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March 11, 2010, 06:29:19 PM *
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tigre
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« on: June 12, 2009, 12:53:33 PM »

In the late 1970's, Buckminster Fuller expressed disdain for the way in which humans are violently launched into space, strapped inside cramped cabins atop a gigantic controlled explosion.  Fuller disparaged this expensive, dangerous, restrictive, frightening and sometimes fatal technology.

As a sensible alternative, the relative simplicity of space tether science beats horrific explosions hands down.  Unfortunately, the notion of clambering up a ribbon requires payload mass to be limited by tether strength.

Fuller spoke about volume-to-mass ratio, pointing out that transport ships can be designed to float massive payloads out of earth's gravity well and into space.  The larger the ship, the greater the payload.  Basically, Fuller was envisioning a sort of advanced dirigible structure.

Fast-forward to our nano-enhanced 21st Century, and it's easy to visualize ultra-light and ultra-strong fabrics woven of nanothreads, comprising the skins of huge inflated space transport and habitation ships.

How can such enormous vehicles pass through atmospheric turbulence?  They are harnessed to an array of nanocable space tethers which stabilize them from severe buffeting.  The number of cables will depend on the size of the ship; a circular array of eighteen tethers should be suitable for initial planning discussions.  The cables do not support the weight of the ships or their payloads; the solar powered vehicles rise on their own, harnessed to the cable array in carabiner fashion.

While harnessed to the cables, each flexible tubular transport ship is curled into a donut shape. Because no weight is put on the cables, a number of ships can ascend in succession.  Once in space, these ships can be linked together like train cars.  At their final destination, large numbers of ships can be joined to form a massive rotating space station, many miles in circumference.  The manufacturing cost of the vehicles can be economical enough that groups of space-colonist families will be able to afford to travel together to the site of the space station at, say, Lagrange Point 5.
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A_M_Swallow
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« Reply #1 on: June 12, 2009, 03:37:27 PM »

Balloons have difficulty raising above about 30km.  Since this is a form of balloon it probably has a similar limit.
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Andrew Swallow
Frank
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« Reply #2 on: June 13, 2009, 04:13:55 PM »

Using a two stage balloon concept the folks at JP Aerospace plan to go much higher in a balloon.  The second stage balloon is assembled at the height the first stage can reach.  It is very large and to fragile for the lower atmosphere.  Once the second stage balloon reaches its maximum height they will use an ion engine to reach orbital speed.  Then on into space.  Their plan will drastically decrease the cost of getting stuff to space.
« Last Edit: June 13, 2009, 04:18:16 PM by Frank » Logged
neil
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« Reply #3 on: June 14, 2009, 08:18:22 AM »

The second stage balloon should get the payload from 30 kilometers to 40 kilometers. The ion engine can not push the huge fragile 2nd stage balloon the rest of the way to the top of the atmosphere in less than a week, as air resistance is significant for another 50 kilometers. We have considerable cost moving the very fragile balloons back to 30 kilometers where they can serve as a 2nd stage for another payload.
Even if we can get the very fragile balloons to orbit, it is only strong enough to produce a tiny amount of gravity in a spinning ring configuration of 6 to 600 balloons. Moving people and supplies from one balloon to another safely in the ring is challenging.
Perhaps the ion engines can get the ring of balloons to Earth moon L1. My guess is L5 would take years of continuous thrusting.
My guess is totally impractical until we have cheap CNT with great specs or equivelent. The nano cable space tethers have me confused. Are you thinking space elevators with counterweights at about 100,000 kilometers, or balloons at 40 kilometers, tied to the ground with a tether. I'm not confident that either protects the fragile balloons much from buffeting.   Neil
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tigre
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« Reply #4 on: June 16, 2009, 07:41:28 AM »

Thank you for your responses to the Tether Array project.  Further discussion of the transport vehicles, space station construction, capabilities, features, amenities and resident lifestyles can take place at a later time.  Initially, we seek to determine feasibility and practicality of an arrayed tether system that provides a number of nanocables to stabilize huge spacebound vehicles without putting payload weight on the cables.  Here are some questions which need to be considered:

1.  In what ways might the absence of applied weight advance the time schedule of this or any space tether project?

2.  Assuming the cables are braided strands of nanowire, how long must the individual strands of wire be, in order to hold the braid without it pulling apart? 

3.  Is it best to braid the cables from the nanowires at the Array site, as the cables are ascending, for ease of on-ground manufacturing and installation?

4.  Thinner cables (not required to support payload weights) will have less weight/mass of their own, and need smaller amounts of mass orbiting in place to stretch them outward from Earth. What is the best way to accumulate the mass needed at the Space end of the cable?  If a great deal of weight is required, the source could be aggregate, shuttled or slung up from the moon, which would call forth the need for some sort of Moon Colony.

Since these space vehicles need to be gigantic in order to most easily be "floated" out of the gravity well, they cannot in any way be fragile.  Although they will have a tremendous volume-to-mass ratio, they are not actually balloons, nor are they gossamer structures.  Their structural strength is achieved by knitting a tapestry of nanothreads with a multiplicity of characteristics into a one-piece skin forming the outside of the structure.  How the vehicles are designed inside will depend on what work is to be done and/or what is to be carried within them.  The singular purpose of the Space Tether Array is to bolster these vehicles against lateral movement as they ascend through atmospheric turbulence into near space.

(Neil, you are correct about L1.  L5 is a romance at least several generations away.)
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