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Notes From 3rd Annual Space Elevator Conference
colonist writes "The Space Elevator: 3rd Annual International Conference was held recently. Blaise Gassend, a PhD student at MIT, took notes. The main obstacle is still the material: transferring the strength of the nanotube to the ribbon. Other topics include: the nanotube tether Centennial Challenge; Elevator 2010, a challenge for a 250 kg climber to climb a 16 km tether; objections and refinements to Bradley Edwards' design; non-equatorial space elevators; replacing the term 'space elevator' with 'space bridge'; testing the space elevator material on cable cars; science; defense and economics."
This will change everything. Transporting to space will be (relitive to rockets) DIRT CHEAP. Props to them for their vision and their crazy idea that just might work.
I think that it should be taken into consideration that almost every major project of construction was deemed impossible. Very good examples of these are the famous Golden Gate Bridge and the EuroTunnel. Everyone said it was impossible, yet they were completed. As technologoy in this area continues to develop, I think that this may be able to become a real and practical idea sometime down the road. It may not be possible now, but in ten years, who knows?
Blaise Gassend's page mentions Andrew Price's list of alternative names:
space bridge
space way
space rail
'Space bridge' got the most approval from the audience.
Forgive my ignorance, MEMS and Nanotech has fascinated me for a while, but I don't know enough of the math behind them to tell if this is true. My grandfather, rest his soul, once told me of something called the Sailor's Rope Rule, which effectively says that the weight a rope can support is diminished by its length. Thus, a 500 lb. rope might support 500 lbs when there's less than a foot or so in length between the pully and the weight, but might only support 250 lbs when there is a good 100 ft. or so... The actual support degradation of course depends upon the width of the rope and the material the rope is made of.
So what I'm wondering is, does the same apply to the weight supported by nanotubes and other molecular chains. I figure it has to be less of a degradation due to the ionic bonds involved, but it would seem to me that, unless some Quantum rule is involved dealing with extremely small-scale weight supporting chains, that they might never overcome this problem due to the sheer thinness of the tubes, chains, etc. It might be extremely strong material, but if it's width is only a few atoms wide, wouldn't this material be, at least in single lengths, more or less useless by the time it got to a respectable length? This is, of course, excluding bundles, which make the most sense, I'm really just curious if the same rule applies to nanotubes as applies to rope.
-The Libra
"Please be patient--The future will begin momentarily."
The Spaceward Foundation is creating the Elevator:2010 program:
They have to be to hold the darned thing in place. I doubt something as feeble as a passenger plane crashing into it will do much damage other than making it vibrate for a bit. I don't envy the people on the plane, though.
Stick Men
I recall Arthur Clarke pitching the initial concept for a Space Elevator some time back, and revisited the idea in 3001 : The Final Odyssey - in which he depicted planet Earth having a fully functional ( four actually ) space elevator system; which facilitated a subset of human civilisation living in low earth orbits in reduced gravity - thus invoking presumed benefits of doing so.
Anywho. He spoke a couple years ago, subsequent to 3001's release on how at the time of writing, such a feat was nigh on impossible at this stage - as the materials to construct the 'elevator' were yet to be developed. Until now. The carbon molecule Buckminsterfullerene ( C60 ), also known as 'Fullerene', is supposedly strong enough to actually make such a concept a reality - which is in part the reason the space elevator was hurled back into the limelight of late.
I think its a fascinating idea - which until we develop propulsion systems beyond the primative scope of the 1,000+ year old firecracker concept, certainly seems a more elegant way for the species to venture into Space more regulary. Or, at the very least, be the catalyst for what could perhaps become the initial stepping stones to establishing a permanent presence in space which will hopefully later lead to space initiated launches.
