[FlamingCobra]

What we'd need is something that can be easily produced within the ship, rather than having to be constantly refilled

wat

You'd still have to carry (and refill) the materials used to make the fuel. Conservation of mass kind of bites you on the ass here.

Unless I completely misunderstood what you're trying to say.

maybe what he means is a fuel that we could harvest the materials from asteroids that pass by and then manufacture on the ship?

[redsniper]

Why the **** would you make a space elevator tether out of diamond? Holy ****.

because only diamond, carbon nanotubes, and graphene have the breaking lengths necessary to make the tether. If it were made of any other material it would collapse under its own weight.

Notice that all of the materials mentioned are made purely of carbon.

I believe redsniper knows what he's talking about.

I know what I'm talking about.

Material Science and Mechanical Engineering Education for Hard Light Productions: Round Two
(Round 1 was the last time we talked about space elevators when you guys were smugly comparing grades of steel for the tether based on their hardness () and tensile strength ())

When you apply a load to an object, it deforms. Like when we put our tether in tension, it gets longer. Up to a point, this deformation is reversible; the object will return to its original size when the load is removed, sort of like a spring. This is called the elastic range and the deformation is elastic deformation. When loaded further, the object will permanently deform. That is, even when the load is removed, the dimensions of the object will be different from what they were originally. This is called the plastic range, and the permanent deformation is plastic deformation.

Elastic deformation is directly proportional to load (double the load, double the deformation..) thus it's predictable. Plastic deformation.... is not. When an object crosses from the elastic range to the plastic range, we say it "yields," and the stress (force over area) it's experiencing is the yield stress or yield strength. We design stuff around the yield strength and always try to stay well within the elastic range. Now if your object goes plastic and you continue to increase the load, eventually it's going to break. The stress at the breaking point is the tensile strength. (The caveat here is that with ceramics and really brittle materials, the plastic range is tiny; your object would stretch a tiny bit under increased loading and then just snap. In those cases you would design around tensile strength because it's basically the same as yield strength.) This is all well and good for perfectly formed objects, and diamond actually has a pretty high tensile strength compared to steel and such, but there are no perfect objects.

Another crucial failure mode besides overloading is crack growth or brittle fracture. That is, if you load an object with a crack in it, the stress tends to concentrate at the tip of the crack, causing the crack to grow until your objects cross section so small that then it fails by overloading. We quantify a material's resistance to crack growth with something called fracture toughness. It's not as straightforward as yield strength, having some rather funky units associated with it, but basically higher is better. Fracture toughness is low for brittle materials and high for ductile materials. Stuff like steel and aluminum has good fracture toughness, while stuff like iron and diamond does not. You could actually pretty easily shatter a diamond just by smacking it with a hammer.

Hardness is basically just a relative measure of how easily a material gets scratched. You use it to figure out how a material will get affected by wear and small localized surface deformations. There's a rough positive correlation between hardness and yield strength (in metals at least), but hard materials also tend to be more brittle.

Breaking length I hadn't heard of and it's actually kind of an interesting way to express strength to weight ratio.

breaking length, also known as self support length: the maximum length of a vertical column of the material (assuming a fixed cross-section) that could suspend its own weight when supported only at the top. For this measurement, the definition of weight is the force of gravity at the Earth's surface applying to the entire length of the material, not diminishing with height.

However it all kind of falls apart because of the scale and loading conditions of something like the space elevator because

when supported only at the top

Nope, and...

For this measurement, the definition of weight is the force of gravity at the Earth's surface applying to the entire length of the material, not diminishing with height.

the force of gravity at the Earth's surface applying to the entire length of the material, not diminishing with height.

the entire length of the material, not diminishing with height.

the entire length of the material

sea level to geosynchronous orbit

1g up to up to geosynch orbit? Nope nope nope nope nope. No, no, no way, no.

So what would the loading conditions for our tether actually be? Well.... I don't know. I don't know enough about orbital mechanics or proposed space elevator design to discuss this confidently. It would probably be complicated though. I mean non-uniform gravity field? Geez... Furthermore, depending on how steadily we can keep the anchor in place, our tether might see cyclic stresses, which are a whole other can of worms.

