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Space Elevators Going Up
MikShapi writes "CBC is running a new piece on the Space Elevator. Nothing dramatically new, as we're all still waiting for one of the many Carbon Nanotube research centers to announce they reached the famous 100GPa red line from page 10 of the NIAC Phase 2 Report, thus obtaining 'unobtainium' [pun intended], the material necessary to build the Elevator. The report predicts this will happen during the course of the next two years or so. It's then that the fun really starts - A REAL all-out space race, open to everyone with will and a national budget, winner probably getting to own space [read last paragraph]. In the meanwhile, we can all spread the word, discuss, debate and brainstorm every nook and cranny of the program here on Slashdot, and give Edwards a shoulder by giving the program every bit of mass-exposure we can."
Weightlesness, radiation, and hard vacuum.
Will they have emergency override controls on the cargo deck? Watch 'Aliens' if you don't understand why this is necessary.
A REAL all-out space race, open to everyone with will and a national budget, winner probably getting to own space
I predict that there will not be a space race, because the cost-benefit isn't acceptable yet. If this technology is only 2 years away (doubtful again), then there would be massive funding to accelerate the program if there was enough interest. Lack of interest now means that there is probably not going to be much interest when the nanotubes arrive.
DoggGetting 100 GPa for carbon nanotubes composite is one thing. Getting 100 GPa on a 100000 kilometers carbon nanotube composite is another.
I'm more interested in the length of the nanotubes than in their strengh since increasing the strengh is quite easy (basically all we need is to increase the fraction of carbon nanotubes in the composite) compared to increasing the length of the composite.
Iraq: war to save the U
"If the whole thing fell somehow like you cut it at the counterweight, cut it way up at the counterweight, it would wrap around the Earth a couple of times," Laubscher says.
Well, that's fine. Calculate the length of that sucker just right and you've got a quick, exhilarating way to travel from one point on Earth to another.
The coolest voice ever.
thus obtaining 'unobtainium'
OK for someone who can hardly remember a thing about High Scool Chemistry, Unobtainium, what's that? A new term for good karma?
Karma? Hey I just call it as I see it.
In the post-9/11 world, the first space elevator, built by the United States, would be a tempting target for terrorism.
Not if our brand-new Department of Homespace Security has anything to say about it!
Imagine, if you will, a solid 3D column of security, with an outer edge in the shape of the U.S., starting at the U.S. and extending infinitely into space. I think if we tried, we could even make it glow the whole way. Put a scare into some of those E.T.'s.
The coolest voice ever.
Almost exactly on the equator and above a lot of the weather.
"At year fifteen the first entity has six cables up including two 106 kg cables, has a manned station at geosynchronous, has recouped much of the construction cost through selling two cables and through hundreds of launches on its eight cables,
and is beginning construction of a Mars cable"
There is plans for a mars cable now? Isnt that um, impossible given our orbits in relation to each other?
It's nice that we're on our way to creating the materials needed for a space elevator, but where are we going to find a big enough rock to attach to the other end?
Where can I obtain some unobtainium?
http://www.beyourowneviloverlord.tk
http://www.frozenchickenthrowing.tk
http://www.killercamel.tk
When this technology finally comes into fruition, would it not basically put the ISS out of buisness ? You could basically do all of the things the space station does but also be able to lift and unload new cargo without launching rockets. And if this technology is only 2-3 years away, won't this be ready before the station is even built ?
If the dollar is an "I owe you nothing", then the Euro is a "Who owes you nothing." - Doug Casey
Second Floor Scottie!!
Whenever a space story is brought up, some person always brings up the argument that perhaps we should spend money on the poor instead of a useless space elevator (or whatever the space story du jour is). I don't think they are arguing correctly. Space is just as important to human advancement as feeding the hungry, curing chronic diseases, and providing a livable environment is. I don't think you can order these in importance, they are all important.
But they go hand in hand with each other. Unless we truly believe Matthew 5:5, that the weak will inherit the Earth, it will take a worldwide view of humanity to move us to the next stage of human advancement which is the eventual separation of humans from the Earth and into the galaxy. We can go this alone, leaving the world's poor to their own devices, while the space superpowers leave them behind. However, when the day comes that certain small groups of humanity take to the heavens leaving this world and venturing off into the depths of space, how will history treat those of us living now who failed to hold the hands of those unable to stand with us as we raised humanity to new heights?
The space elevator is a great achievement. Hopefully we will begin to have a true space-based space program that is not dependent upon sending rockets to the space station. This would be the largest step in the path to Earth separation since the first manned space programs.
However, taking steps only with our strongest leg means we are still limping. We must strengthen all our limbs as members of the human family, IMO.
I have been pwned because my
The Fountains of Paradise by Arthur C Clarke and Red/Green/Blue Mars by Kim Stanley Robinson. Both discuss the politics and sociology surrounding the construction and use of a space elevator. Good books, well worth a read.
Tubal-Cain smokes the white owl.
Look for the AFL/CIO to get in on the act, Can you imagine how much money you could hide/steal/launder on a construction project of this size !
In the article they estimate that it would require 650 tons of material. Christ, how many kilograms have we made to date! A two year timeline is unreasonable given our current limitations. Yes, it would be nice if we did have a space elevator, however I do not see it becoming a possibility in this decade. Do we not need more expertise in manufactoring and manipulating these materials? Has anyone made any mathematical models that predict the stress etc... that an elevator would need to undergo?
Dang, over 300,000 geeks on slashdot and i'm the first to say this!
Why not create a chain of bouyant cables instead of focusing on strong and light ones made from carbon nanotubes??
Although there is a "Q" in Quito
I was at that NIAC conference a couple years ago when Brad Edwards presented his Phase 2 results and I have to say this was one of the most inspiring things I've ever seen.
Listening to him go through all the numbers and technical details you're left not only with the amazing scope of the thing but the feeling that, ya know, we might just be able to build this thing!
G.
Such is the case with a group of scientists from the National Research Laboratory in Los Alamos, N.M. (''Los Alamos'' is Spanish for ''More than One Alamo''). According to an Associated Press story that I am not making up, these scientists are proposing to build an elevator that would be 62,000 miles high. That's right: 62,000 MILES, which is 32 million stories. At the top would be a revolving restaurant serving what the scientists promise will be ''really mediocre food.''
- Dave Barry
"If you are an idealist it doesn't matter what you do or what goes on around you, because it isn't real anyway."-R.P.W.
build one there first maybe?
every day http://en.wikipedia.org/wiki/Special:Random
Can you imagine making love in THAT elevator?
