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."

Comments

Doubtfull

[Smitedogg]

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.

Dogg

Re:Doubtfull

[houstonbofh]

There will be funding just as soon as it looks like someone else could make it. No one will want to be the president who "Lost space to the Chinese." Embarrassment is a powerful motivator.

Re:Doubtfull

[Jerf]

If exponential growth predictions hold true, and the "first entity" locked out others from use, then the "first entity" would be a "winner" simply due to taking off too rapidly for others to feasibly catch up. That doesn't make the other entities "losers", except in relative terms; they may always be four years behind but that four years may represent a factor of, oh, as long as we're being fanciful let's say 50.

However, I think there's a majorly false claim in there, which is that the first owner will lock out everyone else. Obviously, the first order of business when you have a space elevator is to put up more of them, and for a while they may indeed have a monopoly. But given the resources still available on Earth, someone will eventually tender an offer for a fully-completed cable that the first entity can't refuse; no matter how valuable the cable, it is possible to pay the owner off today with $X dollars, which the first entity will (correctly) perceive is more valuable to have it in liquid form, available to then invest back into other things. That price may be sky-high, pun semi-intended, but there are people on Earth who will be able to afford it.

By buying a completed cable, they can jump-start themselves up, and as more and more entities do this, it'll start looking more even. While the first mover will have a true advantage that may last a very long time, I don't see a situation where they maintain a 20x advantage over everybody in perpetuity; the value proposition of liquidating one of the cables is just too appealing.

This assumes a capitalistic owner of the first tether, and if the US gets there, the world can for once be glad that we see everything in terms of dollars, sooner or later, because that means that we will indeed have our price (though in the truest capitalistic tradition, it will be all the traffic can bear!). If it's not the US, well, it depends on who gets there first, but even so, it would take a very strong government to turn down the offers it would get... some of which are quite likely to be of the "offer you can't refuse" variety. ("Dear China: We still have nukes. Sincerely, All Nuclear-Capable Countries.") I still can't imagine a plausible long-term scenario where somebody maintains a massive, multiplicitave lead indefinately, though again, serious short- and medium-term advantage do accrue to them. (If nothing else, they'll need to draw on international capital to invest in space itself.)

What does human advancement require?

[ObviousGuy]

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.

Re:What does human advancement require?

[1u3hr]

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

I'm sure that more is spent on any one of: cosmetics, fizzy drinks, cigarettes, SUVs, cocaine. If you're just talking about govt expenditure; at least 100 times as much is spent on the military.

If access to space is much cheaper, the benefits to the world will be immense; though it'll take a few decades. Even back in the 70s when O'Neill advocated space colonies in the L5 orbits it was possible to make a case. With a much cheaper launch method it becomes compelling.

Cable propagation lessons from the launch loop

[klic]

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