> Boyancy is entirely useless. That would be like using helium to help
> fly an airplane.

If there was room on an airplane then buoyancy would help.

In the real thing, the section of the tether that is close to the
hub, gravity will be the predominate force. Aerodynamic and
centrifugal forces will be small. I believe this is where buoyancy
will help the most. In sections where aerodynamic forces become more
significant then cross section geometry of the foil becomes more
important, and aerodynamic lift can be used to overcome gravity, and
using buoyancy may not be practical.

> Not really. Stiffness is not needed, we are talking pure tension. A
> structure of this size held straight by stiffness would be
> completely infeasible. We are pulling a string at both ends.
> Inside, it is the driving force, outside, it is the centrifugal
> force. In between, the
> string sags a little bit to support the drag. The leverage is
> dictated by the requirement that the tip must not point forward
> despite the sag.
>
Stiffness may not be required, but for the optimum design some form
of stiffness may be needed. I think of the problem like a suspension
bridge lay on its side. One can use one massive tower, but that will
require the cable to handle greater tensional loads, therefore more
materiel for the cable. On the other hand multiple shorter towers
will spread out the load, but at the cost of more towers. It could be
that some combination of towers and designing stiffness in to the
cables may be the best design, while requiring minimumal mass. Also
there may be issues with stability that require addition stiffness.

In short all solutions should be considered in the concept. Most
workable designs include a lot of "features" that may not be an
elegant solution, but are required. Look at the aerodynamic devices
on an aircraft: Slats, Flaps, Speed Brakes, Trim Tabs, and so on. The
ideal design would be a deformable wing, but that is not considered
practical.

Bert

--- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@...>
wrote:
>
>
> > Boyancy is entirely useless. That would be like using helium to help
> > fly an airplane.
>
> If there was room on an airplane then buoyancy would help.
>
> In the real thing, the section of the tether that is close to the
> hub, gravity will be the predominate force. Aerodynamic and
> centrifugal forces will be small.

No, the dominant force is tension, and together with the lift further
out keeping the tether up will be no problem at all.

At any speed the dynamic lift of an airfoil is much stronger than any
buoyancy that the same volume could possibly have. Any speed, that is,
down to below walking speed, I would estimate.

Andreas

--- In space-elevator@yahoogroups.com, "Andreas" <awnd329@...> wrote:
>
> --- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@>
> wrote:
> >
> >
> > > Boyancy is entirely useless. That would be like using helium to
help
> > > fly an airplane.
> >
> > If there was room on an airplane then buoyancy would help.
> >
> > In the real thing, the section of the tether that is close to the
> > hub, gravity will be the predominate force. Aerodynamic and
> > centrifugal forces will be small.
>
> No, the dominant force is tension, and together with the lift
further
> out keeping the tether up will be no problem at all.
>
> At any speed the dynamic lift of an airfoil is much stronger than
any
> buoyancy that the same volume could possibly have. Any speed, that
is,
> down to below walking speed, I would estimate.
>
> Andreas
>
OK

--- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@...>
wrote:
>
> This is definitely in the "Mad Englishman Category"
>
> 1. Modify an electric RC model plane by:
>      Remove battery
>      Add hobby pulsejet including fuel supply
>      Add spool mechanism for small gauge carbon fiber ( A mile or
>      two in length will do)
>      Attach the plane to a heavier tether. Bundled with tether
>      would be power cord for plane.
>      Attach other end of heavy tether to post
> 2. Launch plane with electric motor
> 3. Fly plane to end of tether, and start pulse jet
> 4. Release and spool out carbon fiber via RC controller
> 5. Duck !!!!!!!!
>
> Hobby Ramjet
> http://www.windspire.com/daemon/
>
>
> What would this prove? That you are probably MAD
>
> Bert
>
Correction Gas powered Large scale RC Plane
http://www.giantscaleplanes.com/Giles3D-49.htm

In a message dated 6/1/2006 12:48:45 P.M. Central Daylight Time,
awnd329@... writes:

At any  speed the dynamic lift of an airfoil is much stronger than any
buoyancy  that the same volume could possibly have. Any speed, that is,
down to below  walking speed, I would estimate.

Andreas



What airfoil works below 3 mph?


[Non-text portions of this message have been removed]

Maybe, but it would have to be kite. I wonder what happens if you
have tailwind?

