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06 September 2006

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Patrick Kennedy

If things get to bad here on earth, it might make a good escape route.

billmon

I think it sounds like the title of a Led Zepplin song.

Babak Makkinejad

We do not have the materials with that tensile strength. You are talking about several orders of magnitude increase.

Once you get the material, the rest can be built.

Green Zone Cafe

Quite a few sailors have been killed or maimed by nylon mooring lines which parted and snapped back.

What would be the effect of a snap-back of one of these carbon nanotube lines going up to 35,786 kilometers (19,323 nautical miles or 22,241 statute miles).

Charlie Green

Great SF idea! The only problem is that the authors never study the actual astrophysics (or even basic physics) and societal problems involved. A geosynchronous orbit is at about 26,200 miles above the earth's average surface.

To be effective, the "rope" from the earth station at the lower end of the "elevator" to the space station involved must be very stable (in thousand of mile terms) so the ascendent doesn't have to chase it around the surface of the Earth due to winds, orbital variations, or loading effects. (One author put it near Mount Kilimanjaro) And that's the least of the problems.

Using the image on the post, the counterweight is in a higher orbital level than the Space Station (ESS = Elevator Space Station). That means it HAS to orbit slower than the ESS; how does the ESS system keep the "rope" aligned vertically? Using the ESS as the anchor is more plausible by making it a massive Space Station; maybe a captured asteroid?

Next problem: when the "elevator", which by definition must be both airtight, and meteor and cosmic ray shielded (eg, massive), begins ascent (or descent) the center of gravity of the entire system will change dramaticly due to acceleration and weight change forces. This will require some serious orbital corrections as the forces vary. Where's the fuel gonna come from?

If one rises or drops to just below the speed of sound to avoid mach turbulence (less than 760 MPH), the trip either way will take 34 plus hours. OK, the module will need bathrooms among other amenities. And wireless and cellphone access will be limited to the few miles above the earth without additional infrastructure.

I'm not gonna bother with details like acceleration rates (so passengers don't bounce off the ceiling), food, supply logistics (The turnaround with only one "elevator" is kinda long unless it is more like a train and then the mass gets serious; if there is more than one with dual cables then some of these problems are irrelevant but the total mass of the cables becomes significant. And keeping the cables from beating against each other becomes a problem.), and who's gonna pay for a project of this magnitude with questionable return on investment.

fred

So that is where Saddaam kept his WMD! (Sorry, couldn't resist)

Does bring to mind space based weapons, though.... heard a public/military affairs talk about that a couple years back at the University of Florida. Can't remember who put that on; not exactly pr but more informational - and a good information exchange - which we could use more of now.

Speaking of peak oil (again) Marvin Harris, anthorpologist at UF, had some comments on peak oil in one of his books (published ~1976, quoted some geologists at Shell, amongst others, putting peak oil happening in 1995 plus or minus a few years. Intresting book, though oil was tangental to the subject.

Michael Murry

From aerospace engineer Robert Zubrin's book "Entering Space" regarding the so-called "geostationary beanstalk," p. 99:

"The beanstalk concept as envisioned by Artsutanov, Pearson, and Clarke was a wonderful idea that offered a complete and easy solution to the problem of cheap Earth-to-space transporation. It had just one problem: it was impossible. It was impossible because if one places a load at the bottom of geostationary tether, the bit of tether holding it must be thick enough to support that load. The next bit of tether must be thick enough to support not only the load, but the bit of tether supporting the load. Thus as it proceeds to 36,000 km from the ground to geostationary orbit, the tether must get thicker and thicker, and its diameter and weight will grow exponentially. Depending on the strength-to-weight ratio of the tether material assumed, the cross-sectional area of the tether at the satellite would be 10 to 20 orders of magnitude greater than its area at the base, with similar incredible ratios holding between the tether mass and the mass of the payload it is required to lift. Unless fantastical materials, such as 36,000-km-long single-crystal graphite fibers with incredible strength-to-weight ratios, were assumed, a beanstalk designed to lift 1 ton would itself have to weigh quadrillions of tons. With real materials, the beanstalk just wouldn't work."

