Japan to build Space Elevator

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Japan could never actually build this thing in Japan, because they can only be built over the equator. You can't have a geostationary orbit over Japan, sadly.
Opps, I wasn't thinking in that direction, but taking that into consideration, the existing satellites that are or were in geostationary orbit have to also be considered. As of 1 January 2005, there were 1,124 objects with a cross-section of more than 1 m catalogued in the geostationary region and its immediate vicinity. Of these, only 346 are operational satellites. Two thirds of them are equipped to jet out of their current orbit upon their end of life tour but a full one third of them will remain to end with natural conclusions. That conclusion could be by contact with other objects. Hope it's not an elevator.
"Look Ralph, doesn't that look like something coming awful fast towards us?"

Hey, I'm full of pizza and I'm going to call it a night.

Thanks for the discussion this evening.
 
Wouldn't it be easier/better to build it on the moon first? Much shorter cable, much less tension required, existing nano-tube technology would suffice? And, no icing/wind/crazy-religionists to worry about.
 
Wouldn't it be easier/better to build it on the moon first? Much shorter cable, much less tension required, existing nano-tube technology would suffice? And, no icing/wind/crazy-religionists to worry about.


Rrr, no. What Japan is trying to do is to build the space elevator until the
geostationary orbit, i.e. 36,000 km up. The cable needed is twice than that
(72,000 km) so that the length will be centered in the geostationary point for
the reason which has been explained by Nasor (post #32). On the other hand, the
distance from earth to the moon (center to center) is 384,403 km.
 
Rrr, no. What Japan is trying to do is to build the space elevator until the
geostationary orbit, i.e. 36,000 km up. The cable needed is twice than that
(72,000 km) so that the length will be centered in the geostationary point for
the reason which has been explained by Nasor (post #32). On the other hand, the
distance from earth to the moon (center to center) is 384,403 km.

I think he meant build an elevator to go from the moon's surface to lunar orbit. It would be a lot easier, but also a lot less useful.
 
I think he meant build an elevator to go from the moon's surface to lunar orbit. It would be a lot easier, but also a lot less useful.

Oops, you are right, he said on the moon, I thought to the moon. :eek:
Even though so, how is that easier? For instance, you are going to have to transport
all the materials to the moon first. Also the machines, the manpower, etc.
 
distance from earth to the moon (center to center) is 384,403 km.
Average it"s worse in reality with the moon ellips orbit and the fact that it doesn't rotate the earth around it's centre.

And not to hijack a threat
but here is a nice link abouth a martian space elevator
That amongs many things say that Mars would need only 42 GPA stong nanotubes far a cable weighting 2 000 000kg. Meaning it would weight the construction facility send to Phobos to construct it.
 
Average it"s worse in reality with the moon ellips orbit and the fact that it doesn't rotate the earth around it's centre.

And not to hijack a threat
but here is a nice link abouth a martian space elevator
That amongs many things say that Mars would need only 42 GPA stong nanotubes far a cable weighting 2 000 000kg. Meaning it would weight the construction facility send to Phobos to construct it.

Draqon would be really excited to read that one :eek: It looks really interesting as the cable length would be 'only' 6000 km.

From that source:
A novel approach is examined for creating an industrial civilization beyond the Earth. The approach would take
advantage of the unique configuration of Mars and its moon Phobos to make a transportation system capable of
lifting frequent payloads from the surface of Mars to space and accomplishing this at a low cost. Mars would be
used as the primary location for support personnel and infrastructure. Phobos would be used as a source of raw
materials for space-based activity, and as an anchor for tethered carbon-nanotube-based space-elevators to help raise
people and payloads from Mars to space. One space-elevator would terminate at the upper edge of Mars’ atmosphere
(6,000 km long). This terminus would only be moving about 0.52 km/s relative to the surface. Small craft could be
launched from Mars’ surface at a modest velocity and small rockets used to rendezvous with and attach the craft to
the moving elevator tip. Staged cable lifts could then raise modules from the craft to Phobos, then the empty craft
detached and landed with a paraglider. Landing on Mars from space could be done directly with a combination of
aerobreaking and use of a large paraglider to land.

