# Boom of the Thunderbird

Could wings and feathers be capable of creating a sonic boom like whips do?

The thunder bird of native American myths was a large raptor that was often accompanied by bad weather and the sound of booming thunder. If this was a real flesh and blood avian, perhaps it was so large it used storm winds to help it stay aloft, and the booming sound was the flap of it's wings.

What size and length would wings need to be to produce this effect, and would there need to be any modification made to the wing tip feathers to endure the stress of a breaking the sound barrier.

• The problem lies not in the wing structure or the feather (even though both will undergo interesting stresses). The main problem is muscles strong enough to force a large wing through the transonic barrier. The power required is several magnitudes larger than mere flying would require. – PcMan Mar 13 at 18:21
• "so large it used storm winds to help it stay aloft" storms tend to be turbulent to the point where being large might hurt rather than help (more stress on the wings). Perhaps it instead surfs on the updrafts that form cumulus clouds that as the day progresses eventually become cumulonimbus. That way it presages storms, but can land before it's caught in them. – Kofthefens Mar 15 at 15:15

I'd suggest a slightly different approach with the same effect.

Tom Holland's scientific explanation of the origin of the myths surrounding the Thunderbird is that it arose with the discovery of a Pterosaur fossil. The ever popular Quetzalcoatlus Northropi with it's 50 foot (15.5 meter - estimates vary about maximum span), its weight being as much as 250Kg (450 lb) would make it heavier than a couple of average humans by a fair bit.

The sound of a Golden Eagle stooping, with its wings tucked in close to its body for streamlining - from over a mile-up, as it approaches the ground (some way from the camera and mike, sounds like a small fighter jet to me). The Q.Northroi could be lots louder.

Then the "Womp" sound made by its wings opening to decelerate. (soundtrack of a parachute opening). A big heavy bird like the Thunderbird of legend would likely reach a terminal velocity greater than that of a human by virtue of better aerodynamics - and more quickly, and a very impressive "Womp". Several of them playing in the clouds and making jet noises, simultaneous "Womps" then climbing to do it again out of sheer exuberance, might fit the bill.

If I might say, adding L.Dutch's idea and mine - the crack of a whip in the mix might fill all the appropriate gaps in the needed soundtrack.

Crack-crack-crack-CRACK-crack, Sheeeeeeuoch, WwWWwwoomP.

• For a moment there I thought the Hoñland in questkon was Spiderman. – The Square-Cube Law Mar 14 at 0:25
• @TheSquare-CubeLaw "With great internet searches comes great mistakes". RIP Stan. – A Rogue Ant. Mar 14 at 0:29
• Typo: "Golden Eagle stooping". I suspect you meant "swooping"? – RBarryYoung Mar 14 at 17:20
• @RBarryYoung Close in sound similar in meaning, - "Stoop: Noun, 1)A posture in which the head and shoulders are bent forward, 2)the downward swoop of a bird of prey.".I collected the word a few years ago from the title of a show: "She Stoops to Conquer". Probably not a very common word. – A Rogue Ant. Mar 14 at 17:32
• @Rottweileronmarket-day.I am familiar with both stoops (noun) and stooping (verb), though I have never heard it used to describe swooping. – RBarryYoung Mar 14 at 18:03

According to some paleontologists, Apatosaurus could produce a sonic boom with its tail

When an Apatosaurus dinosaur slapped its impressively long tail onto the ground, other beasts likely listened. Turns out, the long-necked dino may have broken the sound barrier with its tail whips more than 150 million years ago.

Paleontologists have all but gone back in time to prove the sonic booms, by creating and test-slapping a model tail made of aluminum, stainless steel, neoprene and Teflon.

The 12-foot-long (3.6 meters) model is just one-quarter the size of a sauropod tail, but it's still able to produce the distinctive crack that indicates it can break the sound barrier when whipped around, said Nathan Myhrvold, founder and CEO of Intellectual Ventures, a company that invests in technology patents and research.