So, diamond is very hard and strong, but it's WAY too brittle for a structural material. We're a long ways off from manufacturing useful nanotubes that actually meet their theoretical tensile strength. Graphene is like, a one atom thick layer of carbon, last I heard. I was under the impression people were more excited about using it for electric circuits than for structural stuff.

tl;dr: diamond may be the strongest metal know to man, but it's too brittle for a space elevator or just about anything else.



Or at least that's how I see it, but what do I know, I'm only a practicing mechanical engineer. 

[Nuke]

carbon is a non-metal, lol.

we need to be able to manufacture very long nanotubes. these would then be woven into larger fibers, and those fibers woven into even thicker fibers, and so on as with cable manufacture. these would need to be embedded in some kind of binding material. carbon fiber materials use epoxy but im not sure if that would work for this application. also i think right now we can only grow nanotubes a few mm at a time. i have serious doubts of being able to actually build a space elevator though. and when it has a high enough technological readiness level, that the need for the tether would have gone to cheaper launch platforms and off planet manufacturing.

[redsniper]

carbon is a non-metal, lol.

It's a meme.

And yeah, the more I think and read about it, the more I think it would be better to work on SSTO stuff like the Skylon, assembling stuff in space, and establishing more permanent stations and moon bases and stuff.

[deathfun]

What we'd need is something that can be easily produced within the ship, rather than having to be constantly refilled

wat

You'd still have to carry (and refill) the materials used to make the fuel. Conservation of mass kind of bites you on the ass here.

Unless I completely misunderstood what you're trying to say.

I can see how that was misunderstood. Essentially, instead of having actual fuel creating propulsion, you have an energy based system which is perpetually generated (that is to say, creates as much as it uses on it's own rather than having an outside source [say for lack of a better example, gasoline] being used). Since this is the future I am talking about, I leave open for any possibilities.

To simplify the above, a generator that generates it's own **** to generate it while providing **** to generate the engines. This takes away the need to carry fuel, or to mine for it

And yes, I know only speculation and theories will determine how this would be possible to obtain.

[Scotty]

Thermodynamics doesn't really like your idea, sorry to say.

[watsisname]

Three Laws of Thermodynamics, for laymen:

1:  You cannot win.
2:  You cannot break even.
3:  You cannot get out of the game.

[FlamingCobra]

carbon is a non-metal, lol.

we need to be able to manufacture very long nanotubes. these would then be woven into larger fibers, and those fibers woven into even thicker fibers, and so on as with cable manufacture. these would need to be embedded in some kind of binding material. carbon fiber materials use epoxy but im not sure if that would work for this application. also i think right now we can only grow nanotubes a few mm at a time. i have serious doubts of being able to actually build a space elevator though. and when it has a high enough technological readiness level, that the need for the tether would have gone to cheaper launch platforms and off planet manufacturing.

good luck getting nanotube fibers to line up with each other so they can link together.

What we'd need is something that can be easily produced within the ship, rather than having to be constantly refilled

wat

You'd still have to carry (and refill) the materials used to make the fuel. Conservation of mass kind of bites you on the ass here.

Unless I completely misunderstood what you're trying to say.

I can see how that was misunderstood. Essentially, instead of having actual fuel creating propulsion, you have an energy based system which is perpetually generated (that is to say, creates as much as it uses on it's own rather than having an outside source [say for lack of a better example, gasoline] being used). Since this is the future I am talking about, I leave open for any possibilities.

To simplify the above, a generator that generates it's own **** to generate it while providing **** to generate the engines. This takes away the need to carry fuel, or to mine for it

And yes, I know only speculation and theories will determine how this would be possible to obtain.

you mean like a breeder reactor, then?

-snip-

wat about that space fountain thang then? that was a good read, btw. I do like information. As long as it's not history..... or grammar.

Three Laws of Thermodynamics, for laymen:

1:  You cannot win.
2:  You cannot break even.
3:  You cannot get out of the game.

So I guess ITER is pointless?

[The E]

So I guess ITER is pointless?