Bert

--- In space-elevator@yahoogroups.com, GEddieA95@... wrote:
>
>
> In a message dated 6/1/2006 12:48:45 P.M. Central Daylight Time,
> awnd329@... writes:
>
> At any  speed the dynamic lift of an airfoil is much stronger than
any
> buoyancy  that the same volume could possibly have. Any speed, that
is,
> down to below  walking speed, I would estimate.
>
> Andreas
>
>
>
> What airfoil works below 3 mph?
>
>
> [Non-text portions of this message have been removed]
>

--- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@...>
wrote:
>
> --- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@>
> wrote:
> >
> > This is definitely in the "Mad Englishman Category"
> >
> > 1. Modify an electric RC model plane by:
> >      Remove battery
> >      Add hobby pulsejet including fuel supply
> >      Add spool mechanism for small gauge carbon fiber ( A mile or
> >      two in length will do)
> >      Attach the plane to a heavier tether. Bundled with tether
> >      would be power cord for plane.
> >      Attach other end of heavy tether to post
> > 2. Launch plane with electric motor
> > 3. Fly plane to end of tether, and start pulse jet
> > 4. Release and spool out carbon fiber via RC controller
> > 5. Duck !!!!!!!!
> >
> > Hobby Ramjet
> > http://www.windspire.com/daemon/
> >
> >
> > What would this prove? That you are probably MAD
> >
> > Bert
> >
> Correction Gas powered Large scale RC Plane
> http://www.giantscaleplanes.com/Giles3D-49.htm
>
I have uploaded a file about a model pulse jet plane that can reach
300KM/hr

Bert

Please see: http://www.spaceelevatorblog.com/?p=263

Also NSS SE chapter news feed:
http://seattlewebcrafters.com/nsecc/?q=aggregator/feeds

Enjoy,
Bert

FYI

http://news.bbc.co.uk/1/hi/sci/tech/5012638.stm

It's nice to see that if groups are really interested in doing something, that
they can get together and do it. There are many parrelells between ITER and the
SE, particulerly cost and the fact that location is prestigous in nature. This
raises the odds that it could be completed in my view.

Simon

I haven't gone through the math but this article is along the lines of
concerns
that I've had for a long time, that the nano-tube strength might not be
preserved
when turned into a long cable due to bonding issues.   Is there other
analysis
on this subject or any criticisms?

Dave Forslund
Robert G. Seeberger wrote:
> SCIENCE IN THE NEWS
> from Sigma Xi, The Scientific Research Society
>
> Today's Headlines - May 22, 2006
>
>
> The Space Elevator: Going Down?
> from Nature News
>
> Is it possible to make a cable for a space elevator out of carbon
> nanotubes?
> Not anytime soon, if ever, says Nicola Pugno of the Polytechnic of
> Turin,
> Italy. Pugno's calculations show that inevitable defects in the
> nanotubes
> mean that such a cable simply wouldn't be strong enough.
>
> The idea of a space elevator was popularized in science fiction, where
> writers envisioned a 100,000-kilometre-long cable stretching straight
> up
> from the Earth's surface and fixed in a geosynchronous orbit.
> Payloads, or
> tourists, would simply ascend the cable into low-Earth orbit,
> eliminating
> the need for rocket launches.
>
> When carbon nanotubes were discovered to have an incredibly high
> strength-to-weight ratio, researchers hoped they would take the idea
> out of
> fiction and bring it into reality.
>
> http://www.nature.com/news/2006/060522/full/060522-1.html
> or
> http://tinyurl.com/of4xr
>
>
> xponent
> To Be Disproven Hopefully Maru
> rob
>
>

David Forslund wrote:
> I haven't gone through the math but this article is along the lines of
> concerns
> that I've had for a long time, that the nano-tube strength might not be
> preserved
> when turned into a long cable due to bonding issues.   Is there other
> analysis
> on this subject or any criticisms?
>
> Dave Forslund

Yes.  See Tom Nugent's post on our blog.

http://www.liftport.com/progress/wp/?p=839


--
Brian Dunbar
System Administrator
Liftport - The Space Elevator Company

brian.dunbar@...
aim: bdunbar1967

this email is: [ ] bloggable [x] ask first [ ] private

Remember.
But move forward, too. Light a candle, yes. But also drive a rivet.
~Lileks

Sounds like we really won't know until one builds long cables.  Hopefully
it won't cost too much to find out.

