Newtonian Aurora

[procyon]

So, will we get a new tech line called "Slug integrity", that starts at maybe 5000, and goes up from there?
The question would be, how do we treat it afterwards?

Not to worried about slug integrity.  If it could survive the hit - use that stuff as armor because it can survive the hit.

Degrading penetration if it goes any further?
After all, an armor square is a meter², so shell expansion wouldn't factor into the system much.
And a slug of molten metal, radiation and plasma is probably still as lethal as one from solid metal, given the speeds that are required to reach that state anyways.

After a quick thought, and check with a wee bit of math... I came to a conclusion.  (Very possibly incorrect, which won't be a first.  Comments expected.)

With the velocities we are expecting to see from the ships, the ship is likely to hit the slug - more than the slug hitting the ship as it were.  You can't guarantee that it will hit 'nose first'.  We shoot at relatively slow moving objects here on Earth.  That won't apply.

So my guess is with a fair chance that a ship will hit it from any vector (heck, it might come in from behind and slam into it a hundreds of km/s) - our slugs are going to look more like cylinders, or maybe even old time cannon balls.

The energy of the collision should be enough with even a 1kg projectile (assuming >50km/s) of penetrating a large amount of armor.  Lots more than most ships will likely pack on.  Didn't check the MJ level for armor, but with most measured in cm's - penetration should be assured for a spherical projectile.

Once your blob of molten/vaporized stuff gets through the armor, it is going to expand like a bomb.  Don't worry about it going out the back.  It will look more like a bundle of TNT going off.  I'm not worried about whether it will do damage.  It just shouldn't be limited to a few systems (unless you have internal armoring/bulkheads), it should take out anything it can expend energy on.  Any atmosphere in the ship is just going to propogate this massive shockwave.  If it has enough energy - it should gut a ship.  Not put out a few systems and then go on its merry way.

That was my point.  It wouldn't do limited damage to the inside of a ship.  If it was going fast enough into a ship filled with atmosphere - it could blow it up as completely as a bomb placed inside the vessel.

[fcharton]

Hi Procyon,

I very much agree with your analysis. Unless slugs are extremely small (and I don't understand why they should be), and relative speed is very low (ie the ship overtakes the slug), the amount of kinetic energy will be such that armour will make very little difference. With respect to projectiles, a hit is a kill.

On the other hand, long distances and large speeds would make 'aiming' extremely difficult. Even with perfect control on the firing vector (and there are physical limits on this), you can't expect slug and target speed to be absolutely constant, nor can you expect their trajectory to be perfectly straight (due to gravity, at least). And volleys of slugs shot at long distance would probably scatter a lot.

In my opinion, projectile weapons will make short distance combat impossible (which is why, I believe, missiles, and maybe some projectiles, must be area weapons), but at longer ranges they will become a form of "lottery weapon", with a small probability of sudden kill. And volleys of projectiles would only improve the hit probability at short range (as range increases, so does scatter).

Apart from luck, the only defense against slugs I can think of would be some yet to be handwaved "grav/mag/whatever shield" that could deflect incoming trajectories. This would work against slugs arriving on low angle trajectories, but probably not for direct hits.

Now, this raises an interesting question about missiles, and "explosive rounds" (if such things exist). Should they be fragmentation or "pure energy" weapons? (or maybe a combination of both)?

Francois

[procyon]

On the other hand, long distances and large speeds would make 'aiming' extremely difficult. Even with perfect control on the firing vector (and there are physical limits on this), you can't expect slug and target speed to be absolutely constant, nor can you expect their trajectory to be perfectly straight (due to gravity, at least). And volleys of slugs shot at long distance would probably scatter a lot.

Yes, we had a very long discussion earlier in this thread of the viability of long distance accuracy on rail guns.  I will defer (as will everyone else) to Steve's decision, but long range fire will be problematic.

In my opinion, projectile weapons will make short distance combat impossible (which is why, I believe, missiles, and maybe some projectiles, must be area weapons), but at longer ranges they will become a form of "lottery weapon", with a small probability of sudden kill. And volleys of projectiles would only improve the hit probability at short range (as range increases, so does scatter).

I expect Steve to set some maximum range for the rail gun projectiles.  How he figures it is up to him.  But having the processor track hundreds or thousands of rail gun slugs as they drift deep out system will really put a strain on the computer (I think).

Apart from luck, the only defense against slugs I can think of would be some yet to be handwaved "grav/mag/whatever shield" that could deflect incoming trajectories. This would work against slugs arriving on low angle trajectories, but probably not for direct hits.

Not sure if Steve will allow the detection of incoming slugs.  Hitting 'bullets with bullets' will be difficult.  I suppose some form of 'sand caster (ala traveller)' could deflect/disrupt them.  If you could see them long enough and could paint one with a high enough energy laser you may also be able to deflect (by vaporizing part of the surface)/ disrupt (by creating shock wave through rapid heating/expansion) it.  But it would take a lot of energy as you aren't likely to hold it in the beam for long. 

