From: vince@offshore.ai (Vincent Cate)
Newsgroups: sci.space.tech
Subject: Re: Lunar Sample Return via Tether
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Andrew Nowicki <andrew@nospam.com> wrote in message news:<3FD9C8E8.A32A0A08@nos
pam.com>...
> AN> Having a small momentum wheel is useful for fine adjustment
> AN> of the angular velocity of the lunavator. If you do the
> AN> adjustments with the winch only, the lunavator shakes
> AN> too much, and you have to use mini rocket thrusters.
>
> VC> Do you have anything to backup either of these claims?
>
> The real rotating tether is not a rigid straight line. Gravity
> and reeling make it flex and shake. Finite element analysis
> is the only way to model the rotating tether.

Yes, I understand.  This is how my tether simulator works.
While a winch can cause waves, it can also help get rid of
them.  Also you can use it in such a way as to not cause a
problem wave.  So I don't think that using a winch means you
need to be firing rockets.

I am not convinced that a momentum wheel is any real use for a
rotating tether.  But I am happy to agree to disagree.

> I agree as long as we ignore the tether mass.

I can now simulate a winch, so we can put real numbers to
the winch stuff.

> The gravity method is useful only
> when gravity is significant in comparison with the centrifugal
> force.

I will have to simulate this winching in and out to get some
real numbers on how fast you can gain or loose angular momentum
at what distances from the moon.   But I think you could do it
at any realistic centrifugal force level, just that it could take
a bigger winch motor.

> Unfortunately, this condition shakes the tether.

But I don't think "shaking the tether" is going
to be a big problem.  Winches with simple things like a
"maximum force limit" or a "power limit" will reduce waves.
You want to pull in during the weak parts of the wave and
not so much when the tension is high, and these can do some
of this.  A real computer control algorithm could do very well
at getting rid of waves. But with even simple thing, it has not
been a real problem on my initial tests.

> PS. I have been frequenting the sci.space.tech and a few other
> newsgroups before the World Wide Web was invented. Until now I
> have never seen any novel idea posted on the newsgroups. The
> latest post by Ron Baalke "People Are Robots, Too. Almost"
> hints at the plausible explanation of this lack of creativity...

Just checking, you are saying that this thread is the first
with some novel ideas?

  --- Vince