Micro Gravity and A Space Elevator?

On 2020-06-11 21:16, Scott Kozel wrote:
On Thursday, June 11, 2020 at 1:24:46 PM UTC-4, David Spain wrote:

Another feature not to be discounted are stops along the cable that
remain in the atmosphere. You could have observation stations in both
lower and upper troposphere, stratosphere and ionosphere. Something that
is exceedingly difficult to do today, even with balloons.

Something that I haven't heard addressed, is how to protect the cable from
aircraft collisions. No matter how well marked and lighted, sooner or later an
aircraft will hit it, resulting in the severing of the cable and the crashing of
the aircraft.

Perhaps the fixed part of the cable (the orbital tower) should end high
up, higher than planes fly and significant storms blow. The small hop
from and to the ground could be handled by winched cables, no big
problem if one of them gets hit, although the load/cab being winched up
or down may be lost, of course.

The only important reason for anchoring the cable to the Earth's surface
arises if the cable is used to accelerate significant amounts of _net_
mass (upwards mass flow downwards mass flow) to orbital or escape
velocity, in which case the cable has to bend to the west (along the
rising direction) and extract momentum from the Earth's rotation through
its connection to the surface. This connection could of course also be
designed to tolerate isolated airplane strikes, for example it could
consist of many thinner cables that connect to widely separated points
on the ground but converge to the central, main cable high up. The
failure of one or two of the thin cables could be tolerated, and the
cables could be replaced.

Another comment: accelerating a cab outwards along the cable by
"centrifugal" force at altitudes above the geosynchronous is not really
a "free ride", because the momentum has to come from somewhe either
from rocket propulsion, or from the cable's orbital momentum (which is
not suistainable), or from the Earth's rotation, via tension in an
inclined cable.

--
Niklas Holsti

niklas holsti tidorum fi
. @ .

On Friday, June 12, 2020 at 7:08:10 AM UTC-4, Niklas Holsti wrote:
On 2020-06-11 21:16, Scott Kozel wrote:
On Thursday, June 11, 2020 at 1:24:46 PM UTC-4, David Spain wrote:

Another feature not to be discounted are stops along the cable that
remain in the atmosphere. You could have observation stations in both
lower and upper troposphere, stratosphere and ionosphere. Something that
is exceedingly difficult to do today, even with balloons.

Something that I haven't heard addressed, is how to protect the cable from
aircraft collisions. No matter how well marked and lighted, sooner or later an
aircraft will hit it, resulting in the severing of the cable and the crashing of
the aircraft.

Perhaps the fixed part of the cable (the orbital tower) should end high
up, higher than planes fly and significant storms blow. The small hop
from and to the ground could be handled by winched cables, no big
problem if one of them gets hit, although the load/cab being winched up
or down may be lost, of course.

The only important reason for anchoring the cable to the Earth's surface
arises if the cable is used to accelerate significant amounts of _net_
mass (upwards mass flow downwards mass flow) to orbital or escape
velocity, in which case the cable has to bend to the west (along the
rising direction) and extract momentum from the Earth's rotation through
its connection to the surface. This connection could of course also be
designed to tolerate isolated airplane strikes, for example it could
consist of many thinner cables that connect to widely separated points
on the ground but converge to the central, main cable high up. The
failure of one or two of the thin cables could be tolerated, and the
cables could be replaced.

Another comment: accelerating a cab outwards along the cable by
"centrifugal" force at altitudes above the geosynchronous is not really
a "free ride", because the momentum has to come from somewhe either
from rocket propulsion, or from the cable's orbital momentum (which is
not suistainable), or from the Earth's rotation, via tension in an
inclined cable.

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.

"Scott Kozel" wrote in message
...

On Friday, June 12, 2020 at 7:08:10 AM UTC-4, Niklas Holsti wrote:
On 2020-06-11 21:16, Scott Kozel wrote:
On Thursday, June 11, 2020 at 1:24:46 PM UTC-4, David Spain wrote:

Another feature not to be discounted are stops along the cable that
remain in the atmosphere. You could have observation stations in both
lower and upper troposphere, stratosphere and ionosphere. Something
that
is exceedingly difficult to do today, even with balloons.

Something that I haven't heard addressed, is how to protect the cable
from
aircraft collisions. No matter how well marked and lighted, sooner or
later an
aircraft will hit it, resulting in the severing of the cable and the
crashing of
the aircraft.

Perhaps the fixed part of the cable (the orbital tower) should end high
up, higher than planes fly and significant storms blow. The small hop
from and to the ground could be handled by winched cables, no big
problem if one of them gets hit, although the load/cab being winched up
or down may be lost, of course.

The only important reason for anchoring the cable to the Earth's surface
arises if the cable is used to accelerate significant amounts of _net_
mass (upwards mass flow downwards mass flow) to orbital or escape
velocity, in which case the cable has to bend to the west (along the
rising direction) and extract momentum from the Earth's rotation through
its connection to the surface. This connection could of course also be
designed to tolerate isolated airplane strikes, for example it could
consist of many thinner cables that connect to widely separated points
on the ground but converge to the central, main cable high up. The
failure of one or two of the thin cables could be tolerated, and the
cables could be replaced.

Another comment: accelerating a cab outwards along the cable by
"centrifugal" force at altitudes above the geosynchronous is not really
a "free ride", because the momentum has to come from somewhe either
from rocket propulsion, or from the cable's orbital momentum (which is
not suistainable), or from the Earth's rotation, via tension in an
inclined cable.

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.

It certainly would be fairly spectacular to see though!

BTW, still worth reading "Fountains of Paradise" by AC Clarker.


--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net
IT Disaster Response -
https://www.amazon.com/Disaster-Resp...dp/1484221834/

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

On Saturday, June 13, 2020 at 12:01:34 PM UTC-4, Alain Fournier wrote:

[. . . .]

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.

Part of the reason for having the Earth anchor being on a platform well out
in the ocean.

Still, the various outcomes could affect shipping and aviation over a wide
area.