Physically plausible explanation for missile based space combat?

[GTOM]

I've done some calculations.
At first glimpse, yes it sounds very nice, that with missiles you can attack way outside laser range...

On the other hand, based on molar heat and weight of titanium, it looks like to me, that actually melting down a kg projectile only requires a few MJ... while boosting it to only 10km/s requires scale more power. That shows that even with the low efficiency of lasers (especially vs reflective armor) actually taking out the missile from a safe distance requires lesser power than sending a long range missile, that can track a manuevering target.

I looking for a plausible explanation to justify the roles of missiles and agility to dodge shrapnels...
I have listed a few things that can be the weakness of laser defence, my question is, what could be the main explanation that sounds plausible from the viewpoint of physics and engineering?


Cooldown time : While we already have TW lasers, but what i read about National Ignition Facility, it looks like they need hours to cool down after a shot.
Is there any hope that it could change without some unobtanium?


Fragile mirrors : You need large mirrors to focus a beam precisely.
After they heated by the shot they might be damaged by a much lesser laser?
In this case, the lasers main role could be simply weaken the defence systems (either with a long range duel, or just after the first wave of missiles reach a distance of a few thousand km) while kinetics still have a big role.


Jamming : it requires lesser energy than taking out an armored target (30 fighters, but they are so small we can't track them!)
On the other hand it could be countered by narrow band filtering (although that also filters out much of the heat signs...) or erecting lots of small probes.
Although the main ship could use active radars (that isn't face toward the enemy ships jammers) to find theese targeting probes also.

 

[LURCH]

How about firing time? Right now, the only airborne lasers powerful to be useful have to be chemical lasers. As I understand it (the tech details are all pretty classified), they fire once and the chemicals are depleted, then you have to return to base and refill. For the same amount of mass and room, you could carry dozens of kinetic weapons.

Also, are you writing about near future or far?

 

[GTOM]

Not THAT far future, no starships and stuff like that, but i imagine interplanetary spacecraft to have fusion reactor (I don't know whether theoretically it is more efficient than a nuclear one, or simply the fuel is cheaper? Or maybe mixed fission and fusion fuel.) and reach voyage speed on the scale of 100 km/s.
Also a number of orbital combats with proper orbital speed around Earth and Moon and other celestials.

Well i thought about electrically powered lasers, probably large capacitator banks.
Maybe free electron lasers, but i don't really thought about W40k scale multiple km-s ships.

 

[GTOM]

Hmm, i read ADAM (Area Defense Anti-Munitions) needed almost 30 sec to eliminate a speedboat. It was written that it was actually reinforced rubber...
That sounds not a bad justification that they are still so pretty weak.

 

[Decimator]

Regarding missiles, keep in mind that missiles can carry long-range warheads. Both bomb-pumped lasers and shaped nuclear warheads are options. With either of those, the missile doesn't need to impact the target.

 

[GTOM]

Good idea, although IMHO that would take away one of their great advantage, concentrated unstoppable impact damage.
But i thought fighters have such systems to use them against point range defence before delivering kinetic kill payload.

 

[Decimator]

Personally, I think a spear of nuclear inferno counts as concentrated unstoppable damage, even if it isn't an impact.

 

[GTOM]

Ok, i just want to avoid a nuclear war, while using nukes in space isn't the same as on Earth, but still, eventually they would use them on Earth too, if international agreements and things like that wouldn't stop them.

 

[Decimator]

Depends on if its a total war situation or not. If a faction is launching nukes at populations, then their missile submarines are just as likely as their spacecraft , if not more so.

I guess the real question here is are all the factions Earth-based? How far into the future are we talking?

 

[GTOM]

One is Earth and Mercury based, the other is Mars and asteroid belt based, the third is Earth based.
The second and third have a coalition against the first.

My ultimate justification for not going nuclear, because the first one couldn't destroy all asteroid colonies, while the other ones could destroy every vital infrastructure on Earth and Mercury also have only a half dozen cities.
So till the very last moment, the first one hopes that planetary defence and surface troops and the rescue fleet from Mercury will be enough.

 

[Decimator]

I don't quite understand. You have a faction of Earth and Mercury, a faction of Earth, and a Mars and asteroid belt faction?

 

[GTOM]

Yes, and if things were gone nuclear, only that one that is scattered on the asteroid belt, they have a good chance to survive.

 

[GTOM]

http://en.wikipedia.org/wiki/Plasma_stealth

Hmm i read that one, that says plasma can swallow incoming radiation. Can such method be possibly used as laser shielding? (Or bigger reflectivity instead of swallow?)

Otherwise i thought about a basic broadband metallic mirror as armor, and you can also rotate constantly in space.

