-2
$\begingroup$

I'm trying to design an aircraft with a long range, and I thought that an electric aircraft with a generator powered by the motor would be able to do that.

However, I've seen very few of these commercially not seen any aircraft that do this, and I was wondering why.

Is a fully electric aircraft too expensive/ not powerful enough to be feasible, economically or physically?

Also, is there possibly a way to generate enough power? An alternator/Magneto combination, perhaps?

Improve this question
$\endgroup$
8
  • 3
    $\begingroup$ What kind of aircraft are your asking about? We have a question about large electric aircraft feasibility, and for replacing jet engines. $\endgroup$
    – fooot
    Commented Sep 19, 2016 at 22:40
  • $\begingroup$ Your question is too broad. Electric aircraft exist at varying scales, but without a more focused question it's hard to say if it's "feasible". $\endgroup$
    – egid
    Commented Sep 20, 2016 at 1:21
  • $\begingroup$ I mean a fairly small aircraft. Not much larger than a Cessna. It would use an Electric Ducted Fan design, so it almost would be replacing a jet, but still using a prop. $\endgroup$
    – Nicholas
    Commented Sep 20, 2016 at 1:26
  • 2
    $\begingroup$ Until you understand simple things (e.g., you can't build a perpetual motion machine), you won't get very far with your attempt to do a complicated thing (design a long-range aircraft). $\endgroup$
    – David Richerby
    Commented Sep 20, 2016 at 13:19
  • 2
    $\begingroup$ Related: aviation.stackexchange.com/q/25933/4108 $\endgroup$
    – Sanchises
    Commented Sep 20, 2016 at 13:56

3 Answers 3

Reset to default
3
$\begingroup$

[Is] there possibly a way to generate enough power? An alternator/magneto combination, perhaps?

Not according to the law of conservation of energy.

Magnetos are for spark plugs in piston engines. If the airplane is fully electric, then you don't need magnetos.

As for the alternator, if the battery has 100 pirate-ninjas, and it spends 1 pirate-ninja to turn the propeller and turn the alternator every minute, the output of the alternator will be a tiny fraction of that pirate-ninja.

For electric propulsion topics here on SE, click here.

For the first question, click here.

For a list of modern light electric planes, click here.

Improve this answer
$\endgroup$
6
  • $\begingroup$ Thanks. What if I turned the magneto charge into DC via a diode bridge to go into the battery? Magnetos usually use 3- phase, correct? Could there be enough charge if the craft was wired that way? $\endgroup$
    – Nicholas
    Commented Sep 20, 2016 at 1:52
  • 3
    $\begingroup$ @Nicholas — You can't create free energy out of nothing, work has to be done, work consumes energy. The work used to turn whatever generator, it won't come back, only a fraction will. That's why we feed fuel to generators. $\endgroup$
    – user14897
    Commented Sep 20, 2016 at 1:54
  • $\begingroup$ Ok. It's probably more cost-effective just to use fuel. Thanks for the help. $\endgroup$
    – Nicholas
    Commented Sep 20, 2016 at 2:11
  • 5
    $\begingroup$ @Nicholas it's not that it's not cost effective it's that it's impossible. Read the links on conservation of energy and free energy / perpetual motion. $\endgroup$
    – Notts90
    Commented Sep 20, 2016 at 8:54
  • 1
    $\begingroup$ @ymb1 The reaction force from turning something in a magnetic field is not friction. Sure, you can't turn stuff for free in a magnetic field but the thing that stops you doing that is not friction. $\endgroup$
    – David Richerby
    Commented Sep 20, 2016 at 13:21
2
$\begingroup$

There is no such thing as free energy/perpetual motion so such a system is not possible. If you want a system to keep running you have to put energy into it.

As ymb1 pointed out, there's this thing called the conservation of energy and the laws of physics are pretty strict about it.

All systems lose energy as they perform work and that energy needs to be replaced from external resources.

It is possible to power a long range aircraft entirely from electricity

What you may be interested in is the solar impulse project which is an all electric (light) aircraft that is powered entirely by electric generated by solar panels on the wings.

It was the first solar-powered aircraft to make a round-the-world flight.

Improve this answer
$\endgroup$
1
$\begingroup$

In my 8th grade physics class long ago the instructor told us if we were to take a small toy motor and spin its shaft by some mechanism it will produce small electric current, which obviously is the other way around usually.

I asked him if i could take one motor and power it with a battery then couple that motor with another motor will that provide enough current after some time to then power the first motor without battery? He said try it in your next lab.

I sure did, and the results? As soon as I disconnected the battery the first motor always went off even though in my (erroneous ) theory the other motor which was spinning at the same speed should have been sending some current to keep the system working.

So no, if you cant really power such a tiny milliamps motor like that forget about a motor which will power a big propeller for sustained flight.

My R/C aircrafts drain amperes like anything and the quicker you want to recharge them the more power your charger requires and that certainly can not come from those motors themselves.

Yes you can design your aircraft to be able to self charge to increase its flight duration up-to a certain extent and a number of electric aircrafts do this already but that can be a little extension and not self sustained for any considerable duration. KERS does that, Ram Air turbines do that. Even gliders have dynamo to that effect but they don't provide as much power as would be required by your proposed idea

Improve this answer
$\endgroup$
3
  • 1
    $\begingroup$ You have a source of energy (the battery), you convert electrical energy into mechanical energy (first motor rotation), you transfer this mechanical energy to the second motor (dynamo) by coupling rotation axis. The mechanical energy of the second motor is converted back into electricity. But nothing is 100% efficient and there is an energy "loss" (actually heat generation) at each stage (conversion or transfer), so the final electrical energy is not sufficient to run the first motor at the same speed, so in a few seconds all levels of energy decrease to zero in a reaction loop. $\endgroup$
    – mins
    Commented Sep 20, 2016 at 8:45
  • $\begingroup$ And that's exactly my point - Such a system is not possible with current knowledge with reasonable number of resources $\endgroup$
    – Hanky Panky
    Commented Sep 20, 2016 at 8:47
  • 1
    $\begingroup$ Ah, sorry then. "When" there would be no loss, the physicians' Grail would have been found but this would create a big trouble. $\endgroup$
    – mins
    Commented Sep 20, 2016 at 8:55

Not the answer you're looking for? Browse other questions tagged .