Micro Gravity and A Space Elevator?

On Thursday, June 11, 2020 at 8:29:45 PM UTC-4, David Spain wrote:
Allow me to refresh your memory:

On 2020-06-10 7:46 PM, Alain Fournier wrote:
On Jun/10/2020 at 18:35, Scott Kozel wrote :

I wasn't advocating or opposing a Moon space elevator, just saying
that it is
technologically feasible with today's materials.

I read somewhere that a Mars space elevator is technologically
feasible with
today's materials, but I am not sure about that.

An Earth space elevator is technologically feasible with today's ---- emphasis mine
material. See for instance
space.nss.org/wp-content/uploads/2000-Space-Elevator-NIAC-phase1.pdf
that's a little old, but materials available 20 years ago should be
available now. It would be too expensive, but technically, it is doable.
Costs estimates in that report are of $40B (page 11.4), but I would say
the author is a little optimistic, not ridiculously so, but a little
optimistic.

On Mars, I'm not sure how one would solve the problem caused by the low
orbiting moons but I think it would be doable. Anyway, for the time
being, the traffic from Mars surface to Mars orbit is too low to justify
the cost, whatever that cost would be :-)


Alain Fournier

OK, where are the experiments that would support that a 60,000 mile long carbon
nanotube cable can be made thin enough to not exceed feasible weight limits, and
be able to support the transport cab?

On Thursday, June 11, 2020 at 2:37:27 PM UTC-4, David Spain wrote:
On 2020-06-11 2:16 PM, 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.


As well as bad weather, high shearing winds, lightning strikes etc.
which would be all too common a problem no matter how well you sited the
ground station.

As far as stray aircraft is concerned: Well one of the schemes to power
the cable climber, uses ground based lasers to power it.

Just sayin'.... :-)

Dave

PS: On a serious note, doesn't look to me where the proposed ground site
would be, right along the equator and possibly out at sea to the west of
South America, near the Galapagos Islands, is a highly traversed area of
air transit. Obviously this would need to be an air travel exclusion
zone. But there is also terrorism to consider...

Hurricanes, tornadoes, etc.

Plus someone else mentioned satellites

On 2020-06-11 8:06 PM, Alain Fournier wrote:

I think that what happens above geostationary altitude on an elevator
is often overlooked. People talk about putting a counter weight to
keep the cable taught. I think you want to have 30,000 km of cable
above geostationary altitude and you don't need to put a big massive
object at the end of those 30,000 km. What you put at the end of the
cable is another cable, this one spinning. All those cables are your
counter weight, but you can also use them to go away in the solar
system. Just going to 30,000 km above geostationary gives you enough
angular momentum to escape Earth. The spinning cable gives you more
umpf, but it also lets you go outside of Earth's equatorial plane.


I forgot to mention also that once you are past geostationary altitude,
you no longer have to figure out how to power your cabin. The cabin is
pulled out by the centrifugal force. Now you have to figure out what you
are going to do with the electricity you generate while controlling your
speed and/or slowing down. So using the cable after geostationary
altitude to go out in the solar system is really a free ride.

Both of these ideas are interesting potentials of the technology I
hadn't thought of. Cool ideas.

Now if we had say about 3 of these, equidistant around the equator,
acting like giant 'cell telephone' towers, perhaps we could replace LEO
satellite clusters altogether, which seems from today's perspective one
of the two the biggest inhibitors to this technology. The other being
the still unsolved materials problem of constructing the appropriate cable.

So in the end, it looks like rockets and satellites win, because
technology enabled them first.

Dave

In article ,
says...

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.

Post 9/11 I agree that this is something to seriously consider.

Micrometeorite and orbital debris is also a huge concern. It's not like
a space elevator can initiate a collision avoidance maneuver. Better
add clearing out all significant orbital debris to the price tag of your
space elevator.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

In article , says...

On 2020-06-11 7:41 PM, Alain Fournier wrote:
but weren't we already
day dreaming about space elevators?

Yeah until they got bombarded by a Starlink cluster f**k.

oh well.....

