15 replies to this topic

[PaulH]

For those of you who haven't heard, there is a new space elevator company, High Lift Systems. They are betting that mass produced carbon nanotubes will be readily available within the next 10 years, making a space elevator both economically feasible and desirable.

Either way, I'm excited about space again, because despite all other indicators aside, space migration might actually happen en mass in my lifetime (assuming no life extension benefits).

Paul

Planet P Blog

[pulsar]

hmm i was only 7 when this thread was made ._. they haven't made one yet and i doubt they would in 3 more years :(

[niner]

Ha ha. "Prediction is hard, particularly of the future." (Berra) I think we'll have a space elevator some day. It sure as hell won't be in three years though. It will probably be technologically possible before it's financially possible. It will have to compete with alternatives like chemical rockets and space planes, and there will need to be a compelling economic model, or else it will only be done by a government. Maybe a non-democratic one, like China, since they can take the long view, not having to worry so much about getting reelected.

[A941]

I wonder if space-tourism will be boosted through that?

Would it be possible to travell to the moon with a space elevator?
No, not with one and the same, but would it be possible to leave earth with one, be "tossed" of in a Space-shuttle-bus and catched with another elevator-station so that you could descent safely to the moon surface?
Or could you land on the moon without such aid?

[Clifford Greenblatt]

An alternative to the space elevator that I have been thinking of is a vacuum shaft. As far as I know, the Cape Canaveral launching site is not far above sea level. A much higher launching elevation would save a significant amount of rocket fuel. A long shaft deep into a mountain could permit magnetic acceleration of a rocket for a few miles before burning any rocket fuel at all. The thinner atmosphere at the top of the mountain would also reduce air resistance. A 50 mile high pyramid with a magnetic propulsion shaft could get the rocket to a very high speed before burning any fuel. At a 50 mile height, the atmosphere would be much thinner than at sea level. The shaft could be at near vacuum pressure to greatly reduce losses due to air resistance. However, I do not know how the economics of a 50 mile high structure would compare to the proposed space elevator, which would be more like a very long and strong rope into deep space.

[YOLF]

Why build up when you can build down? I think building into a mountain would be best so long as there was stability. Mt. Everest is less than 6 miles high, a 50 mile high pyramid would be like building 1000s of mountains and probably take a considerable amount of time to build. Building a mega city from scratch to be like a pyramid with many structures supporting larger structures to contain the vacuum tube at the center would be necessary to have any kind of economic feasibility. I'd just dig as deep a hole as possible and then top it off with a conventional structure to get it a little bit higher. Better yet, build it into a mountain from some old mine shafts that could be used to load the shuttles. Initial vacuum or near vacuum could be achieved by pumping water melted from the ice cap into the tube which would be deeper (or just terminate into a much less narrow space at its depth) than the volume of water used and contain a drain plug. Vacuum generators could then be used to top off the vacuum and be powered by a series of hydroelectric turbines from ice melt and a bunch of nuclear reactors (lots of energy required to reach escape velocity) which would serve dually as the power for the electromagnetic propulsion. Near the tip of the pipe a high speed "vacuum damn" would be engaged just prior to another one opening at the top to release the payload thus preserving as much vacuum as possible. A series of these "damns" could be used to allow larger or smaller payloads and provide backups in case one fails to close. The magnetic system would continue post vacuum to ensure the change in air pressure wouldn't misdirect the payload. Much smaller rocket stages would then be used to achieve the 25,000+ miles per hour escape velocity required. Breaking inertia wastes a lot of energy.

It looks like all of the largest mountains are in east Asia, so it looks like it will be China, India, or Russia who will have the skill and best mountains for it. Though I guess having a high plateau is more important than peaks, so it it's probably a bit harder to determine where the best launch site would be. I could think of a few more unconventional means requiring much less energy too. Don't forget there are limits to how many Gs a human body can endure. I think that's why we have roller coasters. I imagine they boost bone and tissue density.

Oh, hey Cliff, check this out: http://www.longecity...00-mile-radius/

[taho]

I don't think it will be done.
But, it looks like we will soon have reusable, cheap rockets, so won't need to build one.

[YOLF]

One may come before the other but the tech will eventually need to be cheap enough for everyone to use it and that means cheap rockets and cheap escape velocity.

[taho]

First we must build incrediblly strong 40.000 km rope, that will not break when something hits it really fast..
Reusable rockets are childs play compared to that. Skylon looks promising. SpaceX is even closer. Falcon 9 will soon fly back to launch site and land there. Once that happends, every other rocket will become obsolete. And they are planing to build even bigger, better, cheaper rocket for a trip to Mars..

[niner]

It doesn't need to be 40,000 km. More like 100 km. That's high enough to be out of the bulk of the gravity well. If we could manage to build a space elevator, I think the cost of putting a kilogram of mass into low earth orbit would be orders of magnitude less than chemical rockets. It would make it feasible to construct significant structures in space. However, that isn't taking into account the cost of building the elevator, which might be $100B. If only we could claim that it would fight terrorists...

[PWAIN]

Sorry niner but that is wrong, you need to have half the rope outside of earth's gravity well to act as a counter or the whole thing just falls back to earth in a heap.

[taho]

It is not the height that is important. It's the speed, so that you stay in space. Things stay in orbit because they have just enough speed (7.89 km/s in LEO) so that they don't fall back or fling out. The 100 km height is important because air friction will reduce your speed and that will make you fall down. The higher you go, less air you have.
40.000 km from ecuator is a GEO orbit. This is where your orbit around Earth takes 24 hours to complete just as it takes the Earth 24 hours to spin. Anything in that spot looks like it is just sitting there.
Space elevator is a big rope that does not fall down, because it has a counter weight at that point with more "fling" speed so that everything stays in balance. To do that you "only" need that long unbreakable rope..

[YOLF]

It doesn't need to be 40,000 km. More like 100 km. That's high enough to be out of the bulk of the gravity well. If we could manage to build a space elevator, I think the cost of putting a kilogram of mass into low earth orbit would be orders of magnitude less than chemical rockets. It would make it feasible to construct significant structures in space. However, that isn't taking into account the cost of building the elevator, which might be $100B. If only we could claim that it would fight terrorists...

It does fight terrorism! More spy satellites and such things could be launched from it!

[niner]

Sorry niner but that is wrong, you need to have half the rope outside of earth's gravity well to act as a counter or the whole thing just falls back to earth in a heap.

Taho was right- apparently it needs to reach the geostationary orbit location 35,786 km (22,236 mi) above the surface. Well that sucks, doesn't it. I don't see this happening for a long time. I won't say never, but I don't think we have the technology or the will at the moment.

[Antonio2014]

I think the first space elevator will not be on Earth but on Mars or the Moon. It's easier. Anyway, I don't think it will happen any time soon.

[YOLF]

I'm all for doing a bunch of fundraisers to build one