ted@imsvax.UUCP (Ted Holden) (09/11/85)
Everybody who has ever studied pterosaurs and done any
THINKING about them has arrived at the same conclusion: that
it would be physically impossible for them to fly, but that
they obviously HAD to fly in order to survive (since they were
built for flying and could not have earned a living otherwise),
hence an enigma, which I claim nothing other than Immanuel
Velikovsky's theory of a lesser FELT EFFECT of gravity in the
archaic world could possibly account for. The following quotes
are from Adrian Desmond (from "The Hot-Blooded Dinosaurs"):
"The combination of great size and negligable weight must
necessarily have resulted in some fragility. It is easy to
imagine that the paper-thin tubular bones supporting the
gigantic wings would have made landing dangerous. How could
the creature have alighted without shattering all of its
bones?"
"Many larger birds have to achieve a certain speed by
running and flapping before they can take off and others
have to produce a wing beat speed approaching hovering in
order to rise. To achieve hovering with a twenty three foot
wingspread, Pteranodon would have required 220 lbs of flight
muscles as efficient as those of hummingbirds. But it had
reduced its musculature to about 8 lbs., so it is
inconcievable that Pteranodon could have taken off
actively."
(Desmond obviously means THE POWER of 220 lbs of muscle, not the
added 220 lbs of weight, which would make matters worse)
"How they could have taken to the air after gorging
themselves is something of a puzzle. Wings of such
extraordinary size could not have been flapped when the
animal was grounded. Since the pterasaurs were unable to
run in order to launch themselves, they must have taken off
vertically. Pigeons are only able to take off vertically by
reclining their bodies and clapping the wings in front of
them; as flappers, the Texas pterosaurs would have needed
very tall stilt-like legs to raise the body far enough to
allow the 24 foot wings to clear the ground. The main
objection, however, still rests in the lack of adequate
musculature for such an operation. Is the only solution to
suppose that, with wings fully extended and elevators
raised, they were lifted passively off the ground by the
wind? If Lawson is correct and the Texas pterosaurs were
carrion feeders, another problem can be envisaged. Dinosaur
carcasses imply the presence of dinosaurs. The ungainly,
Brobdignagian pterosaurs were vulnerable to attack when
grounded, so how did they escape the formidable dinosaurs?
Left at the mercy of wind currents, take-off would have been
a chancy business."
"With each increase in size, and therefore also weight, a
flying animal needs a concomitant increase in power (to beat
the wings in a flapper and hold and maneuver them in a
glider), but power is supplied by muscles which themselves
add still more weight to the structure. The larger a flier
becomes, the disproportionately weightier it grows by the
addition of its own power supply. There comes a point when
the weight is just too great to permit the machine to remain
airborne. Calculations bearing on size and power suggested
that the maximum weight which a flying vertibrate can attain
is about 50 lbs: Pteranodon and its slightly larger but
lesser known Jordanian ally Titanopteryx were therefore
thought to be the largest flying animals."
Desmond is obviously thinking in terms of power to weight,
the square-cube problem in which weight goes up like a cubed
figure (volume), while power goes up like a squared one (cross
section of muscles). However, there is more trouble. Ability to
breathe only goes up as another squared figure (surface area of
lungs). McMahan and Bonner, in "On Size and Life", note the
following:
"..a hummingbird with a mass of 4 grams must increase its
metabolic rate above the resting levelby only a factor of
about 3.3 to fly, while a 7.3 kilogram Griffon vulture has
to raise its metabolic activity to a rate 20 times the
resting level to stay airborne. Recalling that C.R. Taylor
and his collaborators (1981) found that terrestrial animals
can increase their metabolic rate to about 10 or 15 times
the resting level and taking into account the fact that
birds have relatively larger hearts and lungs than mammals,
we arrive at the conclusion that the largest birds are
expending energy at rates close to the upper limits of their
abilities while sustaining level flight in still air."
