Discussion:
Space Elevators Soon?
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Quadibloc
2021-09-12 02:39:47 UTC
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I came across this video on YouTube



which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.

However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.

John Savard
Lynn McGuire
2021-09-12 03:19:34 UTC
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Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
John Savard
The tallest building in the planet is the 828-metre (2,717 ft) tall Burj
Khalifa in Dubai.
https://en.wikipedia.org/wiki/List_of_tallest_buildings

We need a lot more experience with tall buildings before building a
space elevator. Just building the space elevator structure will be
difficult. Then adding the elevators will be tricky as air and power
will be needed. Probably toilet facilities too as the elevator will
take hours ??? to get to LEO ? And part of that trip will be at zero
gravity.

Doesn't one space elevator design have an asteroid maneuvered into place
in GEO with the elevator suspended from it ?

Lynn
J. Clarke
2021-09-12 03:49:48 UTC
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On Sat, 11 Sep 2021 22:19:34 -0500, Lynn McGuire
Post by Lynn McGuire
Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
John Savard
The tallest building in the planet is the 828-metre (2,717 ft) tall Burj
Khalifa in Dubai.
https://en.wikipedia.org/wiki/List_of_tallest_buildings
We need a lot more experience with tall buildings before building a
space elevator. Just building the space elevator structure will be
difficult. Then adding the elevators will be tricky as air and power
will be needed. Probably toilet facilities too as the elevator will
take hours ??? to get to LEO ? And part of that trip will be at zero
gravity.
Doesn't one space elevator design have an asteroid maneuvered into place
in GEO with the elevator suspended from it ?
A space elevator will not be a "structure" in the conventional
sense--it will be loaded in tension.

A space elevator to LEO is not a reasonable configuration--it has to
go to GEO to have any real utility. And any space elevator will have
a counterweight.
Quadibloc
2021-09-12 04:38:32 UTC
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Of course, my point was that slightly stronger concrete with microscopic
particles of graphene in it...

is not enough to take the space elevator out of the realm of science
fiction.

Whether composites with a strength approaching that of graphene will
be available in decades or centuries, I can't guess.

But something more modest would be some way to accelerate a
spaceship to a high velocity without the use of reaction mass to be
carried along with it - the magnetic railgun. That might be practical on
the Moon, but it would be difficult on Earth. But it would still be orders
of magnitude easier than a space elevator.

So I did some looking around. It turns out that there are some mountains
in the Alleghenies that are over 6,000 feet high - more than a mile.

Oops. The troposphere is *five* miles high. While Mount Everest isn't in
the United States, there are some mountains 24,000 miles high in the
U.S., but none of them are anywhere near the southern part of the Eastern
seaboard - one wants to launch rockets from somewhere southerly,
not to waste energy correcting their orbits, and so that they can head
eastward and fly over the ocean for the risky first part of their flights.

I mean, there's a reason they chose Cape Canaveral.

Hawai'i has Mauna Kea, but there's enough controversy over just
having telescopes on top of it. And the islands are too small to support all the
infrastructure for building the rockets *there*, so one has to ship them by sea.

Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.

John Savard
Quadibloc
2021-09-12 04:41:26 UTC
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Post by Quadibloc
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
Cerro de Punta in Puerto Rico, and Crown Mountain in the U.S. Virgin Islands
definitely don't cut it, so there don't seem to be any options there...

John Savard
Quadibloc
2021-09-12 04:55:10 UTC
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Post by Quadibloc
Post by Quadibloc
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
Cerro de Punta in Puerto Rico, and Crown Mountain in the U.S. Virgin Islands
definitely don't cut it, so there don't seem to be any options there...
In Jules Verne's "From the Earth to the Moon", Texas was considered as a
possible launch site. It has a coast that has the Carribean to the East.

But the tallest mountain in Texas is only some 8,000-odd feet high, and it
isn't anywhere near the coast, being on the other side of the state. Mexico
has mountains closer to its Eastern coast, but that hardly helps.

