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Scientist Sees Space Elevator in 15 Years
bofh31337 writes "Scientist Bradley C. Edwards, head of the space elevator project at the Institute for Scientific Research, thinks an elevator that climbs 62,000 miles into space could be operating in 15 years. He pegs the cost at $10 billion, a pittance compared with other space endeavors. 'It's not new physics--nothing new has to be discovered, nothing new has to be invented from scratch,' he says. 'If there are delays in budget or delays in whatever, it could stretch, but 15 years is a realistic estimate for when we could have one up.' NASA already has given more than $500,000 to study the idea, and Congress has earmarked $2.5 million more."
At the minimum, keep this guy funded so he can research the necessary materials. The article gives a timeframe of 2 yrs for the nanotube technology. If something like this could actually be built in the coming generation, getting things into space will probably become a whole lot cheaper.
Plus, a space elevator.. it even SOUNDS cool. Almost as cool as moonbase.
One little problem for a human to ride the space elevator--the slow speed of assent means that people would pass though the Van Allen belt for a rather long time--exposing them to possibly deadly radiation.
The MIDPOINT of the cable will be in geosynch orbit. This is at 32K miles. The remainder of the cable is outside of this, to counterbalance the pull of gravity on the lower portion of the cable.
Nothing in the article mentions the feasability of getting a decently sized counterweight at the top of the elevator. All plans I've heard of require at least some sort of asteroid...and if you're talking politics, people are going to be afraid of dragging a rock into Earth orbit that could smash into the planet a.la if something went awry.
I did some more research on this and found the following:
e di a/s/sp/space_elevator.html
The concept of the space elevator first appeared in 1895 when a Russian scientist named Konstantin Tsiolkovsky was inspired by the Eiffel Tower in Paris to consider a tower that reached all the way into space. He imagined placing a "celestial castle" at the end of a spindle-shaped cable, with the "castle" orbiting Earth in a geosynchronous orbit (i.e. the castle would remain over the same spot on Earth's surface). The tower would be built from the ground up to an altitude of 35,800 kilometers (geostationary orbit). Comments from Nikola Tesla are suggestive that he may have also conceived such a tower. His notes were sent behind the Iron Curtain after his death.
http://www.campusprogram.com/reference/en/wikip
How is coriolis force going to be handled.
Since velocity=(radius)(angular speed) then there has to be a tangential acceleration as the elevator starts going up.
Obviously tension on the cable can be used if you do not go up too fast or send up too much mass at one time.
Of course the talk as always about using this to go up, but would it be possible to use this as a really big sling shot to launch space craft around the solar system.
The nanotube thread we can make now is not strong enough to work. What we need is a way to "weld" nanotubes together without introducing massive defects (that's key). There's a significant amount of physics to be done there.
On the other hand, we've been able to increase the size of the nanotubes we've been able to grow an order of magnitude every few years. We're up to centimeters now for one, single tube, and the process is likely scalable (as in, bigger furnace, longer tubes).
To get an idea of how hard this would be:
62000 miles is about 1*10^14 micrometers,
There are about 3.2*10^7 seconds in a year,
nanotubes grow at around 300 micrometers a second,
so it would take 10,000 years to grow that elevator out of continuous tubes (unless we're way, way off on the speed).
I'm not sure about 15 years, but I think we'll get it done sometime in the next 100 with some sort of welding technique, and in the long run, it's going to cost a lot more than anyone now thinks.
If the end of the elevator is only at geosychronous, then it has thousands of tons of weight pulling it downward. But since anything *past* geosync actually flings the object away from the planet, you put just as much weight on the other side of geosync, performing a nifty balance. As for why its not 45k miles, I can't say. Seem to remember it tapering at the end quite a bit, for some engineering reason.
Best of all, go out to the end of it, let go.... you get a free trip out of orbit. Be sure to bring plenty of food and water.
With all the force of fluttering newspaper. It would take hours to come down, and would be more of a pollution problem than a catastrophe. Of course, this assumes failure at the thickest portion of the cable, just around geosync somewhere. The thinnest part, most likely to fail I'd think, if it were to fail, would leave it hovering just above the ground waiting to be duct taped back in place.
If there is a catastrophe to be had here, I'd think, it would be it burning (do nanotubes burn very well?). What sort of electrical storms are there that far up? The electrical potential between sky and ground can be huge, and we're stretching a non-insulator across the two.
I'm not so sure about that 62,000 miles figure. That's more than the circumferance of the earth.
