Slashdot Mirror
Going Up?
An AC points us to this article about the space elevator concept, once solely the realm of science fiction but now coming a bit closer to reality. The main problem seems to be the lack of some material with the ludicrous tensile strength required. Oh, and an asteroid to anchor it. And the willpower to actually build it. Check out the slashdot discussion of an earlier spacescience.com article on this idea as well.
Not a silly question. :)
I used to think about this when I was a kid, not knowing too much about how the atmosphere stayed where it was.
Nah, a big tube into space wouldn't leak out our atmosphere simply cause gravity keeps it in place.
Zero Kelvin
neux.org
...done that.
Thank you.
-- Patrick Bateman, Esq.
All the greatest failing of the whole Space elevator concept stem from the idea that this elevator goes all the way up in a single step.
:). Those will usualy have a way out. I.e. Back down to the last platform.
How about the 1st step going to a platform supported by a cluster of blimps that will drift a little with the wind, but only as much as the fans let it. This platform will nead refueling by conventional means. No bigy.
Above that you have another platform in the stratusphare kept stable by jets.
And so on ontil you get out to the last haul into orbit.
breaking it up this way achives several things.
#1 if it falls it will just be a part of it. Dangerus but a lot less so.
#2 It should be more stable.
#3 It brings it somewhere within sanity. I.e. We could build some of these stages already.
#4 when there is a failure somewhere on the elevator there is usualy a stop so not everyone will be left dangling on the wire. Only a few
This 31 mile tower is ridiculus. For now. A few baloons hovering at 31 miles up is not however. Ask your local metrologist.
PS: Be carefull with how the baloons are constructed. We don't want them floating to high, deflating, faling or exploding.
--= Isn't it surprising how badly I spell ?
I don't know where to begin with this one.
First of all, Storrs-Hall just described a "mass driver", but one propped up on a 100km high tower for God knows what reason. Which proves:
He doesn't know anything about orbital mechanics, but just thinks you need to "point up to get into space". Well, that's probably unfair; he at least got orbital velocity about right.
He certainly doesn't know anything about mechanical engineering, or he'd realize that making a 100km structure that will support tension may be possible, but making one that won't buckle under compression is ridiculous. Buckytubes may have a hundred times the tensile strength of steel, but they still bend real easy...
Honestly, now, has Slashdot become infested by morons? Look at all the crap that's been moderated up on this article! There's the "won't it suck away all our air" question, the "will it change our orbit" question, and the mumblings about shear stress...
Don't take this the wrong way: those are all valid questions to ask, I don't think they should be moderated down, I hope they all get accurate responses, and I hope the responses get moderated up. Ignorance is correctable, and the right way to correct it is by asking serious questions.
But could you imagine this kind of thing happening in a computer science story? Would someone who asked "Won't Lunix let the hackers steal my computer cause it's open source?" get stamped with +1, insightful?
Ok, done ranting now. On to your question.
Serious question: Wouldn't such a thing affect the earth orbit?
Quick answer: Yes, but not so you'd notice.
Building the beanstalk, if it were done with asteroidal materials, would add mass, angular momentum, and an increased moment of inertia to the Earth. Depending on how the asteroid was captured, this could raise the earth's orbit slightly, but would leave the rotational period (length of a day) unchanged. Launching interplanetary vehicles from the beanstalk would remove angular momentum (and a little mass) from the system, slowing the rate of a day slightly.
If the beanstalk was built with terrestrial materials (building one thread first and hauling the rest up on that), it would increase the moment of inertia of the planet-beanstalk system slightly, without adding any angular momentum. Again, the day would be slowed slightly.
But, the key word here is "slightly". By slightly I don't mean days that are one second longer, I mean days that are (1 + ~10*(mass of beanstalk / mass of earth), which works out to something like 100 picoseconds, longer. Use the beanstalk to launch continual interplanetary payloads for a few millenia, and maybe we'll slow the rotation of the earth down by a microsecond. This is all back-of-the-napkin arithmetic, of course, but if my conclusions are too optimistic by a factor of a thousand I'm still not nervous.
the only point in the tower where you can drop off and be in orbit with a little push is at GEO.
Almost correct; the only point where you can drop off into a circular orbit is at GEO; there's a huge range of hyperbolic orbits you can get into (well, hyperbolic w.r.t. the Earth; enough to take you to the inner planets at least) by dropping off the tower above GEO, and a range of elliptical orbits (including one with perigee in the upper atmosphere, making aerobraking into equatorial LEO a cheap possiblity) you can get to by dropping off the tower below GEO.