John Savard
Michael F. Stemper
2021-09-12 20:26:25 UTC
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Post by Quadibloc
Post by Quadibloc
Post by Quadibloc
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
Cerro de Punta in Puerto Rico, and Crown Mountain in the U.S. Virgin Islands
definitely don't cut it, so there don't seem to be any options there...
In Jules Verne's "From the Earth to the Moon", Texas was considered as a
possible launch site. It has a coast that has the Carribean to the East.
But the tallest mountain in Texas is only some 8,000-odd feet high, and it
isn't anywhere near the coast, being on the other side of the state. Mexico
has mountains closer to its Eastern coast, but that hardly helps.
Heinlein's novella "The Man Who Sold the Moon" goes through a bunch of
issues like these involved in selecting a launch site. It's a good
story, too.
--
Michael F. Stemper
Psalm 82:3-4
Andrew McDowell
2021-09-12 04:43:52 UTC
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Post by Quadibloc
Of course, my point was that slightly stronger concrete with microscopic
particles of graphene in it...
is not enough to take the space elevator out of the realm of science
fiction.
Whether composites with a strength approaching that of graphene will
be available in decades or centuries, I can't guess.
But something more modest would be some way to accelerate a
spaceship to a high velocity without the use of reaction mass to be
carried along with it - the magnetic railgun. That might be practical on
the Moon, but it would be difficult on Earth. But it would still be orders
of magnitude easier than a space elevator.
So I did some looking around. It turns out that there are some mountains
in the Alleghenies that are over 6,000 feet high - more than a mile.
Oops. The troposphere is *five* miles high. While Mount Everest isn't in
the United States, there are some mountains 24,000 miles high in the
U.S., but none of them are anywhere near the southern part of the Eastern
seaboard - one wants to launch rockets from somewhere southerly,
not to waste energy correcting their orbits, and so that they can head
eastward and fly over the ocean for the risky first part of their flights.
I mean, there's a reason they chose Cape Canaveral.
Hawai'i has Mauna Kea, but there's enough controversy over just
having telescopes on top of it. And the islands are too small to support all the
infrastructure for building the rockets *there*, so one has to ship them by sea.
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
John Savard
https://en.wikipedia.org/wiki/Lunar_space_elevator
J. Clarke
2021-09-12 07:53:17 UTC
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On Sat, 11 Sep 2021 21:38:32 -0700 (PDT), Quadibloc
Post by Quadibloc
Of course, my point was that slightly stronger concrete with microscopic
particles of graphene in it...
is not enough to take the space elevator out of the realm of science
fiction.
Whether composites with a strength approaching that of graphene will
be available in decades or centuries, I can't guess.
But something more modest would be some way to accelerate a
spaceship to a high velocity without the use of reaction mass to be
carried along with it - the magnetic railgun. That might be practical on
the Moon, but it would be difficult on Earth. But it would still be orders
of magnitude easier than a space elevator.
So I did some looking around. It turns out that there are some mountains
in the Alleghenies that are over 6,000 feet high - more than a mile.
Oops. The troposphere is *five* miles high. While Mount Everest isn't in
the United States, there are some mountains 24,000 miles high in the
U.S., but none of them are anywhere near the southern part of the Eastern
seaboard - one wants to launch rockets from somewhere southerly,
not to waste energy correcting their orbits, and so that they can head
eastward and fly over the ocean for the risky first part of their flights.
I mean, there's a reason they chose Cape Canaveral.
Hawai'i has Mauna Kea, but there's enough controversy over just
having telescopes on top of it. And the islands are too small to support all the
infrastructure for building the rockets *there*, so one has to ship them by sea.
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
Try Huascaran in Peru, 9? degrees 7'S, 22,205 ft.

However you're still going to have a tremendous lot of atmosphere to
punch through, and you're going to be sending massive shockwaves
across about 3000 miles of South America.
Michael Dworetsky
2021-09-12 08:44:17 UTC
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Post by Quadibloc
Of course, my point was that slightly stronger concrete with microscopic
particles of graphene in it...
is not enough to take the space elevator out of the realm of science
fiction.
Whether composites with a strength approaching that of graphene will
be available in decades or centuries, I can't guess.
But something more modest would be some way to accelerate a
spaceship to a high velocity without the use of reaction mass to be
carried along with it - the magnetic railgun. That might be practical on
the Moon, but it would be difficult on Earth. But it would still be orders
of magnitude easier than a space elevator.
So I did some looking around. It turns out that there are some mountains
in the Alleghenies that are over 6,000 feet high - more than a mile.
Oops. The troposphere is *five* miles high. While Mount Everest isn't in
the United States, there are some mountains 24,000 miles high in the
U.S., but none of them are anywhere near the southern part of the Eastern
seaboard - one wants to launch rockets from somewhere southerly,
not to waste energy correcting their orbits, and so that they can head
eastward and fly over the ocean for the risky first part of their flights.
The magnetic rail gun concept was a key plot element in Heinlein's "The
Moon Is a Harsh Mistress". The problem is that in an Earth launch,
doing all the acceleration at a relatively low altitude over a short
distance generates very high g-forces, so it isn't practical for human
spaceflight. Fine for cargo that can be constructed to survive the
launch. Avoiding the upwards "meteor effect" at escape velocity is
another severe problem, far worse than a capsule or shuttle re-entry.

