Micro Gravity and A Space Elevator?

On Jun/12/2020 at 13:27, Greg (Strider) Moore wrote :
"Scott Kozel"Â* wrote in message

Something that I read in the literature a few years ago, what happens
if the
cable breaks?

It would depend on where it breaks, as to what part falls to the ground,
what part heads out into space, and what part might just wave around
at high
altitude and not fall.

Also the expense of rebuilding part or all of the elevator cable.

I saw someone do the math once. Ignoring any payloads, the cable itself
is so light that it "falling" on pretty much anyone or anything most
likely wouldn't do much kinetic damage. As for other problems (say falls
against a road, truck runs into it) that's another issue.

What happens is a complex issue. I wouldn't trust it to gently lay
itself on the ground. If the cable breaks, I would get out of its path.

Imagine if the cable breaks near the top. The broken off part just flies
off, we can ignore that part. The top of the cable still anchored to the
ground is still pulling the bottom part up but the bottom part is
pulling down harder than the top part, so the cable is slowly coming
down vertically. At first the cable is still taut, but it is gaining
vertical speed downward. This puts some slack in the top of the cable,
not the bottom where the pull is stronger. The bottom part of the cable
is accumulating on the ground near the anchor point. After a while, the
top part has too much angular speed for its lower altitude and starts to
pull the cable eastward. As the cable gets lower, this eastward pull
becomes stronger and the cable that was on the ground near the anchor
point starts being pulled eastward. When all the slack of the grounded
cable is taken up, the cable now has significant eastward speed and you
have a huge mass with significant speed pulling eastward. SNAP. Not pretty.

Now imagine that instead of breaking near the top, the cable breaks near
geosynchronous altitude. Much the same as above happens again, even if
the top part at geosynchronous altitude is not pulling up, it wants to
stay at its altitude but is pulled down by the bottom part. Things go
along much as in the case where the initial break was much higher up, it
only happens in a different time frame.

Imagine this time that the cable breaks at an altitude of 10,000. This
time ignore the bottom part which hits the ground. A little more
surprisingly, the top part will do much as the two examples above. The
cable first goes up vertically, then the bottom part loses angular
momentum. It starts pulling the cable westwardly, this westwardly pull
accelerates, but mostly in the bottom, while the top is accumulating
some slack. After a while, the top part receives the cue that there is a
big westwardly pull. Again SNAP.

In reality, all of the above can happen together. Different parts of the
cable will be pulling in different directions there will be some slack
accumulating here and there and the the cable becoming taut again and
snapping here and there.

The pieces falling to the ground might not be taut. Who knows, you could
have some big balls of cable that have curled up. And even if you don't
have big balls of cable, you can have some cable fall lightly to the
ground and then be dragged eastward pulling anything with it.

The physical properties of the material used to make the cable would
also have an effect on what happens.

Just a simple cable breaking could have a mostly unpredictable chaotic
outcome. One could put in some apparatus here and there on the cable to
keep it somewhat under control. If you roll in the cable where some
slack accumulates, you don't end up having wide speed differences for
different parts of the cable.

It certainly would be fairly spectacular to see though!

Yes. :-(


Alain Fournier