Throw in some high efficiency rockets (ion engines, plasma rockets - all the sorts of things you can't use on a launch vehicle because they're too low thrust), and you could get into any Earth orbit with a lot more payload, a lot cheaper than with a conventional rocket.
Or perhaps I should say marginally cheaper; as the amortization of the original construction cost should be considered. Of course, building this thing means manufacturing thousands of tons of buckytubes, each thousands of kilometers long. IIRC, current buckytube manufacturing is on the order of $2000 a gram, for micrometer-sized things that might be useful in electronics, MEMS, or nanotech, but certainly wouldn't be as a structural material. We've still got a little technology to research...
Do you realize how much energy our Sun is spitting out every second? And how little of that energy happens to impinge on this tiny planet for us to use?
How about matter? I'll spare you the numbers, but it wouldn't take a very large asteroid to supply our entire civilization's structural metal requirements for centuries, and to provide enough mass of everything else to make the phrase "precious metal" an oxymoron.
There's a nice Kuro5hin discussion going on right now about overpopulation, including the question of what is a "sustainable" population for humanity. The answer isn't encouraging; our fossil fuels won't be around in a few centuries, our fissionable metals will give us a few centuries more... and then what? Solar power? Not concentrated enough, unless you've got a plan to reduce our population 10-fold, or pull in extra power from space. Fusion? That's better (assuming we get it working eventually), but then you run into the problem that the cleanest fusion fuel, He3, only exists in quantity on the Moon and outer planets. Even if you don't see the value of going into space to support life there, eventually we'll want to leave this planet to better support life here.
The solar system has the resources to support quintillions of people; unfortunately for us an insignificant fraction of those resources happen to be on Earth.
An elevator to nowhere. Imagine how silly it'd look.
So anyway, like I said, you've got it exactly backwards. It would be an elevator to everywhere.
You bring up a good point. Not only is tensile stress important, but the "cable" would be under very high shear.
People I'm quite admired abotthis discussion. I have seen LOTS of vapourware stuff in /. I have seen people calling for panic while on Y2K.
But your COLLOSSAL lack of physics is, for me, extraordinary. It's just fantastic to see how people go by things like "bringing pieces of Space to Earth", "elevators". How you can forget that Gravity decays at the square of the distance? Do you know what is angular momentum? And how can you dare to think about something pushing this elevator up in vacuum, by itself. Hey, as anyone forget Newton's Third Law? Sorry to be so flamously bitter, but do they still teach it on school?
And what about friction? The stuff is there and no one will kick it out...
And some people come here moderate my comments to 1 while pushing other weird fantasies up? People give me a break. If anyone of these will call himself a Space Geek, then please get to the open and look at that damn Space. Look at it and then look at your own feet. Saw them? You are bound to this piece of dirt. And this damn piece of dirt will be you damn home and grave because you don't know a thing about the world you live in. Like 1000 years ago, you are still a serv of your own ignorance. And you are cursed to be so because you wish more for your feet than for yourself...
And with regard to the vacuum question, what do you think stops our atmosphere from disappearing into the vacuum of space at the moment? Why, gravity of course (and a little protection from the solar wind courtesy of our magnetic field).
So let's see.
We lack the materials science to build it, the transportation science to obtain the counter-weight, and the funds to make it all happen.
We've got everything else, though. We're home-free.
-
The space ramp is about 100 km high and 300 km long, with a linear induction motor running its length. You take an elevator up to one end, hop on the induction motor, and get accelerated at 10 G for about 80 seconds. This puts you in low-earth orbit, at an amortized cost of 42 cents per kg. Prior to amortization, you'd be paying about a buck a kilogram. The cost for space shuttle launches is about $10K per kilogram.
WWJD for a Klondike Bar?
Uh, so what exactly is considered "launch cost" with space elevators? Is it merely the price of getting a payload delivered to orbit once the thing is built (theoretically)? Well in that case I can launch comsat sized payloads for about 75$ using a linear accelerator, oh yeah, once one is built and we have some vehicles to use on it and whatnot. Space elevators are nice prospects for societies living a hundred years from now that need to make regular orbital runs to space stations and lunar cities. In 10 to 20 years we may have the ability to make labrotory quantities of the requires materials to make a space elevator but don't think a bellhop is going to be announcing "stopping on the third, fourth, fifth, floors and low Earth orbit". In 20 years unmanned orbital delivery vehicles will be the norm and any manned flights will be made by more specialized vehicles. Why the specialization? If you have a low overhead vehicle that just transports people and consumables to and from the space station(s), you're saving money on excess vehicle you're not also sending up to the station. Rather than the space shuttle imagine something more near the size of a Lear jet transporting crews and consumables to and from the space station(s). A similar system could be used to cheapen satillite launches, only using a vehicle designed soley for unmanned payload delivery. I think one of the biggest reasons for this is adapability, right now there are not even a handful of facilities that are capable of launching the space shuttles. If the scope of the vehicles was reduced you can also eliminate some complexity in terms of support. Any desirable plot of land, maybe locations with higher elevations than Cape Kennedy say...Colorado, could be used to launch a smaller space vehicle. Johnson space center is still going to manage the launch, if you're got addequate support facilities at the launch site you don't need a whole lot else. This is a MUCH more reasonable expectation in 20 years than space elevators. It isn't like I don't like the idea, the concept is more of a pipe dream than anything else right now and probably will continue to be for a good stretch of time yet.
