Main Battery as PD?

[someone_else]

Ships carry triple-digit gigawatt to single-digit terawatt scale fusion reactors, which can then be used to charge up capacitors that can then dump the energy into the shields.

You have shielded ships? Did you mention that before? Nevermind, doesn't matter. Btw, ever considered the idea of using inertially-confined fusion engines with MHD generators that can convert the thrust into shipboard power when needed? Like using your car engine as a generator. Saves mass in space as it does on Earth.

So a shielded ship requires sub-kiloton/second firepower, though this is never used on an unshielded vessel unless you have a situation where the ship and every single thing, both living and artificial, on it, must die. Missiles, OTOH, probably require a single-digit gigajoule/second firepower......at most.

So, to put it bluntly, you have what I classify as "overpowered" lasers (fully personal opinion). Short of relativistic impactors, missiles are a waste of mass if you have so much powerful lasers at your disposal.

Mah excel spreadsheet tells me that at 10'000 km from the vessel using 200 nanometer UV light (around the shortest radiations you can still work with with lenses and standard laser stuff) and a main optics (mirror probably) size of 10 meters (still damn fucking big for 2011 tech) you have a spot diameter of 2.4 meters.
Let's pretend that missiles need a gigajoule per m2 to die (their face is one m2), and if you shoot once per second that's a 4.5 gigawatt laser (spot area is 4.5 m2). If you shoot more, like say 10 times per second, it has to be a 45 gigawatt laser.

With the same kind of laser shooting at a missile 100'000 km away you have a spot diameter around 24 meters. Spot area is 452 m2. If you still need one gigajoule per m2 per second you are shooting a 452 gigawatt laser. If you hope that the missile will die even with an order of magnitude less, you can use the same PD laser that instead of shooting 10 times per second shoots once per second 10 times as far.

Say we are shooting at a ship 100'000 km away, with your ship's main gun that hopefully has a bigger optic system, let's say 50 meters so you still have a manageable spot size (although it's a pretty big mirror, will have to be a segmented mirror, decreasing the performance somehow). You said it must be able to shoot in the sub-kiloton range, so let's say it is a 2'092 Gigawatt laser (can shoot 0.5 kilotons once per second or 0.1 kilotons 5 times per second or any similar combination).

At 100'000 km its spot diameter is 4.8 meters, area of 18 m2, so it's dealing 116 gigawatts per m2 if shooting once per second or 11.6 gigawatts per m2 if shooting ten times per second. Or 1 gigawatt per m2 (necessary for missile kill as you said) if shooting 100 times per second.
In all three situations, cooling problems are the same.

If you wanted to optimize it for anti-missile duty you could say 20 shots per second with 5 times the area (a spot size of 10,7 meters of diameter). Still a gigawatt per meter, but now on 90 m2.
Still around same total output, so if you can keep shooting once per second at full power all day without cooling problems, you can keep shooting 20 such antimissile shots per second without cooling problems as well.

It's also a bit of a missile limitation; the missiles can coast for a long time, but a military vessel can use bursts of high-G acceleration to rapidly put on additional velocity and get out of the missile's tracking envelope.

The missile *must* outperform its intended target in acceleration and maneuverability (that is accelerating in different vectors without waiting hours to turn).

The only area where the ship should (massively) outperform the missile is the delta-v, or fuel endurance. (but since it cannot change its speed anywhere as well as the missile, it won't be able to evade unless the missile has been launched from very very far and/or has tiny fuel reserves)

If you don't make it so, makes no sense to use missiles at all.

Ah, I was under the impression initially that you were saying that particle beams suck in general, rather than as PD ordnance.

I said that particle beams suck because the average person I talk to thinks of particle beams as conventional weapons that burn and cut stuff.
The kinds of particle beams that don't suck balls don't leave any scar, but destroy electronics and crew with hard radiation ignoring armor.

At this point, it's mainly because I figured that staging would boost the range of the missiles by having multiple engines that fire, allowing them to get going as fast possible and as far as possible.

Wrong. You waste time and massively increase the risk of a failure fucking up your plan.
Staging wastes time since you have to wait the old stage gets clear of your nozzles before you can ignite the new stage. And that takes some seconds, unless tou place retro-rockets that fire to bring the spent stage away fast (adding mass and chances of failure).

Staging requires cadres of equipment that can fail and doom you. Explosive bolts, dedicated sensors and electronics, cabling, and more importantly loads of engines. If either of these components fail, your missile becomes space trash.

If you just want high performance and fuel isn't an issue, place all the engines together on a single stage, so that even if some fail, you get slightly degraded performance, and not a total fuckup.
If you still like the idea of discarding stuff, use drop tanks. Still useful but not a killer in case of fuckup.

