Newtonian Aurora

[procyon]

For all drives, there would be some speed over which maneuverability drops (because the engine cannot support such accelerations). This max-maneuver velocity would be low for old generation ships, or later day freighters, higher for military vessels, and much higher for fighters (because of the low m in the above eq).

The degree of change in course bearing will relate to relative velocities.  But actual displacement over a given time span will always remain a function of your acceleration.  Adequate displacement from the incoming weapon (minus it ablility to correct for this) will determine successful intercepts.  A half degree course change that moves you two kilometers or a 15 degree course change that moves you two km will all displace you from a weapon path 2km if performed in the same time frame.  If Steve models the G forces of inherent in the course change necessary by incoming ordinance the 15 degree change is desirable.  If it isn't = displacement will simply be displacement.

But those missiles would move in a straight line, bearing on your ship, no? So, if you can align with them (easy task if you are at rest, almost impossible if you are moving fast, but then, the missiles will have a hard time intercepting you...) and if your antimissile have an area effect (just like enemy missiles), the only thing you need is that your AM "crosses" the enemy missile before it is in range of your ship.

Supposing your AM has the same speed as the missile (but you could adapt the formula), this means you can detect the enemy projectiles at twice their explosion range. But all this only seems to work if you can align your fire with enemy missile path, ie if you are very close to te ship targetted. "sideways" shoots at missiles, on the other hand, would be little more than potshots...

Detection range will be paramount on incoming ordinance.  High enough inbound speed may limit counter fire to direct fire weapons as AMM will not have sufficient time to reach a minimum safe distance from the target.

And depending on how the coding works, I only see a few successful 'head on intercept' attempts against mobile opponents with credible defenses.

But a missile at high velocity (or better = several closing on different trajectories) equiped with detonation laser rods on a passing trajectory could be a difficult target (depending on warhead yield, laser output, and accuracy).  It won't be coming straight at you.  If the coding supports it I would have them veering off on the end of the attack runs.  The missile should be able to rotate on its axis even more nimbly than a ship to aquire a target.  As you pointed out, it doesn't have to worry about inertia for the lasers and can even detonate after it has passed the target.

Depending on relative velocities, trajectories, and ranges these missiles may give precious little opportunity to stop them.

But again, I will have to wait and see what the game supports.

Of course, you could always have your missiles travel in pairs, with one several kms in the lead.  Both with healthy nukes.  The first one set to detonate to stop the incoming AMMs....


EDIT

Have I mentioned lately that I really can't wait to see what is possible, and try it out to see what works....

[UnLimiTeD]

Yeah, you're already dwelling in possible tactics.
I expect Lasers and particle accelerators to be the weapons of choice for "close" range point defense.
Well, we haven't yet gotten any info on what Lasers will be like.^^

[fcharton]

High enough inbound speed may limit counter fire to direct fire weapons as AMM will not have sufficient time to reach a minimum safe distance from the target.

Yes, it means, AMM efficiency will mostly depend on the acceleration they can provide at launch. An AMM should then be a very light missile (acceleration in inversely proportional to weight), with a very large exhaust speed, that can jump to very high speeds in a very short period. Perhaps they should be a mix between a missile and a railgun projectile...

Note that warhead effective range will most certainly be under 1 million kilometres (it should correspond to laser effective range if laser warheads become the norm). If effective sensor ranges are around 50 million km, then, against an inbound missile at 0.5 c, you have a little more than 300 seconds between detection and interception if you want to intercept out of warhead range. An AMM covering a million km in 300 seconds would have an average speed of 3333 km/s. Under constant acceleration, this would correspond to a final speed of 6 666 km/s, or an acceleration of 22 km/s^2, ie 2.2 G.

Note that the use of laser warheads will make laser less efficient as antimissile weapons : if enemy laser technology is on par with yours, by the time the enemy missiles reaches your effective laser range, it is about to detonate...

Francois (check the above maths before you quote them, I'm running away to a meeting, so the figures might be grossly wrong...)

[procyon]

Yes, it means, AMM efficiency will mostly depend on the acceleration they can provide at launch. An AMM should then be a very light missile (acceleration in inversely proportional to weight), with a very large exhaust speed, that can jump to very high speeds in a very short period. Perhaps they should be a mix between a missile and a railgun projectile...

