Nukes, love them or leave them...

[Adrian Laguna]

That depends on how good the enemy sensors are, how much interference you've got, etc. At sufficient range, everything is just a blob as far as optical imaging goes, especially when you consider the fact that the enemy ship probably doesn't have a giant lens for a bow and will be maneuvering itself, with all of the resulting vibration and interference this will generate. You can't assume that every ship will get nice Hubble Telescope pictures of anything it wants.

You could say similar of real life aircraft and their radars. A fighter can't have a big-ass radar on it, there wouldn't be space for the weapons and engines. That's why the airforce went and put their giant radome on a big plane that hangs outside the battle. You just get the space equivalent of an AWACS plane and decoys are unless.

[Darth Wong]

That depends on how good the enemy sensors are, how much interference you've got, etc. At sufficient range, everything is just a blob as far as optical imaging goes, especially when you consider the fact that the enemy ship probably doesn't have a giant lens for a bow and will be maneuvering itself, with all of the resulting vibration and interference this will generate. You can't assume that every ship will get nice Hubble Telescope pictures of anything it wants.

You could say similar of real life aircraft and their radars. A fighter can't have a big-ass radar on it, there wouldn't be space for the weapons and engines. That's why the airforce went and put their giant radome on a big plane that hangs outside the battle. You just get the space equivalent of an AWACS plane and decoys are unless.

And this craft would be immune to attack and therefore have no need to maneuver because ...?

A real-life AWACS plane can do what it can do (which, by the way, is not exactly immune to countermeasure either) because missile range is not that long. If we're talking about these hypothetical long-range missiles that are so advanced that avoidance is really difficult, then the viability of this space version of the AWACS plane is in serious doubt.

[Sidewinder]

The problem with decoys in space is that they have to match the applicable characteristics of the ships they're mimicing fairly well. Same temperature (both the ship itself, and the drive), same radar signature, same optical image, same amount of mass in the drive exhaust. At that point, you've got something with the same size and mass as a real ship.

What about inflatable decoys, which were mentioned in 'Aliens: Colonial Marines Technical Manual'? Cover the balloon with a radar reflective material, and the enemy might think it has the same mass as a real ship.

[Beowulf]

You have failed to address the other points I made Wong. Specifically the with regard to the exhaust.

The problem with decoys in space is that they have to match the applicable characteristics of the ships they're mimicing fairly well. Same temperature (both the ship itself, and the drive), same radar signature, same optical image, same amount of mass in the drive exhaust. At that point, you've got something with the same size and mass as a real ship.

What about inflatable decoys, which were mentioned in 'Aliens: Colonial Marines Technical Manual'? Cover the balloon with a radar reflective material, and the enemy might think it has the same mass as a real ship.

Unless the ship isn't accelerating, the decoy will behave differently. Either it'll accelerate faster than the real thing, or the temperature/mass of the drive exhaust will be wrong. You can tell the mass of the drive exhaust by how quickly it cools down, IIRC.

[Starglider]

Unless the ship isn't accelerating, the decoy will behave differently. Either it'll accelerate faster than the real thing, or the temperature/mass of the drive exhaust will be wrong. You can tell the mass of the drive exhaust by how quickly it cools down, IIRC.

AFAIK this only works for drives that use thermal expansion. Ion engines throw particle beams that have negligable backscatter in the near-vacuum of space, and mass drivers throw cold lumps of metal that don't show up any better than arbitrary space junk.

As for the AWACS spacecraft idea, I would expect lightspeed comms and sensing limitations to be a serious issue if it sits far enough back to be out of missile engagement range (on tactically relevant timescales - waiting for your missiles to complete a one-month transfer orbit to the target isn't terribly useful).

[phongn]

I don't think ion drives will give out enough thrust for a realistic warship, though.

[Darth Smiley]

The whole dreadnaught/gunboat debate is actually dependant on another debate: lasers/point defence vs missles.

The laser / point defense arguement is that a laser armed ship can shoot down missles fast enough and reliably enough that it is not cost effective to even shoot them. The missle arguement is that even if lasers CAN shoot down missles, it only takes one and BOOM!

The problem is that it is very, very, very, dependant on the specific conditions, such as the distance the fleets are expected to fight at, and the maturity of specific technologies. If your universe has torchship drives but mediocre directed energy techs, then lightly armored ships can evade lasers by making random course changes at extreme range while pummeling each other with torchdrive missles (armor is more or less irrelevant, as ANY direct hit is death). One the other exteme, if the best drive you've got is an ion or chemical and you are capable of throwing around hard X-rays, it would be prudent to put several thick layers of heat absorbing armor around your spacecraft (the reflective cloud idea is cost inefficent. For the mass penalty neccessary to carry enough cloud to be effective, your might as well put on some armour)

So: Don't argue about battleship vs gunboat until you argree on a specfic set of technologies.