Dave
Brian Dunbar wrote:
> David Forslund wrote:
> > I haven't gone through the math but this article is along the lines of
> > concerns
> > that I've had for a long time, that the nano-tube strength might not be
> > preserved
> > when turned into a long cable due to bonding issues.   Is there other
> > analysis
> > on this subject or any criticisms?
> >
> > Dave Forslund
>
> Yes.  See Tom Nugent's post on our blog.
>
> http://www.liftport.com/progress/wp/?p=839
>
>
> --
> Brian Dunbar
> System Administrator
> Liftport - The Space Elevator Company
>
> brian.dunbar@...
> aim: bdunbar1967
>
> this email is: [ ] bloggable [x] ask first [ ] private
>
> Remember.
> But move forward, too. Light a candle, yes. But also drive a rivet.
> ~Lileks
>
>

buetifull thing about building a material stronger then diamond - even if it
turns out to not be as strong as we need right away, it's an immediatly viable
product. CNT are already viewed by many in some fields(physics and chemestry
especially) as the most important topic currently being worked on, and most of
those people I am sad to say are not likely to be SE fanatics. CNT's are worth
the investment for so many reasons outside of the SE, don't worry. The money
will get there.

Simon



-----Original Message-----

> Date: Mon Jun 05 22:05:43 PDT 2006
> From: "David Forslund" <forslund@...>
> Subject: Re: [space-elevator] Anti-SE news
> To: space-elevator@yahoogroups.com
>
> Sounds like we really won't know until one builds long cables.  Hopefully
> it won't cost too much to find out.
>
> Dave
> Brian Dunbar wrote:
> > David Forslund wrote:
> > > I haven't gone through the math but this article is along the lines of
> > > concerns
> > > that I've had for a long time, that the nano-tube strength might not be
> > > preserved
> > > when turned into a long cable due to bonding issues.   Is there other
> > > analysis
> > > on this subject or any criticisms?
> > >
> > > Dave Forslund
> >
> > Yes.  See Tom Nugent's post on our blog.
> >
> > http://www.liftport.com/progress/wp/?p=839
> >
> >
> > --
> > Brian Dunbar
> > System Administrator
> > Liftport - The Space Elevator Company
> >
> > brian.dunbar@...
> > aim: bdunbar1967
> >
> > this email is: [ ] bloggable [x] ask first [ ] private
> >
> > Remember.
> > But move forward, too. Light a candle, yes. But also drive a rivet.
> > ~Lileks
> >
> >
>
>

Check out the the study referenced below:

http://arxiv.org/PS_cache/cond-mat/pdf/0606/0606105.pdf


Sounds very promising to me. Thoughts anyone?

To build the SE will require a high degree of automation. My NSECC
blog has a copy of an article from AW&ST titled: "Orbital Express To
Test Full Autonomy for On-Orbit Service" that talks about this.

http://seattlewebcrafters.com/nsecc/?q=node/view/29

Bert

--- In space-elevator@yahoogroups.com, "Keith Shultz" <kshultz222@...>
wrote:
> Check out the the study referenced below:
> http://arxiv.org/PS_cache/cond-mat/pdf/0606/0606105.pdf
> Sounds very promising to me. Thoughts anyone?

I was disappointed when it is mentioned CMWNTs are a theoretical
construct, but then the last two pages illustrate a potential
manufacturing procedure.  I don't follow their reasoning at all
though.  They say hitting nested tubes with an electron beam induces
defects.  They say the lowest energy state of CNTs is defect free.
Then they propose assembling CMWNTs (I don't know if they are just
nested CNTs or something "tighter"), and hitting them with an electron
beam.  They say that will somehow take away all the sidewall defects.
Maybe there is some other mechanism where the CMWNTs "force" the
defects to fix, but it isn't described here so I'm pessimistic.  CMWNTs
would easily be strong enough to build the SE (maybe even the loop-SE)
if they actually can be built.

I'm not really up to all the physics involved, but a pulley system
would seem to solve a lot of the power issues. If it were longer than
above the gravitational midpoint (i.e. the altitude cargo becomes
weightless) the cargo itself would provide lift. It could have an L
shape on the bottom and possibly lengths of nanotude formed into a rope-
type arrangment for repair.

Hi Andreas,

Any update on the spreadsheet?

