Newtonian Aurora

[UnLimiTeD]

Well, the figure I used there was expecting a speed of roughly 100 kps.
Sure, on other speeds we really have no idea.^^

[jseah]

Once you have a kinetic weapon going through the ship and exiting the other side, some of the kinetic energy will be deposited on the ship and the rest carried out by the exiting round. 

As you increase the kinetic energy of the weapon (and thus increase proportionally sqrt impact speed), surely more kinetic energy is deposited on the ship?
The ratio of energy on the ship to initial weapon energy may decrease, but I would expect the absolute amount of energy placed on the ship increase. 

Of course, by the time you have this, the damage is usually pretty severe anyway. 

[UnLimiTeD]

Thats what we've been discussing those last few pages. 
We expect that at a certain level, likely a few 100 kps tops, the projectile is going to completely disintegrate, thus spreading out.
It might have an effect like detonating a small nuke inside the ship.
If, however, the projectile goes too fast, it'll exit out the other side before that can happen, thus decreasing the effect.

[jseah]

Oh yes, the transition from projectile not exiting to projectile shooting through may mean that increasing the energy over that threshold would decrease damage. 
 - And I'm not entirely certain that this would actually reduce damage at all.  As you increase projectile energy, its going to get closer to the other edge of the ship.  As you approach the "shoot through" energy level, you get spallation on the other side of the armour, carrying energy away.  Around the "shoot through" energy level, armour plating on the other side is going to flake off or simply be blasted right out of the hull by the shockwave. 

Either way, there could simply be a reducing damage to energy ratio as you approach the shoot through limit without actually reducing absolute damage at any point. 
I don't know enough to say either way. 

But from there, further increasing projectile energy will only increase damage. 

[UnLimiTeD]

I doubt that.
At an impact of 1000 kps, the projectile will disintegrate, which means turning into very hot gas and dust, the blast traveling through the ships atmosphere.
The expansion of this cloud of death can only go so fast, so if the projectile is so fast it only measureably expands when reaching the other end of the ship, the harm done is noticeably smaller than if it detonates inside the ship.
So decreasing the projectile speed by 100 might increase the effective damage, while increasing it will make it harmless at some point.
Increasing the projectiles size will do more, if it's at all measurable when the ship's gone, but more speed will not always make a difference.
In fact, whether shields should be used or not depends on speed as well, if the energy of the projectile can be stopped by the armor if spread out, a shield to break the shot before it hits the armor is useful, if it can't, a shield will actually increase the internal damage.
Unless you're exactly at the point where the projectile would reach the inside and scatter, but not fully fly out again, in which case the shield would slightly reduce internal damage at the cost of armor.

I'm slowly reaching the point where I'm just willing to wait until I can test it. 

[procyon]

This is not right at all.  First, IEDs are generally not shaped charges.  They're bombs.

No arguement.  Lots were/are just old Soviet WWII era 152mm shells.  Buried in roads.  Stuck in a pile of trash or junked car on the roadside.  Those aren't too dangerous to an M1.  Usually blows a tread, tears up a road wheel or two, screws up torsion bars, etc.  Hard on softer targets, but that is to be expected.
What the tankers fear are the old shells with about 1-3kg of copper strapped to the side and lined up with the road.

An RPG-7 can't penetrate the frontal armor on an M1, and it's going to have a much better warhead.  Second, the speed of a shaped charge jet tip is on the order of 7 to 14 km/s, not 3 km/s.

RPGs don't do well against the frontal armor.  Usually don't make it past the side either.  Can't go into the configuration of Chobham as it is still classified (getting the tankers and infantry to sign papers to not disclose what they saw when the armor was penetrated was a pain) but it works pretty well disipating the energy of the shaped charges.  But a solid chunk of copper hitting it just cuts right through.  Too much energy.  And most of the copper blocks were/are going a couple km/s. 

Same physics that allow our penetrators to cut through vast amounts of armor, just far more primitive.  But as one of my instructors in basic pointed out, an old obsolete rifle will kill you just as dead as the latest in technology.

And just so we're clear, energy is always proportional to the square of velocity.

Energy yes.  Momentum no.  Just being a little facetious.  Sorry.
If you got to deal with the number of sites I did, you tend to develop some 'coping strategies' when talking about IEDs. 


