Slashdot Mirror
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?
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??
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...
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."
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.
...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.
Unless it breaks, it can't tip over. It's like hanging a yoyo from your finger. There's no way the string is going to tip over onto your hand.
I'm not the least bit concerned about the carbon nanotubules. I'm still trying to figure out how their going to ATTACH the damn thing. All buildings are essentially resting upon the Earth. This thing can't rest, it needs to be attached. For a cable this long, a "stupid hurricane" could set up a vibration is going to build to the point where the whole thing starts "walking" across Columbia.
Don't blame me, I didn't vote for either of them!
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.
--
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
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
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.
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)
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
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").
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.
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.
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?
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.
Wouldn't that actually be four books?
Technically, yes. But in a shoot-off between the cheap Merlot I am currently drinking, and the cheap (and obvious) point you are making, YOU LOSE! (in a diplomatic sort of way, not meaning to put you down, you understand, but, like, the Merlot is getting me drunk, what are you doing to help my plight? Savvy?)
Tubal-Cain smokes the white owl.
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
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.
its not like we're talking about building it out of iron.
well - you asked about the wars. You might want to read James Jones works. Do a google search. I read from here to eternity when I was in grade 8 and it had quite an impact on me. If you read the books (best - do this first) then read books like the 20th century march of the dead it might give you some idea of what the war was like and why young men would be willing to throw away their lives.
Now to the rail guns.
Please consider the last shuttle disaster. Note that it took place at high elevation.
Clearly, a projectile launched at the surface must have more kinetic energy than the same projectile at the shuttle's location. Clearly at low elevation the effect of the atmosphere is many many times worse (follows an exponential in fact)
If the shuttle has a tough time protecting itself against re-entry then imagine the order of magnitude worse problem of gaining orbit from stored kinetic energy.
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Any system that is going to work has to feed energy into the launch craft on a more or less linear schedual. Given the ability to get a craft airborne using external energy feeds - then clearly we should be able to sustain the energy flow into the craft and there is a continous energy draw function and a continous energy drain function and a continuous drag/heat function and similar lift functions.
As a mathematician who has not tried to caclulate a window through these functions... my gut feeling says there is one and it is rather large.
So you can go to hyper velocities but you must choose a high elevation where you do this - where the air is rather thin.
Brute force blasting from the surface will gain a melted bullet. But - you might hide a nice little spacecraft in the wake..... agree?
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"
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...
"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?"
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
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.
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