Talk about Mile High Club...
The problem with socialism is that they always run out of other people's money. - Margaret Thatcher
I'm a physicist, and I work with carbon nanotubes. In October's Macromolecules, there was a paper put out called "Phase Behavior and Rheology of SWNTs in Superacids". It was done by a huge group of people (for a nanotech paper), including Nobel winner Richard Smalley. A press release about it was posted here somewhere.
To make a long story short:
They did it.
By finding a way to dissolve nanotubes, then slowly concentrating the solutions, they formed a liquid crystal of nanotubes. By extruding this through a syringe, they formed an aligned, macroscopic, nanotube rope.
I've seen this stuff... somewhere, and it looks just like black string.
What's left?
They used tubes grown by high pressure carbon monoxide, which leads to a lot of defects. If they switch to methane, the defects will largely be gone, but the yeild drops.
They probably need to chemically connect the tubes. You can do that with an electron beam, but that would be a pain industrially. I'm sure there's a way around it.
I'm sure that same group of people has already figured out many more problems and solutions than I can think of. I havn't seen anything out about the mechanical properties of these ropes yet, but I would expect something within a few months, and I would be surprised if it wasn't amazing.
I used to be a skeptic when it came to a space elevator, but now...
"Unobtainium".. What about the ground the elevator stands on? There are reasons why bridges are built the way they are. I guess an elevator like this should be built with an optimal energy distribution, so that it dosn't tip over because of a stupid hurricane.
2 Things, Here in Akron Ohio, the Now home of Televangelist Earnest Angley, the building he now offupies was televangelist Rex Humbards previously, Rex started to build a HUGE Rotating restraunt on a pillar, something along the lines of the "space" needles, He ran out of Money before he could finish, so now at one of the highest points of town, a large white tower stands with no purpose, everyone here calls it Rex's Erection
A second note that almost killed me with laughter was , well let me start with I used to be in the building trades, one day while at a supply house, a New blue truck pulled up, the sign on the side ? "Short STEEL Erection" I was dying, they specailzed in Steel reinforced concrete. I always love that one I think they were out of Canton OH
Im constantly amazed how optimistic some people get about a space elevator. The main post and a lot of things other people are saying make it seem like they think technology is the deciding factor in whether or not one will get built. The only reason nobody has really spoken out against the idea is the average person thinks the scientists are smoking some good crack on this one.
This isn't a harmless piece of cable we're talking about. The real barrier is going to be whether or not it'd be dangerous if it breaks or if it's cut. If it'll burn up and IF the burnt nanotubes aren't dangerous then maybe there will be a snowballs chance in *$#@ that the public will ok such a project. You can be guaranteed that if it's dangerous though that everyone will just assume that it will break or be broken intentionally.
the top floor would move much faster than the bottom. Don't remember all my freshman physics, but it seems reasonable that to get to the top you have to undergo some serious lateral acceleration.
You'd also have a hard time interacting with any orbiting satellites (except those in a geo-stationary orbit) because they'd be flying by at 13,000 mph.
"We have to fix the satellite. Here it comes, I'll grab it with my giant catcher's mitt... WHOA! That almost took my head off! Well, at least it won't come around again for 90 minutes."
there is already a ladder that reaches this high, someone should tell them.
The Ladder made out of junk.
But the Japaneses' Ladder seems to be winning.
-- Ben --
The strength of the material is controlled by defects. In a petri dish, the carbon nanotubes have no defects, but there is no way they can make a cable that is more than a few cm long without defects. This will make the strength of carbon nano-tube much smaller. In real materials, the reductions is 3 orders of magnitude. So instead of a meter wide cable, they would need a kilometer wide cable.
They realize that the cables, extending out into space, slow the Earth's rotation causing massive environmental damage. (That's a joke, moderators)
If anyone's interested, there's an interesting example of a space elevator used in the last episode of the anime Gunbuster (Gainax). They basically treat it as a sort of hanging gondola (like the ones you would use to get up a mountainside)
...the 100 GPa number sounds ridiculous.
For context: the most common type of structural steel currently used has a yield strength of 350 Mpa. 100 GPa is 285 times stronger. And stronger isn't enough, it has to be dependable and resistant to cyclicle loading and fatigue, which isn't easy to quantify, especially under such unusual conditions.
To suggest that this can be achieved in a couple of years sounds silly to me, considering whatever material used would a lengthy term of testing and a proven track record before sinking billions of dollars into it.
It'll be at least a century before one of these things actually do anything useful.
Actually, common English translations of Matthew 5:5 state that the MEEK shall inherit the Earth. Additionally, the evolution of the english word "meek" since the time of translation makes it an unfit word for the intended meaning.
A more accurate interpretation suggests that those who inherit the earth are exactly the opposite of weak. Instead, the "meek" originally intended was a word to describe a ready and willing warrior. My university's Bible professor likened it unto the steed of a knight. Eager for battle, ready at a moment's notice to aggressively and unashamedly obey its master. Christ, I think, was referring to those who put intense, unmitigated faith in his Father. That's the sort of "meek" who inherit the earth. [/theology lesson]
Anyway, I do agree with you that advancing technology like this is not necessarily at the expense of helping the poor. It can actually HELP that endeavor. I am of the personal belief that it shouldn't rest on the government's shoulders to prop up the poor. That's the sort of thing with which the compassionate members of society ought to be busying themselves.
--
They need to find an upsidaisium mine. It has
all of the prerequisite properties to make just
such a silly project succeed. Beware that Boris
and Natasha don't find it first.
The column you're looking at is labeled "Altitude (feet) / Distance (miles)". The highest altitude reached is under 100,000 feet, which is under 31 kilometers.
The second link (which says you've got 35,756 kilometers to go) you read correctly.
It feels as though a lot of powers-that-be are reading Slashdot and taking our advice.
Or perhaps these influential types are actually venting their thoughts on Slashdot threads.
I think almost all of your musings on the subject are already covered accross those books.
For people going up the space elevator the ride will take more than a week
Over 80 comments already and nobody has posted the obligatory elevator farting jokes.
