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Post by apophys on Sept 3, 2018 15:22:36 GMT
Also, your comment about molten lithium 6 sounds like you haven't considered how thick said lithium shield would have to be. It takes ~6.87688 cm of liquid lithium to reduce the neutron flux by 50%. Where are you getting this? In CoaDE, it takes 137 micrometers of lithium-6 (solid, but that shouldn't make much difference) to reduce neutron flux of fast neutrons by 50%.
1 cm reduces the neutron flux of fast neutrons passing through by a factor of 1.21*10-22, and thermal neutrons 3.3*10-2. Is this wrong?
Googling tells me that Li-6 and B-10 are commonly used for neutron capture in real life radiation shielding, so I didn't think the performance here was anything out of the ordinary.
If you could tell me how lithium hydride and lithium borohydride perform, that would also be great.
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Post by apophys on Sept 3, 2018 7:13:59 GMT
Cobalt-60 RTGs The unusual length of the craft is due to the 200m space, helping decrease the radiations to the crew module, but it still needs several 1m-thick blocks of lithium-6 to stop the many remaining kilo-Sieverts. Lithium-6 is no more effective than other kinds of mass shielding against gamma (which is what cobalt-60 radiates). You'd do cheaper with the same mass of potassium or selenium, or just more distance (or propellant tanks in the way).
Li-6 is fantastic against fast neutrons, but only that.
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Post by apophys on Sept 3, 2018 2:57:07 GMT
I was talking about in reality and not inside of an unrealistic video game. In reality, we would be able to fully shield reactors with molten lithium-6 (or lithium borohydride using Li-6 and B-10), making mass concerns for neutron shielding largely moot due to its effectiveness.
Gamma radiation produced during normal operation does not transmute elements, so it doesn't contribute to later servicing difficulty. A shadow shield for that is fine, or even just distance.
The servicing issue would be reduced to gamma radiation produced from already-transmuted elements in the inner structure of the core. This to me seems possible to deal with. It doesn't make the servicing equipment radioactive (worst case, you can use robotic arms operated from behind a gamma shadow shield), and the radioactive waste is as little as possible.
Dealing with radioactive waste is much easier in space than on Earth. You can build a reprocessing and storage station in orbit for this purpose, set a dumping location on Luna, or even launch it into the sun.
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Post by apophys on Sept 3, 2018 2:44:04 GMT
Have you considered including a 10 kW radioisotope thermoelectric generator? Or ordinary hydrogen nuclear thermal rockets? A radioisotope thermoelectric generator saves crew in smaller ships, which may lead to overall mass/cost savings. I'm considering a 1 kW & 10 kW RTG for vanilla, but mass/cost savings are unlikely. The main cost-effective RTG pellet, cobalt-60, produces a large amount of gamma radiation, which is very difficult to deal with (at least without abusing the bug that spider silk blocks it all). It would really only apply to unmanned drones, for which reactors are better anyway. Hydrogen is strictly inferior, performance-wise, to hydrogen deuteride for thermal rockets.
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Post by apophys on Sept 3, 2018 1:50:21 GMT
What are the best materials for crew modules, cargo modules, and radiation shields by the way?
I mentioned this in another thread, but the best crew module materials, from lightest to cheapest, are polyethylene, calcium, magnesium, and potassium (potassium needs more than 1 cm thickness; the others don't, for maximally lengthened modules). I typically used to use magnesium, but I'm leaning toward polyethylene now.
Cargo modules are fine with graphite aerogel, so there's no reason not to use that.
Radiation shields for fast neutrons are best made from lithium-6 (this is what you need for shielding from reactors).
Radiation shields for thermal neutrons are best made from a very thin layer of gadolinium-157. Boron is also good, though not quite as good. But there's no relevant source of these, so you can more or less ignore it.
