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Post by blothorn on Sept 29, 2016 7:55:16 GMT
I decided to get some actual data on missile armor---made a space station with a 100MW laser and timed how long it took to destroy groups of five of my standard frag missile with different armoring options (all the same mass, +/- 0.2kg). For consistency, I made all interceptions at 100m/s (+/- 5m/s) and started the time when the station began firing (as different geometries had notably different times for the initial turret traverse). Most groups are the average of 3 rounds like that, to attempt to smooth over remaining variances. Armor | Average time (s) | Notes | 5mm amorphous carbon | 31 | My expected winner, at least for "homogenous" armor. | 3mm diamond | 6 | Conductivity does not win you much without good specific heat... | 4.7mm graphite | 45 | Still puzzled why this beats amorphous carbon, which seems to have better stats. | 5mm boron | 26 | My standard bulk kinetic armor; included to see how much it gives up to the carbon-based armors. | 6mm reinforced carbon-carbon | 8 | This might explain the comments about lasers being overpowered vs. stock ships... | 4mm amorphous carbon, 2.7cm graphite aerogel | 32 | The logic is that the aerogel can act as a thermal transfer layer for the amorphous, but it is hampered by the low melting point of the aerogel. Not worth the (considerable) bulk. | 1.9mm diamond, 1.9mm amorphous carbon | 29 | Tries to use amorphous carbon as a heat-sink for the conductive diamond. I am surprised how close this was to homogenous amorphous carbon, given the poor performance of diamond. | 0.8mm basalt fiber, 4mm amorphous carbon | 143(!) | I meant to put the basalt on the inside, to see if insulating the inside components from the armor helps. Putting the basalt on the outside is the best mistake I have made in a while... | 4mm amorphous carbon, 0.8mm basalt fiber | 39 | So much for my initial theory---the performance advantage here is more than explained by the superiority of basalt fiber. | 3.9mm basalt fiber | 223(!) | All five missiles passed the target and were destroyed by fire to their unprotected rear. |
The spectacular results for basalt fiber were surprising---it has a mediocre melting point and specific heat capacity, and one of the lowest thermal conductivities of a solid. I am not entirely certain what is happening, but the results are convincing (if you can stomach the price tag). The big caveat here is that these are thin layers of armor on small targets, and I expect that to work very differently from thicker armor. OTOH, I do not see lasers as very viable in capship fights except for module sniping; I should attempt an experiment on turret armor. (Even if they are the king of close-range combat, as claimed, I have never seen a capital survive trying to close the range that far.) Drones are harder to generalize about, since they are usually killed by weapon/radiator damage, not armor penetration, and options there vary heavily by class.
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Post by mavericksawyer on Sept 29, 2016 8:13:27 GMT
Tinker with some of the stock designs and see what happens?
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Post by 314159 on Sept 29, 2016 9:25:14 GMT
I should attempt an experiment on turret armor. (Even if they are the king of close-range combat, as claimed, I have never seen a capital survive trying to close the range that far.) Drones are harder to generalize about, since they are usually killed by weapon/radiator damage, not armor penetration, and options there vary heavily by class. Seconded. With my current drone design, the turret is the one component which is knocked out very quickly, even when I armour it with 5cm of amorphous carbon (no basalt fibre available for turret armour). Increasing that time would significantly increase their utility.
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Post by quarkster on Sept 29, 2016 11:56:51 GMT
Regarding the basalt fiber, the fact that it's fibrous makes it more resistant to damage from thermal stresses. The idea with lasers is to heats a small spot so much that it vaporizes and the expanding vapor takes chunks of unvaporized material with it.
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acatalepsy
Junior Member
Not Currently In Space
Posts: 97
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Post by acatalepsy on Sept 29, 2016 14:29:42 GMT
What about spider silk? I've been meaning to do some armor testing with that against kinetics and lasers, and the result of the fiber against lasers is encouraging.
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Post by RA2lover on Sept 29, 2016 14:55:11 GMT
What's the efficiency of the laser? Can you replicate the same results with different laser wavelengths? how much does M² affect the results?
