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Re: Massive answer to the mess of pterosaur mass



I did a quick and dirty calculation on Qn flight performance using Mark's weight of 250 Kg and Mike's wing area of 9.8 Sq.M. (from memory -- Mike, correct me if I'm wrong on the area -- I used a span of 11.2 meters, so also correct me if you'd prefer I use a lower span). Using a frontal area that I knew to be a bit low (and thereby requiring less power from the animal), this combination would require that at least 22% of the animal's mass be devoted to flight muscle and that with that muscle fraction, that the animal flap continuously to maintain level flight when in steady-state atmospheric conditions (no energy input from atmospheric lift). Flapping frequency would be about 1.07 Hz. From memory, I think about 17 total hp is required, but I didn't write that down, so don't hold me to it....

If I'd taken time to go to the other computer and extract a better approximation of the frontal area a higher flight muscle fraction would have been required. This would lead to the questions, could the animals aerobically power continuous flapping (personally, I don't think so), and how well could they survive if they were forced by oxygen intake requirements to ground themselves except when substantial supplemental energy was available from the atmosphere? As an aside, the weight and wing area that I prefer still requires flapping about 60% of the time in no-lift conditions, but with a smaller flight muscle fraction and a lower power requirement.

I note in passing that the calculations above used a frontal area far smaller than Mark used in his Qn/giraffe sketch. Consequently, the giraffe Qn would have to work far harder and expend more energy to stay aloft than the numbers above. I'm not saying the animal couldn't have done it, just asking if anyone thinks its worth the doing to do a more elaborate projection of the power required considering the limited nature of the preserved materials? Mark, what frontal area do your calculations give for the body? That includes total frontal area of the non-flight surfaces, including both the torso and frontal projection of the area of the head. Mike, how about you?
JimC


----- Original Message ----- From: "MICHAEL HABIB" <habib@jhmi.edu>
To: <Mark.Witton@port.ac.uk>
Cc: <jrccea@bellsouth.net>; <dinosaur@usc.edu>
Sent: Thursday, January 17, 2008 6:17 PM
Subject: Re: Massive answer to the mess of pterosaur mass



Hey everyone,

Some comments on the pterosaur mass issue (specifically the Quetz. mass issue). I think Mark's mass estimate technique has a lot of merit, and I have run some launch calculations with his 250 kg Qn that came out reasonably well. I have tended to prefer a slightly lower mass (closer to 200 kg) myself, but that margin is actually a lot smaller than it seems. By the same token, my mass estimate and Jim's are also not actually so far off as they might seem, given how much estimate error there can be.