[extropy-chat] Space elevator vs. space pier

[Eugen Leitl]

On Fri, Feb 16, 2007 at 02:27:38PM -0600, Chris Petersen wrote:
> 
>    I'd be interested to hear any thoughts on comparison of feasibility,
>    cost/benefit, and failure modes between the space elevator and the
>    space pier.
>    [1]http://autogeny.org/tower/tower.html 

"Compared to the skyhook, which is just barely possible with even the theoretical best material properties, a tower 100 km high is easy. Flawless diamond, with a compressive strength of 50 GPa, does not even need a taper at all for a 100 km tower; a 100-km column of diamond weighs 3.5 billion newtons per square meter, but can support 50 billion. Even commercially available polycrystalline synthetic diamond with advertised strengths of 5 GPa would work. Of course in practice columns would be tapered so as not to waste material; and the base of the tower would be broadened to account for transverse forces, such as the jet stream. Only the bottom 15 km (i.e. 15%) of the tower lies in the troposphere and would have to be built taking weather into account."

This answers the question pretty much by itself. Solid beams
of diamond, 100 km high. We can synthesize diamond, but only
in relatively small, discrete chunks. Without machine phase chemistry,
this is way out of reach.

However, the maglev accelerator idea would also work on Earth, a bit.
A maglev acceleration track built up the slope nearby a suitably
located conical mountain (volcano, most likely) near the equator
can substitute the first or even the first and the second stage,
allowing acceleration of a rocket and/or a hypersonic scramjet stage
to the ignition regime and release at several km above sea level,
which then reaches Mach 25 on own power and enters LEO. On the other 
hand, one could just strap such a stage to a supersonic equivalent
of an An-124 (150 t payload capacity), and release it (Concorde
maximum flight height was about 18 km, maximum speed was Mach 2).

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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