Another space-elevator would be extended outward of Phobos an additional 6,000 km to launch craft toward the
Earth/Moon system or the asteroid belt. Release at the outward elevator tip velocity of 3.52 km/sec would result in a
hyperbolic velocity of about 2.6 km/sec. This is the Hohmann elliptical transfer velocity needed to reach the
Earth/Moon system, and is also nearly the transfer velocity needed to reach the inner edge of the asteroid belt. This
velocity boost would considerably reduce onboard propellant needs for space transportation. This outward elevator
tip could also be used to catch arriving craft, with staged elevators also bringing the vehicles or carrier modules from
the vehicles to Phobos.

These space-elevators would allow low cost movement of people and supplies from Mars to Phobos and from
Phobos to interplanetary space. This approach would allow Mars to be used to support an extensive space industry.
In addition, large quantities of material obtained from Phobos could be used to construct space habitats and also
supply propellant and material for space industry in the Earth/Moon system as well as on and around Mars.
 
Yes, the cables could just terminate in space. The only important thing is for the center of mass to be at the point of geostationary orbit. If you use 70k km of cable instead of 35k (half below GEO and half above) then the center of mass would still be at GEO and the system would still be stable. The advantage of this is that the end of the cable would be traveling at far above orbital velocity, so you could launch things directly out into the solar system without having to burn rocket fuel to move from a geostationary orbit to an earth-escape orbit. The disadvantage is that you have to make twice as much cable.


Well, it depends on whether by "fantasy technology" you mean "technology that we have a good idea how to build and is probably a few years or decades away" or if you want it to mean "technology that we have absolutely no clue how to build and probably won't develop for the foreseeable future."

The minimum strength for a space elevator cable is around 65 GPa, but most designs call for a cable material with a strength of around 120-130 GPa so that there's a comfortable safety factor. We have already developed carbon nanotubes with measured tensile strengths of 63 GPa, and calculations indicate that "ideal" nanotube ropes should have tensile strengths around 300 GPa. So we know of a material that's strong enough, and we are getting progressively better and better at making it. Of course it's not clear exactly when 100+ GPa nanotube cables that are appropriate for a space elevator will be developed, but it's definitely a technology that everyone expects within a decade or two - we aren't talking about wacky fantasy technology that we have no idea how to build.

A cable that would let you pull the entire assembly down from orbit without breaking would have to be a LOT stronger than a cable that merely hung under its own weight.


The cable will have a density of about 1.3 g/cm^3, and is less than 1 cm thick along most of its length, so no one is ever likely to be hit with 100 kg of it. A better analogy would be having two airplanes flying over Tokyo with a long, thin piece of nylon rope strung out between them. Then they cut the rope loose. The rope isn't going to crush anyone or damage any buildings when it lands, it's just going to drape itself over the city and annoy people.

On a side note, Tokyo would never be hit with the cable anyway because the cable has to be anchored along the equator. Sorry, no space elevator for Japan.

You are forgetting that entire cable is already rotating exactly in sync with the surface of the earth when it is cut. Yes, of course eventually coriolis forces will cause it to "wrap around" the earth, but the cut would have to be extremely high (thousands of km up) before they had any significant effect. Of course the cable isn't going to coil itself into a nice little pile right at the base of the elevator, it's going to be subject to wind etc. as it floats down to earth. The point is that there isn't going to be any significant "wrapping" of the cable around the earth unless the cut is made very high.

Edit: And if you're still really worried about it, you can anchor the cable on a ship over the ocean or something.

As for problems that don't break the cable, one of the nice things about the space elevator is that it is self-stabilizing because of the earth's rotation and the centripetal force being exerted on the portion of the elevator system that's beyond geostationary orbit. If you simply pull on the cable for a while it will deform the cable slightly and pull the whole thing down a little, but as soon as you release the pressure it will begin to drift back to its original position. This is pretty important, because otherwise the whole thing would eventually become destabilized by the changes in angular momentum that occur when cars move up or down it.

