Re: Massive answer to the mess of pterosaur mass

[jrc <jrccea@bellsouth.net>]

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.