[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: vaulting pterosaur launch, questions



I think the physical requirements for a standing/leaping launch are greater than a running launch.

Do you have any particular mechanical parameters in mind? I don't think the physical requirements are actually greater.



While it may be easier for a bird with the neccesary adaptations, I would think a standing launch would be a more derived form of flight, and the basal launch technique would either be running into the wind, down a slope, or dropping from a high perch.


Dropping from a perch (i.e. gravity assisted launch) seems plausible as a basal launch strategy, assuming arboreal, gliding ancestry. Running into the wind or down slopes strike me as much less likely, as the specific requirements of terrain and conditions seem unlikely to be met with enough regularity. And, if wind was truly required, then leaping into the wind would be just as good as running into it.

But archeaoptyrx could sustain flight, the problem was getting airborne and the trouble it would have flapping its wings on the ground, right? a running start into a head wind could be sufficient to get airborne to allow for weak flapping to do the rest.

It's ability to sustain flight is not certain, though it should have been able to cruise for a bit. The problem is indeed largely with launch, and that is likely best solved by leaping for an animal with its build. The running start into the wind might do the trick, but jumping into the wind would probably do even better.


True, but I think any animal that does a leaping takeoff from the ground, is already adapted for flight, I have a hard time beleiving it is the basal launch technique

Well, running launch is only present as a derived state in living birds. Granted, the basal state in neornithines is already heavily flight adapted, but I still don't see why leaping should not be the basal launch technique. For an animal with long hindlimbs, like Archaeopteryx, a leaping launch provides similar launch velocity, with greater clearance for the wings, over less launch distance, in a shorter period of time (as compared to a running launch).



I'm not talking shear here (30 knots consistent straight in is at my limit, if not just above it), but smooth laminar flow over elevated coastal terrain.

If you're not experiencing gusts or shear, then where are you extracting your energy? I was under the impression that you were referring to deflected air at ridge features, which would be a form of shear energy.


Coastal lift is the most consistent lift I know of, and presents in my view the lowest barrier to controlled flight. This doesn't mean thats how it happened, but I wouldn't be surprized if controlled flight arose from pterosaurs or therepods living near the beach, or consistent wind.

Not a bad thought.

Of course birds do that as well, and it isn't a requirement. However, as with the Wright brothers, you can't very well have powered flight until you can have controlled flight.
The transition form has to be viable, and I think a coastal soaring unpowered flight form is viable.
At least more viable than something clumsily flapping to extend its glide between trees.

I don't entirely disagree, but for sake of argument I do note that extended, controlled marine soaring among modern birds is actually a fairly derived and control-intensive exercise.



Among human foot launched flight, a lot of the time all you need to do is walk to the edge of a coastal dune with a neutral/negative angle of attack, and then increase angle of attack at the edge, and away you go- no leaping or running required at all. It should get even easier as it is scaled down.
A an early bird or pterosaur need not neccesarily run or leap at at all, just waddle up to the edge and unfold its wings

Indeed; a gust over a ridge is a powerful source of energy. I doubt that pterosaurs launched bipedally (see earlier posts in the thread) so I rather imagine that pterosaurs didn't waddle up to cliffs and unfold the wings in quite that manner, but a bipedal or quad leap off a ridge into a strong gust would be a decent way to get airborne, presuming that the aforementioned incipient flight was not intended as a method of escape (since reliance on ridges for your getaway is unlikely to be sustainable).



Cheers,

--Mike


Michael Habib, M.S. PhD. Candidate Center for Functional Anatomy and Evolution Johns Hopkins School of Medicine 1830 E. Monument Street Baltimore, MD 21205 (443) 280-0181 habib@jhmi.edu