One more small step towards the space elevator

[betazed]

http://www.space.com/astronotes/astronotes.html (the topmost article of Nov 17th)

Space Elevator Climbs at MIT

It was one small climb for the space elevator last week at the Massachusetts Institute of Technology (MIT) in Cambridge.

From high atop the roof of MIT’s Cecil and Ida Green Building, a tether was lowered to the ground as curious onlookers watched the display in suspended belief under snowy conditions.

A scale model of a robot lifter successfully made its way up the lengthy ribbon, under the watchful eye of Michael Laine, president and founder of LiftPort Incorporated. Based in Bremerton, Washington, LiftPort is a for-profit company devoted to the commercial development of an elevator to space. The lifter was designed by LiftPort's David Shoemaker.

LiftPort's scale model of a robot lifter successfully made its way up a tether at MIT's Cecil and Ida Green Building. Credit: Tom Nugent/LiftPort
(Click to Enlarge)

A lifter is a robotic cargo and construction car, a key element of the space elevator mass transportation system that would stretch from an ocean platform up, up and way beyond geosynchronous orbit.

The event was part of SpaceVision 2004, hosted November 11-14 by the Students for the Exploration and Development of Space (SEDS) and the MIT Mars Society.

With each passing day the chance that I will actually climb one to space before I die becomes better.

 

[Mark1031]

How exactly is this going to work? What is it attached to in space? It looks pretty flimsy. How does it withstand the atmospheric stresses?

 

[betazed]

mark,

check out http://www.spaceelevator.com/

for excruciating details (including specific calculations and measurements) i will suggest this book.

It all started with this great science fiction from Arthur C Clarke. Fountains of Paradise.

Now, those are the references. Here is the basic idea.

You put a mass in GEO. Then you lay out a string up and a string down so that the cg of the entire system stays in geo. Then when the down string reaches earth you tie it down. To go to space you just climb the string. as for flimsy, it is made of carnon nano tubes (lots of them). There is no limit really on how strong you want it to be. We could easily build a elevator to haul up 20 ton masses. Use that to build a 60 ton elevator. Use that to a build a 200 ton one and so on. Atmospheric stresses are minimal really. But that can be accomodated with varying the ribbon (the string) width. Also remember only a small portion of the string is in atmosphere. Most of it is out of the atmosphere.

 

[Mark1031]

Thanks......

 

[The Person]

Maybe I'll live to see the space elevator come true. That would be fantastic.

 

[Keirador]

I read about an idea for such a thing as soon as spider silk became a viable commercial product, because at the time spider silk or an artificial derivative (which this appears to be) was the only substance that could hold its own weight at such a length. Many scientists have predicted that the greatest innovations of the next few decades will come from textiles; this is one of them.

 

[Little Raven]

Carbon nano fibers beat the bejeezus out of spider silk. Good thing too, cause we're going to need them to make something like this a reality.

 

[betazed]

Carbon nano fibers beat the bejeezus out of spider silk. Good thing too, cause we're going to need them to make something like this a reality.

Not only that, carbon nanotubes can reach the theoritical limit of maximum strength of material of about 300 Gpa (giga pascals).

For a space elevator all we need is about 85 Gpa (which includes 100% safety margin).

 

[Keirador]

I said "at the time". This was perhaps two years ago, I'm sure that we have better stuff now. Although, am I mistaken in thinking that carbon nano fibers are a manmade variation on the spidersilk theme? I have not the time to thoroughly investigate this, but I believe the two are produced along the same (or at least similar) chemical and molecular structural lines. Understanding the makeup of spidersilk allowed scientists better insight with which to create stronger tensile material. . . no?

 

[betazed]

Although, am I mistaken in thinking that carbon nano fibers are a manmade variation on the spidersilk theme?

No. as usual check out Wiki

 

[JoeM]

I would love space elevators, but you can't pretend we are anything nearly even close to it being possible.

We can conceive the idea, but all the solutions to the many many problems are all future tech. Being realistic, nanotubes are a distant possible solution.

