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In lugnet.space, Jason J. Railton writes:
> In lugnet.space, Joel Kuester writes:
> > In lugnet.space, Jesse Alan Long writes:
> >
> > > I appreciate the fact that you do agree with me but I must truthfully say
> > > that I never considered the fact that friction does indeed keep together the
> > > bolts on a space craft. Are there any other sceintific laws that either me
> > > or Paul failed to consider in our thoughts about space craft, Duane? Thank
> > > you for not seeing me as evil in the LEGO space bulletin board, Duane.
>
> You're not seen as evil. It's just that if you're unsure of what you're
> saying, don't try to make out that it's absoulutely right, and people won't
> mind if your opinion differs from theirs.
>
> > I believe Paul was poorly communicating a correct idea.
> >
> > The scientific law of friction is applicable everywhere, even in space. It
> > is a law, and going to space won't make it go away.
> > What you need to understand is how this law works. The friction that we are
> > used to calling drag is the friction of air particles on a jet, or water
> > particles on a submarine. The drag is much greater underwater because the
> > water is denser with particles. This is an operation of matter states, ie:
> > the density of a liquid state is more than the gaseous state, and the solid
> > state is greater than the liquid.
>
> Just to add to this, possibly blurring the arguments but hopefully drawing
> nearer to a consensus. There is friction in space between a moving body and
> the occasional particles it meets, but in a fluid such as air or water there
> is also friction between adjacent particles (molecules) in the fluid. Fluid
> molecules can not just move anywhere at any time and speed - they are
> dragged by surrounding molecules - this is an explanation of the viscosity
> of a fluid. This leads to various pressure effects which both lift and drag
> aircraft, and cause swirls of turbulence as the fluid tries to rush in
> behind a moving body. Turbulent (moving) air is at a lower pressure,
> causing yet more drag behind an aircraft.
>
> In space, molecules distributed sparsely throughout a vacuum have very
> little interaction, and so have negligible viscosity. No matter how fast
> you go, the molecules are still spread out. Quite simply, they do not
> behave fluidly - merely as individual particles. So, a moving body would
> only really impact with each one individually. This might cause it to roll
> along the hull causing friction, or it may bounce off. Either will impart
> some energy onto the hull, but neither case counts as viscous drag from a fluid.
>
> > The reason drag is a moot point in space is because it is a near-vaccuum.
> > The amount of particles is so low that you rarely bump into them, and
> > therfore there is no effect. The lift a wing creates needs particles to
> > move around the wing (faster on the top and slower on the bottom, due to the
> > diffence in the surface areas of the top and bottom of a wing) and the
> > difference in speed this creates causes a pressure tension to literally pull
> > the wing up. I am just going by memory for this explaination right now...
> > there is a lot more to it than that, but thats the basic concept behind wings.
>
> [Okay, this is the geeky bit, and it goes way off-topic, but that hasn't
> stopped anyone so far:]
>
> Well, it was good enough for the Wright brothers, and everyone else up to
> about 50 years ago. It's actually down to viscosity, and the angle of the
> wing to the airflow, not it's shape. Have you ever questioned how even the
> old barnstormers used to fly upside-down, if the curve of the wing had to be
> on top to get lift?
>
> If you just angle up a flat plate with rounded ends in a slow airflow, in a
> wind tunnel with smoke lines, you see something quite interesting. You'd
> expect air to be deflected downward by the plate, but it isn't. Forcing air
> downwards creates pressure to force it back up again. What actually happens
> is the air moves up to the wing, just under the leading edge, then the
> airflow splits to go rearwards, but also circulates forward, up and over the
> front. The lower airflow then curls around the trailing edge and meets up
> with the upper airflow before drifting off rearward at exactly the same
> height as it arrived. Overall, the air behind the wing is moving at the
> same height and speed as it was in front, and there is no overall force
> up/down or forward/back on the wing.
>
> But, as you sharpen the trailing edge, and speed up the air flow, the
> viscosity of the air means it can no longer curve up around the rear edge.
> The rear circulation is forced further back, dropping off the rear edge of
> the wing and leaving some wash in its wake. The circular motion at the
> front continues, and this is what gives you the speed (and pressure)
> difference above and below the wing.
