Artificial superstrong silkworm silk surpasses natural spider silks
cell.com
cell.com
This contrasts from biotech based fibers, e.g. https://boltthreads.com/technology/microsilk/ , which is produced by genetically modified yeast.
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!
For it to be competitive, it would be necessary for the rate of hydrolysis of the protein fibers (which breaks the fibers) in an alkaline environment to be less than the rate at which rusting diminishes the strength of steel bars.
This is very unlikely. At most there might be a chance for such fibers to be used for reinforcing some other kind of cement, less alkaline than the common cements.
Also, for reinforcement applications, good adhesion between the reinforcing material and the reinforced material is necessary, which for silk vs. a mineral cement would need some kind of extra adhesive coating of the fibers, with adequate properties, which might be hard to discover.
How does it compare to something like Dyneema?
https://matweb.com/search/datasheet.aspx?matguid=4481722d60e...
They just need to breed friendly docile spiders.
https://www.getsurrey.co.uk/news/uk-world-news/royal-hollowa...
>Has a Royal Holloway researcher discovered the world's friendliest spider?
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.
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.
They could be practical with known materials on Mars, but there is nothing there worth building one for.
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.
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.
No. That is ridiculous and wrong.
The cable is not holding up its own weight, the centrifugal force is. The tension comes from the anchor point and the centrifugal force only. Weight is entirely counteracted and is no longer a consideration.
Think of a rotating chain in space, the chain is weightless, but each ring needs to apply enough centripetal force to counter the centripetal force.
Lets focus on the barycenter of the chain.
The centripetal force is limited by the strength of the chain; the centrifugal force is a function of rotation speed, length of the chain, and linear density of the chain.
this means that for any combination of chain type and rotation speed if the chain gets too long it will break.
With a geostationary space elevator you need to build a part of it over geostationary orbit and a part of it below geostationary orbit. the part above will pull the part below and make it "float".
The problem is that the part below needs to be ~100 km long and has still has a weight.
Think of the section of the tether at geostationary orbit as a giant weightless chain link.
The issue is not having that chain link remain suspended, the problem is to have it not break while trying to balance the huge forces.
And in order for a space tether to work at all, that weight must be negated by centrifugal force or the entire thing will collapse to the ground.
all the ~100km of tether below geostationary orbit will have positive net weight by definition. All this weight must be held by tensile strength, whether it comes from a fleet of rockets or centrifugal force is irrelevant.
Again the hard thing is not making it float, geostationary satellites do this already, the hard thing is building a 100km long satellite.
EDIT: said another way consider a chain being pulled apart by two tractors. All forces on the chain cancel each other yet some chains will break and some will not.
Forces are first applied, then propagated, then (vectorially) summed. If the material cannot handle the forces applied it will break.
If you happen to have seen those "Hydraulic press against X" videos you can see how it is not enough to have forces cancel each other in different points.
And to be clear about how this is relevant: for (at least) the first 50km or so the centrifugal force is negligible, so even if
weight + centripetal_force = 0
you have
|weight| + |centripetal_force| = fuckton of force
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.
(2 GPa) / (1400 kg/m^3 x 10 m/s^2) = (2e9 N/m^2)/(1.4e4 N/m^3) = (2e5/1.4) m = 140 000 m = 140 km
P = F/A, F = M x g, M = A x L x rho
L = M/(A x rho) = (F/g)/(A x rho) = (F/A)/(g x rho) = P / (g x rho)
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.
a) Space elevators (but the tensile strength required for that is too high and we are still not close enough), and
b) Large O'Neill cylinders, in the radius of about 50 kilometers (about 30 miles). With regards to tensile strength, these would require something with the strength of graphene.
This particular fiber seems to have 2 GPa of tensile strength, which is only good for a smallish O'Neill cylinder.
An O'Neill cylinder would consist of two counter-rotating cylinders. The cylinders would rotate in opposite directions to cancel any gyroscopic effects that would otherwise make it difficult to keep them aimed toward the Sun. Each would be 5 miles (8.0 km) in diameter and 20 miles (32 km) long, connected at each end by a rod via a bearing system. Their rotation would provide artificial gravity.
- Durable stringy clothing items
- Thinner ropes? Particularly relevant is for safety applications.
- Fiber ropes are particularly advantageous when compared to steel ropes in applications that require repeated bending.
I mean, you could in theory rappel from something like 2mm dyneema line with very comfortable safety margin on tensile strength alone, but 1. keeping a say 60m long 2mm line untangled is a serious headache, and I would not be comfortable holding my weight on the 2mm rope while letting it scratch against a rock wall .
And to be clear, I believe there are multiple applications for higher tensile strength fibers. I just can't see that many applications where thinner ropes than current technology produces would be a game changer.
* Buildings
* Bridges
* High voltage wires with very few supports
It has to do with the weight of the cables.
That article posited that spider silk was a solution, but this may be better.
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.