In the novel, the issue was water, and the idea was to use a gun to
launch containers of water to Luna where the ingenious farmers could use
it to grow grain crops that feed Earth.
Post by Quadibloc
I mean, there's a reason they chose Cape Canaveral.
The ESA site in French Guiana is almost right on the equator. Being
near the equator is ideal for launches into synchronous orbits or flight
paths near the ecliptic plane. Not so good for the ISS which has a high
orbital inclination, but feasible.
Post by Quadibloc
Hawai'i has Mauna Kea, but there's enough controversy over just
having telescopes on top of it. And the islands are too small to support all the
infrastructure for building the rockets *there*, so one has to ship them by sea.
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
John Savard
--
Mike Dworetsky
J. Clarke
2021-09-12 16:30:15 UTC
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On Sun, 12 Sep 2021 09:44:17 +0100, Michael Dworetsky
Post by Michael Dworetsky
Post by Quadibloc
Of course, my point was that slightly stronger concrete with microscopic
particles of graphene in it...
is not enough to take the space elevator out of the realm of science
fiction.
Whether composites with a strength approaching that of graphene will
be available in decades or centuries, I can't guess.
But something more modest would be some way to accelerate a
spaceship to a high velocity without the use of reaction mass to be
carried along with it - the magnetic railgun. That might be practical on
the Moon, but it would be difficult on Earth. But it would still be orders
of magnitude easier than a space elevator.
So I did some looking around. It turns out that there are some mountains
in the Alleghenies that are over 6,000 feet high - more than a mile.
Oops. The troposphere is *five* miles high. While Mount Everest isn't in
the United States, there are some mountains 24,000 miles high in the
U.S., but none of them are anywhere near the southern part of the Eastern
seaboard - one wants to launch rockets from somewhere southerly,
not to waste energy correcting their orbits, and so that they can head
eastward and fly over the ocean for the risky first part of their flights.
The magnetic rail gun concept was a key plot element in Heinlein's "The
Moon Is a Harsh Mistress". The problem is that in an Earth launch,
doing all the acceleration at a relatively low altitude over a short
distance generates very high g-forces, so it isn't practical for human
spaceflight. Fine for cargo that can be constructed to survive the
launch. Avoiding the upwards "meteor effect" at escape velocity is
another severe problem, far worse than a capsule or shuttle re-entry.
Also once it leaves the launcher, it's going to be getting massive
G-forces in the other direction due to drag as it passes through the
atmosphere.
Post by Michael Dworetsky
In the novel, the issue was water, and the idea was to use a gun to
launch containers of water to Luna where the ingenious farmers could use
it to grow grain crops that feed Earth.
Post by Quadibloc
I mean, there's a reason they chose Cape Canaveral.
The ESA site in French Guiana is almost right on the equator. Being
near the equator is ideal for launches into synchronous orbits or flight
paths near the ecliptic plane. Not so good for the ISS which has a high
orbital inclination, but feasible.
Post by Quadibloc
Hawai'i has Mauna Kea, but there's enough controversy over just
having telescopes on top of it. And the islands are too small to support all the
infrastructure for building the rockets *there*, so one has to ship them by sea.
Hmm. Well, I've only started looking, perhaps there are possible sites I'm
overlooking.
John Savard
Hamish Laws
2021-09-12 09:49:21 UTC
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there are some mountains 24,000 miles high in the U.S.
Impressive.
Dimensional Traveler
2021-09-12 15:41:58 UTC
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Post by Hamish Laws
there are some mountains 24,000 miles high in the U.S.
Impressive.
One assumes you are referring to the 24,000 miles of idiocy there....
--
I've done good in this world. Now I'm tired and just want to be a cranky
dirty old man.
Ninapenda Jibini
2021-09-12 15:45:52 UTC
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Post by Dimensional Traveler
On Sunday, September 12, 2021 at 2:38:34 PM UTC+10, Quadibloc
there are some mountains 24,000 miles high in the U.S.
Impressive.
One assumes you are referring to the 24,000 miles of idiocy
there....
This *is* Quaddie we're talking about.
--
Terry Austin