Space missiles in hard-ish scifi should be composed of 2 parts: a booster and a seeker. The booster is a dumb rocket that fires to accelerate the thing towards the enemy, and then is discarded (and maybe blown up to make some nice fragments), the seeker is a guided projectile, with its engines facing sideways, and whose only job is home on target and maybe avoid antimissiles, not accelerate towards it nor avoiding lasers (how?). They have no hope to be particularly fast on their own (around 3-4 km/s) but in various kinds of engagements they can easily reach 10-20 km/s due to the speed difference of the two fleet's spacecraft. They count on not being very big and on very high numbers to do the job.

Of course, in a softer sci-fi where you have powerful small engines that need little fuel and are also so cheap to still make sense on a missile, then you should keep thrusting all the way to the target and gimbal its main engines to change course.

If, however, inherent limits in sensor resolution or gunlaying prevent you from aiming to a precision of a meter, then your defense fire will be 'sprayed' into the volume around the missile anyway, which defeats the purpose of evasion.

The more powerful is the laser, the smaller can be its focusing optics, the bigger will be its spot at the same range.
Since generally optics after a certain size start to look idiotic (regardless of their feasibility) even on km-long Penis-Ships, anything above the few dozens of thousand km from the ship will have a spot size above one meter.

Especially since if the combat is fought at ranges where light speed weapons have significant accuracy problems against a maneuvering target, there is a good chance your main battery weapons wouldn't be hitting the target anyway.

Lol? Hitting something on a more or less constant course is not an issue for a laser.
Spacecraft can only accelerate in a single general direction. Turning them safely takes lots of time (relatively speaking).

[Dwelf]

Lol? Hitting something on a more or less constant course is not an issue for a laser.
Spacecraft can only accelerate in a single general direction. Turning them safely takes lots of time (relatively speaking).

This is an absurd generalisation. Unless there a mass constraints there is no reason that a spaceship cannot accelerate on whatever vector it pleases. Sure this will result in large turning circles if you actually want to change course. The point of evasive manouvers is not to change course it is to provide uncertainty on the exact position of your vessel when the fire starts comming in.

[Simon_Jester]

Can you elaborate why it is the fourth power?

Assuming you know their maximum acceleration.
Distance to their last know position( How old the image is)
Their last known velocity.
How long your processing and targeting takes.

the area of uncertainty should just be a circle with a radius of
1/2at^2

where t is (age of data) + (processing time) + (weapon travel time)

At least that is my understanding of the maths involved.

Yes. Now. Calculate the area of that circle, given that its radius scales with t-squared. Its area will scale with t to the fourth power.

Ignore, for the sake of argument, age of data and processor time- say, you're fighting with 100 km/s railguns, so that the time it takes radar and computers to spot the target is small relative to the time it takes the shots to cross a reasonable distance. If you fire a shot with a time of flight with one minute, the target could potentially be anywhere in a circle (or, more likely, ellipsoid or other more complicated shape) equal in radius to the maximum distance it can run in any given direction in one minute.

If the time of flight is two minutes, the radius of that circle increases by a factor of four, but the area increases by a factor of sixteen.

This becomes a losing proposition very quickly when you're shooting at a target from far enough away that it can sidestep by several times its own length before your shots arrive. World War era navies had this problem with long range ballistic gunfire, with flight times of a minute or two and ships that could turn in considerably less distance than that.

As navies learned from the 1940s on, the easiest solution is a guided weapon- something that can track a target's attempts to evade and defeat them with its own course correction. The other solution, if accuracy is important, is to close to a range such that the enemy can't dodge.

[Dwelf]

Ah that explains the missing step I hadn't though of nesting the equations.

[Simon_Jester]

Ah, I was under the impression initially that you were saying that particle beams suck in general, rather than as PD ordnance.

I said that particle beams suck because the average person I talk to thinks of particle beams as conventional weapons that burn and cut stuff.
The kinds of particle beams that don't suck balls don't leave any scar, but destroy electronics and crew with hard radiation ignoring armor.

This doesn't interact gracefully with the idea of indistinguishable-from-magic energy shields.

If, however, inherent limits in sensor resolution or gunlaying prevent you from aiming to a precision of a meter, then your defense fire will be 'sprayed' into the volume around the missile anyway, which defeats the purpose of evasion.

The more powerful is the laser, the smaller can be its focusing optics, the bigger will be its spot at the same range.
Since generally optics after a certain size start to look idiotic (regardless of their feasibility) even on km-long Penis-Ships, anything above the few dozens of thousand km from the ship will have a spot size above one meter.

What matters is comparison of spot size versus target size versus circular error probable of the weapon. If, at light-second ranges, your beam is ten meters wide but your circular error probably is only a meter or two, then being able to sidestep ten or twenty meters in one second gives a surprisingly good chance of dodging the laser... for a target no more than five meters wide or so.