One question : the basic plan involves transmitting power through microwaves or laser light, enough electric power to provide the kinetic energy difference to actually put a vehicle in orbit. Why not skip the development of unobtainium and skip trying to put a super long and heavy cable in orbit? Just build the power laser facility 10 times over, and build spacecraft that use a block of inert propellant, heated to millions of degrees celcius from pulses from the laser and pulsed such that the shockwave is a planer wave coming away from the spacecraft. So no nozzles, no rocket engines, no pumps, no chemicals, no fuel, no explosives...all the stuff that make spacecraft expensive and dangerous. Just a block of cheapo rock and a spacecraft built like a cheap copy of an Apollo capsule made by the Russians. Would be safer as well, since in-orbit is pretty safe (there are patches to plug small holes), launches no longer can blow up, and reentry is much simpler and less error prone that with a space shuttle. Finally, that kind of laser would make a rather fine weapon, and would help out military applications as well (so could get some of the funds from the U.S. military budget)
1/625 possibility of 'severe damage' (aka destruction) from the 2031 Leonid Shower is a pretty damn big risk, if you ask me. I imagine that every nation that might get smacked by falling debris would have an objection to this ever going up on this basis alone.
Laugh while you can, monkey-boy!
Instead of each nation trying to build it in competition, why don't we try to build it all together? Maybe this is the event we need to unite as a world, Star Trek stylee...
There are only 10 kinds of people in this world... those who understand binary and those who don't
They insist that one day there will be lots of elevators ferrying satellites, prospectors and even tourists into space.
"If the whole thing fell somehow like you cut it at the counterweight, cut it way up at the counterweight, it would wrap around the Earth a couple of times,"
These all have to be on the equator. If one breaks and wraps around the earth it would take out some others - chain reaction.
Heavily populated areas near the equator are in western Sumatra, Borneo, Celebes, Uganda and of course Ecuador.
At least if you found yourself caught with a VC in this elevator, you would finally have time to really pitch your business plan.
On a serious note, they predict it would be hit, if not moved, by a large space object around once a year. They think they can spot these objects and move it as needed. But what about smaller objects. How much damage will they do? How easily can they be detected? How often will they hit?
And worse, what about deliberately launched smaller objects, radar-invisible small objects fired by a nation that doesn't want another nation to own space.
Has it been over a year since you last donated to the Electronic Frontier Foundation
Probably preaching to the choir, here, but just in case someone hasn't read it... I found Robert Forward's 'Indistinguisable from Magic' to be a pretty good read. If you like the idea of a space elevator, then you'll love the rotating 'space bolo' version, kind of like a bullroarer on ubersteroids.
The earlier posts on 'space bungees' might not be so far off the mark after all.
Anti-gravity? That was *my* little secret! But I never patented it! Boy, was *that* dumb!
If i was in charge of raising funds, then i'd be damn sure that it worked... one gram of Carbon Nanotube costs around 1500$ to produce.
"Oops, we just threw 15.000.000$ out of the window, after 10Kg of it disapeared in the mail..."
On the other hand.. Just because its expencive, it doesnt mean its not worth trying. I assume they keep in mind that a project like this easily can stirr up some anger among the tax-payers, if it fails.
this is probably the most boring sig in the world
Go to the spacestation and say "it's comin' down catch?
Yes, it sounds outrageous, but it's theoretically possible to do this with nanotubes, apparently. As I understand it, nobody has actually demonstrated a macroscopic piece of nanotube composite with this kind of strength though.
True, but the things made possible with such a material would surely attract billions of dollars worth of R&D. Can you imagine what it could do for things like aircraft design?
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
The only problem is that the same nanotube technology that would enable a space elevator will also enable a reusable single-stage-to-orbit spacecraft capable of putting mass into orbit at a much lower cost.
Just to pick some numbers:
Space elevator: $5B each, one 4 ton payload per day
Nanotube composite rocket: $.1B each, one 8 ton payload every two days
In other words, it will never happen.
Cripes, these ships are probably going to be pretty small, aren't they? And there won't be much to do? And it's going to take a week?
I wonder if there's any chance that it could use a maglev system. Japan's at 581kph or so. If you could fly straight up at even 500kph that cuts the trip down to 3 days.
According to page 19 of the report, under the heading of Ribbon Infall,"The raw numbers suggest that the worst case cable infall is not as bad as the best case, nominal operation of current rocket programs."
Granted, they supply no numbers and they explicitly state that they have done no serious quantitative analysis of this, so I'm curious how they came to his conclusion.
Nature has spend along time doing research for us. So you root the thing like a tree.
As for vibrations you make a cable whis is made out of many smaller cables all of them at slightly different tensions so that they vibrate at different freqs.
It's spelled "yield".
Other than that, YAY!
The cable is "holding" mostly its own weight. Therefore, if the material is not at the critical strength, the elevator can't be built. (not disagreeing with you about the difference from lab to real life tho)
For the record I am temporarily disabled and unable to go out tonight
Check your email - maybe you can score some Vi@Gr&.
There is one problem that doesn't seem to be addressed -- the problem of imparting the necessary angular momentum to the elevator car as it rises.
As the car rises, from the point of view of the ground, it will appear that the car is dragging the tether westward. As the car continues to rise, the angle of the tether-bend will increase, pulling the base station down into a lower orbit, If the system doesn't "crack the whip" and snap off the sky station, or induce a huge oscillation in the tether/sky station, it will at the very least leave the sky station in a lower orbit, and the tether "slanted" westward. The more mass you send up the tether, the sharper the slant, and the worse the problem becomes.
The following experiment graphically illustrates the basic problem. The "space elevator" does not behave like an elevator.
Take a long piece of string or fishing line and tie a medium bolt to the end. Go outside to a large open area. Take a second bolt of similar size, thread it through the line, and hold it in your hand along with the free end of the fishing line. Now start spinning in a circle and let the line play out until the bolt is spinning at the end of the line. For the purposes of this demonstration, you are the earth, the fishing line is the elevator, and the tied bolt is the space anchor. You are looking straight "up" the elevator tether at the space station at the "top". Notice how your hand (the base station on the surface of the earth) is moving fairly slowly (with respect to your torso, the core of the earth), but the bolt at the end of the line (sky station) is whipping around at high speed? This means that the bolt on the end of the string has a lot of angular momentum, and the bolt in your hand has considerably less angular momentum. Now let go of the bolt you are holding while you continue to hold the string. The "elevator car" bolt will proceed to travel "up" the string into space until it comes to a stop at the "space station." However, the bolt will NOT simply rise straight up the line like an elevator car. Instead it will drag the line in the direction opposite to the direction you are rotating, and will "crack the whip" somewhere near the end of the travel. When you are all finished, the line will be oscillating "east to west" (forward/backward) relative to your hand.