Wann Langston, writing in the Feb. 81 issue of Scientific
American, had this to say about the Texas pterosaurs
(Quetzalcoatlus):
"Aeronautical engineers quickly pointed out, however, that a
pterosaur with the shape of a pteranodon and a wingspan of
15.5 meters might have weighed as much as 136 kilograms. It
would then have lacked the muscle power to maintain level
flight by flapping its wings. Moreover, the strength of the
wing bones would perhaps have been insufficient to bear the
stresses the wings would have had to endure. Of course,
Quetzalcoatlus Northropi did not have exactly the same
proportions of Pteranodon. Even so, an animal with a
wingspan of 15.5 meters would probably have been at or
beyond the engineering limits for a flying machine made of
muscles, tendons, and delicate, hollow bones."
For the flying dinosaurs, the preceeding statements pretty
well sum up the nature of reality. However, let's delve into the
realm of non-reality for awhile. Bill Jefferys of the UT astro
dept. writes:
>I noticed with some interest in this morning's paper that Paul
>MacCready (who built the Gossamer Condor and the Gossamer
>Albatross - the first successful human-powered flying machines).
>is now building a full-scale, flying replica of *Quetzalcoatlus
>northropi*, the largest of the pterosaurs. The replica is
>intended to be accurate as to size and weight and power, and
>will operate in a fashion similar to the original creature.
>They are being assisted in this by a team of paleontologists
>headed by Professor Wann Langston, Jr., of the University of
>Texas. According to the article [1],
> "Flight was possible for the giant pterosaur
> because it was very light. The lightness resulted
> from thin-walled, hollow bones, which Langston
> compared to a mailing tube with Styrofoam plugs
> on each end."
>The fact that Paul MacCready, probably the world's foremost expert
>in the field of lightweight muscle-powered aircraft, thinks that it
>possible to build a full-scale flying replica of this creature,
>is strong evidence to me that Ted Holden has been talking through
>his hat.
What's he going to use for a power plant, Bill? An inline
Allison, like the P38 used, or a radial like in the Corsairs and
Bearcats? That's sure going to tell us a hell of a lot about trying
to fly something that sized with muscle power, isn't it?
This kind of thing isn't science at all; it's showmanship.
But I can understand why an astronomer like Jefferys would approve.
He's not interested in SCHOLARSHIP, or in trying to understand our
world and perfect it (which requires understanding our past).
Velikovsky was interested in those kinds of things. His (Jeffery's)
whole discipline is basically showmanship. What the hell else do you
call wasting billions of dollars landing some freaking clown on the
moon at a time when Americans were being drafted into what amounted
to a low-grade spectacle, and fish were not able to live in the river
flowing past our nation's capital? Nero would likely have called it
"fiddling"; Dwight Eisenhower called it "just nuts", which is what I
call it.
What does anybody call star-wars, or someone like Gerard
K. O'Neill who is out there right now spreading the gospell that
ESCAPE TO OUTER SPACE is the answer to all of man's problems as
regards overpopulation and the like? I mean, Reagan and his National
Commission on Space LISTEN to this guy. I personally regard this
character as dangerous and believe he should be SENT to outer space
permandntly and as quickly as it can be arranged, preferably by way
of one of the 16 inch guns on the New Jersey.
Oh, one more thing. I'll be there to watch McReady's mechanical
monster crash into the park grounds near the Smithsonium (which is
where I understand he intends to demonstrate it), and I'll tell you
about it. Not that it'll be underpowered, as would real pterosaurs
in our gravity; I'm sure McReady will have taken care of that. I
don't think he can CONTROL such a thing.bill@utastro.UUCP (William H. Jefferys) (09/11/85)
Ted's experts may think the Pterosaurs couldn't fly. Obviously,
Paul MacCready thinks otherwise, and no one in the world knows
more about muscle-powered flight than he does. 177 lines of
quotations, insults and obfuscation don't change the fact that
the Ted's case is by no means as overwhelming as he imagines.
--
Glend. I can call spirits from the vasty deep.