Big targets need higher acceleration to sidestep, which makes evasion doubly difficult (bigger engine and the required engine power for the thrusters scales with roughly the 4/3 power of the mass of the ship). Weapons whose circular error probable is large compared to their spot size will of necessity be 'sprayed,' so you gain less from small evasive maneuvers: sideslipping by ten meters against a weapon whose shots land at random anywhere within a circle forty meters wide doesn't help you very much. Weapons whose spot size is very large, likewise, because you can't sidestep out of the zone of effect.

Evasion is also, where possible, best combined with electronic warfare- you create a double uncertainty if you can play a shell game with your position and create false images, at least ones good enough to confuse the enemy for a few seconds at a time and over an angular separation measured in microradians.

Especially since if the combat is fought at ranges where light speed weapons have significant accuracy problems against a maneuvering target, there is a good chance your main battery weapons wouldn't be hitting the target anyway.

Lol? Hitting something on a more or less constant course is not an issue for a laser.Spacecraft can only accelerate in a single general direction. Turning them safely takes lots of time (relatively speaking).

This depends enormously on the design. If I'm fighting something five or ten light-seconds away, it is actually possible to dodge the laser, unless everything in the universe has very limited acceleration. This is important to grasp.

Now, if we stick to hard-ish SF reaction drives, accelerations on a large ship will perforce be low enough to make dodging lasers impractical, lateral accelerations more so. But the same constraint may not apply to a missile, or to the many many settings where drive power allows steady acceleration burns at ~1g or more.

[Whiskey144]

Sorry I haven't been able to respond to replies to this thread; I've been out of town. I'll answer a bit of general stuff, and a couple things in particular.

This doesn't interact gracefully with the idea of indistinguishable-from-magic energy shields.

Indeed; to further elaborate on the shielding systems, they are actually more vulnerable to particle beam based weaponry than any other weapon system, due to [whatever technobabble reason to be invented at a later date].

Now, if we stick to hard-ish SF reaction drives, accelerations on a large ship will perforce be low enough to make dodging lasers impractical, lateral accelerations more so. But the same constraint may not apply to a missile, or to the many many settings where drive power allows steady acceleration burns at ~1g or more.

Just to alter/reinforce what I've noted earlier in the thread:

Ships in-setting tend to have 1 G or less acceleration. Military and paramilitary* vessels typically carry either a fusion or antimatter torch or a supply of injectable antimatter, to provide boosts of multiple Gs. Missiles, OTOH, have acceleration on the order of 10-100 Gs, typically dependent on specific details of missile design, such as warhead, kill method, delta-v, flight profile, and target type.

*Paramilitary covers pirates, bounty hunters, unusually-well-armed-independent-traders and mercenaries, in-setting.

General stuff:

The idea that prompted this thread was the possibility of using the main laser battery of a ship as a point defense measure.......but not that said main battery would be the sole or main PD battery. In the case of a long-range missile duel, then the main battery would indeed function in the PD role, while in laser- and mid-range engagements the main battery functions as just that, with secondary, dedicated PD guns taking over.

[someone_else]

Lol? Hitting something on a more or less constant course is not an issue for a laser.
Spacecraft can only accelerate in a single general direction. Turning them safely takes lots of time (relatively speaking).

This is an absurd generalisation. Unless there a mass constraints there is no reason that a spaceship cannot accelerate on whatever vector it pleases. Sure this will result in large turning circles if you actually want to change course. The point of evasive manouvers is not to change course it is to provide uncertainty on the exact position of your vessel when the fire starts comming in.

ehm, excuse me but if you can't turn the nose very fast (unless on very small craft and this isn't the case) and the engines are reaction engines that push the ship, the only "evasion" you can do in laser-shot timescales is variate your forward thrust.

This depends enormously on the design. If I'm fighting something five or ten light-seconds away, it is actually possible to dodge the laser, unless everything in the universe has very limited acceleration. This is important to grasp.

It is also important to grasp that a laser able to still deal damage at those ranges has either a stupidly huge optic system or its output is unreasonably high.

Given that the ranges here are at most 1/3 of a light second (100'000 km), that range is the "sensor blinding range".

But the same constraint may not apply to a missile, or to the many many settings where drive power allows steady acceleration burns at ~1g or more.

Those settings have to use inertial dampeners to have their craft turn at decent speeds to allow anything more than thrusting more/less on the same general direction to allow evasion on multiple vectors in laser-shot timescales at well above the light-second range.

I said that particle beams suck because the average person I talk to thinks of particle beams as conventional weapons that burn and cut stuff.
The kinds of particle beams that don't suck balls don't leave any scar, but destroy electronics and crew with hard radiation ignoring armor.

This doesn't interact gracefully with the idea of indistinguishable-from-magic energy shields.

I don't understand.
You can say the particle cannons actually dump enough energy in the shield to have the same effect of a laser shot of the same power. Which isn't totally wrong, a stream of relativistic particles carries a significant quantity of energy, and only a tiny fraction of it actually interacts with the target (that's the problem high-power ionizing radiation). A shield that stops the whole beam is looking for plenty of trouble.

