"V12 Jake- Hittin' Switches" (jbv12)
11/15/2016 at 00:37 • Filed to: None
2
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"V12 Jake- Hittin' Switches" (jbv12)
11/15/2016 at 00:37 • Filed to: None | 2
| 14 |
So one of my passions is WW2 era theory crafting; what if we continued building fighting machines in a simplistic WW2 style but with modern production methods ? My latest pipe dream is a very large battleship intended for long range shore bombardment. My question is would it be possible to get a 4400 lb solid core 18 inch gun round up to 1500 m/s ? Now correct me if I’m wrong but a longer barrel generally equates to a higher velocity, so if we have a 18"/70 cal. that would give us a barrel length of just over 105 feet. I think anything longer that that would be incredibly impractical and prone to incredible wear. Another concept I thought about was the use of multiple propellant charges (sort of like the V3 gun but with just one very large secondary charge just forward of the firing chamber.) Any thoughts at all would be appreciated !
bob and john
> V12 Jake- Hittin' Switches
11/15/2016 at 00:52 |
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anything is possible with enough power.
longer gun = faster bullet + better accuracy.
Biggus Dickus (RevsBro)
> V12 Jake- Hittin' Switches
11/15/2016 at 00:53 |
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Maybe, the Iowa launched 2,700lb projectiles at up to 760 - 820m/s using 16"/50 guns.
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Biggus Dickus (RevsBro)
> bob and john
11/15/2016 at 00:56 |
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At a certain point, a longer barrel becomes more of a hinderance. Hence why you rarely see Rifle barrels greater than 24 inches except in VERY-powerful calibers.
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bob and john
> Biggus Dickus (RevsBro)
11/15/2016 at 01:05 |
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he is talking about slinging a 4400lbs slug at 1500m/s
and 105 foot long barrel.
I’m pretty sure we are WELL into the ‘very powerful’ calibers at this point.
Flyboy is FAA certified insane
> V12 Jake- Hittin' Switches
11/15/2016 at 01:13 |
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Using modern tech and materials on a nuclear powered boat, I think the best use here would be an electromagnetic gauss cannon.
Incredibly high velocities for the projectiles, though I’m unsure if they actually put any Explosives in them or if they’re still “just” a kinetic kill system.
Flynorcal: pilot, offshore sailor, car racer and panty thief
> Flyboy is FAA certified insane
11/15/2016 at 02:47 |
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Speaking of electromagnetic, friction would dissolve the projectile, warp the 130' barrel, and the shock wave from the sonic boom would likely rip it apart as well.
However, if you can levitate the projectile like a magnetic speed train and create enough of a vacuum at the end of the barrel... like a hyperloop....
Oh. My bad. I’m copying from Elon’s work.
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V12 Jake- Hittin' Switches
> Biggus Dickus (RevsBro)
11/15/2016 at 07:42 |
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That where I got she’ll weight from...
random001
> Flynorcal: pilot, offshore sailor, car racer and panty thief
11/15/2016 at 08:56 |
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Nope, that doesn’t happen. You use a sabot carrier, the barrel is open so the concussion wave has minimal to no effect, and both the projectile and barrel survive quite well.
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random001
> Flyboy is FAA certified insane
11/15/2016 at 08:57 |
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Typically kinetic kill. Use the solid fill projectile to withstand the stress of acceleration, and the energy is much more than any amount of explosive you could put in there.
EngineerWithTools
> V12 Jake- Hittin' Switches
11/15/2016 at 11:01 |
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Hmm. There are several ways to look at this...
Disclaimer: I know very little about what happens inside a gun barrel during firing (mental note: I love transient responses, so I should learn). I’m going to assume linearity, which is certainly not perfectly accurate, but will get us in the right ballpark.
Simply speaking, a gun takes stored chemical energy in the gunpowder and converts it into kinetic energy of the projectile, all within the barrel. We’re ignoring rocket-assisted projectiles, which would be a better way to do this.
