Subject:
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Re: Hypothetical design question
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Newsgroups:
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lugnet.space
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Date:
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Mon, 23 Jun 2003 13:48:42 GMT
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Viewed:
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537 times
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In lugnet.space, George Haberberger wrote:
> In lugnet.space, Sylvia Tresto wrote:
> > Okay, just something I thought of while fiddling with my LEGO: An aerodynamic
> > desigh is only handy in atmosphere and not necessary in space, right? I remember
> > it from physics lessons and some posts in this newsgroup. But space is not a
> > true vaccuum, is it? There is all sorts of stuff out there, even if it is only
> > on a molecular or atomic level. So if a spaceship had a revolutionary drive
> > which would allow it to travel close to lightspeed (let's stay true to Einstein
> > and assume faster is no option) it should be very aerodynamic or its would
> > sustain heavy damage from even the smallest of particles out there. Am I right
> > or have I completely overlooked something?
> >
> > Love, Sylvi
>
> Sylvi,
>
> Aerodynamics is complex. One usually divides aerodymanic behavior into different
> categories, depending on the speed of the vehicle in comparison to the speed of
> the particle. If your vehicle is traveling under particle speed (the speed of
> sound for air), you have subsonic, incompressible flow. A little faster, you
> have transonic flow, then supersonic, then hypersonic.
Wow, that's quite a bit more complicated than I assumed...
>
> Shapes that you may consider aerodynamic are typically designed for
> subsonicincompressible flow situations, where the velocity of the vehicle is
> about 80% or less of the Mach speed (the speed of the individual particles in
> the flow), the fluid does not compress, and the fluid is considered a continous
> liquid. Think a sport car, TGV train, jetliner.
Yup, I had those in mind for vehicles which actually travel through atmosphere.
>
> Supersonic flows create aerodynamic shapes that are very thin and pointed, think
> the Concorde.
>
> Very high speed near vacuum flows react very different, you end up with
> hypersonic flows, and sharp leading edges can get hot, very hot. Think of Apollo
> re-entry capsules. You dnn't really have a fluid-flow, just lots and lots of
> individual particles hitting the craft.
>
> So, for a near light speed craft, anything hitting it would probably destroy it,
> if it didn't have some sort of shield. I can't find the link, but there is a
> page that describes very nicely what happens when an object the size of a soup
> can hits a Star Destroyer at half the speed of light ( a huge explosion).
>
> Thanks,
>
> George
No thank YOU, George, for clearing some things up.
What about this, taken from the SF novel Revelation Space by Alistair Reynolds,
it made me wonder wether or not I should make my new ship look like a needle:
"Space only approximated a vacuum at slow speeds. Up near lightspeed - which was
where these ships spent most of their time - it was like cutting through a
howling gale of atmosphere. That was why they looked like daggers: conic hull
tapering to a needle-sharp prow to punch the interstellar medium." Is this a
non-sensical design (from the point of view of physics and not esthetics)?
Love, Sylvi
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Message has 1 Reply:
 | | Re: Hypothetical design question
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| (...) -snip- (...) Sylvi, This is an interesting reference. I can only guess at Reynolds' inspiration, though it does sound like an extrapolation of designs based on hypersonic flow theory (on that front, see (URL) -- note how the optimal shape (...) (21 years ago, 23-Jun-03, to lugnet.space, FTX)
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Message is in Reply To:
| | Re: Hypothetical design question
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| (...) Sylvi, Aerodynamics is complex. One usually divides aerodymanic behavior into different categories, depending on the speed of the vehicle in comparison to the speed of the particle. If your vehicle is traveling under particle speed (the speed (...) (21 years ago, 23-Jun-03, to lugnet.space)
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