That is, a 100 gigawatt particle beam has the same effect of a 100 gigawatt laser if you stop the whole beam somehow.

Evasion is also, where possible, best combined with electronic warfare- you create a double uncertainty if you can play a shell game with your position and create false images, at least ones good enough to confuse the enemy for a few seconds at a time and over an angular separation measured in microradians.

ECM works on radars, but not on passive sensors. IR telescopes at this range are pretty good.
Countermeasures (deploying decoys or flares) have a shitty range but may still be able to turn a solid hit in a glancing hit or worse.
Jammers easily give out your position.

[Dwelf]

Lol? Hitting something on a more or less constant course is not an issue for a laser.
Spacecraft can only accelerate in a single general direction. Turning them safely takes lots of time (relatively speaking).

This is an absurd generalisation. Unless there a mass constraints there is no reason that a spaceship cannot accelerate on whatever vector it pleases. Sure this will result in large turning circles if you actually want to change course. The point of evasive manouvers is not to change course it is to provide uncertainty on the exact position of your vessel when the fire starts comming in.

ehm, excuse me but if you can't turn the nose very fast (unless on very small craft and this isn't the case) and the engines are reaction engines that push the ship, the only "evasion" you can do in laser-shot timescales is variate your forward thrust.

Maybe I was unclear. Even if I considered your statement to omit low thrust manouvering thrusters that concept can be scaled up. Unless you only have 1 engine and turn by vector thrust there is no reason that you need to turn a spacecraft to accelerate in any given direction. You can mount drives facing sideways for evasive manouvers. If they are going to increase your survivability more than their equvalent weight in armour then there is really no reason not to do this. So yes your assertion that spacecraft can only accelerate in a single direction is an absurd generalisation.

Even in universes with magical lasers that are effective at over 100 000km you are probably going to want evasive thrusters. They require your oponent to build smarter missiles to handle the uncertainty and prevent concentrated attacks by fleets from outside normal effective weapons range.

[Simon_Jester]

Sorry I haven't been able to respond to replies to this thread; I've been out of town. I'll answer a bit of general stuff, and a couple things in particular.

This doesn't interact gracefully with the idea of indistinguishable-from-magic energy shields.

Indeed; to further elaborate on the shielding systems, they are actually more vulnerable to particle beam based weaponry than any other weapon system, due to [whatever technobabble reason to be invented at a later date].

[Raises eyebrow]

If you aspire to relatively hard SF, this may place you in a grave difficulty, because the required power output for particle beam weapons capable of fatally irradiating a target ship is likely to be lower than the power requirement for laser cannon capable of cutting it in half. A lot lower. In which case battles reduce to "who can kill the other ship with radiation poisoning first," and you get some weird damn designs to limit the effects of bremsstrahlung, I'd think.

Even in universes with magical lasers that are effective at over 100 000km you are probably going to want evasive thrusters. They require your oponent to build smarter missiles to handle the uncertainty and prevent concentrated attacks by fleets from outside normal effective weapons range.

Unless your ship has one hell of a screwy design, though, main engines must still face forward. Lateral acceleration will suck compared to main engine acceleration- worth bearing that in mind.

[GrandMasterTerwynn]

Sorry I haven't been able to respond to replies to this thread; I've been out of town. I'll answer a bit of general stuff, and a couple things in particular.

This doesn't interact gracefully with the idea of indistinguishable-from-magic energy shields.

Indeed; to further elaborate on the shielding systems, they are actually more vulnerable to particle beam based weaponry than any other weapon system, due to [whatever technobabble reason to be invented at a later date].

[Raises eyebrow]

If you aspire to relatively hard SF, this may place you in a grave difficulty, because the required power output for particle beam weapons capable of fatally irradiating a target ship is likely to be lower than the power requirement for laser cannon capable of cutting it in half. A lot lower. In which case battles reduce to "who can kill the other ship with radiation poisoning first," and you get some weird damn designs to limit the effects of bremsstrahlung, I'd think.

Worse, one would think that the laser would be harder to stop. Particles can be deflected (though you may incur an x-ray bath, depending on the degree of deflection) much easier than a laser. You could postulate a shielding system that can absorb lower-frequency lasers, such as UV, visible light, and IR; but a x-ray or gamma-ray laser would just whip right through it with only modest attenuation (though it is difficult to envision building a gamma ray laser, since at the energies required, the act of lasing would destroy the lasing medium; or the tactical utility of one, given how deeply-penetrating gamma rays are. Mind you a x-ray laser is only slightly easier to build. At least one can be built with a big enough free-electron laser, but one would need over three kilometers worth of accelerator (or elf magic) in order to do it.)

Even in universes with magical lasers that are effective at over 100 000km you are probably going to want evasive thrusters. They require your oponent to build smarter missiles to handle the uncertainty and prevent concentrated attacks by fleets from outside normal effective weapons range.