Hot. Why, so can I, or so can any man; But will they come when you
do call them? -- Henry IV Pt. I, III, i, 53
Bill Jefferys 8-%
Astronomy Dept, University of Texas, Austin TX 78712 (USnail)
{allegra,ihnp4}!{ut-sally,noao}!utastro!bill (UUCP)
bill@astro.UTEXAS.EDU. (Internet)friesen@psivax.UUCP (Stanley Friesen) (09/14/85)
In article <393@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes: > > Everybody who has ever studied pterosaurs and done any > THINKING about them has arrived at the same conclusion: that > it would be physically impossible for them to fly, but that > they obviously HAD to fly in order to survive (since they were > built for flying and could not have earned a living otherwise), Well, this could really only apply to Pteranodon and the other larger types, since *most* ptreosaurs were much smaller and would have had no problem even according to the most skeptical student. Of course, I claim that the ones whoe *really* thought about it decided that even the large species could fly. > ... The following quotes > are from Adrian Desmond (from "The Hot-Blooded Dinosaurs"): > > > "The combination of great size and negligable weight must > necessarily have resulted in some fragility. It is easy to > imagine that the paper-thin tubular bones supporting the > gigantic wings would have made landing dangerous. How could > the creature have alighted without shattering all of its > bones?" > > > "Many larger birds have to achieve a certain speed by > running and flapping before they can take off and others > have to produce a wing beat speed approaching hovering in > order to rise. To achieve hovering with a twenty three foot > wingspread, Pteranodon would have required 220 lbs of flight > muscles as efficient as those of hummingbirds. But it had > reduced its musculature to about 8 lbs., so it is > inconcievable that Pteranodon could have taken off > actively." > Gotcha, these are out of context, I have that book. Dr Desmond goes on to point out that these animals were *gliders*, not hoverers, so the dynamics of a Hummingbird simply do not apply. In fact the wing proportions are those of an Albatross, a gliding bird which almost never lands. In fact when an Albatross lands it usually crashes, that is why they are called Goony Birds! In short, the Pteranodon didn't need all that muscle, because it didn't use the same airodynamics as a Hummingbird with it tiny little wings. A recent journal article, which I have not yet been able to relocate for review here, calcualted the stall speed for a Pteranodo, that is the *minimum* *air* speed needed to sustain flight. The result was an incredible ~5mph. This means that it could take off by just facing into the wind and spreading it wings! No need at all for *any* flapping during take-off, and only a slight amount of trim and lift type flapping during flight, you know a little push now and again just to make sure it stays up. Eight lbs of muscle would be plenty adequate for this. > > (More quotes written in a popular "gee whiz" style, for drama, which seem to say the same thing as the ones above, and are equally out of context) > Wann Langston, writing in the Feb. 81 issue of Scientific > American, had this to say about the Texas pterosaurs > (Quetzalcoatlus): > > "Aeronautical engineers quickly pointed out, however, that a > pterosaur with the shape of a pteranodon and a wingspan of > 15.5 meters might have weighed as much as 136 kilograms. It > would then have lacked the muscle power to maintain level > flight by flapping its wings. Moreover, the strength of the > wing bones would perhaps have been insufficient to bear the > stresses the wings would have had to endure. More calculations based on a *flapping* flight in what was probably a glider! -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
friesen@psivax.UUCP (Stanley Friesen) (09/16/85)
The above referenced article by Mr Holden includes a number of
quotes from a popular science text which show a considerable
misunderstanding of the nature of popular science texts. The quotes
are of extreme statements which, if you read the whole book, you will
find that the author *himself* does *not* believe.
The problem is that such books must cater to popular tastes,
which often(usually) are not oriented toward "dry" technical
discussions. Thus the when trying to get across a rather ordinary set
of facts, the author must find a way of *dramatizing* the presentation
to keep his audience interested. One way of doing this is to make
outlandish statements and then discuss them back to the truth. Such
statements are rather like banner headlines in newspapers, they
introduce a subject, but do not *really* say anything. The way to read
such a thing is to ask "what is the bottom line?" or "where does the
author *end* *up*?".
As a matter of fact Dr Desmond in "Hot-blooded Dinosaurs"
comes on rather strong with this technique. Here he is trying to
overcome a second area of reader resistance, the rather unrealistic,
but deeply ingrained, preconceptions most people have about dinosaurs.
When fced with changing their prconception many people will rather
simply ignore the source of the conflict. Dr. Desmond was apparently
trying to *really* pep his book up, so that it would hold even such an
audience. The result is a "science" book that in some ways reads like
the National Enquirer. Not entirely, thank goodness, or the book would
be totally without value. At least his final conclusions are essentially
correct, even if he gets there by rather sensationalist methods.
--
Sarima (Stanley Friesen)
UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen
ARPA: ttidca!psivax!friesen@rand-unix.arpa