Gamma shielding is best done by propellant tanks and distance. A thick layer of material works, but is very heavy (selenium, zinc, or lead are decent, depending on your available volume). The only relevant sources of gamma are cobalt-60 RTGs, so you can ignore it if you don't have those on a ship (put them on drones only). There is a bug where spider silk blocks all gamma radiation, but I expect that to get fixed eventually, so I'm not going to recommend that. Note: Lithium-6 does nearly nothing for gamma.
Of course, if you need to shield from multiple different types of radiation, layer multiple types of radiation shields. There's no single combo material.
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Post by apophys on Sept 3, 2018 1:15:27 GMT
After casually strolling and scrolling around for a while, I noticed that there are quite a few stuff I could make out of the ideas (if the owners of the idea give me permission to do so). Examples are such as [...] apophys 's 100 GW MPD ship brachistochrone in ToughSF discord server. Possibly a race against time to deliver personnel from Apophys Electrics' headquarter on asteroid Apophis to Earth/Mars or other objects in the inner Solar System. Sounds great to me.
I can make a version that would be compatible with the community material pack, if you like (the version I built uses my standard 50 GW reactors, which have diamond moderator). I should probably change the reactors to not have diamond in the first place, considering how much trouble it causes for some people...
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Post by apophys on Sept 1, 2018 20:59:56 GMT
The lowest density materials are lithium, lithium-6, potassium, polyethylene, and UHMWPE… but would building a tank out of these materials and filling it with methane really work, all things considered? Probably no? Also, what’s the default propellant tank thickness? Dynamic? Because the tanks must be able to hold a certain amount of pressure and if they’re transparent, I guess radiation can affect the contents? All things considered, what’s a good material for containing methane or oxygen? What you need is a high strength to weight ratio, not low density. The tanks need to be pressure-tight. Tank thickness is dynamically modified to be the minimum that holds the pressure. Materials that are not directly outclassed by any other for tanks, from lightest to cheapest, are vanadium chromium steel, diamond, or selenium. The mass increase with selenium isn't ever really worth it, imo.
I use diamond tanks for all fluids with the density of around methane or better.
There is no need to add armor to prop tanks. Your armor should be wrapped around the outside of and in front of the ship, not wasted inside between tanks.
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Post by apophys on Aug 31, 2018 3:15:33 GMT
Indeed, these railguns don't seem realistic, as they are.
However, using a plasma armature (and pushing a payload) might allow similar performance values, since plasma shouldn't have such issues with erosion, spot welding, or the velocity skin effect. It's hard to be sure though, because such things are classified.
Electrically charging bits of metal and accelerating them as in a particle accelerator is a possible and interesting alternative, with which you can certainly get up to and beyond 200 km/s.
Particle accelerators in general would be an excellent addition.
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Post by apophys on Aug 30, 2018 23:09:56 GMT
For lighter crew modules, always have as many decks as possible (i.e. make them long and thin rather than short and fat).
The top choices for materials, in order from lightest to cheapest, are polyethylene, calcium, magnesium, and potassium (potassium needs to be thicker than 1 cm; the others don't).
Boron nitride is an option if you want some natural radiation resistance. Amorphous carbon is an option if you want it to be slightly more damage-resistant.
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Post by apophys on Aug 30, 2018 7:29:03 GMT
Boron fiber is the easy pick for high strength to weight ratio at low ingame cost. This also makes it an excellent kinetic armor material.
If you need it to be pressure-tight, the game won't let you use fibers, making diamond (cheap) or VCS (lightweight for strength) top choices.
If you need it to sustain very high temperature, amorphous carbon is best.
Combining structural material with lasing resistance is not a good idea, since the decent choices (more or less just aramid fiber) are very expensive for useful amounts.
