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Re: starship-design: Tugs

On Sun, 27 Jul 1997 12:36:20 +0100 TLG.van.der.Linden@tip.nl (Timothy van
der Linden) writes:

>I wonder if these tugs are heavy enough to damp the sail. I also 
>where they get their power from (and how their outlet doesn't damage 
>the sail).
>You also write "start to flap or wrinkle", sounds like you assume they 
>flapping very slowly.
>Anyhow, why would they start to flap? Flapping is caused by turbulence, 
>wonder where we would get that from.
>That leaves wrinkling, which can only be caused by uneven beam 
>Uneven beam densities indeed may be really troublesome. They will not 
>wrinkle the sail, but also start to turn it (since the pressure on one 
>of the center of mass is bigger than on the other side).
>Oh wait, wrinkling is likely not an issue, since we will make the sail 
>that there is a slighly outward pressure that keeps the sail streched. 
>very big (catastrophic) uneven beampressures will then wrinkle the 
>I wonder what the concequences of such high uneven beampressures will 
>If only we could make parts of the sail transparent at will...

Uh, just a note folks, really quick (I'm working on my rebuttal for my
long range tanker idea).  Stretching the sail will not stop catastrophic
vibrations.  Even systems in pure tension suffer from vibrations.  And
one of the biggest fears of any engineer worth his salt is something
called the RESONANT FREQUENCY (go talk to your engineering professors,
ask them about the Tacoma Narrows Bridge).  With many tension lines, a
HUGE sail area, and a microwave wind that we must admit won't be
absolutely homogeneous (nothing in life is, sigh), there will be some
vibration in the sail (ever see a taut line vibrate in the wind?)  If the
frequency of this vibration approaches something called the resonant
frequency, and this frequency may well be rather small in such a huge
structure, the amplitudes of the vibrations will compound with increasing
force until the structure fails.  ANY structure, device or whatever, if
operated upon continuously by a forcing function at or near its resonant
frequency, WILL tear itself apart, even if the forcing function is
relatively small.

Okay guys, find me a solution for this.