That doesn't mean it isn't a cool idea.

 

[betazed]

I would love space elevators, but you can't pretend we are anything nearly even close to it being possible.

We can conceive the idea, but all the solutions to the many many problems are all future tech. Being realistic, nanotubes are a distant possible solution.

have you read the literature on this subject? If you do then you will be pleasantly surprised. Most technical problems have been solved. We are really now in experimental verification stage (meaning we have solved all the technical problems on the drawing board and are now building the prototype hardware). As soon as carbon nanotube ribbons hit the 85 gpa tensile strength range - and are cheap to produce (give or take another 5-10 years max) - we are good to go.

 

[JoeM]

No I do follow it actually and I can't share your optimism based on Carbon Nanotubes.
There strength is theoretical which we hope to achieve at least 35% to enable this elevator.

Okay it is the last technological limitation, but that leaves out the engineering, production and other real-world issues.

You don't need me to tell you we are able to go to Mars. But no-one has done it in the thirty odd years we've been able to.

 

[betazed]

Okay it is the last technological limitation, but that leaves out the engineering, production and other real-world issues.

I do not understand why you are pessimistic. We can already create CNT fibers with 63 gpa tensile strength (although they are expensive). So why couldn't we create 85 gpa CNT in 10 years?

also remember this is not the only application of CNT. Lots of research is going on as the applications are numerous. Lot of money is being poured into this by various industries.

You don't need me to tell you we are able to go to Mars. But no-one has done it in the thirty odd years we've been able to.

Not because of technological problems but because of cost. It is going to cost anywhere between 50 to 100 billion $ to do a human mars program today (whatever Zubrin might say). But we can do a elevator for $10 billion now (if we have the CNT).

 

[Keirador]

CNT technology is similarly prohibitively expensive at this stage to develop and produce, regardless of the cost of actually building an elevator.



Perhaps spidersilk could provide an economically viable alternative. . .

 

[Pirate]

So far the world record for length of a CNT is 4 centimeters. How long do you think it will take before we can build a nanotube long enough for a space elevator (tens of thousands of miles long)?

 

[JoeM]

It's still based on if's my friend. I'm not saying it ill never happen, I'm waiting until the tech is there before getting excited.

 

[The Person]

Not because of technological problems but because of cost. It is going to cost anywhere between 50 to 100 billion $ to do a human mars program today (whatever Zubrin might say). But we can do a elevator for $10 billion now (if we have the CNT).

The Apollo Program cost almost 250 billion dollars. Why is 100 billion dollars for a Mars trip too much? And if we can build the elevator with 10 billion dollars, it's a bargain in comparison.

 

[Serutan]

Apollo wasn't $250 billion (unless this is a conversion to today's
dollars/costs). It was more like $10 B. In the 60s,
the defense budget was "only" $70B/year or so.

@Betazed - Technically speaking, you're wrong about the
idea starting with Clarke. He cites the origins of the idea
being in a paper published in the Soviet Union in, IIRC,
1966. However, "Fountains of Paradise" is likely the
first time the idea was brought before the general public.

 

[betazed]

So far the world record for length of a CNT is 4 centimeters. How long do you think it will take before we can build a nanotube long enough for a space elevator (tens of thousands of miles long)?

To answer your question let me ask the following : "The biggest piece of cotton that we can grow in a cotton field is a few cms. How long a piece of cloth can we sew using those cotton?"

The answer of course is, however long we wish.

The ribbon of the elevator is not made from a single nanotube. Even if we could do that, it would not be desirable for maintenance purposes. Rather think of it as a hundred thousand km piece of cloth that is sewn from trillions of individual nanotubes - each a few dozens of cms long. Of course the trick is in sewing them in the right way to get a desirable tensile strength. So research is currently continuing in two directions. Creating individual nanotubes cheaply and sewing them together cheaply.

@Serutan: You are correct. The first person to think of a elevator was a Russian thinker by the name of Konstantin Tsiolkovsky in 1895. Clarke popularized the idea and gave it the impetus.