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Re: Problems

To Brian

> Now that I have a concept of how to get a sail driven starship to TC in 
>less than 50 years, I'm trying to get some questions answered on the ship's 
>dry weight requirements and whether or not they can be met.
>My Argosy design, as of last night, requires:
>1000km wide sail.
>A crew of 400
>An exploration module (ion drive plus habitat) weight of 350,000 tons minus 
>reaction mass
>A maximum cruise velocity of .75c.
>A minimum power requirement of 1E18W.
>1.  Can a 1000 km wide sail made mostly of chicken wire or flimsy silver 
>foil be rigged to support a 350,000 ton ship without being ripped to shreds? 

The pressure on every part of the sail would be 10 bar (1E6 Pa). You could
easely bend chickenwire with such a force. Besides this, there have to be
connections to the ship, at these connections the pressures would be much
higher, since they collect all the force to a small area.
So if you aren't going to make connection wires every metre, I don't think
the thing will hold.

>2. Will the guy wires/cables snap under their own weight given a 10m/s^2 

That depends on the amount of cables (see above).

>3. How heavy would the cables need to be to prevent snapping.  Tim gave me 
>some equations a while back when I wanted to tether a solar collector array 
>to Mercury.  I haven't had time to try to make sense of them but he said the 
>cables would probably snap under their own weight.

Yes, but that assumed very long cables, these cables are about 2 kilometres
at max.