 

[GTOM]

http://en.wikipedia.org/wiki/National_Ignition_Facility#Driver_laser

" Previous devices generally had to cool down for many hours to allow the flashlamps and laser glass to regain their shapes after firing (due to thermal expansion), limiting use to one or fewer firings a day. One of the goals for NIF is to reduce this time to less than four hours, in order to allow 700 firings a year.[23]"

Why can't they cool it down faster with liquid nitrogen or helium?
Is that slow cooling applies to any other high energy application (particle accelerators, coilguns) or just lasers have this bottleneck?

 

[QuantumPion]

If you are talking about realistic space combat, keep in mind ships in orbit may be thousands of miles apart with completely different orbital periods. Lasers require line of sight and have limited range due to beam spreading. Also, if you are being lased, you can probably easily tell where it is coming from and counter-attack.

Missiles have unlimited range, do not require line of sight, and can be guided to the target. A small missile coated with radar absorbing material would be very hard to detect to avoid or shoot down. And it would be nearly impossible to determine the source of the missile if it is internally guided and changes its orbit after launching.

I suspect realistic space combat would be more akin to submarine warfare than anything else - stealthy ships stalking each other and using torpedoes to attack indirectly.

 

[Ryan_m_b]

Missiles have unlimited range, do not require line of sight, and can be guided to the target. A small missile coated with radar absorbing material would be very hard to detect to avoid or shoot down. And it would be nearly impossible to determine the source of the missile if it is internally guided and changes its orbit after launching.

The problem with missiles is how you actually get them from A to B. Sure they have unlimited range but how much fuel can you actually pack in? If you pack a lot in then its mass will go up limiting its thrust, making it far easier to destroy. Whilst one might be hard to detect when powered down when it activates its propulsion it will be very easy to see (thanks to IR sensors). Also if you're assuming lasers are powerful enough to be an effective weapon then you've automatically got a pretty good point defence. Given that it's difficult to see how a missile would be effective.

I suspect realistic space combat would be more akin to submarine warfare than anything else - stealthy ships stalking each other and using torpedoes to attack indirectly.

Except a craft that constantly has to be kept at habitable temperature is going to shine like a beacon on any reasonable IR detection system. So no stealth.

 

[GTOM]

I introduced hibernation mainly to reduce life support costs, but reactors still generates lots of heat, no relativistic, interstellar travel etc, active radars can be also used, they can build forests of recon, so i decided its harder and challenging to compare the whole situation to a strategic board game.
Of course distance means that even a cargo ship with ion thrusters have good chance to outmanuever a missile, or finish its course before the missile gets close unless it is launched from a fast ship - then the ship needs a proper attack vector, landing place. I consider fusion powered long range missiles unviable, you don't build such a thing to be single use.
(Well i think they upgraded even cheaper 10km/s delta-v rockets with some nuclear heat propulsion to attack drones in order to offer the possibility of multiple missions and attack behind cover.)

On the other hand, unlike land combat, high velocity missile shrapnels can still kill a ship, like shotgun pellets kill a duck (i expect ships made mostly of light material) - they can be dodged, but you can't dodge a barrage.

However i still wonder, what would be the best bottleneck of laser defences?
Cooldown, recharge when they put on a ship that have electric propulsion?
Range limited to a few hundred kilometers?
Tracking problems when faced with laser jammers?
High reflectivity broadband mirrors, spin around axis?
Fragility of focusing mirrors?

 

[Ryan_m_b]

On the other hand, unlike land combat, high velocity missile shrapnels can still kill a ship, like shotgun pellets kill a duck (i expect ships made mostly of light material) - they can be dodged, but you can't dodge a barrage.

Why not? Even if you made a complete circular screen of high velocity shrapnel a kilometre wide after traveling 1000 kilometres with a spread of just 1 degree your screen would now be spread over a thousand square kilometres. Double that and it's four thousand square kilometres. By the time this gigantic screen has reached a light second it's spread over an area equivalent to twice that of Africa. Just randomly placing yourself rather than even trying to dodge said shrapnel it would still be likely your survive as the chances of being hit would be 65 million to 1.

Seems like it would be pretty easy to dodge that. Even if you did try to make your shrapnel as RADAR and LIDAR proof as possible I suspect it still wouldn't be impossible to spot some coming your way and get out of the path.

However i still wonder, what would be the best bottleneck of laser defences?
Cooldown, recharge when they put on a ship that have electric propulsion?
Range limited to a few hundred kilometers?
Tracking problems when faced with laser jammers?
High reflectivity broadband mirrors, spin around axis?
Fragility of focusing mirrors?