Unless your ship has one hell of a screwy design, though, main engines must still face forward. Lateral acceleration will suck compared to main engine acceleration- worth bearing that in mind.

One could build a giant saucer ship and stick powerful engines all along the brim. Of course, it only provides decent lateral acceleration in whatever plane the brim happens to be on. And linear acceleration will be limited to whatever one of the brim motors could produce. Though, for high enough velocities, tangential accelerations will produce correspondingly smaller changes to the ship's velocity vector.

[Whiskey144]

If you aspire to relatively hard SF, this may place you in a grave difficulty, because the required power output for particle beam weapons capable of fatally irradiating a target ship is likely to be lower than the power requirement for laser cannon capable of cutting it in half. A lot lower. In which case battles reduce to "who can kill the other ship with radiation poisoning first," and you get some weird damn designs to limit the effects of bremsstrahlung, I'd think.

I should probably have been more specific; particle beam weapons are extremely effective against the handwavium shields.......but not so much against bare hulls. In-setting, minor surface ablation (like, leaving some scorch marks) is usually what happens to a ship's hull endures a particle beam strike. Given enough time, the beams can dump sufficient energy to cause small......I forget the term, but it's where there's shallow 'cuts' dug into the hull. You won't have penetration, but there'll be minor surface ablation and perhaps a small amount of molten particulate.

Worse, one would think that the laser would be harder to stop. Particles can be deflected (though you may incur an x-ray bath, depending on the degree of deflection) much easier than a laser. You could postulate a shielding system that can absorb lower-frequency lasers, such as UV, visible light, and IR; but a x-ray or gamma-ray laser would just whip right through it with only modest attenuation (though it is difficult to envision building a gamma ray laser, since at the energies required, the act of lasing would destroy the lasing medium; or the tactical utility of one, given how deeply-penetrating gamma rays are. Mind you a x-ray laser is only slightly easier to build. At least one can be built with a big enough free-electron laser, but one would need over three kilometers worth of accelerator (or elf magic) in order to do it.)

Interesting.......especially since I had been thinking that the average military warship carries between two and four spinal guns; an anti-shield particle beam, an "interdiction" xraser, and perhaps a railgun for surface bombardment. Any gun could be duplicated in mounting as necessary.

One could build a giant saucer ship and stick powerful engines all along the brim. Of course, it only provides decent lateral acceleration in whatever plane the brim happens to be on. And linear acceleration will be limited to whatever one of the brim motors could produce. Though, for high enough velocities, tangential accelerations will produce correspondingly smaller changes to the ship's velocity vector.

I think that this reinforces Simon's statement about "screwy designs".

[Simon_Jester]

One could build a giant saucer ship and stick powerful engines all along the brim. Of course, it only provides decent lateral acceleration in whatever plane the brim happens to be on. And linear acceleration will be limited to whatever one of the brim motors could produce. Though, for high enough velocities, tangential accelerations will produce correspondingly smaller changes to the ship's velocity vector.

For fire control purposes (and evading fire control), what matters is absolute acceleration, not ability to change the direction the ship is going. Hitting a target that travels at 50 km/s in a straight line is, for a sufficiently advanced gunnery setup, no different from hitting one that stands still... and hitting the same target when it's apt to start sidestepping at two gravities is equally difficult in either case.

I should probably have been more specific; particle beam weapons are extremely effective against the handwavium shields.......but not so much against bare hulls. In-setting, minor surface ablation (like, leaving some scorch marks) is usually what happens to a ship's hull endures a particle beam strike. Given enough time, the beams can dump sufficient energy to cause small......I forget the term, but it's where there's shallow 'cuts' dug into the hull. You won't have penetration, but there'll be minor surface ablation and perhaps a small amount of molten particulate.

[blinks]

That seems entirely backwards to the way the physics ought to behave. What is your reasoning for how this works?

[Whiskey144]

That seems entirely backwards to the way the physics ought to behave. What is your reasoning for how this works?

It was my initial thought of the weapon "balance", if you will, inspired by a game I played. However, I am totally open to alterations of that particular aspect.....but particle beams are still going to remain premier anti-shield weapons.

[Simon_Jester]

...Why?

I mean, when you decided which weapons were most effective against what, did you actually know what the weapons did? What kind of forces can act on a particle beam, or on a laser? Or did you just arbitarily decide that "weapon type A" would be good for X, and "weapon type B" would be good for Y, without giving any thought to how?

[Whiskey144]

I mean, when you decided which weapons were most effective against what, did you actually know what the weapons did? What kind of forces can act on a particle beam, or on a laser? Or did you just arbitarily decide that "weapon type A" would be good for X, and "weapon type B" would be good for Y, without giving any thought to how?

I'm going to be honest and say that no, I didn't really think over what each weapon did other than some superficial aspects. My main preference for particle beams being good at anti-shield stuff is that it's somewhat of a refreshingly uncommon idea; AFAIK, the only setting that does it is the one in which I drew the inspiration from.