AMM drive efficiency will need to be the best you can get, agreed.  I could see proactive deployment of AMMs from an escort - before you detect incoming ordinance - to be a possible tactic.  Will have to test that one when the time comes.  AMMs with internal sensors set to TCS 1 and good drives with a small nuke could make an effective screen.

Note that warhead effective range will most certainly be under 1 million kilometres (it should correspond to laser effective range if laser warheads become the norm). If effective sensor ranges are around 50 million km, then, against an inbound missile at 0.5 c, you have a little more than 300 seconds between detection and interception if you want to intercept out of warhead range. An AMM covering a million km in 300 seconds would have an average speed of 3333 km/s. Under constant acceleration, this would correspond to a final speed of 6 666 km/s, or an acceleration of 22 km/s^2, ie 2.2 G.

Math good to the G point.  22m/s2 is 2.2G.  22km/s2 is 2200 G.  A wee bit more than I expect my engines to attain for a while.


As I have said, I look forward to this game.  It will put a lot of theories to the test.

[chrislocke2000]

Have to say I can't wait to have a go at this myself. Already started building the brownie points with the wife in the anticipation of some long evenings locked in the study!

Was just having a quick look at the rules again and noticed that the costs in warhead between conventional / nuclear / nuclear laser seem quite small to me and was wondering if these differences should be more pronouced to give players more of a decision to make in the types of ordinance used?

Also, having re-read the rail gun thread I was not sure if Steve was going to be calculating kinetic energy for damage based purely on the exit velocity of the shell or the eventual relative impact velocity when it hits. I'm assuming it's the later with the exit energy just being used to calculate total enegry requirements and cool down requirements.

Just running some numbers I can see that even with a closing speed of just 500kms any shots are going to be lethal: By my calcs that would give an impact energy for a 1 kilo slug of 125k MJ, more than enough to punch through basically any armour and shields and go back out the other side. I'm wondering how that sort of narrow but very high damge will be dealt with for internal systems.

[UnLimiTeD]

What we should actually factor in is slug ablation.
If that slug is 1 kg, and it hits the force shilds of the ship, and possibly some sort of wobble shield on the armor ( I know i would mount some), then shouldn't it degrade somewhat?
If it flies though 20 layers of armor, shouldn't the slug take damage as well?
Still, a 1kg chunk of iron shouldn't damage a ship too harsh, it'll just leave two large holes.
And wreck whatever else it passes.

[fcharton]

Math good to the G point.  22m/s2 is 2.2G.  22km/s2 is 2200 G.  A wee bit more than I expect my engines to attain for a while.

Sure enough! (and thanks, Procyon!)

The calculation scales linearly with incoming speed, which means a missile moving at 15000 km/s would need 220G-capable AAM to be stopped. This is a lot, but it is not a crazy (current day ABM accelerate to more than 100g, and modern electronic equipment can witstand over a thousand G).

I don't know how plausible 2200 G is? More or less than 0.5c missiles? With 2200 G, you'd need something like 500 million km to accelerate a missile to 0.5c, with accelerations in the hundreds, you'd need several billions.

But then, given that such fast projectiles will not be able to maneuver, maybe a better question is : do we really need missiles? or would railguns with explosive ordnance work better?

We'd be back to older models, as artillery becomes  the queen of the space battlefield?

Francois

[UnLimiTeD]

Given that as far as we know, Railguns won't have "real" homing projectiles, for now, the accuracy will drop off drastically.
Missiles will be special delivery vehicles, sure you can create an armored one as a kinetic kill vehicle, but it'll mostly be nuke, shrapnell, or laser rod warheads, all with their special uses.

[bean]

I'm not sure I see your point. You seem to imply that velocity building must take days. I would say this would be the case for freighters and early game ships, but warships would have high G engines (with some form of grav/inertial compensator, which would probably be the main feature of TN technology). Such ships would quickly accelerate to cruise speed (fuel cost being the same) and operate, most of the time, in ballistic mode, ie with engines stopped.