Cooling lasers doesn't seem like it would be difficult given that the technology for rapid interplanetary travel is probably going to involve some cooling technology. Furthermore lasers are much more efficient in space thanks to the lack of blooming. I don't understand what you mean by laser jammer so can't comment there. If you mean something that can blind all your sensors I doubt such a thing would be possible, seems like it would be easy to defend against by simply filtering the direction the source is coming from (and it the missile itself is the source then it's a nice fat target). Reflective surfaces only work against certain wavelengths and even then nothing is 100% reflective. The enemy could either repeatedly shift wavelengths and/or pump enough energy that the small amount damages the mirror making it no longer reflective. As for focusing mirrors that doesn't seem to be much of a consideration for laser's today, even the ones that are entering military service.

This might be useful as it outlines some of the challenges of laser technology being tested for the US navy: http://www.theengineer.co.uk/military-and-defence/in-depth/your-questions-answered-laser-weapons/1016249.article

 

[GTOM]

"Cooling lasers doesn't seem like it would be difficult given that the technology for rapid interplanetary travel is probably going to involve some cooling technology."

I think we already know many things about cooling, why does a TW laser needs so much cooldown? (link above)


I read the article, well, one commenter thinks they are over optimistic, of course on a ship with electric propulsion many present issues can disappear.

"Even if you made a complete circular screen of high velocity shrapnel a kilometre wide after traveling 1000 kilometres with a spread of just 1 degree your screen would now be spread over a thousand square kilometres."

The point is to deliver the shrapnels close enough, like with anti-air missiles.

An attack missile has to withstand laser punisment until gets close enough.

"and it the missile itself is the source then it's a nice fat target"
If they make a IR sensor capable to track something from 1000km, won't it be blinded by a sudden IR flash?

"Reflective surfaces only work against certain wavelengths and even then nothing is 100% reflective. The enemy could either repeatedly shift wavelengths and/or pump enough energy that the small amount damages the mirror making it no longer reflective."

Above i saw that polished aluminium can reach 85% reflectivity over a wide UV and visible band, and IR lasers scatter more.
Of course it won't be laser proof, the point is to buy enough time to reach close enough, and closing speed will be pretty high.

Do you suggest some magitech laser protection should be employed?
TV trope and LOHG had the idea to use some non solid armor held magnetically to prevent drill through.

 

[QuantumPion]

The problem with missiles is how you actually get them from A to B. Sure they have unlimited range but how much fuel can you actually pack in? If you pack a lot in then its mass will go up limiting its thrust, making it far easier to destroy.

The missile does not need much thrust at all. Just enough to change its orbit to get an intercept. It does not need thrust to intercept its target, just to change its orbit and then coast until intercept at high speed. For example, A 200 kg missile with a 50 kg payload (and Isp=250 s) would have over 3 km/s of delta-V, plenty to make large orbital changes.

Whilst one might be hard to detect when powered down when it activates its propulsion it will be very easy to see (thanks to IR sensors). Also if you're assuming lasers are powerful enough to be an effective weapon then you've automatically got a pretty good point defence. Given that it's difficult to see how a missile would be effective.

The missile would only need to activate propulsion on launch to achieve the desired intercept orbit. Cold gas thrusters may be used to make corrections en route. A laser would have to be enormously powerful to destroy it in the short time between detection and interception. We're talking about relative velocities in the km/s range.

Except a craft that constantly has to be kept at habitable temperature is going to shine like a beacon on any reasonable IR detection system. So no stealth.

While true that you cannot stop all IR emissions, a craft with a low aspect ratio that is well insulated would be impossible to detect unless it was close enough. I don't know what distance "close enough" is quantitatively but it would be invisible up to some finite distance.

 

[GTOM]

"For example, A 200 kg missile with a 50 kg payload (and Isp=250 s) would have over 3 km/s of delta-V, plenty to make large orbital changes."

With solid fuel? As far as i know liquid chem fuel has exhaust veolcity of 4-5 km/s, nuclear thermo around twice.

I though the closing speed will be at least 10 km/s. If the ship takes a proper attack course, 100 km/s.

"While true that you cannot stop all IR emissions, a craft with a low aspect ratio that is well insulated would be impossible to detect unless it was close enough."

I wondered about redirecting heat with liquid helium and magnetic cooling, although redirecting generates more waste heat and the mass of the apparatus decrease delta-V, so its viability is questionnable.

 

[QuantumPion]

With solid fuel? As far as i know liquid chem fuel has exhaust veolcity of 4-5 km/s, nuclear thermo around twice.

I though the closing speed will be at least 10 km/s. If the ship takes a proper attack course, 100 km/s.

An Isp of 250 s is reasonable for a solid fuel or monopropellent rocket.

