Fun With: Flight Mechanics (and Gravity)

[rhoenix]

This is a continuation of my multi-species thread, to chase a particular idea and see how far it goes.

Concept: from the previous Fun With thread, in which low gravity-adapted people were examined. Now, we add the additional details.

We take the basic human form, and alter it to be quite bat-like - the arms are now much longer and have leathery skin-like wings behind them, the head is elongated and better adapted for flight, the bones are enhanced to have a natural hollow hexagonal honeycomb-like structure (to keep the weight lower without compromising much in the way of resilience), the legs are shortened and given prehensile toes, and other additions. The hands are still full articulated, complete with thumb, though they are directly attached to the wings, as bats' are.

This species of human has now adapted to a low-gravity environment (approx. 0.75 G), and has learned to excel in the area of flight, calling the air itself their home over the decades after they settled. They learned to eat, sleep, drink, and even mate while on the wing, and actually touch down only once in a great while. They are even capable of expressive artistry while in the air.

Scenario:
Let's see how this species fares on planets with higher gravity, shall we? For gravities of 1.0g, 1.5g, and 2.0g (in relation to Earth's gravity being 1.0g), here are the scenario questions:

1. On planets (and under conditions) with higher gravity than their homeworld, how much more would flying tire them out? Could they work up to achieving the same life-on-the-wing on planets with gravity relatively close to theirs?

2. Would they even be capable of the same flight mechanics under higher gravity (e.g. would they have to content themselves with simply gliding from place to place, given a high enough gravity)?

3. How might how they live affect how they live as a technologically advanced culture? Would they still continue long flights, or would invention be a necessity for staying put while tinkering?



Thank you in advance for your thoughts and replies.

[Batman]

Aren't most large birds on Earth ALREADY primarily gliders because while actually beating your wings for propulsion is technically doable, above a certain size it's too energy-intensive to do for any reasonable fraction of your flight time on any reasonable diet?

[rhoenix]

Aren't most large birds on Earth ALREADY primarily gliders because while actually beating your wings for propulsion is technically doable, above a certain size it's too energy-intensive to do for any reasonable fraction of your flight time on any reasonable diet?

My layman's understanding is that birds need the actual ability to fly to reach the warmer air currents, as well as maneuvering to land. However, once they've found a thermal, they can then glide within it, as you mentioned.

[Broomstick]

I think you may be making the same mistake many people do, thinking that gravity is the limiting factor in flight. It's not. Air density is a much more important factor. Enormously important. So much so that here on Earth, where gravity is a constant* that pilots have to recalculate runway take off and landing lengths with only about 300 meters difference in elevation because, yes, it starts to have a noticeable effects. Air, being a gas, also changes in density with temperature. Again, a mere 15 or 20 degrees or so (Fahrenheit - Celsius would be an even smaller interval) can require recalculation of runway distances because of the effect on air density. In the planes I fly required runway distance for winter time flying may be 1/3 of what is needed for summer on the same runway in the same airplane.

Increase air density and flying becomes easier. Decrease it and flying becomes harder. Yes, gravity also has an effect, but flying will be easier on a 1g world with higher air density than a less than 1g world with thin air.

Your next consideration needs to be wing loading. That is, how much weight is support by each unit area of wing while in flight. Higher wingloadings require more muscle power to fly, lower wing loadings require less but need a great supportive area. To my recollection, the Canada Goose has a wing loading of approximately 2lbs per square foot (sorry, yes, it's in English units). I tried to confirm this, and also to get a metric measurement, but my Google-fu and Wiki-fu is weak tonight. Maybe you could try Guinness, they might have the greatest wingloading for a flying bird on record. Anyhow. once you determine the wingloading and weight of your flying hominids that will give you an idea of the wing area you'll somehow need to contrive to enable flight.

About weight - you'll want to jettison as much as possible. This goes beyond hollow bones. Flying birds have largely dispensed with pairing organs with a spare. Flying birds have only one, or only one functional, kidney, gonad, etc. So toss one of every paired organ overboard. Most male birds don't have penises, either (waterfowl are one of the exceptions). Make these folks smaller than normal humans, too. Greater height/mass is not an advantage even for us fully human pilots (when I flew ultralights there were a couple summer days where weighing half of what the male pilots did enable me to fly whereas they literally couldn't get off the ground). Make your flying hominids 5 feet, or even 4 feet tall on average and they'll have it a lot easier.