Proof that Alan Baker is a liar and a fool, and even stupider than
Lynn:
https://www.cbp.gov/newsroom/stats/sw-border-migration


"Terry Austin: like the polio vaccine, only with more asshole."
-- David Bilek

Jesus forgives sinners, not criminals.
Quadibloc
2021-09-12 16:49:51 UTC
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Post by Hamish Laws
there are some mountains 24,000 miles high in the U.S.
Impressive.
Oops, typo. I meant feet. However, apparently 14,000 feet is more like it.

John Savard
Robert Woodward
2021-09-12 17:02:19 UTC
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Post by Quadibloc
Post by Hamish Laws
there are some mountains 24,000 miles high in the U.S.
Impressive.
Oops, typo. I meant feet. However, apparently 14,000 feet is more like it.
For values of 1 mountain at 20130 feet.
--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_.
—-----------------------------------------------------
Robert Woodward ***@drizzle.com
Lynn McGuire
2021-09-13 00:00:18 UTC
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Post by Quadibloc
Post by Hamish Laws
there are some mountains 24,000 miles high in the U.S.
Impressive.
Oops, typo. I meant feet. However, apparently 14,000 feet is more like it.
John Savard
Even Pike's Peak is taller than 14,000 feet at 14,115 feet. I drove my
truck to the top of it back in 2001.
https://en.wikipedia.org/wiki/Pikes_Peak

There are 96 mountains higher than 14,000 ft in the USA, 64 of them
higher than Pike's Peak.
https://en.wikipedia.org/wiki/Fourteener

Lynn
Torbjorn Lindgren
2021-09-12 21:16:20 UTC
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Post by Quadibloc
Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce
graphene at such a cost, and in such sizes, so that it can be used in
building construction.
Post by Quadibloc
However, it isn't until 2:52 that they get to the point; what this is
about is about concrete that is 30% stronger because some graphene has
been mixed in. So that isn't quite close to the theoretical strength of
pure graphene on a large scale.
For a Space Elevator and high skyscrapes the relevant figure is AFAIK
how strong it is in compression. They seem to only talk about tensile
strength which is rarely the limiting factor issue for these kind of
constructions which makes the cynic in me think there's little or no
improvement on that aspect or they would have mentioned it given that
it's basically a SALES PITCH.

Increasing the tensile strength does help with some thing though IF my
understand is right that's mostly in reducing or eliminating the need
for rebar (steel) reinforcement. Which is valuable because usually
most of the time is spent on that and time is money but is less
helpful for this.

They do mention reduced cracking which CAN help these kind of projects
but given that it's a sales pitch I wouldn't trust that it's better at
that than various already existing advanced concrete formulations.
Post by Quadibloc
We need a lot more experience with tall buildings before building a
space elevator. Just building the space elevator structure will be
difficult. Then adding the elevators will be tricky as air and power
will be needed. Probably toilet facilities too as the elevator will
take hours ??? to get to LEO ? And part of that trip will be at zero
gravity.
Doesn't one space elevator design have an asteroid maneuvered into place
in GEO with the elevator suspended from it ?
No, for a Space Elevator the "mid-point" is at GEO or corresponding
(stationary) altitude for other planets/moons, with the counterweight
much further out (you can balance weight vs how much further out).

Going further out with the counterweight increases the speed boost the
Space Elevator can provide by "flinging" crafts! If you extend the
outer structure far enough out it IS the counterweight but it would
need to be very long, it's hard to imagine a case where they don't end
up with a substantial counterweight part added at the end.

Any kind of non-magic-tech (IE not scrith) Space Elevator on Earth
will use significant taper, IE it's much thicker/heavier far away from
the mid-point to reduce the material strength requirement.

