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There are a few flying questions lately and this got me thinking. Someone suggested that a centaur might power a plane via a bicycle. I don't think this would work out, since the centaur would be very heavy compared to its power... but what about a small, light creature, with a lot of strength compared to its weight? What about a goblin?

If goblins used man-powered planes... how far could they go?

Characteristics of Goblins

In this case, I am presuming the following relevant characteristics:

Size

  1. They're small, of course. Let's say about 3.5 to 4 feet tall. This allows you to shrink various aspects of the plane, and should have an exponential improvement on its flight distance

Weight

  1. They're skinny and light, as is popular in most modern depictions. They probably weigh about 20 to 30 pounds, say 25 for simplicity. This reduction in weight should allow you to cut down on the weight of the craft, as well, which could have a significant impact on fuel-efficiency (in this case, goblin-power), and thus total flight distance.

Strength

  1. Compared to their weight, they are immensely strong. I'm not sure what figure to give, to best represent a strength to weight ratio... but as a general estimate, let's say that while they are about a 5th the mass of a 6-foot healthy man, they actually have 40% of the strength. In other words, they're about twice as strong per weight.

Endurance

  1. We'll also say that goblins have more endurance than a human. For simplicity, let's say they can endure twice as long, while putting out twice the power per weight, so theoretically 4x the total energy output per weight per day.

Craft

I expect the MIT Daedalus would be the best example to go off of. It has the current record of 115 km in a man-powered flight.

Multiple Goblins

You don't need to have just one goblin peddler. If the goblins are capable of producing more lift than their weight, then packing 3, 4, or even some ridiculous number like 12 could be considered?

It's possible the question of multiple goblins is too complex, as it gets into the complication of adding in new pilot seats, increasing structural strength, or even lengthening the plane in extreme cases. So, feel free to focus on the question of a single goblin. Extra credit to anyone who works out how multiple goblins can change the distance, of course. Or better yet, the optimal number of goblin-peddlers.

Assisted Takeoff

Assisted takeoffs, via taking off from a high point, or using a catapult, or whatever else, is allowed. This wasn't the case for the record flight of the Daedalus, where the takeoff had to be manpowered. I'm not sure how much of a difference this will make to distance, but I could imagine it adding on several km.

Question:

So, using humanoids with these sorts of characteristics... how far could a goblin powered plane go?

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    $\begingroup$ Depending on what you define as goblin-powered, you could also just have goblin-guided. Instead of a bicycling system, a goblin piloting an unpowered glider would work perfectly fine. The longest glider flight is about 3000 km, since it uses natural air thermals. But since it isn't technically powered kinetically by the goblin, I don't know if that counts as an answer $\endgroup$
    – Mandelbrot
    Jan 14 at 4:33
  • $\begingroup$ @Mandelbrot Makes me wonder about rocket-powered gliders. The only issue with the 3,000 km is that it sounds like they had a very prepared route for it, if they were using thermal updrafts. The 115km was under optimal conditions, using a win, but you could theoretically get similar distances from most places (or half the distance under subpar conditions). $\endgroup$
    – Johnny
    Jan 14 at 4:52
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    $\begingroup$ An answer to this is SO much more dependent on the materials technology available to the airplane manufacturer than the ability of the living "engines", that it becomes impossible to answer without more information about that. $\endgroup$
    – PcMan
    Jan 14 at 6:50
  • $\begingroup$ @PcMan I gave the Daedalus as an example for simplicity, so you can answer with present tech. Certainly, I'd be interested in an answer for any era. The early days of flight when bicycle planes were all the rage would be fitting. $\endgroup$
    – Johnny
    Jan 14 at 7:24
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    $\begingroup$ @Johnny the thing is, having more capable "engines" would not help Daedalus any. What ended its record breaking flight was not exhaustion of the pilot, but mechanical failure of the plane. Adding more power to the same structure would exacerbate this. So the question really becomes, "how do we redesign Daedalus to cope with stronger pilot(s)"? That is a very hard question to quantity. $\endgroup$
    – PcMan
    Jan 14 at 9:41
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Sailplanes are much, much more influenced by the form of their outer shell than be 20kg more or less payload. A 4 feet goblin would weight as much as many female pilots today... ok maybe even a little less.

