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Post by zuthal on Dec 30, 2023 4:59:09 GMT
This is actually a lot less bad than it seems. 10 g of copper at 650 K has, even taken relative to 0 K, about 2.5 kJ of heat. If it were moving at 5 km/s, it would already have a kinetic energy of 125 kJ. Hypervelocity projectiles impact with an energy so far in excess of what is required to vapourise them that their pre-impact temperature only matters if it is hot enough for the projectile to melt and as a result disperse.
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Post by zuthal on Oct 8, 2018 21:09:09 GMT
One note about turnabout time: I find that (at least for the very light, RCS-steered missiles I like to build) two seconds is a good spot to aim for - it give good maneuverability without an unacceptably large degree of oscillation.
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Post by zuthal on Aug 11, 2018 14:03:17 GMT
I am, as are probably quite a few of us here, a bit curious as to why exactly silver gallium selenide is such an amazing nonlinear optic, allowing 100% efficiency. Well, I did a dive into the RefractionIndices.txt file, and lo and behold, Silver Gallium Selenide has no entry at all for the k value - where all other materials do have one, and from what I can tell, the k value in the complex refractive index governs the absorptive properties of the material. Even more interestingly, this k value appears to be either missing or set to 0 for the refractive indices of all lasing media, nonlinear optics or other transparent materials.
Could someone with more of an understanding of optics/the complex refractive index chime in and tell me if this should be that way or not?
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Post by zuthal on Jan 23, 2018 0:31:56 GMT
Isn't the extra 4.8 MeV in gamma rays? Isn't this kind of bad? The extra 4.8 MeV should be (I think) mostly in the kinetic energy of the reaction products, i.e. tritium and helium-4 nuclei. I am not sure how much of the energy will be either immediately released as gammas, or turned into xrays due to bremsstrahlung.
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Post by zuthal on Jan 20, 2018 21:16:59 GMT
I mean, this would he a good reason to actually use a neutron reflector. Making a similar issue regarding "fuel will be used up by 6 months" we could probably add in "radiation shield will decompose by 6 months, radiation will exceed (I forgot the magic #)". True, but the amount of Li you are using will be pretty low compared to the shield - a 1 cm thick Li-6 shield is about 5 kg/m^2 or so, and while absorbing 63.7 kW of neutron radiation, you as I said only consume 125 g of Lithium-6 per year... so really, you just have a tiny reserve tank for your liquid lithium rad shield system.
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Post by zuthal on Jan 20, 2018 0:05:05 GMT
Everyone likes to talk about (or at least, it has become a sort of meme on the Discord server) how our lithium-6 radiation shields are quite unrealistic - but are they really? The most common objection to them is that they would be ablated, turning into a mixture of helium and tritium, by the neutron flux - but that is not something that happens extremely quickly. Another objection is the heat, which is an issue - especially as the reaction between Li-6 and a fission neutron, itself already having about 1 MeV of energy, releases another 4.8 MeV. This, if you limit your shield to being solid and radiating off both faces, limits the neutron flux it can withstand without melting to about 5.1*10^15 m^-2 s^-1 - at which rate, it would take 343 years to ablate away 1 mm of lithium.
However, there is no reason a neutron shield has to be solid. It can, in fact, be a liquid - and at 1 atm of pressure, lithium boils at about 1600 K. This means that, for each 1 m^2 of radiator area, you can absorb a neutron flux of 4*10^17 s^-1 per m^2 of radiator area - or, in more typical CoaDE reactor terms, a reactor radiation hazard of 63.7 kW, assuming 1 MeV neutrons. The liquid radiation shield also allows an easy way to deal with the gas that is produced - you simply include a centrifugal gas separator into your line somewhere, where the helium bubbles out (the tritium reacts with the hot lithium to lithium tritide, and eventually decays to helium-3). And this system wouldn't use up that much lithium - at a flux of 4*10^17 s^-1, it consumes about 125 g of lithium-6 per year.
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Post by zuthal on Dec 25, 2017 9:41:20 GMT
The waste heat of a reactor, plus its electrical power output, should equal the thermal power output - P_th=P_el+P_waste. However, it seems that in CoaDE, reactors are instead outputting the thermal power as waste heat - without regards to the fact that quite a bit of that thermal power is being turned into electricity. This 62.5 MW reactor would have, at 22.5% efficiency, a thermal power of 62.5 MW/0.225=278 MW. The waste heat should be 62.5 MW/0.225-62.5 MW=215 MW. This appears to affect all reactors. For example, the stock 13.5 MW reactor, at 13.5 MW electrical power and an efficiency of 21.5%, should have a thermal power of 63.8 MW and a waste heat of 49.3 MW – but it has a waste heat of 63.8 MW. In consequence, the waste heat of all reactors is too high by a factor of 1/(1-η), where η is the reactor's efficiency.
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Post by zuthal on Jul 17, 2017 6:40:41 GMT
Seems to me like you could slow down your turbopump quite a bit - after all, you are only getting chamber temps of 1595 K.
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Post by zuthal on Jul 9, 2017 12:16:32 GMT
argonbalt That strange glowing ball you mentioned might be the explosive from the flakbombs - as an explosion in space would take the form of a spherical ball of initially glowing gas.
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Post by zuthal on Jun 28, 2017 17:19:45 GMT
I can confirm this - on a ship with four reactors outputting ~66 MW each, the displayed engines-off heat output (outside of simulation) is a bit over 1 GW.
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Post by zuthal on Jun 28, 2017 15:22:09 GMT
An enemy gunship is cast in stark light as a brimstone warhead cores its engine section.
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Post by zuthal on Jun 22, 2017 18:03:56 GMT
They would probably deform into ribbons trailing behind the ship under any sort of thrust anyways...
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Post by zuthal on Jun 20, 2017 21:20:22 GMT
Does having kilometer long radiators lower your turning time more than an equivalent mass in the same spot? I would imagine it does but I can't tell from removing them how much as they do weigh a considerable amount You could make a radiator that is the same total area, but wide and short instead of long and thing - thus keeping the same mass, but putting it closer to the CoM, which should lower the moment of inertia.
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Post by zuthal on Jun 20, 2017 20:46:58 GMT
And another reason for not implementing that of course is that there is no real easy way to deduce the reactivity of a material combo just from the basic properties, and explicitly defining it for everything very quickly leads to a combinatorial explosion and becomes impossible.
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Post by zuthal on Jun 20, 2017 10:11:36 GMT
Went looking for one only to be met with empty results so here it be. Just post any screenshot you like, whether blasting some gunships or just sailing calmly through space. For the first order of business, here's a passenger ferry around Triton: -snip- How did you manage to turn off the UI?
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