Thanks,
Bert


--- In space-elevator@yahoogroups.com, "Andreas" <awnd329@...> wrote:
>
>
> I agree. And in any case, it is premature to talk about physical
> models before the most basic computational models have been
explored.
>
> In a first pass I have convinced myself that drag can be overcome,
> that power can be supplied to keep the ribbon rotating, and that the
> material requirements are moderate, compared to the SE.
>
> Instead of when to start building what, I would much rather have a
> debate here challenging this notion, so we can either put the idea
to
> rest or crystallize it into something closer to permitting talk of
> prototypes.
>
> I will attempt to make my spreadsheet so that it would be useful to
> others, and then upload it. That will take a little more work,
> unfortunately. Meanwhile, please challenge my various assertions.
Much
> can be explained without numbers.
>
> Andreas
>
>
> --- In space-elevator@yahoogroups.com, "Robert Munck" <munck@>
wrote:
> >
> > The definition of "model" that I use is:
> >
> >   X is a model of Y if X can be used
> >   to answer questions about Y.
> >
> > The value of a model depends on the set of questions
> > about the object being modeled that you want to answer.
> > You can't argue about whether or not something is a
> > model if you haven't specified the set of questions
> > that you want it to answer.
> >
> > Bob Munck
> >
>

I think one can use a Space Station like counterweight for a space elevator to
the Moon.

Is there any private organization (association) to colonize the Moon?.

Regards.

[Non-text portions of this message have been removed]

http://www.economist.com/displaystory.cfm?story_id=7001786

Waiting for the space elevator

Jun 8th 2006
From The Economist print edition


Space: After decades of speculation, the idea of a "space elevator"
capable of lifting payloads into orbit is being taken a bit more
seriously

FOR decades science-fiction writers and engineers have dreamed of
building a lift from the Earth's surface into space. Konstantin
Tsiolkovsky, a Russian scientist, suggested a similar idea more than
a century ago, and in 1979 Arthur C. Clarke wrote an entire
novel, "The Fountains of Paradise", about the construction of a
space elevator. Whisking satellites, space probes and even people
into orbit on a giant elevator appears far more civilised than
expensive, unreliable rockets.

Now this fanciful dream is taking its first tentative steps towards
reality. Two companies, LiftPort and X-Tech Projects, have been
founded to pursue commercial space-elevator projects, and America's
space agency, NASA, has provided a $400,000 prize-fund for an annual
competition, the Space Elevator Challenge, to encourage space-
elevator research. At this year's contest, to be held in October, 21
teams will test their designs for cables, and robotic lifts to climb
up them.

The concept of a space elevator is simple enough. An orbiting
satellite is linked to the surface of the Earth by a cable, which
vehicles then climb up and down. However, to reach a satellite in
geostationary orbit—which takes exactly a day to circle the Earth,
and so seems to hover above a single spot on the equator—the cable
would have to be nearly 35,800km (22,250 miles) long. Such a cable
would have to be phenomenally strong and light to support its own
weight.


It has long been recognised that carbon nanotubes, tiny molecular-
scale threads of carbon atoms, would be strong enough to build such
a cable. (Even though nanotubes were discovered only in 1991, Dr
Clarke suggested something very similar in his book:
a "hyperfilament" made of "pseudo-one-dimensional diamond crystal".)
But it is not yet possible to produce nanotubes in sufficient
quantity, or to knit them into a rope with anything like the
strength of the tiny, individual tubes. So far, the strongest
commercially available fibre of the required weight is around 4% as
strong as a space elevator would require, says Ben Shelef, co-
founder of the Spaceward Foundation, which runs the space-elevator
competition. He notes that if researchers can increase the strength
of that fibre by 50% a year, they will produce a fibre strong enough
by 2013. Such speedy progress is not unusual in a new field.

The next problem is to work out how to power the lifts, which will
take several days to make the long trip into orbit. Carrying fuel or
batteries on board would be impractical, as this would add massively
to the weight of the lift, and reduce its carrying capacity. So both
LiftPort and X-Tech are designing climbing modules equipped with
solar panels that receive power from a laser beamed from the ground.
The technology to make this possible is still under development, but
compared with the challenges posed by the cable, it's
straightforward, says Mr Shelef.

Then there is the danger of orbiting space debris left over from
decades of launches, which could damage or destroy the cable. Mr
Shelef proposes using radar to detect chunks of debris before a
collision, and then steering the cable around them. Fixing the
bottom of the cable to an ocean-going platform would make it easy to
move, he suggests.

If these problems can be overcome, building a space elevator is
expected to cost around $10 billion—a modest sum by the standards of
space exploration. LiftPort estimates that satellites could be
launched at around one thousandth of the cost of using rockets. But
NASA is sceptical, despite supporting the space-elevator
competition. "Since the basic material has yet to be developed, it
is still in the research phase and is not a current programme at
NASA," says a spokesman.

In February LiftPort conducted one of the most elaborate space-
elevator tests so far. Hot-air balloons secured a cable in place for
six hours, and robots then climbed up and down it. The cable reached
only a mile into the sky, it is true. But engineers have, in effect,
pressed the "call" button—though as so often when waiting for a
lift, there is now likely to be a long wait until it arrives.

Very good information thanks for passing it on.

andrewcooper20002000 <andrewcooper2000@...> wrote:  
http://www.economist.com/displaystory.cfm?story_id=7001786

Waiting for the space elevator

Jun 8th 2006
From The Economist print edition


Space: After decades of speculation, the idea of a "space elevator"
capable of lifting payloads into orbit is being taken a bit more
seriously

FOR decades science-fiction writers and engineers have dreamed of
building a lift from the Earth's surface into space. Konstantin
Tsiolkovsky, a Russian scientist, suggested a similar idea more than
a century ago, and in 1979 Arthur C. Clarke wrote an entire
novel, "The Fountains of Paradise", about the construction of a
space elevator. Whisking satellites, space probes and even people
into orbit on a giant elevator appears far more civilised than
expensive, unreliable rockets.

Now this fanciful dream is taking its first tentative steps towards
reality. Two companies, LiftPort and X-Tech Projects, have been
founded to pursue commercial space-elevator projects, and America's
space agency, NASA, has provided a $400,000 prize-fund for an annual
competition, the Space Elevator Challenge, to encourage space-
elevator research. At this year's contest, to be held in October, 21
teams will test their designs for cables, and robotic lifts to climb
up them.

The concept of a space elevator is simple enough. An orbiting
satellite is linked to the surface of the Earth by a cable, which
vehicles then climb up and down. However, to reach a satellite in
geostationary orbit—which takes exactly a day to circle the Earth,
and so seems to hover above a single spot on the equator—the cable
would have to be nearly 35,800km (22,250 miles) long. Such a cable
would have to be phenomenally strong and light to support its own
weight.


It has long been recognised that carbon nanotubes, tiny molecular-
scale threads of carbon atoms, would be strong enough to build such
a cable. (Even though nanotubes were discovered only in 1991, Dr
Clarke suggested something very similar in his book:
a "hyperfilament" made of "pseudo-one-dimensional diamond crystal".)
But it is not yet possible to produce nanotubes in sufficient
quantity, or to knit them into a rope with anything like the
strength of the tiny, individual tubes. So far, the strongest
commercially available fibre of the required weight is around 4% as
strong as a space elevator would require, says Ben Shelef, co-
founder of the Spaceward Foundation, which runs the space-elevator
competition. He notes that if researchers can increase the strength
of that fibre by 50% a year, they will produce a fibre strong enough
by 2013. Such speedy progress is not unusual in a new field.

The next problem is to work out how to power the lifts, which will
take several days to make the long trip into orbit. Carrying fuel or
batteries on board would be impractical, as this would add massively
to the weight of the lift, and reduce its carrying capacity. So both
LiftPort and X-Tech are designing climbing modules equipped with
solar panels that receive power from a laser beamed from the ground.
The technology to make this possible is still under development, but
compared with the challenges posed by the cable, it's
straightforward, says Mr Shelef.

Then there is the danger of orbiting space debris left over from
decades of launches, which could damage or destroy the cable. Mr
Shelef proposes using radar to detect chunks of debris before a
collision, and then steering the cable around them. Fixing the
bottom of the cable to an ocean-going platform would make it easy to
move, he suggests.

If these problems can be overcome, building a space elevator is
expected to cost around $10 billion—a modest sum by the standards of
space exploration. LiftPort estimates that satellites could be
launched at around one thousandth of the cost of using rockets. But
NASA is sceptical, despite supporting the space-elevator
competition. "Since the basic material has yet to be developed, it
is still in the research phase and is not a current programme at
NASA," says a spokesman.

In February LiftPort conducted one of the most elaborate space-
elevator tests so far. Hot-air balloons secured a cable in place for
six hours, and robots then climbed up and down it. The cable reached
only a mile into the sky, it is true. But engineers have, in effect,
pressed the "call" button—though as so often when waiting for a
lift, there is now likely to be a long wait until it arrives.












