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Post by RA2lover on Oct 15, 2016 13:18:32 GMT
Seems like it's all a matter of how much you are willing to heat the barrel.
Ignoring heat gradient losses, firing 1kg of octogen each second and assuming half of its energy goes towards heating the barrel instead of accelerating the projectile or escaping through muzzle blast, heating the barrel to 1000 K needs 50m² of radiator area. rise it to 2000 K, and you only need 3.15m², though i'm not sure how many shots the barrel can last at that temperature. Those temperatures would also require an open bolt to prevent ammunition cookoff.
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Post by nerd1000 on Oct 15, 2016 14:00:42 GMT
A lot of modern aircraft mounted cannons collect the cases and either dump them in a storage bin or return them to the magazine, as it is rather difficult to eject a shell case into mach 2 airflow without it subsequently colliding with the aircraft. I expect any space based warship would do the same- not much point fighting over low Titan orbit if your civilian ships won't be able to use it for 1000 years afterwards. Hmm i guess, it's still a ton of brass to haul around, compared to how simple and effective caseless ammunition would solve the problem. Indeed, though currently there are many unsolved problems with caseless ammo that mostly preclude its use.
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Post by uberdude9001 on Oct 15, 2016 16:42:40 GMT
Hmm i guess, it's still a ton of brass to haul around, compared to how simple and effective caseless ammunition would solve the problem. Indeed, though currently there are many unsolved problems with caseless ammo that mostly preclude its use. Could the cannons in game be firing combustible cased ammunition similar to most modern tank cannons? Like caseless this speeds up reloading because only a small stub that used to be the rear of the casing is left in the chamber after firing.
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Post by argonbalt on Oct 15, 2016 17:36:54 GMT
Indeed, though currently there are many unsolved problems with caseless ammo that mostly preclude its use. Could the cannons in game be firing combustible cased ammunition similar to most modern tank cannons? Like caseless this speeds up reloading because only a small stub that used to be the rear of the casing is left in the chamber after firing. You know, it might just be that as well, it is "technically" a caseless round of sorts, and after all most large scale artillery in real life uses large powder bag+round combinations anyways.
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Kahl'Zun
New Member
King of all cardboard
Posts: 19
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Post by Kahl'Zun on Oct 16, 2016 2:26:06 GMT
one of the problems with caseless ammo in atmosphere is the casing acts as a heat sink pulling some of the heat from the projectile away.
Space causes things to have trouble cooling, so caseless ideas are even worse.
i think the guns fire too fast as they should be rapidly heating up to the point of plasticity.
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Post by captinjoehenry on Oct 16, 2016 2:31:14 GMT
Well there could be an active cooling system not mentioned. Just simply circulating some coolant around the barrel and out into even tiny radiators would probably do the trick. Again I am not sure but it might just be a small enough heat load to be dealt with with in build cooling
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Post by argonbalt on Oct 16, 2016 2:52:01 GMT
one of the problems with caseless ammo in atmosphere is the casing acts as a heat sink pulling some of the heat from the projectile away. Space causes things to have trouble cooling, so caseless ideas are even worse. i think the guns fire too fast as they should be rapidly heating up to the point of plasticity. Cases pull only a fraction of the heat away, a majority of the heat gets dumped into the barrel any ways, so even if you changed to cased you would have heating issues, likewise if you don't dump your casings into space and hold them in a catcher then you have a bag of hot brass. I was thinking about this today, i know in the past things like water jackets existed, i wonder if a gas or water medium could be pumped over or integrated into the barrel to have cooling. I recall a story about i believe a maxim gun(though it may have been a Vickers) firing continuously for seven days straight, needing only the occasional water switch to remain operational. So i believe that the fire rates are not really constrained by heat, more than anything else mechanical breakdown is the most likely retarder of continuous high power/high fire rate machine guns and cannons.
