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Artificial superstrong silkworm silk surpasses natural spider silks

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Re: Artificial superstrong silkworm silk surpasses natural spider silks

#51

Post by dekhn »

ncmncm wrote: post #44

2 GPa is 2GN/m^2, or 200kN/cm^2, which supports 20Mg. Taking silk density as 1 g/cm^3, that is 20M cm, or 200,000 m, or 20km. Silk density is actually ~1.37 g/cm^3, so derate the above to 14.6 km. IOW, a silk cable can support 14.6 km of rope hanging below it. Not close to strong enough for a Space Elevator.

That's still only the very first step to building a Space Elevator. And, the product, if it had those properties (when deployed in the wild) would find more profitable use in terrestrial applications.

We will be burning rocket fuel to get to space for the foreseeable future. Better to launch enough to build in-space processing facilities if you're really committed to dual-homing humanity or making space travel more cost effective.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#52

Post by rmah »

anu7df wrote: post #4

Tensile strength of 2 GPa for this silk compared to 0.4 to 0.8 GPa for steel. Really cool.. This is without including the strength to weight aspect!

What makes steel awesome is that the properties can be tuned across a wide range.

Sure, cheap structural steel has a tensile strength of about 0.4 to 0.5 GPa and the most common types (i.e. cheapest) of "high strength" steel can reach 0.8 GPa.

But... some specialty steels can reach well over 2+ GPa. The steel for some cables have tensile strengths of 2.0 GPa, maraging steel for can reach 2.7 GPa.

There's a good reason steel is still so widely used. It's awesome!

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#53

Post by tb_technical »

ncmncm wrote: post #44

2 GPa is 2GN/m^2, or 200kN/cm^2, which supports 20Mg. Taking silk density as 1 g/cm^3, that is 20M cm, or 200,000 m, or 20km. Silk density is actually ~1.37 g/cm^3, so derate the above to 14.6 km. IOW, a silk cable can support 14.6 km of rope hanging below it. Not close to strong enough for a Space Elevator.

Space elevators are lame. Launchloops and orbital rings are where it's at! :D

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#54

Post by Maursault »

ncmncm wrote: post #44

2 GPa is 2GN/m^2, or 200kN/cm^2, which supports 20Mg. Taking silk density as 1 g/cm^3, that is 20M cm, or 200,000 m, or 20km. Silk density is actually ~1.37 g/cm^3, so derate the above to 14.6 km. IOW, a silk cable can support 14.6 km of rope hanging below it. Not close to strong enough for a Space Elevator.

> Not close to strong enough for a Space Elevator.

I thought space elevators were deployed with space tethers, which are held taut by the planet's rotation and centrifugal force. While mutant silk worm silk still may not be strong enough for a space elevator, it shouldn't depend on the weight of the rope hanging below it but instead the on the centrifugal force pulling in the opposite direction, away from the planet's surface.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#55

Post by ncmncm »

tb_technical wrote: post #53
ncmncm wrote: post #44

2 GPa is 2GN/m^2, or 200kN/cm^2, which supports 20Mg. Taking silk density as 1 g/cm^3, that is 20M cm, or 200,000 m, or 20km. Silk density is actually ~1.37 g/cm^3, so derate the above to 14.6 km. IOW, a silk cable can support 14.6 km of rope hanging below it. Not close to strong enough for a Space Elevator.

Space elevators are lame. Launchloops and orbital rings are where it's at! :D

Orbital rings like circular skyhooks that are much easier to schedule pickup on, and have much friendlier structural stress characteristics, seem not to be written about as much as they ought to be.

If by orbital ring you mean a band girdling the planet and rotating well above orbital speed, magnetically coupled to and supporting stationary structures that reach ground level... I don't see any value in discussing those in this century.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#56

Post by ncmncm »

Maursault wrote: post #54
ncmncm wrote: post #44

2 GPa is 2GN/m^2, or 200kN/cm^2, which supports 20Mg. Taking silk density as 1 g/cm^3, that is 20M cm, or 200,000 m, or 20km. Silk density is actually ~1.37 g/cm^3, so derate the above to 14.6 km. IOW, a silk cable can support 14.6 km of rope hanging below it. Not close to strong enough for a Space Elevator.

> Not close to strong enough for a Space Elevator. I thought space elevators were deployed with space tethers, which are held taut by the planet's rotation and centrifugal force. While mutant silk worm silk still may not be strong enough for a space elevator, it shouldn't depend on the weight of the rope hanging below it but instead the on the centrifugal force pulling in the opposite direction, away from the planet'…

Space elevators depend utterly on extreme material strength to be possible at all, and on centrifugal force only to stay taut.

