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Post by BLDoom on Sept 28, 2016 17:20:30 GMT
Oh...thermocoupler exit temperature. Wow!Tiny reactor is tiny. And yes, super duper extreme rotational forces there.
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Post by RA2lover on Sept 28, 2016 17:33:25 GMT
Tried to make a cheaper beam drone after noticing how much its 4 RTGs cost. Still failed at designing a proper replacement, but ended up with a very compact nuclear reactor that beats it power output, mass and cost extremely easily.
ThermoelectricFissionReactorModule 334 kW Thermoelectric Fission Reactor 2
ReactorCoreDimensions_m 0.1 0.1
NuclearReactor
Coolant Sodium
Moderator Boron
ModeratorMass_kg 2
Fuel U-233 Dioxide
FuelMass_kg 2
FuelEnrichment_Percent 0.93
ControlRodComposition Boron
ControlRodMass_kg 1
NeutronReflector Boron
ReflectorThickness_m 0
AverageNeutronFlux__m2_s 1.6e+017
InnerTurbopump
Composition Boron
PumpRadius_m 0.052
RotationalSpeed_RPM 310
ThermocoupleInnerDimensions_m 0.1 0.1
Thermocouple
PTypeComposition Tantalum
NTypeComposition Nickel Chromium Iron
Length_m 0.0011
ThermocoupleExitTemperature_K 1000
OuterCoolant Sodium
OuterTurbopump
Composition Boron
PumpRadius_m 0.052
RotationalSpeed_RPM 320
1MW heat generation, 334kW output, weighs 11.6kg and costs 1.31kc. It also spits out 4.15W of radiation, but who cares? Radiation shielding is for the weak!(the actual reason is lithium-6 has godlike neutron absorption capabilities but melts too easily to be used as a neutron reflector)
On a side note, i want a 40% efficiency on this(so i can use a single reactor as a beam drone replacement), though i'm limited by both Tantalum's tendency to shatter on thermal expansion and Nickel-Chromium-Iron's temperature limiting thermodynamic efficiency.
Some design considerations i've found out while designing it:
- Most of a reator's mass is in radiation shielding. Low atomic number materials are great absorbers as they're lightweight and cheap. In particular, Lithium-6 is game-breakingly overpowered at absorbing it, with just a few milimeters of it being able to soak up nearly all radiation in a reactor. Sadly, it melts far too easily to be used as a neutron absorber, meaning you need to apply it elsewhere. Plastics can also work, though they perform much worse at the task. If you want to actually bundle radiation shielding inside the reactor package, Boron is probably the best at that task as it combines good absorption, low mass, cheap cost and a high melting point.
- Nuclear material enrichment costs don't seem to be present at the moment.
- Thermocouple design is vital(though i honestly haven't spent a lot of time with it in this design).
- High RPM fans tend to be heavier and consume more energy than slower fans with a larger area for the same performance.
- Sodium has a very high thermal conductivity which allows you to save a lot on active cooling requirements.
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Post by pokington on Sept 28, 2016 18:29:19 GMT
This, uh, this can't be right.  178 kg, 1mx.883m, 2.2MW, as replacement for the 7.5T, 1MW reactor. It's pretty trivial to get it over 3 MW too, but I was trying to see how small I could make it and keep it over a megawatt. This has to be some issue with the reactor model, but I don't have the background or knowledge to say what exactly is the problem. The power density is absurd compared to all the others in game. |
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Post by morrigi on Sept 28, 2016 18:40:20 GMT
The power density is absurd, and you're also leaking several kilowatts of radiation. That appears to be an issue.
