Just as an exercise in worldbuilding, imagine a world where genetic engineering (on subjects that already reached maturity, so no need to modify embryos and raise them to adulthood) creates supersoldiers with super strength who can exert themselves for days without the need to rest or sleep as long as they can replenish the calories and nutrients and hydrate themselves.

Would it make sense for an army to ditch the motors on their vehicles and only use man power? Imagine swapping the motorcycles for bicycles for example but also applying to cars, tanks, planes and boats.

In what circumstances would this be a preferrable option and on which ones would it not?

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    $\begingroup$ (1) Humans are inefficient engines. A common or garden variety diesel engine is about 40% efficient, that is, it is able to convert about 40% of the chemical energy in the fuel into mechanical power. A human working as an engine is about 20% efficient, that is, it is able to convert at best 20% of the chemical energy in the food into mechanical power. In other words, from the same amount of fuel or food, a diesel engine will be able to extract twice as much mechanical energy than a human working as an engine. (2) Humans are horribly heavy engines, with ridiculously low power-to-weight ratio. $\endgroup$
    – AlexP
    Feb 17 at 4:08
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    $\begingroup$ accepting the first answer you get after only 2 hours from posting is not the best way to get quality answers. Solved questions get less attention, and not all our users are online at the same time $\endgroup$
    – L.Dutch
    Feb 17 at 8:00

3 Answers 3


TL;DR: Yeah, but not completely. It is also inadvisable, unless budgetary or other extraneous factors play a part in decision making.

This would only create soldiers relatively immune to prolonged marches or prolonged operations and not able to replace some frankly inhuman military capabilities.

For an example: None of us can go supersonic naturally and the gearing needed to drive a ducted fan to push a plane to be supersonic would be insanely heavy because of the complexity and forces that a human driven supersonic engine drive train would require. For a more pedestrian aeronautic capability, the Merlin engine of the spitfire is roughly one thousand horsepower. A good cyclist could probably manage 1000W or about 1.35 horsepower. For your superhuman to manage a spitfire level of performance, they would need to be roughly 740x stronger than the normal human being (not to mention the caloric consumption that would entail)

That being said, it would open the opportunity for better infantry logistics when working in small groups, they can carry more resources and therefore fight for longer, not to mention that broken ability to not need sleep.

It could also open up some niche capability though, like bicycle powered transport gliders for short ranged hops between neighboring camps/bases. forward dirt airstrips could be used to resupply using those gliders especially when used like an air tow fashion like the soviets had done. (when some cargo planes might get a engine full of dirt trying to RTB, that is)

(the process would probably be that the mother plane would tow the gliders in a route that goes over multiple forward bases at once and unhook the individual gliders for them to land at their respective locations. Then once unloaded the glider would limp back to base or the logistics center they were at under the power of a couple of these super bros on a tandem bike to return the glider.)

Other forms of transport could be flatbed trikes, all terrain pedicabs for long endurance marches (one guy pulls four guys, rotate the guys every unit of distance, one guy could have a mounted machine gun lol).

On rail, this could be used in conjunction with slip coaches to add a margin of safety and insurance (if the slipped coach was going uphill or stopped early, the guy can pedal it into station) and many other light transport.

This will free up the military to focus on heavy equipment and not light trucks and whatnot; the only light vehicles would then be government official cars and various vehicles that has mounted on it some appliance that needed external power like SAM trucks, ICBM trucks, Radar trucks, Kitchen trucks (maybe), Long Range Communications cars, etc. Pure light transport trucks could be de-emphasized in favor of more heavy transport trucks as well.

Conceivably, this pedal power could also be used in the face of oil shortages due to blockade or prolonged war.

IIRC armies back in the day also experimented with bicycle corps to see if simply upgrading with cheap bikes could provide a big enough mobility and carrying capacity boost to infantry. It seemed it was born of a necessity to replace horses rather than motorcycles (horses were relatively harder to support, logistically). Though, sidecar bicycles are a thing -- out of which necessity is beyond me.

Keep in mind that this is if your country's economy is relatively poor, that is, if the economy could not purchase and support proper mechanized transport on such a scale that it might need to. It is much more efficient to let a specialty engineered part do the job than if a human were to waste energy doing one of many things that it could be doing otherwise. Its a waste of intelligence and quite the waste of energy for a human to perform transport under their own power.


There are 4 areas where Vehicles would still be preferable:


Regardless of how strong our super soldiers are - they aren't carrying more cargo than say a Truck, Cargo plane or ship. Even if we assume they can carry 500 Kilos of weight with ease, it's the bulkiness and volume of Cargo that means that they aren't as efficient as a dedicated Cargo transport.

And as we all know, amateurs study tactics, professionals study Logistics.


So, our super humans can run really fast, like 100 MPH or faster? Still way slower than a Jet Aircraft. Getting from point A to Point B in large distances will require Aircraft.

Armor and Firepower

So this is kinda a double up - but if we assume what a Tank brings - it's a combination of firepower (big gun) and protection. Sure, our Super soldiers might be able to carry body armor - but the physics is that even a super-soldier will not be able to face-tank a 120mm sabot round (not enough mass in the human, too much kinetic energy etc. etc.) and likewise, assuming our super soldier could lift several tonnes of cannon (again, physics and leverage is not our friend here) - the recoil would be uncontrollable (unless the Super soldier weighs several tonnes).


I think things might go the other way...

There is a height limit on Top Gun pilots. Tom Cruise is about right. It is easier to pick someone the right height than to modify the billion-dollar aircraft for tall people. There may be some advantage for being short when you are doing high-G manoeuvres, but I think it is not significant.

If you wanted to lift more or run further, use a motorised exoskeleton. This can be turned off, and consume no power. It can be replaced if it gets damaged. There are gadgets that can give you super-sight and super-hearing.

It might be worth modifying people for for improved stamina, or for the ability to go into hibernation until help comes if wounded or abandoned without resources. You have small, wiry people with lots of technical kit.

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    $\begingroup$ There is a height limit for military pilots, but it isn't Tom Cruise. He's in the bottom few percentiles of adult male height, and cockpits like the F/A-18 are designed to allow something like the middle 90% of adults to operate everything. College football linebacker Terry Maki flew the A-10, for instance. He was probably close to the upper limit, but far taller than Tom Cruise! $\endgroup$
    – Ralph J
    Feb 18 at 17:35
  • $\begingroup$ I would imagine that a sensible army with the aforementioned super-soldier technology would only insert super-soldiers where needed and the rest stay natty (unmodified). $\endgroup$
    – Harry Mu
    Feb 19 at 5:20
  • $\begingroup$ Okay, I did stretch a point with Tom Cruise. But having a Frazetta Conan body is probably not the bonus it would seem to be, even if it does make the book cover good. $\endgroup$ Feb 19 at 11:29

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