have now been working on it 13 years....and I think I am getting there. Dozens of innovations ( many unseen in aviation before ) that makes it possible...if ever. To make the airplane lite and durable enough for economical flight.

My 13 years old daughter is watching closely my aviation developements....and she will inherit my knowledge and methods...in the case I succeed she will continue the work (nephew is working at the Airbus). I have now 3 models so far and fourth is still needed to test before a bigger R/C plane. Luckily I now have a work space where I actually can build the plane too. I doubt it will fly next summer..but it is getting very close now.
 
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John.Roo

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With aspect ratio of 16 and L/D of 25 and wing loading of 25 kg/m2 I bet a 3-4 kw usage at 100 mph is doable too....so 3,5 hr endurance with 60 kg of batteries and 120 kg payload.
I agree that high aspect ratio of wing and high L/D helps a lot to achieve low energy consumption. But I am affraid that to fly at 100 mph (160 kmph) you will need more than 3-4 kW of power.
Idea of "glider like" plane is good. With low wing loading try to slow down to speeds arround 100 kpmh (60 mph). Think about higher drag of airplane at higher speeds.
60 kg batterie = 12-14 kWh. You need some energy for takeoff + try to keep at least 10% of energy in batteries after landing (longer battery life).

Weights....
60 kg battery
120 kg payload
10 kg motor
1,5-2 kg controller
And with some reserve for wiring etc. and weight is approaching to 200 kg.
80-100 kg airframe would be a very good result so you need MTOM somewhere near 280-300 kg.

Your requirement to low wing load will probably lead you to construction like AERO AC-21 or AL-12(M) (with increased MTOM). And with one modification - electric motor cannot bey installed on pylon. Too much drag during cruise flight.
1605087641003.png

However low wing load will also limit your cruise speed....
So... it is always about some compromise and realistic expectations :)

I would personaly not bet on endurance of 3-4 hours (unless you include soaring with engine off). But 60-90 minutes could be achieved.

Best regards!
Martin
 

Speedboat100

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I agree that high aspect ratio of wing and high L/D helps a lot to achieve low energy consumption. But I am affraid that to fly at 100 mph (160 kmph) you will need more than 3-4 kW of power.
Idea of "glider like" plane is good. With low wing loading try to slow down to speeds arround 100 kpmh (60 mph). Think about higher drag of airplane at higher speeds.
60 kg batterie = 12-14 kWh. You need some energy for takeoff + try to keep at least 10% of energy in batteries after landing (longer battery life).

Weights....
60 kg battery
120 kg payload
10 kg motor
1,5-2 kg controller
And with some reserve for wiring etc. and weight is approaching to 200 kg.
80-100 kg airframe would be a very good result so you need MTOM somewhere near 280-300 kg.

Your requirement to low wing load will probably lead you to construction like AERO AC-21 or AL-12(M) (with increased MTOM). And with one modification - electric motor cannot bey installed on pylon. Too much drag during cruise flight.
View attachment 103978

However low wing load will also limit your cruise speed....
So... it is always about some compromise and realistic expectations :)

I would personaly not bet on endurance of 3-4 hours (unless you include soaring with engine off). But 60-90 minutes could be achieved.

Best regards!
Martin

Hi Martin !


AEROS AC-21 is a good find...80 kg empty...I am aiming 62 kg empty. My craft has now 16 the aspect ratio ( Aeros 13.6 ), but wing span is just 12 m ( 39 ft ).

I can reveal that my AC has much shorter fuselage than Cri Cri or BD-5, but all checks out ok.

Also the elevator is flying and elevated like in Gen 3.

gen_3.jpg

If my daughter flew it it would have just 12.5 kg/m2 wing loading....with ½ hr batteries.

For the speed I have a clever flap system....which also provides 45 km/t stall speed to meet the Part 103 kinda landing features.
 
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henryk

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Sorry I don´t understand - what means "BKB1 free wing"?
Thxs.
Martin

=vortex flow possibility (Cy >3 at >30 deg. AoA ) ,
L/D=circa 20
(Vhor=10 m/s , Vvert=0.5 m/s !)

=STATIC stability & controlibility

L/D max=29


"free wing " = ASTER XII, XIII =AoA controll via control stic...
 

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blane.c

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Like many other pilots I am an instrument pilot (just think, it really can't be that hard) so what is the current state of the industry regards battery power to "on top" and solar power for sustain?
 

Jay Kempf

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You went from airplanes to ships to cars. Like other engineering projects, airplanes and watercraft require a question first: "What is the mission?" For a given mission, one evaluates the options and then makes a choice, if possible. As batteries continue to improve (and the amount of research going on is like no other race I've ever witnessed), the options will improve.

With regard to cars, and your comment, we have another "huge, mature and well figured sorted infrastructure" (sic) to deliver electricity to the point of use with little geographic spacing. It's even more flexible and ubiquitous than gas stations.
Yup, mission drives all. Cars, boats, airplanes all have to have a place to dock and refuel. Currently there is electricity everywhere sort of. But you can't charge a car in 5 minutes, while at your stop and get your coffee filled and have a pee and get right back on the road 24/7. There are charges showing up everywhere. I live in the middle of nowhere and there is one at the coop tiny hippie store at the bottom of my hill. There were a bunch of companies working on hydrogen filling stations. That didn't go either.