However, I'll reiterate again that I'm totally open to suggestions on weapon effectiveness tweaks.....more so than I specified above, at this point, considering the fact that I'd need to come up with some kind of technobabble reason that the shields are more vulnerable to particle beams than any other weapon type.

[someone_else]

You can mount drives facing sideways for evasive manouvers. If they are going to increase your survivability more than their equvalent weight in armour then there is really no reason not to do this. So yes your assertion that spacecraft can only accelerate in a single direction is an absurd generalisation.

Ok, what kind of performance you think is good for evasion in this case?
I thought anything less than a torch was useless.
I tend to assume that a real torch drive is going to have a significant size or it melts itself. Handwaving can change that, but it's a brain-bug of mine , please excuse me.

They require your oponent to build smarter missiles to handle the uncertainty and prevent concentrated attacks by fleets from outside normal effective weapons range.

Missiles will easily home on you unless your ship has more preformance than the missile (and then one asks why are you using a missile at all). Firing engines will actually make the homing easier since now there is a HOT spot to ome onto.

Particles can be deflected (though you may incur an x-ray bath, depending on the degree of deflection) much easier than a laser.

Even more or less relativistic particles like a low-power cosmic ray? Those aren't stopped even by the Earth's magnetic field if I'm not totally wrong.

particle beam weapons are extremely effective against the handwavium shields.......but not so much against bare hulls.

As long as they also kill all the crew and computers relatively near the shot with a massive dose of radiation (the people drop dead on the spot), that's how a high-powered particle beam would work.

Given that they are very penetrating, if shooting on a shield (that stops everything cold or it's pointless in this case) they dump their whole beam power on the shield, if shooting on an unsheilded vessel, the energy is dispersed over meters of armor depth or dozens of meters of pressurized compartments (more if the power is much higher). At very high power levels you may be able to melt minor stuff along the way in the beam's path well below the armor.

If you swap the Main Laser with a Main Particle Cannon, and manage to have a 1000 GW beam instead of a 2000 GW laser, you can blanket a 1 km-diameter spot with 500 grays (50000 rads) and kill anything in a very good depth.
200-300 g/cm2 of TVT that means the beam will be reduced to 10% the impact power after it traversed 2.5 or so meters of suitable shielding like plastics or 8 meters of average ship interior, but that's still 50 grays (500 rads) and dangerous for people. Having a metal armor would make it become an x-ray shower that none wants.

[Dwelf]

In this case your going to gain little so I'd probably be aiming for something in the order of 0.1g for evasive manouvers. You probably have over a minute of missile travel time to provide uncertainty. Against the lasers not so useful, as many of us have said there simply isnt enough time.

Yes missiles will easilly home in on a ship but the smarter the missile is the more expensive it is to produce.
If your target cannot evade at all you use rockets they are dumb no computers, no sensors.
If your target has minimal evasion you use a missile with a communication unit and some manouvering thrusters. A central ship/ships can provide reusable sensors and computation.
If your target has enough evasion to make sensor and transmission delay matter or effective coms jamming. You have to put the sensors and computers on the missiles.

These options will get progressively more expensive to produce. This would be a logistics concern but bankrupting your oponent is still a legitimate tactic.
You are also aiming to have enough evasion to make the missiles with bomb pumped weapons enter your effective point defence envelope. It's sort of a magic numbers thing but having at least some seems to make alot of sense to me.

Even in universes with magical lasers that are effective at over 100 000km you are probably going to want evasive thrusters. They require your oponent to build smarter missiles to handle the uncertainty and prevent concentrated attacks by fleets from outside normal effective weapons range.

Unless your ship has one hell of a screwy design, though, main engines must still face forward. Lateral acceleration will suck compared to main engine acceleration- worth bearing that in mind.

I am well aware that the acceleration available for evasion will most probably be lower than your primary drive cluster. You could possibly get ~50% power for evasion without the design getting too screwy. A tripple or more engine clusters at the rear of the vessel each one of which can be rotated 90 degrees so they face oposing directions latterally and matching thrust along the front half of the vessel. It really depends on the universe to how practical that is but not getting hit does wonders to your survivability. It would also probably make your engineers cry due to the various combinations of forces the design now needs to handle. I'm not saying this is the golden combination but it doesnt seem too screwy to me.

[Sarevok]

Missiles are useless against a torch ship except at very short ranges (less than few hundred kilometers). Any further and the missile will never catch up to the ship.

[Whiskey144]

Missiles are useless against a torch ship except at very short ranges (less than few hundred kilometers). Any further and the missile will never catch up to the ship.

Then you obviously haven't been paying much attention to the thread, because the missiles have acceleration on the order of 10-100 Gs.

While ships are limited to a several-second "dash"/"sprint" acceleration of up to 10 Gs......but are generally limited to 0.01-0.1 Gs.

