Obayashi Corporation to Build Space Elevator by 2050

[I'm Murrin]

Well this is interesting.

realitypod.com/2013/02/japanese-company-to-build-an-elevator-from-earth-to-space/

A Japanese company is now prepping to build the elevator to space and will be completed by 2050. Japan’s Obayashi Corporation thinks that NASA is not moving fast enough so they plan to take the responsibility of do the next big thing in space research. However, the feasibility of the plan and the current technological capabilities of the company are still not disclosed.

According to that article the elevator will travel at a maximum speed of 125mph and will take 8 days to reach its destination.

[Savor Dam]

At first, this sounded all wrong. Eight days at 125 mph sounded entirely wrong. Looking at the article, however, the station will be at 22,000 miles altitude (far higher than I expected) with a counterweighting station at almost three times that height.

Duh. a space elevator station pretty much needs to be at geosynchronous height. Shame on me...I should know that instinctively.

At 22k miles altitude, an eight day trip is about 114 mph. Thirty people in that proximity for eight days will be interesting...

[I'm Murrin]

Hmm, good point. Where are they planning to build it? A geostationary orbit has to be directly above the equator.

[Savor Dam]

Wonder if the return trip from the geosynch point is also eight days? While people and cargo could conceivably make a much faster return via conventional reentry, surely the elevator cab must return via the "beanstalk", nu?

[Avatar]

First conceived in science fiction in 1960, by a Russian author IIRC.

Ah, science fiction...where would we be without you.

--A

[I'm Murrin]

Interesting thought, Savor. Space elevators are intended to take less energy than the extreme amounts for a rocket to break out of the gravity well, but re-entry probably is quicker and easier by the old method. But how do you get the re-entry vessel up to the space station?

[ussusimiel]

I've always thought the space elevator idea was cool but very impractical. The first thought that occurs is the economic justification for spending $1billion on it. There will need to be clear economic reasons for it. (Maybe they are already present, but I don't see it yet.)

Secondly, the exposure of a 22,000km string to attack or adverse natural events seems ludicrously large. My guess is that before it's every seriously considered the technology for relatively cheap, safe atmosphere-to-space flight will be available at a fraction of the cost.

u.

[Hashi Lebwohl]

I cannot think of any material with a tensile strength sufficient to support itself with the distances required. If we presume that such a material has a density of 10 g/cm^3, a 10 cm diameter cable after only 2 km weighs...hang on...628 metric tons (1 m-ton = 1000 kg), requring a tensile strength of 2 metric tons per cm^2. It would shear itself and fall back to the ground. Even if you collect all the material in space and begin lowering it to the Earth, its weight would pull the anchor down with it or break off before getting all the way down.

No, although they are a nice idea I have always been of the opinion that space elevators are the fiction part of science fiction.

We will see "inertialess" thrust before we see a space elevator. DVICE had an article recently where China is claiming to have made some advancements on intertialess thrust, but so far no one in a position to verify the results has been given access to the prototype, the specs, the experimental data, or anything. In short--it is all talk.

[Vraith]

Heh...from the drawing, it is a terrible design even if the materials existed...I'm not sure they're even theoretically possible...and surely not by 2050.

Heh...just to make the counterweight, they'd have to start launching 2 tractor-trailer loads every day starting right now.

I suspect 1 trillion is probably about 1 tenth of what it would really cost.

Anti-gravity is a better option.

[I'm Murrin]

I cannot think of any material with a tensile strength sufficient to support itself with the distances required. If we presume that such a material has a density of 10 g/cm^3, a 10 cm diameter cable after only 2 km weighs...hang on...628 metric tons (1 m-ton = 1000 kg), requring a tensile strength of 2 metric tons per cm^2. It would shear itself and fall back to the ground. Even if you collect all the material in space and begin lowering it to the Earth, its weight would pull the anchor down with it or break off before getting all the way down.

No, although they are a nice idea I have always been of the opinion that space elevators are the fiction part of science fiction.

According to Wikipedia:

Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms. In 2000, a multi-walled carbon nanotube was tested to have a tensile strength of 63 gigapascals (GPa). (For illustration, this translates into the ability to endure tension of a weight equivalent to 6422 kg (14,158 lbs) on a cable with cross-section of 1 mm2.) Further studies, such as one conducted in 2008, revealed that individual CNT shells have strengths of up to ~100 GPa, which is in agreement with quantum/atomistic models. Since carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3, its specific strength of up to 48,000 kN·m·kg−1 is the best of known materials, compared to high-carbon steel's 154 kN·m·kg−1.

A lot better than yuor numbers, but a little poking around shows still not strong enough for 22,000 miles.


On the 22,000 mile bit: It looks like that's roughly the point you need to be at on a space elevator to experience (apparent) zero-g. Higher than that and you begin to feel the centrifugal force of your rotation pulling away from earth. Which I guess means it's also the ideal point to be launching spacecraft from.

[Vraith]

I cannot think of any material with a tensile strength sufficient to support itself with the distances required. If we presume that such a material has a density of 10 g/cm^3, a 10 cm diameter cable after only 2 km weighs...hang on...628 metric tons (1 m-ton = 1000 kg), requring a tensile strength of 2 metric tons per cm^2. It would shear itself and fall back to the ground. Even if you collect all the material in space and begin lowering it to the Earth, its weight would pull the anchor down with it or break off before getting all the way down.

No, although they are a nice idea I have always been of the opinion that space elevators are the fiction part of science fiction.

According to Wikipedia:

Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms. In 2000, a multi-walled carbon nanotube was tested to have a tensile strength of 63 gigapascals (GPa). (For illustration, this translates into the ability to endure tension of a weight equivalent to 6422 kg (14,158 lbs) on a cable with cross-section of 1 mm2.) Further studies, such as one conducted in 2008, revealed that individual CNT shells have strengths of up to ~100 GPa, which is in agreement with quantum/atomistic models. Since carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3, its specific strength of up to 48,000 kN·m·kg−1 is the best of known materials, compared to high-carbon steel's 154 kN·m·kg−1.

I thought there was some composite that included boron or something that was even stronger...

But even that isn't strong enough as a guess, I don't feel like doing a whole bunch of math, especially since some of it will surely be beyond me.

There was something SF I read once where they webbed together at least all the inner solar system...they made the material by using a some quantum quirk or something that allowed them to extend the range of the strong nuclear force a bit to hold atoms together.

[I'm Murrin]

Yeah, apparently nanotubes are currently only good for about 2,000km, not 35,000.

[Hashi Lebwohl]

A lot better than yuor numbers, but a little poking around shows still not strong enough for 22,000 miles.

Absolutely--a lot better than my numbers, which were done in two minutes on a calculator while at work with no notes and only one or two quick presumptions. Those results are also for nanotubes from 13 years ago; today's nanotech will surpass that...but still not suffice for creating a space elevator.

[I'm Murrin]

And there's also the fact that we still can't grow tubes longer than tens of centimetres.

[Avatar]

It's certainly not practical right now. However, that's not to say that it won't become so. As whatsisname up there pointed out, there isn't much use for it right now either.

Give it a couple hundred years and that might change though.

Heinlein, another writer who wrote about space elevators, also posited mass-driver "catapults" to launch objects out of gravity wells.

Prototypes had already been built by the 70's, and are apparently quite feasible.

--A

[Vraith]

It's certainly not practical right now. However, that's not to say that it won't become so. As whatsisname up there pointed out, there isn't much use for it right now either.

Give it a couple hundred years and that might change though.

Heinlein, another writer who wrote about space elevators, also posited mass-driver "catapults" to launch objects out of gravity wells.

Prototypes had already been built by the 70's, and are apparently quite feasible.

--A

There are a fair number of SF variations of catapults/flingers and such that are actually far more technologically feasible with a 2050 goal...
I don't recall how Heinlein's [or any of them] actually worked...
But the "rail-gun" type that various authors have used is, IMHO, easily workable by that date.

[ussusimiel]

There's a space elevator in the backstory of David Brin's Sundiver. They call them beanstalks and there's one in Brazil, presumably because it's on the equator.

Railguns and mass drivers are viable technology. (They'd need to be a fairly long to achieve escape velocity.) For humans the obvious problem is the g-forces involved. Still a lot of that could probably be overcome if it were possible to fill the cavities in the body with fluid so that there wasn't the danger of unequal pressure. Then it becomes a matter of medical technology rather than physics. (Anyone want to put up some seed capital for research? )

u.

[Avatar]

Heinlein's was also a rail-gun type with induction fields. It was for materials, not passengers, so no problem there.

In Friday, his space elevators were also called "beanstalks" (although that was slang...IIRC, the official name was "Skyhooks") and there was one in Brazil, and one in Kenya.

--A

[sgt.null]

this was solved back in 1902

[SerScot]

Hashi,

I cannot think of any material with a tensile strength sufficient to support itself with the distances required. If we presume that such a material has a density of 10 g/cm^3, a 10 cm diameter cable after only 2 km weighs...hang on...628 metric tons (1 m-ton = 1000 kg), requring a tensile strength of 2 metric tons per cm^2. It would shear itself and fall back to the ground. Even if you collect all the material in space and begin lowering it to the Earth, its weight would pull the anchor down with it or break off before getting all the way down.

No, although they are a nice idea I have always been of the opinion that space elevators are the fiction part of science fiction.

We will see "inertialess" thrust before we see a space elevator. DVICE had an article recently where China is claiming to have made some advancements on intertialess thrust, but so far no one in a position to verify the results has been given access to the prototype, the specs, the experimental data, or anything. In short--it is all talk.

Carbon nano-tubes.