Japanese Begin Working On Space Elevator 696
thebryce writes "From cyborg housemaids and waterpowered cars to dog translators and rocket boots, Japanese boffins have racked up plenty of near-misses in the quest to turn science fiction into reality. Now the finest scientific minds of Japan are devoting themselves to cracking the greatest sci-fi vision of all: the space elevator. Man has so far conquered space by painfully and inefficiently blasting himself out of the atmosphere but the 21st century should bring a more leisurely ride to the final frontier. Japan is increasingly confident that its sprawling academic and industrial base can solve those issues, and has even put the astonishingly low price tag of a trillion yen (£5 billion) on building the elevator. Japan is renowned as a global leader in the precision engineering and high-quality material production without which the idea could never be possible."
Reminds me of a quote... (Score:5, Informative)
"The first space elevator will be built about fify years after everyone stops laughing."
-Arthur C. Clarke
Re:No I didn't Read TFA (Score:5, Informative)
Re:Just as a subnote... (Score:5, Informative)
And as a sub-subnote, this is approximately the cost of developing a complete conventional man-rated rocket launch system. I'm skeptical of the quoted price tag, but it would be extremely cheap if it could be achieved.
Re:Equal and opposite? (Score:5, Informative)
Re:No I didn't Read TFA (Score:4, Informative)
Technically, a weight in geosynchronous orbit would remain at the same altitude indefinitely with no other forces in effect. A space elevator will require a weight placed in an orbit which will supply tension — otherwise it'd be pulled out of orbit. It would probably be close to geosynchronous, but not quite.
(Actually, I'm not sure we even have a name for such an orbit. It would have to remain stationary above a point on the earth, but it would also have to hold up the cable and the car – in other words, without the tether it'd fly off into an entirely different orbit. Also, whenever the car accelerates it will put an additional tug on the cable – equal and opposite forces, you know. It'll be a tidy little equilibrium problem, and I'm glad I don't have to solve it!)
Re:call me when they have something (Score:5, Informative)
Well, no. Modern materials are within a factor of 3 or so of what's required for a space elevator, and known materials with sufficient theoretical strength exist, it just needs to be figured out how to build them. It would not be surprising to have those materials move from theory to reality within a decade or so.
AI, human-indistinguishable androids, and world peace, on the other hand, are not things that people have any idea how to achieve. And FTL drives are prohibited by currently accepted physical theory. To compare a space elevator to any of those is either deliberately being stupid, or a result of profound ignorance about either space elevators or all the other things you mentioned.
A space elevator is certainly not going to be as easy as a Popular Science article makes it sound. But on the other hand it's not anywhere near as difficult as the pipe dreams you named.
Re:Equal and opposite? (Score:5, Informative)
You're thinking of making a big tower (like a really large skyscraper). That wouldn't work. You have to approach the problem differently.
A simplified explanation of a space elevator is to take a really long, really strong cable (nanotubes), hang a weight on the end (more cable, an asteroid, lots of metal, etc), and anchor it on the equator. The weight goes out beyond geostationary orbit, and the tension of your cable pulls in on the counterweight to keep it from flying away. The tension keeps your cable taut. You can then run "cars" or "trains" up and down the cable on motorized wheels, most likely with electric power (solar, beamed microwave, or conducted through the cable). Your car can travel nice and slow, and be more efficient than a rocket.
If this doesn't make sense, imagine tying a weight to the end of a string, holding on to the other end, and spinning in circles. The weight will be held out at the end of the string and appear stationary relative to (since you're spinning too). Now put a caterpillar on that string that walks to the counterweight and back to you.
In short, the advantage is that you can use electrical power (which you don't have to carry with you) converted to direct mechanical energy to climb into orbit, instead of expelling fuel (less efficient) that you do have to carry with you. Your vehicle ("car") structure is simpler, more robust, and cheaper than a rocket. The elevator itself would be quite expensive, and requires some advances in materials science, but isn't physically impossible.
Re:Space Elevator Music (Score:5, Informative)
Being groped by space-whores could potentially be worth the wait anyway.
But remember, this is JAPAN we're talking about. They have tentacles.
Still, that amounts to $9.5 Billion USD at the moment. To put it in perspective, we're looking at spending $700B to bail out the banks this week. Over the course of the life of the shuttle, each launch as ended up costing $1.3B. So, for a little over a tenth of the bank buyout, or less than 10 shuttle launches*. Or, if you want to go with incremental costs ($60M), it'd be 158 launches - compared to the 115 launches as of Aug 2006. Still, I hardly think that it'd be fair to compare incremental costs of a dangerous platform with creating a new one with substantially lower incremental costs and hopefully greater safety.