>
> Not convinced? Look at footage of US Navy steam catapult launchers. You'll
> see each aircraft leaving behind a roll of steam as it is launced, left by
> the trailing edge of its wings. This is the rear circulation being left behind.
>
> Now the really geeky / head-spamming bit is this. You also get circulation
> around the wingtips (look at Concorde landing). This is the higher pressure
> air under the wing leaking around the wingtip and onto the top. These are
> all simple pressure effects, but they're desparately trying to restore the
> air to a neutral position. These swirls actually link the leading edge
> circulation with the trailing circulation left behind in one giant toroid,
> like a smoke ring stretched out all the way from take-off to landing. In
> reality, in our viscous fluid, it disperses behind the aircraft, but
> mathematically that's what's happening.
>
> Don't care? Ah well... :-)
>
> > few particles in space = insignificant friction to the craft.
> > near vaccuum in space = no pressure and therefore no "lift" possible.
>
> Quite so. I'm amused by sci-fi that gets it horrendously wrong. Macross is
> a great one - using air-brakes, and banking by about 30° to turn in space.
>
> Jason J Railton
The first problem I have, Jason, is that I am not sure that everyone else is
right, either on these bulletin boards and I know for a fact that I am not
probably right in my ways of thought in my life. Would an overheated engine
become a problem in outer space because if it does become a problem in outer
space, you could always use some Castrol (variant GTX) and some Gumout Warp
Coil Cleaner (I saw that last product in an advertisement) on your
engine(s). I believe that poor communication leads to miscommunication
between people and this was certainly an example of this problem, Jason.
We have established that there is LESS friction and gravity in outer space
but now a new question occurs to my mind. You say that gas provides the
least friction and gravity, solids provide more gravity and friction, but
that liquids provide the most gravity and friction. (The increase of
gravity and friction therefore, at least to my mind, must also increase the
amount of drag that an object uses in that type of armosphere.) What
comprises of the most molecules in outer space and if outer space includes
particles from all three types of matter (five in you include gels and
plasmatic materials but they are more of a transitionatory element than an
actual object), then how would the mixed particles react to an object that
is moving through that domain of existence, that is how would a space craft
be affected in terms of drag in space if all three types of objects exist in
outer space?
I believe that the pilots of those old airplanes simply wanted to have fun
so they flew upside down in order to appear as though they were really some
big hot shot, that and bacck in those days, there were not that many ways to
impress women so these pilots flew upside down to get dates with women. I
am not sure that all of my information is correct on this subject but due to
those first pilots, stunt flying is a fairly large business today. The Blue
Angels (not to be confused with a Wing Commander squadron of the same name)
and the Thunderbirds are the most modern example of this type of flying with
aircraft.
I have three last questions to tell you, Jason. The first question is with
air pressure on space craft. Am I right by saying that the air spilts to go
under and over the wing but ends up meeting at the back of the wing or is it
more complicated than that conclusion to the information, Jason? The second
question is what happens as a result of the more sharpened trailing edge
creating a wake from the wing? The final question is are toroids those
white trails that we see in the sky when jet craft are in the sky that are
made of this steam and are also composed of those rear circulations behind
these aircraft? I thank you for answering my letter, Jason.
Jesse Long
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Message has 2 Replies:
 | | Re: Couldn't resist
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| (...) And I thought I'd drifted off the subject... :-) I don't know of any form of reciprocating or rotating engine that could propel you through space, so engine oil seems a bit pointless. As for overheating, the only way to disperse heat in space (...) (23 years ago, 27-Jun-01, to lugnet.space, lugnet.off-topic.geek)
| | | Re: Couldn't resist
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| Why is it that whenever YOU think, MY head hurts? I really wish this were clear enough to follow, because it sounds semi-interesting, but as it is, I'm just painfully confused. Take care, Soren (22 years ago, 25-Jan-03, to lugnet.space, lugnet.off-topic.geek)
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Message is in Reply To:
| | Re: Couldn't resist
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| (...) You're not seen as evil. It's just that if you're unsure of what you're saying, don't try to make out that it's absoulutely right, and people won't mind if your opinion differs from theirs. (...) Just to add to this, possibly blurring the (...) (23 years ago, 26-Jun-01, to lugnet.space, lugnet.off-topic.geek)
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