Earth escape velocity is around 11 km/s so the fastest closing speed for two objects in orbit would be 22 km/s if they were going in opposite directions head-on. 100 km/s would be well in excess of solar escape velocity.

 

[GTOM]

I thought most battles will be in the asteroid belt, 100km/s could be reasonable with ion thrusters, fusion reactors.

 

[Decimator]

While true that you cannot stop all IR emissions, a craft with a low aspect ratio that is well insulated would be impossible to detect unless it was close enough. I don't know what distance "close enough" is quantitatively but it would be invisible up to some finite distance.

Insulating is exactly what you don't want to do. Your missile will cook. After thrusting, you need to cool your missile down to near 3 Kelvin to blend in with the background. Until you do that, your missile is easily tracked, and its orbit plotted. Once the enemy plots the missile's orbit, they can track it by any wavelength, not just IR, since they know where to look. And how well do cold-gas thrusters work at 3K?

For reference, if your missile's cross section is half a meter squared, and you cool it down to 30K, the enemy will be able to detect it out to 8.5 Mm.

 

[GTOM]

For reference, if your missile's cross section is half a meter squared, and you cool it down to 30K, the enemy will be able to detect it out to 8.5 Mm.

If they know exactly where to look, and can have a long enough exposition time, which is the case, if they spotted the missile launch, its delta-V is way more limited than the ships delta-V, that is also limited.

Well, i assume that it would be too much magitech to avoid IR and radar based detection at very least 100.000 km, however i don't think lasers could do much damage in that distance, vacuum self focusing isn't plausible in foreseeable future.

http://adsabs.harvard.edu/abs/2007SPIE.6726E..15F

 

[GTOM]

I wondered about mass efficiency.

If a FEL has a 60% efficiency, and the reflective armor (aluminium golden ceramite whatever layers) have 80% efficiency, its an overall 12% efficiency.
If a nuclear thermo thruster has a 80% efficiency, and a mass ratio of 3, then it has an overall efficiency 26%, that twice the laser efficiency...

If the reflectivity can hold on till the attack drone covers the laser range i don't think its more than few hundred or thousand kilometers.

 

[GTOM]

Regarding missiles, keep in mind that missiles can carry long-range warheads. Both bomb-pumped lasers and shaped nuclear warheads are options. With either of those, the missile doesn't need to impact the target.

Is there anything that suggests, that nuclear shaped charges could be effective?
http://forums.spacebattles.com/threads/crazy-idea-atomic-shaped-charges.149558/

 

[Decimator]

Is there anything that suggests, that nuclear shaped charges could be effective?
http://forums.spacebattles.com/threads/crazy-idea-atomic-shaped-charges.149558/

They're part of Project Orion, so yes.
http://www.projectrho.com/public_ht...hp#id--Nukes_In_Space--Nuclear_Shaped_Charges

 

[GTOM]

While it is classified stuff, so one can only guess, but on other threads, they wrote, this didnt bring too good results, they couldn't achieve too much directivity... a nuclear explosion destroy any material that could shape the explosion, x-rays and gamma rays can't be reflected easily, they won't be coherent to focus them with lenses neither. Also big focusing stuff can be damaged from a bigger distance.
So while this sounds good theoretically, but WWII German mega cannons also sounded good theoretically.

(IMHO if those tests were so successful they would have announced, we have this, so you really shouldn't mess with us.)

 

[Khashishi]

If missiles are maneuverable enough, they couldn't be shot down until they are close enough to the target that the blast wave or shrapnel would cause damage anyways. Space missiles will move very fast, so the explosion will continue to move in the direction the missile was traveling and could still destroy the target.

If the missile steers around semi-randomly, then there's no way for a laser to know where to aim.

 

[GTOM]

If the missile steers around semi-randomly, then there's no way for a laser to know where to aim.

But the laser arrives almost instantly, well focusing the beam to a single location is more troublesome, the first countermeasure against it is spinning.

 

[novaprime]

Fire them electromagnetically with a rail gun style system. The missile wouldn't be hot, no friction or exploding gases to eat them. The missile passively scans for the target emitting nothing trackable. When the missile decides it's close enough to the target it activates its own stored fuel and accelerates to a much higher velocity for a short burn. Think it it as throwing a bullet before it self ignites. If it misses it just stays dark.

The idea that it's silent and undetectable till it's too close to dodge. After all if the missile isn't seen to can't be targeted by lasers. If you want the missile could start using whatever radar equivalent you want on final approach. And since you said most your fights are going to be in the asteroid belt, there's plenty of junk to clutter up attempt to find the missiles.

-Oh and railguns are real, the military already has several experimental models that work. They're just not practical at the moment.

