[Spaceships] Ornithopter Wings no longer TL5+2!

[Anthony]

Originally Posted by Refplace

Wings also add a lot of weight and need to handle a lot of stress. This is easier for smaller objects then larger ones.

Every flying machine has wings. The power requirements for an ornithopter are very similar to the power requirements for a helicopter, it's just that you need artificial super-muscles to build a large one.

[spacemonkey]

Originally Posted by Anthony

Every flying machine has wings. The power requirements for an ornithopter are very similar to the power requirements for a helicopter, it's just that you need artificial super-muscles to build a large one.

I'd say the power requirements are much lower unless hovering, propellers alone aren't the greatest at turning energy into both thrust and lift. A fixed wing aircraft will beat a helicopter, and an ornithopter gains some of the benefits of a fixed wing aircraft when compared to a helicopter. That doesn't mean ornithopters could potentially compete with helicopters. For that, we would need to make massive advances in materials, engines, and aircraft design that somehow only apply to ornithopters.

[Refplace]

Originally Posted by Anthony

Every flying machine has wings. The power requirements for an ornithopter are very similar to the power requirements for a helicopter, it's just that you need artificial super-muscles to build a large one.

Wings able to use this kind of lift though need to be stronger and handle a different kind of and increased stress over normal lifting wings on a plane.
and the stronger you make them the heavier they are which means more work for the actuators.

[Anthony]

To give an example of why we don't see large fliers, let's look at the performance requirements on a real fairly small plane: a Cessna 172. It has a weight of 2,450 lb and a fueled (empty) weight of 2,028 lb, making it somewhat more massive than a draft horse; figure an animal in that weight range could manage somewhere on the order of 1.2 horsepower.

The Cessna's cruising power requirement is 88 horsepower and its max is 160. Doing some aerodynamics calculations (1,110 kg, 11m wingspan, 16.2 m^2 wing area, 0.027 Cd, cruising at 63m/s at a nominal altitude of 12,000' (using a standard atmosphere, air density 0.85 m^2) it requires at least 59 kW power, or 61 kW power using stream tube analysis as if it were a helicopter. Thus, we're pretty close to the efficiency limits.

Now, on average the wings are supporting 11,000N weight, meaning each one supports half that; however, what we actually care about is torque, meaning we multiply by the distance from the wing attachment point to the support point. For wings with low taper, this averages to slightly under half the wing length, and thus something like 14,000N*m per wing. Mammalian skeletal muscle has a maximum contraction of about 20%, and we can't really have an attachment point for the main muscle that's more than around half way out the wing, so for wings that can be folded with muscle and can flex somewhat above straight, that's an attachment point not more than about 0.4m below the main wing body, meaning we need 35,000N muscle per wing. That's about 0.1m^2, and the attachment point can be a meter long, so it's only about 0.1m^2 thickness, which isn't too bad. However, that's a total of 0.25m^3 of muscle per wing, and at typical muscle density would amount to 530 kg of muscle. With a reasonable margin (at least 2) of extra power for turning and flapping, that's 1,060 kg of muscle, or basically the entire craft mass. That's really not practical. Moving the attachment point up or down the body doesn't really matter, you wind up moving the attachment point on the wing as well, and you get a shorter but thicker muscle with the same overall weight.

For comparison, the standard engine in the Cessna produces a peak of 160 horsepower and weighs 117 kg. Thus, for a competitive ornithopter, ignoring all the problems associated with controlling flapping wings, we want somewhere around 130x the power output of an animal of similar size, and muscles that are about 9x stronger, weight for weight. You probably also want similar increases in bone strength.

Incidentally, if you assume the existence of such modified muscles, and put them on a large flying creature such as a dragon, you wind up with rather scarily fast creatures. If you take a human arm and double all of its dimensions, it winds up being 4x stronger (ST 20) and 8x more massive, it reaches the same total velocity on a swing and requires 2x as long, and thus has 4x the average power output. If we then multiply muscle strength by 9, the result is 36x stronger (ST 60), it reaches 3x the velocity on a swing and thus takes 2/3 as long as a human would, and produces 108x the power. In practice a flier would tend to work on minimizing its landing gear weight, and thus the front legs might be weaker than that, but also lighter, so it would remain extremely fast.

[AOTA]

These would make awesome spy drones just make them a bit more realistic and load them up with a spy suite and bingo spy drones that would be able to go anywhere.

[Bruno]

Originally Posted by spacemonkey

I'd say the power requirements are much lower unless hovering, propellers alone aren't the greatest at turning energy into both thrust and lift.

We're not comparing them to "propellers", we're comparing them to TL 8 and 9 aircraft - which include propellers, yes, but also turboprops, jet engines, ducted fans, and helicopter blades (which aren't "propellers").

