In sci.space.policy Vincent Cate wrote:
Sander Vesik wrote in message ...
Depending on whetever getting them would require going to an unkown
and anproven technology for which you not just can't really get
proven materials but also you need to do a many orders of magnitude
higher up-front investment.

The main material is Spectra-2000. This is a well proven fishing-line
and kite-line material.

Because a tether system can be so much smaller, it should not be
orders of magnitude more investment.

"should nbot be" without numbers is not worth much.


For initial profit based missions, tethers
simply don't enter into the picture.

Time will tell.

Vince:
I don't think it would cost $400 to $500 mil, but it is clearly
hard to say.

SMART-1 cost $100m. Its a small orbiter and was launched as a add-on
cargo on a flight where most of the expenditure was paid for by other
satellites. You are going to need the full capacity of a heavy launcher,
so $150 - $180m. Assuming that whatever you are launching cost you $200m
to develop and build is reasonable and you co-incidentialy have arrived
at $400m.

There is some reason to believe that if a government organization can
do something for $100 mil that a new startup company could do it for
much less.

Provided it does not have to work, yes. If it does have to work, it becomes
much less clear, esp as they will have to fly a lot of micro/nanosats
to get the basic know-how and technology. Never mind that they will also
have to figure out the descent and return side (SMART-1 is orbiter).


The Falcon-V will take 10,000 lbs to LEO for $12 mil. This should be
enough for a probe using a tether. We do not need a $150+ mil launcher.
It is the all chemical rocket approach that need lots of starting mass.

I will believe that when it has launched at least once. And of course, the
$150m launcher puts rather more than 10k lbs in LEO. Doing a lunar return with
that small amount of mass from *LEO* will be tricky.


To me it seems much easier to justify an investment if you end up
with a low ongoing cost and 100 kg a month than a deal with a
onetime payback of 20 kg.

Really? have you tried writing this up? How much mass doyou need to launch
and how much does the thing launched cost? And please use realistic present
day costs and not arbitrarily tweaked numbers until it worked for you.

As I said about costs above, "... it is clearly hard to say". But a tether
to lift 5 Kg from the moon only needs to be like 15 to 30 Kg.
So the system does not need to be really huge.

Maybe you should start doing some numbers then? Like say how much a 100 km
spool would weight?


-- Vince

--
Sander

+++ Out of cheese error +++