The "real" issue is where the Kinetic Energy comes from. Space Ship 1 proves that a small relatively inexpensive craft can attain the elevation needed to reach space. What Space ship 1 did not have is enough energy to reach orbital speeds. The additional energy is over 30 times more than required to reach the elevation.
Now a space elevator has the exact same problem. Somehow this energy has to be fed into the system.
Now - suppose we launch into space a tether and rotate this teather in the opposite direction to orbit so that the relative velocity of the tether when it picks up a spaceship is low. This tether will need to impart kinetic energy to the craft and perhaps this can be done through some sort of electrical propulsion system. If so, then free sunlight from space can be collected to provide the electricty.
So just maybe there are hybred systems that will work.
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One way a tether system could be used is to use a baloon to raise the ship to a high elevation and then drop a tether down. Of course baloons can be attached to the space elevator cable itself... but why bother? You can simply lift the elevator car.
Now - this is real science fiction. Suppose in orbit we build a monorail that encricles the entire earth... a ring at the equator if you will.
On this monorail you run a train in the opposite driection from the orbital direction and then drop the cable down to the car being lifted up by the baloon. Clearly you have the option of matching velocities. So the car gets transfered to the cable and the baloon gets deflated as the cable takes over the lift. In order to counter balence the weight of the train, the monorail track has counterwieghts and enough strength to actually carry the train and the elevator car.
Then as the car is lifted by the cable the velocity of the train on the monorail is increased to match orbital speeds.
I think all can see the problems with this system. The train must travel at a speed of about 25,000 miles per hour in order to match the speed of the elevator car and even in space it might be difficult to build a train that can handle this velocity difference relative to its track.
However - perhaps using maglev this can be done. If so the kinetic energy of the train can be transfered to the monorail and once the elevator car has been picked up the kinetic energy of the monorail can be recovered to accelerate the elevator car and the train. Essentually the train just brakes and we would need a big capacitor that we can feed the energy into.
Aside from the idea that the monorail is over 26,000 miles long, maybe the physics will work.
Also, with a properly designed rail gun we might be able to launch the building materials into space so there might be some way to build the monorail without expensive rocket systems.
Science fiction? of course this is. IMHO so is a space elevator.
One would think watching Earth grow smaller beneath you would be entertainment enough. Those who have seen it before can bring books. Or maybe read the instruction booklets on how to avoid explosive decompression...
Rule number one: "Don't open the window" means "Don't open the window!".
Rule number two: "Warning! Danger!" means "Warning! Danger!".
Rule number three: If you really can't be bothered to obey the "Spacesuits mandatory" signs, then go ahead and win a Darwin award.
Forget magic. Any technology distinguishable from divine power is insufficiently advanced.
It's probably the nanotube/nanotech pessimists who are ignorant of the law of accelerating returns.
--
Power to the Peaceful
Ok, I'll bite for the flamebait, if only to make a single point:
The MIR space station was first manned in 1986/1987 and was in operation until 2001. That's 15 years of almost continuous occupation relying on core technology from the 80's.
The ISS was first manned by a crew in the year 2000, and considering the major technological advances from the technology found in the MIR space station, I feel that it's safe to say that the ISS will still be in use 15 years from now.
If you really want to be pedantic about the whole issue, replace "ISS" with "Whatever the space station in 15 years will be called."
Even if the space elevator is operational in 15 years, I think most people would agree that it would take more than 15 years to work out the kinks in getting a "geosynchronous city" operational.
But he's a salesman-scientist trying to convince people to invest in his big idea. Are you going to tell them "We COULD build it in 15 years" or "well, it probably won't happen for 40 because {the military-industrial complex, NASA, them welfare queens takin' all our tax money, the Canadians} won't let it." If you want something to happen, it's a better idea to talk it up rather than down!
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
You see, we've done this before... You know, the "monument of engineering in somebody else's country" thing? So where do we build this thingy along the equator??
...Let alone defending the site from the world village idiots.
Let's take a look:
Guatamala
Honduras
Congo
Gabon
Dem. Rep. Congo
Uganda
Kenya
Somalia
Indonesia
Are you fucking kidding me??????
Yes, I can see this one happening in the very near future. Just the places to plant a multi billion dollar space elevator, right? The only country I'd even consider building this thing would be in Singapore, depending on how much equatorial leeway we have to play with. I mean the science is one thing; Great yeah, we have the money and the technology, lets build this mama! But actually breaking ground on this thing is a political nightmare of epic proportions. Stability of the local governement is just as big, if not a bigger issue than "can we build it/how much?"
The fact that the builder is going to want to make money off it once it's built is another huge issue, severely limiting the number of sites. Unless you want to ship all your ultra high-tech parts halfway around the world to, say, Somolia?
