TLDR; they reprocess natural silk from silkworms to produce silk fibers with better tensile strength. This is partly achieved by doing a better job of washing out non-strong compounds from the fiber, so the yield is strictly lower than that for natural silk. This process still involves boiling silkworms alive.
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!
My high school physics understanding of reinforced concrete is that the coefficients of expansion for steel and concrete are similar to a degree that it is very resilient to heat stress. I doubt that's the case for silk.
Also, steel, while more expensive than concrete, is still cheap compared to many other solutions for tensile strength. Also it tensile strength is sufficient for steel reinforced concrete. Concrete itself has performance limits for compression strength.
The problem for such an application is not the strength, but the chemical stability in time.
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.
These are of course, good points; cement probably being more porous than many people perceive. Just a little (hopefully interesting) speculation: adhesion might be less important, or entirely unnecessary if the reinforcing material isn't arranged like rebar. I.e. if it were just a tangle in the concrete.
Elastic stretching, the one that reverses completely on taking the load off, is the regime where there is a linear relationship between the stress load and the stretching. This should be seen as different from yielding which in mechanical testing is an irreversible change usually signifying a destructive change in the material. So, yes, silk stretches but is not damaged while doing so and the resistance it provides at the time relates to its strength.
Very interesting. Currently there are genetically modified silkworms that produce spider silk but it's not quite as good as the real thing. This method basically tries to "up" the silkwork silk to make it better. The metric they use is tensile strength. Curious to see applications.
I would imagine you could use ultra thin rope for heavy loads. I worked at a bungy jump place once and we had members of the Canadian military come to our bridge to test some very thin paracord. The rope they used did not look like it would be able to hold them but it did. But this silk is obviously way stronger then what they had I could only imagine how thin it would be and have the same strength
If transporting steel wiring is a major cost for you you could reduce that cost significantly by transporting far lighter, thinner strands of these fibers. That would have to assume that you can make up any increased costs of using the silk, of course.
> 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.
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.
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.
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.
"Counteracted" by force through tension in the cable. Which relies on the cable holding up its own weight. So, in no way "effectively weightless", unless you consider a regular bridge deck weightless because cables are holding it up.
> "Counteracted" by force through tension in the cable. Which relies on the cable holding up its own weight. So, in no way "effectively weightless", unless you consider a regular bridge deck weightless because cables are holding it up.
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.
the centrifugal force and the weight are applied in different points.
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
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.
Not enough for a space elevator on Earth, but definitely in the range you need for very long suspension bridges -- think in terms of railway bridges over the English Channel, the Straits of Gibraltar, the Irish Sea, and (with causeways/island hopping) the Bering Straits.
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.
IMO, fibers with very high tensile strength have only two applications worth speaking of:
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.
Save others the burden of a couple of clicks / taps.
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.
Regarding ropes, for most practical applications I can think fro the top of my head, tensile strength is not actually that much of a limiting factor (especially with dyneema), but more the abrasion resistance and how easy it is to handle a rope.
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 .
Depends on the use case, Zylon is one of the strongest fibers, and is used for rigging in competitive sailing. However it's not UV stable and not good with repetitive bending, so I'd not recommend it for climbing use either...
Yes, but we are there already in many applications where we need to pad the core for abrasion and handling. Making the core even more smaller makes no big benefit - unless it is substantially cheaper than the competition.
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.
Kevlar has a higher tensile strength than this silk, and there seem to be quite a few uses worth speaking of, apart from science fiction space technology...
Since it is still a protein based biopolymer, it is going to naturally decompose. Per the article, it may be doped with zinc, which is very not good in excess in water supplies. It'd need to be pretty heavily treated to make it suitable for any application where safety is a concern.
There's also the use case of ultra high pressure containers to store whatever gas under extreme pressure which is extremely useful in the short term for aerospace industry and exotic forms of energy storage for renewables (like compressed air) in micro-grids settings
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.
