Newtonian Aurora

[Arwyn]

And from a purely defensive posture, beam weapons would be ideal for defense against the "killer kinetic". A laser will be operating at speed of light, so hitting something on a closing bearing is computationally possible. And it would not need to "kill" the projectile, even a glancing hit would cause the projectile to heat and lose mass in reaction. Obviously the further away you engage, the better, but at the speeds your talking about, a few degrees of adjustment to the path of the projectile will generate a miss.

Combat in Newtonian Aurora is a LOT like WW II sub warfare, and it doesn't take much in terms of speed or course adjustment to screw up a shot.

A perfect shot IS a one shot kill. But torpedo spreads were fired to allow for changes in course and bearing from the target.

Similarly, constant speed and bearing in Newtonian is going to make it much easier to hit with unguided munitions (or missiles for that matter). Throw in some constant course changes and speed changes, and your targeting solutions get MUCH more complicated. Downside is your burning reaction mass to do so.

If your going for realism, I think it would be very likely that warships would be entering a potential battlespace with exactly that in mind. They would be burning reaction mass to do constant speed and course changes to make it that much more difficult to put together and accurate intercept.

With the initial speeds Steve is talking about for kinetic weapons, your pretty assured that they are going to be fairly short ranged due to those variables. Beam weapons operating closer to the speed of light are going to be more effective at range from a hitting perspective, but they aren't going to be carrying the kind of energy potential that the kinetics will.

[Steve Walmsley (OP)]

Similarly, constant speed and bearing in Newtonian is going to make it much easier to hit with unguided munitions (or missiles for that matter). Throw in some constant course changes and speed changes, and your targeting solutions get MUCH more complicated. Downside is your burning reaction mass to do so.

I'll almost certainly be adding some type of optional automated random course and speed change, where you can specify how often and to what extent they take place. The cost will be fuel and added travel time. I can't overestimate how important fuel is going to be in this game.

Steve

[chrislocke2000]

Given the expected lethality of kinetic weapons it does seem to me that we need a better way of defending ships. As already mentioned the US have deployed a land based version of their CIWS system to shoot down incoming rockets, mortars and artillery in high risk areas in Afghanistan. Given the need to deal with atmospherics I could happily see an evolution of this tech to shoot down incoming ordnance. It's really then a matter of how far they will need to be able to see to react and engage.

From a bit of an internet trawl I've seen contact to kill times of 5.5 seconds for a goalkeeper system which is a pretty old piece of kit. Maybe a reaction time of 2 seconds dropping to 1 with increased tech would therefore be reasonable for Aurora. Assuming a worse case closing speed of say 12k kms that gives a required detection range of say 25k km. That does not feel too bad to me for a 1kg slug.

One other thing I noticed with the CIWS was that the heaviest in operation today is about 10 tons. Admitidly it still needs some power but I would think that anti kinetic CIWS could be substantially smaller than those in the game at the moment, allowing all ships to field several each. This makes it harder to get a munition through but once you do it counts.

[chrislocke2000]

Just been thinking about turrets and how they could benefit a ship.

As I understand it, at the moment guns have a targetting error due to an assumed mix of errors in sensor and the accuracy of the gun itself / lens jitter. I would think that these errors would be compounded by the effects of being under thrust and the need to aim by moving the whole ship.

Turrets can address these issues by creating more stable platforms from which to shoot. For lasers especially this could have a significant impact on effective range of the weapons. You could therefore have a turret tech that increasingly reduced the impact of thrust and movement on overall accuracy.

[jseah]

re projectile defence:
You are forgetting the fragmentation missile.  Railguns on ships slugging it out like in TN Aurora aren't what I would expect to see. 

It's the missiles that close at 4x ship standard velocity and turn into a cloud of a few thousand 1kg pellets.  It has the same effective ranges as a railgun but the ability to salvo missiles and the payload of each missile will result in sheer saturation overwhelming any anti-pellet point defence. 

