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Post by alias72 on Apr 21, 2017 15:36:23 GMT
 Hello. I have designed a ship that I hope is realistic. That said I have a few issues with it. Maybe some members of the community could lend their experience to helping me spot errors (especially with the lasers). A couple of things that I wanted to draw attention to: The engine runs far to hot. I have no idea what a realistic safety margin would be. I haven't added safety margins to any of the structural elements. What would a good safety margin be for a warship? UHMWPE has a ridiculous yield strength. I was hoping it was in line with high performance composites. Otherwise I need to adjust my materials. Also The game does not account for acceleration pressure on the tanks which at 1.65g could be rather large. How much would it cost to establish a synthetic fuel facility on mars? I know that the planet has an overabundance of carbon in the atmosphere so pirating CO2 wouldn't hurt terraforming but could that be reduced into decane and polymers? What would the cost of silicon nitride be for a martian colony? Is vanadium chromium steel a good choice for rocket nozzles or is their a less expensive material that could be processed assuming martian material availability? |
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Post by bigbombr on Apr 21, 2017 16:00:44 GMT
Hello. I have designed a ship that I hope is realistic. That said I have a few issues with it. Maybe some members of the community could lend their experience to helping me spot errors (especially with the lasers). A couple of things that I wanted to draw attention to: The engine runs far to hot. I have no idea what a realistic safety margin would be. I haven't added safety margins to any of the structural elements. What would a good safety margin be for a warship? UHMWPE has a ridiculous yield strength. I was hoping it was in line with high performance composites. Otherwise I need to adjust my materials. Also The game does not account for acceleration pressure on the tanks which at 1.65g could be rather large. How much would it cost to establish a synthetic fuel facility on mars? I know that the planet has an overabundance of carbon in the atmosphere so pirating CO2 wouldn't hurt terraforming but could that be reduced into decane and polymers? What would the cost of silicon nitride be for a martian colony? Is vanadium chromium steel a good choice for rocket nozzles or is their a less expensive material that could be processed assuming martian material availability? The best stock nozzle materials are boron and diamond. I don't know how available they are on Mars, but diamond would require carbon (which, as you stated, is present as CO 2) and a lot of energy (which might make it expensive IRL). If you're willing to use modded but somewhat plausable materials, than nothing beats graphene and 3D-graphene. UHMWPE is strong, but not unrealistically so. I have no idea what good safety margins would be, as some materials start weakening long before their melting point while others still retain virtually all their strength 1 K below their melting point. If you're worried about a meltdown of anything nucleair, you can search for modded materials like graphene U-233 cermet (this actually just mimics U-233 pellets wrapped in a graphene shell, giving it a much higher melting point than U-233 dioxide). |
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Post by bigbombr on Apr 21, 2017 16:02:35 GMT
Also, isn't amorphous carbon better than silicon nitride?
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Post by darthroach on Apr 21, 2017 16:12:47 GMT
1) Engine too hot: the game currently models only melting temperature and constant yield stress for materials as far as I know, so indeed - the effects of temperature on materials are not very accurate. No thermal expansion, no solid state phase transitions, etc. Then again, for most of the materials I don't think it's even possible to obtain this data easily - every mech engineer knows the iron-carbon phase diagram by heart, but for amorphous carbon? Boron Nitride? And so on. At least I think this is the case. Been a long time since I last designed a rocket of my own - stealing forumite designs is so much more efficient  2) Safety margins? What is this, airport tycoon? On a serious note, it depends. Pretty much everything we launch in space is fairly overengineered, particularly anything with people on board. Wartime generally loosens these constraints, but I still doubt anyone would be running gigawatt reactors 0.5k away from meltdown. You'd have to ask actual professionals in each field for what they consider appropriate safety margins. For mechanical stresses, most things are fine in the 1.5-3 range on earth, depending on how much you expect the thing to get knocked around, dropped and abused by 200lb trained gorillas. Space is easier, but I can't say by how much. I wouldn't make anything under 1.25 of max expected load myself. 3) Can we make x chemical thing out of y chemical thing? Short answer - yes, always, since this is a primarily nuclear powered setting, it's always possible from a purely thermodynamic point of view. All you need is the source chemicals and plenty of will to do it. |
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Post by alias72 on Apr 21, 2017 16:24:57 GMT
I haven't been able to find a store that sells amorphous carbon in monolithic sheets. I think this implies that turning it into a macroscopic material is implausibly difficult.