Iowa Class:
1225 kg at 762 m/s with 660 lbs of propellant. Kinetic energy = 6.3 X 10^8 Joules.
Jake Class:
1995 kg at 1500 m/s. Kinetic energy = 22.44 X 10^8 Joules.
If we assume that the efficiency of energy transfer stays the same, a Jake Class full shot requires (22.44 / 3.56) * 660 lbs = 4160 lbs of propellant. (6.3x Iowa)
Wow, that’s a lot of gunpowder. You’re going to use up a lot of the barrel length just in the charge.
Let’s look at this another way: Pressure acting on the projectile and its acceleration.
I’m going to assume uniform acceleration over the entire barrel length. I’m also ignoring the slug of air we’re shoving out of the barrel ahead of the projectile. We can figure out the necessary acceleration rate and then the necessary pressure acting on the projectile. Peak pressure is certainly WAY higher, but this gives a good feel.
Iowa Class:
1225 kg, 0 to 762 m/s over 20.3m=> 14288 m/s^2 acceleration, which works out to 19,552 PSI acting on the 16" projectile. That’s a reasonable pressure for steel to hold over many cycles.
Jake Class:
1995 kg, 0 to 1500 m/s over 32m => 35156 m/s^2 acceleration, or 62,204 PSI acting on the 18" projectile. While not totally crazy, that pressure can’t be handled by anything short of high strength steel, and then not over infinite cycles. Hoop stress is linear with pressure (all else being equal) so if you stick with steel, assume the Jake Class barrel needs to be 3x as thick as the Iowa’s.
Short answer: Mechanically possible, but extraordinarily challenging. Much much cheaper and easier to build missiles and ships with vertical launch tubes.
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V12 Jake- Hittin' Switches
> EngineerWithTools
11/15/2016 at 11:15 |
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That’s exactly what I was thinking in terms of it not really being worth the effort. In terms of powder management I think if you split that 4100 lbs of powder into 3 chambers you could have a much less bulky breech. Would a titanium/steel alloy or anything like that be higher strength? Also, if we can find a higher strength material then we could explore the possibility of finding a more efficient propellant, or just go with a rocket shell.
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bob and john
> V12 Jake- Hittin' Switches
11/15/2016 at 14:31 |
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keep in mind gun power isnt the only explaosive now. there are much better ways of making stuff go ka-boom.
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V12 Jake- Hittin' Switches
> bob and john
11/15/2016 at 14:39 |
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That figure isn’t for gun powder even, which is the crazy part.
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EngineerWithTools
> V12 Jake- Hittin' Switches
11/15/2016 at 15:40 |
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First, I just noticed that I transposed a few numbers (I didn’t do this in my head, believe it or not)...3.56 X 10^8 Joules for the Iowa... the 6.3X the energy is correct, so the 4100 lbs is correct.
I think that splitting the charge will help with peak pressure, but my numbers are essentially average pressure: They assume that the burning and expanding propellent exactly makes up for the expanding volume behind the projectile as it travels down the barrel. In other words, splitting doesn’t change the average.
High alloy / high strength steel would be a requirement, but high alloy steel gets its strength from both the chemical makeup and the manufacturing process. If you heat or cool a high alloy steel improperly, you can get garbage (note: this is true for a lot of steels, but gets really important in the highly stressed stuff). Anyway, casting / forging a multi-foot thick barrel while maintaining high strength / high alloy steel properties may be beyond feasible. It’s certainly uber-expensive if possible at all. Then you have to machine this monster - and remember, the stronger the material, the more effort it takes to machine.
Yes, different propellents could reduce the total weight of charge necessary, although the energy output needs to stay the same. Also, if you had a propellent that is very fast acting, which I think is what you get in the higher energy booms, the peak pressure will go up, maybe by orders of magnitude, because the chemical energy would all be released before the projectile moves a significant amount. So then the barrel needs to be...10x as thick?
See also: Vicious circle and point of diminishing returns.