Subject:
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Re: Wings [was: Re: Building big]
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Newsgroups:
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lugnet.space, lugnet.loc.au
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Date:
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Sat, 23 Jun 2001 03:07:37 GMT
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Viewed:
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42 times
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In lugnet.space, Kyle D. Jackson writes:
> In lugnet.space, David Drew writes:
> > Hi.
> > I can't remember the density of space off the top of my head, but let's say
> > it's somewhere near the 1 molecule per 3m^3 like you suggest. If a vehicle
> > is travelling near the speed of light (3*10^8 m/s), then the ship is hitting
> > in the vicinity of 1*10^8 molecules per second per metre^2 of frontal
> > surface area!
> >
> > I can't be bothered working out how many molecules of nitrogen and oxygen
> > fill a 1m^3 box of air, but I think it can become clear that when travelling
> > at near-relativistic velocities, the flow of molecules over the surface of a
> > spaceship can become more than high enough to qualify it as a 'fluid', and
> > thus impose the problems of drag and turbulence suggested.
>
> Hmmm, this is pretty interesting (in an aero-geek way). I can't
> remember Avogadro's number so I won't work out the numbers, either.
6.022 x 10^23. Get computin'! ;)
> I suspect this would become a whole different branch of "fluid"
> dynamics compared to what we deal with today. Because the particle
> density is so very tiny, the whole concept for viscosity of this
> "fluid" becomes pretty messed up. Practically speaking I don't
> believe there would be any communcication between the particles
> like in fluids we encounter today. Because of that there might not
> be any fluid shear to develop to form anything like boundary layers,
> in the conventional sense. Relative to the ship the particles may
> appear to be approaching as a "fluid", but relative to each other
> the particles are still horribly distant and "non-interacting".
> Hey, maybe I can use this for my new masters thesis topic---I
> change it every 3 months or so :]
Bwaaa! I know how that goes. As long as the money is coming,
why finish it? ;)
> Of course we have to start throwing relativity at it now too, which
> is waaay beyond my area. The last pure physics we dealt with involved
> calculating whether a ladder leaning on a wall would slip out from
> under the monkey sitting it :] Oh, and something about "electricity"
> or some whacky nonsense like that ;]
An electric ladder or an electric monkey?
> Anyhow, at those speeds I can agree that drag would be caused by
> the impacting particles (if not a nuclear reaction <G>). But
> I think they would be a form of "impact drag", with transfer of
> momentum between the particle and ship. I'm not so sure any kind
> of "flow drag" would develop in the conventional sense. I have
> trouble thinking about what happens when one single particle
> crashes into gazillions hurtling along in close formation. Does
> it just "stick"??
Sometimes it tries to pass through. If nothing else it
would, I'd think, deform the atomic array it hits ever
so slightly. But if the solid object is going THAT way
at high speed, and the molecule is (relative to that)
exhibiting a radial velocity of 0.89c, I'd imagine the
effect to be similar to sandblasting. Even at the tiny
gas volumes found in the ICM/ISM.
I remember something about relativistic iron nuclei
passing through space capsule hulls and destroying
human nerve tissue being a big problem in today's space-
flight, though. It may be that all sorts of wacky
particle effects come into play at hyperspeed, because
all sorts of particles are out there shooting around,
things that the protection of our sun's emission, its
magnetic field, and the Earth's own magnetic field
render academic (or should that be elementary? I'm
torn as to whether I should go for the pun...) any
question of such interaction at our present stage of
exploration.
> I'll develop some theories and publish the book by Monday :]
"The blancmonges mean to win Wimbledon." There, done!
best
LFB
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Message is in Reply To:
 | | Re: Wings [was: Re: Building big]
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| (...) Hmmm, this is pretty interesting (in an aero-geek way). I can't remember Avogadro's number so I won't work out the numbers, either. I suspect this would become a whole different branch of "fluid" dynamics compared to what we deal with today. (...) (23 years ago, 23-Jun-01, to lugnet.space, lugnet.loc.au)
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