Please learn to read. The answer you quoted was in response to this:

To simplify the above, a generator that generates it's own **** to generate it while providing **** to generate the engines. This takes away the need to carry fuel, or to mine for it

If you do not know why this doesn't work, I would suggest you read up on the idea of the perpetuum mobile.

ITER, on the other hand, is a design for a fusion reactor. One that very definitely follows all the laws of thermodynamics. Because in this universe, you kinda have to.

[FlamingCobra]

So I guess ITER is pointless?

Please learn to read. The answer you quoted was in response to this:

To simplify the above, a generator that generates it's own **** to generate it while providing **** to generate the engines. This takes away the need to carry fuel, or to mine for it

If you do not know why this doesn't work, I would suggest you read up on the idea of the perpetuum mobile.

ITER, on the other hand, is a design for a fusion reactor. One that very definitely follows all the laws of thermodynamics. Because in this universe, you kinda have to.

because matter cannot be created or destroyed, generators cannot generate their own ****. I guess that's what you're getting at?

unless you could somehow harness the principle that particles spontaneously appear and disappear in a vacuum.

[The E]

because matter cannot be created or destroyed

 

Let me introduce you to a friend of mine. He's called E = mc^2. Matter can be created, and destroyed (for values of "created" that involve being converted from energy, and values of "destroyed" that involve being converted into energy).

Then let us examine the laws of thermodynamics. Basically, they state that it is impossible for a machine to create enough energy to both power itself and other machines without an external fuel source.

Regarding vacuum energy, the jury's still out on that one. The main problem being that nobody knows how to extract it.

[LordPomposity]

you mean like a breeder reactor, then?

A breeder reactor functions by converting non-fissile isotopes to fissile ones. You still need the non-fissile isotopes to begin with.

[Nuke]

you mean like a breeder reactor, then?

a breeder reactor just makes more efficient use of the nuclear fuel by "breeding" other useful isotopes (even transmuting other elements) from the fuel which in turn can be burned or extracted and re-processed into other fuels. current light water rectors only use up a fraction of the material and this is removed and put into long term storage. the fuel is still highly radioactive because we didnt use up all the energy in the material. this does not break thermodynamics. its like gasolene, 75% of its energy is lost as waste heat so you only get a fraction of the energy out of it. in the same way as you only get a fraction of the energy out of the nuclear material and whats left is a hot but useless fuel rod assembly.

[FlamingCobra]

because matter cannot be created or destroyed

 

Let me introduce you to a friend of mine. He's called E = mc^2. Matter can be created, and destroyed (for values of "created" that involve being converted from energy, and values of "destroyed" that involve being converted into energy).

Then let us examine the laws of thermodynamics. Basically, they state that it is impossible for a machine to create enough energy to both power itself and other machines without an external fuel source.

Regarding vacuum energy, the jury's still out on that one. The main problem being that nobody knows how to extract it.

Well I was always told that matter cannot be created or destroyed and then I was told that energy cannot be created or destroyed and then I was told matter and energy are interchangeable. You're affirming that last one.

In the fifties I bet no one knew how to contain antimatter either. But we've made great strides (Optical tweezers). In time I'm sure we'll figure that one out as well. But could it be done on a large enough scale to even be useful?

Ok maybe antimatter is a bad example but you get what I'm saying.

you mean like a breeder reactor, then?

a breeder reactor just makes more efficient use of the nuclear fuel by "breeding" other useful isotopes (even transmuting other elements) from the fuel which in turn can be burned or extracted and re-processed into other fuels. current light water rectors only use up a fraction of the material and this is removed and put into long term storage. the fuel is still highly radioactive because we didnt use up all the energy in the material. this does not break thermodynamics. its like gasolene, 75% of its energy is lost as waste heat so you only get a fraction of the energy out of it. in the same way as you only get a fraction of the energy out of the nuclear material and whats left is a hot but useless fuel rod assembly.

You missed my point. It extends the life of your fuel.

[Nuke]

You missed my point. It extends the life of your fuel.

you dont have no point.

[The E]

In the fifties I bet no one knew how to contain antimatter either. But we've made great strides (Optical tweezers). In time I'm sure we'll figure that one out as well. But could it be done on a large enough scale to even be useful?

