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Post by shiolle on Nov 15, 2016 12:35:45 GMT
There was a thread about one material dominating another, but I decided to start this one to see what other people think on the topic. So, here is my list: 1) Diamond. It is unclear how large solid diamonds of various shapes can be produced cheaply and in large quantities. 2) Amorphous carbon. It is unclear to me how you can build anything basically from soot, or this. Amorphous carbon doesn't have crystalline structure by definition. I can imagine a kind of "sandbag" armor, made out of bags of amorphous carbon, but since we are controlling every material down to fractions of a millimeter, wouldn't we need to specify materials of whatever contains such armor as well? Still you can build rocket engines out of it (and good ones too!). 3) Many chemical reactions are not factored when you bring two or more different materials that should react under operational temperatures. Lithium tanks filled with water are the most obvious example, but I'm sure there are many others. Unfortunately, my knowledge of chemistry is lacking, so I can't recognize if something is not right when I see it. 4) Things made out of extremely thin foils. When I see an engine bell with a thickness of 1/10th of a millimeter the first thing I can think of is "how come it doesn't crumple"? In general, it appears to me that a lot of miniaturized designs rely on components that would make them impossible to handle (like the aforementioned engine bell). I wonder if it is reasonable for some sliders to go as low as they do. |
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Post by ash19256 on Nov 18, 2016 13:32:10 GMT
4) Things made out of extremely thin foils. When I see an engine bell with a thickness of 1/10th of a millimeter the first thing I can think of is "how come it doesn't crumple"? In general, it appears to me that a lot of miniaturized designs rely on components that would make them impossible to handle (like the aforementioned engine bell). I wonder if it is reasonable for some sliders to go as low as they do. My understanding of it is that because these engines aren't designed for use outside of an atmosphere, they only have to deal with the mechanical stresses of operating as engines, which can be lowered to the point where foils are a legitimate option. Granted, it does appear that mechanical stresses from gimballing aren't modeled in the game, so these foil engines are able to gimbal at extreme rates without problems, which is somewhat unrealistic. |
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Post by cuddlefish on Nov 18, 2016 13:54:38 GMT
I think the consensus was that amorphous Carbon (and Boron) were both intending to represent big chaotic tangled messes of nanotubes?
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Post by apophys on Nov 18, 2016 15:50:14 GMT
1) Diamond. It is unclear how large solid diamonds of various shapes can be produced cheaply and in large quantities. TL;DR: Settling a gas of carbon can grow diamond sheets, on irregular surfaces even. One potential application is non-stick frying pans. |
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Post by shiolle on Nov 18, 2016 17:31:26 GMT
My understanding of it is that because these engines aren't designed for use outside of an atmosphere, they only have to deal with the mechanical stresses of operating as engines, which can be lowered to the point where foils are a legitimate option. Granted, it does appear that mechanical stresses from gimballing aren't modeled in the game, so these foil engines are able to gimbal at extreme rates without problems, which is somewhat unrealistic. But they will suffer many other mechanical stresses as well. You need to load and unload these missiles/drones. They move inside magazines in preparation for launch. They need maintenance. They probably suffer a few gees of lateral acceleration during launch. If you can ruin an engine with a gentle touch of your finger, they are probably not very serviceable. I think the consensus was that amorphous Carbon (and Boron) were both intending to represent big chaotic tangled messes of nanotubes? is a specific type of allotrope of carbon. It shouldn't have any regular crystalline structure like carbon nanotubes have. Here is the only thing I saw QSwitch say about the matter: childrenofadeadearth.boards.net/post/1323. Where can I read about that consensus? On the other hand, at the time of writing this, I didn't realize that diamond-like carbon is also a type of amorphous carbon, and DLC could be made pretty rigid. So maybe it's something like this, but it has nothing to do with carbon nanotubes as far as I can tell. It's very expensive. My main problem with diamonds isn't impossibility to produce them at all, but their price. According to this this report synthetic diamonds, including those produced by CVD, are around 50 times more expensive than natural diamonds (page 79). That's around 12.5 million US dollars per kg. Of course we can't say it will always stay like this. For example this can bring the cost down, but currently there is no technology that can bring down the cost. |
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Post by zuthal on Nov 22, 2016 1:24:06 GMT
Most materials with fluorine - you can without problem pump fluorine through a lithium turbopump, for example. According to my knowledge of chemistry, the turbopump should rapidly and violently combust.
Also, being able to make guns out of plastic - because the temperature at the inside of the barrel wall would probably be enough to melt/decompose it.
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Post by someusername6 on Nov 22, 2016 2:07:56 GMT
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Post by zuthal on Nov 22, 2016 2:15:22 GMT
See, the one issue I have with that is the ability of the coating to stay on while the turbopump is spinning at several thousand rpm. But I guess the engine does only need to last for a minute or two of total burn time. For fluorine-based capships, I'll use more reasonable materials, though... then again, what the hell even IS compatible with fluorine, and also with hot (if diluted in hydrogen) HF, if the engines use a preburner cycle?
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Post by n2maniac on Nov 22, 2016 3:29:17 GMT
Sodium, heavy water, etc as a reactor coolant for a reactor operating with fuel rods at 3200K. These would be gasses at that point, with water substantially dissociated. Would affect reactor design substantially unless swapping to a higher-melting metal (eg. silver, which would be likely).