Now, this raises an interesting question about missiles, and "explosive rounds" (if such things exist). Should they be fragmentation or "pure energy" weapons? (or maybe a combination of both)?

Personnally I think all missiles should have a 'kinetic' setting.  Just don't arm the warhead.  Shrapnel will likely look like a railgun when it hits, unless the fragments are very large.  But a missile with a 4 ton warhead releasing 4000 - 1kg chunks of metal could be a real terror as it approached a group of ships.  Will make 'dodging' difficult. 

There could probably be a distinction for a pure kinetic kill weapon.  A 1kg projectile hitting a target at km/s will vaporize into a bomb like weapon.  A 1000kg chunk of metal probably won't.  Might fragment.
But with the energy it will contain the shockwave it should create will make the issue of 'will there be a hole in the back' more of a 'will there be a big enough piece left to identify the exit hole'.

As I said before.  I see this game happening at very long ranges if you plan to go home.  Up close the energy and accuracy makes it fairly suicidal.  If you are close enough to get a firing solution with your rail guns/lasers, you probably have a bunch of incoming ordinance heading toward you.


Long range sniping, perhaps survivable.  At close range it will be like fighting in a closet with hand grenades.

[UnLimiTeD]

And we all know what bloody fun that can be! 
So, if we have force fields at a distance to the projectile, or wobble shields through reactive armor, wouldn't that effect the effect on the target?
Could we use turreted pulse lasers in a last ditch attempt to deflect incomming rounds?
Could we mount shotguns that blanket an area of space with hundreds of small pebbles, thus making the rounds fragment before they hit the armor?

[fcharton]

I expect Steve to set some maximum range for the rail gun projectiles.  How he figures it is up to him.  But having the processor track hundreds or thousands of rail gun slugs as they drift deep out system will really put a strain on the computer (I think).

The way I see it (and this would apply to fragmentation missiles as well) is that you stop tracking a slug (or volley) once its chance of a random hit falls under a certain value. It is akin to rounding probabilities to a certain precision: below a certain value, everything ceases to exist.

Here are the maths behind the idea... Every railgun (or similar) has an "angular precision" (a), expressed in fractions of a degree. This factors everything in : launch bearing imprecision, fulctuations in course and speed of the projectile, imprecision is target determination. The best approach is probably to imagine a as a gaussian random variable, but I think a constant probability would work just as fine, and keep the calculations simple.
- Over a certain distance, this angular precision translates into a positional imprecision, as a times d (in fact tan(a).d, but a=tan(a) holds for such low values), so the probability to hit (in the case of a constant probability) is ratio between the surface of the target (PI r^2, where r is some average dimension) to the surface of the "drift cap" (PI (ad)^2 is a good approximation at a distance). In other words (r/ad)^2. You can use this formula to determine practical range from some angular precision, or the reverse, and correlate range to target size (it is obviously easier to hit a shipyard than a ship).
- Now, and this is, I think, the interesting part of the calculation, you could apply this calculation to a volley of slugs. Probability to hit would then be 1- (1-(r/ad)^2)^n, you'd then get a relation between range, rate of fire and size of target (and you can readily approximate it as n(r/ad)^2...)

To summarize, instead of tracking individual slugs, the processor would track volleys, and handle them as a probability of hitting over a certain range (decreasing as the inverse square of distance). This would not (I think) add unreasonable burden on the processor, but would account for the fact that railgun range depends on target size.

Francois

[UnLimiTeD]

As far as i remember a past discussion about this, steve will have them be deleted if they miss their target and theres currently nothing in the future path.
But if the target is in front of a planet, that planet will be hit.

[chrislocke2000]

As it stands it seems to me that there will actually be very little point in adding armour to your ships, better to spend the weight on increasing your acceleration or Delta V reserves so you can get out of the way as there is a good chance that any hit is going to be lethal irrespective of the armour you have.

Just looking at Steve's example of each armour block having 125MJ damage resistance, if we say a pretty well armoured ship has ten layers that does not give much protection on point hits at all compared to the numbers being tossed around.

On the shrapnel missile side of things I would expect 100gram ball bearings to cause enough damage, let alone 1 kilo slugs.

I like the idea of making shields particularly effective against kinetics and armour effective against energy weapons as a possible rock-paper-scissors approach. I also like the idea of some very close range laser defences that can track and shoot down slugs - potentially something limited to say a 10k range to enable enough energy to be applied to the slug.

On a totally different note I was thinking that perhaps my empire was going to need to invest in some slightly more effective escape pods - with the new mechanics I can see 14 days to be too short a time for rescue even when you have other ships in the system and judging my the weapon mechanics I'm going to be using a lot of them!