And in reply to the many posts positing that the projectile will exit the target in some localized area - I will simply have to disagree.  It will turn into a gaseous cloud of immense energy.  The original projectile will have a certain amount of momentum that will try to drive it out the back end of the ship.  Unless you just barely grazed the target you have hit a fair amount of mass (the armor/hull) that was part of the ship.  This material has the same momentum as the ship does/did - and just absorbed a bunch of energy. It will not be moving to exit the ship in some organized manner.  It will just be moving to deposit the energy it has as randomly as it can (per the 2nd L. Therm.).  As will every structure in the ship that is 'hit' by this gaseous cloud of energy.  The 'particles' of the projectile will still have momentum trying to drive them through the ship, but individually the particles will have considerably less momentum than the objects they are likely to strike.  They are likely to be 'stopped/captured' by the structures they impact inside the target.  They will still be carrying a large amount of energy that will then be transferred to the structures - which will also begin depositing this energy to the rest of the target.  Add in the thermal wave of IR radiation going in every direction this whole cascade is generating and it just gets worse.  Unless the ship is very small and made of tinfoil - it is going to absorb a large percentage of the energy from the projectile to its structure - and not just in the path of the projectile.

If you feel that the projectile exits the back, then there isn't much experimental data on what happens to contradict you.  I don't know of any organized attempts to shoot 'space vehicles' with 10's of km/s slugs to see just what happens. 

I believe that is will look like you placed a large amount of explosives inside the hull.  A big flash and detonation, with an expanding cloud of debris after.  But to each their own.

Whatever Steve codes for, I will happily work with. 

[UnLimiTeD]

As said, it depends on speed.
While yes, the projectile will scatter, if it is too fast, it will punch straight through because the expansion of material is physically limited.
Until the point where the matter hits so fast we see nuclear fusion as a result, which in late game could happen.

[procyon]

While yes, the projectile will scatter, if it is too fast, it will punch straight through because the expansion of material is physically limited.

Of the projectile, if the structure doesn't capture the energetic particles of the gas it becomes.

But the structures of the target that absorb the energy won't have this problem.  They will release the energy they absorb fairly uniformly.  Whatever the 'gas/projectile' hits will become the next detonation.

EDIT

If your target is in single digit meters and the projectile hits nothing but hull (no intervening structures - but you apparently don't mind wasting space in your vehicle if this is the case), maybe it would just leave a pair of holes and a lot of very hot material exposed to the impact sites.  This necessitates that the projectile also hit nothing with an atmosphere.  The gas will propogate the shockwave.

But if your ship is measured in 10s of meters with large structures inside it that intersect the projectile's course, it really should make nice fireworks.

EDIT 2

I suppose the easiest way to illustrate this is that the projectile is likely going faster than the speed of 'sound' in the material it hits.  This means that any material struck will tend to displace to the side, as in any shockwave propagating in a stationary medium per Cherenkov.  I really don't like to dredge up the math as it is not the most refined area of science at the moment.  But most (not all) everything this projectile hits will be displaced sideways expanding into the target.  This will be bad on the target if the gas of the projectile is captured by the target.

[bean]

No arguement.  Lots were/are just old Soviet WWII era 152mm shells.  Buried in roads.  Stuck in a pile of trash or junked car on the roadside.  Those aren't too dangerous to an M1.  Usually blows a tread, tears up a road wheel or two, screws up torsion bars, etc.  Hard on softer targets, but that is to be expected.
What the tankers fear are the old shells with about 1-3kg of copper strapped to the side and lined up with the road.

RPGs don't do well against the frontal armor.  Usually don't make it past the side either.  Can't go into the configuration of Chobham as it is still classified (getting the tankers and infantry to sign papers to not disclose what they saw when the armor was penetrated was a pain) but it works pretty well disipating the energy of the shaped charges.  But a solid chunk of copper hitting it just cuts right through.  Too much energy.  And most of the copper blocks were/are going a couple km/s. 

Same physics that allow our penetrators to cut through vast amounts of armor, just far more primitive.  But as one of my instructors in basic pointed out, an old obsolete rifle will kill you just as dead as the latest in technology.

If you feel that the projectile exits the back, then there isn't much experimental data on what happens to contradict you.  I don't know of any organized attempts to shoot 'space vehicles' with 10's of km/s slugs to see just what happens. 

I believe that is will look like you placed a large amount of explosives inside the hull.  A big flash and detonation, with an expanding cloud of debris after.  But to each their own.

Whatever Steve codes for, I will happily work with. 

I'm a tiny bit skeptical about this.  No offense, but anyone can say anything on the internet, and I find it hard to believe that a couple kilograms of copper is some sort of wonder penetrator.
As for penetration, there's a professor at my school who studies armor penetration and space debris.  I'm meeting him on the 26th, and will try to get some answers.

[Yonder]

Damage to the spaceships could be limited if we posited extremely effective crumple zones in the structure and armor that limited the energy dissipation perpendicular to the path of the round.

In fact that could be an explanation for our very discrete armor "spaces". Maybe each armor space is separated from the next by one of these great crumple zones.

[Steve Walmsley (OP)]

That's why I think sometimes, in gaming and science fiction (Stargate ), physical laws must be bent or simply ignored to make the game or the show more enjoyable.  Are you traveling at relativistic speeds? Invent something that creates some kind of space-time bubble around your ships to maintain coherence.  Are you accelerating at a rate which would kill any human? Put some cool inertial dampener which god knows how it works.  Do you need to turn around your ship to counterattack an enemy ship at your back? Just do it like a boss.

Beside, science change a lot every few years.  Actual working physical laws can be completely wrong in a decade.  Adapting centuries of development and science investigation in our campaings to 21th century physics is like trying to supply water to a growing city through the same pipes.  Sure, they will work for the first 200,000 hundred people, but when the city reaches 1 million inhabitants, those pipes are not going to be enough.

However, I think it's pretty interesting that kind of aproach.  Personally, I would prefer a little "science fiction" here and there, but trying to build a space empire with today's limitations is. . .  challenging at least.

I agree that bending or ignoring the laws of physics where necessary is a reasonable idea to make a game playable and enjoyable. That is the approach I took with Aurora. The whole point of Newtonian Aurora though is to try to implement realistic physics as much as possible and see what happens. I am not convinced it will turn out to be playable so the whole game is really an experiment

Steve

[fcharton]

And in reply to the many posts positing that the projectile will exit the target in some localized area - I will simply have to disagree.  It will turn into a gaseous cloud of immense energy.

A few figures to support this...

Suppose the slug is metallic, its specific heat will be in the 100 - 1000 J / kg K (depending on its density), and its boiling point will be in the range of 1000 - 6000 K. Thus, the energy needed to heat a 1kg slug to melting point would therefore be on the order of 100 KJ - 6 MJ, say around a megajoule. (Note : correct calculation is more complicated as you'd need to add latent heat, take care of pressure, etc, but the order of magnitude should be fine...)

A 1kg slug (for instance, the calculation is independent of mass) travelling at 100 km/s will have a kinetic energy of 5 gigajoules (0.5 x 1 x 100 000^2), and 500 GJ at 1000 km/s. Thats 5000 to 500 000 more than the energy needed to vaporize the slug.

Now, the slug could explode out of the ship if the time it takes to vaporize is longer than its travel time through the hull. Assuming a 100 metres cross section, that would be 1/1000th of a second at 100 km/s, and 1/10000th at 1000 km/s. Not sure how you calculate the "heat speed", though...

Francois

[Yonder]

Not sure how you calculate the "heat speed", though...

I have no idea either. Perhaps the speed of sound of the gas would be a suitable approximation? Of course that requires the knowledge of the temperature of the material, which would also have to be approximated somehow.

Maybe say that some arbitrary fraction of the impact energy (1/100th, 1/1000th?) goes into instantly heating the projectile, calculate the heat of the projectile, then the speed of sound, then use that.

That's two layers of completely arbitrary assumptions, but it may look reasonable. I think that's what we are going to have to do. List out a bunch of wacky and arbitrary methodologies, pick a bunch of those that sound most reasonable to us, then go with the one out of those that sounds like the best for gameplay.

[Steve Walmsley (OP)]

This is exactly the case.  The fact that you present it as a problem indicates that you don't understand a salient fact about space travel: ships are not maneuverable.  In any case with a reasonable delta-V to acceleration ratio (where you are accelerating over the course of days), you will not be capable of serious combat maneuvering.  They will spend days building delta-V, and that will prevent them from making quick turns.  To see any difference, you need hundreds of Gs, and that is simply not practical, even with drones, for engineering reasons.
Putting a 10G engine on a ship is going to impose enormous penalties for the vessel in question.  Not only do you need 10 times the engine of a 1G ship, you also need about 10 times the structure.  At that point, there's not much room left for weapons.

Matching vectors with the enemy ship might be the way to go for closer combats.  It leaves both sides with more options.
That would help mitigate the drive-by holocaust problem, and even more so if there is a range limit on the tracking commands.  You can't control a missile from way, way out-system.

I agree. Ships will definitely not be able to manoeuvre significantly in any short-time frame. It will be about positioning pre-engagment and making manoeuvres that could take several hours or days to complete. On the other hand, my experience with the limited missile engagements I have tried so far indicate that missile flight times could be on the order of days for some battles rather than minutes or hours.

Steve

[Steve Walmsley (OP)]

I was actually excluding railguns because their projectiles (in a newtonian setting) will be imparted the ship speed.

This is true. Railgun projectiles start with the ship speed. I am slowly forming an opinion that railguns will probably have high damage but low accuracy. They have low muzzle velocity (relative to likely ship speeds), which means they will be relatively easy to avoid. They will have potentially high impact velocity when launched from a fast ship because the ship speed is added but even then they will be difficult to aim because you will have limited control over the directions in which you can fire them as a large part of their post-launch vector is preset by the ship's vector.

Lasers will be much more accurate because of their high muzzle velocity but the beam widens with range so they will have less of a concentrated impact. In fact, depending on range the beam could be wider than the target ship so a lot of energy will be lost in that case.

Steve