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Why would you need to rifle the barrel of a railgun?
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Accuracy. If you're going to be firing a round a couple of hundred miles that does it's damage by direct impact instead of an explosion, best make sure it hits.
Soccerman, electricity moves at the speed of light (or close enough). It's not as if you need to physically move it yourself, you just need to have a large capacitor ready to discharge into the rails when you press the button. I'm pretty sure that's how the current tests systems work.
Lupus: At the ranges we're talking about rifling won't be much of an aid anyways, as wind, and any small course deviation would throw the round way off target after 200 miles. That's why they are looking at fin stabilized GPS guided designs.
As a side note, the Abrams battle tank uses a fin stabilized rounds, as it has a smooth bore barrel. Seems to work pretty well.
True, I'm just curious as to how they would go about it if it's something they went for on smaller scale guns. Just twisting the path of the conductor/projectile would mean areas of no force or reversed force, so I'd just find it interesting to see how rifling could still be achieved like that
Using a railgun to launch a missile which then kicks in would give some impressive range. Sort of like the Shagohog from MGS3 hehe.
Lupus, considering that railgun rounds use discarding sabots, rifling wouldn't make a bit of difference, as the round separates from the sabot anyways. (Edit: well, I suppose if the sabot rotates while keeping a nice tight grip on the round, but I'm not sure that'd work, or if it's necessary. Seems like something that would just increase rail ablation.) And as such, a smaller system could still use fin stabilization. If we're talking "handheld" small, then I don't know.
As for the railgun/missiles combo I have a feeling that might come to pass. It would be a very effective way to speed a missile up enough to activate a scramjet engine and let it fly further at hypersonic speeds. That would let you eliminate a lot of mass from the missile by removing the first rocket stage necessary to speed it up enough for the scramjet to be able to work.
The problem is in discharging the capacitors. A capacitor isn't going to completely discharge instantly, so the current is going to be limited. To give ya some numbers, or the means to get some actual numbers, the charging and discharging of a capacitor is based on a time constant which is equal to the capacitance * the equivalent series resistance. It take 5 time constants to fully charge and discharge a capacitor. And shorting a cap like that will cause the dielectric material in the cap to break down, so you'd have to replace the cap each time.
Unfortnately I don't know off hand the specs for some really large caps to see what the discharging current rate is, but then I have no idea what strength of magnet they used.
hmm, gonna have to do a little experiment this weekend, connect a battery to two large pieces of metal, see what the potential is between them.
They mention that they use multiple capacitors, so perhaps they have quite a few capacitors set up with each discharging to only one portion of the rail in sequence.
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I'm not saying rifling is a better way of doing it, I'm just saying it would be interesting to see how it was done if they managed.
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I'd be interested too, especially if that would be possible, but I doubt they'll bother.
Soccerman I don't know what the heck you're talking about, and I suspect you are more in my camp than you'd admit
They charge capacitors and discharge them into the rails to fire the gun. The projectile itself is usually a non-conductive metal slug like tungsten, that sits in a conductive sabot. All this gas nonsense is goofy, and as for caps blowing, I wouldn't be surprised if that's one of the problems they're working on ironing out, along with the problem of projectiles and sabots melting and fusing to the rails, or the outward force created pushing the rails apart, all of which are problems that are being worked on, which is why the technology has been understood well enough to test for a while (hell, I know a guy who built one himself - it shot pennies and had a capacitor array the size of a milk crate - I think he might have blown a cap once actually but I don't remember) but isn't yet implemented in the field.
Replies
Why would you need to rifle the barrel of a railgun?
[/ QUOTE ]
Accuracy. If you're going to be firing a round a couple of hundred miles that does it's damage by direct impact instead of an explosion, best make sure it hits.
Lupus: At the ranges we're talking about rifling won't be much of an aid anyways, as wind, and any small course deviation would throw the round way off target after 200 miles. That's why they are looking at fin stabilized GPS guided designs.
As a side note, the Abrams battle tank uses a fin stabilized rounds, as it has a smooth bore barrel. Seems to work pretty well.
Using a railgun to launch a missile which then kicks in would give some impressive range. Sort of like the Shagohog from MGS3 hehe.
As for the railgun/missiles combo I have a feeling that might come to pass. It would be a very effective way to speed a missile up enough to activate a scramjet engine and let it fly further at hypersonic speeds. That would let you eliminate a lot of mass from the missile by removing the first rocket stage necessary to speed it up enough for the scramjet to be able to work.
Unfortnately I don't know off hand the specs for some really large caps to see what the discharging current rate is, but then I have no idea what strength of magnet they used.
hmm, gonna have to do a little experiment this weekend, connect a battery to two large pieces of metal, see what the potential is between them.
http://www.popularmechanics.com/technology/military_law/4231461.html
They mention that they use multiple capacitors, so perhaps they have quite a few capacitors set up with each discharging to only one portion of the rail in sequence.
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I'm not saying rifling is a better way of doing it, I'm just saying it would be interesting to see how it was done if they managed.
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I'd be interested too, especially if that would be possible, but I doubt they'll bother.
They charge capacitors and discharge them into the rails to fire the gun. The projectile itself is usually a non-conductive metal slug like tungsten, that sits in a conductive sabot. All this gas nonsense is goofy, and as for caps blowing, I wouldn't be surprised if that's one of the problems they're working on ironing out, along with the problem of projectiles and sabots melting and fusing to the rails, or the outward force created pushing the rails apart, all of which are problems that are being worked on, which is why the technology has been understood well enough to test for a while (hell, I know a guy who built one himself - it shot pennies and had a capacitor array the size of a milk crate - I think he might have blown a cap once actually but I don't remember) but isn't yet implemented in the field.