Operating turbopump materials near their melting point without strength loss or creep issues. This is the ultimate limiter of turbines IRL. Probably not a huge issue.
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Post by Easy on Nov 22, 2016 3:49:09 GMT
Sodium, heavy water, etc as a reactor coolant for a reactor operating with fuel rods at 3200K. These would be gasses at that point, with water substantially dissociated. Would affect reactor design substantially unless swapping to a higher-melting metal (eg. silver, which would be likely). Operating turbopump materials near their melting point without strength loss or creep issues. This is the ultimate limiter of turbines IRL. Probably not a huge issue. High pressure should keep the fluid liquid. PWR is literally pressurized water reactor. Most nuclear reactors are PWR. Don't know if or how well the game models it. |
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Post by n2maniac on Nov 22, 2016 4:03:52 GMT
Sodium, heavy water, etc as a reactor coolant for a reactor operating with fuel rods at 3200K. These would be gasses at that point, with water substantially dissociated. Would affect reactor design substantially unless swapping to a higher-melting metal (eg. silver, which would be likely). Operating turbopump materials near their melting point without strength loss or creep issues. This is the ultimate limiter of turbines IRL. Probably not a huge issue. High pressure should keep the fluid liquid. PWR is literally pressurized water reactor. Most nuclear reactors are PWR. Don't know if or how well the game models it. In principle, yes, you can push the boiling point up a bit. Sodium's boiling point starts at the 1100-1200K range. In practice, the pressure needed to do this rises exponentially up until it starts flirting with the critical point. Above the critical point, there is no "liquid phase", it is just a supercritical fluid with pressure-dependent properties. Some example critical temperatures and pressures in question: Water: 650K, 22MPa Sodium (dang it wikipedia, making me search elsewhere): 2600K, 35MPa Lithium: 3200K, 66MPa (I almost don't believe that one given the coincidence with reactor temps, but whatever) Mercury: 1750K, 174MPa Silver: Google trolls me with silver speculators, nevermind... Huh, so pressures are painful but not as problematic as I was thinking. Temperatures... make me want to switch from sodium coolant to lithium coolant. |
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Post by zuthal on Nov 22, 2016 9:53:41 GMT
Also, running a reactor with supercritical coolant isn't really that big a problem in principle, besides needing to contain the necessary pressure.
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Post by n2maniac on Nov 22, 2016 23:12:30 GMT
Also, running a reactor with supercritical coolant isn't really that big a problem in principle, besides needing to contain the necessary pressure. I would agree with that statement. That being said, the wonderful thermal conductivities of metals with their shared valence electrons may or may not be useful at that point (useful metric is the Prandtl number, comparing thermal and momentum diffusivity. Note the wonderfully low values for mercury and potassium, but substantially higher numbers for gasses). Can't find much of a reference on how the thermal properties of super-critical metals at 1000s of K are compared to the liquid and gaseous states act. If anyone knows of one, I would be greatly interested in reading it (mostly for my own education, but also to give faith that humanity is not so shy as to avoid antagonizing metals above their critical point). |
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Post by zuthal on Nov 22, 2016 23:52:34 GMT
You are talking about the species that made an oxidiser stronger than pure oxygen, that burns such things as sand and asbestos and a molecule with two carbons, fourteen nitrogens and no hydrogens. I bet you some madman has done it. And while I couldn't find precise data for supercritical sodium, this paper suggests that heat capacity for both gas and liquid increases sharply towards the critical point, while viscosity and thermal conductivity (at least for the liquid) decrease, which makes sense to me, as supercritical fluid generally combine liquid-like densities (and thus likely heat capacities) with gas-like viscosities. One consequence would be though, I think, that the supercritical fluid would be much easier to pump than its corresponding liquid, due to much lower viscosity. |
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Post by n2maniac on Nov 23, 2016 0:58:10 GMT
You are talking about the species that made an oxidiser stronger than pure oxygen, that burns such things as sand and asbestos and a molecule with two carbons, fourteen nitrogens and no hydrogens. I bet you some madman has done it. And while I couldn't find precise data for supercritical sodium, this paper suggests that heat capacity for both gas and liquid increases sharply towards the critical point, while viscosity and thermal conductivity (at least for the liquid) decrease, which makes sense to me, as supercritical fluid generally combine liquid-like densities (and thus likely heat capacities) with gas-like viscosities. One consequence would be though, I think, that the supercritical fluid would be much easier to pump than its corresponding liquid, due to much lower viscosity. Okay, I am bad at search terms. Yea, so my original point it somewhat alluded to in there: its thermal conductivity in the gaseous state is on the order of 0.05 W/mK (fig 2.1-10), versus around 50 W/mK in the liquid state at 1100K and substantially lower as the critical point is approached (eventually syncing up with the gas phase thermal conductivity). Yes, viscosity falls from 170 uPa*s (table 2.2-1, assuming the logical - sign typo) to 58 uPa*s from 1100K to its critical point. So, in that range it is 3x less viscous and 100x less thermally conductive. This sounds like the pocket reactors will be substantially less effective. For heat capacity, I think I just learned something today. Operating a coolant at its critical pressure around its critical temperature (so above and below) will effectively increase its heat capacity substantially across a narrow temperature range. This paper on water gives a good illustration (fig 6e). It feels analogous to the latent heat of vaporization (transiting from inter-molecular forces being more or less important), but blurred. |
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