Not what you may have been expecting based on the conceptually flawed "elevator" analogy.
Now there are limits to this demonstration. For instance, the actual elevator car will be speed controlled, not flying freely like the travelling bolt, and there are massive differences in scale and speed. But even if you solved all the engineering problems you can, the basic problem of conservation of angular momentum remains, and it's a show-stopper.
The oscillation problem could theoretically be avoided by carefully timing the rise of the elevator car, but the killer is conservation of angular momentum. As the elevator approaches the sky station, it will drag the tether westward and pull the sky station into a lower orbit. It can't help but do it, because as the elevator car reaches the sky station, it is going to have to match speed with the sky station. In order to do this, it will have to "steal" some angular momentum from the sky station, and even in a best-case scenario, where the timing is done absolutely perfectly and no oscillation is induced, the system will balance the equation by dropping the sky station into a lower orbit, and leaving the tether "slanted" westward. Bringing the elevator car back down again (perfectly timed once again to avoid oscillation) would straighten out the tether, but if the purpose of the space elevator is to sling things into space, then it becomes clear that the entire scheme isn't going to work. Any object lifted to the sky station is going to "steal" angular momentum from the sky station, and once you let go of anything, you will never get back that angular momentum, and there will be no way to straighten out the t
instead of letting the towers fall over on their side, creating even more death and destruction, there was a saftey that made the towers fall nicely on themselves. like its really statistically possible for BOTH towers to fall nicely on their own volition. HA.
basically with this elevator noodle, you'd just need to break it into smaller noodles that will fall and won't whip around and cause destruction in a 45 kilometer radius.
article here
According to Strong's Concordance, the word in the original Greek is "praus" (latinized spelling) which means mildness of disposition, gentleness of spirit, or meekness. If this page doesn't load, go here, type "meek" into the first line, submit, find Matthew 5:5 and click on the number 4239. This word is close to the modern Greek "praos" which also means "meek."
In other words, Jesus was saying that the humble and mild-mannered will inherit the Earth. You can find this same word commonly translated as meek in 1st Peter 3:4. Also, if you look at the context of Matthew 5:1-13, the opening of one of Jesus's sermons, it's quite clear that he's saying that rewards await the humble and downtrodden. They "are the salt of the Earth" and there is not an aggressive or angry group among "the poor in spirit," "those who mourn," "the meek," "those who hunger for righteousness," "the merciful," "the pure of heart," or "the peacemakers."
I'd be very surprised if Strong's Concordance was wrong on the issue given the context and the modern descendant of the word. I'd love to see some evidence for your professor's claims.
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
Odds of dying on an airplane?
Odds of dying while operating a motor vehicle?
Odds of dying near a motorway?
Odds of dying from a biological/chemical terrorist attack?
Odds of being struck by lightening?
Odds of contracting Human Mad Cow Disease in the United States?
Odds of being a homicide victim in America?
Odds of food poisoning from a food vendor?
Now how many of the countless risky things we do each day are known threats with predictable vectors that could be addressed by ever advancing technology?
You had better hope that your alarm clock does not shock you when you turn it off to hide under the covers the rest of your lifeless existence. It is this exact type of mentality which is plaguing Americans especially NASA. I think it was best put like this:
"If you can't take a little bloody nose, maybe you oughta go back home and crawl under your bed. It's not safe out here. It's wondrous, with treasures to satiate desires both subtle and gross; but it's not for the timid."
-Q Star Trek: The Next Generation
-1 Overrated (Too many big words for me to comprehend)
I shall ask this Professor about this at the next opportunity I have. Probably Monday.
:)
I do regret not being able to reference that--if you'd like, you can reach me at bt3819 AT arbor DOT edu. When I get in touch with my prof maybe I can email anyone interested about what he has dug up on the topic.
My most important correction with the parent of my other post was that meek != weak. The extra interpretations of my old prof were an (I thought) interesting addition.
Perhaps additional torque (and in effect angular momentum) could be imparted by thrusters on the sky station?
Not knowing anything about physics, would it not help to have two parallel cables and drop something down one as something rises up the other?
Or is it not possible to drop something down the cable? (it sort of sounds like it wouldn't be...)
Or how about if the cable-top station had station-keeping rockets? I guess that would sort of defeat the purpose though...
In the free world the media isn't government run; the government is media run.
Not speaking as a physics grad here, and possibly talking out my ass, but I was under the impression that the space end of the tether would be a little outside the balance point, such that (if not for the cable holding it down) it would continually try to fly off into space. Thus, when it's energy was sapped by the launch of a new spacecraft, it would in turn sap the rotational energy of earth to return to it's highest possible orbit.
There ain't no free ride into space: The elevator will simply replace violently exothermic chemicals with the slow sapping of earth's rotational energy.
1/625 is not the odds of the thing falling down overall...that's of the odds of it falling down because of the Leonids in 2031. To put it another way, there's a 1/625 chance that it will be destroyed if it is actually in the sky between 6-12 pm November the 17th 2031.
There's a 1/100,000 chance of being destroyed by the leonids in any one of the 'minor' leonid years. And this is ignoring all of the other mundane risks such as cumulative damage by oxidation and the like.
None of those mundane (or outlandish) things you mention have anywhere near that kind of risk profile.
Laugh while you can, monkey-boy!
There is one problem that doesn't seem to be addressed -- the problem of imparting the necessary angular momentum to the elevator car as it rises.
From which follows two full screens of "sky elevator is falling" whining, ending in this choice quote:
Any object lifted to the sky station is going to "steal" angular momentum from the sky station, and once you let go of anything, you will never get back that angular momentum, and there will be no way to straighten out the tether again.
Swing your yo-yo around your body. Then, swing faster. Notice how the yo-yo catches up after a few rotations?
Funny, isn't it?
The beanstalk *would* lose some angular momentum as the elevator platform rises to the top. It would tilt to an angle, and lose a bit of altitude. But, the bottom end is tied to the Earth, which would be busy pulling the whole shebang forward, back towards a balance.
Eventually, the elevator would catch up, just like your yo-yo. There'd be a very real threshold for the amount of angular momentum you could use. Also, that angular momentum would be regained when the elevator car comes back *down*...
Best bet would be to have two strings, one for cars going up and one for cars going down, say, a thousand miles apart.