Price to build isn't the only thing the government is looking at here and Bradley is a fool if he thinks that's all that's stopping this from moving forward.
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Wouldnt such a long cable from space downto earth generate zillions volt of static electricity?
First off, it's not nearly so simple. Since the space elevator is tapered (in fact, a non-tapered elevator is essentially impossible around Earth), there is a weak point near Earth; this is your bottleneck. As soon as a craft passes the bottleneck, you can launch another; with Edwards' design, that's every 3-4 days. The entire trip is about 8 days.
Edwards' proposal *is* an up-only design, which I complained about on the message board (getting people out of orbit, while easier than in, is still quite dangerous and uses significant fuel). You can't just fire a little rocket to get out of orbit there (although you could slowly decelerate things with ion drives; wouldn't be too great of a solution for people, though).
There are plenty of ways for elevators to pass each other at high speeds when you're past the bottleneck; there are even more if you ditch the "flat ribbon held with rollers" concept and go to a "mesh" design, which can be climbed with teeth from one side only and has better resiliancy . If you allow down-climbing elevators, and keep your elevator size small to enable fast launches, energy recovered can be transferred to up-climbers, cutting down on the energy expense for the up-climbers (which makes up most of the cost, since power beaming is quite inefficient).
I'm an owl exterminator!
Small problem with this. If you send a payload up the elevator without sending and equal mass down the elevator, you change the center of mass of the system. Every load you send up pulls down the top of the elevator a little bit. You'll either need to boost the top of the platform or you'll need a huge counterweight in orbit so the mass of payloads is negligible compared to the mass of the counterweight. I'm sure these guys know more physics than I do, so I really hope they have an answer for this small problem.
The elevator must be so long because it's not the center of mass that must be in geosynchronous orbit, but rather the center of gravity. Portions of the elevator close to the earth will experience much greater gravitional forces, so additional material beyond geosynchronous orbit is needed to compensate.
A basic formula to solve for the required length and illustrate this balance is:
integral(density(x)*[G*Me/x^2 - (2*pi/T)^2*x],dx) from re to (re + length) = 0
where:
density(x) = linear density (kg / m) of cable at altitude of x meters
G = gravitational constant (6.673e-11)
Me = mass of earth (5.976e24 kg)
re = radius of earth (6378137 m)
T = rotational period (~86150 s)
Carbon nanotubes, if the hype is real, are a much better VC investment than most of what we're still doing in Silicon Valley. So is he real or not?
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Actually, you would leave most of it at the top - it's much easier to get down the quick way, because a landing craft is much simpler than a rocket that has to get up into orbit. So you'd haul a bunch of landing craft up the elevator, and people who want to head back down take the express lander. Not sure if the right design is mostly a parachute or more likely mostly a glider, but it means you don't have to take a long slow trip through the Van Allen Belts - just a quick drop.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
KS Robinson has some rather spectacular accounts of an elevator collapse in one of the Mars books (Red or Green), pretty destructive. Is it known whether his portrayal is accurate?
I am curious: how do you calculate the weak point near Earth? Genuine question.
My thought sugguests that the point which is under the most strain is actually at geo-sync -- the 'balance point'.
Also, a minor point: the hard part really _IS_ getting into orbit. It would be _nice_ to come back using the same system (and if done correctly, as you say, very nice indeed) but, for the most part, once an object lets go of the tether, it will NEVER be allowed to get near it again. EVER! Because you would HAVE to attach to the tether at geo-sync orbit -- or at least geo-sync SPEEDS -- which as I would guess you know, but others may not have considered -- are NOT the same thing. I am not justifying poor design; rather I am stating that if simplicity states that the first design be a flat ribben roller design, so be it. Reduce the risk, make the first one a roller, and for the sake of the Gods above, make #2 allow for return trips!
Not that I would ever want to come back......
The skyhook would act like throwing a wrench across the positive and negative terminals of a car battery - zap/boom/need new battery and new wrench.
So we're looking at a combination of ceramics and carbon fibres, and a (pretty much) free ride in terms of power.
http://www.spacetether.com/ Another suggestion is to make a long cable that hangs in free air, from a station in a GEO altitude to a drop towards suborbital space. So it will be dangling around 100km or so above the ground. Since it's not anchored to the earth, you can probably skimp a bit on the material's strength of the tether. A first-stage rocket will deliver the payload, which will be taken by the tether when it 'docks' with the spacecraft. The only issue I see is that the 'hangtime' of being in suborbit should be long enough to complete the procedure, and it would take some work into getting the craft going at the same speed as the tether in orbit.