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Post by blothorn on Sept 30, 2016 9:22:28 GMT
Several more tests: 7.9mm spider silk averaged 5 seconds, 7.2mm aramid fiber 208, 1cm UHMPWE 48, 6.9cm silica aerogel 238. The aramid fiber and silica gel both got all missiles past the target, roughly equalling the performance of basalt fiber. Distinguishing among those three will take a more difficult test. (Note that times in this test are a roughly log scale of effectiveness: spider silk-armored missiles died in a second apiece to a 350MW/m^2 beam at 30km; the missiles that passed the target survived a 20GW/m^2 beam at less than 3km). The terrible performance of spider silk seems to disprove the theory that being fibrous is advantageous. Note, however, that spider silk has a fairly good thermal conductivity while aramid fiber has one of the lowest of a solid material (comparable to basalt fiber) and silica aerogel the absolute lowest. Similarly, UHMPWE performs on a level with carbon materials with much higher melting points and has ~10x lower thermal conductivity than graphite/amorphous carbon. This seems a fairly decisive argument that low thermal conductivity is a huge advantage. What to look at next? There are a bunch of ceramics with low conductivity, but all have poor tensile strengths and I would be concerned about their not pulling their weight against kinetics (although that is where I would look for projectile armor, as they are much less likely to see kinetic impacts, and using the expensive fibres seems wasteful). Several fibers combine superb tensile strengths and low conductivities, but all are ruinously expensive and cannot be mounted on turrets. It would be nice to have comparable data for kinetics; the "Raw Steel" made it sound as if the ultimate tensile strength was about the only thing that matters, but if the high shear moduli of the ceramics make them respectable armor (which I think they should be) they bear more investigation. I also definitely want to test capship scales (centimeter thicknesses and larger surface areas). It would also be interesting to play things out at longer ranges; I suspect few things other than missiles will want to come within 30km of a 100MW laser, and it may be that a lot of the mid-range materials are perfectly adequate at lower intensities (where conductance and re-radiation can offset a much greater portion of incoming heat). Here is the laser. Intensity at the starting range (just beyond 30km) is around 350MW/m^2. I welcome any attempts at replication with other colors.
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tuna
New Member
Posts: 33
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Post by tuna on Sept 30, 2016 10:03:06 GMT
I felt like finding one good material wasn't good enough, so I wanted to test materials similar to it in some ways to find what is it that makes it good. My tests were done with a heavy missile, 100m/s intercepts, facing one active 100MW laser. 2mm basalt fiber | 37s, 42s, 38s | baseline, repeatability tests
| 4.3mm spider silk | ~0s
| This one popped instantly. I had to verify that there in fact was armor. | 1.9mm ceramic oxide fiber | 17s
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| 4mm liquid crystal polymer fiber | 5s
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| 4mm aramid | >65s | one missile got through
| 4mm para-aramid | 2s
| This result I liked, as para-aramid is very similar to aramid, with one major difference. It mas massively better thermal conductivity. |
After this I went straight to the best thermal insulator in the game. This stuff: 56mm silica aerogel | >65s | all missiles got through | 28mm silica aerogel | >65s | all missiles got through | 14mm silica aerogel | >65s | 4 missiles got through | 10mm silica aerogel | >65s | 1 missile got through | 4mm silica aerogel | 41s |
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Silica aerogel is not just a little bit better than everything else, it is by weight ~15 times better than basalt fiber. A layer that will easily protect against most targets is very cheap and light. I see little point in armoring missiles with anything else, and a 20-mm layer makes any missile pretty much laser-proof, except against ridiculous amounts of lasing power. It seems we got it all wrong, what you want is a thermal insulator. I do question it's physical ability to defend against lasers in real life on the basis that lasers can pretty much shine through it. (edit: it seems we ran our tests simultaneously)
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Post by jonatanhedborg on Sept 30, 2016 14:22:10 GMT
Did anyone try graphite aerogel? Cheaper, lighter and has better heat-related stats (I think). Though it has pretty (very?) high thermal conductivity, maybe that will screw it over.
EDIT: Yeah graphite aerogel was awful. Died almost instantly, whereas they couldn't even touch the silica ones. Rushed 4 solar lances with 20 modified striker nukes as a test.
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Post by qswitched on Sept 30, 2016 18:13:41 GMT
A note on thermal conductivity.
Having a high or a low conductivity is better against lasers in various cases. If the laser is slow to burn through your hull (i.e. low irradiance caused by low focus, long range, or low power), having a high conductivity is beneficial. This is because the armor can radiate the heat away to nearby armor tiles and keep from ablating effectively.
Now consider a laser with a high irradiance. If it has a high enough irradiance, it will ablate your armor whether you want it to or not, so a low conductivity is better, because it keeps the heat from penetrating very far through the material. In other words, it prevents the heat from spreading, so the laser, no matter how high power, can only boil away surface layers at a time.
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acatalepsy
Junior Member
Not Currently In Space
Posts: 97
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Post by acatalepsy on Sept 30, 2016 18:22:44 GMT
Now consider a laser with a high irradiance. If it has a high enough irradiance, it will ablate your armor whether you want it to or not, so a low conductivity is better, because it keeps the heat from penetrating very far through the material. In other words, it prevents the heat from spreading, so the laser, no matter how high power, can only boil away surface layers at a time. It seems likely that, with the high powered reactors floating around, very low conductivity is the way to go, especially since we're also seeing powerful railguns and coilguns - and small, efficient NTRs for high velocity missiles - that make it necessary to survive being lased for only a few seconds before detonation. Or maybe a conductive outer layer and an insulating under layer?