Then, the equations would almost always be nearly matched, and you could start moving several cars a week, instead of just 2 cars a month. You *know* that the weight of a car would be squat compared to the weight of the string itself, so several cars at once should not be a problem.
I picture X cars climbing, X cars dropping. The two strings would be arched in a giant pointed loop, bowing away from each other.
Neat, eh?
I have no problem with your religion until you decide it's reason to deprive others of the truth.
You could do something simple to avoid this life offset the laser that is providing the propolusion to the car climbing the elevator. That would take literally no extra expense and only a little bit of mathematics to achieve.
The site doesn't actually run through the numbers or mention how long this recovery time would be. The logic does make sense -- if the tether becomes slanted relative to the surface of the earth (my objection), then by definition there is a lateral component to the centripetal force on the tether, which should allow the sky station to steal some angular momentum from the earth. at some unspecified rate.
The site doesn't actually run through the numbers or mention how long this recovery time would be. If any physics mavens are irritated enough by my parent post to actually run the numbers, I'd be genuinely interested in seeing the solution worked out.
would it be possible to use carbon nanotubes in making soft body armor like vests?
It's remarkably short sighted to argue against taking ALL of humanity a step foward because we're not all on equal footing. We NEED to take this step foward, DESPERATELY, in order to help solve poverty, exploitation and many other ills in the world.
/. You're proposing the scientist's equivalent of the "trickle-down theory"-- ie, "let us experts do our 'science stuff' in space and y'know, eventually maybe some benefit of some sort will reach the rest of you filthy unwashed masses."
This is the most absurd line of arguing I've heard today. And I've been reading a lot of
If supply-side is voodoo economics, then I guess I'd call this is voodoo science. Yes, there are unexpected benefits from scientific endevours that can jump from one area of study to another. But directing resources on space playgrounds, no matter who they're for, when there are people starving and dying and suffering now is pretty brutal. I suspect the only reason you're willing to let those billions of people continue to suffer and die is because they are physically far away from you. If they were dying on your doorstep, I bet you'd have a very different set of priorites. Or if you or your family were in need of those resources, I bet you wouldn't be such an advocate of the space program.
Focusing on a specific scientific problem that directly faces humanity is one thing and I support extending resources to that end. But launching shit into space for its own sake at tremendous expense with the hope to get some kind of as-yet-unknown spinoff side technology as a benefit seems like a tremendous waste of precious resources. We can jack off all we want right here on earth, there's plenty of stuff at the bottom of the ocean or in rainforests or in our weather systems or our own biology all to explore at a fraction of the cost of say, sending a couple of people to Mars in a tin can just to say we did it.
This thing is going to wick the earth's atmosphere out into space. Then they'll feel stupid.
Didnt NASA experiment using a tether miles and miles long to produce electricity? What if the space elevator generate huge amount of static electricity as the "rope" move through space?
Wasn't there an article a while back about how nanotubes go up in smoke when a camera's flash bulb is shown on them? wtf is direct sunlight w/o the earth's atmosphere going to do to em? I hope they're thinking about coating that rope with some sort of space age polymer.
It seems to me that attaching a large rope (for lack of a better word) to the moon and letting it 'hang' to Earth would be worth some thought. Because the moon is tidally locked to Earth, the rope would always be facing down. The distance isn't inconcievible (IIRC, twice the length as the elevator). It would be largely ballenced by the opposing gravities, and the part under most stress would be virtually weightless.
The rope could hang a large distance off the ground, and the space bound object could be raised up to the top of an Earth bound tower, hooked onto the rope, and the it could elevate itsself.
I don't know if it's feasible, or even a good idea, but it's food for discussion.
In the meanwhile, we can all spread the word, discuss, debate and brainstorm every nook and cranny of the program here on Slashdot
/. comments are going to be a key role in the development of this technology.
Yes, I'm sure
I wonder how they'll cite us in the papers they publish?
Wouldn't that actually be four books?
Have you been touched by his noodly appendage?
Stories like this give me a lift.
I predict that a space elevator will make the cost of the lunar landings look like peanuts. I very much doubt it'll happen in our lifetimes.
NASA is the reason space is expensive. Companies like Starchaser and Scaled Composites are the ones who will make space cheaper and will "own space".
Government of the people, by corporate executives, for corporate profits.
I've fiddled with the math for these kinds of things for decades on an old idea called the "launch loop". The dynamics of long tapered cables are not impossible, but they are nasty. Very long cables are not like a stout rope to a fixed point nearby, they are more like reaction mass that vibrates. Think "Tacoma Narrows Bridge", which fell down because 1930's engineers did not take their differential equations up to 7th order.
As a climber goes up, the surface anchoring system must pay out more cable to fill in the less tensioned region under the climber, faster and faster as the climber accelerates up the cable, proportional to the speed of the vehicle, total acceleration (including gravity) and inversely proportional to the mass per meter and the square of the propagation velocity of the material.
This is continuously changing, so forces and velocities at the surface are changing also. The problem is, this is an underconstrained and essentially undamped end-terminated system - as the cable gets very long, you develop big standing wave complexes with only two points (surface and top anchor) to remove or store the energy. Keeping the standing waves from building up is difficult, but not impossible. However, it does add an additional constraint on launch rate; you have to spend a lot of time damping out the waves, even granting that these people are more clever than I am at modelling and removing this energy.
Tapering of the cables, necessary even with magic nanotube unobtainium, makes the math even more "exciting", with the additional constraint that the through-atmosphere sections, along with the sections that dip into the atmosphere during wave motion, have to be thoroughly protected against atmospheric degradation (hint: C + O2 -> CO2 ). The portions of the system below the Van Allen belt have to be armored against atomic oxygen damage. Atomic oxygen will burn off the leading edge of ISS at rates approaching a millimeter per decade; the space elevator will be stationary in the gas field, but there are still a lot of fast moving oxygen atoms up to, and through, the radiation belt.
All motor driven systems have limits to their power-to-weight ratio. To get to GEO, we have to add about 60MJ/kg. If we take 33 hours to do so, we need to move an average of 500 watts per kg (total climber weight) through the (photovoltaic or microwave) energy collectors, motors, rollers, etc. For comparison, a 1500 kg sports car with a 300 horsepower gasoline engine uses 150 watts per kg. However, that underestimates the problem. Most of the energy will be added at the beginning of the climb, during the first 10% of the travel distance, as the climber leaves the depths of the gravity well, so expect thousands of kilowatts per kilogram in the power train during this phase. If there are unexpected variations in the power, the change in climbing acceleration will add more ripples to the cable.