[Ford Prefect]

The laser / point defense arguement is that a laser armed ship can shoot down missles fast enough and reliably enough that it is not cost effective to even shoot them. The missle arguement is that even if lasers CAN shoot down missles, it only takes one and BOOM!

Clearly then you're just not firing enough missiles.

[Starglider]

Clearly then you're just not firing enough missiles.

At some point your ship becomes a missile rack with an FTL drive and some fuel tanks attached. If a full salvo from that isn't enough to reliably destroy an equivalent mass/cost ship consisting of a mass of laser (or particle beam) turrets, a big reactor and an FTL drive, the missile ship is officially worthless, as the laser ship will then proceed to close and vaporise it. In addition the laser ships will be far less dependent on vulnerable supply ships stuffed with reloads.

[Ford Prefect]

At some point your ship becomes a missile rack with an FTL drive and some fuel tanks attached. If a full salvo from that isn't enough to reliably destroy an equivalent mass/cost ship consisting of a mass of laser (or particle beam) turrets, a big reactor and an FTL drive, the missile ship is officially worthless, as the laser ship will then proceed to close and vaporise it. In addition the laser ships will be far less dependent on vulnerable supply ships stuffed with reloads.

Get your dirty realism away from my Itano Circus! *waves fist*

When it really comes down to it, unless your missiles are really quite small, you can't really spam them up so easily. And really, 'small' might be impossible from the technological perspective of a given universe - in such a missile, you want a high yield, simply to extend the lethal kill radius of the detonation, even with the inverse square law brething down your neck like some sort of asshole. As I understand it, when using nuclear weapons, you can only get a given yield out of a given weight, though I don't recall the numbers, nor whether it applies to both fission and fusion.

Then the question is: 'How small can I make the propulsion for this?' and 'How much fuel can I actually fit into such a small weapon?'.

[Starglider]

When it really comes down to it, unless your missiles are really quite small, you can't really spam them up so easily.

Long-range fire-and-forget missiles may be limited by the cost and size of adequate sensors. Remote-controlled missiles are subject to jamming and fire-control capacity limitations, and probably still need a terminal guidance system due to lightspeed lag. If anything more sophisticated than chemical drives are in use, there's the problem that scaling the starship drive (fusion, antimatter etc) down to fit into a missile may simply be impossible. On the plus side you can run the missile drive in an overload condition, since it only has to last until you hit the target.

If you're trying to overcome firing-rate and range-limited point defences with missile spam, you run straight into the problem of anti-missiles. They can be shorter range than the incoming missiles, so they can be higher acceleration, and they can probably be cheap fully-command-guided missiles instead of expensive fire-and-forget missiles too. The anti-missiles can have nuclear-pumped x-ray-laser or fragmentation warheads to take out whole groups of incoming missiles, and the incomings are unlikely to be able to evade them (they may not even be able to detect them).

The recent discussions on this board that illustrated the technical feasibility of ABM also applies here - and in space the sensing and the interception are both easier. Given equivalent technology it's extremely difficult to make a long-range missile carrying a heavy warhead that can avoid a short-range anti-missile carrying just enough of a warhead to kill the incoming, and you can carry a lot more of the later than the former.

That said missiles might be good in fleet engagements for finnishing off damaged ships that have had their sensors and/or point defences destroyed by laser/particle/coilgun fire.

As I understand it, when using nuclear weapons, you can only get a given yield out of a given weight,

There is a theoretical upper yield for every energy source. For fusion weapons it's about 6 megatons of yield per tonne of warhead mass. For antimatter it's about 20 gigatons per tonne, or 40 if you can get the target to supply the matter (not including the mass of the containment mechanism).

Though of course if you have Macross technology you will be able to fit approximately 840 AMRAAM sized missiles into your F-14 sized space fighter.

[Darth Wong]

You have failed to address the other points I made Wong. Specifically the with regard to the exhaust.

As long as we're assuming perfect sensor data acquisition at any arbitrary range, then yes, your point is unassailable. Is there some reason we should assume this? We're talking about a hypothetical scenario with extreme long-range missiles, aren't we?

[Darth Smiley]

Hmmm.... I forgot about ABMs. Those make things more interesting. In that case, the best 'warhead' for a missile might be 10 more missiles, or a bursting charge. However, these can have thier effectiveness degraded by a Whipple shield. The best option for missle warhead might then be a pumped x-ray laser. This way, the defender is forced to fire while the missle is farther out, lightspeed lag is a problem, and they lack good firing solutions.