I'm a loner Dottie, a Rebel.
Sure, make it tall enough for the top to be in a geosynchronous orbit.
But wouldn't all the elevations below that be in faster orbits? Even if it had the tensile strength to survive, wouldn't it "stand" with one heck of a gimp in it?
--
Sheesh, evil *and* a jerk. -- Jade
It does seem like experiments with tethers show they are balky and hard to work with. It may just be a matter of learning the right materials and techniques, but I expect that there will be a lot of failures before there is anything like reliable success. This may be part of the learning process, but I expect it is unlikely that public support for such a project would continue beyond the first couple of disasters -- the public has little appetite for failure, as necessary as it may be on the road to success.
By the way, my wife's an oceanographer, and they sometimes deploy experiments on cables that can develop knots which occupy a volume larger than the ship deploying them (the technical term for such as knot is a "wuzzle"). Unless you could keep the series of long lines you would need to hoist the final tether taught and unbroken, you could end up with a knot the size of a large city. If the line were made of an ultra-durable material you could have a very interesting situation on your hands.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
Unless it breaks.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
This will cause the cable to be under tremendous stress; the satellite pulls it into space while the earth pulls it back. I'm not an expert, but I conclude from this that in the middle of the cable the stress on the cable will be more than twice earth's gravity pulling on half the cable....e.g. if the cable has to be 20000km long and it is 10 grams per meter, it would be 100000 kilograms weight hanging from the cable...and an equal force the other direction. That makes a force equal to the gravity on 200000 kilograms...nice:)
Experts: please correct me if I'm wrong.
0x or or snor perron?!
I've heard the numbers before, but I can't recall off the top of my head...
I know for certain that current "shipping costs" to get into space are roughly US$10K/lb. The space elevator should reduce that to something like US$200/lb. if I remember correctly (it may be lower).
Never forget the reliability factor. We think space shuttle flights are routine, but they're not very frequent, which means the low number of disasters is primarily due to the low number of flights. From what I've heard directly from NASA, if one shuttle were launched every day, we should expect to lose one every year, give or take a few months.
I take pretty much the opposite position, since I've seen some of the numbers and caught a glimpse of how things are run. Unfortunately our governments don't like sharing information (cold war habits die hard, I guess) so frequently scientists from different countries are not allowed to collaborate on experiments. To me, if scientists from different nations can't work together, there is no real purpose in having an "international" space station.
As for propulsion, what type do you mean? A space elevator would lower the cost of getting into geosynchronous orbit tremendously. From there, it's much cheaper to go anywhere else. Just about all of the new propulsion schemes I've heard of either don't produce enough thrust (ion propulsion) or too much radiation (nuclear) for the first part of the trip.
Robert L. Forward also does a lot with tethers/elevators and other radical propulsion systems (including monopole magnets) in his books, too. I highly recommend his book Dragon's Egg, about contact between humans and aliens living on the surface of a neutron star(!)
No amazon url due to patent madness. Choose any online source you want for more info...
--
Friends don't let friends misuse the subjunctive.
I have attended several panels by Dr. Robert L. Forward on the subject of space teathers and elevators using current materials. Interested parties should check out his company, Tethers unlimited Inc as well as his personal site. I don't know where he will next be lecturing, I last caught him at VikingCon 17 (Western Washington Universitie's SciFi convention).
Realities just a bunch of bits.
As I recall the electrical energy costs are around US$1/lb to GEO, and since the propulsion and guidance uses no physical contact with the elevator there is essentially no wear and tear. OTOH, there would be huge construction costs to write off, but it would still probably not cost more than, say US$10/lb assuming a large amount of traffic.
/Dervak
An interesting article, but a little light on the details. There is a really good piece on how space elevators work here.
Last night I shot an elephant in my pajamas. How he got in my pajamas I'll never know.
on the 150,000th floor?