 

[GTOM]

Fire them electromagnetically with a rail gun style system. The missile wouldn't be hot, no friction or exploding gases to eat them. The missile passively scans for the target emitting nothing trackable. When the missile decides it's close enough to the target it activates its own stored fuel and accelerates to a much higher velocity for a short burn. Think it it as throwing a bullet before it self ignites. If it misses it just stays dark.

The idea that it's silent and undetectable till it's too close to dodge. After all if the missile isn't seen to can't be targeted by lasers. If you want the missile could start using whatever radar equivalent you want on final approach. And since you said most your fights are going to be in the asteroid belt, there's plenty of junk to clutter up attempt to find the missiles.

-Oh and railguns are real, the military already has several experimental models that work. They're just not practical at the moment.

But won't the electromagnetic flux heat up the projectile, or the gun itself, that heats the missile?
(Otherwise i think, they will use active radars as well against cold projectiles.)

 

[Ryan_m_b]

Presumably the action of a rail gun firing would be noticeable and the missile would be hot as it leaves the tube (might not be any air resistance but the magnetic force is going to add heat). Given that it seems like it would be trivial to have your tactical awareness software plot the speed and course of the missile. Even if it cooled to the background temperature of space and was perfectly radar invisible your computer would know where it is. If you've got laser weaponry accurate to within thousands of kilometres you could destroy it long before it became an issue.

 

[newjerseyrunner]

If I were living in the not too distant future, where missions to Mars / moon / asteroid belt are common, but no starships yet, I'd build my weapons entirely in space, maybe a single launch to send up some advanced computers that can't be produced on site. It would also be very simple in design, if I had automated drones producing them, I'd want them pumped out quickly, that way if half of them get destroyed on their way to the target, many still hit and they'll be so destructive, I'd win anyway.

Think about NORAD. Right now, it's impenetrable. It was designed so that the Soviet Union could pummel it with nuclear weapons and it would stay standing. The energy of the bomb is reflected off of the mountain. It's literally in the heart of a mountain, no nuke or antimatter bomb could affect it.

A million tons of steel hitting the mountain a hundred thousand miles an hour is a different story. My war machine would orbit the Earth very high, maybe even orbit the moon. The guidance system, controls... everything would be deep inside millions of pounds of iron that's been harvested from asteroids. Containing a powerful, liquid hydrogen and oxygen rocket, using water also gathered from space. Your lasers wouldn't be able to cut through that, even the atmosphere couldn't destroy it. It's so heavy that by the time it's detected and can be shot at, even the most powerful weapons would only shove it a little off course, and it's shell would protect the guidance system, allowing it to correct pretty much up until it enters the atmosphere and can't navigate anymore. Once it's hit the atmosphere, it'll obliterate anything it hits.

KE = mv^2, double the speed, quadruple the yield.

 

[Ryan_m_b]

In most space warfare fiction the combatants are quite distant. If that's the case then conventional weapons seem rather useless. Unguided kinetic weapons can be easily tracked and dodged, guided weapons shot when they're in range, beam weapons might not be able to be tracked but minor random course changes would make it extremely unlikely to be hit at range.

The issue then is that combatants would have to get close to fight. Let's say they have beamed weapons: the closer they are the more real time their information is and the likelier your laser will hit the target. But that works both ways, getting closer means your enemy is more likely to hit you.

Enter the combat drone. It's basically a laser weapon with guidance systems. You launch a bunch of these towards your enemy (could launch them quite fast then have them use their propulsion as needed) and along the way they make minor course changes to avoid fire from the defender. The closer they are the more often they figher at the target. You might loose a few but with enough you should hit your target without exposing your own ship.

Of course the best defence against this would be to launch your own drones back. Battles in this case would comprise of ships staying well outside each other's effective weapon range sending waves of drones at each other. Where those drones clash you hope your weapons and software is good enough to ensure you've still got a large enough force heading towards the target.

A notable limitation is that space is vast. If your fictional technology verges on the hard science those drones aren't going to be carrying enough fuel to go long distances fast (more fuel might help but increases weight so slows acceleration). So there's a window of engagement where it makes sense to launch drones, closer than that you open yourself up to fire and further away your drones will take to long to get there and the enemy could just run away.

 

[GTOM]

You wouldn't care about coherence, intensity and data transmission rate limit the range.

Neglecting small prefactors, the angular spread of a laser beam is at least (wavelength)/(telescope radius). At a distance of d, the laser beam has a width of d times the angle, so the fraction of light hitting the receiver is $$\left(\frac{(receiver~radius) \cdot (telescope~radius)}{distance \cdot wavelength}\right)^2$$

I have tryed to do the math.
Had the following results so far :
so assume 10 MW reactor for 100 ton ship (yeah i know not diamond hard... that applies to the rest as well, but i want to have it something common with reality)
25 km/s exhaust velocity. (e^2 mass ratio for 25km/s for rocket with deceleration)

Calculate with base mass for simplicity : 0,032 kg / s mass ejected from rocket.
800 pushing power 0,008 m/s2 acceleration.

