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Post by n2maniac on Nov 25, 2016 20:09:30 GMT
So a lot of user designs run up against the UO2 melting point, and there isn't a higher melting uranium compound as far as I can find. Common current practice in many nuclear reactors around the world is to encapsulate UO2 pellets in zirconium metal. Suppose in CDE we encapsulated a uranium compound that melts at reactor temperatures inside an inert capsule that does not? Chemical compatibility is probably an issue, but since many of us flow molten sodium into UO2 I assume that may already be out the window. I am thinking of trying TaHfC with U metal and make a metamaterial that is 80% U, 20% encapsulant.
Thoughts from anyone else?
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Post by apophys on Nov 25, 2016 21:55:00 GMT
A limitation would be melting temperatures of control rods. Unless you want to use similarly encapsulated material (molten boron?), then you'll be limited to titanium diboride (3500K melting point), which is much less effective than the currently used boron nitride.
Diamond pellets would be interesting, because diamond is a good moderator in addition to being sturdy.
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Post by coaxjack on Nov 25, 2016 21:58:10 GMT
Do you mean a fully differentiated fuel ball, or an actual alloy or carbide (polycarbide?) or whatever?
I think a pebble-bed reactor is something that could be modeled in game, as there are some already running for real, but as far as I can see, they don't run very hot. Then again, the moderator on the spheres of fuel have all been graphite or silicon carbide, so who knows.
Also, how would you get the spheres to stay in a critical geometry in zero-g? I'm thinking the coolant flow would provide enough 'propulsion' to keep the pellets in place, because a spring or piston mechanism would almost certainly melt right away.
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Post by thorneel on Nov 25, 2016 22:51:27 GMT
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Post by n2maniac on Nov 29, 2016 9:32:40 GMT
Okay, went ahead and did it. I added meta-materials for 20% by volume Tantalum Hafnium Carbide (MP of 4488K) encapsulating 80% by volume either U-233 (as fuel), U-238 (as the required depleted fuel), and boron carbide (as a control rod). Some calculations I did kept the molar ratios and densities somewhat honest, while the game kept cost and nuclear properties honest. Nothing kept coefficient of thermal expansion mismatches, chemical incompatibility (hold on, we all run hot sodium around an oxide???), or uranium's boiling point in check. The results were ...slightly underwhelming. The reactor could essentially run 300K hotter before hitting the limits of the tantalum thermoelectrics (so radiator area is down to... 74% that it would otherwise be for the same electrical output), and a methane NTR could get up to about 7.5km/s ISP (rather than 6.2km/s with UO2, a factor of 1.21 gain). Cost and mass of both go up considerably due to tantalum, but it does not seem to be prohibitive (as they started relatively lightweight given most ships of mine that they serve on). Guess that is just a consequence of the underlying physics with their diminishing returns: T^1/2 on NTRs, and T^(4 - 1ish) but with a tiny T improvement on the thermoelectric fission reactor. Pictures of the units:  (Reference UO2 reactor it was based off of)
 Roughly optimized NTR using this:
 If anyone is interested in trying something out with it, I had to add the following files to C:\Users\[username]\AppData\Roaming\CDE\Mods\Data Ceramics.txt
Material Tantalum Hafnium Carbide filled with Boron Carbide
Elements Ta Hf C B
ElementCount 4 1 17.6 50.4
Density_kg__m3 4946
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
Fissiles.txt
Material Depleted Tantalum Hafnium Carbide filled with U
Elements U-238 Ta Hf C
ElementCount 21 4 1 5
Density_kg__m3 18210
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
Material Tantalum Hafnium Carbide filled with U-233
Elements U-233 Ta Hf C
ElementCount 21 4 1 5
Density_kg__m3 18210
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
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Post by dragonkid11 on Nov 29, 2016 14:27:58 GMT
Being able to increase methan NTR speed to 7.5 km/s from 6.2 km/s is still pretty damn good though.
Yes, it might not be as good as you think. But this 20% increase is still pretty damn good since it's practically a straight upgrade.
