Re: Towers to the Stars

From: Doug Jones (
Date: Tue Feb 29 2000 - 23:19:08 MST

Spike Jones wrote:
> Robert J. Bradbury wrote:
> > > > I wrote about the Landis Tsiolkovsky Tower design paper in JBIS.
> >
> > I htmlized it... See:
> >
> > and pointers from that. Geoffrey Landis is a very serious engineer, so...
> Robert, I got to the same point Landis did in my 1993 paper. I will snail
> mail you a copy if you wish, or better yet, I will scan and email it. I
> derived the formula for the cross sectional area in terms of altitude, then
> could not integrate, for the expression is quite complicated. I did the
> same thing Landis did: numerical integration. {8-[ I used excel for
> that purpose.

Ah, a fellow abuser of excel. I've even used it to calculate iengine
injector layouts and their mass flow distributions, via some ugly
thresholding functions and indirect referencing.
> I wonder if anyone has managed to perform that integral and get a closed
> form solution for the mass of a skyhook in terms of specific strength of
> the material and the mass and rotation rate of the planet about which it
> orbits. Have you heard of such a solution? That paper was shortly before
> the web changed everything.

I could have sworn that Moravec did that, but damn if I can remember the
> When I did my paper, I mentioned spider silk, but not diamond. I didnt
> have a theoretical tensile strength of diamond. Do you have that?

Skyhooks and the tensile strength of various materials were discussed in and/or tech in the last month- you might try a Daja

> Also, I think someone mentioned a isosynchronous cable on Mars. I
> concluded in 1993 that it is faaar more feasible there than on Earth.

Yep, I looked at skyhooks attached to Phobos, too- it's the obvious
source for materials, and is a mighty momentum bank. Trolling the hook
through the upper atmosphere of Mars at 252 m/s turns out to be right
around mach one in cold CO2. The upper branch of the tther can terminate
well below Deimos and still throw objects at far beyond escape velocity-
no "jumprope" problem as with an aresynchronous tether.

The electrical supply for the lower end of the tether is provided by
transonic windmills...

Doug Jones
Rocket Plumber, XCOR Aerospace

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