This is also what kills graphene.
UHMWPE has unrealistic values for polyethelyne. I have found macroscopic yield strengths of 40 Mpa but nothing at 3.5 Gpa. This likely comes from the yield strength of a single chain (as used in a composite).
Boron is rare and I wanted to avoid using it outside of nuclear reactors. That said it may be worth using it in the engine. Honestly the engine can afford a smaller thrust to weight ratio. Strapping an extra ton onto it for safety will have a negligible effect on overall performance.
The Cermets are awesome. I haven't found any data on them specifically but all the references to them point to a dream material (at the cost of all your arms and legs).
I know the safety margins for aerospace are 5% on stresses but I have no idea what the military margins would be. Was hoping someone knew the margins for an F 18 or something.
I was also hoping we could come up with the economics of a synthetics industry on mars. Plastic is incredibly useful and mars does have (most) of the precursors for it. It may be more economical to ship the water to mars than mine it from the salt lakes though.
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Post by darthroach on Apr 21, 2017 17:20:17 GMT
There is no way it could ever be more economic to ship water to Mars from earth, than just about any other solution - if that's what you meant. As for asteroids and such, sure.
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Post by alias72 on Apr 21, 2017 17:34:38 GMT
There is no way it could ever be more economic to ship water to Mars from earth, than just about any other solution - if that's what you meant. As for asteroids and such, sure. not from earth. From the belt or some other asteroid. In terms of DV the belt is about as close to Mars as earth but lacks a strong gravity well. |
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Post by newageofpower on Apr 21, 2017 18:39:53 GMT
I haven't been able to find a store that sells amorphous carbon in monolithic sheets. I think this implies that turning it into a macroscopic material is implausibly difficult. This is also what kills graphene. UHMWPE has unrealistic values for polyethelyne. I have found macroscopic yield strengths of 40 Mpa but nothing at 3.5 Gpa. This likely comes from the yield strength of a single chain (as used in a composite). Boron is rare and I wanted to avoid using it outside of nuclear reactors. That said it may be worth using it in the engine. Honestly the engine can afford a smaller thrust to weight ratio. Strapping an extra ton onto it for safety will have a negligible effect on overall performance. The Cermets are awesome. I haven't found any data on them specifically but all the references to them point to a dream material (at the cost of all your arms and legs). I know the safety margins for aerospace are 5% on stresses but I have no idea what the military margins would be. Was hoping someone knew the margins for an F 18 or something. I was also hoping we could come up with the economics of a synthetics industry on mars. Plastic is incredibly useful and mars does have (most) of the precursors for it. It may be more economical to ship the water to mars than mine it from the salt lakes though. Amorphous Carbon (usually marketed as Diamond-Like Carbon) is currently extremely expensive to manufacture in bulk. UHMWPE is trade-named Spectra Fiber. It's in-game physical properties (extreme tensile strength, horrible heat tolerance, low density, high cost) match up with some real-life formulations of Spectra. Ceramics (my favorite being TaHfC) offer interesting properties but are mechanically inferior to alloys as a structural material. |
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Post by alias72 on Apr 21, 2017 18:49:00 GMT
I should probably have mentioned that I am in love with Cermets because they retain some mechanical properties at 3500K.
The amorphous carbon comment justifies my use of silicon nitride (which I can buy in a plate).
Or perhaps you were suggesting metal armour instead of ceramic? I thought Ceramic would be a good balance between lasers and kinetics. Am I wrong?
Spectra fiber. This answers my question about composites. It must be a composite if it's strength is as a fiber. But this is also amazing because it means that those fuel tanks I made are actually plausible (minus the lack of thrust pressure tolerance).
Also TaHfC is such a beautiful ceramic =)
Is molten tin a plausible gas for an arc lamp? and the Ce:LLC. Can I buy that somewhere (its for... medicinal use).
In essence I am trying to re-evaluate the plausibility and cost of my warship because I find it performs quite well and want to see what an even more real version would be capable of.
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