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Post by apophys on Aug 30, 2018 5:55:24 GMT
Composite armor is a science, you random mix of materials is rather sub-par, stuffed whipple shields with inner bulkheads and spall liners are better, I can get 5g @5km/2 in ten megawatts of power and 1-2 tons of mass, at max RoF My coilguns can throw 5kg rounds at nearly 10km/s and will shread 19cm of Beta Titanium, much stronger then A-Carbon, they also fire 5 rounds per a second You conspicuously omitted your coilgun's power reqs. 5 kg at 10 km/s every 0.2 sec is 1.25 GW. Even assuming 50% efficiency, that's only 2.5 GW draw. More concerning is the cost of what must be 5 kg of expensive magnetic metal glass every shot.
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Post by apophys on Aug 30, 2018 5:01:47 GMT
From my fiddling with railguns, I get a rough relation that 2x projectile energy --> ~2.5x mass & cost of the gun (with much less traverse speed to boot). This is exponential; i.e. 4x projectile energy --> ~6.25x mass & cost, and so on.
Therefore, it is most mass-efficient and cost-efficient to use low energy bullets. High projectile velocity is the #1 concern, in order to have maximum range and actually hit things. The only other thing you can change to have low projectile energy is to reduce the mass as much as possible. Thus, sandblasters.
Cranking up their rate of fire as much as possible is just a matter of having sufficient power generation to hit the 30 shot/sec hardcap (or the 1 GW power input limit, whichever you reach first).
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Post by apophys on Aug 27, 2018 2:38:56 GMT
Welcome! I'm not knowledgeable in D&D, though there should be people here who are. What would the capacity to regenerate reaction mass en route do to spaceships? Being able to refuel continuously would make exhaust velocity much less of a concern, so yes, I'd expect thermal rockets to be the norm. Nuclear thermal would compete with solar thermal, and possibly with some magic that you can use for creation of heat (fire? lightning?). You'd be able to do brachistochrone transfers at a high average acceleration, making travel to the outer system very easy, and making interstellar travel much simpler. Needless to say, the violation of mass-energy conservation would change a lot of aspects of civilization back on Earth.
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Post by apophys on Aug 25, 2018 23:18:28 GMT
By the way, why do you use polytetrafluoroethylene over polyethylene for your armor? Because this was made before polyethylene got buffed; back then, the top choice was either rubber (more expensive) or PTFE (more massive). I haven't updated to take the PE buff into account yet.
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Post by apophys on Aug 25, 2018 20:31:45 GMT
How do you fit all the lasers at the front without increasing the armor cost? I tend not to use armor.
This has been used as a standard testing laserstar ever since it won last year's forum tournament. In this case, the only armor not on the laser turrets themselves is a wide PTFE rad shield right behind the lasers. Code: (some modules are duplicated with my standard modules, so everything was renamed with a 2 just in case) ExplosiveModule [AE] 150 mg 1 cm Flak 2 Description Version 2. By Apophys. UsesCustomName true Length_m 0.01 ExplosiveMass_kg 0.0001 ExplosiveComposition Nitrocellulose ShrapnelMass_kg 5e-005 ShrapnelComposition Osmium Detonator HardRange_km 0.005 ActivationRange_km 0.175 MinimumRange_km 0 OverrideTimer_s 0 TargetsShips true TargetsShots true