Yes, I am implying that velocity building must take days, for a simple reason.  Steve has not indicated that he's adding any sort of system that would allow tens of Gs of acceleration.  As for cruising, that's not the case.  If you have the delta-V, it makes sense to burn constantly.

Even if high G maneuvers were too risky to be attempted out of battle, you could imagine a high G drive giving a low acceleration. Derivating Tsiolkovski's eq, you get the formula for accelerations (G), as
dV/dt = -v_exhaust/m dm/dt
To reduce acceleration, you could either reduce v_exhaust (which might not be practical in chemical rockets, but is perfectly doable if exhaust are accelerated by a field, as in a ion engine), or reduce mass output. In practice, it just means warships would have much more powerful engines than commercial ships, and probably some kind of anti-grav contraption to allow their crew and frame to sustain the high G delivered by the engine.

Your formula is technically correct, and I do agree that ships could maneuver harder during battle, but not enough, assuming that we are limited to human tolerances.  As for reducing acceleration, you would always reduce mass flow, and, if using something like a Hall Thruster, increase the exhaust velocity. 

For all drives, there would be some speed over which maneuverability drops (because the engine cannot support such accelerations). This max-maneuver velocity would be low for old generation ships, or later day freighters, higher for military vessels, and much higher for fighters (because of the low m in the above eq).

But those missiles would move in a straight line, bearing on your ship, no? So, if you can align with them (easy task if you are at rest, almost impossible if you are moving fast, but then, the missiles will have a hard time intercepting you...) and if your antimissiles have an area effect (just like enemy missiles), the only thing you need is that your AM "crosses" the enemy missile before it is in range of your ship.

Supposing your AM has the same speed as the missile (but you could adapt the formula), this means you can detect the enemy projectiles at twice their explosion range. But all this only seems to work if you can align your fire with enemy missile path, ie if you are very close to te ship targetted. "sideways" shoots at missiles, on the other hand, would be little more than potshots...

Francois

You're ignoring part of the above equation, that is the dm/dt, or mass flow.  Yes, a smaller ship with the same engine will have better acceleration.  This does not mean that fighters are a good idea.
And why is maneuverability so important, anyway?  Yes, at higher velocities, it takes longer to make a 90 degree turn.  However, nobody will actually look at it that way.  If you want to generate a miss with regard to missiles, the only thing going slower does is increase the time it takes for the missile to close with you.  You still build the same side vectors, regardless of velocity.  A higher velocity will give you less time to build the vectors, but that's all. 

[UnLimiTeD]

I suppose everytime someone seriously mentions fighters in discussions about engine thrust, they mean unmanned craft?
That might allow for more maneuverability.

[fcharton]

Steve has not indicated that he's adding any sort of system that would allow tens of Gs of acceleration.  

Tens of G of acceleration are a fact of modern day technology, an ABM has acceleration over 100G, in fact. Ruling them out from manned ships is possible, but the issue will reappear for drones and missiles.

As for cruising, that's not the case.  If you have the delta-V, it makes sense to burn constantly.

Not necessarily. Burning constantly will send you "there" faster, but it will also use more fuel, and might make sudden course changes more expensive. Again, for a cargo ship, on a predefined route, it makes sense, for a military ship on patrol, not necessarily so.

And why is maneuverability so important, anyway?  

Can think of many, but in a nutshell, because maneuverability=acceleration

- In a missile vs antimissile dogfight, better acceleration will always win (and if the incoming missile manages to evade the antimissile, it will need to maneuver back towards its target)
- higher accelerations allow an antimissile to reach its target earlier, which is important if warheads are area weapons.
- In a long range ship vs missile situation, a ship with good acceleration can (perhaps) create a situation where the enemy missile runs out of delta-v, lasting longer may matter
- In a more classical (moving) ship vs ship situation, before you fire a missile, you need to align with the target. Better ship maneuverability will allow for an earlier firing solution, better missile maneuverability will allow for a larger set of solutions.



Francois

[bean]

Tens of G of acceleration are a fact of modern day technology, an ABM has acceleration over 100G, in fact. Ruling them out from manned ships is possible, but the issue will reappear for drones and missiles.

