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The Ribbon to Space

I think it's quite a bit far-fetched. Coordinating the stationary orbit of a satellite to lower the ribbon alone is hard enough, but out of curiosity, I did some calculations.

I cut a 2"x 3" piece of ribbon and weighed it: 1 g

2 in x 3 in = 6 in^2

1 g = 0.0022 lb

(0.0022lb / 3 in) * (5280 in / mi) * 60000 mi * (1 ton / 2000 lb) =

116 tons of ribbon

116/6 = 19 tons/in^2

That would have to be one damn strong ribbon to withstand 19 tons of force per square inch!
 
Bruce said:
That would have to be one damn strong ribbon to withstand 19 tons of force per square inch!
Click to expand...

Yes it would but.....
34506main_super_s1.jpg
 
Bet I could catch one hell of a fish with that stuff....
 
Bruce said:
116/6 = 19 tons/in^2

That would have to be one damn strong ribbon to withstand 19 tons of force per square inch!
Click to expand...

Which is 3 tons of force per square centimeter, or ~27,000 Newtons or .27 GPa.
 
Xeriar said:
Which is 3 tons of force per square centimeter, or ~27,000 Newtons or .27 GPa.
Click to expand...

What if it ...broke? (terrorism, industrial accident, faulty engineering, errant airplane, Murphy)

Doesn't look pretty.

No sir, I don't like it.
 
Rob Lister said:
What if it ...broke? (terrorism, industrial accident, faulty engineering, errant airplane, Murphy)

Doesn't look pretty.

No sir, I don't like it.
Click to expand...

The ribbon flies off into space, and the remaining length floats gently down to Earth.
 
Arthur Clarke wrote a novel based on the "space elevator" concept some time ago. Tis' an interesting idea if the technology can be developed.
 
Funny how everyone seems to think hanging a ribbon from a satellite is a static condition. No one appears to take into account aerodynamic and meteoroligical effects on the hanging ribbon. You know, little things like the jet stream? You've got variable forces acting on the ribbon, which will have an ongoing, gradual influence on the orbiting platform, which will have to be countered over the long run.

Carbon anotubes? Sounds to me like they would be electrically conductive to some degree. Anyone considered the possibility of lightning strikes on your ribbon? Even if it turned out that carbon nanotubes are a poor conductor, at the level of the potentials involved, even a poor conductor becomes a significant risk. I wonder what the potential difference would be from one end of the ribbon to the other? Especially when you go from a moist air atmosphere to a nice, insulating vacuum or fairly thin gasses being bombarded with various forms of radiation and becoming ionized. If nothing else, it would be interesting to see what happens when you run a conductive line from ground to space. You might get some neat auroral effects.

I think conditions on the orbiting end would be hell. Imagine being jerked around as different forces played with the ribbon. You might find your head banging the ceiling as the jet stream made a slight meander that crossed the ribbon. Think "marble in a bucket." Oh, sure, you could build in some sort of propulsion system to stabilize the platform, but we're talking a lot of force that would be needed to counteract the twangings of a 19-ton ribbon. How much reactive mass would have to be expended, and what would it do to the system's so-called economy if you had to keep sending up replacement fuel to replenish what you've used?

Nice idea, though I suspect reality has a few bites for this scheme.

Regards;
Beanbag
 
There's no 'station' hooked to the end, it's just a 100,000 km long ribbon. Yes, nanotubes are pretty good conductors - it's helpful, even.

I don't think 'lightning bolt' is quite the term, this thing is a direct route to ground from above the atmosphere. I'll wager there will be a fairly continous stream of current into it from that mere fact alone.
 
As I read it, the space end of the ribbon is tied to a geostationary satellite, and that's it. What people seem to be overlooking is the fact that our geostationary satellite is free floating, and even the slightest tug on our nanotube ribbon will send it careening out of position. Someone tried to tell me that once the ribbon is anchored, centripetal force will hold the satellite in position and keep the ribbon "taut"; however, I still fail to see how the ribbon will be completely unaffected by winds aloft.
 
SkepticJ said:
Yes it would but.....
34506main_super_s1.jpg
Click to expand...