Yahoo! Groups Links









[Non-text portions of this message have been removed]

----- Original Message -----
From: "ESA" <contactesa@...>
Sent: Thursday, June 15, 2006 11:42 AM
Subject: Control system tests begin for Vega's main engine


> Development of Vega, Europe's new launcher for small payloads, continues
> at full speed. A dedicated test facility for the directional control
> system of the main engine has been completed and performance measurements
> are under way.
>
> Full story:
> http://www.esa.int/SPECIALS/Launchers_Home/SEM1T6AATME_0.html
>

--- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@...>
wrote:
>
> It might be worth considering SE as part of a bigger effort to move
> the world over toward a hydrogen economy, this alone would justify
> the SE. An SE along with break throughs in nanotech required to
build
> a SE would make SPSs a cheaper and clean source of electrical
power.
> The RD and engineering efforts for nanotech/CNTs should make
storing
> H2 and the practicability of SPS more feasible.
>
> Example Applications:
> Micro wave amps
> http://nanotechweb.org/articles/news/4/10/7/1
>
> Hydrogen Storage
> http://www.nrel.gov/docs/gen/fy02/31288.pdf
>
>
> For a historical comparison a key motivation for the Panama Canal
> built to get Teddy Roosevelt's "Great White Fleet" from the
Atlantic
> to the Pacific in less time. The Canal was an ultimately a great
> commercial success, but it was justification was military. A
similar
> argument can be made for the Interstate Highway System.
>
> The world seems to be waking up for the need for clean renewable
> energy, and the SE should be part of the solution.
>
also:
Looming energy crisis requires new 'Manhattan Project': US scientists

See: http://tinyurl.com/ozm2v

And other ideas, different from destruction.

Regards.
   ----- Original Message -----
   From: Herbert Murray
   To: space-elevator@yahoogroups.com
   Sent: Monday, June 19, 2006 7:58 PM
   Subject: [space-elevator] Re: Political Motivation for SE


   --- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@...>
   wrote:
   >
   > It might be worth considering SE as part of a bigger effort to move
   > the world over toward a hydrogen economy, this alone would justify
   > the SE. An SE along with break throughs in nanotech required to
   build
   > a SE would make SPSs a cheaper and clean source of electrical
   power.
   > The RD and engineering efforts for nanotech/CNTs should make
   storing
   > H2 and the practicability of SPS more feasible.
   >
   > Example Applications:
   > Micro wave amps
   > http://nanotechweb.org/articles/news/4/10/7/1
   >
   > Hydrogen Storage
   > http://www.nrel.gov/docs/gen/fy02/31288.pdf
   >
   >
   > For a historical comparison a key motivation for the Panama Canal
   > built to get Teddy Roosevelt's "Great White Fleet" from the
   Atlantic
   > to the Pacific in less time. The Canal was an ultimately a great
   > commercial success, but it was justification was military. A
   similar
   > argument can be made for the Interstate Highway System.
   >
   > The world seems to be waking up for the need for clean renewable
   > energy, and the SE should be part of the solution.
   >
   also:
   Looming energy crisis requires new 'Manhattan Project': US scientists

   See: http://tinyurl.com/ozm2v





[Non-text portions of this message have been removed]

The is some discussion on the liftport's blog about a pole base SE.
There is a concept called orbital rings I don't think it is the same
thing as Aerovator but may worth looking at:

http://www.liftport.com/progress/wp/?p=870

Bert

--- In space-elevator@yahoogroups.com, "Andreas" <awnd329@...> wrote:
>
> --- In space-elevator@yahoogroups.com, kyros <kyros@> wrote:
> >
> >
> > There we go. An arguement that succesfull challanges it properly.
> Any idea what the order of the shear forces is?
> >
> > S
> >
> Roughly. For the cable to stay suspended, lift is equal to weight.
> Drag is less than lift by the lift/drag ratio (~20 at subsonic
speed,
> ~5 in the hypersonic range). Thus, the total drag will be at most
20%
> of the weight of the cable. Thus, the additional strength needed to
> support the drag will be at most 20% of the strength needed for the
> cable to support itself if it was hanging down. If I am not
mistaken,
> that is a relatively minor penalty.
>
> To transmit this 20% or less shear force, the cable will lag behind
> the radial in the shape of a spiral, at an angle between spiral and
> radius that is the arctan of the ratio between radial tension and
> "shear" force. Via the above argument, the shear force will
generally
> be much smaller than the radial tension, leading to a fairly small
> spiral angle.
>
> Andreas
>