I don't think we've reached the point where we can build one for Earth
yet, but one on the moon is relatively easy but still require taper
and IIRC Mars is doable but require significant larger but doable
taper.

However, we CAN build a Space Fountain[1] *TODAY*, complete plans for
one were drawn up back in the early to mid 1990's and it would be
significantly cheaper to do today due to much better power handling
electronics and better magnets.

A Space Fountain is an example of a dynamic structure, thus it's
sufficient that it gets up above the atmosphere though higher has some
benefits (but also costs more).

The dynamic nature worries some which is why the plan that was drawn
up used multiple redundant "stream pairs" and was able to handle
complete power loss (it would gradually contract down to a stable
state). It doesn't need to be on or near the equator either, though it
does get more useful (lower extra delta-V required) if it is.

It's still vulnerable to sabotage/terrorism but that's just as much
the case for Space Elevators too, and they would make a MUCH bigger
mess on Earth if that happens.

For more information I can recommend the relevant chapter in Robert L.
Forward's _Indistinguishable From Magic_, and if you want more he
provides several references. The entire book is well worth reading.

Skyhooks, Rotovators and Bolos[2] are also possible for Earth already
but for Earth they all require something else to get up above almost
all of the atmosphere. On the moon OTOH they could be really useful as
is.

The delivery to these on Earth could in theory be some kind of
sub-orbital craft but my feeling is that these consctructs probably
only make sense for Earth if you've first built one or more Space
Fountain (to 70-100km) and launch so much that you want to reduce
launch costs even further.


1. https://en.wikipedia.org/wiki/Space_fountain
2. https://en.wikipedia.org/wiki/Non-rocket_spacelaunch
J. Clarke
2021-09-12 21:34:56 UTC
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On Sun, 12 Sep 2021 21:16:20 -0000 (UTC), Torbjorn Lindgren
Post by Torbjorn Lindgren
Post by Quadibloc
Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce
graphene at such a cost, and in such sizes, so that it can be used in
building construction.
Post by Quadibloc
However, it isn't until 2:52 that they get to the point; what this is
about is about concrete that is 30% stronger because some graphene has
been mixed in. So that isn't quite close to the theoretical strength of
pure graphene on a large scale.
For a Space Elevator and high skyscrapes the relevant figure is AFAIK
how strong it is in compression. They seem to only talk about tensile
strength which is rarely the limiting factor issue for these kind of
constructions which makes the cynic in me think there's little or no
improvement on that aspect or they would have mentioned it given that
it's basically a SALES PITCH.
A space elevator is not some kind of superior skyscraper. It is in
essence a rope in geostationary orbit that is long enough to extend to
the surface. Compressive strength is of little importance, it's all
loaded in tension.
Post by Torbjorn Lindgren
Increasing the tensile strength does help with some thing though IF my
understand is right that's mostly in reducing or eliminating the need
for rebar (steel) reinforcement. Which is valuable because usually
most of the time is spent on that and time is money but is less
helpful for this.
They do mention reduced cracking which CAN help these kind of projects
but given that it's a sales pitch I wouldn't trust that it's better at
that than various already existing advanced concrete formulations.
Rebar rusts. Does graphene? That alone could be a major improvement.
Post by Torbjorn Lindgren
Post by Quadibloc
We need a lot more experience with tall buildings before building a
space elevator. Just building the space elevator structure will be
difficult. Then adding the elevators will be tricky as air and power
will be needed. Probably toilet facilities too as the elevator will
take hours ??? to get to LEO ? And part of that trip will be at zero
gravity.
Doesn't one space elevator design have an asteroid maneuvered into place
in GEO with the elevator suspended from it ?
No, for a Space Elevator the "mid-point" is at GEO or corresponding
(stationary) altitude for other planets/moons, with the counterweight
much further out (you can balance weight vs how much further out).
Going further out with the counterweight increases the speed boost the
Space Elevator can provide by "flinging" crafts! If you extend the
outer structure far enough out it IS the counterweight but it would
need to be very long, it's hard to imagine a case where they don't end
up with a substantial counterweight part added at the end.
Any kind of non-magic-tech (IE not scrith) Space Elevator on Earth
will use significant taper, IE it's much thicker/heavier far away from
the mid-point to reduce the material strength requirement.
It would be heaviest at the mid point--that's where the highest load
would be.
Post by Torbjorn Lindgren
I don't think we've reached the point where we can build one for Earth
yet, but one on the moon is relatively easy but still require taper
and IIRC Mars is doable but require significant larger but doable
taper.
However, we CAN build a Space Fountain[1] *TODAY*, complete plans for
one were drawn up back in the early to mid 1990's and it would be
significantly cheaper to do today due to much better power handling
electronics and better magnets.
A Space Fountain is an example of a dynamic structure, thus it's
sufficient that it gets up above the atmosphere though higher has some
benefits (but also costs more).
The dynamic nature worries some which is why the plan that was drawn
up used multiple redundant "stream pairs" and was able to handle
complete power loss (it would gradually contract down to a stable
state). It doesn't need to be on or near the equator either, though it
does get more useful (lower extra delta-V required) if it is.
It's still vulnerable to sabotage/terrorism but that's just as much
the case for Space Elevators too, and they would make a MUCH bigger
mess on Earth if that happens.
For more information I can recommend the relevant chapter in Robert L.
Forward's _Indistinguishable From Magic_, and if you want more he
provides several references. The entire book is well worth reading.
Skyhooks, Rotovators and Bolos[2] are also possible for Earth already
but for Earth they all require something else to get up above almost
all of the atmosphere. On the moon OTOH they could be really useful as
is.
The delivery to these on Earth could in theory be some kind of
sub-orbital craft but my feeling is that these consctructs probably
only make sense for Earth if you've first built one or more Space
Fountain (to 70-100km) and launch so much that you want to reduce
launch costs even further.
1. https://en.wikipedia.org/wiki/Space_fountain
2. https://en.wikipedia.org/wiki/Non-rocket_spacelaunch
Quadibloc
2021-09-13 01:45:06 UTC
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Permalink
Rebar rusts. Does graphene? That alone could be a major improvement.
Yes. Microscopic graphene particles embedded in cement will likely not
have oxidation issues. But graphene being a form of carbon, it can
oxidize. But I suspect that unlike in the case of rebar, it will be quite
possible to ensure that won't mean anything.

