Posted on 04/07/2013 12:05:19 PM PDT by neverdem
And I'll repeat the same question as I did above:
How does a 16" gun launching a projectile with up to 2,700 lbs of high explosive really compare to a 40 lb non-explosive shell at Mach 7, assuming that it maintains that speed upon reaching the target?
Until you answer that question, you cannot compare the recoil -- because you are comparing apples to oranges.
Why is it so hard for you folks to understand the question?
I an just picture the NJ lobbing these shells into Iran or Afghanistan..
Oh, give me a break. You just don't understand the physics. Let me try to express the question in a way that you can comprehend.
At some point, we will presumably be able to build a railgun that generates the same recoil as as 16" gun like one on the USS Iowa. And if we can sufficiently power them on one platform, we could fire 9 of them at one time. The USS Iowa was able to handle that, and it would be able to handle it.
But, those 9 guns on the Iowa launched up to 24,000 lbs of high explosive onto the target. While the kinetic energy delivered to the target is presumably substantial, it's only a small fraction of the energy delivered by the resulting explosive blast wave.
The question is: how would this explosive energy from the USS Iowa's guns compare to the kinetic energy of non-explosive rounds delivered by the railguns? Remember, all of the railgun's energy must be generated by the launcher(s). And that kinetic energy generates an equal amount of recoil.
There is at least one other variable here: the acceleration of the projectile at the launcher occurs over the length of the barrel, while the deceleration at the target will presumably be over a much shorter distance. That changes how the energy is dispersed, and what damage is done to the target. And, you would have to account for how the explosive energy of the conventional shell is distributed.
I'm not pretending to have the answer to these questions. But, the answer is certainly not "the recoil is roughly the same". You can't make that assertion by comparing two completely different outcomes.
Agreed. There are a number of considerations that have to be accounted for when making the comparison. The fact that the railgun shells are inert is a huge advantage: transport, storage, handling, etc. much easier.
But, when someone says "recoil is no problem", they don't understand the question. In order for a projectile to do significant damage with kinetic energy alone, it has to be accelerated. And that is going to generate an equal push in the opposite direction.
However, the acceleration and impact have different characteristics. It's why you can shoot a rifle without (permanently) hurting your shoulder, but do significant damage to the target. It's all about where the energy is expended.
Maybe the problem is you don’t know the definition of the word “recoil”?
You seem to think it means the same thing as “impact”.
Oh, also a 2700 lb armor piercing shell does not contain 2700 lbs of explosive. It has a 41, that’s not a typo, 41 lb explosive charge.
The kinetic energy of recoil and impact will be the same, after subtracting out the velocity lost due to parasitic drag. That's a law of physics that you can't change.
I've already noted the difference the rate of acceleration at the launcher and the rate of deceleration at the target. There's also the question of how the force at the launcher is distributed, vs. the relatively small impact area at the target (I alluded to it in my rifle shoulder vs. target analogy).
But, could you stop hand waving these things away and actually quantify these differences? I'm asking how explosive vs. kinetic damage compare at the target. You can only compare the recoil of the two methodologies once you have equalized the damage to the target. It's certainly not easy to answer the question, but I don't understand why it is so hard for you to understand the question.
Oh, also a 2700 lb armor piercing shell does not contain 2700 lbs of explosive. It has a 41, that’s not a typo, 41 lb explosive charge.
OK, then I'll ask the question again: how does the kinetic energy of a 40 lb non-explosive shell at Mach 7 (which charitably assumes it will maintain that speed to the target) compare to the energy of 41 lbs of high-explosives, wrapped in 2659 lbs of metal, at their terminal velocity?
I keep asking the question, but you keep dodging it. I don't pretend to be able to answer it, but until you can, you can't compare the recoil. With different outcomes, it's like comparing a .22 rimfire to a .223 NATO.
Looks like the Battle ship may well be back. That or at least a sort of Monitor ship.
And you cross your arms, shake your head and say "You answer doesn't satisfy me."
Maybe you'd like to figure out yourself and let us know. This has been entirely one-sided -- pretty classic "bring me a rock" stuff. We've brought you the wrong rock at least half a dozen times.
I'm out.
No, it’s more like comparing a two oz rock from a sling to a 55 gr slug from an M-16.
Anything which expels a projectile, by whatever means, will have recoil. Look up the law of conservation of momentum. The recoil will be LESS, because we just have the projectile shooting out, rather than projectile plus gases, but there will still be a lot of recoil.
The big barrier to fielding a rail gun has been wear on the rail after each firing. The lab rail guns (maybe up until recently) have needed the rail section replaced after every shot. This is, of course, unacceptable in the field.
The projectile begins to decelerate as soon as it leaves the rails. Air drag increases as a square of muzzle velocity, so it doesn’t maintain its hyper velocity for very long. Once the projectile hits the apogee of its trajectory, it’s just going the same speed as a conventional artillery projectile. No free lunch with ballistics.
It's not a straight-line path. It's a parabola.
OTOH, the barrels on a battleship were supposed to be replaced every 400 firings or so.
I’d bet the rails could be moved inwards to compensate for wear on the fly. It’s probably easier to replace the just the rails than it would be to replace the rifling in machined barrels, too.
It’s more than just having a GPS receiver that can survive launch acceleration and EMP: the projectile will need a control system, servos, and either reaction steering or fins to re-point this beast to the intended target. All of that has to survive the launch process and it takes up internal volume of the projectile. I am still of the opinion that the rail gun is an expensive dead end.
I’m not sure that assumption is correct for low angles of fire.
If I shoot at a target 100 yards away, the bullet arcs in with the apogee between me and the target, but I’m pretty sure it’s still going faster than the 200 mph or so terminal velocity of a bullet dropped off a tall building.
40 lbs at mach 7 will punch a hole through most things. Picture a bullet passing through a sheet of paper. The target won’t absorb the energy, unless the target is the ground. Maybe this could create a local earthquake, like the WWII bridge-busters.
Sounds like the perfect product for the manufacturer.
What an awesome replacement parts volume.
You mean like the Copperhead round successfully demonstrated in the 80’s?
(only EMP hardened, of course)...
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