In article ,
says...
In article ,
Doug... wrote:

Where are you getting your cost estimates? Off the top of your head?
You have no real idea what the costs would be on either side. Good luck
getting capital based on your gut feelings as to what the costs ought to
be...

To be fair, Vincent Cate has more to go on that gut feelings. He has
fairly detailed simulations, and cost-estimate spreadsheets, all of
which are open and available to critics. He also seems to have a small
group of helpers who presumably might point out any blatant mistakes in
the simulation or estimates.

Of course he could still be blatantly wrong for some reason, but it's
not fair to say that he's just making stuff up. He's put a fair amount
of time into getting reasonable numbers.

OK -- I'll accept that he's put some time into getting his numbers.
That is certainly not obvious in his posts, where he simply tosses out
numbers like "this will cost from 100 to 1000 times less than chemical
rocket systems." Without any clue as to his assumptions and premises,
it's hard to accept those kinds of figures.

I still have a hard time believing in his faith in tether systems -- I
truly believe that the engineering aspects are going to be far more
difficult to manage than he seems to think. One of the things I can't
understand about his proposal for getting lunar materials via tether is
that he seems to be proposing that you can deploy a tether from lunar
orbit and affix a scoop to the end of that tether that will scoop up
lunar materials. I know quite well how uneven the lunar surface is at
the scale of a scoop attached to what amounts to a constant-length
tether, and I have a fair idea of how much energy the impact of that
scoop along such an uneven surface will take out of the system. And how
many oscillations it will set into the tether. I just don't see those
issues being addressed.

I'd love to see them addressed, since *any* system of moving mass from a
planetary surface into an orbital state is worth exploring. While I
accept your statement that Vincent has done a lot of research into this
issue, I haven't seen the real ball-buster issues addressed in his
posts...

Doug