Reach full speed during 40 mil km (so constant speed up and down till Mars when it is closest to Earth) during a month, so two-three month from Earth to Mars.

Laser power only MJ/sec.
10m focusing mirror (while a 100m mirror sounds good, but keep it cool after multiple shots...)

At a 1000 km able to focus at 3cm with 300nm UV-B laser.

10% efficiency versus (SF) titan-mirrorium armor.

Around 2000 C for melting titan armor.
1MJ/10/2000 mol titan, 100g.

So a 3cm spot 3cm thick, it is more than 100g

So to kill the striker craft with a single shot distance smaller than 1000km needed.

30km closing speed for fighter (25+5 save 5 for return in case of intercepting a not so well defended convoy)
during that, laser could burn 3kg titan, and even if striker craft shatters, shrapnels still quite dangerous.

(Assumed 1 arcmin spread. With 30m rocket cross-section, 1/100 of mass would hit, and it is enough...)If mothership would like to support landed troops with laser, with atmospheric swallow, and 100m mirror, and much bigger output... I think it still needs to be closer than 100.000 km to efficiently attack armored targets, so get into a range, where it can be attacked even from surface launched missiles.

 

[Artribution]

Thermonuclear missiles, when detonated, flood local space with such extreme levels of heat, light, EM waves and particle radiation that sensors are effectively jammed, rendering an enemy blind and helpless. A swarm detonation of such weapons around an enemy formation can maintain the sensor-blinding effect continuously, putting even a large fleet out of action. Humans have a term for the sensor-jamming effect: nuclear blackout.

 

[GTOM]

Thermonuclear missiles, when detonated, flood local space with such extreme levels of heat, light, EM waves and particle radiation that sensors are effectively jammed, rendering an enemy blind and helpless. A swarm detonation of such weapons around an enemy formation can maintain the sensor-blinding effect continuously, putting even a large fleet out of action. Humans have a term for the sensor-jamming effect: nuclear blackout.

I still don't like the idea that every goon would throw nukes in space. I think a good kW laser jammer could do the sensor black out thing, or at least reduce targeting accuracy.

https://books.google.hu/books?id=ANEM6nI3tosC&pg=PA196&lpg=PA196&hl=hu#v=onepage&q&f=false

According to it, skirt jamming (jam with not exactly same frequency) could require 60dB jamming/signal or more. That is a million times more than the signal.
So at a distance of 10.000km if reflected or emitted signals are scattered well (inverse squre law) it could be able to do the trick. If lots of probes emitted, use the lidars shaded from enemy jammers to find them.

Probably striker craft should be UFO shaped? (spin, and a sharp edge at the middle, to scatter the beams more)

 

[Artribution]

Well, in this scenario, I don't have any idea how the enemy's scanning devices work. But a nuclear blast (or many nuclear blasts) is generally good because the intensity and wide range of emissions interferes with almost everything, from masking a spacecraft 's heat signature to interfering with radar waves and magnetics. On top of that, it destroys unshielded electronics. And blackout is a known effect in nuclear strategy, so it's good if you want something non-speculative.

Another thing worth mentioning is that nuclear warheads can be improved by sheathing them in different materials that add to their effects. For example, they could be made to scatter radar-absorbing particles over a wide radius for improved jamming efficiency, and such particles could linger for some time.

 

[Ryan_m_b]

If you're close enough to deploy nukes and shine jamming lasers on their sensors you're close enough to kill them, or be killed by them. It's difficult to have these sorts of discussions without a setting to discuss it in, complete with available technology.

 

[GTOM]

If you're close enough to deploy nukes and shine jamming lasers on their sensors you're close enough to kill them, or be killed by them. It's difficult to have these sorts of discussions without a setting to discuss it in, complete with available technology.

I think i gave much info with my calculations, but i gladly give more, what would you like to know?
At this point, while i don't know too much about sensors or astronomy, i don't clearly see why the jamming range has to be so close to kill range, they don't have to exactly focus on the sensors.
With a distance of thousands of kms, and inverse square to the signals, i would think it is like blind someone with a reflector, who has a night-vision google. Burn the skin require much bigger power.

 

[Artribution]

If you're close enough to deploy nukes and shine jamming lasers on their sensors you're close enough to kill them, or be killed by them. It's difficult to have these sorts of discussions without a setting to discuss it in, complete with available technology.