They could be practical with known materials on Mars, but there is nothing there worth building one for.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#57

Post by ChrisMarshallNY »

obsrvatlarge wrote: post #39
ChrisMarshallNY wrote: post #30

Earlier quoted context omitted.

I’ve read an article (maybe linked here?), about the reason that building elevators have limits to how many floors they can travel. It has to do with the weight of the cables. That article posited that spider silk was a solution, but this may be better.

Might have a problem with fire resistance.

Most materials (including steel) have issues with extreme heat. Steel can suffer “invisible” damage, where it becomes structurally weak, but there’s little visual evidence.

In that case, a cable that visibly melts or breaks, can be better.

Elevators have all kinds of passive braking systems. They might get stuck, but they only fall in movies.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#58

Post by Maursault »

ncmncm wrote: post #56
Maursault wrote: post #54

Earlier quoted context omitted.

> Not close to strong enough for a Space Elevator. I thought space elevators were deployed with space tethers, which are held taut by the planet's rotation and centrifugal force. While mutant silk worm silk still may not be strong enough for a space elevator, it shouldn't depend on the weight of the rope hanging below it but instead the on the centrifugal force pulling in the opposite direction, away from the planet'…

Space elevators depend utterly on extreme material strength to be possible at all, and on centrifugal force only to stay taut. They could be practical with known materials on Mars, but there is nothing there worth building one for.

You are sidestepping the fact that in your OP you demonstrated and argued that the silk could not be used for space elevators because it could not support its weight beyond 14.6km, but I argued it would not need to since that weight will be countered by centrifugal force, so whether the silk can be used for a space elevator has nothing whatsoever to do with supporting its own weight, rather, it must support the centrifugal force.

If the silk only need be kept "only" taut, its weight will be perfectly balanced against centrifugal force, so in effect the silk will be weightless. But my suspicion is the tether would necessarily need to be kept taut with extra force, not "only" taught, but with force to put stress on the silk tether pointing outwards and upwards.

I have no idea how one would calculate the required centrifugal force, but perhaps you'll do us all the favor and determine whether or not the silk would be strong enough without being distracted by the weight of all the silk, which is irrelevant due to it being cancelled by centrifugal force.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#59

Post by ncmncm »

Maursault wrote: post #58
ncmncm wrote: post #56

Earlier quoted context omitted.

Space elevators depend utterly on extreme material strength to be possible at all, and on centrifugal force only to stay taut. They could be practical with known materials on Mars, but there is nothing there worth building one for.

You are sidestepping the fact that in your OP you demonstrated and argued that the silk could not be used for space elevators because it could not support its weight beyond 14.6km, but I argued it would not need to since that weight will be countered by centrifugal force, so whether the silk can be used for a space elevator has nothing whatsoever to do with supporting its own weight, rather, it must support the centr…

The correct figure, as noted elsewhere, is 146 km.

But literally the only thing holding up almost all of the span from geosynchronous orbit down to the ground is the pure strength of the cable. Centrifugal force would act usefully mainly on parts of the cable that extend out past geosynchronous orbit, to support the whole structure through tension in the cable. The cable inside that orbit would absolutely not be weightless. Its weight per unit mass is of course lower close to geosynchronous orbit, but most of the cable is very far from it.

Re: Artificial superstrong silkworm silk surpasses natural spider silks

#60

Post by Maursault »

ncmncm wrote: post #59
Maursault wrote: post #58

Earlier quoted context omitted.

You are sidestepping the fact that in your OP you demonstrated and argued that the silk could not be used for space elevators because it could not support its weight beyond 14.6km, but I argued it would not need to since that weight will be countered by centrifugal force, so whether the silk can be used for a space elevator has nothing whatsoever to do with supporting its own weight, rather, it must support the centr…

The correct figure, as noted elsewhere, is 146 km. But literally the only thing holding up almost all of the span from geosynchronous orbit down to the ground is the pure strength of the cable. Centrifugal force would act usefully mainly on parts of the cable that extend out past geosynchronous orbit, to support the whole structure through tension in the cable. The cable inside that orbit would absolutely not be weig…

Effectively weightless. The weight of any part of the tether must be entirely counteracted by centrifugal force, otherwise the weight of the tether would pull everything to the ground.
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