As long as they also kill all the crew and computers relatively near the shot with a massive dose of radiation (the people drop dead on the spot), that's how a high-powered particle beam would work.

I think I can make that work pretty well.........most ships have minimal human crew, instead having humanoid robotics fulfill most functions. Rather silly, I know, but the systems used in-setting tended to be designed for human use, while only "recently", in-setting, have cheap, relatively-sophisticated robotics been able to be fielded.

Given that they are very penetrating, if shooting on a shield (that stops everything cold or it's pointless in this case) they dump their whole beam power on the shield, if shooting on an unsheilded vessel, the energy is dispersed over meters of armor depth or dozens of meters of pressurized compartments (more if the power is much higher). At very high power levels you may be able to melt minor stuff along the way in the beam's path well below the armor.

?

Particle beams don't do super-penetration to shields in-setting; due to [to-be-invented technobabble reason] they deplete shields faster than any other weapon. But otherwise, I'm pretty sure everything else in your statement applies. Very useful and interesting.

If you swap the Main Laser with a Main Particle Cannon, and manage to have a 1000 GW beam instead of a 2000 GW laser, you can blanket a 1 km-diameter spot with 500 grays (50000 rads) and kill anything in a very good depth.

At what range would this occur, though? Also, a terawatt of power is about the total of an average frigates power generation......such a "death-star beam" (in-setting at least) would require mounting on a battleship or dreadnought.

OTOH, it also make building such ships fairly desirable, I suppose. 'Course, I already planned for both types.......though I am going a different route in that dreads are WMD deployment and hard-target siege platforms, with fleet combat being a (very) secondary function....they hold their own, and can even dominate a fleet engagement below a certain size, but a full-on battlegroup in wartime will be able to either run away or stalemate the dread.

200-300 g/cm2 of TVT that means the beam will be reduced to 10% the impact power after it traversed 2.5 or so meters of suitable shielding like plastics or 8 meters of average ship interior, but that's still 50 grays (500 rads) and dangerous for people. Having a metal armor would make it become an x-ray shower that none wants.

Would having, say, a "mixed" armor scheme be desirable? Wherein there's a layer of anti-radiation shielding (perhaps similar to plastics), and underneath it, a metal plate scheme?

[Sarevok]

Missiles are useless against a torch ship except at very short ranges (less than few hundred kilometers). Any further and the missile will never catch up to the ship.

Then you obviously haven't been paying much attention to the thread, because the missiles have acceleration on the order of 10-100 Gs.

While ships are limited to a several-second "dash"/"sprint" acceleration of up to 10 Gs......but are generally limited to 0.01-0.1 Gs.

My bad.

But how do the missiles manage to create and sustain such acceleration ? What kind of engines are they using ?

[Whiskey144]

But how do the missiles manage to create and sustain such acceleration ? What kind of engines are they using ?

At this point, all I'll say is "magic torch drives". But that's more to do with the fact that I'm in-between drive solutions ATM.

[Simon_Jester]

Missiles are useless against a torch ship except at very short ranges (less than few hundred kilometers). Any further and the missile will never catch up to the ship.

Then you obviously haven't been paying much attention to the thread, because the missiles have acceleration on the order of 10-100 Gs.

While ships are limited to a several-second "dash"/"sprint" acceleration of up to 10 Gs......but are generally limited to 0.01-0.1 Gs.

My bad.

But how do the missiles manage to create and sustain such acceleration ? What kind of engines are they using ?

A solid fuel rocket is perfectly capable of sustaining an average acceleration of ~100 g for several seconds. See also the HIBEX experimental project for further investigation into the subject.

Granted, these are intrinsically short-legged missile designs,. I suspect one could work out staging schemes which allow you to use the solid fuel stages at the most critical phases of the missile's flight path while relying on lower-thrust, longer-lived engines for other phases.

Development of extremely high-acceleration missiles has been more or less a dead letter for the last thirty years, so the records set in the '60s and '70s haven't really been surpassed as far as I know. But it's not unreasonable to posit rockets of this type, or a more advanced iteration of the type, as viable space-to-space missiles for torch drive ships. At least, no more unreasonable than positing the torch drives themselves.

Extremely advanced solid fuel rocketry also helps with the problem of surface-to-orbit spacelift- if you can build super-SRB units, it makes getting heavy things outside the atmosphere, where the drive can be used safely, a lot easier. This is used in some nuclear pulse propulsion (Orion) concepts- use SRBs to heave the thing to high enough altitude that you can start lighting off the nukes. It would also work for other kinds of torch drives, or for lofting heavy components of a torch drive ship into orbit.

[Simon_Jester]

Even more or less relativistic particles like a low-power cosmic ray? Those aren't stopped even by the Earth's magnetic field if I'm not totally wrong.

They may not be stopped, but they're bent into deranged curlicues.