Of course, the article does at least mention a number of issues - we need to industrialize a carbon nanotube production process that makes a cable that'd 4 times as strong as the best lab result to date. There's all sorts of issues with a pod that has to go 22k miles, straight up.
I heard a snippet of a speech by Reagan today about SDI and how we now finally have the missile defense stuff he proposed. They talked about him not realizing the difficulties and state of the art, at which I laughed a bit when, in the speech, he talked about it possibly taking 'into the next century'. Anyways - this topic reminded me of the SDI program - nice goal, but might end up being slightly out of our reach at the moment. Especially for a 'mere' 9.5B. Probably end up being 100B*, and an additional 40 years.
*Still cheap at the price.
Re:No I didn't Read TFA (Score:1, Informative)
That would apply twice the force to the orbiting counterweight as it would have to resist the gravitational pull of both the elevator and the elevator counterweight.
Re:No I didn't Read TFA (Score:5, Informative)
actually it's the center of mass that is relevant. The device would be considered in GSO because the center of mass would be there, or minimally lower (a few feet).
There would be roughly evenly distributed mass from earth to GSO, Maybe slightly increasing as it goes up to GSO, and then a large weight beyond GSO.
The idea is to not have it pull up on the ground, or press down (much). Last thing they need is to have a huge chunk of the terminal flung into space.
Boffin (Score:5, Informative)
Re:Start from orbit. (Score:3, Informative)
For a start, as you extend the cable from GEO, the center of mass of the satellite+cable moves downwards, changing its orbit. This alone will cause the bottom end (free-floating) to begin swinging, relative to Earth. Eventually, the swings will by gynormous. Then you'll touch atmosphere and the speed of the lower end will be immense, burning it up due to friction. Then it gets bad.
On the other hand, if you extend some mass upwards at the same rate that you extend mass downwards (making sure that moment arms match reasonably closely), then you can do it this way. Note that you have to have a mass ABOVE GEO at least as high as the mass below GEO. Which mass below GEO is the 22,000 Km long cable, which presumably is built stoutly enough to support more than one elevator car, which themselves won't be small (you're not going 22,000 Km in an elevator in less than days).
In other words, till we move a small asteroid into high Earth orbit, there's not much point in worrying about a Space Elevator becoming real.
However. That said, it still makes sense to work on the materials technology. It'd be basically dumb to spend a trillion or so dollars moving an asteroid to Earth orbit, only to find out that it'll be another 200 years till we have a material to connect said rock to the ground.
Re:call me when they have something (Score:3, Informative)
Although, having said that, that is measured by Earthbound clocks. What the shipboard transit time would be is another question.
Re:No I didn't Read TFA (Score:3, Informative)
Sir Arthur C. Clarke, when asked about when the space elevator would be constructed, he said something like:
Probably about 50 years after everybody quits laughing.
link [nasa.gov].
Don't shut the idea, the idea is pretty good, yet the implementation is going to be tricky, with a space elevator, sending a kg. into space will be way more cheap than what is cost nonadays.
Re:Start from orbit. (Score:2, Informative)
Re:Start from orbit. (Score:1, Informative)
choose any type of rope/cable/string/whatever. what is the maximum weight it can hold? how much does 36000km of that rope weigh? (this is fairly approximate, due to weakening of the gravitational field etc, but shows the basic problem)
Currently there is no material strong enough to hold 36000 km of its self.
Re:Start from orbit. (Score:4, Informative)
This is exactly how all the people considering this intend to do it. The problem is that the strength of cable required to support its own weight for that distance is huge. It has been determined that a ribbon shaped like a giant flat golf tee (can't think of a better description) will be best.
In short, your plan is the same as the best plan that mankind has so far, but we still don't have a suitable material to make the cable from.
Justin.
(Incidentally, geostat tends to be much higher than 100 clicks (qv 'Low Earth Orbit').)
Re:No I didn't Read TFA (Score:4, Informative)
The best counterweight is... another elevator car. If you have multiple tethers and superconducting cable (or another means of transmission), you can use a large fraction of the potential energy of the descending car to power the ascending car.
If you bring net mass down from orbit, you can actually make an energy profit (just on the elevator, I'm not saying that it would offset the costs of hauling propellant, etc, for asteroid miners and such).
Re:Space Elevator Music (Score:3, Informative)
Re:call me when they have something (Score:4, Informative)
No, it's your references which are wrong: if you could get to C your trip (from your view) would be instantaneous, from Earth it would take 4.3years.
