[ot] Mars colonization

[Storminator]

The impact of a two inch meteor doesn't come anywhere near the force of 20 tons of cable slamming into the Earth's atmosphere at a tremendous velocity [edit: make that "tremendous velocity" 7km/s]. The friction by itself would disintegrate the cable. Once it started to come unwound, the actual fibers themselves are about the thickness of a hair.

Real world example: a two inch meteor would punch a hole in the space shuttle. On the other hand, the space shuttle hitting the Earth's atmosphere at too flat of a trajectory would cause it to completely disintegrate. The cable will weigh only 20 tons. The dry weight of a space shuttle is 90 tons, and I can assure that little would survive to hit the ground.

Of course, this is a mythical cable someone is dreaming up. As I said, I haven't bought into what that site is selling. I seriously doubt the 20 tons estimate (it works out to a pound and a half of material per mile).

And we've seen big hunks of debris hit the ground before. The cable wouldn't necessarily hit the atmosphere hard, it's already piercing thru it. The possibility of the cable snaking back along itself and laying down at a mere 1 km/s is very real.

I'm not saying it can't be done, I'm just saying it isn't easy.

PS

 

[Lurks-no-More]

Re: Terrorism

With the current proliferation of WoMD more and more groups will have access to ballistic missles or something else to attack the elevator. In 1945, one country had nuclear missles, these days a third-rate country like North Korea is almost there. In 2050 a country as small as Jamaica could conceivably have them (ok, that's a stretch).

tleilaxu imagines the "Rasta Bomb"

Actually, that proliferation is one of the biggest reasons I think we must get people off this planet, QUICK!

Sooner or later some idiot is going to use bioweapons (chemical and nuclear weapons can kill millions, if you use them against a big city; a tailor-made smallpox could kill a billion people or more...).

Independent, self-contained, human habitats, all over the asteroid belt, dug deep beneath the surface of Moon, on Mars, all over Earth's orbit and LaGrange points...

Individually more fragile, perhaps, but you can't get them all. At the moment, we have all of our eggs in a single big basket.

 

[Larry Fitz]

We are the only species on this planet with the capability to engineer our own survival beyond the end of the planet itself. The eventual survival of our species will depend on leaving Earth and in fact the Solar System entirely. Extra-terrestial colonization is not a matter of "if" but "when". The sooner the better in my opinion.

 

[tleilaxu]

We are the only species on this planet with the capability to engineer our own survival beyond the end of the planet itself. The eventual survival of our species will depend on leaving Earth and in fact the Solar System entirely. Extra-terrestial colonization is not a matter of "if" but "when". The sooner the better in my opinion.

Actually, when you think about it monkeys and dogs were in space before homo sapien sapiens. I gues they've come up with the ultimate survival instinct: make friends with the hairless monkeys.

 

[Wil]

Of course, this is a mythical cable someone is dreaming up. As I said, I haven't bought into what that site is selling. I seriously doubt the 20 tons estimate (it works out to a pound and a half of material per mile).

And we've seen big hunks of debris hit the ground before. The cable wouldn't necessarily hit the atmosphere hard, it's already piercing thru it. The possibility of the cable snaking back along itself and laying down at a mere 1 km/s is very real.

I'm not saying it can't be done, I'm just saying it isn't easy.

PS

I wouldn't call it mythical material...there's a lot of research gone into it. They know exactly what it's going to be made of, and that material is currently being produced in smaller scale. The projected weight of the cable is 7kg/km. That's not a lot of mass. If it were to be severed from the station end, it wouldn't fall straight down - there's the rotation of the earth and the sudden release of the upper anchor point that would cause it to wrap almost vertically. When it hits the atmosphere, it disintegrates as it falls. If the cable were to snake back along itself at a low relative velocity, it would simply plunge into the ocean with little or no effect.

Edit: Not to mention the possibility of integrating a self-destruct system that breaks the cable into small chunks should it be severed. Either a beamed signal to explosives woven into the cable, or have them triggered when a signal running through the cable is lost (probably a fiber optic line).

I'm not sure if you're thinking of some tens of meters-wide cable here (which is what earlier science fiction envisioned). This thing is a meter wide in orbit and just microns thick. With as much research that has gone into the possible impact of the cable, I think they pretty much have that angle covered. Yes, there are risks - but the risks are more than worth the return.