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Post by pokington on Sept 28, 2016 19:10:53 GMT
The power density is absurd, and you're also leaking several kilowatts of radiation. That appears to be an issue. Ah, yeah. While that's true you also don't need radiation shielding for a drone, and that's what I was doing in that pic. My bad. At any rate, adding shielding adds about 100 kg, and about 3/4ths of a meter in length which is... pretty much irrelevant anyway.  RA2lover's reactor is even more silly. 334KW in 11.6kg. Edit: no, wait, 4mm of Lithium-6 drops radiation down to the tens of microWatts, so shielding isn't even an issue. That has to be a bug.Maybe I should pay more attention to what I'm doing. |
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Post by blothorn on Sept 28, 2016 19:15:11 GMT
RA2lover---for drones, especially, I would definitely go with high-output-temperature reactors. The only reason I know of to chase efficiency is to keep your heat generation down for cheaper flares, and ATM I do not know of anyone using missiles against drones (and if they do, the large radiators used by low-temperature reactors are probably the greatest vulnerability).
And yes, I definitely think something is wrong with the physical model to be allowing these, even ignoring radiation. I think I made a 1MW reactor that fits in a 1m cube...
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Post by qswitched on Sept 28, 2016 19:39:49 GMT
And yes, I definitely think something is wrong with the physical model to be allowing these, even ignoring radiation. I think I made a 1MW reactor that fits in a 1m cube... This is not actually a surprising result. One kilogram of enriched U-235 has 80 million MJ of energy stored in it. ( Link) Thus, a 1 MW reactor from 1 kg of U-235 has 80 million seconds of power in it, or about 925 days of power, or almost 3 years of power. In game, reactors are rated as how much power they can produce for 6 months (if you go lower, the editor will throw an error). You're still within the realm of reality with your design. Also note that 1 kg of U-235 is roughly 50 cubic centimeters, tiny. The trick is making sure the reactor can stay critical after so much of the uranium has fissioned, and being able to extract the power effectively via the turbomachinery. That part is the hard part, but you've done very well in that respect it seems. |
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Post by RA2lover on Sept 28, 2016 19:40:25 GMT
xkcd's what-if did some analysis on the effects of overpowered heat sources in a 1x1x1 cube. pumping 1.8MW into it would only heat it to about 1600K. |
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Post by qswitched on Sept 28, 2016 19:48:48 GMT
xkcd's what-if did some analysis on the effects of overpowered heat sources in a 1x1x1 cube. pumping 1.8MW into it would only heat it to about 1600K. He determines how a cube would radiate heat away, basic radiator stuff. The reactor is not a radiator, and would be very broken indeed if the outer shell of the reactor got hot enough to radiates like a radiator. |
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Post by quarkster on Sept 28, 2016 20:52:04 GMT
One mechanism which would add considerably more realism to the game is to model heat drop across the surface of the radiator, which is especially relevant at very high coolant temperatures like these.
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Post by blothorn on Sept 29, 2016 1:41:07 GMT
My realism concern was just the extreme temperature differentials---this reactor has listed 371K and 3097K components coexisting within the same .193m^3. I am not an expert on thermal insulation, but I would think that would be a colossal task.  |
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Post by RA2lover on Sept 29, 2016 1:52:17 GMT
That's the line bringing coolant from the radiators back to the reactor, which is outside the reactor itself. It's pegged to the melting point of the coolant, though - this might be a bug.
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Post by quarkster on Sept 29, 2016 2:01:16 GMT
The game also ignores neutron embrittlement. Qswitched has done an amazing job with physical modelling in this game, but many constraining factors have been left out.
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tuna
New Member
Posts: 33 
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Post by tuna on Sept 29, 2016 2:54:49 GMT
That's the line bringing coolant from the radiators back to the reactor, which is outside the reactor itself. It's pegged to the melting point of the coolant, though - this might be a bug. I am fairly certain that this is a bug. It's notable because the thermocouple stress is computed based on this value, not the radiator temperature, and this makes a few thermocouple options unusable at high reactor temperatures as they cannot be made strong enough to not shatter with the bogus 2800K dT, even though there should only be 300K dT between the reactor and the radiator. |
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tuna
New Member
Posts: 33
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Post by tuna on Sept 29, 2016 2:55:48 GMT
Also, thermocouple efficiency/strenght is backwards. According to the tooltip, thermocouples should become less efficient but stronger as they are made longer -- currently, the opposite is true.
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