Of course, you can always use antimissiles.  But the same applies to closing ships.  Anti-antimissiles are easily possible (as are PD dedicated suicide fighters as missile escorts)

And this statement tells you all you need to know about the Aurora demographic

What?  It IS easy.  Anyone who can't do geometry might as well not play.  =P

[Arwyn]

I think that the defense and lethality envelops SHOULD be a bit more "iffy" and not so black and white. Starfire did an excellent job of showing how combat, tactics, and designs changed as the technology shifted (yes it got silly twoards the end, so did SFB).

To that point, anti-missile work, and anti-kinetic work are NOT the same thing.

Missiles are much easier to detect, since they are burning reaction mass and generating heat. Missiles are also relatively fragile constructs. Any beam/missile/kinetic hit is likely to cause significant damage to a unarmored missile. Blinding the missiles tracking or sensors, penatrating the skin and damaging the explosive payload, or causing catastrophic heating will all give a mission kill on a missile.

Kinetic weapons are tougher kills. They are much smaller, much harder to detect, and much tougher. Kinetics are inert bricks, so destroying/deflecting them is much tougher. It would take a lot more energy (kinetic/beam/handwavium ect) to get a mission kill on a lump of metal.

Frag missiles give the shotgun approach like the old torpedo spreads used in WW II. They wont all hit buy something MIGHT hit. Even with that, since Steve has already said that closure speeds will dictate impact damage, turning away from ANY missile shot is going to be a good idea.

For that matter, just to touch on geometry. SHIP geometry would be an interesting issue as well. Realistically, a ship would want to present the smallest possible cross section to a hostile ship to minimize is potential to be hit. For a traditional "rocket ship" this would be the nose and stern of the ship. Both of which are actually bad places to get hit. Bow shots mean your closing, and increased closure rates equals increased lethality. It also means that your presenting more of the ship internals to a penetrating hit, since a bow hit would punch through the length of the ship.

Presenting the stern is the same issue. Shots striking the stern have a lessend closure rate, but increased likelyhood of a maneuver kill on the ship. Penetrating shots will almost certainly wreck the propulsion systems, and also get the plunging fire through the decks of a bow shot.

A flattened wedge or something similar might actually work better, from a broadside perspective, since it would minimize penetration through the decks.

Might be harder to code, but I think realistically, you would see exactly that kind of thing in those ship designs. Presenting minimized cross sections to the enemy would be the rule of thumb when your talking the kind of hitting power these weapons would have.

[procyon]

In a theoretical optimally designed rail gun a solid slug is effectively in free fall and could survive any amount of acceleration. The electromagnetic acceleration is distributed evenly throughout a conductive round as a body force, accelerating every atom in about the same direction at about the same rate. Any compressive/shear forces in the object would be small, sort of similar to how satellites in orbit are constantly accelerating but practically weightless. In Newtonian Aurora rail guns appear to be much closer to their theoretical potential than the modern prototypes of today.

The usual reason high Gs are fatal is that they are resulting from contact forces. The atoms in back are getting pushed into the atoms in front to propagate the force. As a result the inertial forces from the atoms in front trying to stay at rest (or the ones in back trying to stay in motion) generate internal forces compressing/pulling/shearing the object.

Touched on this a few (ok, maybe 30ish...) pages back.  Action/reaction.  You are sending the slug out at a substantial velocity.  Doesn't matter whether it is pushed, pulled, slid, slipped, etc.  It is aquiring a large amount of momentum in a very short period of time.  This is acceleration.
As for it being applied in equal amounts to all the atoms, gravity is the most even force we have.  It will be far more uniform than any railgun acceleration (that I can forsee).  Place a material under a G load in excess of its bearing strength and it will fail.  Check out what happens to bridges that are poorly engineered.
And at the accelerations we may posit for the high end railguns - if you were to mount them in a smaller ship (ie small time of acceleration to acheive velocity), and you may be approaching G levels capable of generating degenerate matter.


And on the matter of the NA demographic, I see that as a compliment.
The fact that my wife thinks that a popular TV show about overly intellectual individuals is based on the people in this thread is completely beside the point...


And on kinetic kill defense...

I and some associates have actually been discussing this one at length.

