Slashdot Mirror
Space Elevators Going Up
MikShapi writes "CBC is running a new piece on the Space Elevator. Nothing dramatically new, as we're all still waiting for one of the many Carbon Nanotube research centers to announce they reached the famous 100GPa red line from page 10 of the NIAC Phase 2 Report, thus obtaining 'unobtainium' [pun intended], the material necessary to build the Elevator. The report predicts this will happen during the course of the next two years or so. It's then that the fun really starts - A REAL all-out space race, open to everyone with will and a national budget, winner probably getting to own space [read last paragraph]. In the meanwhile, we can all spread the word, discuss, debate and brainstorm every nook and cranny of the program here on Slashdot, and give Edwards a shoulder by giving the program every bit of mass-exposure we can."
Getting 100 GPa for carbon nanotubes composite is one thing. Getting 100 GPa on a 100000 kilometers carbon nanotube composite is another.
I'm more interested in the length of the nanotubes than in their strengh since increasing the strengh is quite easy (basically all we need is to increase the fraction of carbon nanotubes in the composite) compared to increasing the length of the composite.
Iraq: war to save the U
I was at that NIAC conference a couple years ago when Brad Edwards presented his Phase 2 results and I have to say this was one of the most inspiring things I've ever seen.
Listening to him go through all the numbers and technical details you're left not only with the amazing scope of the thing but the feeling that, ya know, we might just be able to build this thing!
G.
Im constantly amazed how optimistic some people get about a space elevator. The main post and a lot of things other people are saying make it seem like they think technology is the deciding factor in whether or not one will get built. The only reason nobody has really spoken out against the idea is the average person thinks the scientists are smoking some good crack on this one.
This isn't a harmless piece of cable we're talking about. The real barrier is going to be whether or not it'd be dangerous if it breaks or if it's cut. If it'll burn up and IF the burnt nanotubes aren't dangerous then maybe there will be a snowballs chance in *$#@ that the public will ok such a project. You can be guaranteed that if it's dangerous though that everyone will just assume that it will break or be broken intentionally.
Warren Buffet often argues that since he is more productive than average, it's better for him to put his money to work than donate it to the needy. Once he dies, the argument goes, the money (a greater sum due to compounding) can be distributed. Take any discovery expedition - Columbus, Cortez, Polo - figure the aggregate value gained vs. the actual cost. This is the principle of investment.
One thing I really question is the claim that there will be or can be only one final winner in "owning" space. I'm sure there will eventually be wars and such but dominance by one group doesn't mean exclusion of another. There are times where one group in a particular realm is the "king of the hill" but often there is room for other players too, without the help of that "king".
...the 100 GPa number sounds ridiculous.
For context: the most common type of structural steel currently used has a yield strength of 350 Mpa. 100 GPa is 285 times stronger. And stronger isn't enough, it has to be dependable and resistant to cyclicle loading and fatigue, which isn't easy to quantify, especially under such unusual conditions.
To suggest that this can be achieved in a couple of years sounds silly to me, considering whatever material used would a lengthy term of testing and a proven track record before sinking billions of dollars into it.
Unless it breaks, it can't tip over. It's like hanging a yoyo from your finger. There's no way the string is going to tip over onto your hand.
I'm not the least bit concerned about the carbon nanotubules. I'm still trying to figure out how their going to ATTACH the damn thing. All buildings are essentially resting upon the Earth. This thing can't rest, it needs to be attached. For a cable this long, a "stupid hurricane" could set up a vibration is going to build to the point where the whole thing starts "walking" across Columbia.
Don't blame me, I didn't vote for either of them!
The only problem is that the same nanotube technology that would enable a space elevator will also enable a reusable single-stage-to-orbit spacecraft capable of putting mass into orbit at a much lower cost.
Just to pick some numbers:
Space elevator: $5B each, one 4 ton payload per day
Nanotube composite rocket: $.1B each, one 8 ton payload every two days
In other words, it will never happen.
The site doesn't actually run through the numbers or mention how long this recovery time would be. The logic does make sense -- if the tether becomes slanted relative to the surface of the earth (my objection), then by definition there is a lateral component to the centripetal force on the tether, which should allow the sky station to steal some angular momentum from the earth. at some unspecified rate.
The site doesn't actually run through the numbers or mention how long this recovery time would be. If any physics mavens are irritated enough by my parent post to actually run the numbers, I'd be genuinely interested in seeing the solution worked out.
There are some pictures of real carbon nanotubes in plexiglass containers available here, taken with my crappy digital camera at LiftPort.
Cool story: at one point some of this material, which looks more or less like soot, spilled onto the flat, seemingly smooth table top. After wiping it off, there was a permanent black smudge left on the table top that no amount of scrubbing would remove... some of the nano-scale CNTs had slipped down into the microscopic grooves and divots on the table surface!