Detecting nuclear warheads amidst a missile swarm

[Sarevok]

In nBSG the Cylons mixed nuclear warheads amidst swarms of conventional missiles. The Galacticas had sensors capable of isolating them and prioritizing their destruction.

Would it be possible to do the same with real world sensor technology ? Say for your super duper expensive space battleship comes under missile spam. Amidst the cheap explosive missiles is one special missile with a fission warhead. Your armor can take a beating from normal missiles but the nuke would leave the ship destroyed or crippled. Can your point defense identify and kill this high value threat ?

[Chris OFarrell]

To the best of my knowledge, there is no sensor technology mounted on a platform that could detect the kind of subtle radiation given off by a nuclear missile that exists, at least beyond point blank 'we're already way in the fireball here!' range...

[Purple]

One thing to consider is the missiles mass thou. Having not watched NBSG I can't tell what kind of missiles the other ones were. But if the nukes are relatively heavy in comparison to the others (especially if the others are just decoys, than it would make perfect sense) than their engines will need to produce more power to achieve the same performance as the normal ones. And this can be tracked and detected quite easily.

[Traveller]

Maybe such a thing might be barely possible if the nukes in question were so poorly shielded and leaky that you couldnt help but notice them. All space-going craft should have radiation sensors, but to detect cosmic radiation that could be a threat to the crew and or equipment, could equipment like that detect even the leakiest nuke against all that? not sure. But if that were the case, it would probably be fatal just being in the same ship with them.

In nBSG I wondered how they would pull that off, given that space itself is saturated with background radiation in all directions. Not to mention both sides capships are a source of radiation themselves. And if they can detect an incomeing nuke, wouldnt that imply that they would also be able to detect the cylon nukes still in there launchers? In many hard sci-fi novels in ship to ship combat, its just a given that everyones missles are nukes and everyone plans accordingly, ie dont get hit.

[Sarevok]

One thing to consider is the missiles mass thou. Having not watched NBSG I can't tell what kind of missiles the other ones were. But if the nukes are relatively heavy in comparison to the others (especially if the others are just decoys, than it would make perfect sense) than their engines will need to produce more power to achieve the same performance as the normal ones. And this can be tracked and detected quite easily.

The exact mechanism is unknown but going from dialogue they detected the radiation from a nuclear warhead to detect it. Now as I understand this is easy to do when you are standing a few feets away with a Geiger counter. But they did it from several kilometers away !

[Hamstray]

Decoys would probably be filled with depleted uranium, which is also used as a tamper in thermonuclear warheads.

[Purple]

Decoys would probably be filled with depleted uranium, which is also used as a tamper in thermonuclear warheads.

At that point you might as well add a detonator and some explosives and make it a proper nuke don't you think?

[Hamstray]

At that point you might as well add a detonator and some explosives and make it a proper nuke don't you think?

Depleted uranium has no critical mass and cannot be detonated on its own. The fission of the tamper material is caused by the fast neutrons from the nuclear fusion reaction which requires rare unstable materials (like tritium). DU is abundant.

[Sea Skimmer]

Laser remote sensing detecting the radiation might work if the warhead was not heavily shielded. Once you blew one apart such sensing can certainly detect uranium in the debris cloud. Uranium on the ground can already be detected from space like this in real life.

[Swindle1984]

I'm curious; for the conventional warheads, would an explosively-formed penetrator be more suitable for use against armored spacecraft? Instead of exploding and showering the ship with shrapnel, or doing a contact explosion (the ways conventional missiles seem to be used in all sci-fi), they instead explode after coming within a set distance of the target and form a high-velocity slug.

In reality, they make decent anti-tank weapons because the high velocity of the slug will let them punch through armor. In space combat, I imagine they'd get even more penetration since you have the speed of the spacecraft launching them, then the acceleration of the missiles, and then the acceleration of the slugs themselves once the explosive charge goes off, making for a speedy little bullet.

Ripple-fire a dozen or three missiles and then they shower the target with EFP's, and you can hole the ship and damage vital systems. The slug would also be much harder to intercept/shoot down than a missile would be, and the stand-off range for the slug could be increased dramatically since gravity and air friction won't be slowing them down.

[Cykeisme]

That makes sense, KE penetrators ought to be more efficient against armor than omni-directional explosion of equal yield, just as in real life.

However, there was a thread where a "shaped-charge" effect for nuclear warheads was discussed, that would use direct the energy from the detonation into a more tightly focused cone. I don't remember the details in the execution, but more knowledgeable members than I thought it physically plausible.


Edit: Ah.. a quick search found mention of such a concept here:
+http://www.projectrho.com/rocket/spacegunconvent.php

Apparently the Orion project's propulsion system has a lot of similarities, and a nuclear shaped charge warhead would be an offensive application of the same concept.