Modern radar can track lots of objects that don't ever make it onto a screen.  It won't display all the returns from birds, etc, as they don't pass certain parameters.  The displays only show objects moving with velocities exceeding certain speeds/return signatures/etc.  I am not an expert on radar, but I expect the dopler shift on an incoming projectile moving at hundreds or thousands of km/s would give it a rather distinct signature.  How far out you can detect it is beyond me, but it should be obvious if you have an object closing at that velocity.

Problem is stopping something with the kinetic energy of a small nuke. So far the best solution we have come up with sounds more like a karate proverb about using your opponent's strength against them.  The laser hitting a slug would have an easy time striking, but a hard time deflecting enough in the short time needed to stop a hit.  But even a grain of sand far enough from the ship could cause the slug to turn into a ball of plasma - and could stop it.
Missiles would be poor for this as the time to accelerate would be inadequate to reach adequate standoff distance (I think, it depends on detection time).  But a mass driver projectile could be hundreds of meters from the ship firing it.  That would be adequate to disperse the 'energy/blast'.  If a mass driver was to fire - instead of a solid slug - a 'packet' of tiny projectiles of even perhaps a hundredth or less of a gram, it could disrupt the incoming weapon.  Your railgun could also act as its own defense.
The chance of intercepting an incoming slug could be based on the mass of the slug fired by the railgun.  Small slug (fewer projectiles) equals lower intercept chance.  Heavy slug gives a higher chance of successful intercept due to saturation of the target area.  Might not help against a thousand inbounds that will hit your ship, but if the shrapnel has that tight a spread it will be easier to avoid.  If they spread the shrapnel out to better cover a target area, it will be easier to intercept the few inbound projectiles.

It would also make larger payload railguns more useful (perhaps, or at least more versatile) than smaller slug, higher velocity railguns. 

Thoughts.....

So far this is just a concept in the initial stages, and could undoubtedly use some outside thoughts/improvements.  But it is the best we have come up with to stop the one shot kill railgun.

[jseah]

Place a material under a G load in excess of its bearing strength and it will fail. 

Only happens to objects not in free fall.  A uniformly accelerated railgun slug (source doesn't matter) is in free fall while in the tube. 

[procyon]

Free fall is not a free ride.

Check out what the Rouche Limit is.  If free fall was without hazard, then this wouldn't exist.  

Acceleration beyond bearing strength will cause failure.

And it isn't free fall.  The slug is being accelerated by the ship.  How that acceleration is applied is not at issue.  It is undergoing acceleration.  Whether the ship is pushing/pulling the projectile or both, it is applying force to the object to impart momentum.  The projectile will have to deal with this load.


EDIT

But I am willing to 'suspend disbelief' in this case as I love the concept.  Of course if we can make materials with load bearing strengths a million times their own mass, orbital elevators would be easy.

The material would also make some INCREDIBLE armor as the tensile strength would make the armor Steve has listed look puny.  

[UnLimiTeD]

Ultimately, both armor and slugs might be forcefields containing pure energy.^^
Somewhere, not to many billion years in the future, in a galaxy not far from here...

[procyon]

Ultimately, both armor and slugs might be forcefields containing pure energy.^^
Somewhere, not to many billion years in the future, in a galaxy not far from here...

I looked at this and kind of chuckled.

And then I sat and thought about it. Hmmm....

And decided I really kind of like the idea.  Maybe a bunch.

In that the whole physics of force fields is kind of poorly defined (perhaps not a bad thing...), it could solve a lot of problems with the railgun as it stands.  It wouldn't have to contain energy, as the energy could just be the field used to hit a target.

1.  Having a field based projectile would allow unlimited ammo.

2.  Would alleviate the 'looking the other way' that the ammo would have to survive launch.  If it has no actual material component, it won't have to worry about tensile strength.

3. Would not have to detonate on impact.  Could maintain integrity as passing through a ship (or not, however you want it...)

4.  Could be given an arbitrary max range as the field disipates after a set amount of time.

5. May not have to hit with the force of a nuke.  If it only contains so much energy and is a field/wave phenomena - it will only deliver so much energy regardless of relative velocities.

