I don’t deny the very serious safety problems, Sam Stone. I also don’t short the extreme problems of leaving nuclear waste anywhere here on Earth.
That having been said, I add that I’m afraid that the whole topic of sending our radioactive waste into outer-space via a space-elevator qualifies as a hijack of the thread. I only mentioned the possibility as an enormous cost saving and as, in my opinion, a safety advantage. 
I like a good hijack. The “Should we or shouldn’t we ship nuclear waste into space?” issue is a minor hijack compared to the “Does the sun have feelings?” hijack which seems to come out of left field. I’d like to address them both.
It seems to me that if we could contain the waste in some sort of super-secure container and lift it up via the space elevator and dump it into the sun, that woud be a pretty effective solution to the problem. The main concerns? On the way up the elevator what happens if a jet/terrorist bomb comes along and blows up the car high in the atmosphere? Is it possible to create a container that could contain the waste safely even in such an event? So that if it comes crashing down into the ocean it is still secure and can be recovered and there is no chance of the waste being released into the atmosphere. Once to the top of the eleveator the container could be put into an unmanned ship that travels to and from the sun using a solar-powered ion engine (relatively cheap propulsion) and releases it’s cargo when it gets close enough to the sun that it will fall in, then it returns to earth to get more waste (nuclear or any other kind). Seems like a good plan to me. Securing the elevator seems to be the biggest problem.
How hard would it be to secure something in the middle of the Pacific? Just destroy anything that gets within a hundred or two miles without clearance.
Now as far as the sun having feelings, I’ve never heard that theory before. I’ve heard the Gaia theory, and a couple competeing theories about Super-Organisms emerging from the interaction and memes of many people, but all of those theories were ways of describing emergent properties in systems that were filled with obvious life. The sun exists at a temperature that is far too hostile towards life as we know it.
I suppose it could be possible that there is some system in the sun that gives it awareness, but it does seem unlikely. What would we expect to find as evidence if this were true? Even if it were to be a living entity, the amount of radioactive waste we would send into the sun would equate to not even a mosquito bite. The Sun is something like 109 times the size of the earth if I remember correctly. The total volume of waste compared to the total volume of the sun would be .000-add a shitload of zeros-01
I can’t imagine these minor amounts of waste would be detrimental to the sun - alive or no.
DaLovin’ Dj
Nah, the easiest solution to waste is to slag it into glass or embed in concrete and then drop it into the ocean at a subduction point where it will be drawn back under the crust eventually.
Larry Niven wrote a short article that mentioned that idea, but he dismissed the idea in favour of making waste radioactive material into legal tender (the idea is that you’d be so keen to get rid of the stuff that the economy would experience a massive boom).
So what happens if we dump radioactive waste into, say Kilauea Volcano? Will it just get melted and then spewed back into the atmosphere in a matter of days?
Hey, that’s a good idea… t’hell with the space elevator, let’s just build Star Destroyers!!
Anyway…
Wasn’t the scramjet supposed to replace conventional Earth-to-orbit launches? From what I’ve read of those projections, it would’ve slashed costs on launces dramatically.
Further, something I haven’t seen mentioned in this thread… just how much mass is this thing going to take up, anyway, and is there enough excess material on the planet to do it? A twenty-foot wide cable multiplied by 60,000 miles…
In the Mars trilogy they got the material from nearby asteroids which they moved into orbit and robot mined them for the neccesary materials.
Of course, I don’t think moving an asteroid into earths orbit is the best idea (never mind one that could ever gain public support). The scramjet program turned out to be alot harder than they thought. Last I heard it got canceled. I may be confusing projects here. I aint got time to do a search right now. I’ll find it later if no one beats me to it. As of right now the new launch technologies department is looking pretty dismal.
The best idea I’ve heard are launching the ships using solar powered lasers. Some great research has already been done. I’ll find those links later too.
DaLovin’ Dj
About 1 cubic mile VOLUME of material. Not much when you think about how much concrete is used in highways and roads and stuff.
After a couple of years of reading the SDMB, here’s a thread that is finally getting me to open my big mouth.
DaLovinDJ wrote:
I’ve been considering the question of transportation to orbit for a few years now, and one of the main obstacles to large-scale systems like a Skyhook (space elevator) is that the demand for its capabilities does not yet exist. Currently, there is a market for launching something on the order of 100 tons of stuff to orbit per year. The Skyhook mentioned in the article (which is not possibly going to be built in 6 or even 15 years) could put up thousands to hundreds of thousands of tons per year. Until you can prove (or reasonably suggest) a demand for such throughput, no rational financier will put up the money to build such a project. I haven’t seen the business plan mentioned in the article, but the business plans of most advanced space launch concepts tend to be simplistic and unrealistic. Which is unfortunate and a bit depressing, because so many of us want to go. But one of the problems is of the chicken and egg nature: There’s not a high demand for putting stuff in orbit (partially because of the high cost of getting to orbit), and without a proven demand, no one will spend the money to reduce the cost of getting to orbit. 