From the above you see that the tail was long about 14 meters to produce a sonic boom at its tip. That's the ballpark figure you have to look at. Probably even longer, because wings are not whipped around like a tail.

For reference, the wingspan of the WW2 Spitfire was about 13 meters, so you are talking about something covering at least two Spitfires with its open wings.

## I don't think it works like that.

Let's begin with what everybody knows, or should know, in order to approach the Bridge of Death, namely, that an Old World swallow needs to beat its wings 43 times each second. Well, OK, to reach the other side you should know it is actually about 7 times each second. I have this on the redoubtable authority of the Stream of Consciousness Blog, but they did give a source, leading to Pennycuck, 1996, which says in no uncertain terms that the wing beat of ANY bird can be calculated according to the very simple formula,

$$f=m^{\frac{3}{8}}g^{\frac{1}{2}}b^{\frac{-23}{24}}S^{\frac{-1}{3}}\rho^{\frac{-3}{8}}$$

Fortunately, they modified the original and took the moment of inertia out of that, which isn't known for most birds, or it would be much more complicated.

Now what we can take from this is while we could alter the gravity or the air density, it wouldn't look good, and we could alter the wing length, but with virtually no effect (we multiply it by the frequency and get a 1/24th root of something), which means, either we can make the wing area smaller so it buzzes more like a hummingbird, or we make the bird heavier so that it must somehow learn to fly faster. This last seems in accordance with your preferences. Despite this, the frequency would reduce with mass unless the moment of inertia goes down, so the wings are going to have to be rather strange looking in order to improve the rate of flapping by a large factor.

Because the effect of such a whip-cracking would be more like a motorcycle than a thunderstorm, I would humbly suggest that perhaps you give a little more credit to the legend. The bird simply has conductive barbules:

When it desires, it sends a small portion of each of its wings an endocrine signal that causes each feather to emit a hydrophobic compound in its oil, which detaches the barbules. Unlike the photo shown above, however, these barbules are designed to interlace at the start and end along each barb of each feather. A single feather unspools into dozens of meters of highly conductive thread, and the beat pattern of the wing twists this into a continuous fiber with other such threads.

The result is comparable to Georg Wilhelm Richmann's famous kite experiment, where he flew a kite in a thunderstorm and was killed by ball lightning jumping from the silken string, having less good fortune than Franklin. You may also compare the common lightning rocket - though one of those is the size of a man, that is because it is trying to boost up into the storm from below rather than dropping its strand from above.

Is the Thunderbird simply hungry for cooked meat, or is it a mysterious judge of character that makes decisions like a drone operator who might single out a disfavored foreign diplomat for a similar accident? I don't know - it would be best to go back to the native Americans and ask for more data.

Wings and feathers are not the only choice.
A whip that can be "cracked" is 'easy enough' to fabricate and the motion required to get the tip to achieve supersonic velocity requires a far slower hand & arm velocity accompanied by an appropriate wrist action which accelerates the tip to 50 to 100 times the hand velocity.

I at one stage owned a homemade whip about two meters long that could be "cracked" although not overly well (and often painfully by those with inadequate experience. :-):-(.

A suitably designed or evolved bird could easily have an appendage that could achieve supersonic velocities if appropriately manipulated. Rate of cracking could be independent of flap rate.

The biggest issue to overcome would probably be the provision of a sacrificial cracking-end as these experience extreme mechanical stress - many whips have a replaceable short leather end thong for this reason. This could perhaps be grown but an alternative would be the ability for the Thunder bird to add sacrificial material in some manne.

• " Wings and feathers are not the only choice. " Indeed, the sound could come from a beak or tail. If someone can crack a leather whip then that proves mundane organic material can make a thunderclap like sound with minimal damage. If it's a matter of scale then that's a different question. If it's a crack of a whip that you want then a tail of bare skin, or thin covering of hair or feathers, can likely be a suitable body structure. If the idea is a bird that can make a sound exactly like that of a thunderclap then you are talking of a bird so large and powerful it is unlikely to fly. – MacGuffin Mar 15 at 10:39