I really like my dinosaur juice. Been very, very good to me. Gets me where I want to go even the other side of the planet. We used to call that progress. Some people think technology of any kind is the devil. It's just perspective I guess.

And don't get me wrong that I am anti electric anything. I'm not. I have spent a lot of the last 5 or so years working pretty exclusively on engineering projects that are trying to further electric flight vehicles manned and unmanned. I don't speak from a lack of experience or exposure to the state of the art. I know exactly the state of the industry first hand, watt by bloody watt and oz by bloody oz of structural fraction and suffering through certification planning. The industry is moving forward with a huge number of Vtol projects some vaporware and others not but they are all bounded by the same two issues... 1 battery safety and charge times... 2 factors of safety driving structural fractions of composite structures and battery containment. And that is inching into the future one million investor dollars at a time. The real measure is how much is an investor willing to pay to get one more watt out of the same number of pounds and make it safe for a flight vehicle...? And the answer is probably going to be measured in millions of dollars per gram from what I can tell. Lots of people talking about revolutionary battery technology. Not much actually coming out of the lab for years now.

Going back to AR's original post, and the claims that SB100 has been trying to forward here: there will be certified airplane(s) soon. Pipistrel has a first aircraft. It has enough endurance for a basic training mission with a big turn around time. There are others coming that will have practical endurance but 100mph and endurance probably don't go together with current technology. So practical airplanes, what is your definition of practical? Mine is it replaces the current technology's practicality which is 500+ miles of range at speeds way over 100kts preferably closer to 200, 10 minute turn around and back out you go for another 500+ miles.
 

Speedboat100

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Like many other pilots I am an instrument pilot (just think, it really can't be that hard) so what is the current state of the industry regards battery power to "on top" and solar power for sustain?

There seems to be very few companies adding the solar power to sustain.....Electra One has solar option too.


In my opinion the solar panels are advancing faster than batteries are...I think the new bigger Tesla battery actually worsened the range ( 8 x heavier but gives 5 times more output )...but is possibly cheaper to manufacture and thus gives cost savings.
 

Dan Thomas

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Speculation and wishful thinking and uninformed prophecies never accomplished anything concrete. It takes hardware---real hardware---to do that. Models are fine but scaling them up involves some unpleasant facts, like doubling the size, which squares the wing area but cubes the weight, getting eight times heavier and doubles the wing loading. The average RC model has performance no real airplane will ever achieve.

I don't know about the US, but Canada has minimum HP and climb rate requirements for homebuilts. That's a result of too much blood spilled when underpowered airplanes stall trying to clear the fence or the trees. A low-powered motorglider is never going to meet those demands, and more blood will get spilled.
 

berridos

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Dana

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In my opinion the solar panels are advancing faster than batteries are.
No matter how efficient a solar cell is it still can never produce more power than the account of solar energy impinging on it. That's roughly 1kW per square meter at noon on the equator on a cloudless day, usually much less. A Cessna 172, for example, has a wing area of 16.2 sq m, so even with mythical 100% efficient solar cells the most you could get is 16.2 kW or about 22 HP... not nearly enough to be worth bothering with or to even keep it in the sky.
 

Speedboat100

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No matter how efficient a solar cell is it still can never produce more power than the account of solar energy impinging on it. That's roughly 1kW per square meter at noon on the equator on a cloudless day, usually much less. A Cessna 172, for example, has a wing area of 16.2 sq m, so even with mythical 100% efficient solar cells the most you could get is 16.2 kW or about 22 HP... not nearly enough to be worth bothering with or to even keep it in the sky.

Quite right, but Sunseeker 2 used only 2 kw to travel across the US continent.
 

henryk

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=printed Cu coils ! >96 % efficiancy...
 

Flyright

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Gliders are different story viable for short off the home field duration. It takes 10 minutes or so to fill gas. Are you willing to spend hours waiting for your batteries to be charged. OH over at the auto charging station I see guys in Tesla's sitting in their cars waiting for charge and of course the are looking at their iphone as it's being charged. (Less weight for battery, more duration, quick charge, then it may be viable for aircraft) BTW ... DOD attempted to build a nuclear powered aircraft in Arco NV. GE was involved. Never got off the ground.
 

Geraldc

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Models are fine but scaling them up involves some unpleasant facts, like doubling the size, which squares the wing area but cubes the weight, getting eight times heavier and doubles the wing loading. The average RC model has performance no real airplane will ever achieve.
We need to start breeding smaller people.
 

Vigilant1

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That is correct, but with newer 37% efficient panels would provide even in my new small plane concept 4 kw from panels alone and it is lighter than Sunseeker 2.
Your concept is much lighter than Sunseeker 2, having the advantage of not being made of matter.
For those playing at home, 4 kw = 5.4 hp. Less than that unless we wish away controller losses, motor inefficiencies, etc.
'So I need to fly in this uncoordinated bank all the time to keep the panels pointed at the sun?"
A 5hp aircraft can be very practical. It can carry two people...named Barbie and Ken.
 
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