6.  Would be more easily detectable as an active emmission source.

The more I look at this, the better I like it.  Alot.

EDIT

It won't solve the problem of a shrapnel missile, but those missile will take time to get up to speed, should be more easily detected, and more readily destroyed/evaded.  A shrapnel missile won't be a whole lot more dangerous than a nuke.  It pretty much boils down to the fact that if you let a missile through your defense - its game over for that ship...

[Mel Vixen]

Call me stupid but i can only find the "Roche limit" online and it applys to the destruction of planetary bodys by tidalforces from another massive body overcoming the first bodys internal gravity. I dont see how that applies to a Projectile if we assume it would be accelerated evenly where tidalforces (due to the involved object sizes and the nature of gravity) are uneven.

If there is a "Rouche Limit" i would like to have a link to it. I mean i can be wrong too.

You can assume that a railgunslug desintegrates if its accelerates to fast against its own inerta either by overcomming the tensile (drawing) or Bulk (pushing) limits maybe shearing too -this would only happen if you apply the accelerating force in a way that the railgunslug is accelerated unevenly, say by applying the force only to one surface/side/part of the slug. This effect is know from highpower x-bows where the string hitting the arrow/bolts shattered the projectile - because of this people changed to bullets from metal stone and ceramics.

[Marthnn]

Free fall is not a free ride.

Check out what the Rouche Limit is.  If free fall was without hazard, then this wouldn't exist.  

Acceleration beyond bearing strength will cause failure.

And it isn't free fall.  The slug is being accelerated by the ship.  How that acceleration is applied is not at issue.  It is undergoing acceleration.  Whether the ship is pushing/pulling the projectile or both, it is applying force to the object to impart momentum.  The projectile will have to deal with this load.

I find Roche limit has little in common with a railgun slug. The propelling of that slug is analogous to freefall in that we can suppose the force applied is uniform, and not a contact pressure. A bridge is subject to gravitational acceleration, yet is not itself accelerated, since its supports resist the weight of the whole structure (and can fail/break). That's not freefall. In the slug, there's no part that supports the applied acceleration of the rest, so the whole is accelerated without tensile, buckling or shear involved, assuming the railgun is well designed and propel the slug straight out of the muzzle.

With a gun, the bullet is propelled by an explosion applying a pressure to its base surface. If your charge was too big, the bullet could crush itself, not from the acceleration, but from the internal stress applied to its base. Same with a human body in a rocket accelerating too much, the body is pushed by direct contact from the seat and internal organs could be crushed together, since they're not held very well inside the body. That is not the case for a railgun, thanks to uniform force.

Of course, one could argue that the force applied by a railgun to its slug isn't exactly uniform. Then is it significantly localized? And can very high technology improve the uniformity?

[sloanjh]

Of course, one could argue that the force applied by a railgun to its slug isn't exactly uniform. Then is it significantly localized? And can very high technology improve the uniformity?

I think this was the point.  Is the EM force that accellerates a railgun slug applied at the surface, or uniformly throughout the body.  For example, I was surprised to learn the other day that inductive heating depends critically on the skin depth of the material to be heated (not just conductivity/resistivity) - apparently the power absorbtion rate goes like the inverse square of the penetration depth of the radiation.  It makes sense that the same effect would happen in a railgun, since both effects should be due to eddy currents.  So in addition to the physical limit procyon talks about, there might also be a "how hard can I accellerate the slug before the skin vaporizes from the eddy currents" effect too (which is actually almost the same thing).

That being said, I don't think it really matters - I think the physical properties of what exactly is getting accellerated how are the sort of thing to abstract away in the game design - as long as the game mechanics are internally consistent I think this falls into the category of "TN materials have better properties".

John

[Mel Vixen]

The skin evaporating into plasma wouldnt be a problem, the plasma itself would act as conductor and accelrate the (now slighly smaller) slug along the path. Iirc you can have a noncuductive not sabboted slug if you add a piece of cooperwire to its rearend. The wire would naturally evaporate but the projectile would ride on the plasma-arc. Take it with a grain of salt that i cant find the article where i did read that.