[Spaceships] Ornithopter Wings no longer TL5+2!

[vierasmarius]

Originally Posted by vicky_molokh

Speaking of wings, by RAW they have a speed limit of 500mph. How realistic is it? Optimistic? Pessimistic?

It don't know about optimistic or pessimistic, but it feels a little arbitrary. Note that a streamlined craft with 0.25G accel normally has an airspeed of 1250, so the only craft that will be slower than the ornithopter's 500mph limit are those that are unstreamlined. Even giving them Small-sized drivetrains (1/3 thrust, or 0.083G) drops the potential airspeed of a streamlined craft to 720mph, which is still over their limit.

I'd actually prefer if Ornithopters were treated more like Helicopters, providing a top speed per motive system (varying with streamlining, of course). That would help differentiate between more and less powerful Ornithopters.

[vicky_molokh]

A quick Google search brings up some pages claiming that ornithopters don't have a theoretical top speed. Again, no idea how well-researched that is.

[spacemonkey]

Originally Posted by vicky_molokh

A quick Google search brings up some pages claiming that ornithopters don't have a theoretical top speed. Again, no idea how well-researched that is.

Sweet, ftl ornithopters!

[vicky_molokh]

Originally Posted by spacemonkey

Sweet, ftl ornithopters!

I think they didn't mean it that way.

[vierasmarius]

Originally Posted by vicky_molokh

I think they didn't mean it that way.

Nah, all it takes is an infinitely strong chasis (so it doesn't disintegrate from friction), an infinitely large air-filled space, a power souce that never exhausts itself, and an infinite amount of time. Easy!

[Anthony]

Originally Posted by vicky_molokh

Speaking of wings, by RAW they have a speed limit of 500mph. How realistic is it? Optimistic? Pessimistic?

It normally causes difficulty for aircraft when parts of the wing approach or break the sound barrier; it's actually better to be significantly supersonic than to be transsonic. Winged flight does involve parts of the wing moving faster than the forward velocity of the plane, though I don't think it's that much faster; still, a general speed limit of 600 mph (typical for subsonic airframes) probably implies a winged flight limit of near 500 mph. However, it's not obvious that you can't make a transsonic or supersonic ornithopter wing.

[Lord Carnifex]

Originally Posted by Anthony

It normally causes difficulty for aircraft when parts of the wing approach or break the sound barrier; it's actually better to be significantly supersonic than to be transsonic. Winged flight does involve parts of the wing moving faster than the forward velocity of the plane, though I don't think it's that much faster; still, a general speed limit of 600 mph (typical for subsonic airframes) probably implies a winged flight limit of near 500 mph. However, it's not obvious that you can't make a transsonic or supersonic ornithopter wing.

Wing-powered flight typically imparts an up-and-down "porpoising" motion. Involuntary porpoising was one of the flight effects the original X-1 team had to overcome. I suspect that phenomenon at transonic speeds would tend to make the vehicle very nearly uncontrollable: the inherent flight pattern in concert with mach buffeting leading to a positive feedback cycle. Which doesn't mean that transonic wing-powerd flight is impossible, but it's unlikely at TL8.

[Flyndaran]

Originally Posted by sir_pudding

Is it? Then almost all "-punk" divergence is also superscience. It's not plausible that Da Vinci could have built a working Ornithopter at all. I guess you can just pencil in the "^" if that makes you happier.

The V-22 has been in service since 2007. There's been only one crash since then and it was a pretty typical combat aircraft incident (and could of happened to any aircraft under the same circumstances).

Reading through ancient posts because my memory is Swiss cheese, and come to this thread. I realized that I never apologized for making a slight arrogant statement getting called without making one. So, sorry for being a bit of a douche.

(I'm trying to police my words better nowadays.)


Though now I just wonder what the cut off points SM wise flapping wings go from realistic to implausible to superscience.

[pawsplay]

So, just pondering this, ornithopters could be interesting as a transportation option. But I think they entirely lack a rationale as a combat aircraft; modern fighters and versatility aircraft are intentionally aerodynamically unstable. The trend has been toward the least wing-like behavior you can get away with.

[Anthony]

Originally Posted by Flyndaran

Though now I just wonder what the cut off points SM wise flapping wings go from realistic to implausible to superscience.

It's a materials science problem, and there are a lot of things in material science that fit under "not clearly prohibited but we have no idea how to make them, or if they can be made at all".

As a general rule, to scale up a flying creature without changing its shape, you multiply the weight by the cube of scale, the material strength required by the scale, the speed by the square root of scale, and the power required by the 3/2 power of scale.

If we go with something that's at least a competent flier, probably best to go with something in the 10 lb range; I'll go with a bald eagle. A 10 lb bald eagle has a peak speed of about 100 mph in a dive; if we want it to keep our super-eagle to less than 600 mph that means we can't multiply size by more than 36. As the SM of an eagle (based on wingspan) is generally +0, that gives us a SM +9 eagle (wingspan ~250 ft) with a weight of around 230 tons. It requires materials 36x stronger (weight for weight) than muscle and bone, with 216x the power density. The bone strength is probably within the range of advanced carbon composites; the muscle properties we have no idea how to achieve but are not clearly forbidden by physics.

It's not quite Rodan, but pretty impressive.