Re:call me when they have something (Score:3, Informative)
Of course putting carbon nanotubes under a tensile load of roughly 5% of their maximum rated tensile strength have the unfortunate property of undergoing plastic deformation and lengthening, which is a sort of permanent thing.
Re:No I didn't Read TFA (Score:3, Informative)
Re:Who pays for the security? (Score:3, Informative)
Re:a disaster waiting to happen (Score:5, Informative)
So don't tie it down. There's nothing about the design of the space elevator that requires it to be tied to the earth in any way. If there's a storm coming, pull it up (or fold it up) about a mile or so above the clouds.
Re:No I didn't Read TFA (Score:3, Informative)
Re:a disaster waiting to happen (Score:3, Informative)
There's nothing about the design of the space elevator that requires it to be tied to the earth in any way.
Well, I think we would not want the counter-weight to go flinging off into space.
Re:a disaster waiting to happen (Score:3, Informative)
Actually, most of the designs that I've heard of do require the cable to be connected at the base. This is because the counterweight at the top isn't actually in orbit but is held taunt by the centrifugal force.
The counterweight is significantly higher than geosynchronous orbit, otherwise every time you brought mass up the cable the counterweight's orbital velocity would decrease slightly. Eventually, if you were bringing more mass up than down, you'd pull the counterweight lower, increasing it's speed. Once it is faster than geosynchronous orbit it's only a matter of time before it re-enters since the cable will be pulling it downwards.
With the counterweight above geosynchronous orbit, the tether pulls the counterweight forward as the earth spins. As you bring payload up, the counterweight increases speed slightly, but it will still be well above orbital velocity, which means that the tether would remain taunt and force the counterweight back to it (relatively) original position.
Re:No I didn't Read TFA (Score:3, Informative)
You obviously have no idea of the margins on the weight problems in this project. How much would a cable (capable of transmitting enough voltage) weight? The whole 35 000 kilometers of it? At such length even steel can not support its own weight, the weight of any type of additional conducting material on the ribbon will likely double or even tripple its weight and that in turn doubles or tripples the ammount of force the ribbon must be able to carry (per unit of weight). Currently we are struggling to get from current 10 GPa to the required 100 GPa and you propose to go up to 300 GPa just to get a cable up?
Laser power transmission to send energy from a ground-based nuclear power plant to the climber is a well tested solution that will not increase the weight of the system. Read up on the state of art before throwing absurd suggestions, please.
orbits (Score:4, Informative)
At a distance of (iirc) about 2/3rds of the way to geosynchronous orbit, an object dropped off the elevator will be in an elliptical orbit that just barely misses the atmosphere. Anything lower than that will re-enter. With rockets, of course, you could drop things lower and/or achieve round orbits.
Launching from beyond geosynchronous orbit ultimately robs the earth of its rotational energy (something that happens all the time anyways because of tides), so that's not really a big deal for the elevator as long as it can handle the additional tension. It would be a great way to launch things towards the rest of the solar system without wasting fuel.
Re:No I didn't Read TFA (Score:3, Informative)
And why would you want to go all the way to GEO anyway?
To go to work at centerpoint station? The station that builds/deploys the ribbon/s? Anyways, the problem with releasing early to get into LEO is that your orbital period attached to the cable isn't fast enough for LEO, thus you're going to end up in a rather elliptical orbit. Not insurmountable, but a pain.
If we actually get this built, I see the ISS being relegated to the same status as Mir.
If they're trying to travel to the Moon, I imagine they'd want to stop off at some space station first (which again, might not be in GEO)
Actually, it might be even further along. You're probably going to want a ribbon going out the other way to make the center of mass the GEO. You can use the other length to set up a slingshot.
Re:No I didn't Read TFA (Score:4, Informative)
Wikipedia has an indirect link to a 2002 paper where a microscopic nanotube was found to have a tensile strength of 0.15 TPa, which is easily strong enough. Even if that was wrong, I see no reason to expect the theoretical calculations to be so far off as to make a perfect structure lack enough strength. Whether they would last long enough to be useful in a space environment, with all the high energy radiation there, is something I wonder about. Can they be repaired in place as fast as they decay, or how much of a cable's life would be spent hauling up its replacement?
It does seem much too early for the Japanese (or LiftPort) to be getting serious about building a space elevator. I suspect that is more for the buzz, and the genuine hope is that the research dollars they generate will pay off in more mundane uses of super strength materials.
Re:a disaster waiting to happen (Score:2, Informative)
err, apart from the problem of flying away into space right? The whole idea of it is that it's "top heavy"