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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Fri, 22 Jun 2001 23:35:52 GMT
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Viewed:
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94 times
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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.
later,
David Drew.
----- Original Message -----
From: "Jason J. Railton" <j.j.railton@cwcom.net>
Oh please. Drag calculations are only approximations for something immersed
in a fluid. You're not going to get conventional boundary layer effects
when you only bump into a single gas molecule every few meters. You could
consider molecular impacts as individual retarding impulses, but if you've
got enough power to move your own mass that fast, their net effect on
forward velocity is still going to be negligible. The only concern is their
net effect on your orientation and course, and that's if you solve the
problem of the actual damage caused by the impacts.
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Message has 2 Replies:
 | | 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. (...) (24 years ago, 23-Jun-01, to lugnet.space, lugnet.loc.au)
| | | Re: Wings [was: Re: Building big]
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| (...) No, it's not..:-) At STP (Standard temperature and pressure, 1atm and 273K if IIRC), only 22.4 lt. of any gas would have 6.022x10^23 molecules. Your number given above is quite negligible when compared to this I think. You must consider (...) (24 years ago, 25-Jun-01, to lugnet.space, lugnet.loc.au)
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Message is in Reply To:
| | Re: Wings [was: Re: Building big]
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| (...) Oh please. Drag calculations are only approximations for something immersed in a fluid. You're not going to get conventional boundary layer effects when you only bump into a single gas molecule every few meters. You could consider molecular (...) (24 years ago, 21-Jun-01, to lugnet.space, lugnet.loc.au)
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