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Future of Space Elevator Looks Shaky
Posted by
kdawson
on Tue Dec 09, 2008 02:43 PM
from the a.-c.-clarke-quaking-in-his-grave dept.
from the a.-c.-clarke-quaking-in-his-grave dept.
lurking_giant writes "In a report on NewScientist.com, researchers working on development of a space elevator (an idea we have discussed numerous times) have determined that the concept is not stable. Coriolis force on the moving climbers would cause side loading that would make stability extremely difficult, while solar wind would cause shifting loads on the geostationary midpoint. All of this would likely make it necessary to add thrusters, which would consume fuel and negate the benefits of the concept. Alternatively, careful choreography of multiple loads might ease the instability, again with unknown but negative economic impacts."
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Hardware: Space Elevator Teams Compete for NASA Prizes 158 comments
Hugh Pickens writes "The University of Saskatchewan's has the first place climb in the Second Annual Space Elevator Games being held this weekend at the Davis County Event Center in Salt Lake City. Teams are competing for $1,000,000 in NASA prize money. Although the idea of a space elevator has been around for decades, the space technologies needed to support it have yet to be created. The non-profit Spaceward Foundation has hosted an annual competition since 2005 to build a super-strong tether, or get a robot to climb a suspended ribbon. In the robot climber competition, teams have to get their device to hurtle up a 100-metre-long ribbon, suspended from a crane, at an average speed of two metres per second. The climber must be powered from the ground: strategies include reflecting sunlight from huge mirrors on the ground to solar panels on the climber; shining lasers from the ground up to similar panels on the robot; or firing microwaves up at the climber. Qualifying rounds have been taking place all week, and although high winds and rain have caused delays, four out of eight teams have made it into the finals. There are no outdoor climbs today because of bad weather but some of the tether competitions will happen indoors later this afternoon."
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Technology: Japanese Begin Working On Space Elevator 696 comments
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."
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Told you so (Score:5, Funny)
I told everyone it wouldn't work. But would they laugh at me? No!
Re:Told you so (Score:5, Interesting)
Most of the inner planets have no space elevator at all; Venus and Mercury because their days are unfeasibly long, Earth because its gravity well and debris belts challenge the limits of engineering.
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Re:Told you so (Score:5, Insightful)
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Alterantives (Score:5, Funny)
If an elevator won't work what about a space escalator?
Re:Alterantives (Score:5, Funny)
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Re:Alterantives (Score:5, Funny)
/me runs off to patent the "Space Canoe".
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Serious Alterantives (Score:5, Informative)
In all seriousness, the space elevator gets a lot of press because it's the concept that is easiest for the average person to understand, that doesn't mean it is the only option (or even the best option) to efficiently get stuff into orbit without rockets. I always thought the launch loop made more sense (http://en.wikipedia.org/wiki/Launch_loop/ [wikipedia.org]).
The idea is that the moving parts are what keeps the structure stable, rather than tension or compression. In theory it could be built with today's materials and technologies and could be cabable of launching more into orbit in its first month than has been launched to date with conventional rocket launches.
Then of course, there are the non-traditional rockets such as laser propulsion, where a laser is shined up from the ground to superheat the air in the rockets cone, which, in turn, produces thrust. And of course, my personal favorite, there's always Project Orion. Not the wimpy one NASA is using to get to the moon, I'm talking about the original Project Orion. As in, using thermonuclear bombs to launch a city sized spaceship into orbit.
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The best part is.. (Score:5, Funny)
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Re:Alterantives (Score:5, Funny)
But when you get there the shops are all closed. Bollocks to that.
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Scary stuff (Score:5, Interesting)
You think the engineering is mind boggling? (Score:5, Funny)
Your mind will be hyperboggled by the amount of paperwork, business trips and expense account lunches the project will generate. The engineering will look like chump change.
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Re:Scary stuff (Score:5, Funny)
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Re:Scary stuff (Score:5, Insightful)
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Re:Scary stuff (Score:5, Funny)
Take a ball of paper and throw it at 100,000 miles an hour. Tell me that's not going to cause some damage.
For starters it's really going to strain your arm.