RadiationShieldModule [AE] 3 mm 2 mg AC Shell Cap 2 Description Version 2. By Apophys. UsesCustomName true Composition Amorphous Carbon Dimensions_m 0.0015 0.000135
MagnetoplasmadynamicThrusterModule [AE] 1 GW Neon MPD 2 Description Version 2. By Apophys. UsesCustomName true CathodeRadius_m 0.0252 ChamberThickness_m 0.01 AnodeThickness_m 0.001 ThrusterLength_m 0.0156 CathodeComposition Potassium AnodeComposition Depleted Uranium InsulatorComposition Polyethylene Propellant Neon Current_A 1.43e+005 Injector Composition Lithium PumpRadius_m 0.07 RotationalSpeed_RPM 8.23 Gimbal InnerRadius_m 0.1 ArmorComposition Polytetrafluoroethylene ArmorThickness_m 0.005 MomentumWheels Composition Amorphous Zirconium Steel RotationalSpeed_RPM 94000 GimbalAngle_degrees 90
ThermoelectricFissionReactorModule [AE] 1.01 GW Reactor 2 Description Version 6. By Apophys. UsesCustomName true ReactorCoreDimensions_m 0.14 0.276 NuclearReactor Coolant Sodium Moderator Diamond ModeratorMass_kg 20 Fuel U-233 Dioxide FuelMass_kg 8.82 FuelEnrichment_Percent 0.97 ControlRodComposition Hafnium Carbide ControlRodMass_kg 133 NeutronReflector Diamond ReflectorThickness_m 0 AverageNeutronFlux__m2_s 2.2e+020 InnerTurbopump Composition Amorphous Carbon PumpRadius_m 0.69 RotationalSpeed_RPM 479 ThermocoupleInnerDimensions_m 3 8.7 Thermocouple PTypeComposition Osmium NTypeComposition Tungsten Length_m 0.001 ThermocoupleExitTemperature_K 2500 OuterCoolant Sodium OuterTurbopump Composition Selenium PumpRadius_m 0.59 RotationalSpeed_RPM 504
LaserModule [AE] 100 MW Nd-YAG 1 Mm Laser 2 Description Version 3. By Apophys. UsesCustomName true ArcLamp GasComposition Krypton EnvelopeComposition Diamond PowerSupplied_W 1e+008 Radius_m 0.001 CavityWallComposition Gold CavityCoolantComposition Hydrogen CavitySemimajorAxis_m 0.2 CavitySemiminorAxis_m 0.198 GainMedium Nd:YAG OpticalNodes 3000000 LasingRodRadius_m 0.0025 Mirror Composition Copper OutputCoupler Composition Fused Quartz CoolantTurbopump Composition Silicon PumpRadius_m 0.33 RotationalSpeed_RPM 119 CoolantInletTemperature_K 1000 FrequencyDoubler NonlinearOptic Composition Silver Gallium Selenide OpticLength_m 0.024 OpticRadius_m 0.01 SecondFrequencyDoubler NonlinearOptic Composition Silver Gallium Selenide OpticLength_m 0.012 OpticRadius_m 0.01 ApertureRadius_m 2.39 FocusingMirror Composition Aluminum Unmounted false Turret InnerRadius_m 5.07 Extruded false ArmorComposition Polytetrafluoroethylene ArmorThickness_m 0.002 MomentumWheels Composition Amorphous Zirconium Steel RotationalSpeed_RPM 1860 EngagementRange_km 1000 TargetsShips true TargetsShots true
PropellantTankModule [AE] 10 t Neon Tank 2 Description Version 2. By Apophys. UsesCustomName true Propellant Neon StructureComposition Selenium ReactionMass_kg 10000 HeightToRadiusRatio 15 AdditionalArmorThickness_m 0
RadiatorModule [AE] 0.45 GW Silicon Laser Radiator 2 Description Version 2. By Apophys. UsesCustomName true Composition Silicon PanelWidth_m 5 Height_m 14.8 Thickness_m 0.001 ArmorThickness_m 0.001 Panels 20 FrontTaper_radians 0 BackTaper_radians 0 SurfaceFinish Diamond