... for single, perfect nanotubes. There was a new world record set for nanotube length last year: 2 mm.

Once you factor in the lattice faults (and in a 36,000 km long crystal, they are thermodynamically inevitable), nanotubes are no stronger than carbon fibre, because that's essentially what they are, just a neat configuration of it.

Edit to add: coolest thing from that article:
By altering the gas flow direction, researchers were also able to make cross connected nanotube grids that may be able to be used as nanosized circuits.
Click to expand...

Also edit to add: who needs stainless steel, when you can do cool things with bainite? 2.5 GPa yield stress and plastic failure in a dirty steel.
 
The ribbon/space elevator is not just tied to a geostationary sattelite. A counterweight is extending upwards, presumably holding the whole thing in equilibrium. I haven't seen any theorethicans tear the basic theory to schreds, so I assume the math is solid enough.

Plenty of other problems, obviously. A totally new material technology is needed, but that is a sort of barrier we have overcome many times before.

Hans
 
MRC_Hans said:
The ribbon/space elevator is not just tied to a geostationary sattelite. A counterweight is extending upwards, presumably holding the whole thing in equilibrium. I haven't seen any theorethicans tear the basic theory to schreds, so I assume the math is solid enough.
Click to expand...

Yeah - the centre of mass has to be geostationary. This is also the point where the forces are greatest.

Originally posted by Xeriar
The ribbon flies off into space, and the remaining length floats gently down to Earth.
Click to expand...

Ideally most of it burns up in the atmosphere on re-entry.

I would be interested in knowing what standing waves might be set up, though...
 
Originally posted by Bruce
I think it's quite a bit far-fetched. Coordinating the stationary orbit of a satellite to lower the ribbon alone is hard enough, but out of curiosity, I did some calculations.

I cut a 2"x 3" piece of ribbon and weighed it: 1 g

2 in x 3 in = 6 in^2

1 g = 0.0022 lb

(0.0022lb / 3 in) * (5280 in / mi) * 60000 mi * (1 ton / 2000 lb) =

116 tons of ribbon

116/6 = 19 tons/in^2

That would have to be one damn strong ribbon to withstand 19 tons of force per square inch!
Click to expand...
That's a mighty short mile you got there . . . :D

Plus, you shouldn't divide at the end by the area of your piece of ribbon (2 inches times 3 inches), but rather by its cross-sectional area (2 inches times the very small thickness of the ribbon).
 
I thought that was a mighty small tensile strength for the project. :-)

Redoing the math, I come up with around 260 GPa.

However, there is a good chance that the nanotube ribbon is going to be considerably lighter.
 
The structure extends as far above the geostationary orbit as below. Then you build another two 120 degrees apart.

Then you...


Nice idea, but I'm not holding my breath. Clarke's "The Fountains of Paradise" is a good yarn though.

What I find worrying is how as soon as anyone proposes an ambitious structure these days, someone immediately pops up with the terrorism question. Yes, a terrorist can put a car in front of a 200mph train. He can drop rocks off a freeway bridge. He can poison water supplies. Should we therefore do without such things?

Let's not let the cavemen win, people.
 
Soapy Sam said:
What I find worrying is how as soon as anyone proposes an ambitious structure these days, someone immediately pops up with the terrorism question. Yes, a terrorist can put a car in front of a 200mph train. He can drop rocks off a freeway bridge. He can poison water supplies. Should we therefore do without such things?
Click to expand...

Be pretty silly for terrorists to blow a space elevator up... not when they could use it to drop rocks from orbit.
 
Matabiri said:
Once you factor in the lattice faults (and in a 36,000 km long crystal, they are thermodynamically inevitable), nanotubes are no stronger than carbon fibre, because that's essentially what they are, just a neat configuration of it.
Click to expand...

Well, we might not even attempt to make a space elevator until nanites are made that will build it without the carbon lattice flaws.
You are correct, they aren't any stronger than carbon can be because that's what they are. What they are though is a molecule of nothing but sp2 bonds which are stronger than diamond's sp3s. I think the graph I posted is incorrect also; didn't notice it until I had posted it. I think it has their strength at about 1/3 of what it really is.
 
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