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Next question about kinetic weapons in my universe: We have a coilgun/railgun, it launches a projectile at 30 km/s; if it meets a compartmentalized spacecraft on its path, does the projectile go straight through the hull, or blow into schrapnel/plasma just after hitting ship?

If not either of the above, what does happen?

What I mean by compartmentalized spacecraft: instead of one propellant tank, there are many, and in between them armored crew sections are sandwiched. All of it is divided by bulkheads, and external envelope of the ship is light armor capable of stopping small space trash and meteors.

Additional information: The projectile material is tungsten, ships are mainly made of something strong and light, i.e. good steels, titanium, some composites maybe. Projectile can pierce the armor used in crew sections if it is still intact after going through rest of the ship (which I am trying to determine). Anti meteor armor is a Whipple shield with two thin layers of light metal.

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    $\begingroup$ What material is the projectile made out of? What Material is the ship made out of? Is the projectile blunt? Pointed? Could the projectile pierce the armored crew sections? This question is way too broad and doesn't give enough information to answer it. $\endgroup$ – Jason Desjardins May 22 '18 at 22:13
  • $\begingroup$ As an illustration of how impossible it is to answer this generally, note that armored piercing rounds sometimes pass right through a tank instead of (more usually) not doing that. Some happy tank crews have lived for this reason. You can't easily predict what will happen even with detailed design info and you don't have anything more than a vague sketch. $\endgroup$ – StephenG May 22 '18 at 22:39
  • $\begingroup$ @Jason Desjardins edited $\endgroup$ – Mranderson May 22 '18 at 22:42
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    $\begingroup$ If this ship is not a jump ship and actually travels in space then it will have to withstand similar impacts from meteorites, especially if its travel speed is close to light speed. So I think its normal shielding would suffice to repel this projectile (it probably doesn't work by absorbing the impact). $\endgroup$ – Real Subtle May 23 '18 at 8:01
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    $\begingroup$ This question has been flagged "too broad." I disagree that it's too broad. Consider that (fundamentally) any projectile material that is more dense than the target material will simply pass through the target given sufficient velocity. However, that's not necessarily a bad thing. Heat from friction, compression as it hits the interior atmosphere, plus the exterior vacuum, suggests the ship might blow apart similar to an apple hit by a 7.62mm shell (which I've done). $\endgroup$ – JBH May 28 '18 at 3:23
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I highly recommend fully reading through the following link.

Most of the research on hyper velocity impacts looks at objects traveling at about half your projectile speed because about 15km/s is the most we expect to need to worry about in regards to small debris.

However, Whipple Shielding is highly effective at stopping small impactors at hyper velocities. If you look at figure 4-2 at that page, you will see that the effectiveness of the Whipple shielding on the ISS drops off at higher velocities, but should still be at about half effective at the speeds we are talking about (also, what might be important for story purposes, Whipple shielding is actually shockingly ineffective against projectiles at around 2km/s (though more traditional shielding is usually behind the Whipple shielding).

Impacts against Whipple shielding will produce clouds of plasma as the impact material (and shielding) disintegrate. While this won't cause damage, but it can mess with electronics.

Something important to note about this. Whipple shielding testing is done with Aluminum spheres with a diameter between .5-2 cm. Larger projectiles have more energy (though only linear, unlike the quadratic increase from velocity).

This video shows the impact of a small (4mm) hyper velocity projectile hitting a non-pressurized tank in a vacuum. You can see the blast of plasma and shrapnel that fly out.

The wikipedia page for Hypervelocity has a pic of more traditional shielding. For reference it is 18 cm thick and the projectile is 1.2 cm.

High velocity impacts cause the materials to behave as fluids because materials can behave like fluids under high stress. This page has some useful areas showing you what damage can occur even when not catastrophic.

You can end up with what is called "detatched spalls." Internal fracturing of the material could cause shrapnel even if the material itself was not penetrated.

Here you can read more about the materials used in shielding, and this will let you compare different shielding styles (Whipple is just what is used on the ISS).

This paper includes some useful graphs that you can use to extrapolate penetration depth.

But what will happen with a larger projectile. NASA and the ESA quote "catastrophic failure" for 10cm projectiles. But what happens to the projectile.

Unfortunately your question falls outside of what people typically will test. Spacecraft shielding typically is tested against small impactors. Larger impactors tend to be tested against rock (for cratering of moons).

I am assuming your projectiles are going to be larger than 10cm?

I can say for certain it won't be fully intact. You will get some plasma and some shrapnel. Will your projectile continue in to impact more things? It's hard to say without knowing more.

If you give me an approximate projectile size and armor thickness, I can run a simulation for you and get back to you with "nice" pictures and edit my question, but with the details as given I think my answer is suitable.

If you want to run the simulation yourself, I would recommend gizmo. Actually iSale would be even better / easier. One of their examples is exactly what you need as long as you tweak the projectile size and speed. However, you would need to contact them to get permission to run it.

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According to the wiki and other sources I cant be bothered to look up right now (if only because I cant remember how or where I found them in the first place), at, or above, a certain velocity metal will act like a fluid upon impact. https://en.m.wikipedia.org/wiki/Hypervelocity

Now it doesn't matter which is moving, both the projectile and the target will experience this. So upon impact both will deform. Additionally, the impact will accelerate the pieces the projectile comes into contact with and turn its 30km/s velocity into energies like heat. So the question would need some info about the projectiles weight, density (I don't think we'll get accurate data on how most materials behave at Hypervelocity impact) and shape of the projectile that contacts.

The formula for kinetic energy has the square of velocity times mass, which means higher speeds builds kinetic energy faster than more mass and 30km/s is a lot. If the projectile is relatively small it would impart 100% of its energy into the target causing essentially an explosion consisting of the projectile and the parts it came into contact with, which isn't going to be pleasant.

If it is larger it wouldn't lose all its kinetic energy on impact and drill through the ship, causing fragments of what it smashes through to spiral through the ship. It might be better to put less armor on and make sure the projectile just tears a hole through the ship as less total energy is imparted, as you can quickly reach nuclear explosion strength kinetic energy that you need to dissipate if you try to stop it with armor.

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If not either of the above, what does happen?

Ricochet.

You have 2 options which can happen: projectile traverses target at same trajectory retaining kinetic energy, projectile explodes on / into target expending kinetic energy.

The third option is that the projectile hits the target, expends a little bit of energy and continues on at a reduced speed and a different trajectory. The Brad Pitt tank movie has a lot of gore but excellent tank battle scenes including many where a shell bounces off of a tank's armor - Brad's crew bounced several off of heavily armored German tanks. Check Youtube.

So to your ship. I think tank armor is angled for this reason (correct me if this is wrong, commenters). In space, it seems to me the best armor shape for this would be very long very hard conical spikes. Unwieldy on land but fine in space. An incoming round would encounter the side of a spike and tend to ricochet off trajectory, missing the ship.

Needless to say this spike ship would be immensely bad of ass, bristling with spikes, many of them broken / fused / scratched silver from prior deflections.

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