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Going Up?
jmiyaku writes "The National Post is reporting that NASA has given a Seattle company a $570,000 grant to continue its investigation into constructing a space elevator. Coupled with some production-grade technology from a Japanese car company (carbon nanotube composites), this elevator could be a reality within 15 years..." The Highlift website has some more information.
If you build it, they will come...
Strange women lying in ponds distributing swords is no basis for a system of government.
Well, Yucca Mountain leaves a whole lot to be desired. I suppose the best thing to do would be to shoot the radioactive waste into the sun. You could lanuch self-guiding ships full of the stuff straight into the sun...the sun sure wouldn't care. But how do you get the stuff in space safely?
Perhaps this space elevator? I think it should be safe(r). Use the elevator to take the radioactive waste top the space station, then build a craft to launch the waste into the sun. No more radioactive waste problem! And it would probably be cheaper than the current proposed solution, plus it would be really great for the space program and scientific development. Is this a good idea?
Lawrence Lessig is my personal hero.
http://www.highliftsystems.com/faq.html
This talks about what will happen if it falls, what terrorists can do to it, etc. It actually seems fairly honestly done, not all marketing-speak.
Also what about the risk of it falling down? An orbital tower will wrap about the earth more than once if it falls. The description in Red Mars was particularly though provoking.
I used to think that this would make space elevators impractically dangerous. However, this turns out not to be the case.
The energy gained by the falling cable will be at most its gravitational potential energy, which is within a factor of two of conventional high explosives (per unit weight). Pick a maximum yield on impact, and you have a maximum cable weight. Use a thin enough cable to meet this weight restriction, and you have an adequately disaster-proof elevator (it'll make a mess, but not wreck the world's climate).
My own calculations with a 10 kT yield/cable weight came up with something that could reasonably be used for space travel and would pay for itself if you could keep the cargo moving.
The biggest problem is figuring out how to move cargo fast enough. I'd be leery of having induction motors mess with the cable itself, and if its a nanotube bundle they won't conduct in the right direction anyways. Winches are much too slow. Sheathing the cable with metal would only be practical for a very thin layer, which ends up being too thin to support the required currents without boiling off (I think). It's an interesting design problem.
> It seems to me that this project will never work. There are to many forces at play. The elevator would probable snap in half do to all the strain. If we did manage to build it there would be a HUGE problem: Earth's rotation would slow down, forcing us toward the Sun. Imagine the Earth as an ice skater in rotation. The person keeps their arms close to their body to rotate fast. What happens when the person's arms raise away from their body? They slow down. It is a simple concept of centripetal acceleration. The elevator would act as an arm of the Earth, thus causing it to slow down.
Wow. There are so many scale errors here it's hard to tell where to start. First, What strain exactly would "snap the elevator in half"? It's a ribbon, and while it's certainly possible to break the ribbon, it's not likely to happen under normal operation, and the design specifies that they'll set it up in a location that minimizes the likelihood of high winds or lightning. Second, "Earth's rotation would slow down"?!? You can't be serious with this. The mass of this thing is so much less than that of the Earth that the slowdown would be indetectable with the most sensitive instruments we have, if we were actively looking for it. To take your example of the figure skater, imagine her spinning, then letting out a one inch long piece of the finest hair you can find. How much do you think she'll slow down? And last, why exactly would slowing Earth's rotation cause us to head for the Sun? The day would get to be more than twenty-four hours, but the speed the Earth moves around the Sun (that's "revolution", not "rotation") would not change in the least.
Go buy a book on physics.
Virg
Where to begin???
Point 1: Neo to attach to. Unnecessary. You can achieve the same thing with a really long teather and a 1 kg weight on the end. Did you not notice that the cable was 100,000 km long, when geosynch orbit is only 36,000 (miles or km I can't remember, but even if it is miles that would make it 57odd thousand km up, far less then the 100,00 required) the extra thousands of km are used to provide leverage and a decent ratio for the mass to be lifted.
Although I am curious to know what you mean by strong enough. All you need to do is get an object, in geosych orbit, move it to an outer orbit but keep it at the same angular velocity (how long it takes to orbit the earth) and the resulting centripetal force can be used to pull against when pulling up mass. 'Strong' neos aren't needed, a collection of cotton wool would do it, if there was enough and it was far enough out.
Point 2: Constant height. Not actually necessary, the water level is pretty flat (aside from tidal variations due to the moon and the sun) BUT the cable is under constant tension thus would forgive a certain amount of play. In fact the cable has to be at over 5 tonnes of tension at the base to be able to lift the mass required.
Point 3: Energy required for lift. Actually you are wrong again, the energy required is less. When you use a reaction engine fully half the energy required to boost you is wasted throwing mass out in the opposite direction. HOWEVER along with this is the fact that they are going to be using lasers to drive photovoltaic cells to drive electrical motors, and this could (in theory) be purely sunlight driven.
Point 4. Location. The ocean isn't too bad, a simple cargo ship deliver the cargo and it lifts. Sure its not rail or lorry but its good enough. Most of the oil the US needs is shipped via tankers, why can't a few satelites?
Point 5. Anti-gravity. (Ignoring the racist angle) this is an unproven experiment, and it should be noted that 2% is a little different to lifting the item into orbit.
As an aside, the cable itself will weigh in at a stunning 750 tonnes. Of that 480 tonnes (metric) will be above geo-synch orbit (assuming 36k km or should that be Mm???) and not likely to crash down.
I applaude them, but hope it does all work even though I have my doubts...
The tensile strength of the cable needs to be huge.. 7.5 kg per km, and that needs to hold around 270 tonnes, its a hell of a challenge....
Z.