So, in my setting, the (space) warships can get pretty big and tough. Some of the big ones can take hundreds of hits and still keep going. However, the problem I've run into is Nukes. Even if your very large(1200m!) and expensive warship can take hundreds of missiles worth of explosives, all it would take is a few nukes to kill it in one go. While the nukes would have to actually make physical contact with the ship, or use a kind of nuclear-shaped charge, it still makes them much more effective(I think). Of course, if you have super-expensive warships that can be killed in a single salvo of nukes, that is unacceptable. What measures can you take to keep the ship intact, beyond shooting down the missile? Specifically, what measures could you take to keep your very expensive ship intact?

Bonus points if the ship is still able to keep fighting afterward and if the system works against antimatter, but nukes are the focus. It's also nice if it is reusable, but not required. Also, they are willing to go very far to protect this ship, even possibly farther than merited by its strategic value since it also has a lot of symbolic value. Basically, they really want that ship intact, at almost any cost. They also have access to making artificial gravity fields strong enough to nudge something out of the way, but not much more.

EDIT: The yield of the nukes are on the order of 2 gigatons or so.

  • $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$
    – L.Dutch
    Commented Jun 5 at 14:04
  • $\begingroup$ How are your nukes being delivered? In space you can see everything all the time, if an enemy ship is built you will see it, if it's within line of sight a million miles away you will see it and easily detect a launch, you have plenty of time to intercept with point defence. How are you going to land the nuke? Knowing how you land it will inform how you can defend against the hit. Note - current warships can also be sunk with a single missile/drone/nuke and yet we still build them! $\endgroup$ Commented Jun 6 at 6:46
  • $\begingroup$ @user63873687 This is assuming that a nuke has already gotten through the defenses(likely through a massive swarm attack of nuclear-tipped missiles) $\endgroup$
    – Bubbles
    Commented Jun 6 at 13:37

11 Answers 11


Nukes aren't as powerful in space as they are on land.

In the air, they create a massive pressure wave that knocks over buildings and shatters bones. If you look at a map of how much damage a nuke will do, it rates the various distances in terms of how much overpressure will hit a specific area.

In space there is no air to create that pressure wave, so you only have the radiation. The radiation is no joke, but it's also not as much of a threat to an object that is already hardened against radiation.

Getting the nuke close enough to cause meaningful damage is an overwhelming challenge. Space is big. With land and sea wars, an area of operation is a couple hundred miles across. In space, you can expect to be keeping unfriendly objects a couple thousand miles away.

Nukes are pretty easy to spot. In space, there's nothing to hide behind. If you don't have propulsion on them, then you can't get them close. If you do have propulsion, then the plume from the exhaust is a big, obvious IR signature.

So you have a combination of factors: difficulty of getting into range, decreased range of effectiveness, and a minimum required shielding just to be in space in the first place.

What you really should be worried about is nuke-pumped lasers.

Addendum: you won't get a nuke that close

There is a lot of commentary about what a nuke could do if it hits a ship. I agree. If you hit a ship with a nuke, you're going to take a huge chunk out of it. The problem is getting close. Think "enemy aircraft getting into the airspace of an American aircraft carrier" close, not "SAM catching up to a fighter" close.

A Minuteman III missile weights five times as much as an F-15. Its barrel is about six feet across. The size of a nuke is limited by the mathematics of critical mass, but you can maybe cut your nuke's size in half because it doesn't have to leave the atmosphere.

With our current telescopes, without atmospheric interference, we can spot a Minuteman coming around 20,000 miles away. That's optical, not radar, and it presumes it's not under thrust. The only way this is going to get within a mile of a capital ship is if you're playing a numbers game, with a lot of cheap, dumb impactors instead of a small number of expensive delivery vehicles.

The one exception is if you let the ships come to the nukes. You can deploy nuclear mines across a broad range of space. They'll still be obvious, but you can scatter them among a bunch of boring empty cylinders as an area denial system. Nuclear space-mines. This would be particularly effective if someone is expecting to use an atmosphere for aero-braking (see Green Mars).

But as missiles? It would be a waste of fissiles.

  • $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$
    – L.Dutch
    Commented Jun 6 at 2:00

A 2 GT nuke going off 1 km away in space is going to crumple the ship like a tin can because of the recoil from the hull vaporizing

"Nukes are weak in space." Sure buddy, but I did see the word "gigaton." Let's do some math.

How much energy per m^2?

The nuke will deliver its energy entirely as radiation, mostly high-energy neutrons and photons. 2 GT TNT equivalent is 8.368e18 J. A sphere with 1km radius has an area of 12.57 km^2. So we have 8.368e18 J / 12.57 km^2 = 6.657e11 J/m^2.