Zubrin does go on to say, though, that on the moon, with much less gravity and much shorter surface-to-orbit distances to overcome, something like a lunar beanstalk might have an outside chance of becoming a reality someday.

Like many of my generation, I clearly remember President Kennedy challenging America to get to the moon and back in less than a decade. I remember that we did it, too, in 1969. Somehow, though, a trip that we could once routinely make in three days forty years ago, we can only dream about doing again some decades in the future. Something bad happened to our once-pioneering space program.

Oh, well. We've always got Iraq and Afghanistan to point to with pride.

mike

Pie in the sky, but 'tether propulsion' may not be.

As I recall, there was at least one and possibly more "space tether" experiments done by a space shuttle crew a decade or more ago.

Also, I understood that the Italians did alot of theoretical work on tether propulsion but I see no mention of that in the wikipedia article.

W. Patrick Lang

All

Did anyone look at the math in the wiki on tether strengthsm thickness, etc.?
pl

RAM

An Earth to space beanstalk impossible? Maybe.

But back in the 1950s, we were positive Dick Tracy’s wrist radio was impossible. And everyone knew digital computers filled up whole rooms. How could it be any other way since they needed all those heat-producing tubes?

MarcLord

The math may be challenging, but the tensile strength is doable. By my calculations it shouldn't take more than USD 7.72 Trillion to build and should stay aloft for 3.63 years (rounded). Let's build it!

Glen

Pat,

I am uncertain if we will be able to build a space elevator soon, but I'm not willing to discount human ingenuity. I still vividly remember my dad turning to me while watching 2001 in the theater when the Discovery first came on screen and exclaiming that the movie producer had somehow stolen their design. I did not know at the time that ten years prior to that he had helped design, build and test a nuclear powered ramjet engine in the Nevada desert and then helped design a nuclear powered spacecraft based on the same technology.

As for peak oil, the benchmark work on the subject was M. King Hubbert's papers in the 50's, 60's and 70's which very accurately predicted the peak and fall of U.S. domestic oil production. Similar work done by many others is what has lead to estimates as to peak world oil occurring right about now, give or take twenty years. This has been somewhat clouded by the Saudi's when they quit publishing the data required for accurate estimates in the 70's. Plus, as someone else pointed out, it's really the shortfalls of light, sweet, crude which will cause problems. There is no real shortage of fossil fuels. I have a Hubbert paper in front of me right now which predicts US coal production will peak between 2180 and 2220 depending on whose estimates you use for coal reserves. It's just that light sweet crude is the "free lunch" of the fossil fuels, and changing from it will mean major changes in our energy distribution/infrastructure. Plus, we will have to deal with global warming as a result of burning fossil fuels as this is a very real problem despite what the current bunch of politicians tell us.

As for space elevators and space travel, well, I'm a firm believer that God didn't put all those universes out there just for us to look at.

Just my two cents,

Glen

Alex

I believe the reason why this proposal has been dusted off is the emergence of carbon-nanotube technology, which may be capable of producing a tether of sufficient strength-to-mass.

pbrownlee

If you have not seen the (premium) Economist June 8 2006 article "Waiting for the space elevator", it's been lifted to the Liftport Staff Blog at http://www.liftport.com/progress/wp/?p=866
It concludes with a fairly robust "if":
"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."

Freeman

Col: You asked if anyone had looked at the math.
I have not checked the cable thickness v. height formula nor the stress calculation for the assumption of use of carbon nanotubes. Nevertheless, I note the wiki article says that an hypothetical nanotube cable would be "just a millemeter wide at the base". This immediately raises two practical problems:
1. It doesn't give much scope for a friction grip by the climber, and the gripping device could be at great risk of damaging the fine cable. (See the substantial San Francisco cable-car gripping device on its driving cable.)
2. Because of the risk of physical damage to (or of defects in) small structures, construction codes typically will today limit the minimum cross-section size of any stressed member. (See for example bridge construction codes.)
Consequently, I reckon that any single stressed cable of only one millimeter width would therefore be banned, and as a single point failure mode would be doubly banned by any safety code.
So, it's going to take more than development of a lightweight, high-strength cable to get this project off the ground, so to speak.