[bean]

With the velocities we are expecting to see from the ships, the ship is likely to hit the slug - more than the slug hitting the ship as it were.  You can't guarantee that it will hit 'nose first'.  We shoot at relatively slow moving objects here on Earth.  That won't apply.

The projectile doesn't care, but I can see this happening.  Cannonballs might be a good idea.  And I have some formulas for penetration I should dig up and test.

Here are the maths behind the idea... Every railgun (or similar) has an "angular precision" (a), expressed in fractions of a degree. This factors everything in : launch bearing imprecision, fulctuations in course and speed of the projectile, imprecision is target determination. The best approach is probably to imagine a as a gaussian random variable, but I think a constant probability would work just as fine, and keep the calculations simple.
- Over a certain distance, this angular precision translates into a positional imprecision, as a times d (in fact tan(a).d, but a=tan(a) holds for such low values), so the probability to hit (in the case of a constant probability) is ratio between the surface of the target (PI r^2, where r is some average dimension) to the surface of the "drift cap" (PI (ad)^2 is a good approximation at a distance). In other words (r/ad)^2. You can use this formula to determine practical range from some angular precision, or the reverse, and correlate range to target size (it is obviously easier to hit a shipyard than a ship).
- Now, and this is, I think, the interesting part of the calculation, you could apply this calculation to a volley of slugs. Probability to hit would then be 1- (1-(r/ad)^2)^n, you'd then get a relation between range, rate of fire and size of target (and you can readily approximate it as n(r/ad)^2...)

I haven't checked the math too closely, but it looks good.  One thing, though, is that you should be using radians instead of degrees.

[Yonder]

You wouldn't want to go without armor against nuclear explosions though, and especially lasers.

I've been thinking about what happens when a slug hits a ship, and I think one way to try to model the amount of dissipation on the slug directly.

Maybe have a ratio of the hardness of the armor and the slug, and from that you get the sideways acceleration on the cloud/molten ball of matter that was once the projectile after it hits the ship. Spread out the kinetic energy of the of the round at all the armor pieces hit at that level. If there is enough kinetic energy to destroy them then knock that amount off, calculate the new speed of the projectile mass, and widen the cone again. Continue until you either run out of kinetic energy or run out the back of the ship.

So a projectile hitting relatively slowly may have a damage pattern like this:
oooxooo
ooxxxoo
xxxxxxx
ooooooo

While the same projectile hitting the same ship at a much higher speed would be something like this:
ooxooo
ooxooo
ooxxoo
oxxxoo
oxxxxo
xxxxxx

[UnLimiTeD]

You are aware that the armor thickness per level is one centimeter and the size of one square is a square meter?
I don't quite think that a projectile the size of a tennis ball would spread out that fast.

[jseah]

but not enough, assuming that we are limited to human tolerances. 

I mentioned a while back that this was potentially a method to balance high and low G races. 

High G races can withstand higher maximum accelerations, giving their ships a boost in tactical combat. 
Low G races get to colonize damn near everything, giving them more ships in general. 

[Mel Vixen]

How comes you guys combine Gravity with G tolerances? Some animals survive Gs better then Humans, iirc peregrin falcons can survive some higher Gs for a short time. I see that Gravity and g-force-tolerances are linked but there has to be some variance in it.

[jseah]

Uh, gravity tolerance is the same as g-force.  Gravity is acceleration. 

A species that is adapted to life on a large earth-like world with 7g gravity can build ships that go at 7g accelerations without meeting any biological limit. 
No species would have any trouble on a ship accelerating at less than it's homeworld gravity. 

It's the question of how much *higher* than homeworld gravity can a species survive that can have variance. 
Although it is obvious that higher-G races would cope better with higher accelerations.  I dunno, guess it might be proportional?  1G races might have an average tolerance maximum of say 1.6Gs for long periods and 10G races might have an average tolerance max of 16Gs for long periods. 

[Yonder]

You are aware that the armor thickness per level is one centimeter and the size of one square is a square meter?
I don't quite think that a projectile the size of a tennis ball would spread out that fast.

At these velocities the projectile will very violently explode, I think that it will have a decent spread rate. It can also be handwaved as not only the area of the ship that is physically touched by the projectile, but also that is destroyed by the shockwave of the armor being pushed out away from the projectile to make room for it.

[bean]

How comes you guys combine Gravity with G tolerances? Some animals survive Gs better then Humans, iirc peregrin falcons can survive some higher Gs for a short time. I see that Gravity and g-force-tolerances are linked but there has to be some variance in it.

There are several reasons for this.  One is that the creature in question is smaller then a human, and the square-cube law works in its favor.  For example, if you threw a mouse out of an airplane, it would land totally unharmed.  A rat wouldn't.  Partially, it's the lower terminal velocity of the mouse, and partially, the mouse's size.