Nukes (call them fusion disintegrators if you want to be all sci-fi) can be launched from as far away as another planet. The final stage could be very small and very hard to track without an engine burning, and the stage before that could actually serve as a useful decoy. I agree we can't really come to a decision without some understanding of the technologies available, but we can speculate about physically plausible explanations.

 

[GTOM]

The final stage could be very small and very hard to track without an engine burning, and the stage before that could actually serve as a useful decoy. I agree we can't really come to a decision without some understanding of the technologies available, but we can speculate about physically plausible explanations.

Interesting idea, that stage as a decoy, yes launch range is near unlimited vs stationary target.

So, summarize things.

Basic setup : prolonged war for the asteroid mines, with multiple parties, (privateers included) I would say at at least hundred years have passed since they started to colonize other celestials.

Technology available : everything that exists now + fusion rockets (i gave details about them in calculations post) i think it would be illogical not to have at least a MJ output laser with so much power on board, some new alloys (the titan-mirrorium armor i talked about) hibernation (manned spacecraft not much more expensive than unmanned, general distrust in decision making AIs due to one party's cutting edge in robotics, hacking) drone fighters, neural interfaces (human factor still worth mentioning in drone operating) advanced high-thrust low specific impulse drives for striker craft (I can think about nuclear-thermo)

Most likely war situations are attacking cargo convoys (with frigates and privateers) and overtake mines (that is cover based combat)
I think even cargo ships should have lidars against a meteor (even if a hit is an unlikely event) and shielded electronics vs cosmic rays.
Restrictions : orbital bombardment of settlements is war crime (while Earth's gov is pretty corrupt, they won't overlook that one - that would mean even politicans couldn't be safe) I barely see any reason why would employing nukes were a different category.

 

[Artribution]

I don't see why using nukes in space would necessarily be considered a war crime. We're talking about combat between military spacecraft . Would anyone care if they blew each other up with nuclear missiles instead of photon torpedoes? It's the same result either way: a big flash of light ensues, and the offending spacecraft disappears.

Also, thermonuclear devices have all kinds of applications for asteroid mining.

And your story reminds me of a highly underrated classic.

 

[GTOM]

I don't see why using nukes in space would necessarily be considered a war crime. We're talking about combat between military spacecraft . Why would anyone care if they blew each other up with nuclear missiles instead of photon torpedoes? It's the same result either way: a big flash of light ensues, and the offending spacecraft disappears.

Also, thermonuclear devices have all kinds of applications for asteroid mining.

And your story reminds me of a highly underrated classic.

Thanks for the link, sounds interesting. :) (Although now i don't really have time for gaming.)
Use nuclear bombs for mining? Isnt it a problem, that the sorroundings will be contaminated by really nasty isotopes? Otherwise in my setting in majority of cases mining corps war against eash other too (i would describe it space feudalism)

Still, let's have a megaton explosion at the distance of 10.000 km. So energy released is on the order of 10^15 J. Apply inverse square law, 10^7m, 10^14 on square, so energy density on ship will be around 10J/m2.
If a 20 KJ jamming laser focus on whole ship with 30m diameter density will be around 30J/m2. And it can be operated in continuous mode. (The point would be turn off everything but the crudest sensors not much more sensitive than human eye, to cause targeting problems).

Even if the nuke is total black, and even have liquid helium vs IR detection, if the enemy has any guess about attack direction, they can send some small probes forward, and detect the shadow of the nuke.

 

[Artribution]

But:

1. A laser will only jam a target's light and heat sensors. Sensors that work on other principles would be unaffected.
2. If the jammed target is part of a larger formation (a fleet of manned spacecraft or just one spacecraft with a surrounding network of drones) the jamming laser and its source will be visible to them.
   
3. If the jammed target is in contact with the other nearby spacecraft (or drones) as part of a tactical computer network, it's possible even the 'jammed' spacecraft could ignore the jamming by using another spacecraft 's sensors.
4. A laser would have more limited range than a swarm of missiles and (unlike a missile) firing a laser requires getting close enough to expose your own spacecraft to risk.
5. A missile can evade, unlike a laser.
6. A missile can go around asteroids and dwarf planets, unlike a laser.
7. A missile swarm can shut down their engines and act as an orbiting minefield.
8. Missiles have a continuous mode, too—we call it launch all the missiles.
   
9. Near-future technologies might very well allow a small missile to be practically invisible (active camouflage) and transparent to radar/EM/laser detection (plasma stealth). Those are both areas of active research.
10. If jamming lasers are so much better, is there any reason a missile can't carry a short-range laser of its own, along with other ECM?

 

[Ryan_m_b]

A missile cannot evade a laser point defence at close range. It can randomly change course and junk but the closer it gets the smaller the envelop of possible locations it could be in, thus more chance that a laser shot into that envelop will hit it. At 10,000km a laser burst only takes 30 milliseconds to cross the distance.

As for stealth space is huge so hiding round planets or moons will rarely be available. Not to mention the enemy will see you coming on the way out. And there is no stealth in space. You might be able to hide yourself to visual and radar but you can't hide your heat signature. Even running cold won't help. If you fire a missile it will be hot as it leaves, the enemy could see it and their computer automatically plot it's course. If it did turn off its engine and cool down its last known position and speed will make it easy to shoot down.

Regarding jamming if you need to precisely hit their sensors then they can evade you by dodging, random course corrections and rolls. That means you have to food an area which just energetically doesn't make much sense on the scales involved in space. If you're close enough that the light takes fractions of a second to find its target you're close enough for them to just shoot you.

 

[GTOM]

But:

1. A laser will only jam a target's light and heat sensors. Sensors that work on other principles would be unaffected.
2. If the jammed target is part of a larger formation (a fleet of manned spacecraft or just one spacecraft with a surrounding network of drones) the jamming laser and its source will be visible to them.
   
3. If the jammed target is in contact with the other nearby spacecraft (or drones) as part of a tactical computer network, it's possible even the 'jammed' spacecraft could ignore the jamming by using another spacecraft 's sensors.
4. A laser would have more limited range than a swarm of missiles and (unlike a missile) firing a laser requires getting close enough to expose your own spacecraft to risk.
5. A missile can evade, unlike a laser.
6. A missile can go around asteroids and dwarf planets, unlike a laser.
7. A missile swarm can shut down their engines and act as an orbiting minefield.
8. Missiles have a continuous mode, too—we call it launch all the missiles.
   
9. Near-future technologies might very well allow a small missile to be practically invisible (active camouflage) and transparent to radar/EM/laser detection (plasma stealth). Those are both areas of active research.
10. If jamming lasers are so much better, is there any reason a missile can't carry a short-range laser of its own, along with other ECM?

1. Other types of sensors, like radar? We have radar stealth.
2-3 yes to give enough energy to all observers in the area, sure don't make it easier. :(
4. Well, i have no problem with the expose your own spacecraft thing, but it is more fun to read about missiles burst, closing in etc.
5. ?? Why should a beam evade? (FTL senses is outside the limit of human science for my setting)
6. Yes an important part in asteroid mine capturing (well, the limit between a really smart missile and a drone fighter is blurred)
7. That minefield part vs cargo ships sound interesting.
8. They should definitally try to overwhelm defences in squadrons or swarms.
9. I will read more about it.
10. No such reason, although the entire launcher ship can have much more power output.

If you're close enough that the light takes fractions of a second to find its target you're close enough for them to just shoot you.

I calculated earlier that 10m focusing mirror, 1000km distance, UV-B laser, MJ output still not enough for instant kill if i apply the (more or less futuristic) heat resistant broadband mirror armor.

 

[Artribution]

A missile cannot evade a laser point defence at close range. It can randomly change course and junk but the closer it gets the smaller the envelop of possible locations it could be in, thus more chance that a laser shot into that envelop will hit it. At 10,000km a laser burst only takes 30 milliseconds to cross the distance.

If the laser beam is meters in radius and the missile is traveling at hundreds of relative meters/second, it could be very hard to hit. And a hit might not be enough—it might need some sustained contact to burn through. And if it's not just one missile but a salvo of missiles, you might be in trouble.

Also, once the first salvo detonates (even if still quite far from the target), the light/heat/EM/particle interference generated will make salvo 2 that much harder to hit.

As for stealth space is huge so hiding round planets or moons will rarely be available.

It seems that this story takes place in the asteroid belt. What I meant by "go around asteroids" was that if you're orbiting Ceres and you want to destroy something orbiting on the far side, you can't fire a laser because it won't have enough range and it can't go around the planetoid, but a missile can. And, depending on the orbit, the engine burn required to line up an orbital intercept can be done while the target is still on the far side and unable to detect your heat signature. You can just coast from there. (At least this works in Kerbal.)

And there is no stealth in space. You might be able to hide yourself to visual and radar but you can't hide your heat signature. Even running cold won't help. If you fire a missile it will be hot as it leaves, the enemy could see it and their computer automatically plot it's course.

If they have line of sight, yes, but they might not. Or they might be very far away, potentially orbiting another planetoid. Missile range is quite far.

edit:

Why should a beam evade? (FTL senses is outside the limit of human science for my setting)

I mean the laser weapon itself can't evade very well, because it has a giant beam of light coming out of it.