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Post by mmmfriedrice on Dec 3, 2016 1:55:17 GMT
If anyone is interested in trying something out with it, I had to add the following files to C:\Users\[username]\AppData\Roaming\CDE\Mods\Data Ceramics.txt
Material Tantalum Hafnium Carbide filled with Boron Carbide
Elements Ta Hf C B
ElementCount 4 1 17.6 50.4
Density_kg__m3 4946
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
Fissiles.txt
Material Depleted Tantalum Hafnium Carbide filled with U
Elements U-238 Ta Hf C
ElementCount 21 4 1 5
Density_kg__m3 18210
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
Material Tantalum Hafnium Carbide filled with U-233
Elements U-233 Ta Hf C
ElementCount 21 4 1 5
Density_kg__m3 18210
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
So has anyone else run into issues where the game doesn't seem to save the modded materials every time you quit and reload? Every time I design a module and leave the game to return later, it bugs out and replaces it with the default materials (aluminum for structural, Am-241 for fissiles). |
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Post by n2maniac on Dec 3, 2016 3:53:35 GMT
If anyone is interested in trying something out with it, I had to add the following files to C:\Users\[username]\AppData\Roaming\CDE\Mods\Data Ceramics.txt
Material Tantalum Hafnium Carbide filled with Boron Carbide
Elements Ta Hf C B
ElementCount 4 1 17.6 50.4
Density_kg__m3 4946
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
Fissiles.txt
Material Depleted Tantalum Hafnium Carbide filled with U
Elements U-238 Ta Hf C
ElementCount 21 4 1 5
Density_kg__m3 18210
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
Material Tantalum Hafnium Carbide filled with U-233
Elements U-233 Ta Hf C
ElementCount 21 4 1 5
Density_kg__m3 18210
YieldStrength_MPa 270
UltimateTensileStrength_MPa 590
YoungsModulus_GPa 550
ShearModulus_GPa 223.9
MeltingPoint_K 4488
SpecificHeat_J__kg_K 192
ThermalConductivity_W__m_K 22
ThermalExpansion__K 6.76e-7
Resistivity_Ohm_m 2.9e-7
RefractiveIndex Tantalum
RoughnessCoefficient 0.2
So has anyone else run into issues where the game doesn't seem to save the modded materials every time you quit and reload? Every time I design a module and leave the game to return later, it bugs out and replaces it with the default materials (aluminum for structural, Am-241 for fissiles). I did notice that too, and would also be interested in a solution. It is quite inconvenient to have to do this to every part of a ship using that stuff. |
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Post by RiftandRend on Dec 4, 2016 1:57:30 GMT
Add the materials to the core game files found inside it's steam directory. That totally solves material related bugs for me.
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Post by n2maniac on Dec 4, 2016 21:44:15 GMT
Add the materials to the core game files found inside it's steam directory. That totally solves material related bugs for me. Wow, that works. |
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Post by zuthal on Dec 5, 2016 0:57:41 GMT
Being able to increase methan NTR speed to 7.5 km/s from 6.2 km/s is still pretty damn good though. Yes, it might not be as good as you think. But this 20% increase is still pretty damn good since it's practically a straight upgrade. Especially since the needed mass ratio for a certain delta-V is equal to e^(deltaV/V_e), which means that you are cutting fuel requirements rather drastically. For example, to get 5 km/s of delta-V, a ship with the standard 6.2 km/s NTR needs a mass ratio of 2.24. With the 7.48 km/s upgraded version, it only needs one of 1.95 - already a 13% reduction in mass ratio. For 10 km/s of delta-V, it is 5.02 standard and 3.8 upgraded - a 24.3% reduction. And less fuel needed means less mass for tanks and armour needed means less fuel needed... the Tyranny of the Rocket Equation works both ways! |
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Post by newageofpower on Dec 5, 2016 9:21:02 GMT
Having a real hard time getting my NTRs that high without a weak thrust/mass ratio. Got a design description/link/screenshot? |
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Post by zuthal on Dec 5, 2016 20:37:09 GMT
 This one's just a lil' one, but you could scale it up. 247 g0 TWR is high enough, yes? |
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Post by lol on Dec 5, 2016 23:15:52 GMT
This one's just a lil' one, but you could scale it up. 247 g0 TWR is high enough, yes? >gimbal speed Everything violently disassembles. |
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Post by zuthal on Dec 5, 2016 23:32:38 GMT
Yeah, especially since the thrust chamber is 100 micron thick boron foil  The engine should rapidly fail under the stresses of gimballing, but /shrug |
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The engine should rapidly fail under the stresses of gimballing, but /shrug