NGM, you seem very hostile to the idea of a space elevator. It's perfectly fine that you're skeptical, and there are indeed many major engineering challenges associated with building one. But you might want to remember that a lot of serious physicists and engineers have evaluated the idea and they generally agree that it will be feasible relatively soon. It's not like this is some wild idea that a crackpot came up with on this message board; space elevators have been seriously studied since the 1970s. You've only been hearing about them in the popular press recently because it has only been in the last 10 years or so that we've gotten close to having the technology to actually make a cable that is strong enough. Of course that doesn't mean that we will necessarily ever be able to build one, but most of the things that immediately come to mind as potential problems have already been very thoroughly evaluated by professionals.


Btw, in the above post you mentioned the necessity of the center of the
cable to be in the geostationary orbit. This is to make sure the stability
of the cable, right? So that it would look like a satellite, i.e. hanging on
the geostationary orbit, maintained by centripetal force. The total weight
of the cable would be around 100 kg, whereas the mass of the elevator and its
load (human, supplies) will outweigh it. So, when the elevator is attached into
it, isn't it going to make the center of the mass changing?
 
Oops, you are right, he said on the moon, I thought to the moon. :eek:
Even though so, how is that easier? For instance, you are going to have to transport
all the materials to the moon first. Also the machines, the manpower, etc.

Easier in terms of technology. Since the moon's gravity is lower the cable doesn't have to be nearly as strong, so you could build one today using a variety of commercially available materials like spectra or zylon (or probably a bunch of others that I don't know of off the top of my head).

In addition to making it a lot easier to maintain a moon base, there are several kinds of rocket fuel that can be made from lunar materials, and such an elevator would allow you to bring up an unlimited amount of fuel from the moon for use elsewhere, more or less for free. Or aluminum, which you can also get from the moon. You could imagine it being very helpful if you ever wanted to do any sort of large-scale manufacturing in space.

The actual cost of building it wouldn't be as high as you might think, because you could launch the cable in one piece from earth in a moderately big rocket. The main costs would be associated with setting things up on the moon, but it's assumed that you're already planning to have a colony or some industry or something there, otherwise there's no point in building it in the first place.
 
give me a example the moon has virtually no hydrogen
There might or might not be water on the moon - the jury is still out. A slurry of aluminum nanoparticles suspended in a liquid oxygen also makes a reasonably good rocket fuel, and there is plenty of both on the moon. If you're using nuclear thermal engines, liquid oxygen can be used as a propellant by itself.
 
A moon base would ideally have nuclear reactor technology for energy production. No one complaining about messing up the environment [which is minimal anyway - radioactive materials decay away - chemical pollutants tend to be stable and remain indefinitely]. The energy could be used to extract aluminum and other useful materials, propel 'moon-buggies', and power a space-elevator for transporting aluminum, etc. to high orbit for subsequent production of a mars shuttle. If we're going back to the moon, we ought to do it right.
 
Easier in terms of technology. Since the moon's gravity is lower the cable doesn't have to be nearly as strong, so you could build one today using a variety of commercially available materials like spectra or zylon (or probably a bunch of others that I don't know of off the top of my head).

In addition to making it a lot easier to maintain a moon base, there are several kinds of rocket fuel that can be made from lunar materials, and such an elevator would allow you to bring up an unlimited amount of fuel from the moon for use elsewhere, more or less for free. Or aluminum, which you can also get from the moon. You could imagine it being very helpful if you ever wanted to do any sort of large-scale manufacturing in space.

The actual cost of building it wouldn't be as high as you might think, because you could launch the cable in one piece from earth in a moderately big rocket. The main costs would be associated with setting things up on the moon, but it's assumed that you're already planning to have a colony or some industry or something there, otherwise there's no point in building it in the first place.

Ok, thanks for the reply. What about my question in post #48? Am I right in
thinking that the elevator load will influence the center of the overall mass, so
the center won't be in the geostationary orbit anymore, but somewhat lower?
 
