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Re: starship-design: Tugs

L. Parker wrote:

>The link that Timothy just posted to Landis's paper on sails also has other 
>pages which reminded me of something I had quite forgotten. JPL actually 
>designed several sails for a mission to Halley's comet. NONE of them used 
>the "parachute" arrangement with cables attached to a sail. They were just 
>big square kites with steering vanes and a minimal structure. Even the 
>structure may not be necessary though. 

This is because they were solar sails, so the forces expected to act
upon the sail are very very small.  Which just couldn't be the case
for any practical interstellar laser sail.

>Suppose the structure was built-in to the sail itself? If part of your 
>fabric contained hollow channels which could be inflated with gas or foam 
>to stiffen the sail, you wouldn't need any structure at all. Payload 
>fraction could go way up or the sail size down.

That would be extra structure.

I think large laser sails are more trouble than they're worth, but
the most efficient way to stabalize its structure would have to
be an active mechanism.  Something like many patches which can be
rotated up to 90 degrees with micractuators.  They'd be able to
effectively adjust the transparency of the sail on a local basis.
    _____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
/___________\ "Mari-san...  Yokatta...
\=\)-----(/=/  ...Yokatta go-buji de..." - Karigari Hiroshi