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What kind of system using modern technology would be able to counter a railgun projectile on a vehicle (both land and sea)? Would a think slab of angled armour in the shape of "<" work to cover the entire thing that needs to be protected or would an all-or-nothing design work better? On the other hand, would making something with no armour and a very thin structural shell project better as it allows the railgun projectile to overpenetrate?

The railgun in question would be this railgun tested by the US Navy. The projectile would just be the solid sabot fired by that gun.

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This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

  • $\begingroup$ The 'V'-shape would only help if it was always pointed at the projectile. Something like an upturned flat soupbowl might fare better i think. (It would deflect a horizontally travelling projectile upwards, independent of the direction (but not the azimut) $\endgroup$ – Burki Oct 5 '16 at 12:54
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    $\begingroup$ Protection for 🚢,🚁,🚀,🚅,🚃 or 👨? $\endgroup$ – user6760 Oct 5 '16 at 13:03
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    $\begingroup$ There's also the "be-elsewhere" armor, which requires no hardware changes at all -- only a conops change. :) $\endgroup$ – iAdjunct Oct 5 '16 at 13:38
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    $\begingroup$ If it is hard science then we need more specifics about the rail gun, payload, and target. $\endgroup$ – Jason K Oct 5 '16 at 16:35
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    $\begingroup$ Whoever downvoted everyone's answers is just making it so people don't want to answer the question. especially since all the answers have been accurate., though lacking in all but mine hasn't mentioned that you could use a magnetic field to stop a rail gun projectile. $\endgroup$ – Durakken Oct 5 '16 at 17:22
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You actually have two separate problems to consider here.

A hypervelocity railgun being fired from a tank or fire support UAV is coming in at a fairly flat angle and fired from a relatively short range (assuming this is Desert Storm VIII you might be able to get a sight line to the horizon, but even then you are only speaking about @ 5km).

OTOH, the naval railguns as described for fire support to ground forces are being fired from several hundred kilometres away (current USN descriptions of the subject speak of a range of 200km). In this case, the round is reentering the Earth's atmosphere from a high trajectory and coming at the target from a very steep angle. A "smart round" might actually deploy small fins to adjust the trajectory and strike at a plunging, almost vertical angle.

So your protective system(s) would be dealing with both rounds coming in at a flat angle and plunging fire from rounds reentering from space.

Currently, the direct fire threat is handled through heavy plates of dense armour. Some versions of the M1 tank use depleted uranium encased in steel, which for all practical purposes is about as dense as physically possible. This is considered the best way to deal with current APDS-FS rounds (Armour Piercing Discarding Sabot-Fin Stabilized). The current M829 round used in American tanks (NATO nations would use similar rounds) has a muzzle velocity of 1670 m/s, an effective range of over 3km and is considered able to penetrate 540 mm of RHA steel armour at 2000m, so you can see there is a considerable bar to clear.

Various counters have included thicker and denser armour, using layers of armour of different density to force the round to "tumble" and prematurely break up, using plates of glass or ceramic to shatter and absorb some of the energy of the incoming round, Explosive Reactive Armour (ERA) which shoots a plate of steel into the path of the oncoming round and even longer range active defence systems like DROZD or TROPHY, which use a rocket or mortar like projectile to intercept the incoming round. The Swedish "S Tank" had a "picket fence" arrangement on the glacis plate in an attempt to force incoming AP rounds to tumble, as an alternative.

enter image description here

TROPHY LV fitted to a MRAP vehicle

enter image description here

S Tank with the "Picket fence" installed

The problem with all these methods is the target is much heavier and needs to be fitted with more complex gear (sensors, firing mechanisms or ERA bricks and so on), which increases expense and reduces performance. There is also a danger radius around the tank as well, since the protective system must be automated and can fire without warning nearby troops.

This also has diminishing returns against a railgun round, since it will be moving considerably faster, meaning there is far less time to sense the round and react (in the case of an active system), and no practical amount of armour protection will stop the round. Given the size and energy of the railgun round, any laser system capable of destroying an incoming railgun (or even an APDS-FS) round in flight would be a main weapon in its own right.