Next consideration - are they going to have membrane wings, or feathered ones? After all, if you're engineering them you probably do have a choice here. It would seem, comparing bats to birds, that birds are capable of sustaining higher wing loads and that may have something to do with feathers, which are arguably the best solution nature has come up with for flying so far.

As far as these folks visiting other worlds - if the air is less dense than what they're designed for flying could well be a problem. However, supplementing their natural abilities with backpack mounted propellers might give them a sufficient power boost to enable flight. Normal humans have been known to use this technique to turn parachutes into flying machines: link to large image The total weight of such rigs is in the 50-75lb range. As our hypothetical flyers won't need the parachute, rigging, or as large a motor as a normal human any "boosters" should be of significantly less weight.

That should get you started on thinking about this. There are on-line sources of more specific information once you get into more nitty-gritty details. Let me know if you have additional questions and I'll see what I can do to answer them as this post is a pretty rough and broad overview of what could be a pretty complex subject. And I'm tired and not converting all the measurement units into the board standards of metric because if I tried right now I'd screw it up. It doesn't help most of my references are in English units and I'd have to go out and get the key numbers in metric before proceeding with more precise calculations.


* Actually, it's not quite - there are regional variations in the Earth's gravity that can be measured. But for our purposes they're so small we can ignore them.

[Broomstick]

Aren't most large birds on Earth ALREADY primarily gliders because while actually beating your wings for propulsion is technically doable, above a certain size it's too energy-intensive to do for any reasonable fraction of your flight time on any reasonable diet?

It's not just size, it's also how the wings are shaped. Seagulls, for instance, are gliding birds not because they're big and heavy but because that's what their wings are optimized to do. Albatrosses are not only big and heavy, they're shaped as gliders. Alabatrosses actually need runways, as they can't simply leap into the air ,they need to build up speed. You also see this in waterfowl, who typically have a take-off run on or just above the water to build up speed for flight. In that case, smaller ducks and geese will have "runways" not because they are big, but because of high wing loading.

There is, of course, an upper limit to how much power an animal can produce per unit of muscle, and this must be balanced with factors like weight and wing loading.

Condors are some of the largest flying birds and they certainly do favor launching from cliffs and utilizing thermals. They can take off from the ground, but it is a great effort for them to do so. Flying hominids might opt to climb up on something and launch from there.

[Batman]

Aren't most large birds on Earth ALREADY primarily gliders because while actually beating your wings for propulsion is technically doable, above a certain size it's too energy-intensive to do for any reasonable fraction of your flight time on any reasonable diet?

My layman's understanding is that birds need the actual ability to fly to reach the warmer air currents, as well as maneuvering to land. However, once they've found a thermal, they can then glide within it, as you mentioned.

Buddy I'm as much a layman about this as you are
My point (which I obviously didn't get across very well) was that while birds OBVIOUSLY are able to fly under their own power, SMALL birds can do this a lot better than BIG ones, with the big ones relying on gliding whenever they can.

[rhoenix]

Buddy I'm as much a layman about this as you are
My point (which I obviously didn't get across very well) was that while birds OBVIOUSLY are able to fly under their own power, SMALL birds can do this a lot better than BIG ones, with the big ones relying on gliding whenever they can.

That makes more sense; thank you for clarifying. I do appreciate your comments Batman, as they do usually help me to consider a concept from a different perspective, which I find valuable.

And Broomstick...never let it be mentioned that you are not awesome. That analysis you gave I'm going to be using as reference material until these people are much more complete, as its obvious I've more work to do for them, especially if they still have fully-articulated hands.

However, if I understood your post correctly, air density appears to be a far bigger enemy for flight than the local gravity. The caveat that they might need to climb and jump from a higher place sometimes is no barrier for them.

As of right now, a random idea I had in another thread is rapidly developing into another species in this universe, and one that will fill a much-needed niche in the story's ecosystem.

I am grateful to all who've participated, but don't let that stop you from replying further if you've an idea.

[Broomstick]

If I have time over the next couple days I'll see about getting you some information about air density calculations and stuff like that. I'm assuming you'll want it in metric, but if for some bizarre reason you want English units let me know.

This is an old thread on SD.net discussing a real-world airplane accident. Starting with the item posted Sun Dec 11, 2005 at 3:28 am there is a discussion of the effect of air density and how it's calculated in regards to the behavior of a B737. The same laws of physics also apply to birds, bats, bees, and all other flying things on the planet. Density altitude is in reference to a "standard atmosphere" and is basically "correcting" your present altitude to account for temperature and barometric pressure. The lower the density altitude the easier it is to fly (because the air is denser). The higher that number is the harder it is to fly.