I tried to avoid these problems with the launch loop (see URL below) by keeping the altitude under 100 km and the motors on the surface. Even over those "short" distances, cable propagation issues are problematic. Funny/bad things like lightning, ice buildup, fractally gusty winds, and jittery payload forces require special attention, and all reduce the capacity of the anchoring and stability cables. Everything above the atmosphere is exposed to a steady rain of the garbage that your launch system has accumulated in orbit (it all comes down, eventually). Reentry systems for human payloads (in case of failure) add weight. Problems, problems.
At the end of the day, though, the killer issue is lack of demand. The launch loop, with about the price as a space elevator (+/- 3dB) and using materials and technologies we have had for two decades, can put 80 tonnes of payload into orbit *per hour*, for less than $10/kg. Unfortunately, nobody wants that much mass in orbit, even at that miniscule price. Perhaps "if you build it, they will come", or perhaps you end up with another white elephant lik
Keith Lofstrom server-sky.com
YOU DON'T NEED A COMPOSITE MATRIX! You can repair a broken rope by re-weaving a section a bit longer than its diameter. Ropes are made up of short fibers held together by friction and tension. Friction is tough in carbon, but if you have even three nanotubes filaments, if you cross-link molecules every few hundred atoms along a few millimeters of filaments, you can forget the matrix. (Patent applied for...now--Unobtanium, Inc.)
"...while history is usually explicable it is often irrational" --Roger Spiller
The channel tunnel cost $21 billion and that's just a couple of big holes in the ground. The cost is going to have to be amortized across generations of users. I do agree with your point though.
More people fly from the UK to the continent these days because it's much cheaper, faster and more flexible.
Government of the people, by corporate executives, for corporate profits.
Hi, i'm Johnny Knoxville, welcome to orbital jackass...
"Sic Semper Tyrannosaurus Rex."
Something else to worry about...
"Sic Semper Tyrannosaurus Rex."
Not to rain on the parade, however, back on earth we do still have a lot of growing up to do.
How many wars are still going on?
When will greater minds unlock puzzles like world poverty?
No biggie, Mars looks a lot like the land in the Gaza strip.
Now lets talk some sense.
Space is going to have to become cheap and safe.
Otherwise, lets go back to debating the above.
That said, why not develop current technologies better?
Rail Guns?
Potential Energy converted efficiently into Kinetic Energy using magnets, superconductors, aerodynamics and a smaller amount of safe fuel.
The idea is to create momentum and push closer towards escape velocity while still on the earth and then launch the moving mass into space and keep it going with a lot less fuel.
The example is best seen when trying to push your dead car forward for the first time.
If on flat land, it takes some effort at first to get her rolling, thereafter it takes just a little until you stop again or realize that trying to push her up a big hill was just a bad idea.
This is also seen in the fact that most of a rocket's fuel is used up in the beginning part of the launch. It takes very little to keep the mass going, especially once it sheds enough mass and starts to move farther from the gravity well.
Now on earth we are going to have problems pushing a mass to 330m/s. (air friction and ionization to name two).
So lets get our aerodynamic payload at least to Hyper Mach using a superconducting magnet rail gun, then engage the air turbines and go for some fun with the rocket once out of the stratosphere!
A plug for my really amateur space site:
www.spacecanada.org
I do not agree with you. The best the x-prize achieves is tiny compared to orbit. Just calculate the kinetic energy at orbital speeds verses the potential gravitational energy.
When you do so I think you will find you are comparing GIANT PUMKINS to cherry tomatoes.
Of course - the cherries are always fun!
its not like we're talking about building it out of iron.
And the people already in it are going up and you want to go down?
Powering a miraculous transportation device by bleeding off the Earth's angular momentum? That sounds suspiciously familiar... anyone else read "Signal to Noise" by Eric Nylund?
I'll be keeping my ears open for any reference to "Wheeler."
My deviantArt site
no - I didn't read the book. But NASA has been a parasite before... this is how they put many probes into space... its called a "gravitational assist"
That would be cool if Canada owned space.. Maple syrup falling from the sky like rain! mmm... maple syrup......
in girum imus nocte et consumimur igni
I applaud you for posting a correction. But still, before you made the original post, did it occur to you that maybe these really smart scientists with Ph.D.'s knew something you didn't? Scientists sometimes get something wrong, but don't you think somebody would have run the numbers before dumping all of this money into research?
Mod down posts with a "Free Mac Mini/iPod" sig, they're spam!
Because there is usually a small percentage of the population with effectively total control of the populace that has no interest in letting the rest of the world help?
Imagine trying to provide healthcare, education, and the right to walk in sunlight to women of Taliban Afghanistan...
I hate to beat a dead horse, but seriously: Why do you ridicule the efforts of the x-prize contestants?
At least they are making attempts at going into space. By far and away the most difficult aspect of private attempts for getting into space (and even government attempts for that matter) is the sheer bureaucracy of people who are trying to stop you at every step of the way.
Check out the Space Access Society website for further details, but I find it rediculous that if you had one of those Slaver-designed bio-engineered rocketships described by Larry Niven (a great SF story about bio-engineer rockets as powerful as a Saturn V... just add water and the plant makes you a personal rocketship for just the price of the water and a little bit of sunshine) it would still cost you over $1,000,000 just to file the paperwork to get flight clearance.
Something is definitely wrong here when this is the situation. The X-Prize folks are making some very real progress, and they are following an incremental design and engineering approach that is going to be very sustainable in the long run. If you check out Armadillo Aerospace you will see that they are planning for not if but when their spacecraft crashes/dies/blows up, and they are just going to take lessons learned and move on from there. With NASA's approach they are so paranoid to lose a vehicle that they are completely unable to even launch anything, and refuse to take any risks even after they eventually plan on any launches.
That and the approximately $500 million per launch is really quite overkill, but that is still another point to be made. NASA is doing a lousy job of lanching people into space and it is so obvious now that even a typical congressman can figure it out for themselves.
"In the meanwhile, we can all spread the word, discuss, debate and brainstorm every nook and cranny of the program here on Slashdot, and give Edwards a shoulder by giving the program every bit of mass-exposure we can."
