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Post by zuthal on Nov 8, 2016 12:09:42 GMT
Since subunit did a reality check on 5.56 mm NATO small-arms ammunition - and this check was thoroughly failed - I thought I would do one on what is likely one of the best and most famous naval guns of all time: The 16" (406 mm) fifty caliber guns of the Iowa-class battleship. All data on the gun taken from Navweaps. The 16"/50 has a caliber of 406 mm (exactly reproduced in-game), and a barrel length of 20.32 m (approximated as 20.3 m in game). The Mark 8 APC shell has a total mass of 1225 kg (approximated as 1230 kg), and a propellant charge of 297.1 kg D839 (approximated as 297 kg and assumed to be nitrocellulose). The material assumed for the projectile and barrel is vanadium-chromium steel. At the specified working pressure of ~255 MPa, a grain radius of 8.2 mm was needed, yielding a muzzle velocity of 728 m/s - compared to a historical muzzle velocity of 762 m/s. In order to make it work, the barrel needed to be of a thickness of 42 cm, giving the whole gun a weight of 256 t, compared with 121.5 t for the real gun. Conclusion: Conventional cannons underperform compared to their real-life counterparts, and are significantly heavier than them as well.  |
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Post by nerd1000 on Nov 8, 2016 12:15:43 GMT
The real cannon appears to have a tapered outer radius on the barrel- I don't think CoaDE models this, instead it has the gun barrel the same thickness over the entire length. That might explain the increased weight.
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Post by zuthal on Nov 8, 2016 15:00:32 GMT
Quite possible - visual inspection of one of the photos on the Navweaps site suggests that the combined thickness of liner, A tube, jacket and hoop is roughly equal to the bore diameter. That is then only one more reason to have tapered barrels!
That still doesn't explain the missing 54 m/s of muzzle velocity, though - a gun in a vacuum should have a higher muzzle velocity, as the pressure differential across the projectile is greater by 1 atm and there is no air resistance.
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Post by subunit on Nov 8, 2016 18:32:05 GMT
Would a shell made of, say, zirconium copper and with a payload consisting of a barrel of whatever the TNT load of the shell should be, survive the propellant detonation?
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Post by zuthal on Nov 8, 2016 18:49:48 GMT
Well, the bursting charge of the Mark 8 shell is 18.55 kg. I actually cannot fit the full mass of the shell into an explosive payload, so I am using a 1000 kg payload, and an additional 205.5 kg shell in the cannon "under" it. And that will work with any "shell" material that has a tensile strength of at least 256 MPa.
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Post by subunit on Nov 8, 2016 18:58:02 GMT
Well, the bursting charge of the Mark 8 shell is 18.55 kg. I actually cannot fit the full mass of the shell into an explosive payload, so I am using a 1000 kg payload, and an additional 205.5 kg shell in the cannon "under" it. And that will work with any "shell" material that has a tensile strength of at least 256 MPa. In general I think the system works OK- the fact that you got a weapon thats pretty close to the earthbound equivalent means the sim is working pretty well. I think with some tweaking to the payload stuff, maybe editable slug composition (m855 green tip has tungsten penetrators, necessary for my AR drones  ), barrel friction and other things added in, things would be pretty close to perfect. I am a little surprised that simulated earthbound guns tend to be worse than their real equivalents given no air resistance and what seems to be no barrel friction. I think the problem might be nitrocellulose propellants? I don't know. |
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Post by zuthal on Nov 8, 2016 19:18:37 GMT
That is a possible cause - I do not know what the D839 powder they use is actually made of, but I think it is roughly nitrocellulose. And you can sort of simulate different compositions by making the round a "payload" made up of different armour and "radiation shields" - but then you of course don't get the pretty tracers.
And I don't think barrel friction would have such a great effect here, since afaik the gun we use are smoothbore - there is no need to spin the projectile in a vacuum! The one big problem is the turret. A turret that can get it to turn at an acceptable rate consumes 10 GW and increases the mass by something like six times.
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Post by qswitched on Nov 8, 2016 19:19:13 GMT
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Post by zuthal on Nov 8, 2016 19:22:02 GMT
That would allow them, yes, since the real-life propellant is something like 5 cm by 10 cm high cylinders, with several perforations.
Also, could we get tapered barrels? Because those would I think significantly help to reduce the mass of such weapons. Also nice would be mechanically actuated turrets, like on actual tanks and battleships, so that we don't have to spend multiple GW on reaction wheels, though that would likely be a lot more difficult to implement.
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Post by subunit on Nov 8, 2016 19:22:39 GMT
That would explain things . Thanks for making this thing, which will inevitably destroy my marriage, by the way |
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Post by Dhan on Nov 8, 2016 21:22:29 GMT
And you can sort of simulate different compositions by making the round a "payload" made up of different armour and "radiation shields" - but then you of course don't get the pretty tracers. |
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Post by dragonkid11 on Nov 9, 2016 7:35:22 GMT
Flare will cause the round to disappear after the burning time is finished though.
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Post by someusername6 on Nov 9, 2016 7:40:45 GMT
Flare will cause the round to disappear after the burning time is finished though. This one should give enough time for the projectile to reach its target: |
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Post by dragonkid11 on Nov 9, 2016 8:10:59 GMT
Well nevermind then.
Though anyone have issue with too many flare causing the game to not produce any sounds at all?
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Post by leerooooooy on Nov 9, 2016 10:00:05 GMT
Conclusion: Conventional cannons underperform compared to their real-life counterparts, and are significantly heavier than them as well. I disagree, real life designs underperform but high speed, high firerate monsters like this  are more than competitive |
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), barrel friction and other things added in, things would be pretty close to perfect. I am a little surprised that simulated earthbound guns tend to be worse than their real equivalents given no air resistance and what seems to be no barrel friction. I think the problem might be nitrocellulose propellants? I don't know.