Correction: The problem of antimatter containment never existed. We knew how to do it for a very long problem, the issue is that we can't generate enough of the stuff to be worth containing in the first place. Also, you are really really wrong. The Penning trap, which is used to capture and hold charged antimatter, was developed in the 50s. Although the first one was built in '59, the research it was based on came earlier. The current record for continuous antimatter containment (for antihydrogen) is about 1 kilosecond (or roughly 17 Minutes), for less than 300 atoms, btw.

And optical tweezers? I'm sorry, but what do they have to do with accessing vacuum energy? Using them as an analogy is like somebody in the fifties saying "We can breach the sound barrier, I am sure we will be able to travel at near lightspeed by the year 2000".

[FlamingCobra]

In the fifties I bet no one knew how to contain antimatter either. But we've made great strides (Optical tweezers). In time I'm sure we'll figure that one out as well. But could it be done on a large enough scale to even be useful?

Correction: The problem of antimatter containment never existed. We knew how to do it for a very long problem, the issue is that we can't generate enough of the stuff to be worth containing in the first place. Also, you are really really wrong. The Penning trap, which is used to capture and hold charged antimatter, was developed in the 50s. Although the first one was built in '59, the research it was based on came earlier. The current record for continuous antimatter containment (for antihydrogen) is about 1 kilosecond (or roughly 17 Minutes), for less than 300 atoms, btw.

And optical tweezers? I'm sorry, but what do they have to do with accessing vacuum energy? Using them as an analogy is like somebody in the fifties saying "We can breach the sound barrier, I am sure we will be able to travel at near lightspeed by the year 2000".

Optical tweezers are a way to contain antimatter, E. They have nothing to do with accessing vacuum energy. And at the end I said it probably wasn't a very good analogy. I was just trying to make an example. And I failed. I'm sure you could think of dozens off the top of your head.

Now for one of my long unanswered questions:
E, why is your country so overwhelmingly anti-nuclear?

EDIT: OK, I got one. For the longest time, alchemists sought to change lead into gold. But now, scientists can do this in nuclear reactors (it might be expensive, inefficient, AND pointless, but it can be done.)

[deathfun]

Thermodynamics doesn't really like your idea, sorry to say.

I know
Hence why I don't live in a world where it exists! Ha! Take that factual science!

you dont have no point.

DOUBLE NEGATIVE

[The E]

Now for one of my long unanswered questions:
E, why is your country so overwhelmingly anti-nuclear?

FlamingCobra, why do you ask offtopic questions?

EDIT: OK, I got one. For the longest time, alchemists sought to change lead into gold. But now, scientists can do this in nuclear reactors (it might be expensive, inefficient, AND pointless, but it can be done.)

AAAAAAAHAHAHAHAHAAAAAA

ROFL

Creating Gold in a nuclear reactor? Please explain to us how you get from Uranium or Plutonium to Gold via the power of nuclear decay. Then explain why this isn't done industrially (Gold being an incredibly useful metal to have in conductors).

EDIT: Ah, seems like you CAN create Gold. By bombarding Platinum or Mercury with Neutrons, which produces minuscule amounts of gold. So yeah. Pointless.

[FlamingCobra]

-snip-

EDIT: OK, I got one. For the longest time, alchemists sought to change lead into gold. But now, scientists can do this in nuclear reactors (it might be expensive, inefficient, AND pointless, but it can be done.)

AAAAAAAHAHAHAHAHAAAAAA

ROFL

Creating Gold in a nuclear reactor? Please explain to us how you get from Uranium or Plutonium to Gold via the power of nuclear decay. Then explain why this isn't done industrially (Gold being an incredibly useful metal to have in conductors).

EDIT: Ah, seems like you CAN create Gold. By bombarding Platinum or Mercury with Neutrons, which produces minuscule amounts of gold. So yeah. Pointless.

You totally missed my point.
1. I like to use ADHD as an excuse. Not too off-topic though, since I was talking about nuclear reactors.

2. I was reading up on the Casimir effect and I was wondering if its ability to create a negative-mass region could be applied to the space elevator.