The statement was meant WRT manned ships.  As for drones, I don't see drone ships seriously outperforming manned ships if for no other reason then fleet interoperability.  Missiles are an entirely different matter.

Not necessarily. Burning constantly will send you "there" faster, but it will also use more fuel, and might make sudden course changes more expensive. Again, for a cargo ship, on a predefined route, it makes sense, for a military ship on patrol, not necessarily so.

That depends on how much delta-V you have.  Modern chemical rockets have low delta-V, but relatively high acceleration, so it makes sense for them to burn quickly.  However, there is a limit to how much acceleration a person can handle, and that limit strongly indicates we'll see long term burns to be able to use it.  I'm not ruling out coasting at some point, but I don't expect long coasts to be the norm.
 

Can think of many, but in a nutshell, because maneuverability=acceleration

- In a missile vs antimissile dogfight, better acceleration will always win (and if the incoming missile manages to evade the antimissile, it will need to maneuver back towards its target)
- higher accelerations allow an antimissile to reach its target earlier, which is important if warheads are area weapons.
- In a long range ship vs missile situation, a ship with good acceleration can (perhaps) create a situation where the enemy missile runs out of delta-v, lasting longer may matter
- In a more classical (moving) ship vs ship situation, before you fire a missile, you need to align with the target. Better ship maneuverability will allow for an earlier firing solution, better missile maneuverability will allow for a larger set of solutions.



Francois

All of these are true, but also relative.  You stated this argument by claiming that higher accelerations were needed to make space combat possible.  A ship with higher acceleration has an advantage, yes.  But what that acceleration is is irrelevant.

[procyon]

Have to say I can't wait to have a go at this myself. Already started building the brownie points with the wife in the anticipation of some long evenings locked in the study!

I wish I could say the same thing.  Convincing my wife and kids to put the RPGs and Starfire on hold so I can play is a hurdle I am not looking forward to.  

Also, having re-read the rail gun thread I was not sure if Steve was going to be calculating kinetic energy for damage based purely on the exit velocity of the shell or the eventual relative impact velocity when it hits. I'm assuming it's the later with the exit energy just being used to calculate total enegry requirements and cool down requirements.

Just running some numbers I can see that even with a closing speed of just 500kms any shots are going to be lethal: By my calcs that would give an impact energy for a 1 kilo slug of 125k MJ, more than enough to punch through basically any armour and shields and go back out the other side. I'm wondering how that sort of narrow but very high damge will be dealt with for internal systems.

I am fairly sure he intends to use actually impact speeds, not launch speeds.  I wouldn't think it would be hard to code for, but I am not a programmer.  

The damage modeling for slugs could really use some attention.  My reasons....

At those velocities, unless this slug is made of some incredibly resilient material it won't survive impact intact.  If it could, we need to be using whatever it is made of for armor.  The energy generated will create an enormous amount of heat (depending on velocity at impact) - likely vaporizing the slug and turning it into a violently expanding mass of superheated gas and particles.  It is going to become a bomb.

The slugs fired from the 120mm on our tanks only hits targets at < 3 km/s.  Often less than 2 km/s.  They turn into molten slag on the way through the armor and essentially detonate in the target.  Check the records.  I saw a fair number of enemy vehicles hit by our tanks - the only exit holes were on soft vehicles.

The railgun slugs will likely be hitting at higher than single digit km/s.  The penetrator (if it overcomes the armor) won't be intact.  It will be a 'fireball'.


EDIT

On the thought of a slug hitting a shield, I really don't have any idea what would happen.  I don't really know what the shields are.  If they are some distance from the ship, they may yaw the slug.  This would ruin its sectional density as it struck and profoundly limit its penetration.  If the shields are nearly flush with the ship, then I doubt it makes much difference.

[procyon]

  All of these are true, but also relative.  You stated this argument by claiming that higher accelerations were needed to make space combat possible.  A ship with higher acceleration has an advantage, yes.  But what that acceleration is is irrelevant.

Ok, couldn't resist. 

You don't need ANY acceleration for space combat....

You just can't expect to live very long though...

I apologize.  I'm better now.

[UnLimiTeD]

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?
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.