Incoming rounds fired from ships at sea can be treated in a similar manner to incoming ballistic missiles. This means you are now looking at a dedicated theatre defence system, with long range radars and tracking systems, and possibly three levels of interceptor weapons to engage at high, medium and low altitudes. The problem here is the incoming round could be as cheap as a simple bar of metal, but even a sophisticated homing round would still be far cheaper than several sets of interceptors. The interceptors still need to be able to meet a target moving at a minimum of about Mach 6, so there is not going to be much time to react, or recover from a miss.

For a short range tactical defence system, it might be possible to have a set of UAV's circling overhead. They provide sensor coverage and can serve and the launch platform for high speed rockets to attempt to disrupt the railgun round in flight. The vehicle or bunker still needs heavy armour in case the railgun round breaks up in flight and pieces strike the target.

enter image description here

Think of each pod as being good against one incoming round

Protection against naval gunfire is most likely going to involve spoofing target detection systems so the ships cannot get an accurate fix on the target in the first place, followed by some sort of area defense system like "Iron Dome".

enter image description here

Iron Dome

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  • $\begingroup$ What sort of defensive measure could fire a rare earth magnet to intercept? The goal could be deflection in a near miss situation or a change in aerodynamics resulting in tumble/instability. $\endgroup$ – Jammin4CO Oct 6 '16 at 16:54
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    $\begingroup$ I'm not sure what you mean here? Fire a magnet into the path of the railgun projectile? The amount of magnetic field strength needed to deflect a projectile flying past at hypersonic velocity (especially since the magnet would also be moving at high speed) would be insanely high, and if the projectile itself was made of a non magnetic material (the sabot could be made of ferrous material), then the magnet would be useless. $\endgroup$ – Thucydides Oct 6 '16 at 20:28
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Probably an active defensive system, like reactive armor. Something to break up the projectile, spread out the impact, or even deflect it a bit. Aggressively sloped armor would also help, but there is only so much you can do. Pretty important to know what type of projectile the railgun is firing. Just a direct fire high density armor piercing dart, some sort of smart warhead, a high arcing plunging artillery round?

Allowing the round to zip right through wouldn't really work. Internal structure is filled with people, fuel, ammunition, people, electronics, and oh yeah, the people :) They react poorly to ultra high velocity rounds punching through. Even if the main round over penetrates, it still hits fast enough to convert what it DOES hit into plasma, spalling shrapnel, and in general, bad stuff. Your soldiers wouldn't really see "thin armor to protect against railguns!" as a plus :P Most main battle tanks (presumably what is mounting the rail gun) carry lower velocity explosive rounds for "soft" targets like things with thin armor to ensure a kill.

If the railgun round is coming in from a LONG way away (like from naval bombardment) then possibly a laser could deflect it or even destroy it. Counter-battery fire from your own railgun is a possibility, depending on how dumb the incoming round is. The high initial velocity of the incoming round lowers the flight time but also allows for a much longer range, so depending on how far out you can detect the incoming rounds, you have an opportunity to get something in it's way. The more complex the round, the easier it will be to disable or damage, but the harder it may be to hit (if it has passive or active defensive systems or even maneuvering capability). A solid spike of DU will be tough to destroy but it has a predictable ballistic arc.

But like in most things, the best defense is to not be targeted AT ALL. Either through stealth, misdirection, or high mobility.

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  • $\begingroup$ I like the railgun counterfire concept. $\endgroup$ – Willk Apr 26 '18 at 23:13
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Stealth and Active Defence

As @JasonK pointed out, allowing a projectile to get inside is generally a really bad idea, because the projectile never passes through hull plates, machinery, stored items such as ammunition, and people in nice and neat manner, but instead carries with it lots of fragments bouncing about inside the structure in a quite nightmarish manner.

So you have two options:

  1. Do not get shot at and hit by the projectile
  2. Do not let the projectile get inside

To stop it from going inside you can either bolt on more armor, or you can destroy the projectile.

And before you say "But you cannot shoot down a projectile", I say "Yes you can"

The idea of destroying the projectile before it reaches the hull is not even very new. Putting a mesh or anything quite flimsy in the way to break up and/or pre-detonate munitions has been employed for quite some time.