John Savard
Kade Green
2021-09-12 22:39:24 UTC
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Permalink
Post by Torbjorn Lindgren
For a Space Elevator and high skyscrapes the relevant figure
is AFAIKhow strong it is in compression. They seem to only talk
about tensile strength which is rarely the limiting factor...
for a Space Elevator the "mid-point" is at GEO or corresponding
(stationary) altitude for other planets/moons, with the counterweight
much further out (you can balance weight vs how much further out).
Think about that for a minute and you'll see that a space elevator isn't
a tower holding itself up from the ground by compression, it's a cable
lowered down from geosynchronous orbit, hence the center of mass at GEO.
The ground connection isn't holding the cable /up/, it's holding the end
/down/ at a particular place.
Quadibloc
2021-09-13 01:41:59 UTC
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Post by Torbjorn Lindgren
For a Space Elevator and high skyscrapes the relevant figure is AFAIK
how strong it is in compression.
A space elevator is intended to be a tether to an object beyond geosynchronous
orbit, so it is in tension.

Tall buildings _were_ primarily dependent on compression strength, but today's
really tall buildings use the tensile strength of materials a lot, as the techniques
of traditional construction, that worked with materials with basically no
tensile strength, and only compressive strength, are not equal to the task.

With compressive strength, one is talking about the Pyramids, the arch, and
the dome.

John Savard
Lynn McGuire
2021-09-12 04:15:54 UTC
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Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
John Savard
https://en.wikipedia.org/wiki/Space_elevator

Goes to GEO and beyond.

Lynn
Hamish Laws
2021-09-12 09:48:27 UTC
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Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
and concrete's strength is normally much higher in compression than tension, so it's not really usable for this
Paul S Person
2021-09-13 15:47:05 UTC
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On Sat, 11 Sep 2021 19:39:47 -0700 (PDT), Quadibloc
Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
As a result of reading this thread, I've become reasonably sure that
the possibility of using nanocarbon tubes (which may be included in
"graphene") for a space elevator was mentioned provided they could be
made into long enough cables several years (possibly two decades) ago.

The engineering is, of course, the problem.