:)
I doubt there's enough Mentos in the world to get ya out of that situation
========================
63,000 bugs in the code, 63,000 bugs,
ya get 1 whacked with a service pack,
--- Grow a pair, liberals... stop letting the Republicans bully you!
> I don't know about you, but last time I checked
> space was a vacuum. If we put a platform in
> orbit that had an elevator going from earth to
> outside our gravity well wouldn't it serve as a
> tube to just suck our atmosphere out into space?
That is exactly like saying that if I drop a drinking straw into a glass of water, the water in the glass will spontaneously shoot out the top of the straw and empty the glass. Clearly that would never happen with a straw that was 50 cm long, why would it suddenly happen if the straw were 32000km long?
Slashdot monitor for your Mozilla sidebar or Active Desktop.
Think guyed tower, not building. The problem is dealing with wind loading for the part of the tower that's in the atmosphere.
-
Chemical rockets.
Chemical fuels aren't powerful enough for useful space travel. Even with the best possible fuels, you
either need disposable stages or have tiny payloads for the size of the craft.
Heinlein pointed this out in the 1940s.
-
Nuclear rockets.
Too messy. The NERVA program made real progress,
but open-cycle nuclear reactors spray radioactive waste. Closed-cycle ones are too heavy, and messy if they crash land. Orion, the A-bomb powered spacecraft, was even worse in that regard.
Still, if you launched from, say, halfway between Cape Horn and Antartica, where South Africa once tested an A-bomb without bothering anybody, it might work.
-
Antimatter propulsion.
Dangerous, but feasible. Antimatter can be contained in electric and magnetic fields. Portable containers for antiprotons have been built. If anything goes wrong, all the energy comes out as gamma rays. Another one of those "the launch site had better be really remote" launch systems.
-
Laser launch. A big laser on the ground
heats up water in the spacecraft to make steam.
May be feasible for mini-spacecraft.
-
Antigravity.
We have no idea how to do this.
But it might not require new physics.
-
Beanstalks, tethers, etc.
Requires really good materials in huge quantities, along with some other big-time means of space travel for
the construction.
-
Winged launch. The Pegasus rocket was launched from a B-52, and souped-up fighters
have made it to the edge of space.
Helps the fuel problem a little, but not as much as is really needed.
-
Cheap, dumb boosters. The original Von Braun plan: mass-produce lots of cheap disposable rockets,
build a big space station, and operate from there.
Boosters have been mass-produced as ICBMs,
but never got cheap enough.
And that's the way it is.I don't remember where, but I read an article a while about about buckytubes. The basic idea is a cylinder of carbon atoms with end caps in the shape of half of a buckyball. The interesting aspect is that creating them is relatively simple. Eventually, you end up with a pile of soot and some buckytubes. Well, they have enormous tensile strength and it had been suggested that they could be used in a space elevator (if they could be produced in large enough quantities).
On an interesting side note, Clarke had originally written about a space elevator connected to a tiny island, but I can't remember the book (it was before 3001). I do recall that the island was conveniently very similar to Sri Lanka (where Clarke lives) but moved south to make the physics work.
"I believe that a scientist looking at nonscientific problems is just as dumb as the next guy." -Richard Feynman
No, a meteorite, according to the dictionary, is a meteor that reaches the surface of the earth without being completely vaporized, which might describe it after some enormous disaster (terrorist attack?) which brings it out of orbit and down on our heads. While in orbit, the appropriate terms would be asteroid, planetoid, moon (it's in orbit around the earth), or (possibly) moonlet (because of its likely small size).
"Bite me, it's fun!" - Crowe T. Robot
About the outer endpoint of the system: typical designs use a large mass (like a small asteroid) at the outer end of the cable. Since it's beyond geosynchronous orbit but still moving around Earth once every 24 hours, it's going too fast for its orbital altitude; it therefore tries to move away from earth, but is kept in place by the cable. The result: enough tension to hold the cable "up." You select the tension by choosing the mass and its location relative to GEO. (Alternatively, you can make the cable longer to achieve the same result; but cable's expensive, while asteroids are relatively common.)
To answer your question about connecting it to the ground: The proposals I've seen usually put a large "foundation" in the ground, and attach the bottom end of the cable to that. A rather similar thing gets done at the ends of a large suspension bridge: the cables at each end are pulling toward the center of the bridge, and must be anchored. I suppose an alternative would be to attach it to bedrock, but I think I'd rather engineer the attachment -- that way I would know exactly what it's capable of handling.
