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Space Elevators Are Possible

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Re: Space Elevators Are Possible

#51

Post by ohwp »

avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

Another problem never answered: Do we have the resources (funds and material) to create the amount of material needed?

Lets say the cable is 1m2 thick: 1m2 * 100000m (Kármán line) = 100000m3. Maybe this doesn't sound like a lot until you check the prices of nanotube-like materials.

Re: Space Elevators Are Possible

#52

Post by jccooper »

S4M wrote: post #41
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

How about making the elevator start in the North pole (or South pole) and go vertically from there. That way, we can be sure that it will never meet the trajectory of a satellite? Of course, it would prove harder to build it in those cold regions.

Impossible. It must be on the equator. Attaching a line from the ground to a large object in geosynchronous orbit is the essential plan, and GEO only happens above the equator.

Re: Space Elevators Are Possible

#53

Post by Crito »

shaneofalltrad wrote: post #36
ChuckMcM wrote: post #20

Earlier quoted context omitted.

I was going to bring this concern as well. I expect that in theory we could build a space elevator but I doubt we could keep it in space. Between space junk, meteorites, and regular gear flying around like GPS nodes, items in a non-orbit (which they would be in this configuration) will be hit with more than enough energy to destroy even the strongest materials we have out there.

I would also want to know the impact of a counter weight attached to the earth and it's effect on our ability to orbit naturally while it's drag is attached to even water. Could an impact on this force it into a spin around Earth creating Centrifugal force or something not studied before?

I'm not quite sure I am parsing your question correctly, but:

The Moon is yanking the Earth around, but even something that stupendously massive doesn't do much damage (the tidal forces are nothing to sneeze at.. but the 'wobble' caused by the difference between the Earths center of mass and the Earth-Moon barycenter (the point that the Earth and Moon both orbit) is negligible in nearly every consideration).

This would absolutely not be a concern.

Re: Space Elevators Are Possible

#54

Post by kamaal »

avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

I think you are essentially talking about a 'traffic signal' equivalent of space.

If launching satellite becomes cheap with space elevators. You are going to have absolute mad rush to launch satellites, any way. In any such situation, you will have a lot of satellite traffic up there and merely managing that traffic among satellites itself is going to be difficult.

But even if you discount space elevators, if cost of launching satellites gets cheaper by the day. At some point you have to worry about this satellite traffic problem.

Re: Space Elevators Are Possible

#55

Post by kamaal »

jccooper wrote: post #48
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

We already monitor very small debris (anything 1cm or larger), and move things out of the way if needed. The ISS moves about 6 times a year, mostly to maintain a very large margin. Orbits are quite predictable, and moving the tether around isn't all that bad--after all, it makes getting fuel to LEO altitudes cheap. Also, I would expect active sats to avoid the tether, and the presence of a tether will make removal of…

Also I guess any space elevator system will deploy a 'tether maintenance' activity every some interval with intermediate stations. There will be likely bots moving up and down the tether to keep it free from debris and other approaching objects.

Re: Space Elevators Are Possible

#56

Post by jccooper »

kamaal wrote: post #49

At the risk of appearing stupid, I just have few simple questions 1. What exactly holds the counter weight in position? 2. Such a long rope, which the article says is around 62000 miles, won't it function more like rubber band than function like a rope? Due to mere stretching/elastic effect? 3. I'm sure traveling 62000 miles is nothing like fuel efficient especially when you travel in the direction of highest frictio…

1. The counterweight is in geosynchronous orbit. It is "held up" by its absurd speed like any other satellite.

2. One of the reasons you need a very strong material. The tether will be in tension, but probably will have quite a bit of movement to it. The tether dynamics are not a solved problem.

3. Most plans suggest that power will be beamed from the ground to the climber, either as microwaves or visible light. Some plans might use a paired tether to carry electricity. In either case, no onboard fuel is needed, which us pretty nice, as that's a lot of weight you don't have to pull against gravity. There have been several competitions in this area already.

Re: Space Elevators Are Possible

#57

Post by jccooper »

ohwp wrote: post #51
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

Another problem never answered: Do we have the resources (funds and material) to create the amount of material needed? Lets say the cable is 1m2 thick: 1m2 * 100000m (Kármán line) = 100000m3. Maybe this doesn't sound like a lot until you check the prices of nanotube-like materials.

It will likely be much thinner than that. But that is a problem. Most plans assume "once manufacture becomes possible and cheap enough". Of course, ordering that much (once a process is proven) will quickly drive down the price. Talk about scale!

Re: Space Elevators Are Possible

#59

Post by frozenport »

thrownaway2424 wrote: post #11
elktea wrote: post #3

The animated icon on this site is terrible

The writing isn't too hot, either.

This HN needs a downvote button or an embargo on upvotes. For example, you can only upvote 5 minutes after you have read the link. Having been away for a year I am shocked by the number of upvotes everything is getting.

Re: Space Elevators Are Possible

#60

Post by Sharlin »

ohwp wrote: post #51
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

Another problem never answered: Do we have the resources (funds and material) to create the amount of material needed? Lets say the cable is 1m2 thick: 1m2 * 100000m (Kármán line) = 100000m3. Maybe this doesn't sound like a lot until you check the prices of nanotube-like materials.

Your length is off by three orders of magnitude. Fortunately, the surface area is off by four. In the most serious proposals, the space elevator "cable" is a flat tape with a cross-sectional area of a few square centimeters. Thus, we get:

2 cm^2 * 10^8 m = 20000 m^3. Yes, it's a lot of nanotubes, but the price of nanotubes per unit mass has dropped exponentially for a long while now, and the economies of scale involved in building a space elevator will lower the prices even more.

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