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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Thu, 21 Jun 2001 16:55:58 GMT
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Viewed:
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1132 times
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In lugnet.space, David Drew writes:
> On 21/6/01 5:19 AM, "William R. Ward" <bill@wards.net> wrote:
>
> > David Drew writes:
> > > On 20/6/01 5:54 AM, "William R Ward" <bill@wards.net> wrote:
> > >
> > > > Actually, this is false. Space is a vacuum - there is no air, only a
> > > > few stray molecules of gas or cosmic dust. As a result, there is no
> > > > friction and thus no need for wings or streamlined shapes on space
> > > > craft. Also, there is very little gravitational pull, so the lifting
> > > > power of wings is useless.
> > >
> > > Actually, if you're travelling at near-light velocities, the density of the
> > > interstellar medium becomes high enough (especially within solar systems, so
> > > I guess that would be intrastellar medium) that a streamlined shaped would
> > > become essential. Even then, there would be both heavy erosion of whatever
> > > impact-shielding you have, and heavy drag on the ship.
> >
> > That may be true, but I don't think anyone knows for sure, because we
> > haven't tried going that fast yet. My spacecraft follow a very "hard
> > SF" policy - no FTL travel, no artificial gravity, etc. But that's
> > not to say that it's the only way...
>
> We know it's true, since we have our nice and handy fluid mechanics
> calculations. The drag experienced by a vehicle depends on a number of
> factors, including surface area, drag coefficient, viscosity and density of
> fluid, and the velocity of the vehicle.
>
> Obviously, for low speeds, the drag is near zero, since density is near
> zero. But get near to 3*10^8 m/s, and it becomes a whole different story.
> There will probably be other effects coming in as an object approaches
> relativistic velocities, which we cannot account for, but there are unlikely
> to reduce the drag.
>
> Later,
> David Drew.
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.
The design may well be streamlined, but in a way to deflect impacts rather
than to smooth the flow of passing fluid. Wedge-shapes rather than
tear-shapes, since you don't have to worry about drag from a turbulent wake.
I mean, it's hardly rocket science, is it? Oh, hang on...
Jason J Railton
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Message has 3 Replies:
 | | Re: Wings [was: Re: Building big]
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| (...) How many posts have resulted since my comment about wings in space? My calculations say that there have been about fourty or fifty posts since my comment about wings in space. My space craft is generally wedge shaped, Jason, if you want to (...) (23 years ago, 22-Jun-01, to lugnet.space, lugnet.loc.au)
| | | Re: Wings [was: Re: Building big]
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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 (...) (23 years ago, 22-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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| (...) We know it's true, since we have our nice and handy fluid mechanics calculations. The drag experienced by a vehicle depends on a number of factors, including surface area, drag coefficient, viscosity and density of fluid, and the velocity of (...) (23 years ago, 21-Jun-01, to lugnet.space, lugnet.loc.au)
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