Second edit: However, since we're talking about nBSG that seems to use "normal" nukes that radiate their yield in all three-dimensional directions, you're right, they ought to be rather inefficient against heavily armored space warships.

[Eternal_Freedom]

In fairness to nBSg, we do see the omni-directional nukes being less than brilliantly effective. Galactica takes a direct hit to a hollow metal structure and suffers what is (on reflection) fairly minor damage. Pegasus later takes three hits in close succession and is still capable of fighting, if not jumping away immediately.

The only time we see nukes take out a ship with a single blast is when they are smuggled inside, such as the Cylon Basestar above Kobol and the Cloud Nine.

[Simon_Jester]

I'm curious; for the conventional warheads, would an explosively-formed penetrator be more suitable for use against armored spacecraft? Instead of exploding and showering the ship with shrapnel, or doing a contact explosion (the ways conventional missiles seem to be used in all sci-fi), they instead explode after coming within a set distance of the target and form a high-velocity slug.

It all depends on relative velocity.

If the missile's engines have it doing several kilometers per second on impact, there's not that much point in using chemical explosives at all, since they just can't carry enough energy to add all that much to the kinetic oomph of the missile itself crashing into the target.

If the velocity is extremely high, which doesn't really apply to BSG, then you get an argument for using chemical explosives as fragmentation charges, to turn one solid 100+ km/s projectile (which may be evaded if the enemy's ECM is good enough) into a cloud of 100+ km/s mini-impactors, with a higher probability of hitting the target. Depends on how durable it is, really.

At lower velocities (less than 1 km/s, and maybe a little more) use of explosively formed penetrators makes plenty of sense, as do a variety of tricks found in modern antiship and antitank missiles. On the other hand, closing velocities that low give point defense a pretty wide envelope in which to shoot down the missile, which makes for a lot of problems with any practical design, be it kinetic, chemical-explosive, or nuclear.

One possible problem with EFPs is dispersion- just how far can those things fly in vacuum before coming apart?

[Sea Skimmer]

An EFP fired in a vacuum should stay in one piece forever. Fired into sand on testing ranges they usually stay together as it is. They are much fatter and shorter then conventional shaped charges. They also pierce much less armor, usually only 1-2 times the diameter of the warhead against 10 times or more for a normal precision shaped charge. I can’t see a particularly vast value to using one in a space to space missile as a means of greater standoff. They could make a lot of sense as part of a warhead which pierces the ship and explodes inside. Radical EFP charges would vent a large number of compartments to vacuum and it’s now possible to make reactive metal EFPs that will combust as they do so.

Shaped charge nukes work. Almost everything about them is classified, except that they work by using a lot of radiation reflectors to channel rads into a target material like beryllium which vaporizes and directs the energy into the desired arc. That means all else being equal the warhead is going to be significantly heavier and bulkier then an omni directional nuke. It also appears the result is a lot more like a directional burst, something akin to a Claymore mine, then the kind of tight focusing you normally associate with shaped charge warheads.

[Simon_Jester]

Yeah. With an EFP you're basically writing off the mass of the missile itself and its impact, in favor of the impact of a much smaller mass at (possibly) slightly higher speed. It's not going to pay off well in space- what can the EFP accomplish that the missile itself, hitting at its terminal velocity, cannot? If you're really worried about armor penetration characteristics there are ways to optimize the missile for that role, I'd think... but at some point, a nuclear warhead is probably the cheapest, since the missile body probably costs more than a kiloton-range bomb anyway.

The real life nukes aren't used so promiscuously is the fear of escalation, retaliation, and radiation effects on the battlefield, none of which really apply in a space war between powers that can field warships large enough it takes nukes to put them down reliably.

(I'm idly curious about what kind of terminal velocity you might get from something like an AMRAAM, or longer-range rocket-powered missiles, in outer space...)

[Sea Skimmer]

Yeah. With an EFP you're basically writing off the mass of the missile itself and its impact, in favor of the impact of a much smaller mass at (possibly) slightly higher speed.

Well, not necessarily. If you ejected the warhead, had it fire on the target, while the missile still attempted to make a hit as a purely kinetic round then this limit does not apply. A lot of stuff might work in space that won’t easily work in the atmosphere, in this case because if you ejected a missile warhead in mid air you’d have 1) air resistance on the ejection to deal with, and 2) a giant hole left in the missile airframe creating the same problem unless we have a missile with bomb bay doors (Pluto SLAM apparently did to make that 26 x nuke warhead thing work). But in space, it’d be a lot simpler, a hole means nothing and a ejected warhead can be blunt nosed or any other shape we want and not tumble out of control. This idea could also scale up with multiple ejected warheads so that one missile turns into five or six incoming projectiles or whatever you want.

