How can a humanoid creature achieve the lowest possible terminal velocity with its own body?
What kind of anatomy would decrease its terminal velocity?
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1$\begingroup$ How close to human is humanoid? I'd say some kind of webbed limbs, i.e. a flap of skin or something that joins their torso, their arms and legs, so they can hold out their arms and legs as a sort of parachute, or maybe a giant fold in their skin that extends out like an actual parachute, but is that still humanoid? $\endgroup$– komodospCommented May 14, 2018 at 8:59
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3$\begingroup$ Does the humanoid have to be human-sized? $\endgroup$– Comic Sans SeraphimCommented May 14, 2018 at 12:52
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$\begingroup$ Wear a parachute? Nobody ever mistaken a parachutist as an alien, nevermind a complete non-humanoid. $\endgroup$– NelsonCommented May 15, 2018 at 2:10
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5 Answers
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Spread out flat a.k.a. (apropriately enough) spreadeagle.
To decrease terminal velocity, you want to maximise drag, while minimising mass. So, lightweight/honeycombed bones, and flaps of skin like a flying squirrel
SCIENCE!
The formula for Terminal Velocity is $V=\sqrt{2mg/(ρAC)}$ - that is to say, the square-root of twice the Force due to gravity divided by the drag on the object.
Since $g$ is approximately constant (acceleration due to gravity varies with square of distance from centre of Earth, approximately 9.81m/s), as is $ρ$ (density of air, varies with altitude) and $C$ (drag coefficient) is a constant for a given shape, then to change Velocity you need to either increase $A$ (surface area - if this changes the shape, it can also increase/decrease $C$) or decrease $m$ (mass of object)
answered May 14, 2018 at 8:59
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4$\begingroup$ @theonlygusti, mass ONLY has NO effect in a vacuum, as proven by the Hammer and Feather dropping at the same rate experiment, however, when any type of atmosphere is in play, then the ratio of mass to drag is what counts, less mass = lower terminal velocity, more drag does the same, to get the lowest terminal velocity you'd need to lower mass and increase drag... a parachute normally helps too $\endgroup$ Commented May 14, 2018 at 10:01
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7$\begingroup$ My first thought was flying squirrels. $\endgroup$ Commented May 14, 2018 at 10:12
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5$\begingroup$ It's essentially a human with a built-in wingsuit. $\endgroup$– SkylerCommented May 14, 2018 at 14:01
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18$\begingroup$ @Skyler Indeed, some sort of flying-mammal-person. A "Bat-man", if you will $\endgroup$ Commented May 14, 2018 at 14:10
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3$\begingroup$ @Chronocidal You mean like Man-Bat! en.wikipedia.org/wiki/Man-Bat $\endgroup$– EthanCommented May 14, 2018 at 22:21
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In addition to the other answers: Make your humanoids small! The advantages of small size for falling are a universal principle of elementary physics, clearly and memorably explained by J.B.S. Haldane in On being the right size:
You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes. For the resistance presented to movement by the air is proportional to the surface of the moving object. Divide an animal’s length, breadth, and height each by ten; its weight is reduced to a thousandth, but its surface only to a hundredth. So the resistance to falling in the case of the small animal is relatively ten times greater than the driving force.
This can work either on its own (make them mouse-sized), or in combination with other features (make them cat-size, but with some kind of wings, maybe lower their planet’s gravity a little, thicken the atmosphere…).
answered May 14, 2018 at 15:15
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1$\begingroup$ +1 - there are insects so small that they can swim through air $\endgroup$– JeutnargCommented May 14, 2018 at 21:09
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3$\begingroup$ This is the Square-Cube Law: en.wikipedia.org/wiki/Square%E2%80%93cube_law $\endgroup$– glauxCommented May 15, 2018 at 8:04
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$\begingroup$ @Jeutnarg which ones? $\endgroup$– user9182Commented Sep 5, 2019 at 22:16
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1$\begingroup$ @theonlygusti can't find the article I read earlier (which listed many), but found one about fruit flies news.cornell.edu/stories/2011/05/… and also found that the science of aerobiology includes "some insects" $\endgroup$– JeutnargCommented Sep 5, 2019 at 22:46
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Terminal velocity results from the balance of 3 forces: (assuming motion is only happening in the vertical direction)
- gravity $F_g$ (pulling down)
- drag $F_d$ (pulling up)
- buoyancy $F_b$ (pulling up)
At terminal velocity $F_g = F_d + F_b$
If you want the terminal velocity to be as small as possible you have to increase the drag (flying squirrel-like) and also reduce density of the body with respect to the medium in which it is falling.
answered May 14, 2018 at 10:03
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Depending on how you define humanoid, you can just cover them in feathers. (Feathers appear to have originally evolved as a way to keep warm, flight was a much later addition.)
Even if you can't go that far, a thick pelt of fluffy hair similar to what some modern Africans have on their heads would provide quite a bit of drag.
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As other people have mentioned - size is an important factor. The less mass you have to worry about, the lower energy you hit the ground with.
Taking inspiration from nature - the wingsuit ala flying squirrel!
A while ago someone actually managed to make a wingsuit landing without a parachute - albeit into a giant pile of cardboard boxes that acted as padding.