Following up to myself: here's a link to a page about a variety of tether-based designs and experiments: Advanced Propulsion Concepts.
you're forgetting the big upside of the space elevator: the owners of the space elevator can drop shit on you from space! heavy things like big rocks, kitchen sinks, and 2000 pound gps-guided bombs. and let it be clear, there is no defence against kitchen sinks falling on you from space. we're talking afforable space based weapons platforms. the weapon of choice of the future may be raindrop-shaped ceramic projectiles with spent-uranium cores, raining unstoppably from above and smashing their way through tanks and into underground bunkers, or sinking an aircraft carrier battlegroup.
the military of the country that builds this wonderous weapons platform will let see to the safety of the tether, you can bet on that.
Simple - have more than one tether.
You could have say 5 tethers, anchored in a pentagon shape on the ground, where the sides of the pentagon are maybe 100km long. Same sort or arrangement at the top - they all connect to the same asteroid, just a little distance apart.
If any one tether is destroyed, the rest will be enough to hold things together until the broken one is replaced.
Meanwhile, under normal conditions, you have 5 times the capacity.
Yes I know it'll cost more, but if you want redundancy, you gotta pay for it.
But is it really that less wasteful? Launching into orbit takes energy in 3 forms:
- Gaining altitude: You still need the same energy in the space elevator
- Gaining orbital speed: This will have to be compensated by propulsion at the top of the elevator, but is also the same as in a regular loss.
- Atmospheric drag: This will be less because the cargo can move slower than a rocket. But still, must of the dynamic pressure experienced in a rocket is during the first minute of launch. After this, there's not much left.
I guess most of the energy during conventional launch is lost because propellant has to be carried up. However, I think you will still need a fair amount of propellant at the top of the elevator to compensate for the loss of speed due to cargo being lifted up. This propellant somehow has to be transported up too, costing a lot of propellent itself. So will this really be much less wasteful?
The energy has to come either from A) the lifting force of the climber or B) from the elevator itself. Looking at it as an angular momentum problem, I believe it's B, from the elevator. But by the same accord, any mass that decends the elevator will speed up the rotation, so they'll only have provide boost for the mass that stays up.
On a side note, I wonder how much drag the atmosphere produces? How much energy will need to be spent to just keep it up?
Consider the ultimate composite nanotube material -- stiffness 10^12 Pascal, yield strength 10^10 Pascal. So at-yield, it stretches 10%. The stored elastic energy density then is 5x10^9 J/m^3. This is roughly the same stored energy as an equal volume of TNT (4.1x10^9 J/ton)! Yikes! You can think of the deployed nanotube bridge as a gigantic PrimaCord detonating system.
Simple enough to fix, you set the center of mass of the system, unloaded, to be slightly outside of geosync. That means that the system wants to fly off, but you keep running mass up to counteract the effect. If you don't want to run something up at the moment, you simply tie the tether down with a mass at the bottom, such as the oil type platform they propose.
I don't read AC A human right
Most plans I've seen for one of these involves starting construction on a second using materials lifted by the first.
Makes sense, as the second one would cost 1/100 of the first, doubling your capacity and reducing the chance of a breakage making you lift replacement materials by the expensive method again...
I don't read AC A human right
Current proposals for implementation of the Hans Moravec's original design rely on a hypersonic air-breather of advanced aerodynamic design like the Boeing DF-9 (that exists only on paper).
Can /. readers think of anything likely come along in the near future that could take
paylods to 100km and mach 12?
Probably the same thing that is driving the bureaucrats to make all this noise about space elevators now.
A key to the Rotovator(tm) is getting hub mass in place to keep it out of the atmosphere while it picks up mass from 100km@mach12 -- but that mass can be any old space junk -- at least at the hub where it counts the most for high strength materials like carbon nanotubes. However, you can do a Rotovator(tm) with off-the-shelf commercially available fibers and still have a factor of 2.
Nice thing about Rotovators(tm) is that they can be built with much lower capitaliztion over a much shorter period of time using existing commercial materials. All you need is a bunch of mass orbiting near earth, some quite-doable tethers, and sufficient manuverability and speed in the atmospheric leg to hook up with the tether as it reaches the nadir.