RadiatorModule [AE] 0.5 GW BN Reactor Radiator 2 Description Version 2. By Apophys. UsesCustomName true Composition Boron Nitride PanelWidth_m 5 Height_m 7.3 Thickness_m 0.001 ArmorThickness_m 0.001 Panels 20 FrontTaper_radians 0 BackTaper_radians 0 SurfaceFinish Diamond
CrewModule [AE] 51 Crew Module 2 UsesCustomName true CrewCapacity 51 Decks 17 StructureMaterial Magnesium ShellThickness_m 0.01
RadiatorModule [AE] 1.5 x 8 Silicon Radiator 2 UsesCustomName true Composition Silicon PanelWidth_m 0.75 Height_m 8 Thickness_m 0.001 ArmorThickness_m 0.001 Panels 2 FrontTaper_radians 0 BackTaper_radians 0 SurfaceFinish Diamond
RadiationShieldModule [AE] 5 m Diameter 1 cm Li-6 2 Description Version 1. By Apophys. UsesCustomName true Composition Lithium-6 Dimensions_m 2.5 0.01
RadiationShieldModule [AE] 18 m Diameter 5 cm PTFE 2 UsesCustomName true Composition Polytetrafluoroethylene Dimensions_m 9 0.05
CraftBlueprint [AE] 152 mg 1 cm Flak 2 Description Version 2. By Apophys. Modules [AE] 150 mg 1 cm Flak 2 1 0 null 0 [AE] 3 mm 2 mg AC Shell Cap 2 1 0.5 null 0 Armor
RailgunModule [AE] 100 MW 50 km-s 152 mg Flak Railgun 2 Description Version 3. By Apophys. UsesCustomName true PowerConsumption_W 1e+008 Capacitor Count 1 DielectricComposition Biaxially Oriented Polypropylene Dimensions_m 1 0.649 Separation_m 1.2e-006 Rails Composition Zirconium Copper Thickness_m 0.0604 Length_m 3.43 BarrelArmor Composition Graphite Aerogel Thickness_m 0.585 Armature Composition Osmium BoreRadius_m 0.00445 Mass_kg 0.001 Tracer null Payload [AE] 152 mg 1 cm Flak 2 Loader PowerConsumption_W 37000 ExternalMount false InternalMount false Turret InnerRadius_m 0.921 Extruded false ArmorComposition Polytetrafluoroethylene ArmorThickness_m 0.003 MomentumWheels Composition Diamond RotationalSpeed_RPM 11000 TargetsShips true TargetsShots true
AmmoModule [AE] 5000x 152 mg 1 cm Flak [1] 2 Description Version 1. By Apophys. UsesCustomName true SuppliedModule [AE] 100 MW 50 km-s 152 mg Flak Railgun 2 AmmoBay Capacity 5000 Stacks 2 ArmorComposition Silica Aerogel ArmorThickness_m 0.001
CraftBlueprint [AE] 2GW Deep Fryer 2 Description Version 3. By Apophys. Modules [AE] 1 GW Neon MPD 2 2 0 null 0 [AE] 1.01 GW Reactor 2 1 0.4375 null 0 [AE] 100 MW Nd-YAG 1 Mm Laser 2 18 82.821 null 0 [AE] 10 t Neon Tank 2 9 -0.86597 null 0 [AE] 0.45 GW Silicon Laser Radiator 2 2 61.266 [AE] 100 MW Nd-YAG 1 Mm Laser 2 0 [AE] 0.5 GW BN Reactor Radiator 2 2 27.892 [AE] 1.01 GW Reactor 2 0 [AE] 51 Crew Module 2 1 -0.64258 null 0 [AE] 1.5 x 8 Silicon Radiator 2 4 4.7688 [AE] 51 Crew Module 2 0 [AE] 100 MW 50 km-s 152 mg Flak Railgun 2 2 79.113 null 0 [AE] 5000x 152 mg 1 cm Flak [1] 2 12 5.5784 null 0 [AE] 1.01 GW Reactor 2 1 1.4375 null 0 [AE] 0.5 GW BN Reactor Radiator 2 2 50.185 [AE] 1.01 GW Reactor 2 0 [AE] 5 m Diameter 1 cm Li-6 2 1 -0.10254 null 0 [AE] 0.45 GW Silicon Laser Radiator 2 2 39.044 [AE] 100 MW Nd-YAG 1 Mm Laser 2 0 [AE] 18 m Diameter 5 cm PTFE 2 1 66.763 null 0 Default Remote Control 1 9.7194 null 0 Armor
I might update the design to reflect design choices possible in the recent patches, specifically I may add concave armor. But it still works fine as it is; surprisingly, nothing broke since it was made.
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