[avatarxprime]

Your next consideration needs to be wing loading. That is, how much weight is support by each unit area of wing while in flight. Higher wingloadings require more muscle power to fly, lower wing loadings require less but need a great supportive area. To my recollection, the Canada Goose has a wing loading of approximately 2lbs per square foot (sorry, yes, it's in English units). I tried to confirm this, and also to get a metric measurement, but my Google-fu and Wiki-fu is weak tonight. Maybe you could try Guinness, they might have the greatest wingloading for a flying bird on record. Anyhow. once you determine the wingloading and weight of your flying hominids that will give you an idea of the wing area you'll somehow need to contrive to enable flight.

Here you go Broomstick, wing loading ratios for several bats and birds including the Canada Goose all in metric values. Funny enough in grams/cm^2 the Canada Goose is still at 2 (well 2.007 but who cares about 007 ). Man though, I had no idea that birds beat out bats so badly in terms of wing loading. So, rhoenix should certainly follow the avian body plan over the flying mammal.

[rhoenix]

So, rhoenix should certainly follow the avian body plan over the flying mammal.

Careful, I'm starting with the human body as a template. I have writer's fiat, not a magic wand.

With that said, feathered mammals wouldn't be impossible...but it would make hands very difficult, as no large animals have six limbs (wings included), which would rule the "angel/devil" type right out.

[avatarxprime]

So, rhoenix should certainly follow the avian body plan over the flying mammal.

Careful, I'm starting with the human body as a template. I have writer's fiat, not a magic wand.

With that said, feathered mammals wouldn't be impossible...but it would make hands very difficult, as no large animals have six limbs (wings included), which would rule the "angel/devil" type right out.

If I remember correctly when looking into the salamander's ability to regenerate (for human applications) they were able to get them to grow functional appendages in their backs in addition to repairing the original severed limb. You can take something like that as a basis to allow you to start engineering wings (or anything else for that matter) wherever you want.

[Razaekel]

So, rhoenix should certainly follow the avian body plan over the flying mammal.

Careful, I'm starting with the human body as a template. I have writer's fiat, not a magic wand.

With that said, feathered mammals wouldn't be impossible...but it would make hands very difficult, as no large animals have six limbs (wings included), which would rule the "angel/devil" type right out.

If I remember correctly when looking into the salamander's ability to regenerate (for human applications) they were able to get them to grow functional appendages in their backs in addition to repairing the original severed limb. You can take something like that as a basis to allow you to start engineering wings (or anything else for that matter) wherever you want.

The issue with this is that you need large muscles in order to flap the wings, for both bats and birds, and the best location for such muscles is the pectoral and ventral area, with the joint at the shoulder, which is why you don't see birds or bats with 6 limbs. If we're working from a human bodyplan, with the intent of keeping the standard arms and moving the wing attachment point to the back as depicted in artistic impressions of angels/demons, you'd have to either attach it to the scalpula or reshape it in order to reshape the dorsal section of the ribs. It's like fitting a square peg in a round hole, you'd have to do some major redesign of the skeletal anatomy to get something that would even be plausible. And that doesn't even account for the necessity of having solid attachment points for the muscles that would flap the wings. In this case, it's simpler to follow the model of bats where their fingers provide the support for the wing membranes. I suppose you could kitbash a bird and a bat, and modify the hand in order to provide both the extended digits and metacarpals of a bird, but have some normal sized fingers for manipulation. I wouldn't want to meet it in a dark alley, though.

[avatarxprime]

Careful, I'm starting with the human body as a template. I have writer's fiat, not a magic wand.

With that said, feathered mammals wouldn't be impossible...but it would make hands very difficult, as no large animals have six limbs (wings included), which would rule the "angel/devil" type right out.

If I remember correctly when looking into the salamander's ability to regenerate (for human applications) they were able to get them to grow functional appendages in their backs in addition to repairing the original severed limb. You can take something like that as a basis to allow you to start engineering wings (or anything else for that matter) wherever you want.

The issue with this is that you need large muscles in order to flap the wings, for both bats and birds, and the best location for such muscles is the pectoral and ventral area, with the joint at the shoulder, which is why you don't see birds or bats with 6 limbs. If we're working from a human bodyplan, with the intent of keeping the standard arms and moving the wing attachment point to the back as depicted in artistic impressions of angels/demons, you'd have to either attach it to the scalpula or reshape it in order to reshape the dorsal section of the ribs. It's like fitting a square peg in a round hole, you'd have to do some major redesign of the skeletal anatomy to get something that would even be plausible. And that doesn't even account for the necessity of having solid attachment points for the muscles that would flap the wings. In this case, it's simpler to follow the model of bats where their fingers provide the support for the wing membranes. I suppose you could kitbash a bird and a bat, and modify the hand in order to provide both the extended digits and metacarpals of a bird, but have some normal sized fingers for manipulation. I wouldn't want to meet it in a dark alley, though.