Link to Paul's page with links to download docs discussing orbtial
rings:

http://www.paulbirch.net/





--- In space-elevator@yahoogroups.com, "Herbert Murray" <hcm1955@...>
wrote:
>
> The is some discussion on the liftport's blog about a pole base SE.
> There is a concept called orbital rings I don't think it is the
same
> thing as Aerovator but may worth looking at:
>
> http://www.liftport.com/progress/wp/?p=870
>
> Bert
>
> --- In space-elevator@yahoogroups.com, "Andreas" <awnd329@> wrote:
> >
> > --- In space-elevator@yahoogroups.com, kyros <kyros@> wrote:
> > >
> > >
> > > There we go. An arguement that succesfull challanges it
properly.
> > Any idea what the order of the shear forces is?
> > >
> > > S
> > >
> > Roughly. For the cable to stay suspended, lift is equal to weight.
> > Drag is less than lift by the lift/drag ratio (~20 at subsonic
> speed,
> > ~5 in the hypersonic range). Thus, the total drag will be at most
> 20%
> > of the weight of the cable. Thus, the additional strength needed
to
> > support the drag will be at most 20% of the strength needed for
the
> > cable to support itself if it was hanging down. If I am not
> mistaken,
> > that is a relatively minor penalty.
> >
> > To transmit this 20% or less shear force, the cable will lag
behind
> > the radial in the shape of a spiral, at an angle between spiral
and
> > radius that is the arctan of the ratio between radial tension and
> > "shear" force. Via the above argument, the shear force will
> generally
> > be much smaller than the radial tension, leading to a fairly small
> > spiral angle.
> >
> > Andreas
> >
>

--- "Herbert Murray" <hcm1955@...> wrote:
>
> Link to Paul's page with links to download docs discussing orbtial
> rings:
>
> http://www.paulbirch.net/

We had a fairly long discussion of this concept in the space-tech
mailing list back in the late 80's or early 90's. The idea was
a ring or belt all the way around the Earth at LEO height and
moving at faster than orbital speed for that altitude. I called it
an "orbital hula-hoop" when I suggested the idea.  There would be
small stations riding on the loop magnetically with cables going
down to the surface.  The excess speed of the loop would hold the
whole ring in tension and would also support the station and the
weight of the cable, aka "spoke."  There would be at least six such
spokes, maybe dozens; vehicles could climb the spoke and then couple
magnetically to the moving hoop and be accelerated up to orbital
speed.

An embellishment would be to have multiple concentric hoops, say
at 50 km, 100 km, 200 km, 300 km, and so on, maybe all the way up
to GEO. Now you have the equivalent of an SE (or six of them), but
with much lower strength requirements on the vertical cable and
no counterweight.

The discussion died out when it was realized that the whole thing
would be horribly unstable, would have oscillation modes all over
the place, and wouldn't fail very safely.

Bob Munck

In a message dated 6/22/2006 10:02:10 P.M. Central Daylight Time,
munck@... writes:

We had a  fairly long discussion of this concept in the space-tech
mailing list back  in the late 80's or early 90's. The idea was
a ring or belt all the way  around the Earth at LEO height[....] whole thing
would be horribly  unstable, would have oscillation modes all over
the place, and wouldn't  fail very safely.



This system is in effect the baby brother of Larry Niven's Ringworld.   Do we
even have materials that could embody it?


[Non-text portions of this message have been removed]

--- GEddieA95@... wrote:
>
> This system is in effect the baby brother of Larry Niven's
> Ringworld.

Not really, other than being the same general shape. Ringworld
didn't have spokes connected to the sun. The hula-hoop doesn't
have people walking around on the inner side.

I think of it more as the big brother of the Lofstrom Loop.
The orbital hula-hoop is more like Niven's shadow squares.

> Do we even have materials that could embody it?

Well, sure. If the hoop is moving at orbital velocity, there's
no strain on it at all.  One km/hr faster, a tiny bit of strain.
And so on.  To increase the payload that the spokes can carry,
you can increase EITHER the speed of the hoop or its mass. The
SE, unfortunately, doesn't work that way.

Bob Munck