Yes, I imagine that that will make all the difference. In future years, the touchstone of scientific and engineering excellence will be "Was it discussed, debated and brainstormed on Slashdot or not?"
some freakin' kid's gonna run on and hit all the buttons and jump off before the doors close
The heaviest element known to science was recently discovered. The element, tentatively named Administratium, has no protons or electrons and thus has an atomic number of 0. However, it does have 1 neutron, 125 assistant neutrons, 75 vice neutrons and 111 assistant vice neutrons. This gives it an atomic mass of 312. These 312 particles are held together by a force that involves the continuous exchange of meson-like particles called morons.
Since it has no electrons, Administratium is inert. However, it can be detected chemically as it impedes every reaction it comes in contact with. According to the discoverers, a minute amount of Administratium caused one reaction to take over four days to complete when it would have normally occurred in less than one second. Administratium has a normal half-life of approximately three years, at which time it does not actually decay but instead undergoes a reorganisation in which assistant neutrons, vice neutrons and assistant vice neutrons exchange places. Some studies have shown that the atomic mass actually increases after each reorganisation.
Research at other laboratories indicates that Administratium occurs naturally in the atmosphere. It tends to concentrate at certain points such as government agencies, large corporations and universities and can usually be found in the newest, best appointed and best maintained buildings.
Scientists point out that Administratium is known to be toxic at any level of concentration and can easily destroy any productive reaction where it is allowed to accumulate. Attempts are being made to determine how Administratium can be controlled to prevent irreversible damage, but results to date are not promising.
Satellites are steered constantly to maintain the proper orientation(s) for their task. This is why they have a limited lifespan. When satellites run out of fuel they will just float and tumble uselessly, which is why they are properly de-orbited at the end of life.
Satellites are also steered to avoid space junk (the ~10,000 objects tracked by NORAD, etc.). Steering around a thin cable in a known location would be a simple affair, since a tiny adjustment several orbits in advance of the potential crossing will result in miles of leeway.
Another poster mentioned that the cable will also be moveable.
So, sure, it is work to avoid collisions, but no more work than is already being done by anyone running a satellite today.
What if all the research on String Theory and the mechanism of Gravity (IANATP) comes good and a method to repel gravity is discovered, let's say about 2015?
Bit of a bummer for the investors.
when the first plane crashes into the space elevator - ugh
first you get the unobtanium, then you get the space, then you get the women...
but because this is slashdot:
1. Obtain 'Unobtainium'
2. Own Space
3. ???
4. Profit.
Material of this strength allows other methods of space access that may be more efficient.
Tether a platform just a few dozen or hundred kilometers up, supported by rigid hydrogen-filled inflatables. Access it by elevator (but now, the cables can be over-engineered by a factor of 100, for safety). Launch from there, either chemically (standard single stage to orbit), or electrically (linear accelerator). Either way, you are beyond the bulk of the energy stealing atmosphere.
It is possible to build a linear accelerator several hundred kilometers in length, moored to the platform, that would allow launch of living payloads, because the average acceleration would be survivable.
-- -pjk Perry Kundert perry@kundert.ca http://kundert.2y.net
What would a object so large leaving earth have in terms of effects on the earths magnetic field and rotation?
Currently: dry weight 80 tons, payload 20 tons.
;-)
After replacement: dry wt. 2 tons, payload 98 tons
(I mean, the stuff is 40 times stronger!)
Seriously though, availability of this material as a mass product would revolutionize aviation and astronautics long before anybody even mentions space elevators.
So crawl back in your Candy Land box and dream of a reality with nothing but gumdrops and Kool-Aid with Sugar for rain and everybody a smiling happy person %210 safe from any danger what so ever anywhere.
Anybody else smell bullshit?
"our current unsafe systems"
Ask one of John Mohammed's victim's families how safe it is to pump gas.
Jeebus, scared of your own shadow too?! Imagine if we just said fuck it on January 27, 1967 when the crew of Apollo 1 was burnt to death in the command module.
You fear mongerer, are part of the problem.
Have you ever looked through the Forbes 400? "Old money" in the US is largely a myth.
The ten wealthiest individuals in America are Gates, Buffett, Paul Allen, Larry Ellison, Michael Dell, and the Walton heirs. (Steve Ballmer is 11th, incidentally.) Of these, only the Waltons inherited their money, and that not from some ancient rail baron, but from a self-made man who died in 1992.
All employees must wash hands before seeking equitable relief.
The presence or absence of a scholarly degree on the part of a theorist says absolutely nothing about the merits of a theory. Nor does the amount of money invested in the enterprise of realizing the theory. I learned that one from cold fusion.
Looks like th etower of babble is finnaly going up. I just hope a 6,000+ mile structure doesn't come down on anyone's house.
I wonder how efficient it would be to compact much of the garbage that is on earth and send it up the cable? Spend a little more money and build some robots that can assemble interlocking packages of garbage at the other end. It's a lot of mass we're not using right?
"...we're all still waiting for one of the many Carbon Nanotube research centers to announce they reached the famous 100GPa red line from page 10 of the NIAC Phase 2 Report..."
Why do I feel like I've missed an invitation to join a very, very exclusive club?
The www.highliftsystems.com website--which seems to be down now--is the one I frist read about the space elevator idea. I don't recall if it had numbers, but I recall it was pretty thorough in its plans and problems.
Other interesting problems they had worked out were the oscillation of the ribbon and effects of wind.
This is just a projection from years ago. Look at the graph and the dates, the year 2003 is halfway up the projection. The sample data being projected from in the beginning is tiny. Do we have any current real data? This is the same kind of garbage that infests ufo theory. (or supply side economics but that's a whole other flame war)
At the first lightning strike it will vaporize.
#1 We elevate a few hundred pounds of propellant and some rockets.
#2 We always have a matched elevator car going down at the same time one rises, on either side of this humongous ribbon.
#3 We have cars moving out from the geosync station at the same time as one rises from the ground.
And these are just pulled out of my ass, me a highschool dropout loser with a wageslave job. I'm sure the actual rocket scientists among us can come up with even better ideas how to manage this.
Besides, think for a fucking minute, brainiac. We're talking something *HUGE*. With potential energy I can't even begin to calculate... a 2 ton elevator car is gonna crash the whole thing down? It might lose a millimeter of altitude a month... plenty of time to fine-tune all of this.
I would register to vote if one of our presidential candidates promised to build the damn things.
In the movie The Core, 'Unobtanium' was the magical material used for the shell of the ship.
Basically, as temperature and pressure increased, two things happened: the durability and strength of the material increased, and also the material started generating electricity.