But the concept has been stuck on the ground floor for decades, not least because constructing a tether strong enough for the job is beyond current technology. Nanotubes might be up to the task, but they would have to be made longer and with fewer defects than any that can be fabricated today.
A new study makes the prospects appear even gloomier.

Even if a space elevator could be built, it will need thrusters attached to it to prevent potentially dangerous amounts of wobbling, says Lubos Perek of the Czech Academy of Sciences' Astronomical Institute in Prague. The addition would increase the difficulty and cost of building and maintaining the elevator.


Previous studies have noted that gravitational tugs from the Moon and Sun, as well as pressure from gusts of solar wind, would shake the tether. That could potentially make it veer into space traffic, including satellites and bits of space debris. A collision could cut the tether and wreck the space elevator.

http://space.newscientist.com/article/dn13552-space-elevators-face-wobble-problem.html
 
Ok, thanks for the reply. What about my question in post #48? Am I right in
thinking that the elevator load will influence the center of the overall mass, so
the center won't be in the geostationary orbit anymore, but somewhat lower?
Sorry, I somehow missed that before. Even though the cable is very thin and relatively low density, there is a LOT of it, plus the mass of the counter-weight (or extra length of cable). The mass of the elevator car+payload is probably going to be very, very small compared to the over all mass of the system, so the overall change in the center of mass will be very small - probably on the order of just a few tens of meters. But if you're really worried about it, you can always just have another mass located near GEO that you move up the cable right before you attach the car, so that the center of mass stays in the right place.
 
A new study makes the prospects appear even gloomier.

Even if a space elevator could be built, it will need thrusters attached to it to prevent potentially dangerous amounts of wobbling, says Lubos Perek of the Czech Academy of Sciences' Astronomical Institute in Prague. The addition would increase the difficulty and cost of building and maintaining the elevator.

Previous studies have noted that gravitational tugs from the Moon and Sun, as well as pressure from gusts of solar wind, would shake the tether. That could potentially make it veer into space traffic, including satellites and bits of space debris. A collision could cut the tether and wreck the space elevator.

http://space.newscientist.com/article/dn13552-space-elevators-face-wobble-problem.html

This has already been addressed. There are ways to cancel oscillations in the tether, including moving the base slightly or carefully timing the ascent and decent of the elevator cars. So far as I know, no one has ever shown quantitatively that the elevator cable could not be stable.
 
It would make more sense to be build only half an elevator. Basically you dangle the overall shaft from a space platform over the earth and use Airships to lift containers to the shafts base platform which is suspended at a point high in the atmosphere but not too high that an Airship can't reach.

If the "shaft" is a cable, then it can be retracted and moved and then redeployed at a new location. I'd suggest having something like a Solar Drone (Similar to the drones the military uses) at the base of the shaft to control the end which can be dis-attached during redeployment.

Using this method would mean that with thrusters it would be possible to move the shaft/Platform around the globe, so any country could potentially use it for a duration.

Using a "container" system would work quite well, especially if the actual "lift/elevator" mechanism was individual per container (Namely inbuilt), so there is no lift/elevator to fail due to an over extended lifespan, as each container could contain their own lift/elevator mechanism.
 
The cable would not be able to feed on earth angular momentum and would slow down in our atmosphere until it crashes.

A better method would be to find a reasenable massed NEO (at least 10E16kg)and bring it in orbit at 10 000 km (that around 3 times the altide of the ISS and abouth 1/7 the lenght of a traditional space elevator.
This rock comparable to phobos would apart from the estetical (it would apear to be half the size of the moon) have little to no tidel effect on the earth but the earth would have a mayor effect on this new moon tidal locking it.
if you would attach the cable to this new moon and hang the lower end in our upper atmosphere then the energy will be transfert to the new moon changing it's angular momentum, however earth gravitational lock would then speed it up to keep it tidal lock and the moon would loose minimal altitude altough it would probably crash with the earth in between 1000- 10 000 years but by that time we could have imported enough fuel trusters and power plants to launch it to alpha centauri. So it would never crash.
 
As someone said above, I don't think space elevators will ever be possible. They are just too futuristic... Sci-fi in my humble opinion.
 
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