Dave

Active satellites aren't an issue. Starlink satellites can maneuver and
should be able to miss the cable every single time (it's not like the
cable is moving, so it's easy enough to do very small maneuvers far
ahead of time).

The far bigger problem is dead satellites, spent stages (e.g. from
direct GEO insertions, like DOD likes to use for some secret squirrel
satellites), and large debris from the same. Much of these dead things
are in orbits that won't decay for hundreds, thousands, or more years.

Starlink satellites at least have the property that they're in a low
orbit and even if one dies and becomes completely uncontrollable, it
will reenter the earth's atmosphere within a few years.

So, by the time you go to actually build a space elevator, you could
have already put in place measures to insure satellites in LEO won't be
a problem. It's those pesky hunks of space junk in much higher orbits
that will be a *very* long term, problem.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

In article ,
says...

On 2020-06-11 20:06, Alain Fournier wrote:

I forgot to mention also that once you are past geostationary altitude,
you no longer have to figure out how to power your cabin. The cabin is
pulled out by the centrifugal force.



An elevator goes up and down.

Say I am 20km below geostationary. so roughly 24 hour orbital period.
I run the engine and move up 20km in one hour.

If I release any brake against the tether, would that put me into an
elliptical orbit and I would be going up/down 20km each 12 hours?

If I hae a brake against the tether, does this mean that I will continue
to exert downward force on it for 12 hours while my orbit is circularized?

So you're saying stay attached to the cable, whose orbital period
doesn't change and doesn't match the orbit you're trying to go in.

Doesn't make any sense. Just release and use rocket propulsion to
circularize your orbit. Besides, you're going to need to get out of the
same plane as the elevator so you don't ever run into it. That means
rocket propulsion anyway.

And more generically speaking: would it be correct to state that force
to accelerate an object horizontally as it climbs the tether would come
from the "centripetal" force of the mass beyond geostationary? ( object
woudl wat to deform tether by moving westward, and counterceight high
above would pull up to straighten the tether, essentially pulling object
eastward).

Actually, it comes from actually slowing down the rotation of of the
earth (a very tiny almost imperceptible bit). From the Wikipedia
article:

The angular momentum is taken from the Earth's rotation. As
the climber ascends, it is initially moving slower than each
successive part of cable it is moving on to. This is the
Coriolis force: the climber "drags" (westward) on the cable,
as it climbs, and slightly decreases the Earth's rotation
speed. The opposite process would occur for descending
payloads: the cable is tilted eastward, thus slightly
increasing Earth's rotation speed.

So not only would such counterweight have to support the weight of the
tether itself, not only would it have to support the weight of an
upcoming elevator and its cargo, but would also be what accerelated that
elevator fhorizontally as it climbs?

I have no idea what you're trying to say here. Read this section:

https://en.wikipedia.org/wiki/Space_elevator#Climbers

Jeff

--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

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
. @ .

"David Spain" wrote in message ...

The 'nail' in the Space Elevator coffin might not have actually ANYTHING to
do with the technical feasibility of building one, but that the environment
that it would operate within has become too hostile!

Scott Kozel posted about the hazards of aircraft hitting the cable, but a
far more likely scenario will be a member of a LEO satellite constellation,
such as Starlink or one of it many competitors that may be launched.

Having an entire constellation of thousands of low Earth orbiting
satellites may very well present too much of a challenge to have one stable
ribbon cable extending vertically across the orbital planes of these
constellations at the Earth's Equator. The orbital pathways of Starlink
look far more like a weave than a circle. Requiring frequent and
potentially costly moves of an Earth-side anchor even if it were designed
to be mobile from the get go. A further design complication. This may
render the entire concept moot. Like setting up a lemonade stand in the
middle of an eight lane superhighway!

I've seen suggestions that issues like this be solved in part by imparting a
"wave" in the cable to move it around as needed.

Considering our extremely limited experience with tethers and the failures
and problems, I suspect this is far from trivial.


So if this ever happens, maybe Moon or Mars will be the first, even if
technically doable on Earth!


There's a couple of other issues that need to be addressed:

Monoatomic Oxygen - Any materials will need to take this into account.

Voltage differentials between orbits.

Dave

--
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 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/