It's not going to pay off well in space- what can the EFP accomplish that the missile itself, hitting at its terminal velocity, cannot?

Much smaller target for terminal defenses would be one advantage. The other advantage is that, say the missile cannot score a direct hit because it ran out of main engine fuel but got fairly close to the target. It still could then change its orientation, while still traveling on its original course, using only a small bit of fuel in a reaction jet control system it needs anyway, compute a lead, aim and fire the EFP at the target. Then that extra velocity the EFP has effectively turned into more reach for the missile. An EFP can explode out a chunk of metal at some kilometers per second so this is a pretty useful reserve of performance, in certain circumstances. I couldn't really say if it would actually be better then having no warhead and more fuel, this is situational.

EFPs however could still make more sense then a normal shaped charge even for a direct hit. Conventional Shaped charges don’t like voids and layered armor very much, and space warships may be highly bulky but not thickly armored. in that case an EFP would be much better for taking damage deep into the ships hull. Depends on the technology in play.

If you're really worried about armor penetration characteristics there are ways to optimize the missile for that role, I'd think... but at some point, a nuclear warhead is probably the cheapest, since the missile body probably costs more than a kiloton-range bomb anyway.

Nukes are ideal for high firepower certainly, nothing but anti matter could do better, but only if you can use them, missile range and politics could make this impossible to do safely. Ignoring politics effective missile range runs directly into the question of how the missile and starship propulsion works. Since space is much different then the atmosphere it might not be possible to make an effective long range missile at all, because starships have more fuel and more time to accelerate and the only way a missile can shift course is with a main engine burn, not control fins. It may be that effective missile range sucks balls and a firing ship is always within the danger zone for a nuke, unless you have an optimal head on engagement when on paper, range could be unlimited if the enemy didn’t maneuver.

The real life nukes aren't used so promiscuously is the fear of escalation, retaliation, and radiation effects on the battlefield, none of which really apply in a space war between powers that can field warships large enough it takes nukes to put them down reliably.

Radiation effects certainly still apply. Since the nuclear energy is released as radiation, and nothing exists to block the radiation except shear distance that’s going to be a problem at much greater distances then it would be on earth. One nuke might not be such a bad thing, but when people fire hoards of them? Cumulative electromagnetic effects are a problem, many design features to defeat ‘EMP’ related effects do have problems with successive or especially near simultaneous blasts. For example if you have a power quality or line quality filter, a vital component of shielding, that filter makes heat as part of the filtering process, that’s what it does with the bad power frequencies. Overheat it and it melts like anything should, and then that power connection is dead. So you don't have arbitrarily high protection, it is still a question of limits and if they matter or not.

So being in space isn’t a surefire protection unless you only ever use nukes at very long ranges. Of course what long range has to mean is technology dependent. Magic energy shields ought to make the problem go away out of hand; being able to build very high mass warships should also make it become minor simply because you’d have so much weight for redundant protective measures. If that power filter is hooked up to triple redundant liquid helium cooling grids, well, I doubt nukes will overheat it before they start melting the hull anyway, but who knows?

(I'm idly curious about what kind of terminal velocity you might get from something like an AMRAAM, or longer-range rocket-powered missiles, in outer space...)

Well, it’d be a lot different of a rocket and multiple stages would be a vital for starters but probably a couple kilometers a second of delta V. The problem is of course like I was alluding too above, AMRAAM type missiles have the motor burn out within a few seconds and then essentially glide to the target, often taking a ballistic arc part of the way to do so. That doesn’t work in space, you need more thrust to make a course correction, so you need a restartable engine or else a very long burn time to have an effective missile. A space to space missile has to be an equivalent of a cruise missile, something with the engine working all the way up until impact. Now, liquid fuels have more energy then solid fuels anyway and lend themselves to engines that can throttle and restart, but the simple fact that you have to carry a reserve of fuel to nearly the end of the flight limits how fast you can go earlier in the flight. This all also makes intercept geometry even more important then it is for missiles on earth because a target heading away from the missile can keep accelerating until it runs out of fuel, in which case I suspect the enemy was going to die in space anyway, or hits the limit of its exhaust velocity which might be absurdly high. The enemy ship may start out the engagement already going incredibly fast, unlike aircraft which have hard upper speed limits inferior to that of the missiles (usually), and generally piss poor supersonic acceleration anyway. So missile range is highly situational as well as technology dependent.

[Sarevok]

Plus many nuclear based propulsions for space craft puts them much faster than chemical rockets. Any missile smaller than a Saturn V launcher is going to be purely defensive only acting as SAMs or point defense.