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I'm wanting to build a flying wing designed drone and I'm wondering if I were to fill the fuselage with helium if it would improve it's range.

Camille Goudeseune
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at0micV3n0m
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    Does this answer your question? Would hydrogen fuel tanks on an airplane increase lift? Buoyancy (a.k.a. static lift) depends on the volume of the object. If you put something else in the tanks, the buoyancy does not change. –  Apr 14 '21 at 01:13
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    Not really a dupe... using H2 as fuel (most of the discussion on the "dupe" question) is full of problems. Using helium to make your wing *lighter* than it would be if filled with the typical atmospheric mix of N2, O2, CO2, etc, as a separate set of considerations. – Ralph J Apr 14 '21 at 02:32
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    @RalphJ But the main point still stands: The weight saving is miniscule. So it is a dupe. – Peter Kämpf Apr 14 '21 at 05:52
  • However, the op is discussing the case of filling the (entire?) fuselage of a drone with helium, not the fuel tanks of a full size airplane. – CGCampbell Apr 14 '21 at 14:23
  • Thank you all very much for you're incredible feedback. @CGCampbell Yes, I'm wanting to create a flying wing drone for cargo delivery with the entire fuselage being filled with helium. I'm aware that nitrogen is lighter but I don't want it to become a mini Hindenburg if something should go wrong lol. – at0micV3n0m Apr 14 '21 at 16:10
  • So my idea was to create a flying wing design that incorporated a tiny compartment in the belly similar to the design seen in this vid: https://www.youtube.com/watch?v=fjjbeltn4Fo. The initial prototype of the drone would be of similar size to the one seen in the vid and would only carry a maximum of 45lbs. Since it's only a tiny compartment that would open and close for the cargo I though if I could fill the rest of the empty space in the body with helium perhaps I could extend it's range. If I should ever need to service it perhaps I could attach a valve to such the helium out and store it. – at0micV3n0m Apr 14 '21 at 16:13
  • So to be clear, the actual cargo bay would NOT contain helium but the rest of the empty space in the body of the drone would. If it's of any relevance I'm conducting further research to see if a battery/supercapacitor powered drone is feasible for approx. 50 mile range with a cargo weight of 40lbs. If not then I will look into some type of combustion. After initial testing the I had intended to scale it up to something that could carry a car or two. Perhaps I would consider filling the entire drone including the cargo bay with helium or maybe just everything else except the cargo bay. – at0micV3n0m Apr 14 '21 at 16:20
  • I'm not too concerned about the overall cost since I intend to create as many of the components/materials myself as possible including helium. I mean... the overall cost of the prototype can't be that of a Ferrari but I figured that if the performance increase was decent I could probably find a way to make it work at a reasonable price. – at0micV3n0m Apr 14 '21 at 16:30
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    Now I wonder why nobody has pointed out so far that a flying wing has no fuselage. There is nothing to be filled with hydrogen! – Peter Kämpf Apr 29 '21 at 16:46
  • Well, that's easy: put one on there! (with a low drag coefficient). – Robert DiGiovanni Apr 29 '21 at 21:32
  • You never specified that the aircraft was powered. If it is a glider and you are launching it from a mountain top into the face of strong headwind, you'd improve the range by filling it with lead. – quiet flyer Apr 29 '21 at 22:15

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If the end result of the sealed wing filled with helium is lighter than the same wing filled with a normal atmosphere (nitrogen, oxygen, and assorted other gases), then yes - a lighter aircraft will, all else being equal, have better performance and thus longer range than a heavier one.

If you'd actually be able to achieve economic benefit is doubtful - the delta in weight will be offset by everything required to seal the wing up, and the gain in efficiency may be pretty tiny. Beyond that, if mechanics need to access stuff inside the wing, you'll be paying to replenish the helium whenever that happens. Plus, the volume inside the flying wing is normally where things like fuel, passengers, crew, cargo, engines, and etc would go; you may find that you don't have all that much available space left to fill with helium.

Ralph J
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    Helium leaks very easily, so you'd be paying to replenish the helium on a regular basis. – jamesqf Apr 14 '21 at 03:48
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    The weight of the sealant needed will very quickly exceed any gains from displacing air with helium, especially at altitude when thinner air is replaced by sea level pressure helium. The end result will be a weight increase and a performance decrease. – Peter Kämpf Apr 14 '21 at 05:54
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This question is interesting as it delves into the efficiency cross over point between airships and aeroplanes.

From history we learn that airships had efficiency advantages up to around 80 knots, but were bulky and hard to control in poor weather.

A drone sounds like something that may fly at slower speeds, so why not cut loose a bit and think about a lifting body hybrid.

Slower flying speeds lend themselves to very thick heavily cambered wings, or lifting surfaces which could be inflatable.

In the end it is thrust/drag expense for lift + thrust drag expense for forward velocity. An airship drone may give you greater range.

Robert DiGiovanni
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To elaborate a bit on Robert DiGiovannis answer, yes certainly that would increase the range, if not for any other reason, than because it is quite easy to make it add considerably to the structural integrity of the drone.

Another thing you need to realize is, that saving weight and other range extending measures can come in a lot of small contributions, rather than one big one. So even if the volume is not all that big, as long as it contributes to the cause, its welcome.

Robert DiGiovanni
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