---
---
Politics is about making compromises. Religion isn't. --Michael Horton
---
---
Politics is about making compromises. Religion isn't. --Michael Horton
The URL goes to the scond part of the article. See:
o gy /space_elevator_001226.html
r d_ tethers_000328.html
http://www.space.com/businesstechnology/technol
The reality in the article is next June's space tether experiment in generating electricity (using the power directly for spacecraft propulsion):
http://www.space.com/sciencefiction/books/forwa
Of course the best known material to be strong enough for a space elevator turns out to be buckytubes...
John
ourpla.net is your planet
Think of it this way: Which is cheaper: Riding an elevator to the top floor of a skyscraper or using a helicopter to do the same thing? A shuttle ride is around $22,000 per kilogram today. The estimates most people put on a space elevator is around a buck or two a kilogram.
Today, there probably isn't enough practical use for this to justify the expense. In the future, especially when we start mining the moon and/or asteroids, this will become a big issue.
Another point is that a space elevator can actually serve as the initial boost for interplanetary trips. The top end of the elevator is actually above geostationary orbit (the center of mass is at geostationary orbit - 35786 km) and as such when you figure the math using a conservative 36,000 km orbit, you get the fact that the top end is actually traveling well over 225 million kilometers in 24 hours or just under 9500 km/h (roughly 5900 miles/hour). This saves a LOT of fuel costs. You basically just wait until the right point and then "let go" and you're on your way to the moon, or mars, or....
Assuming this beast gets built, we have to keep in mind that at first (and, I think, for a very long time) there will only be one of these things.
Its cost effectiveness (and it's appropriateness for use by individual private passengers) must take into account the cost of transporting the people and cargo across land to the site of the tether.
I have no idea how to crunch these kinds of numbers. Has anyone else done so?
--
Accountability on the heads of the powerful.
Power in the hands of the accountable.
but, take the thought experiment to the extreme, if the tube was long enough and extended far enough into space, and you could initially fill it with air, would it not act as a siphon? But, in regards to the initial question, the air in the tube doesnt know, and isnt acted upon by any additional forces, then the air right next to it on the outside of the tube.
Sneakemail is to spam filters what an ounce of prevention is to a pound of cure.
actually, after thinking it through, it wouldnt end up like a siphon, the air inside the tube at the far end would either escape, or get pulled down, until the conditions in the tube matched the outside of the tube, like a big barameter.
Sneakemail is to spam filters what an ounce of prevention is to a pound of cure.
Serious question: Wouldn't such a thing affect the earth orbit?
Also, the thought of having one doorway to outer space, under the control of some political force or another, does not strike me as safe. Considering the kinds of mass destruction that can be wreaked on the rest of the work from orbital heights means that this would not only be the space elevator, it would also be a major weapon. Lets face it, once something is in orbit, landing it in a particular spot is not that difficult. For those who do not believe, go get a copy of Navigation for Space Flight, by Prentiss Hall, I think (it's been a while). At the kind of energy levels we are talking about here, you don't have to be precise.
Besides, I want my OWN fricking orbital shuttle. I've got places to go besides Clarke orbit.
*whup* "Get along, little electrons. Heeyah!"
The purpose of this elevator is not to go up magcially by itself. The point is the following: rockets have to carry their own weight plus the weight of the propellant which is unfortunately the largest percentage. An elevator just needs a motor to pull itself up. You could even imagine an elevator with solar panels to slowly climb its way up by grabbing th cable. Apparently these poeple propose the "pulling" to be done with magnets but the principle remains the same.
If you are found of Dyson spheres, beanstalks, spacehooks, terraforming and other stellar husbandry, check out the following site, full or ressources on these topics:
Megascale Engineering
I code, therefore I am.
And this wouldn't really be a step in the right direction. Sure, research into new materials/engineering techniques would be fruitful, but what is this really?
An elevator to nowhere. Imagine how silly it'd look. :-)
Wasn't it the huge diamond at Jupiter's core that gave the 'ring around the earth' the tensile strength required?
All we need to do is find a bloody big diamond, or gain control of matter at the molecular level.
Or Jupiter can blow up. That would work as well...
From the top of my mind I can think of 3 main reasons that have driven science all along history: Practical Reasons, wars and humankind endless curiosity. I guess that for every advance in science we can find a bit of each in it. Reasons for the elevator? Practical: Cheaper and safer launch platform for communication satellites, elevator for the first space tourists, cheap way to send labor to orbit. Wars: Easy and fast way to put spy satellites in orbit, transfer funds from launching to R&D, build an orbital defense/offense system, space wars. Curiosity: A challenge, a step forward towards space colonization, a way to find new questions. Pick the one you like most Personally I like to think that the third is what drives us... but I'm naive