Micro Gravity and A Space Elevator?

On 2020-06-10 2:16 PM, Scott Kozel wrote:

It would be possible for the Moon today, given its much lower gravity. Given
its very slow rotation, a geosynchronous anchor would not work, but they could
use one of the Moon's LaGrange points.


You're thinking a fuel depot? Water pumped up from the surface to the
anchored depot at L1 or L2? Micro-gravity available when docked?

Dave

On Wednesday, June 10, 2020 at 2:28:39 PM UTC-4, David Spain wrote:
On 2020-06-10 2:16 PM, Scott Kozel wrote:

It would be possible for the Moon today, given its much lower gravity. Given
its very slow rotation, a geosynchronous anchor would not work, but they could
use one of the Moon's LaGrange points.

You're thinking a fuel depot? Water pumped up from the surface to the
anchored depot at L1 or L2? Micro-gravity available when docked?

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.

On Jun/10/2020 at 18:35, Scott Kozel wrote :
On Wednesday, June 10, 2020 at 2:28:39 PM UTC-4, David Spain wrote:
On 2020-06-10 2:16 PM, Scott Kozel wrote:

It would be possible for the Moon today, given its much lower gravity. Given
its very slow rotation, a geosynchronous anchor would not work, but they could
use one of the Moon's LaGrange points.

You're thinking a fuel depot? Water pumped up from the surface to the
anchored depot at L1 or L2? Micro-gravity available when docked?

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
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

On 2020-06-10 7:46 PM, Alain Fournier wrote:

An Earth space elevator is technologically feasible with today's
material. See for instance
space.nss.org/wp-content/uploads/2000-Space-Elevator-NIAC-phase1.pdf

Interesting, will take a look, thanks. Reformatted for one-click...

https://space.nss.org/wp-content/upl...IAC-phase1.pdf

Dave

On 2020-06-11 1:44 PM, David Spain wrote:
On 2020-06-10 7:46 PM, Alain Fournier wrote:

An Earth space elevator is technologically feasible with today's
material. See for instance
http://space.nss.org/wp-content/uplo...IAC-phase1.pdf

OK I've read through Chapter 2. There are a lot of if's here. I would
judge this as written as currently feasible without further study. The
good news is that at the time of writing of this paper in 2000 where
lengths of carbon nanotubes were only in a few centimeters, such results
have been subsumed by newer research ([1], 2013) that have produced a
length of 50 centimeters. So work is progressing, but to say it's
feasible is still a "stretch", pun intended.

There have been more recent papers published on the NSS website he

https://space.nss.org/space-elevator-library/

I'll have to take a look and see what progress has been made since 2000.
The 2000 Edwards paper shows promise and consideration but in and of
itself is not convincing.

Also I take some issue with the need to use a ground laser / climber
solar arrays to power climbers if the cable itself has unique electrical
conductivity. Save some effort here?

Dave

[1] https://pubs.acs.org/doi/10.1021/nn401995z

On 2020-06-11 2:25 PM, David Spain wrote:
There are a lot of if's here. I would
judge this as written as [not] currently feasible without further study.
Sorry bad typo.

Dave

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!

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

Dave

"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/

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 :
On Wednesday, June 10, 2020 at 2:28:39 PM UTC-4, David Spain wrote:
On 2020-06-10 2:16 PM, Scott Kozel wrote:

It would be possible for the Moon today, given its much lower
gravity.Â* Given
its very slow rotation, a geosynchronous anchor would not work, but
they could
use one of the Moon's LaGrange points.

You're thinking a fuel depot? Water pumped up from the surface to the
anchored depot at L1 or L2? Micro-gravity available when docked?

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

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?