If it loses millimeters of altitude over a long period of time, surely they could use the same laser to propel the climber to sustain the station's orbit, at no real consequence?
Secondly, doing a few financials on this thing you can see there is a good reason to spend the money in other ways to lower low-earth orbit costs:
Let's say you, through some kind of miracle of government subsidy or making space as sexy to billionares as philanthropy to Africa, manage to get $10 billion at only 12% interest for this high risk project. Further lets say the miracle is so wonderful that you don't actually have to pay any interest on any of that money for 10 years while you are getting the elevator operational. (I forgot to mention the miracle that lets you actually construct the whole thing at all since the article admits they can't with carbon nanotubes as currently engineered.) Finally, lets say you miraculously only have to pay the interest on the principle once the whole thing is running. OK, so we're looking at a mere $100 million per month interest payments.
Are there any other lower risk ways of spending $10 billion that yield 12% interest? Lots, of course, but since we're being miraculous here we can assume we can grab the $10 billion and put it in one of those 12% yield bonds or mutual funds or whatever and have $100 million per month without spending the principle.
So what do you do with $100 million per month to, over the course of 10 years, get a system in place that can reach low earth orbit for $100/lb?
Lots of things, not the least of which is just guarantee a market for for launch services of $100 million per month for the next 10 years for any mass launched into orbit that doesn't end up as orbital debris. You pay only by the pound and you divide up the money evenly, each month, between all mass launched from earth to orbit that month.
The result is a "race to the bottom" in terms of cost/lb to earth orbit.
Where does it limit out?
Fuel costs aren't the limiting factor.
How about the vehicles?
Well, the vehicles don't have to be all that expensive really. Control electronics? Naw. Tankage? Take for example the mass production of Coke bottles out of PET plastic. These are tough, light-weigh bottles capable of withstanding cryogenic temperatures. Do something in quantity and you can get the prices of pressure bottles way down. Engines? The guys who worked on the Atlas engines in General Dynamics told me they weren't really any more close-tolerance than the VW engines you put in your old '69 microbus. Again, volume is the key. Rocket science ain't rocket science. The key is industrial production and operational volumes.
So at the end of 10 years, what you have are a bunch of small companies doing the equivalent of a Latin American VW factories cranking out disposable rockets (the tankage, electronics and engine metal for which you can use on orbit anyway so your effective payload is quite a factor), launching a million pounds per month into orbit at $100/lb.
Seastead this.
What effect do you think improvements in small run manufacturing might have here? Do you think some small run designs might emerge that jump start this process?
CRAP CRAP CRAP!!!
I apologize; geosync is about 36,000 kilometers, not miles.
That translates to about 22,000 miles.
I'm sorry that I got metric and "standard" confused.
(Perhaps I should get a job at NASA.)
I don't know why, but I thought that geosync was much higher.
You were right; sorry about my earlier post that a geosync-sized cable would wrap around the Earth at least once.
It wouldn't.
However, the total cable, including the counterweight portion, would wrap around the Earth if it weren't for friction.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Getting {people, equipment, etc} into space becomes a lot easier when you only have to lift them partway. Then they get thrown the rest of the way, really, really fast, with no work on your part. By controlling when you start the ride, you determine when you get flung off the end, and thus where you're going to be at the end of the arc.
You cannot apply a technological solution to a sociological problem. (Edwards' Law)
> Perhaps you've heard of centrifugal force? I heard that it doesn't really exist. Perhaps you've heard of centripetal force?
Perhaps I've got a degree in Physics?
Whether a force is "fictional" or "real" all depends on your frame of reference. In this context, the distinction hardly matters and would be a digression.
Instead of using a laser to beam power up to the top, why not have a nuclear reactor up there instead?
Nuclear reactors in space are needed and are already being researched by the NASA Prometheus initiative. Conversely, beaming at the power required is a technology not even in its infancy. Using a nuclear reactor at the end of the elevator would provide enormous power, would be more cost effective, and would reduce the number of technological unknowns required to make a working space elevator.
This is my sig.
Don't blame Kim Stanley Robinson for the faults of his readers.
Finally! A year of moderation! Ready for 2019?
The limiting factor of launch service creation isn't small-run manufacuring but market incentive. The number of under-employed technologists that would be willing to sacrifice everything in their lives but the chance to build cheaper launch systems is so great that you just aren't going to get that much of a gain from small run manufacturing technologies. The problem is if they sacrifice everything and then can't even get the tools, or can't get the food and shelter long enough to use the tools -- then they are no better off than if they were working for the boss they always worked for -- except to the extent they might be better off dead.
Seastead this.
For a good book on the effects of a Space Elevator, read "Red Mars" published around 1992. There is quite a bit in there that, of course, pertains only to a Space Elevator being used in a lower gravity environment than earth. Kim Stanley Robinson put a lot of good explanations of everything in that book, which seems to still hold true after a 1996 Mars Sojourner landing and this year's twin landings.
"Beware of he who would deny you access to information, for in his heart, he dreams himself your master."
Always me with the stupid question, but how do you install a nanotube cable in space? This seems much more difficult than the installation of the Transatlantic Cable, and that didn't work the first time. They never addressed this technological issue in the article. I mean, do you rocket a spool of cable to a geosynchronous orbit and let it out in opposite directions, one towards Earth and the other away? As the spool satellite gets lighter, it's going to have to fly lower...it's just complicated!
-=- Many seek good nights and lose good days.
I think I'd stay at or below the midpoint. Below the midpoint of the cable, you could fall to earth in your space capsule ( you DID bring a space capsule didn't you?? ) Past the midpoint, you would fly off into space I think ( would you fly off into space or just orbit forever? My vote is fly off into space... ). And that would suck....
Eat at Joe's.
The idea of "meek" meaning the above came from a lecture from one of my theological profs.
Among my prof's sources is the Theological Dictionary of the New Testament, vol. 6. I'll be double-checking that book soon, since our library has it. As one of the replies to my slashdot post noted, the Greek word was "praus" (pra-oos). Commonly in Greek literature, my prof has told me, this word was an adjective meaning "ready for service," or "awaiting command." He told me about a pair of instances in Greek literature. In one occurrence of the word, a character was looking upon a warship which was decked out with all of its equipment and lacked only a Captain. In the other instance, "praus" was used to describe an armored horse, fitted for battle, and needed only its rider.
So, according to these usages, and the Theological Dictionary of the New Testament, when Christ said Blessed are the "praus," he was probably referring to those who keep themselves spiritually prepared.
--