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Post by pokington on Oct 16, 2016 13:41:18 GMT
I was thinking about this today, i know in the past things like water jackets existed, i wonder if a gas or water medium could be pumped over or integrated into the barrel to have cooling. I recall a story about i believe a maxim gun(though it may have been a Vickers) firing continuously for seven days straight, needing only the occasional water switch to remain operational. So i believe that the fire rates are not really constrained by heat, more than anything else mechanical breakdown is the most likely retarder of continuous high power/high fire rate machine guns and cannons. If it was the Vickers, it was twelve hours and a million rounds, but they had to change barrels 100 times. Supposedly. Even water-cooled guns need barrel swaps - the chamber erodes to the point of being unusable after ~10,000 rounds. Air-cooled guns require frequent barrel swaps under sustained use, because they heat up to the point where the barrel deflects and it can even burst. Under a cyclic rate of fire (~600-900 rpm, depends on the gun) you need to change the barrel every minute or more. Space-cooled guns are going to have heating problems (seizing/bursting from thermal expansion) unless the problem is directly addressed.
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Post by argonbalt on Oct 16, 2016 17:48:43 GMT
I don't think anybody is moving for a pure space cooled gun if it starts to get fucky after only a thousand rounds, integrated cooling would be an interesting addition, along with ammo belts, turret construction and more realistic barrel assemblage.
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Post by bdcarrillo on Nov 2, 2016 23:31:37 GMT
I have to agree with the OP on this one. Heating of the barrel via projectile friction could be modelled in game, requiring us to reduce the RoF to a realistic numbeer. Realistic heating of coilguns (based on W) and railguns (friction plus rail W) could be modelled as well.
Mitigation strategies could include burst fire, fluted barrels, and liquid cooling.
Anecdotally, I've put several hundred rounds through a M2 in short bursts, and that thing heats up! Barrel fatigue due to heat at a constant, sustained max rate of fire is a real issue for modern automatic firearms. Those are cooled primarily by convection... I'm not familiar enough with the math to compare air convection to space radiation rates.
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Post by qswitched on Nov 3, 2016 0:02:14 GMT
Barrel heating is actually modeled in game. Barrels are very effectively radiatively cooled. It's very rare, though. I've only ever seen it happen once, when I had conventional cannons blasting for several minutes without stop, they got red hot and the RoF dropped.
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Post by cuddlefish on Nov 3, 2016 1:56:34 GMT
One can confirm this by using nonmetallic barrel compositions on conventional cannon - I fooled around for a bit with plastic weaponry mostly to see how light I could make a gun. They fired quite nicely for a short period before needing to stop to (sloooooooowly) cool off, with the over-temp indicator displayed.
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Post by bdcarrillo on Nov 3, 2016 2:57:22 GMT
Barrel heating is actually modeled in game. Barrels are very effectively radiatively cooled. It's very rare, though. I've only ever seen it happen once, when I had conventional cannons blasting for several minutes without stop, they got red hot and the RoF dropped. I stand corrected then on barrel heat being modelled. Is that function based on the melting temperature of the barrel material, or a lower temperature at which plastic deformation occurs? The other consideration might be autoignition or decomposition temperature for conventional propellants. Obviously current technology utilizes multiple barrels or chambers to maintain a similar RoF, but the as-shown single barrel gun designs do tend to boggle the mind with their cyclic rates.
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Post by argonbalt on Nov 3, 2016 5:21:56 GMT
This is why i was thinking it was a caseless based system, as eliminating that chunk of the firing cycle would speed things up nicely.
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Post by bdcarrillo on Nov 3, 2016 10:58:32 GMT
This is why i was thinking it was a caseless based system, as eliminating that chunk of the firing cycle would speed things up nicely. True, that does eliminate the ejection part of the cycle, but then chamber temperature and autoignition become even more of a concern. Admittedly, the physics may say it's plausible to continuously fire 4,000+ rounds per minute but I still get the sense that it's beyond some practical limit. Loader systems, barrel heat elasticity (since black body radiation at low temperature differences is less efficient), propellent exposure to chamber heat, and so on.
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