Swedish MBT model 103-C, with anti-HEAT slat armour at the front, and spare fuel tanks on the side

Swedish MBT model 103-C, with anti-HEAT slat armour at the front, and spare fuel tanks on the side to protect vulnerable parts of the drive-train

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Sadly, there is no defense against a railgun with armor if it should not get ridiculously thick. (We are talking about something about 10m thick).

After a speed of 3 km/s it does not matter if a projectile contains explosives or not, the amount of kinetic energy exceeds chemical energy and railguns are theoretically able to exceed this speed several times. So there are only a few options left:

  • Deflect. Move the projectile out of the collision path. This can be done by hitting the projectile itself with something, the sooner, the better. Deflect it out only a fraction of an angle is much more effective. Sloping is the idea of deflecting it at the last possible point, but is it not effective at such speeds because the necessary sloping angle is far, far too small. Remember, you need to contain something in the

  • Destroy. If we have such enormous amounts of power available, we could build something like a big condensator. Two metal plates with an insulating material between and charging it up. If the penetrator passes, the circuit is closed and if you can put enough energy in it, the penetrator will evaporate. Explosives can try to shatter the penetrator (active defense). Both approaches are very hard to implement for timing problems the faster the penetrator goes and once 10 km/s are reached explosives are useless because penetrator moves with the same speed as the shock wave.

  • Take the hit. You can also say, ok, then take it. Use self-healing walls and redundant systems and live with the fact that each hit will take several lives.

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In addition to what has been posted in other answers, layers of ceramic armor plates might work because railgun ammo should be similar in effect to KE penetrators, which ceramics are strong against.

In addition smoke launchers, perhaps combined with holographic projectors* to prevent targeting of weak spots.

*Lasers project false images of the target into the smoke.

Wikipedia on ceramic armour:

Due to the extreme hardness of the ceramics used, they offer superior resistance against a shaped charge jet and they shatter kinetic energy penetrators (KE-penetrators). The (pulverised) ceramic also strongly abrades any penetrator. Against lighter projectiles the hardness of the tiles causes a "shatter gap" effect: a higher velocity will, within a certain velocity range (the "gap"), not lead to a deeper penetration but destroy the projectile itself instead.[1] Because the ceramic is so brittle the entrance channel of a shaped charge jet is not smooth—as it would be when penetrating a metal—but ragged, causing extreme asymmetric pressures which disturb the geometry of the jet, on which its penetrative capabilities are critically dependent as its mass is relatively low. This initiates a vicious circle as the disturbed jet causes still greater irregularities in the ceramic, until in the end it is defeated. The newer composites, though tougher, optimise this effect as tiles made with them have a layered internal structure conducive to it, causing "crack deflection".

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Railguns are just high velocity rounds so standard plus extra defenses will work.

Thick Dual layered angled armor outter hull is the first basic level defense.
Beneath that you have fabric mesh surrounding the vehicle's inner hull that is tear resistant and some sort of self repair that will auto-fill any hole that is made.

The next step is point active defense which you target the incoming shot and vaporize it. Probably not the most effective defense but helps.

The primary defense though if you have the power to do so is a magnetic field. Remember it's a bullet that is being launched via magnetism. The bullet should thus be magnetic. A magnetic field that is strong enough can repel any such round.

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This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

  • $\begingroup$ A magnetic field that is strong enough to repel any such round is also strong enough to cause significant issues to both your health and that of your vehicle. $\endgroup$ – iAdjunct Oct 5 '16 at 19:37
  • $\begingroup$ @iAdjunct I don't agree. We can shape magnetic fields so the effects of a field could be eliminated and a minimum field could be used because we could target the object, extend the field length and strength that slows the round significantly to non-harmful rather than just stops it. Likewise you could have a very powerful field around a sheath that is protected from the field where the crew and mechanics are. While we can't do this perfectly yet, it is well within the realm of if we needed it we could build it tomorrow as all the principle technologies are known and available. $\endgroup$ – Durakken Oct 5 '16 at 20:13

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