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The space elevator - climbing a ribbon all the way to space?

Posted by: The Legionnaire - Mon Jul 28, 2003 9:58 pm
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The space elevator - climbing a ribbon all the way to space? 

When will the first space elevator enter service?
By the year 2020. 14%  14%  [ 7 ]
Between 2020 and 2040. 31%  31%  [ 16 ]
Beyond 2040. 29%  29%  [ 15 ]
Never - it's impossible! 25%  25%  [ 13 ]
Total votes : 51

The space elevator - climbing a ribbon all the way to space? 
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Post    Posted on: Wed May 26, 2004 9:19 pm
You can ride this up the cable with out using any motors. Just use it as a guide line. When you go as far as you can then re-attach to the cable and hoist the elevator the rest of the way to geo sync orbit . This will cut down the time it will take to reach space. Also it will cut down on maintains of the cable and motors. You will not need a power plant to beam energy up to the elevator if the balloons are doing the work for you. And you may only need solar panels and batteries to move the rest of the way because the elevator will weight a lot less do to the earths rotation.

On the way down you can remove some of the helium via a compressor and tank and allow the elevator to descend quickly. Only using smaller motor to control the descend or stopping the elevator. This will save on weight and energy used to move the elevator up and down.

There also a safety factor to consider. At any time the cable snaps a well placed explosive bolts/cutters can cut the cables on both side of the elevator and let it float safely to the ground.


Last edited by DJBREIT on Wed May 26, 2004 9:41 pm, edited 1 time in total.



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Post    Posted on: Wed May 26, 2004 9:31 pm
Sigurd wrote:
n54 wrote:
there's a whole seperate thread on that link, why the crossposting?

You're right, lets keep this topic about space elevators, or as DJBREIT wrote, "connect the dots ".. so maybe a comparission between Elevation <> Airships.


Use them together


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Post    Posted on: Sat Sep 24, 2005 7:17 am
The article "Space Elevator Concept Undergoes “Reel” World Testing" ( www.space.com/businesstechnology/050923 ... _test.html ) is reporting today the first successful test of a climber - after 18 versions of the climber have been tested before.

According to the article the test has been promising. The trip has gone up to 300 meters only but LiftCorp obviously is applying a step-by-step-concept which reminds me to JP Aerospace.

They used a balloon to hold the tether up - again I am thinking of JP Aerospace. It's the DSS this time.



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Post    Posted on: Thu Jun 01, 2006 8:19 am
Hello, Joe_Liftport,

in another thread of this section you wrote:

Quote:
Posted: Wed May 31, 2006 3:28 pm Post subject:

--------------------------------------------------------------------------------

Quote:

We really need a VHLV (Very Heavy Launch Vehicle) 400+ tons


I could get behind that idea. The fewer launches we need to purchase, the lower the material strength needs to be, and the faster we can put up the LiftPort Space Elevator.


and

Quote:
Posted: Thu Jun 01, 2006 6:10 am Post subject:

--------------------------------------------------------------------------------

The ribbon will need to be launched by conventional rocket into orbit. From there, the ribbon will be deployed downward to earth as the counterweight moves out beyond GEO.

The starting plan calls for a 'starter' ribbon which we're currently estimating is going to require between 5 and 8 launches of the Falcon 9 S9 or Saturn V sized launches.

With a much larger launch payload, we can either send a wider/higher capacaty 'starter' or a little bit lower GPa material within the timeframe necessary to make it a viable commercial venture.

(btw, thanks N.S., you're purchase is appreciated.)


What about detailing the reasons and origins of the result, that HLLV would be required? Decisions like that should be based on comparisons to as much alternatives as possible which I am missing a bit in several threads.

There is another problem - an italian scientists recently discovered problems to produce the required ribbon. I will look for the article and I don't agree that easily to the scientists for a particular reason - but it seems bit too early to call for a HLLV instead of looking how HLLVs, Falcons or CXV-like vehicles could be applied.



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Post    Posted on: Sat Jun 03, 2006 7:08 am
In between there is an article in English about it - "Nanotubes Might Not Have the Right Stuff" ( www.space.com/businesstechnology/techno ... 60602.html ).