Decoys might be useful tactically, but I think Beowulf is assuming a more long term strategic approach. It's certain that you arn't going to be able to hide how many ships you have....given time, eventually the enemy is going to see through the decoys by analyzing the exaust, or very careful inspection. On the other hand, during a long range missile fight, when lightspeed lag becomes a problem, you might be able to confuse a missile's guidance by throwing out a decoy and changing course. The missile doesn't have time to analyze the exaust.

[Beowulf]

You have failed to address the other points I made Wong. Specifically the with regard to the exhaust.

As long as we're assuming perfect sensor data acquisition at any arbitrary range, then yes, your point is unassailable. Is there some reason we should assume this? We're talking about a hypothetical scenario with extreme long-range missiles, aren't we?

The decoy has to have similar, if not identical characteristics as far as temperature, power, velocity (both exhaust and ship), and mass flow, are concerned, to be able to make it hard to distinguish from the real thing. If you've got something large enough to do that, your decoy is already the size of a ship. Those characteristics are hard to fake. Is there, in fact, any reason to assume it's possible?

This scenario doesn't require any specific range or weapon technology. In fact, the scenario is in part to determine which weapon technology is realistic.

[Starglider]

In that case, the best 'warhead' for a missile might be 10 more missiles

If the system bursts late it has the same problem as MIRV against ABM; it won't work because the enemy can hit the bus before it starts dropping warheads. If the submunitions are released early enough for it to work, all you've done is made 10 missiles share a common stage, which reduces your options (you now have to fire them in bursts of ten and they have to share an initial vector) for nothing but a marginal cost gain. That mass would probably be better invested in a gun-launch system to give the missiles a decent initial velocity without forcing them then to share boosters.

[Darth Wong]

You have failed to address the other points I made Wong. Specifically the with regard to the exhaust.

As long as we're assuming perfect sensor data acquisition at any arbitrary range, then yes, your point is unassailable. Is there some reason we should assume this? We're talking about a hypothetical scenario with extreme long-range missiles, aren't we?

The decoy has to have similar, if not identical characteristics as far as temperature, power, velocity (both exhaust and ship), and mass flow, are concerned, to be able to make it hard to distinguish from the real thing.

Again, you are assuming perfect sensors. If you're at such long range that visual images are nothing more than a blob without giant lenses, then I see no reason to assume that you can expect this kind of accuracy with other kinds of sensor. IR sensors are still passive EM band sensors; they're not magic, and they're subject to the same limitations that a visual sensor is. Hell, I don't see why you couldn't confuse the hell out of long-range passive EM sensors by beaming something at them.

If you've got something large enough to do that, your decoy is already the size of a ship. Those characteristics are hard to fake. Is there, in fact, any reason to assume it's possible?

At such long range that a visual image is nothing more than a blob of light, I still don't see why such high resolution should be assumed. At very long ranges, an awful lot of characteristics are inferred by sensor technologies rather than being directly observed. Inference can be fooled.

This scenario doesn't require any specific range or weapon technology. In fact, the scenario is in part to determine which weapon technology is realistic.

You can't separate range from the question of which weapon is most appropriate.

[kinnison]

It seems to me that to make space battleships practical, at least the sort of thing you see in Star Wars, several things are necessary. First is a drive that either doesn't rely on reaction much at all (Bergenholms, stutterwarp from the game Traveller 2300 or possibly the FTL drive from the Dorsai series, or some sort of gravity drive that uses the entire universe to push against) or uses extremely high-velocity exhaust; maybe a plasma/ion drive, nuclear pulse, fusion or even antimatter annihilation. (The second alternative also makes a good weapon - Niven's Kzinti Lesson.)

The second is some sort of extremely high-density power source. Nuclear reactors probably won't cut it - perhaps some sort of antimatter engine, something using a micro-singularity, or more speculatively something using vacuum energy or something else that draws power from subspace/another universe - Culture's Gridfire.

The third depends on whether you are using reaction drives or not. Stutterwarp or inertialess drives don't have this problem. Reaction drives do. Namely, some sort of gravity compensators - so that you can maneuvre without turning the crew into bloody paste. Or maybe an immersion tank - Forever War.

Of course, you also need either missiles with a high yield/mass ratio (and/or one or other of the drives described above) or beam weapons of very high power indeed - or both.

And if you have all this stuff, then you probably aren't going to go to war anyway - as you can get all you need from unhabitated or unhabitable stellar systems. Unless you have some non-practical reason - such as religion or just sheer paranoia.

[Connor MacLeod]

Some thoughts/questions/considerations I've wondered about:

1.) exactly what KINDS of engines are we atlaking about for ships as well as the kinds of accelerations? I'd say that plays a role in fighting

2.) I dont think I've seen much mention of automated/robotic drones instead of human-controlled craft. A robotic drone would be much less prone to acceleration problems (and could save on mass issues a human couldn't.)