(Note that I’m mostly ignoring government-sponsored work, but I do so on purpose: I don’t have much hope that anything good will come out of that sector.)
Unfortunately, given the events of Sept. 11, the likelihood of such a mega-project being built has gone down even further, I think. If people are scared of building skyscrapers that are potential terrorist targets, who wants to build something taller than the sky itself?
As far as technical questions go: As others stated, the tether would mostly fall down, not wrap around the earth (although part of it would stay in orbit, and who knows what might happen to it over the course of decades). Some proposals suggest leaving a clear area about 20 miles to the east of the base station in case it does fall. Sorry I don’t have a technical ref handy. I’ll try to dig them out of my files.
Mighty Maximimo is right on the spot – having one ton of millimeter-long ropes is not the same thing as having one ton of a single multi-kilometer long rope. To get the material properties you’d need, each thread in the rope would have to extend the full length (100,000 kilometers or whatever), and no one is coming anywhere near making such a long nanotube. Mixing shorter ropes (eg. millimeter-length) into some kind of composite material has not, to date, produced drastically improved material properties and theory suggests it won’t.
AndrewL wrote:
You don’t have to clear everything out of LEO, but some things would have to go. And it may be possible to have the Skyhook do a little ‘dance’ to boogie itself out of the way of incoming objects (big ones, that is). There are also designs for tethers which would provide a large degree of safety in the case of a micrometeorite strike. Check out Tethers Unlimited, Inc for details on their Hoytether.
You can plot a trajectory, certainly. But as I and othes have noted, to place your payload into that trajectory costs you. It costs you in terms of imetus, which has to come from somewhere. At some point, you have to throw away a lot of reaction mass (and spend the energy needed to get it up to speed) to force your radioactive waste out of orbit. This is true even if you rely on big spinning whips (as in Schmidt’s space elevator novel The Web Between the Worlds) or magnetic launchers in place of rockets. Momentum transfer ain’t free. As I’ve said before – launching something into the sun is an expensive and difficult proposition.
I’m not saying you can’t put all the waste into orbit, but unless you shoved it somewhere it would all congregate at the “top” end of your space elevator. The Trojan points of the Earth-Moon system might be attractive, but that’s a quarter of a million miles away – you might as well dump it on the moon. And it’ll cost you reaction mass and energy to get it to either the Trojan points or the moon from the Elevator.
Heres what Nasa has to say about the subject:
http://liftoff.msfc.nasa.gov/academy/tether/spacetowers.html
That assumes that the top of the elevator is at geosynchronous orbit. If the cable is 60000 miles long, the top is way above geosynchronous, and is moving at about 15,000 mph with respect to a non-rotating Earth.
I was too lazy to derive it myself, but these guys claim that the escape velocity of a body is
root(2GM/R), where G is Newton’s constant, M is mass of the planet, and R is the distance from the planet’s center to the body.
Using 6 x 10[sup]24[/sup] kg for the mass of earth, at a radius of 60,000 miles (say, 100,000 km), and 6.673 x 10[sup]-11[/sup] m[sup]3[/sup] kg[sup]-1[/sup] s[sup]-2[/sup] for G, we get around 3 km/sec, or around 10000 kmh.
15000 mph is way faster, so at the end of the tether things can just be unclipped and they’ll fall into a hyperbolic orbit away from Earth to infinity - and beyond. There is no additional energy cost beyond boosting the object up to geosynchronous, in fact you can take energy out as it goes up to the end of the tether. When it gets to the end, it is being held by tension in the cable only, and so from the frame of the end of the tether the weight will shoot straight up away from earth, then coriolis will drag it westward.
As for the “wrap around earth” problem, if you lose the station at the end, you could just have explosives along the length of the cable to blow it to manageable chunks. Higher up chunks will leave Earth, middle height chunks will be in orbit and can be cleaned up later, and lower chunks will fall to the east of the anchor point. Given a big enough ocean, I think it would not be too terrible.
Finally, protecting against idiots who hijack jetliners may involve something like a 500 mile no fly radius enforced with military assets.
The fact that anything “above” the center of mass of a tether is actually being held at a lower orbit than it would otherwise move to (ie. it’s being dragged at a higher velocity than its orbit dictates) is one of the really cool and useful things about tethers. Douglips is right in saying that something at the 100,000 km high end of a tether would be flung away from the Earth if it let go. It wouldn’t actually leave the solar system, though – the Sun’s escape velocity is much higher than the Earth’s (it’s a little over 42 km/sec at Earth’s distance from the Sun). But there are lots of proposals out for moving things around the solar system by simply dropping them off the proper points of a set of tethers (which are not even necessarily attached to any planet, but may be in orbit about them).
Perhaps – but then how do all the travelers to space get to the tether? Take a cruise boat for a couple of weeks?
I see. Just have explosives line the length of a 60,000 mile cable. That is such a bad idea on so many levels I don’t even know where to begin.
Try. This is “Great Debates”, not “Great non-Debates”.
If you don’t like the explosives on the cable idea, how about we store a bunch of surface to air missiles with 18 gazillion safety interlocks east of the cable, ready to blow it into bite size pieces when Space Station Zebra goes Major Tom?
