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Space Elevator Update
TheMadReaper writes "The 2005 edition of the Space Exploration Conference in Albuquerque, NM came to a conclusion earlier this week. A large fraction of the conference was devoted to the Space Elevator. Surprisingly, there hasn't been much news coverage of this conference, perhaps because it doesn't have Space Elevator in its name. The most interesting fact I got from the conference is that money is really starting to exist in the space elevator world mainly thanks to the work of Dr. Bradley Edwards at ISR and at Carbon Designs, Inc. The strong nanotube talk was also more promising than last year."
In the interest of promoting more enlightened discussion, a lot of good information concerning space elevators can be found here.
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~ |rip/\/\aster /\/\onkey
How about creating a simulator for a space elevator? It would be great to mess around with values to see how possible this thing really is. The closest thing to a simulator I've seen is this but its sadly lacking.
http://spaceelevator.sourceforge.net, anyone?
Actually, if you have heavy objects impacting the Earth's surface, it's sort of preferrable to have them hit land, not water. Dust clouds and solid ejecta are unpleasant for the locals, but tsunamis are unpleasant for people who live thousands of miles away.
Aside from which, manufacturing spacecraft is perhaps one of the most industrially complex things we do. Trying to replicate that in a place more remote, and with far more environmental challenges than, say, Antarctica, would have gargantuan capital costs dwarfing the elevator. In fact, the only way you could probably get the infrastructure up there would be an elevator or something equivalently cheap.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
>Jeez, try to imagine the havoc if the cable comes loose
>from its orbital anchor. Thousands of miles of pure splat!
That's why you don't build it as a cable. You build it as a ribbon, with lots of surface area. If the ribbon snaps, portions high up in the atmosphere will burn up upon reentry. The portions of the cable that don't burn will flutter to the ground - think tickertape parades.
"A 40,000mm bridge is a 40m bridge. That's less than 120 feet. People have built multiple KM bridges long before now, the new Millau bridge in france is 2.5 KM in length."
Is it made out of carbon nanotubles or anything with the strength it would take for a Space Elevator?
No, so it's not in the same class structurally.
Your objections are very leaky.
It is a single point of failure. If any one of the millions of potential problems with a space cable turns out to be a show-stopper, the whole investment is lost.
It's possible to "prove" the space shuttle can't fly based on the number of parts and the failure rate in those parts. Yet it flies. It isn't like we've spent a fraction of the GNP on it. This argument comes down to "I don't think it will work because it seems complicated." It's actually much simpler than riding a bomb into space which is what astronauts currently do.
The benefits are small. The energy needed to shift a payload from the bottom to the top remains the same with or without the structure. The amount of money and energy spent on building the structure needs to be recovered in improved efficiency, and that seems unlikely.
This is just wrong. The benefits are huge! This would reduce cost to orbit by orders of magnitude. When you put material into space, you're not paying for the energy. It actually doesn't take all that much energy to put something into space. The calculation is easy. It's about 60 million Joules per kg (1/2 mv^2 with v=escape velocity). You can take a day to lift (which is 86400 seconds). That gives you about 700 J/s (which is the same as 700 Watts). It's the same energy you need to run 7 100 Watt light bulbs for 24 hours.
All of the investment is up front. There is no incremental benefit to this - the elevator does not become useful until it's complete. Any return on investment (including to governments in the form of kudos or re-election benefit) is delayed until long after completion of the project.
This objection is correct, but trivial. Edwards and Westling, the only ones who have done a realistic design study, put the cost at around $10 billion. That's less than the NASA budget for 1 year. That's much less than building a successor to the shuttle. That's factors of several less than the defunct superconducting supercolidor, and similarly less than the space station. Heck, Bill Gates could in theory build it for fun. Given the international nature of the problem, issues about security, the need for some additional bits of engineering/research, it is a government project. But not an outrageously expensive one.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Well, if you're below geosynchronous orbit, but more than a few kilometers above the surface, things are going to get hot when you re-enter the atmosphere. You'd want the heat shield.
If you're at geosynchronous orbit, you'll stay there, and you won't need the heat shield.
If you're above geosynchronous orbit, you'll get flung out into space with a delta vee somewhere between 0 and 3 km/second. Again, you won't need the heat shield.
Well, it's not as if you're at orbital velocity at low altitudes, but there is a nontrivial amount of energy you've accumulated.
For instance, a 80kg person who is 100km up the space elevator has accumulated ~80MJ of potential energy; this is a nontrivial amount of energy that will be dissipated as heat over a very short period-- the vast majority of it in a couple minutes.
I don't know the appropriate constants offhand (surface area of a person, etc) to calculate temperature under these thermal loads, but i can throw out a few numbers:
80MJ = 19 megacalories-- enough to raise the temperature of 190 kilograms of water by 100 degrees celsius.
80MJ = enough to run 450 standard home 1500W space heaters for the 2 minutes of heating.
So clearly, thermal considerations do matter for jumping from 100km.