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Post by jonatanhedborg on Sept 30, 2016 19:29:37 GMT
As it stands now with silica aerogel it would be very useful indeed to be able to put it as a layer on turrets
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Post by blothorn on Sept 30, 2016 19:35:35 GMT
A note on thermal conductivity. Having a high or a low conductivity is better against lasers in various cases. If the laser is slow to burn through your hull (i.e. low irradiance caused by low focus, long range, or low power), having a high conductivity is beneficial. This is because the armor can radiate the heat away to nearby armor tiles and keep from ablating effectively. Now consider a laser with a high irradiance. If it has a high enough irradiance, it will ablate your armor whether you want it to or not, so a low conductivity is better, because it keeps the heat from penetrating very far through the material. In other words, it prevents the heat from spreading, so the laser, no matter how high power, can only boil away surface layers at a time. Yes---this is a very powerful laser relative to the size of the targets, which definitely biases things in favor of the low-conductivity armor. However, my thinking is that you generally want to minimax defenses: a strength does not compensate for a vulnerability. I think that in most situations, I would trade increased damage from underpowered lasers (that are not going to kill me anytime soon, regardless) for a bit more time against a more powerful laser. Missiles, as noted, only have to survive seconds anyway. For a capship, being able to take weaker fire without taking permanent damage sounds a lot more attractive, but CDE combat is fast and brutal. If the armor buys me a minute or two of life, I shall not complain much about its state afterward. Interestingly, I tried somewhat the conductive+non-conductive composite; putting basalt outside the carbon was decisively superior than the other way around. My theory is that while the carbon was intact, it was spreading the heat across the surface of the basalt. Since the carbon has a higher melting point than the basalt, this increases the surface area of basalt being heated, allowing much more efficient transfer of heat to the basalt. To get conductive-over-nonconductive armor to work, I think you want the melting point of the nonconductive layer to be well above that of the conductive layer, in the hope that in the face of a powerful beam the conductive layer will ablate away before it has much chance to damage the nonconductive layer. Unfortunately, you really want a high melting point in conductive armor, and I cannot think of a good nonconductive armor with a high melting point: the only materials with conductivity below 20 W/m^2 and melting points above 3000K are relatively dense metals with fairly unattractive profiles otherwise. This does mean that you probably do not need to worry about putting a low-melting-point, high-conductivity ballistic armor over a medium-melting-point nonconductive thermal armor (e.g. spider silk over basalt), but do not expect the outer armor to do much other than get out of the way against a laser. Nonconductive over conductive is silly from a thermal perspective---you only take advantage of the strength of conductive armor against weak lasers after they have burned through the nonconductive armor, and then the nonconductive outer layer will prevent the conductive layer from radiating heat outward. Nonetheless, I suspect it is the way to go if you want to combine a weak nonconductive thermal armor with a high-melting-point conductive material that is stronger against kinetics. (Although then you need to worry about the nonconductive material impairing the anti-kinetic ability of the interior layer; I suspect that in some cases it would help stabilize projectiles that would shatter or ricochet, similarly to the soft AP caps on old naval projectiles.)
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Post by aetreus on Sept 30, 2016 21:56:58 GMT
I think that for a capital ship's exterior modules, you want a conductive armor. Lasers typically hold on target for several seconds to kill a turret, so being able to radiate the heat away is probably more effective than ablating. Modules can only have one armor layer as well, so you need it to be resistant to kinetic as well, and the material selection for ultra low thermal conductivity isn't too good for that.
Impact resistance is probably going to be very variable depending on the type of round and velocity involved. The ultra-high velocity railguns and coilguns that some player ships use have much more in common with the jet from a shaped charge warhead than anything else. Look for materials with very high sheer and bulk modulus, stuff like corundum/sapphire. Lower velocities probably benefit more from higher tensile yield materials, though I think this applies to a degree at high velocities as well.
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Post by blothorn on Sept 30, 2016 22:44:57 GMT
Keep in mind that in this case, ablating 4mm of basalt fiber took a reasonably efficient 100MW laser about a minute at ranges below 30km (and most of my kills on the nonconductive armor missiles never breached the armor; they waited until the missile had past and shot through the opening for the engine). It is not that conductive armor is pointless in concept, but that the actual balance means that when intensities are low enough for conductive armor to work effectively, the same weight of nonconductive armor will likely last an entire battle. The one catch is that a barrel is going to be the weakest link, and conductive armor might help sink heat from it.
That said, I agree about the poor options for turrets that combine low conductivity with kinetic resistance. (A lot of the fibers look great--basalt, para-aramid, and ceramic oxide, at the least--but for some reason you cannot use them on turrets.) I think the best bets are probably ceramics and some of the low-conductivity metals. Being able to put composite armor on turrets would be nice...
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