3.) "armour" seems to be taken literally where you need to put large quantities of mass in the way of an object (other ideas have been proposed for defense like what Degan proposed, which is kinda like those hypothetical "cold plasma" shields I heard about years ago.) but you could perhaps arrange some ways to allow for mass to be "in the way" in a limited fashion depending on what the ship carries (fuel/propellant/water supplies, etc.) and the type of powerplant/engine.

[Adrian Laguna]

3.) "armour" seems to be taken literally where you need to put large quantities of mass in the way of an object (other ideas have been proposed for defense like what Degan proposed, which is kinda like those hypothetical "cold plasma" shields I heard about years ago.) but you could perhaps arrange some ways to allow for mass to be "in the way" in a limited fashion depending on what the ship carries (fuel/propellant/water supplies, etc.) and the type of powerplant/engine.

You can even use a thin plate and nothing as a armour. Ever hear of a Whipple shield?



(pic from Atomic Rocket, that website roxxors)

[The Dark]

Again, you are assuming perfect sensors. If you're at such long range that visual images are nothing more than a blob without giant lenses, then I see no reason to assume that you can expect this kind of accuracy with other kinds of sensor. IR sensors are still passive EM band sensors; they're not magic, and they're subject to the same limitations that a visual sensor is.

Current off-the-shelf IR sensors could detect the Space Shuttle (not exactly a wonderous warship) out by Pluto. Unless we're suddenly talking thousands of AU as our long range, and sensors no better than late 20th century Earth, detection is not an issue. Resolution won't be great (for a COTS system at hundreds of AU), but it would be sufficient to tell how warm something is, and give a rough estimate of size. Be off on either of them, and the decoy's known for what it is.

Hell, I don't see why you couldn't confuse the hell out of long-range passive EM sensors by beaming something at them.

Because that requires more precise targeting than what you're saying we don't have in the first place. You need to focus sufficient energy on a relatively small area and maintain it long enough to overload the sensor. Instead of trying to differentiate between multiple-meter-long vessels, you're now trying to hit a meter-wide or so spot on a moving vessel.

If you've got something large enough to do that, your decoy is already the size of a ship. Those characteristics are hard to fake. Is there, in fact, any reason to assume it's possible?

At such long range that a visual image is nothing more than a blob of light, I still don't see why such high resolution should be assumed. At very long ranges, an awful lot of characteristics are inferred by sensor technologies rather than being directly observed. Inference can be fooled.

You don't need super-high resolution. There are a few requirements:
1. Overall size similar - not really a problem; inflatable decoys could do it
2. Electromagnetic signature and heat signature similar - requires a power system probably fairly close in peak power generation to simulate power to weapons, ECM, life support, et cetera. It also needs to radiate similar amounts of heat, or IR will spot it
3. Overall mass similar - the exhaust plumes will glow in IR based on the energy and density of the exhaust (as well as doppler shifting the spectral emissions based on velocity of the exhaust). If significantly different, the decoy is obvious. If the exhausts are similar but one vessel moves significantly faster, it's the decoy.

This scenario doesn't require any specific range or weapon technology. In fact, the scenario is in part to determine which weapon technology is realistic.

You can't separate range from the question of which weapon is most appropriate.

In the end, no. But knowing whether spaceship combat will be like submarines or battleships (to use an extremely rough analogy) can serve as a first criterion for eliminating some systems.

[Klempik]

You don't NEED to aim at a sensor to blind it.

Just consider a flash-bang : It doesn't focus on anything, and will blind you neatly.

[Steel]

You don't NEED to aim at a sensor to blind it.

Just consider a flash-bang : It doesn't focus on anything, and will blind you neatly.

Not at 20+m The flashbang gets away with not focusing on anything because it is assumed the targets are close. Why do you think that flashbangs are not used much outside during the day?

In order to blind a sensor effectively you need to stuck a certain intensity of energy into it, and your means for doing that will drop off in effectiveness with inverse square. My laser will be able to blind you from many times further than a flashbang will. So if you want to have a space flashbang, its going to have to be some kind of massive nuke that lights up most of the system to be effective at long range...

[Klempik]

Steel wrote :

In order to blind a sensor effectively you need to stuck a certain intensity of energy into it, and your means for doing that will drop off in effectiveness with inverse square. My laser will be able to blind you from many times further than a flashbang will. So if you want to have a space flashbang, its going to have to be some kind of massive nuke that lights up most of the system to be effective at long range...

Of course but neither do you need a blinding beam with a projected surface the size of the antenna you're aiming at : That's just too much.
I just wanted to illustrate that you don't need pinpoint accuracy to aim a jamming signal.
Most 1st gen jammers work this way and they are very crudely directed toward their targets.