How about explosives in just one place, strategically placed so that when they go off, the outer chunk of the cable stays in orbit? Assuming the ‘cab’ of the elevator has some backup escape mechanism (rockets, parachutes, etc.) then you only lose the bottom N miles of cable. You could even have a large mass at the end of the cable whose job it is to fly off into space to keep the cable in a closed orbit around earth in case of this failure mode. You then have some space craft dock with some portion of the cable and re-string it.
Is it a better idea to just let everyone within 50 miles of the equator die?
Maybe the risk of the cable having a problem is so low that we need none of these solutions. There is certainly a risk involved in having explosives on the cable, or missiles nearby, or in a meteor strike, or any number of things. Perhaps we can actually talk about it instead of just throwing up our hands and calling our ideas ridiculous.
If you think my ideas are bad, please feel free to actually come up with some of your own.
I just want to point out, again (why does this loony topic keep coming up?) that a ground fixed space elevator is considered a joke in many engineering circles. Ignoring the requirements for magic materials, etc., is just isn’t going to be stable
It is not like swinging a rock on a string. The cable has mass, gravity is pulling on it- non uniformly. The Tacoma narrows bridge is nothing compared to what would happen.
No one ever produces a real set of formulas, a detail simulation or such. Ever. Guess why? Remember, for fantastic claims, it is the job of the claimaints to provide some proof first.
I keep asking over and over one simple question: What is the state of the system 1 hour before first complete hookup from ground to post-GSO?
(If you are going to challenge my post, please completely answer the above question first.)
The article that started this all, shows how silly things are. All engineering calculations show that the cable must have an exponetially increasing diameter as you get near the base. No matter how thin it is in the middle, the base is going to be huge. (And these calc.s ignore shear force.) Talking about starting with a thin cable and making it thicker is asinine.
Like I said, considered a joke among very knowledgable people.
I just want to point out, again (why does this loony topic keep coming up?) that a ground fixed space elevator is considered a joke in many engineering circles. Ignoring the requirements for magic materials, etc., is just isn’t going to be stable
It is not like swinging a rock on a string. The cable has mass, gravity is pulling on it- non uniformly. The Tacoma narrows bridge is nothing compared to what would happen.
No one ever produces a real set of formulas, a detail simulation or such. Ever. Guess why? Remember, for fantastic claims, it is the job of the claimaints to provide some proof first.
I keep asking over and over one simple question: What is the state of the system 1 hour before first complete hookup from ground to post-GSO?
(If you are going to challenge my post, please completely answer the above question first.)
The article that started this all, shows how silly things are. All engineering calculations show that the cable must have an exponetially increasing diameter as you get near the base. No matter how thin it is in the middle, the base is going to be huge. (And these calc.s ignore shear force.) Talking about starting with a thin cable and making it thicker is asinine.
Like I said, considered a joke among very knowledgable people.
Construction of a space elevator should be held off until Al-Queda and other terror squads are incapacitated. Last thing we need is a bunch of fundementalists hijacking Carnival cruise liners and plowing full steam ahead into the “Otis-Lunar-1”
I liked the nuclear waste idea. Here’s Tracer’s take on the subject:
Not likely.
The “super-cannon” Saddam Hussein wanted built would have been the biggest gun ever built in history. However, it would have had a range of only 1000 miles.
A 1000-mile-range gun would have to impart a delta-V to its payload of roughly 13,000 feet per second. To put a payload into low Earth orbit requires a delta-V of over 25,000 feet per second. And to put a payload on an Earth-escape trajectory of any kind requires that you impart “escape velocity” to it, which is over 36,000 feet per second. Detonating enough explosive to impart this kind of delta-V would tear your gun apart before the payload even left the muzzle
I’d think the only thing neccesary to prevent the entire thing crashing down to earth, assuming the CoM is beyond geosynch orbit, is to detatch it at the base. Centrifigal force would then draw the entire mass, station, cable, and all, out of orbit. That would effectively eliminate any ground-destruction from something like a plane hitting the cable (Maybe 6 miles up at most?). The only large-scale ground devestation would be caused then, most likely, by an explosive placed inside one of the elevators, and even then it would take an extremely powerfull explosive. The cable is extremely strong if it’s holding a station in place, and there is no atmosphere outside the car to transfer the blast (And possibly none inside, depending on whether the cargo needs an atmosphere or pressure). Plus it would have to get past any security measures, and a bomb that size would be very hard to hide.
I’m kinda curious about the base, though. The only “working” design I’ve heard of involved a 6-mile high man-made mountain for a base. Certainly big enough to serve as an anchor, and very hard to damage or destroy on accident or on purpose, but… That seems too big to be workable.
Ok. I will breifly indulge in the fantasy that this thing can be built. If this thing fails, explosives will probably not help since all they will do is break it up into peices. They won’t vaporize it. Those peices will still fall to earth and break stuff. Remember the thing is 60000 miles long. If even a “small” 1000 ft long piece lands in a populated area, it would cause a lot of damage.