To take an example, the Earth's magnetic field at the surface of the planet is strong enough to take a beam of electrons traveling at 0.2c and bend it into a surprisingly small circle. Try the math and see for yourself.

That's the thing about cosmic rays; they don't actually travel in straight lines because they have to pass through so many ambient magnetic fields. It's one of the big obstacles to particle astrophysics- you can't really tell where in the sky a given charged particle came from, not without a full map of the magnetic fields between here and there. And with the exception of the sun, no such maps exist for cases where 'here' is the Earth and 'there' is a star or anything.

If you swap the Main Laser with a Main Particle Cannon, and manage to have a 1000 GW beam instead of a 2000 GW laser, you can blanket a 1 km-diameter spot with 500 grays (50000 rads) and kill anything in a very good depth.
200-300 g/cm2 of TVT that means the beam will be reduced to 10% the impact power after it traversed 2.5 or so meters of suitable shielding like plastics or 8 meters of average ship interior...

Disturbingly, that armor material (which is taking about a megawatt per square meter of charged particle flux) is absorbing about 90% of the beam energy... or about 900 kW per square meter of shielding material -> 300 to 400 kJ dumped into each cubic meter per second. That could get damaging, if it's kept up long enough.

but that's still 50 grays (500 rads) and dangerous for people. Having a metal armor would make it become an x-ray shower that none wants.

Though a sufficient depth of metal will also stop the X-rays. There's a limit on how much material a given wavelength of X or gamma rays can penetrate, after all.

Missiles are useless against a torch ship except at very short ranges (less than few hundred kilometers). Any further and the missile will never catch up to the ship.

That depends on the engagement profile and the missile drive performance relative to the torch ship.

In a meeting engagement (two torch ships closing head on) missile barrages are likely to be very effective, because the target is almost guaranteed to end up somewhere in the volume your missiles can physically reach. He's already heading straight for you; all you have to do is throw missiles down his throat.

In a crossing engagement (torch ship crossing another torch ship's base course, give or take a bit of fudge factor), the situation is more difficult- you probably still have a window in which your missiles can hit the target, but it's a lot smaller and it's easier for the enemy to fake you out by throwing your missiles into an area he isn't planning to go.

In a stern chase ("follow that torch ship!"), missiles are least effective, because a typical missile drive would be relatively short endurance but high-impulse.

To take an example, a Sprint missile (developed for ABM work) gets to about 3 or 4 km/s in about five seconds of very very high-acceleration boost. A torch ship running at 0.1g would need an hour or so to develop the same amount of delta-v. This creates a pretty large window in which the missile could overtake the ship.

[Whiskey144]

Disturbingly, that armor material (which is taking about a megawatt per square meter of charged particle flux) is absorbing about 90% of the beam energy... or about 900 kW per square meter of shielding material -> 300 to 400 kJ dumped into each cubic meter per second. That could get damaging, if it's kept up long enough.

Hmm........ Would similar results, albeit requiring more dwell time/peak power/closer range, be attainable with a beam of, say, between 200 and 500 gigawatts?

[someone_else]

Particle beams don't do super-penetration to shields in-setting; due to [to-be-invented technobabble reason] they deplete shields faster than any other weapon.

I wasn't clear. The shield stops the whole beam cold. But the beam's energy must go somewhere. And that means the effect on a shield is similar to that of a similarly-powered laser.
Then, when the shield is down, there is super-penetration.

At what range would this occur, though?

Similar to lasers. Once the particle beam is relativistic, the drawbacks disappear. Too fast to spread anywhere before hitting the target.

Would having, say, a "mixed" armor scheme be desirable?

Yes, but not for the reason you say.
You need rad-shielding to stop particles and something above to protect this layer from lasers. If the rad-shielding layer is destroyed, particle beams can shoot through and ruin your day.
Also something to cool the rad-shielding is a good idea.

X-rays are generated if you have metal before the particle shielding, and inside the ship when the particle beam hits metallic structures.

That's the thing about cosmic rays; they don't actually travel in straight lines because they have to pass through so many ambient magnetic fields

I think you are confusing them with solar wind. Solar activity can boost particles up to 1/3 of lightspeed with CMEs, while cosmic rays are between 40% and well above 99% c. On average they don't give a shit about Earth's magnetosphere and ram the atmosphere. There isn't a so huge flux of them though, so they don't do a lot of damage.

If you want to deflect them you must be able to generate a field stronger than Earth's. Which is silly.

Hmm........ Would similar results, albeit requiring more dwell time/peak power/closer range, be attainable with a beam of, say, between 200 and 500 gigawatts?

You must decrease the spot size, since what matters is the mw/m2 of radiations you're dumping in it.
In that case for a 500 GW thing you still want a 1mw/m2 beam which means you have an area of 500'000 m2, which is a 800-meter-diameter spot just as deadly as the bigger one, albeit a bit smaller.
With the same calc, the 200 GW will have a spot diameter of around 500 meters.