And, surprisingly for an SF group whose members have surely read AC
Clark, who invented and described the thing and located one in Ceylon
(now Sri Lanka), a lot of people here seem unfamiliar with the
concept, confusing it with a veritable Tower of Babel reaching, if not
the Heaven, at least to a geosynchronous orbit.
--
"I begin to envy Petronius."
"I have envied him long since."
pete...@gmail.com
2021-09-14 01:10:30 UTC
Reply
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Post by Paul S Person
On Sat, 11 Sep 2021 19:39:47 -0700 (PDT), Quadibloc
Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
As a result of reading this thread, I've become reasonably sure that
the possibility of using nanocarbon tubes (which may be included in
"graphene") for a space elevator was mentioned provided they could be
made into long enough cables several years (possibly two decades) ago.
The engineering is, of course, the problem.
And, surprisingly for an SF group whose members have surely read AC
Clark, who invented and described the thing and located one in Ceylon
(now Sri Lanka), a lot of people here seem unfamiliar with the
concept, confusing it with a veritable Tower of Babel reaching, if not
the Heaven, at least to a geosynchronous orbit.
It predates Clarke. Tsiolkovsky first considered a tower to geosynchronous
orbit an 1895, and in 1959 the tension version was described by Yuri N. Artsutano.

When the book came out, I described the concept to my father, who happened
to in charge of advertising Kevlar for DuPont in Europe, Kevlar being the
strongest commercially available fiber at the time.

He managed to swing a meeting with Clarke on that basis. Little came of it,
but I did get a signed and inscribed hardback of the book.

Pt
Robert Carnegie
2021-09-14 01:41:18 UTC
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Post by ***@gmail.com
Post by Paul S Person
On Sat, 11 Sep 2021 19:39:47 -0700 (PDT), Quadibloc
Post by Quadibloc
I came across this video on YouTube
http://youtu.be/n82_NsFjj_8
which appears to claim that it has become practical to produce graphene at such a cost, and in such sizes, so that it can be used in building construction.
However, it isn't until 2:52 that they get to the point; what this is about is about concrete that is 30% stronger because some graphene has been mixed in. So that isn't quite close to the theoretical strength of pure graphene on a large scale.
As a result of reading this thread, I've become reasonably sure that
the possibility of using nanocarbon tubes (which may be included in
"graphene") for a space elevator was mentioned provided they could be
made into long enough cables several years (possibly two decades) ago.
The engineering is, of course, the problem.
And, surprisingly for an SF group whose members have surely read AC
Clark, who invented and described the thing and located one in Ceylon
(now Sri Lanka), a lot of people here seem unfamiliar with the
concept, confusing it with a veritable Tower of Babel reaching, if not
the Heaven, at least to a geosynchronous orbit.
It predates Clarke. Tsiolkovsky first considered a tower to geosynchronous
orbit an 1895, and in 1959 the tension version was described by Yuri N. Artsutano.
When the book came out, I described the concept to my father, who happened
to in charge of advertising Kevlar for DuPont in Europe, Kevlar being the
strongest commercially available fiber at the time.
He managed to swing a meeting with Clarke on that basis. Little came of it,
but I did get a signed and inscribed hardback of the book.
Clarke seemed good humoured about not personally
making billions of dollars from placing broadcast satellites
in geostationary orbit, but he wouldn't want to miss out twice.
But he acknowledged the prior art in an afterword.

I think in the book, the setting was still a bit in the future from
now - the architect built the Gibraltar Bridge, which we still
await - proposed carbon monofilament and/or solid diamond
as the stuff to make the thing, and indeed it was to float
in space and to be tethered to the ground.
danny burstein
2021-09-14 01:54:49 UTC
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In <a406d3c7-d79c-40da-ab1a-***@googlegroups.com> "***@gmail.com" <***@gmail.com> writes:
[snip]
Post by ***@gmail.com
When the book came out, I described the concept to my father, who happened
to in charge of advertising Kevlar for DuPont in Europe, Kevlar being the
strongest commercially available fiber at the time.
He managed to swing a meeting with Clarke on that basis. Little came of it,
but I did get a signed and inscribed hardback of the book.
*jealous* !!
--
_____________________________________________________
Knowledge may be power, but communications is the key
***@panix.com
[to foil spammers, my address has been double rot-13 encoded]
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