 

[Umbran]

The friction by itself would disintegrate the cable. Once it started to come unwound, the actual fibers themselves are about the thickness of a hair.

And perhaps we need to consider that more fully. The friction heating is a matter of aerodynamics. The aerodynamics of a straight, long, light cable are not those of a short, dense, space shuttle. Unless you've rolled the cable up into one 20-ton ball, it's nothing at all like the shuttle. So, you shouldn't be getting the effects on the cable by looking at what would happen to the shuttle.

That's not to say the stuff is safe or unsafe. SImply that it's going to behave unlike what we're used to considering.

Anyone ever read Larry Niven's Ringworld? It contains a scenario which is interestingly similar...

 

[Fast Learner]

Anyone ever read Larry Niven's Ringworld? It contains a scenario which is interestingly similar...

Ringworld is precisely why I suggested a cable woven from millions of nanotubes rather than just a few. That molecule-thick wire can be a real problem.

 

[Storminator]

I wouldn't call it mythical material...there's a lot of research gone into it. They know exactly what it's going to be made of, and that material is currently being produced in smaller scale. The projected weight of the cable is 7kg/km. That's not a lot of mass. If it were to be severed from the station end, it wouldn't fall straight down - there's the rotation of the earth and the sudden release of the upper anchor point that would cause it to wrap almost vertically. When it hits the atmosphere, it disintegrates as it falls. If the cable were to snake back along itself at a low relative velocity, it would simply plunge into the ocean with little or no effect.

Edit: Not to mention the possibility of integrating a self-destruct system that breaks the cable into small chunks should it be severed. Either a beamed signal to explosives woven into the cable, or have them triggered when a signal running through the cable is lost (probably a fiber optic line).

I'm not sure if you're thinking of some tens of meters-wide cable here (which is what earlier science fiction envisioned). This thing is a meter wide in orbit and just microns thick. With as much research that has gone into the possible impact of the cable, I think they pretty much have that angle covered. Yes, there are risks - but the risks are more than worth the return.

I thoroughly read the website, as I mentioned above. I still think this cable is mythical. Did you read the part about it being 60,000miles long? I don't think a cable a meter wide and a hair thick is going to work. There are a LOT of big ifs that need to be answered before I believe that design is proven. My guess is that the cable will be much wider and thicker, and it'll be in shorter lengths attached together somehow.

I've got a pretty fair handle on the dynamics of objects falling from space (check my profile). There's a lot of room between hitting the atmosphere at right angles and sliding straight down into the anchor point (and I'm not sold on their anchor point either). Somewhere between those extremes is what's really going to happen, and there's a lot a potential for surviving pieces in that space. If they can really build a cable that'll work and only be a meter wide, it probably will burn up if it reenters. But I think it'll require a lot more cable that that, and I think the cable that *does* get built will survive.

There are a lot of problems with that site's projections. You aren't going to convince me of anything if you keep using their site as a reference.

I am sold on explosive safety devices, tho.

PS

 

[RSKennan]

Has anyone mentioned the possibility of getting the Military and private corporations to help us get into space on a lasting basis? It's been mentioned that the miltiary has a huge chunk of the US govenrment's tax pie, and that's not likely to change (regardless of how I or others feel about it). If the military can see the benefits of getting us into space, It will happen. Similarly, private corporations are looking into the possbilities as we speak. The ten million dollar prize is probably going to be won fairly soon. I think it will start to happen soon.

 

[s/LaSH]

I'll just chip in with some random thoughts again...

The idea of a carbon nanofibrous cable is an interesting one. The current technology provides materials that are multiples better than spiderweb, which is multiples better than steel... or so the professors told me at TECH101. To memory, the only place they can currently make them is on carbon electrodes, and they're only nanometers long... so far.

I wonder... so long as you're using carbon nano technology, it might be possible to use this cable as some form of generator. I say this because, back in the 1970s, scientists from Japan and New Zealand discovered how to make organic polymers that conduct electricity (they got the Nobel two or three years ago). If you could use said cable to sweep through a magnetic field (say from the sun?) you could theoretically get some good power generation. I think. I'm not a physicist.

But it does convey benefits... if you could pull it off, that would be my tack on tricking big business into space. ("Well, so long as the generator cable's there, why not rent it out to launch agencies?")