Considering the level of alterations that will be made/are being proposed to rhoenix's hypothetical genetically modified human to enable it to fly, the changes necessary to allow it to have both a set of wings and a set of arms is certainly on the "doable" spectrum. On the far end I admit, but doable nonetheless. It would probably be better to sacrifice arm strength by having those on the back or some other location while repurposing our current arm locations for wings. Another alternative is to still adapt arms into wings, but to then make the legs more like arms since this flying human spends most of its time in the air anyway.

[Broomstick]

The latter solution may be the more practical one. Keep in mind that birds (I have three specimens under close observation as they line up to beg for part of my breakfast here) have highly specialized "arms" for locomotion and use their legs/feet not only for standing and walking but also as we use our hands. In fact, parrots, with not just an opposable thumb but four opposable digits, are quite dexterous.

Birds are the champion fliers of our world. I think part of what gives them an edge over bats are those feathers they have - a feather, like hair, is a modifed scale and composed mostly of keratin. Once grown it needs no further biological input (just periodic replacement). Bat wings, on the other hand, are membranes that must be supported by a circulatory system and thus have an on-going biological cost. Also, bat wings are supported by very long and delicate bones whereas the meaty part of a bird wing is only part of the length of the wing (the remainder is flight feathers, the primaries) and likewise only a fraction of the width of the wing. This makes bird wing bones relatively stout and sturdy. This picture compares human, bat, and bird limbs. You can see that the bird and human limb are in some ways more similar than the bat limb structurally despite external differences:



You could probably engineer the wrist bones and fifth (and maybe fourth) digit of a human arm to function as a wing support leaving the remaining digits and thumb to function in a handlike manner. That would still leave the problem of the alula, which is what the bird "thumb" evolved into which is of aid in slow speed flight, often used on landing, and functions like the slats and slots on the wing of a big airplane. It is not essential to flight, bats and, as far as know, pterosaurs do not have them, but is yet another reason why birds are such skillful fliers. You might be able to modify a wrist bone to that purposes, as pandas have modified as wrist bone to function as a thumb, thus leaving the thumb to be just that. However, any hand attached to a wing will not be as dexterous as the base human hand. Is that a problem? Probably not, although you likely won't have any concert pianists among your flyers.

In keeping with evolution experimenting with just about everything, the hoatzin is a bird that, at least as a juvenile, bears two claws on each wing which are used for climbing trees until the wings and flight muscles are sufficiently strong to provide reliable flight. It was hard to find a good picture, but here we go:


Although not as useful as the base human hand, such wing digits might be sufficient to support the body in a hanging position, allowing the use of feet modified into hands to be used freely.

[Broomstick]

Here you go Broomstick, wing loading ratios for several bats and birds including the Canada Goose all in metric values. Funny enough in grams/cm^2 the Canada Goose is still at 2 (well 2.007 but who cares about 007 ). Man though, I had no idea that birds beat out bats so badly in terms of wing loading. So, rhoenix should certainly follow the avian body plan over the flying mammal.

Thank you, that was what I was looking for last night and couldn't find (I was pretty tired). As you can see, the Canada Goose is on the high end of wing loading, it's a pretty big bird, and yet they migrate long distances very successfully. Canada Geese have 10 times the wing loading of bats, essentially, and carry much greater mass/weight in the air. I don't think your flying hominids are likely to have a greater wing loading than a goose and still be powerful flyers. Even so, I'm not sure they're going to be able to spend quite as much time on the wing as you originally envisioned. Keeping that much body in the air is enormously costly on a biological level. Albatrosses and swifts both spend a LOT of time aloft, but with much lower wing loadings and, in the case of albatrosses, by using a highly structured method of flying that is the antithesis of cavorting freely across the sky. Add into that the metabolically costly human brain (I assume you want to keep that) and I just don't see sustained flight working 24/7. They can be strong fliers, but they're going to need to stop and rest. Keep in mind, too, that pregnancy would probably ground the women for a substantial time period. I think there would be too much weight gain and also their body profile would change, and probably not to something aerodynamically superior.