Seastead this.
Uh... I started using the word "tether" with the first message in this thread. Why would I have an objection to the word?
The Earth isn't part of the system. The tether as a whole is in freefall and the low end is not fixed to the Earth... in the most practical designs it's actually on a floating platform or terminates outside the atmosphere. The part of the tether that's in contact with the earth is the thinnest and weakest part of the whole system, and can't be used to tug the whole structure around like a, um, milk jug.
The tether can get energy back from tourists returning to Earth. So if your main traffic is tourists going up and down, the tether energy is easy. Another fun trick is that if you had a series of tether in LEO, GEO, and Lunar orbit you could send stuff to the moon and send moon rocks (or other stuff) back to the Earth without needed to add energy. You just keep the total mass going each way balanced.
Because of this, orbital or lunar tourism will not take much more energy than suborbital rocket rides. So we should see it within the next 20 years.
I have a site, spacetethers.com that has info and a Java applet tether simulator. There is also lots of info at tethers.com
Not to knock you off your "Christian mythology" highhorse but since the Tower of Babel story is in Genesis, it's from the Torah and technically rooted in "Jewish Mythology".
Unfortunately, while it's fashionable to throw around terms like "Christian mythology", calling a Jewish story made up will probably just get you labeled as an anti-Semite. Too bad anti-Christian statements aren't treated with the same revulsion as saying Hindus, Jews, Muslims and Buddhists are all living in a fairy tale.
Blaze a trail to the New World
To quote the original Bradley Edwards paper "The Space Elevator",
"The segments of the cable in Earth's radiation belts will experience less than 3Mrad per year (energetic electrons and protons) [Daly, 1996]. Studies of epoxy/carbon fiber composites (epoxy/nanotube composites would be expected to be comparable or better) have found them to be radiation hard to greater than 10^4 Mrad [Egusa, 1990: Bouquet, 1979]. This would allow them to survive more than 1000 years in the expected environment"
To survive the atomic oxygen, it was proposed the ribbon be coated with a thin layer of metal (aluminum, nickel or gold) between .02 and 20 microns thick. This would only be applied where atomic oxygen is a likely hazard
Finally, it is understood that the ribbon will degrade over time despite best efforts, due to radiation, electric discharges, micrometeorite damage, fiber/epoxy failures, etc. They talked about a plan to periodically inspect, and, if necessary, reinforce the ribbon with additional strands of material.
somehow dislodge the asteroid from orbit
Why did the scifi writers think that an asteroid would be used as the counterweight? There's no reason for that. Carbon is cheap - moving an asteroid is not. Just make the cable twice as long, and use the rocket remains as the counterweight. Easy enough. Can we propagate this idea? Here it is again: no asteroid counterweight!
It's quite reasonable to take terrorism into consideration when designing a structure.
Thankfully, the design of the structure takes it into account for you. How nice!
After all, consider this:
The structure is 100,000 miles long. What's the highest that someone could conceivably hit? Assume they have aircraft - so that's what, 30K feet, or 6 miles? So they've just severed the bottom 0.006% of the cable? This would do nothing to the cable itself. They would spool down 6 more miles, sigh, and no one would ever even know it happened. A terrorist organization might try it once, and then they'd realize they're wasting their money.
The only real threat comes when terrorists have orbiting satellites or ICBMs. I think we'll have other things to worry about then...
The other thing to consider is what precisely is the cost of losing the elevator. One might think that it's $10-15 billion, but it's not, unless you're stupid. The first thing you would do is send up another elevator, and leave it in orbit at GEO.
Then the cost of losing one elevator is high - probably a few million - but not that high. After all, once the first elevator has proven itself, putting up other elevators should be the highest priority. Eventually a meteorite swarm will destroy the elevator, and you don't want to be cast back to the dark ages of large exploding cylinders.