JM

I, for one, hereby volunteer to be on the posse that gits ta lasso that asteroid!

Will

Glad you like WP. Went there to start the Patrick lang article, but there was already one there under W. Patrick. I wish I knew how to do a redirecit to Patrick Lang would go to W. Patrick.

For Space stuff, go to Heim Theory in Wikipedia. http://en.wikipedia.org/wiki/Heim_TheoryThis is a controversial theory that predicts faster than light travel. Trip to Mars in three days, Stars in weeks. It also correctly predcts masses of elementary particles but alas has no room for independent quarks.

The Israel Lobby is very strong at WP. I have been in a wheel war at the neofascism site. I put up an innocent addition that Professor Juan Cole observed that the Likud Party met many of the fascist criteria. I put it up once a day, and it gets taken down once a day.

Best Wishes.

Will

Oh for Chrissakes, make available a better pix to put up at the WP site. Release the one on this blog in the public domain, and I"ll upload it.

Best Wishes

W. Patrick Lang

JM

If I can pass the physical, I'll sign up as well. pl

Babak Makkinejad

All:

A link from IEEE Spectrum on the technical aspects of the space elevator:

http://www.spectrum.ieee.org/aug05/1690

And the site:

http://www.spaceelevator.com.

Byron Raum

It seems to me that the problem that almost everyone seems to happily ignore is that if someone climbs a rope, the thing at the top of the rope gets pulled down a little. Depending on the mass of the anchor, eventually the asteroid will enter the atmosphere. After the subsequent destruction of civilization, the Arabs will (again) emerge as the leading power in the world because they are already used to being bombed indiscriminately.

The two options to dealing with this problem are to either use rockets, or to send an equal amount of material down. However, I have yet to see any proponent of this device take these issues into serious consideration. They seem too obsessed with the free ride idea.

For the moon, we don't really need a device like this. It's much easier to lay a bunch of rail tracks down and accelerate payloads to any velocity desirable. Since there is negligible atmosphere, we can simply shoot stuff into space. The same applies to Mars, where one can almost walk into space; the highest mountain on Mars, Mt. Olympus (aptly named) has an atmospheric pressure of 2% of Mars atmosphere at Mars ground level - virtually space. No wonder the Martians were able to give Tom Cruise such a hard time. It's only we earthians who're stuck.

BR.

Babak Makkinejad

Byron Raum:

Not true; because the Earth and the Platofrm will be rotating the thread will remain taut.

qestenya

There is sci-fi book series "Red Mars", "Green Mars", "Blue Mars" about how a Mars colony project eventually outgrew domination by Earth government/corporate complexes. Part of the fight back was getting rid of the Space elevator that was seen as making it cheap for the Earth side to come in and out. So a mission was sent to take it out. When it got detached, it ended up being ONE carbon-nanotube cable long enough to go around the planetary "waist" with amazing whiplash, looping around the planet about 2.5 times. Parts of the cable change to diamond due to the searing heat.

John in LA

OK - the nanotubes and the snapback and all could probably be figured out.

But, judging by the amazing science being done by LA's Jet Propulsion Library, and the dismal, spam-in-a-can-Russian Locker Room -- type work being done by the "International" "Space" "Station", I'd say there's no point moving stuff (including people) into space.

For a hundred million bucks the JPL can throw a rover to any spot on Mars you want - there, it can take chemical samples, do all sorts of geophysical work, send down pictures for the kids' room - the works.

We should be sending digital probes into space - fleets of them. Not dragging humans, their food and their turds back and forth.

For the cost of destroying Iraq we could have seeded space with hundreds of probes, financed a Manhattan project for hydrogen and built 200 mile an hour trains between our cities.

The Space Elevator seems so 20th century....

Peter

Charlie:

Could there not be two elevators which move oppositely up and down in sync? They would meet in the middle and switch payloads(which would have to be relatively the same) thereby not changing the centre of gravity and so not requiring drastic orbital corrections?

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