The thing is that the plane itself, if it is lightweight and uses wings from today, will be able to carry a goblin or three or a man, it wouldn't make a difference. A sailplane is not powered by an engine, it is powered by thermics. Once it is in the air, and it can stay there for very very long.

The engines help arrive at the destination faster, though.

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  • $\begingroup$ With gliders powered by thermics, wouldn't that only be possible in certain climates, and with very specific flight paths? $\endgroup$
    – Johnny
    Jan 17 at 20:27
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    $\begingroup$ All climates, but only some weather conditions. I give you that. And of course some places are better than others. The height record was broken with considerable planning, in the Andes, at a specific place. But generally, it works everywhere. $\endgroup$
    – Anderas
    Jan 18 at 15:32
  • $\begingroup$ This sounds like it could make goblin-powered planes a lot more viable. Unless goblin or manpower would be pointless for such craft? $\endgroup$
    – Johnny
    Jan 18 at 21:13
  • $\begingroup$ Was hoping to get a more specific answer, but this at least offers an interesting alternative I can research. $\endgroup$
    – Johnny
    Jan 21 at 2:59
  • $\begingroup$ Yes, You're right. The distinction between Man- and Goblin pilot is not very important here. Though, there is one special case that might be interesting: If the Goblin has better power to weight ratio or more stamina or both, that might help a lot during the start phase or when something is going wrong with the thermics (too low to the ground and the airport is sitll far away? Pedal a bit) $\endgroup$
    – Anderas
    Jan 21 at 12:58
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Assuming mechanical perfection staying power is probably going to be more important than power-to-weight ratio; humans have incredible stamina, our ancestors used to run prey to death over many miles, sometimes continuing to hound horses and antelope over a period of days until they dropped dead from exhaustion. Goblins are usually depicted as having a high metabolism which requires constant feeding making feats of endurance unlikely.

A lighter, faster vehicle will offset some of the range disadvantages Goblins would have due to lower calorific endurance but quantifying that is awkward to say the least, and when you add the possibility of multi-crewing a vehicle that would only carry one human a final answer becomes impossible. This is especially true because we don't know how far a human flight could have gone in a mechanically perfect vehicle such as Daedalus since the flight was halted by material failure.

Goblin powered aircraft would certainly be more effective on short range runs than their human powered equivalents due to their improved power-to-weight characteristics.

Good question just too many variables left hanging unfortunately.

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  • $\begingroup$ If the Daedalus is considered a poor example, any other man-powered plane is fine to use as an example. It had reached near the length of its maximum intended route, IIRC. $\endgroup$
    – Johnny
    Jan 15 at 5:57
  • $\begingroup$ @Johnny The issue isn't that the Daedalus is a bad example per se, it's that it is the best example we have and it doesn't give us an answer to the question of just how far a human could possibly power such a vehicle because it broke, and/or the course was, short of the maximum distance a human might have been able to propel it. Without that benchmark we cant't really infer much about how other creatures would do by comparison. $\endgroup$
    – Ash
    Jan 17 at 11:35
  • $\begingroup$ That would make it a poor example. since it had reached its intended destination, I presumed that was a fine benchmark. If it's not considered a good example, than any other man-powered plane with a decent benchmark could be used for comparison. $\endgroup$
    – Johnny
    Jan 17 at 20:28
  • $\begingroup$ @Johnny For speed sure but there hasn't been a case that I'm aware of where a man powered aircraft has actually been flown to pilot exhaustion which is the benchmark I think would be important to working out the maximum range, you'd have to look for another endurance event where the participants were under a comparable mechanical load and see how far they got before they had to quit. $\endgroup$
    – Ash
    Jan 18 at 19:41
  • $\begingroup$ There are estimates for how many watts cyclists can put out. 5.5 watts per kilogram of bodyweight is what international pros can put out for an hour, so that's probably more than close enough for the human limit. $\endgroup$
    – Johnny
    Jan 18 at 21:12

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