Nicola Pugno's argument is
Quote:
that inevitable defects will greatly reduce the strength of any manufactured nanotubes. Laboratory tests have demonstrated that flawless individual nanotubes can withstand about 100 gigapascals of tension; however, if a nanotube is missing just one carbon atom, it can reduce its strength by as much as thirty percent


Of course that should be compered to Bradley C. Edwards' study - I am not sure if he had in mind just what has been investigated. I seem to remember that he has in mind to use a bundle of such ribbons which are embedded in epoxy.

Also there is the tested and experimented method to produce nanotube-ribbons scientists have found and that is said to be capable of infinitely long ribbons.



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Post    Posted on: Sat Jun 03, 2006 5:26 pm
I am sure there are a lot of very old high tension steel cables (Golden Gate comes to mind) that have had threads of steel break but the cable still does fine.

Until someone makes and tests various weaving methods and patterns of the fibers, who can say? I think it's way to early to say the material doesn't have the right stuff, however.


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Post Re: The Holy Grail of Space Travel?   Posted on: Tue Jun 06, 2006 5:38 am
Space tethers need not be the ultimate soultion to space travel. They are technically possible now. As we develop a better understanding of both tether dynamics and of tether materials, tethers can act as stepping stones toward the space elevator.

At the same time the tethers can reduce the energy cost (delta V) of space travel.

Space tethers are not mutally exclusive to solar sail or solar photovoltaic propulsion. These are precisely the technologies we need to maintain the tether in a proper orbit as it transfers momentum (energy too) to the cargos it flings into space.

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Post    Posted on: Fri Jun 09, 2006 3:25 am
A skyhook type tether?


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Post    Posted on: Fri Jun 09, 2006 4:52 am
bad_astra wrote:
A skyhook type tether?


No, I have in mind a rotovater type tether. Wikipedia entry follows:
=====================================
Rotovators

The word rotovator is a portmanteau derived from the words rotor and elevator. A rotovator is a high speed rotating tether (sometimes called momentum exchange tethers), rotating so that the tips have a significant speed (~1-3 km per second).

A spacecraft in one orbit can rendezvous with one end of the tether, latch to it and be accelerated by its rotation. The tether and spacecraft would then later separate, when the spacecraft's velocity has been changed by the rotovator.

This is not free. The tether's momentum and angular momentum is changed, and must be recharged.

An example of use would be a rotovator in a circular orbit with the tip velocity zero relative to (or at) the ground that grabs an object from high altitude. However this obvious earth-to-orbit rotovator (skyhook) cannot be built from currently practical materials since the spin rate to give this tip speed is too high for current materials.

However, on airless bodies with reasonably low orbital speed (such as the Moon), a rotovator in low orbit can actually touch the ground and would provide cheap surface transport as well as launching materials into cislunar space. Although it might be thought that this requires constant reboost, in fact it can be shown to be energetically favourable to lift cargo off the surface of the Moon and drop it into a lower Earth orbit, since the moons surface is in a higher potential energy state; constant cycling of materials in loops can keep the system going continuously.

Thus rotovators can be charged by momentum exchange. Momentum charging uses the rotovator to move mass from a place that's higher in a gravity field to a place that is lower in a gravity field. The energy from the falling weight speeds up the rotation of the rotovator. For example, it is possible to use a system of two or three rotovators to implement trade between the Moon and Earth. The rotovators are charged by lunar mass (dirt, if imports are not available) dumped on or near the Earth, and can use the momentum so gained to boost Earth goods to the Moon.

Systems of rotovators could theoretically open up inexpensive transportation throughout the solar system as well, as long as the net mass flow is towards a massive body, such as the Sun, or the Earth.

In a strong planetary magnetic field such as around the Earth or Saturn, a conducting rotovator can be configured as an electrodynamic tether. This can either be used as a Dynamo, which slows the tether, whilst generating electrical power and changing the angular momentum, or alternatively increasing its orbital speed and/or changing its angular momentum can be performed electrically from solar or nuclear power, by running current through a wire that goes the length of the tether. Ultimately, such a tether pushes against the angular momentum of the planet.

(One complication is that as the tether rotates, the direction of current must reverse to act against the magnetic field twice per cycle.)

