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Diamond Nanothreads Could Support Space Elevator (space.com)
Taco Cowboy writes with news that Penn State researchers have discovered a way to produce ultra-thin diamond nanothreads that could be ideal for a space elevator. According to the report at Space.com, The team, led by chemistry professor John Badding, applied alternating cycles of pressure to isolated, liquid-state benzene molecules and were amazed to find that rings of carbon atoms assembled into neat and orderly chains. While they were expecting the benzene molecules to react in a disorganized way, they instead created a neat thread 20,000 times smaller than a strand of human hair but perhaps the strongest material ever made. ... Just recently, a team from the Queensland University of Technology in Australia modeled the diamond nanothreads using large-scale molecular dynamics simulations and concluded that the material is far more versatile than previously thought and has great promise for aerospace properties.
In The Fountains of Paradise, Arthur. C. Clarke wrote about the use of a diamond filament for building the space elevator. The main character, Dr. Morgan, carried around with him a retractable rope made of this filament. He uses it at one point to climb down a cliff face, and it's so thin it can be barely seen...
Kudos, Arthur...
And The Foundations of Paradise, Arthur. C. Clarke.
How exactly does a space elevator "save" energy for lifting loads to orbit?
The same way using a ladder saves energy over using a jetpack.
systemd is Roko's Basilisk.
The person you heard that from was wrong.
In a rocket,:
- Rockets are quite inefficient, about 16% energy efficient to reach orbit.
- You have to lift your propellant, only to throw it all away
- The rocket not only has to do work against gravitational potential, it also has to provide lateral kinetic energy to reach orbit. The kinetic energy component is huge.
For a space elevator:
- The lifting motors are highly efficient, you just have to keep the power beaming losses reasonable.
- You only have to work against gravitational potential. The tether/earth provides the lateral kinetic energy.
They are not even close to sufficient in weight bearing capacity for an earth space elevator. Nothing we have is within 3 orders of magnitude of being sufficient. Not even in the smallest testable quantities. Now, we can build a space elevator on the moon. But not from earth.
Will it turn into a pile of dust if it's hit by lightning?
The original NIAC study on the space elevator dealt with issues such as lightning, corrosion from atmospheric acid and oxygen, micrometeor strikes and aircraft exclusions zone. It also dealt with the mass required to anchor it, proposed how it would be built and which areas in the world would be suitable for the first one.
My ism, it's full of beliefs.
From the perspective of a space elevator, it's not. Read this paper linked from the article. There's no talk of space elevators, that's just their way to entice the reader into listening to them.
That is to say, the space elevator mention is just clickbait.
As the paper notes, "experimentally measured tensile Young's modulus for SWNTs ranges from 320 GPa to 1.47 TPa with the breaking strengths ranging from 13 to 52 GPa". A material with the density of SWNTs is generally considered to need at least 100-120 GPa irreversible yield strength (less than breaking strength) to make a "practical" elevator (although if you read those proposals it's hard to come across with any conclusion other than that they're being way too optimistic even with those numbers). Note: 13-52 GPa for individual tubes. Ropes of multiple tubes are 1-2 orders of magnitude weaker.
So what about these diamond nanothreads?
Their data is pretty consistent, with graphs showing a clear dropoff and stabilization around 56 GPa. Obviously nm-sized fibers are pretty worthless for the purposes of an elevator, there'd be way too little Van der Walls holding them together into a rope.
Now, these are just simulations. But more often than not real world seems to underperform simulations rather than overperform, so I wouldn't get too optimistic about the real-world greatly exceeding these figures. For example, early simulations of SWNTs said they'd be around 120GPa; few believe nowadays that they can even approach those figures.
But what about the density side of the equation? After all, a material can be weaker, but if it's correspondingly lighter, then that's not a problem. The density is not in the paper, but this cites the tenacity (breaking strength over mass) as 4.1e10^7 N-m/kg. While the yield strength is going to be a bit less than the breaking strength, it shouldn't be too far off - this means that the density should be somewhere less than - but not too much less than - 1,37g/cm^3. That's on the same order as SWNTs, unfortunately.
Short answer? We're still nowhere even remotely close to being even capable of making a space elevator.
Space elevators face such numerous problems anyway (really don't want to have to go into them all) that they're really not a fruitful avenue of pursuit. We'd do far better to direct such efforts to more realistic access methods, such as a Lofstrom loop or variant thereof, which requires no unobtanium and is far more efficient (space elevators lose huge amounts of energy to transmission losses, throwing away a large chunk of the advantage that they gain from bypassing the rocket equation). Active suspension via recirculating kinetic transfer, by one means or another, is something we can do today.
I hate to bring up our imminent arrest during your crazy time, but we gotta move.
At some point in time also a spider silk was the strongest material - stronger than steel. But I have yet to see a crane that uses spider silk to lift containers.
Wake me up when we can create a 1km long and 1cm thick rope from these diamond nanothreads.
Your post is simply incorrect.
1) Rockets are not "quite inefficient". Their Carnot efficiency is usually 80%, net propulsive efficiency around 70% - way better than a gasoline engine (~35%) or diesel engine (40-45%). What they suffer from is totally different: the rocket equation. This mandates exponentially increasing fuel needs to reach a given delta-V, with the exponent proportional to the ISP. But fuel costs have nothing to do with how expensive today's rockets are, we're nowhere near that limit. The Space Shuttle consumed about $2m of propellant to deliver 25 tonnes to LEO, or $80/kg. Using electricity at 100% efficiency and $0,80/kWh it would cost about $0,80/kg to reach orbit. Today's launch costs are about $5k-10k/kg for large launches (the Shuttle was said to be about $18k). So you can see that the fuel costs are just the tiniest fraction, and that it's the engineering challenges of cost-effective production and reuse that are the issue.