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Re:Scary stuff (Score:5, Informative)
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Re:You forgot Apollo 1 (Score:5, Funny)
Apollo 1 doesn't count, as NASA declared a mulligan.
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Just jump. (Score:5, Funny)
there goes another dumb jet pack idea (Score:5, Interesting)
Having read the article... (Score:5, Informative)
Their big objection seems to be not that the forces on the elevator are unmanageable but that oscillation could lead to payloads being released into orbits that are "10 km" too high or too low, or that the oscillation could put the elevator in the path of a satellite. Correcting that would require thrusters.
For the first, surely you could simply time your release with the oscillation, to get into the orbit you want. Even if you couldn't, the space elevator would be good for putting things in geosynchronous or interplanetary transfer orbits. The cost of a bit of propellant to correct a +- 10 km error is pretty minor compared to getting into one of those orbits in the first place.
For the second, thrusters to purposely oscillate the cable to allow it to dodge out of harms way are a pretty standard part of any space elevator proposal. That is, the ability to move the cable a little is a desired, even necessary part of its design.
The internet makes playing "telephone" boring (Score:5, Informative)
The "Space Elevators are unstable! The concept is doomed!" Slashdot summary would have been much more thrilling if there wasn't a link to the "Space Elevators are tricky! There might still need to be tiny final orbital adjustments!" New Scientist article, and even that would have been more exciting than the "Space Elevator dynamics is modeled by these stable but undamped equations! Sending multiple payloads up in the right phase causes the minor Coriolis-induced wobbles to cancel out!" Acta Astronautica article.
You people with your damn hyperlinks are ruining journalism. It's getting so a guy can't even wait breathlessly for the News At 11 anymore to find out what common household product might be Killing Our Children.
Re:I call bullshit! (Score:5, Funny)
Obligatory xkcd reference: http://xkcd.org/123/ [xkcd.org]
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Re:I call bullshit! (Score:5, Informative)
You are right, but you are wrong. The Coriolis effect is very real, but it is not force in the strict sense.
The gist of the point in the article is that as a payload is moved up the elevator, it must be accelerated to the side, since the upper portions of the elevator are moving circumferentially faster than the lower portions. The force required to accelerate the payload must come from the elevator itself, causing small displacement of the elevator. The use of the term "Coriolis effect" is not strictly wrong, though it is somewhat sloppy.
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Re:Fixed thrusters rockets (Score:5, Informative)
Ion drives need physical fuel as well as power... they just are a lot more efficient than traditional chemical-reaction drives. This is because they accelereate the fuel to near-lightspeed, maximizing the reactionary force per kg of fuel. (force is a combination of the mass expelled and the speed of which it is expelled... the faster the exhaust, the higher energy per kg of exhaust).
So, you'd still have to haul up fuel, just not as much as with chemical rockets.
MadCow.
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Re:Don't forget the ninjas (Score:5, Funny)
Wait till it 30.. it'll stabilize around then.
Unless she's still single. Then she'll start collecting cats.
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Re:No energy saved (Score:5, Informative)
So much wrong, so little time...
Sorry, most of your post is factually challenged.
1) Space elevators do not lower the energy required - they just use the energy differently.
2) They do not take you to where the gravity is weak - they take you to the point where the force of gravity (which is essentially unchanged) is balanced by centripetal force (which, being linked to w^2r goes up linearly with distance).
3) Rockets typically take you to about 7.7 km/s (orbit), not 11.2km/s (escape).
4) The energy given to the satellite (assuming the same final orbit) is identical regardless of the launch vehicle/elevator used. What is different is the energy efficiency of the system in putting energy into the satellite:
A rocket sends lightweight propellant in the opposite direction very fast in order to transfer the energy. An elevator sends a huge mass (essentially the entire earth) very slowly in the opposite direction. Since momentum is conserved, the mass x velocity of both systems is the same - but since the Earth masses a lot more than most rockets, the Earth's relative velocity is far lower. This is where the e=0.5*m*v^2 comes in - the "wasted" energy is the energy provided to the Earth or propellant. Earth has a small v, big m - which works better than the rockets big v little m.
So you always have to give the satellite the same energy - there are just different efficiencies of giving it that energy. Space cannons have the problem of needing to give that energy extremely quickly... very difficult indeed.
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