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Re: shuttle disaster (space elevators)

Paul E Condon writes:
> It is not hard to compute the tension in a space elevator ribbon. (It
> would be a fair question for a final exam in an undergraduate mechanics
> course.)  It depends on position along the ribbon, on the Earth
> parameters (size, rate of rotation, etc. )...

In particular there is no reason for there to be any significant tension is
the cable at the base.  With proper controls such a cable should just hang
there if severed at or near ground level.  A fail-safe design would make
the connection to the bottom anchor the weakest point so that an
over-tension event would not result in a cable fall.  The real risk comes
from an impact high up on the cable.

> ...the mass-per-unit-length (kg/m) that is assumed for the ribbon.

Which must be tapered, of course.

> The last time I checked, there was not a material having a suitable
> combintation of kg/m and tensile strength.

Theoretically any material will work, but the dimensions get out of hand
when using wet spaghetti.  In practice carbon nanotubes are strong enough.
John Hasler
Dancing Horse Hill
Elmwood, Wisconsin

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