2) The "keeping power beaming losses reasonable" is the problem the parent was describing. There is no known way to efficiently transfer power to a small object over tens of thousands of kilometers. Direct transmission isn't even close with conventional conductors, a superconducting line would be many orders of magnitude too heavy, and the cable itself would not be a superconductor, and even if it were its cross section would be way too low. Batteries don't cut it in terms of energy density. And the requirements that climbers be very light precludes nuclear except for the most unrealistically-massive of space elevators. To make RF power beaming remotely efficient over such distances requires a receiving antenna taking up dozens of square kilometers. Laser power beaming means receiving end (solar cell) losses (which even if the solar cells are tuned to a particular frequency you're unlikely to do better than maybe 30-40%) and laser losses (high power lasers are generally in the ballpark of 0,1% efficient; diode lasers can reach up to 25% or so but have far too poor beam quality and are way too weak to be practical). And of course you need a frequency that minimizes atmospheric losses at that.
Perhaps some day power transmission over those distances might become practical, but today it isn't.
This is just the very start of the problems with space elevators, of course. I know space elevators make great books, but they're not practical in the real world. Look into actively suspended structures for your "direct climb to space" needs. They're buildable with today's materials and can get greater than 50% efficiency in energy transfer.
I hate to bring up our imminent arrest during your crazy time, but we gotta move.
You only have to work against gravitational potential. The tether/earth provides the lateral kinetic energy.
Any cargo climbing to the upper floor would need to gain a proper orbital velocity. It might get it from the ground or from the upper floor or from its own engine. It means that you would need to provide some fraction of the lateral kinetic energy by accelerating laterally either the cargo or the upper floor.
It will still be 50 years before it is built as everyone still laughs at it.
That is to say, the space elevator mention is just clickbait.
This has been happening a lot lately. Just a few articles down is a mention of videos of "execution-style killings" that apparently either the submitter or an editor (ha!) added for clickbait.
/. community to discuss the article in question properly. We don't need some editor giving our discussions "direction", rather the whole point of /. is as an avenue for people knowledgeable in specialized fields to weigh their opinions on the subjects. Adding speculation to the summary preempts the knowledgeable from properly examining the issue, and gives the trolls a foot hold from where to start derailing the discussion.
I'm not sure if the discussion that these things adds increases site revenue or not, but it completely destroys the ability of the knowledgeable
It is dangerous to be right when the government is wrong.
If you want more things to worry about before you "book a ride", the space elevator could take days to reach the top, during which time you have to slowly go through the wonderful Van Allen radiation belts. But maybe we will put up something to drain them of their charged particles by then. (in before all the people whining that draining the belts would somehow permanently remove them, or that the charged particles are the important part of the belts, rather than being the crap that they accumulate)
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
Solar cells may produce - on a clear day - 200W/m^2, if they're sun-tracking and unshadowed. A climber climbing over the course of two weeks (more on that in just a second, you need to climb far faster) has to climb 35,5 meters per second. A small 1 tonne climber with 2 tonnes of cargo requires 1 megawatt of power, meaning 5000 square meters. Think you can fit 5000 square meters of sun-tracking solar cells on a climber that only weighs one tonne?
Speed is important because it defines throughput, and your cables - even if you have some mythical unobtanium 100-120 Gpa diamond filament tether - are still very massive objects with very tiny objects climbing them, meaning you need high throughput to make them economically justifiable.
I don't think most people discussing space elevators realize how tiny the margins on these things have to be even with a cable made of unobtanium. Inside the atmosphere is irrelevant. It's the tiniest fraction of your 43000 kilometer trip, you have no margin to make a special case for in-atmosphere propulsion. It's only relevant for the additional problems it causes your cable, such as wind, lightning, ice, oxidation, etc.
Space elevators really aren't a good design. They're just totally impractical even when made of unobtanium. But science fiction has locked a generation onto this concept when there are far better concepts available.
I hate to bring up our imminent arrest during your crazy time, but we gotta move.
No space elevator designs that are even vaguely plausible include a moving cable. To understand why, consider the mass of such a cable: the energy required to accelerate it and then decelerate it for the cars to start and stop would be phenomenal. You could potentially have a loop that would continuously move in a circle, but you'd still have problems starting it. Just dropping things from the top wouldn't be enough, because you'd need to get them a fair way down before they'd stop orbiting and actually provide force in the correct direction. I don't even want to think about the lateral forces that such a structure would have to endure.
I am TheRaven on Soylent News
This is the longest "Oh yeah? Yo momma stinks!" post I have ever read.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
The moon's rotation is tidally locked to the earth (1 rotation/month makes it hard to stay in lunar orbit unless you are really far off & anything orbiting the moon that far off would be gravitationally perturbed by the earth) makes a classical beanstalk impossible. Other solutions like a rotating skyhook are theoretically possible but the mass concentrations make even that iffy.
Posted as anon to conserve mod points.
Unfortunately, for a space elevator, much more important than gravity is the spin speed of the celestial body it's attached to.
It needs to reach beyond the geostationary orbit of that body - meaning orbit of period equal to rotation period of its base body. That way it remains stretched.
Moon, with one spin per month, has no geostationary orbit at all (it's located beyond its Hall Sphere, meaning the Moon's gravity there is too weak to create orbital motion). So - no lunar space elevator, not due to technological limitations but because laws of physics say "no".
Did you RTFA? I'm not normally one to defend /. editors with their crappy proofing and duplicates, but in this case the click bait comes from outside /.
The original article and a few others: