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Railgun Deflection

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Phantasm

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Railgun Deflection

PostSun Nov 20, 2016 9:09 pm

Conventional cannons, such as those employed by the Resistance, have their effectiveness determined not just by the thickness of the target's armour, but also by its angle, as a shallow slope could cause a cannon round to deflect, with little damage, if the round comes in at the right angle.

The question is, does this apply to railgun projectiles, which are moving MUCH faster, and literally create contrails due to the friction created when they are fired. So would a railgun shot theoretically have a chance to deflect, or would it just ignore armour sloping altogether?

Speaking of which, for advanced races, the armies in Dropzone Commander sure don't give a damn about armour sloping. :ugeek:
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Octavian Lars

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Re: Railgun Deflection

PostMon Nov 21, 2016 8:11 am

I'll just quantify this saying that my knowledge is not infallible, but i have /some/ idea of what i'm on about (2nd year mechanical engineering degree and lots of interest in aerospace, railguns, tanks and such)
armour slope can protect in 2 different methods:
1) increased armour thickness due to geometry (i wrote a small app a few years ago that could calculate this) it's basically a cosine function i think, at 60 degrees slope, your effective thickness is doubled, so a t55 with say 100mm steel armour sloped at 60deg has an effective frontal thickness of 200mm steel. some other factors influence this, something called shell normalisation, but that's horrendously complex in reality.
2) actual deflection: at really steep angles (say the frontal plate of the UCM sabre), shells just won't "bite" into the front plate of armour, and will deflect off (as in a bullet ricochet). as far as i know, actually having a high velocity a la railguns is likely to increase the chance of a ricochet against steeply sloped surfaces whereas slower moving chemical energy projectiles (HEAT shells) are less likely to bounce off, and then will contact the tank, normalise and detonate as normal

just my thoughts, hope that helps
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Phantasm

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Re: Railgun Deflection

PostMon Nov 21, 2016 11:47 am

Octavian Lars wrote:I'll just quantify this saying that my knowledge is not infallible, but i have /some/ idea of what i'm on about (2nd year mechanical engineering degree and lots of interest in aerospace, railguns, tanks and such)
armour slope can protect in 2 different methods:
1) increased armour thickness due to geometry (i wrote a small app a few years ago that could calculate this) it's basically a cosine function i think, at 60 degrees slope, your effective thickness is doubled, so a t55 with say 100mm steel armour sloped at 60deg has an effective frontal thickness of 200mm steel. some other factors influence this, something called shell normalisation, but that's horrendously complex in reality.
2) actual deflection: at really steep angles (say the frontal plate of the UCM sabre), shells just won't "bite" into the front plate of armour, and will deflect off (as in a bullet ricochet). as far as i know, actually having a high velocity a la railguns is likely to increase the chance of a ricochet against steeply sloped surfaces whereas slower moving chemical energy projectiles (HEAT shells) are less likely to bounce off, and then will contact the tank, normalise and detonate as normal

just my thoughts, hope that helps


Some good points (as far as my limited mathematical knowledge can tell) but let's not forget that railgun projectiles (at least UCM ones) are described as disk-like in shape, compared the more cylindrical shape of a cannon round. I wonder if that would make a difference.

And also that, since we're using the example of a very function-oriented UCM Sabre, the materials are much lighter and (presumably) thinner. Although like you said, a 60 degree armour slope, which I'd say is near enough the UCM's front armour (going by memory) functionally doubles armour thickness when it comes to deflection.

A PHR walker on the other hand... Someone forgot about armour sloping when designing those...
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Sayrewolf

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Re: Railgun Deflection

PostMon Nov 21, 2016 2:07 pm

No, what he is saying is that a 100mm steel plate sloped at 60 degrees literally translates into 200mm armour that needs to be penetrated across the most likely angle of attack. I have a feeling that the numbers are quite a bit off but the underlying concept is sound. The possibility that a round could deflect is a fringe benefit to sloping armour, not a primary, (or even secondary etc) reason to do it.

As it happens a disc shaped projectile would be more likely to deflect. Imagine skipping stones across lake as a kid. The best kind were disc shaped. Same basic idea applies. Aside from that though, its actually quite wierd that they are disc shaped, I cant see the advantage since it would vastly increase the air friction on the projectile compared to a long thin rod based system and would diffuse the kinectic energy transfer over a wider area of armour. Anyone fancy coming up with a reason for that other than rule of cool?
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Re: Railgun Deflection

PostSun Dec 04, 2016 5:52 pm

Regards the Disc shape, perhaps it's to increase the projectile's chance of hitting something important after penetration. And I vaguely remember that the contrail of a railgun's shot was plasma or superheated gas. Bigger surface area, more plasma, more likely to kill crew even if it doesn't hit them. Also it depends on if they actually mean railgun or something more like a coilgun, cos if it is a railgun, the mountings could be smaller if its a discso maybe a higher RoF?
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Phantasm

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Re: Railgun Deflection

PostSun Dec 04, 2016 7:15 pm

Echo24 wrote:Regards the Disc shape, perhaps it's to increase the projectile's chance of hitting something important after penetration. And I vaguely remember that the contrail of a railgun's shot was plasma or superheated gas. Bigger surface area, more plasma, more likely to kill crew even if it doesn't hit them. Also it depends on if they actually mean railgun or something more like a coilgun, cos if it is a railgun, the mountings could be smaller if its a discso maybe a higher RoF?


Considering that PHR Railguns use cylindrical projectiles, it might be that the flat disk shape is yet another effort to reduce the Sabre's profile, meaning the Railgun itself can be flatter, and lighter and easier to transport.
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Octavian Lars

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Re: Railgun Deflection

PostMon Dec 05, 2016 9:10 am

The disk profile still seems pretty prone to deflection, though maybe with the shape/composition of scourge armour (the most likely targets) its probably quite likely to catch on the ridges of scourge armour and then do more damage to the internals?
just my thoughts
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Re: Railgun Deflection

PostMon Dec 05, 2016 9:56 am

Having worked with hypervelocity impacts doing my Physics research degree many years ago, yes, angle of impact makes a big difference to penetration.
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Octavian Lars

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Re: Railgun Deflection

PostMon Dec 05, 2016 10:07 am

well then, you're my new hero hahah (2nd year aero-mech engineering)
my hypothesis would be for that (tell me if i'm wrong) would be the normal force against the surface acting away (not going into the armour) even at small angles would be enough to deflect the projectile quickly before it could really do damage? obviously only really any use against hard targets like armour, and that's probably a drastic oversimplification
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Phantasm

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Re: Railgun Deflection

PostMon Dec 05, 2016 8:03 pm

Octavian Lars wrote:The disk profile still seems pretty prone to deflection, though maybe with the shape/composition of scourge armour (the most likely targets) its probably quite likely to catch on the ridges of scourge armour and then do more damage to the internals?
just my thoughts


Or maybe they're designed to target the LACK of Scourge armour. Those skimmers may be fast, but they can't take a hit like a Sabre.
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