Story is set in our days, modern Earth with all it's current problems and conflicts. Let's say someone had secretly found a way to produce almost infinite (reasonably infinite, of course) amount of energy in form of electricity, it's easily scale-able in power, it takes size just about standard suitcase and weight is small enough to be carried by just one man. For a "field experiment" it's used as a power source for an actual battlefield helicopter, similar to something like MH-53 in characteristics (in terms of size, weight and capability to use on a difficult terrains to land and take off).

It's usage pretty crucial for story, as this helicopter is used as a transport for hundreds and thousands of kilometres, with range restriction only in matters of pilot endurance.

My question: is there any way to transform electric current into rotation of blades, and other outputs, needed to operate a helicopter properly? I mean, there are a lot of electric engines with enough horsepower to lift a helicopter, but they weight and are measured about as big as a helicopter itself.

Re-clarification of question: currently available electric engines, if replacing original engines ot that helicopter, will be size of a helicopter itself and weight >6 more times than original one. Do I just don't know about more reasonable e-engine solution, or there is just no any?

Sorry for any errors or misspells, English is not my native language.

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    $\begingroup$ Traditionally questions only containing one question are less likely to be closed and more likely to get good answers. $\endgroup$ – Ash Jul 19 at 16:54
  • $\begingroup$ Removing not so crucial subquestion here: if information about such an extravagant device will slip to some powerful enough country, will it provoke worldwide hunt for that helicopter? With use of autopilot he can virtually be 100% airborne. But can it possibly gain so much interest in some military-scientific circles like DARPA, so they decide to use military power (with worldwide attention) to bring it down and experiment on it by themselves, and it will be ok, or it will be counted so aggressive, so all the other countries will be really, really angry? $\endgroup$ – Lemis Jul 19 at 16:57
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    $\begingroup$ This was a TV show in the 80s: en.wikipedia.org/wiki/Airwolf $\endgroup$ – Morris The Cat Jul 19 at 17:37
  • $\begingroup$ You can not just power a helicopter with it, you can mount a railgun on your helicopter. $\endgroup$ – Alexander Jul 19 at 17:40
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    $\begingroup$ The phrase "countably infinite" has a well-defined meaning. That meaning is incompatible with the usage of the phrase in the question. And your impressions about electric motors are simply wrong. $\endgroup$ – AlexP Jul 19 at 18:10

So you have a small, man-portable device capable of providing electrical power in any quantity desired. Daniel Thomas Shipstone would be proud!

Brushless electrical motors are commonly used to provide lift and momentum in airborne drones which operate very similarly to helicopters. The great challenge in creating a load-bearing drone is not the weight of the engines, but instead the weight of the batteries needed to power the engines for long-distance flight. If you ignore the weight of their fuel/power sources, electrical engines have demonstrated higher power to weight ratios than conventional fuel engines. Since you invention effectively solves the power-source weight problem, there are no obvious technical reasons that you can't create a war-worthy electric helicopter.

  • $\begingroup$ Last time I've checked, helicopters like this used two combustion engines 4k-4.5k horsepowers each, and just one electric engine with that much power was half size of a helicopter itself. If someone want to fit two of those engines in helicopter - he will need a slightly bigger helicopter :) $\endgroup$ – Lemis Jul 19 at 17:39
  • $\begingroup$ I just found a similar question on an associated forum. A lot of the answers support your assertion that size and weight are still the issue. Seems that the advantage in power-to-weight that electric holds over combustion in the small scale, inverts at height power levels. Thanks for helping me learn something new. $\endgroup$ – Henry Taylor Jul 19 at 18:27
  • $\begingroup$ you right, all of the answers on this question is about "yes, just use e-engine", even if I stated in the question itself, that problem isn't about "should I use electric engines?", but about "they are too big to use, what is the way to avoid using USS Enterprise with rotor blades on top of it?" :) From your link I can see that e-engines provide about 1 kW/kg, so just to replace 1 ton and 6 MW of original engines of MH-53 I need six tons of electric engines (and it's without any mechanics around involved)... $\endgroup$ – Lemis Jul 19 at 18:36
  • $\begingroup$ Thumbs up for the Shipstone reference. $\endgroup$ – puppetsock Jul 19 at 19:01
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    $\begingroup$ Modern electric motors such as those used for electric automobiles provide better than 10 kW/kg, so using your crude calculation those 6 MW would need about 600 kg of engine. $\endgroup$ – AlexP Jul 19 at 20:41

You have functionally unlimited amounts of electricity? Just use electric-powered jet engines. Jet engines have four stages, only one of which, the combustion chamber, is chemically-powered, and the burning jet fuel is primarily used simply to increase the temperature of the air in the combustion chamber. With unlimited electricity, you can simply use something like a tesla coil to generate high-temperature plasma in what was the combustion chamber to do the job of heating the air instead of fuel.

  • $\begingroup$ Pretty neat solution, but doesn't jet engines used for planes and overall plane-like motion? Helicopters don't need a runway to land, they can hover and can be used for troop landing, and planes are not. Of course, if it's not something like convertiplane from Terminator. $\endgroup$ – Lemis Jul 19 at 19:22
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    $\begingroup$ A lot of helicopters use jet engines, too; they're called turboshaft engines. They just use them to spin the helicopter rotors rather than providing thrust directly or spinning turbofans like most big passenger planes do. $\endgroup$ – nick012000 Jul 20 at 8:26
  • $\begingroup$ With unlimited power why spin rotors? Build an electric Harrier Jumpjet. $\endgroup$ – Joe Bloggs Jul 21 at 8:13

As of 2018 the most efficient internal combustion engine converts just 44% of the potential fuel energy entering the engine into rotation. Air cooled electric motors using compressed air bearings can produce 95% efficiency with only 5% lost as waste heat, (that's not quite a true comparison as you get some loses to wiring resistance etc... before that energy gets to the engine) you might need a bigger helicopter but with infinite energy to pump into a 95% efficient engine system you should get it off the ground at some point where the economy of scale favours you.

  • $\begingroup$ Well, if I need a bigger helicopter to fit those engines - it will incrementally add to weight, so I will need an even more powerful engines (to lift a bigger helicopter and themselves). Even if it will not lead to N1-like project, it will make using it on battlefield remarkably harder, as size will increase and speed will decline. KSP-like "just add more boosters" is logical, but in the same time is somewhat wrong. $\endgroup$ – Lemis Jul 19 at 17:47
  • $\begingroup$ @Lemis Like I said there will be somewhere along the line that the economy of scale works, probably. $\endgroup$ – Ash Jul 19 at 17:52
  • $\begingroup$ for now I'm just using words like "super-efficient rotor", allowing to not draw much attention of anyone in novel world (but really large, silent not-fueling helicopter will draw it), but it looks too StarTrek-ish. I might just toss there "extraconductive zero-spinary unequal tetrastable torsionic engine" and it wouldn't look less realistic. Helicopter is large part of the story, so I can't just let it be, because 99% of other stuff is much more real-looking, power source is really only one not really beliavable stuff. And without proper explanation I can as well say "it's just magic"( $\endgroup$ – Lemis Jul 19 at 18:00

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