Actual real flying animals, as they get/got up into human weight ranges (100+ lbs) become less and less "flyers" and more and more "gliders that can do some flapping in emergencies". This is pretty evident in how disproportionately large the wings become - the larger and longer they are, the harder they are to flap, and the better they are for gliding over flapping. IE, the creature more and more approximates a fixed-wing ultralight glider.

Quetzalcoatlus has been eyeballed somewhere in the 150 to 550 lbs range (not enough skeleton has been found to make a more firm guess) with a ~30-36 foot wingspan. It looks like a hang glider with a (giant) heron's neck and head hanging off of it. It also has a body plan unusually well designed for quadrupedal motion, unlike other pterosaurs - this is a giant winged animal that did a lot of running around, which suggests it was often more effective for it to just walk somewhere than to try to fly.

[roguebfl]

Originally Posted by Bruno

Actual real flying animals, as they get/got up into human weight ranges (100+ lbs) become less and less "flyers" and more and more "gliders that can do some flapping in emergencies". This is pretty evident in how disproportionately large the wings become - the larger and longer they are, the harder they are to flap, and the better they are for gliding over flapping. IE, the creature more and more approximates a fixed-wing ultralight glider.

Um you missing trends in large flyers like the Haast Eagles who wings while large are notable shorter than if that trend was strictly true.

[vierasmarius]

Originally Posted by roguebfl

Um you missing trends in large flyers like the Haast Eagles who wings while large are notable shorter than if that trend was strictly true.

They didn't get to be much more than 30 pounds, and were a pretty specialized critter anyways (hence going extinct shortly after their primary prey was wiped out by humans). They're certainly no challenge to the trend that Bruno is talking about. Large birds tend to be gliders rather than flappers. IIRC, the same seems to have been true of some of the truly massive Pterosaurs.

[Cheomesh]

Originally Posted by Anthony

To give an example of why we don't see large fliers, let's look at the performance requirements on a real fairly small plane: a Cessna 172. It has a weight of 2,450 lb and a fueled (empty) weight of 2,028 lb, making it somewhat more massive than a draft horse; figure an animal in that weight range could manage somewhere on the order of 1.2 horsepower.

The Cessna's cruising power requirement is 88 horsepower and its max is 160. Doing some aerodynamics calculations (1,110 kg, 11m wingspan, 16.2 m^2 wing area, 0.027 Cd, cruising at 63m/s at a nominal altitude of 12,000' (using a standard atmosphere, air density 0.85 m^2) it requires at least 59 kW power, or 61 kW power using stream tube analysis as if it were a helicopter. Thus, we're pretty close to the efficiency limits.

Now, on average the wings are supporting 11,000N weight, meaning each one supports half that; however, what we actually care about is torque, meaning we multiply by the distance from the wing attachment point to the support point. For wings with low taper, this averages to slightly under half the wing length, and thus something like 14,000N*m per wing. Mammalian skeletal muscle has a maximum contraction of about 20%, and we can't really have an attachment point for the main muscle that's more than around half way out the wing, so for wings that can be folded with muscle and can flex somewhat above straight, that's an attachment point not more than about 0.4m below the main wing body, meaning we need 35,000N muscle per wing. That's about 0.1m^2, and the attachment point can be a meter long, so it's only about 0.1m^2 thickness, which isn't too bad. However, that's a total of 0.25m^3 of muscle per wing, and at typical muscle density would amount to 530 kg of muscle. With a reasonable margin (at least 2) of extra power for turning and flapping, that's 1,060 kg of muscle, or basically the entire craft mass. That's really not practical. Moving the attachment point up or down the body doesn't really matter, you wind up moving the attachment point on the wing as well, and you get a shorter but thicker muscle with the same overall weight.

For comparison, the standard engine in the Cessna produces a peak of 160 horsepower and weighs 117 kg. Thus, for a competitive ornithopter, ignoring all the problems associated with controlling flapping wings, we want somewhere around 130x the power output of an animal of similar size, and muscles that are about 9x stronger, weight for weight. You probably also want similar increases in bone strength.

Incidentally, if you assume the existence of such modified muscles, and put them on a large flying creature such as a dragon, you wind up with rather scarily fast creatures. If you take a human arm and double all of its dimensions, it winds up being 4x stronger (ST 20) and 8x more massive, it reaches the same total velocity on a swing and requires 2x as long, and thus has 4x the average power output. If we then multiply muscle strength by 9, the result is 36x stronger (ST 60), it reaches 3x the velocity on a swing and thus takes 2/3 as long as a human would, and produces 108x the power. In practice a flier would tend to work on minimizing its landing gear weight, and thus the front legs might be weaker than that, but also lighter, so it would remain extremely fast.

I have to know - how do you figure this?

I feel vastly uneducated.

M.

[sir_pudding]

Originally Posted by Anthony

Every flying machine has wings.

Not counting those that use directed thrust or ground effects.