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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."
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.
DoggWhenever 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
Two different elevators guy. One on mars and another on earth. For lauching payloads from both planets. We are going to eventually have to travel home from mars....
there are no stupid questions, but there are a lot of inquisitive idiots
Bouyant cables, even in the best case, can't get you out of the atmosphere, so maybe 1000 km on the top side. The space cable has to reach geostationary orbit, some 35,785 km out. You lose :)
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)
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
Instead, the "meek" originally intended was a word to describe a ready and willing warrior.
Can you give me a reference for this? The OED has no mention of this inversion of meaning. The closest it gets is the primary obsolete meaning, "Gentle, courteous, kind. Of a social superior: merciful, compassionate, indulgent." (see http://dictionary.oed.com, subscription required).
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?)
First of all, I would imagine the $5B stated for the Space elevator includes at least some R&D costs. At $100 million, the nanotube composite rocket contains none - in reality, the cost will be much higher.
Furthermore, consider the cost of lifting each set of cargo - just like the space shuttle is extremely expensive, the fuel for a nanotube rocket is going to be much more expensive than that of a space elevator, which doesn't need fuel to come with.
So in reality you have: Space elevator: Maybe $5B, but pay it once and you've got the bulk out of the way.
Nanotube composite rocket: Billions to start out, >$.1B per rocket (my guess), and millions for each launch. Plus a lot more inspection and stuff.
Which turns the tables a good bit.
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.
It'll be at least a century before one of these things actually do anything useful.
What's sad is that it may well take that long.
However, the best thing we could do to promote the sky elevator is to develop and build nonotube-based structures here on Earth.
For example, if you were to rebuild the Golden-gate bridge in San Fransisco with nano-tube cables instead of steel cables, would they even be visible from the shore?
An impressive, previously infeasible structure, such as a bridge spanning the entrance to the Mediteranean, or across the English Channel would do much to get everybody used to the idea that something like this could, in fact, be done.
Also, projects like this would give us opportunities to answer questions about its durability, relability and safety in a large number of circumstances.
Building a space elevator with nanotubes as the first project is fundamentally stupid. Build something more reasonable first!
I have no problem with your religion until you decide it's reason to deprive others of the truth.
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're right, you would have to do some serious lateral acceleration to get to the top. Luckily, this is spread out over a 1-week climb so the specific impulse required is not too great.
But actually, the lateral acceleration at the top of the elevator is one of the main selling points. By the time you reach the top of the elevator, you've got enough angular momentum that you can just let go and be thrown to the Moon or Mars for free.
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.
I presented at the 2nd SE conference in Santa Fe last year, offering a different way of constructing it, but my comments apply to Dr Edwards' design too.
One of the best things about space elevators is that they are inherently much safer than any other method of reaching space. In fact once a couple of them are operating one can use the exponentially increasing payload capability to builds space elevators with any desired safety factor.
-- Andrew Price