[extropy-chat] Space elevator numbers III

[David Masten]

On Thu, 2007-02-15 at 10:23 -0500, Keith Henson wrote:
> >I think a terrestrial elevator is extremely more demanding, both
> >because of the scale, and of the issues (satellites) you mention.

Not to mention the materials science and economics.

I'd place the odds of having a terrestrial tether system of any sort
operational within the next 20 years at around one in a million. Here is
my reasoning: The mechanics of a really long tether requires near
perfect carbon nanotube technology (or equivalent). The problem right
now is getting the nanotubes with minimal inclusions, at a sufficient
length, in large quantities. There are some real challenges here.

Then there is the economics: any advances in material sciences towards a
tether are also advances toward cheaper rocket launch capability. As
best as I can tell, tether systems are only marginally better than
current, traditional launch systems, so any improvements to rocket
launch vehicles make rockets better than tethers. My bet is on cheap
rocket launch, which is why I started Masten Space Systems.

With lunar tethers the materials science is at least ready, but again,
why would it be cheaper than an L1-moon shuttle? Keep in mind that
perturbations from the Earth and Sun make station keeping painful for
objects in long term lunar orbits.

Dave