One trick for using weaker materials is to put the rotovator in an elliptical orbit. It would pick up a load at periapsis (closest approach), then vary the tether length or attachment point to throw the load (from the top of the tether) at a later time into a higher orbit. This splits the speed-exchange into two parts, each contributing half of the final velocity. It reduces the necessary size, strength and weight of the tether dramatically. It might be called a "revovator" because it exchanges momentum in both revolution and rotation. Recharging such a rotovator is more complex, too.

Another trick to achieve lower stresses is that rather than picking up a cargo from the ground, at zero velocity, a rotovator can pick up a moving vehicle and sling it into orbit. For example, a rotovator could pick up a Mach-12 aircraft from the upper atmosphere of the Earth, and move it into orbit without using rockets. It could likewise catch such an aircraft, and lower it into atmospheric flight. This would save tons of fuel per flight, and permits both a simpler vehicle and more cargo.

An important practical modification of a rotovator would be to add several latch points, to achieve different momentum transfers. Another useful concept would be to add a linear motor to the rotovator, to accelerate spacecraft or materials to higher speeds than the tip speed of the tether.

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Post    Posted on: Fri Jun 09, 2006 7:05 am
Ah ha, this put in mind a sci-fi book I read when small where living tree like structures provided this very service. Rotating in orbit around some planet, one end constantly dipping in through the atmosphere, the other end sending out intersolar craft and seeds for new trees. I just thought this was fantastical at the time, but came to realise the principle is feasable. Well, except for the living organism being the rotavator in question.

Ha! Sci-fi rules. Just wait a hundred years for the ideas to fester a bit.

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Post    Posted on: Fri Jun 09, 2006 7:06 pm
lgroner wrote:
bad_astra wrote:
A skyhook type tether?


No, I have in mind a rotovater type tether. Wikipedia entry follows:
=====================================
Rotovators


http://members.aol.com/Nathan2go/lunavat.htm



To send up bulk mass for a lunar rotorvator, a howitzer could be used from the moon to orbit shells containing regolith-concrete.


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Post    Posted on: Fri Jun 09, 2006 7:10 pm
Ekkehard Augustin wrote:

What about detailing the reasons and origins of the result, that HLLV would be required? but it seems bit too early to call for a HLLV instead of looking how HLLVs, Falcons or CXV-like vehicles could be applied.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)


It comes down to having less assembly. CaLV could have built ISS in four or five flights--as opposed to 40 STS flights, many Soyuz, etc.

We don't ship oil acroos the ocean on rowboats, but big supertankers. Go big or don't go at all.


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Post    Posted on: Fri Jun 09, 2006 7:26 pm
The downside being, once you have an SE, you no longer really need heavy lift.

However it's good to keep a spare HLV or two around just in case you loose the SE you have, as its too strategic an asset to not be replaced, because you're entire economy will be effect by it's existance.

In the event of failure it would have to be quickly replaced, and for that reason the ability to achieve heavy lift would certainly need to be kept around.


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Post    Posted on: Fri Jun 09, 2006 7:37 pm
SE won't replace HLV. If you want to go out of Earth moon--it helps to have all of your hydrogen tankage lofted in one go--to by pass SE and go on to Moon/Mars until such time as the SE has real infrastructure in place.

SE is better at replacing EELV and smaller craft to reduce space junk. A lot of the small sats and small sat launchers can be quite dirty in how they stage. SE's will be quite vulnerable to space junk, and smaller LVs and their payloads can be a threat. Some SLBMs use explosive cords and submerged nozzles to 'stage' and this places shrapnel high up.


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Post    Posted on: Fri Jun 09, 2006 8:19 pm
publiusr wrote:
SE won't replace HLV. If you want to go out of Earth moon--it helps to have all of your hydrogen tankage lofted in one go--to by pass SE and go on to Moon/Mars until such time as the SE has real infrastructure in place.

SE is better at replacing EELV and smaller craft to reduce space junk. A lot of the small sats and small sat launchers can be quite dirty in how they stage. SE's will be quite vulnerable to space junk, and smaller LVs and their payloads can be a threat. Some SLBMs use explosive cords and submerged nozzles to 'stage' and this places shrapnel high up.


Once you've reduced the cost of getting to GSO to dollars per pound, then you either develop the means to produce H2 en situ or you go with something better.

As for SLBM's being a threat: any missle launch will be a threat, but unless it's nearby It's not that big of a deal. I'd rather take my chances on that then a CaLV that gets at best three or four launches a year with at best one engine-out capabity.


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