What depth of hull will be vaporized?

Say it's a steel hull. Steel is basically iron for the purposes of vaporizing. and iron takes 340 KJ/mol = 6.093e6 J/kg of heat to vaporize. We also need to heat up the iron to its boiling point of 2862 C. Let's round that to 3000 C, which adds another 1.347e6 J/kg. Along the way we also needed to melt the iron, adding 0.247e6 J/kg, for a total of 7.687e6 J/kg.

A simple division (6.657e11 J/m^2 / (7.687e6 J/kg)) says we have enough energy to vaporize 86601 kg/m^2 of steel (11 meter depth of hull vaporized). That won't actually happen though, because the energy is not distributed evenly. The vast majority of radiation will be absorbed by the outer few inches of steel, while the steel deeper in will be shielded.

We may use the rough figure that each inch of steel reduces radiation intensity by 50%, which to put another way says that each inch of steel absorbs 50% of the energy that reached that depth. If there is less than 6.041e10 J/m^3, the steel no longer vaporizes. We want a formula that says how much J/m^3 there is at each depth. Each additional inch halves intensity, so it should be of the form A 2^(-d/2.54cm). Half the energy is deposited in the first inch, so if we integrate A 2^(-d/2.54cm) over the first inch we should get 3.328e11 J/m^2. This tells us A = 1.8e13 J/m^3. So the formula is 1.8e13 2^(-d/2.54 cm) = 6.041e10, and d = 20.9 cm; that's the depth of hull that will be vaporized.

What is the momentum imparted to the ship from the hull vaporizing?

First, we need to know the kinetic energy of the iron atoms. Since they are vaporized, they are at a minimum of 3143 K. Using the formula $1/2 m v^2 = 3/2 k_B T$, at 3143 K each iron atom has 6.5e-20 J. We add to this the energy E in excess of that needed to vaporize the iron. So $v = \sqrt{(3 k_B T + 2 E)/ m}$.

Using our formula from earlier, A 2^(-d/2.54cm), convert A to J/kg to get 2.29e9 J/kg 2^(-d/2.54cm). The excess energy per iron atom is E = (2.29e9 J/kg 2^(-d/2.54cm) - 7.687e6 J/kg) 9.27e-26 kg = 2.12e-16 J 2^(d/2.54 cm) - 7.13e-19 J. The momentum for a mass m of steel is sqrt((2*6.5e-20 J + 2 E) / 9.27e-26kg) m.

Let's say that we are looking at a 1 m^2 area of hull. How much total momentum is imparted to the ship? Using the formula above we can make a table: for each cm of depth we plot how much momentum is in the gas made from that 1m x 1m x 1cm section of hull.

 cm momentum (kg m/s)
 0  5306959
 1  4627846
 2  4035024
 3  3517440
 4  3065440
 5  2670596
 6  2325541
 7  2023838
 8  1759855
 9  1528662
 10 1325933
 11 1147868
 12 991113
 13 852693
 14 729945
 15 620443
 16 521914
 17 432112
 18 348580
 19 268085
 20 184623
Total: 38284508

So, the total momentum imparted is 38284508 kg m/s for each square meter of hull.

How fast does the ship recoil?

The section of hull under the vaporized section starts moving first, and it starts moving fast. How much armor does the ship have? Say it has 10m depth of steel armor, which is a heck of a lot. That 10m of steel is now instantaneously flying inwards at 480 m/s. There is no realistic possibility of bracing or internal structure preventing the hull from doing this. That's simply too much speed. The armor goes crunch.

The next thing that happens is the ship as a whole gets kicked. How fast it gets kicked depends on how dense the ship is and its size. If you take a square meter cross section of the ship, from one side to the other, what does it mass?

Ships are mostly rooms, and rooms are mostly empty space. Let's say, quite generously, that 10% of the ship's volume is solid steel. You said the ship is 1200m, but that would be the length of the ship. A broadside hit would be more damaging, and let's say the ship has 500m of depth measured through its broadside. That means 50m of steel. A 1m x 1m x 50m plug of steel weighs 4e5 kg. 38284508 kg m/s / (4e5 kg) = 95 m/s. That's how fast the ship as a whole recoils.

The ship is a mangled mess. The square-cube law is not favorable to such a big ship; the bigger a structure is, the more easily it crumples.

If you are a person in the ship, unrestrained, the wall hits you at 95 m/s (200+ mph). You die. Same if you are a piece of loose equipment.

If you are strapped into a crash couch, it's survivable.

How to mitigate the damage

You could protect sensitive equipment and personnel by strapping them down and/or using airbags. You can't really protect the ship as a whole, unless the whole thing is practically a solid block of steel, which seems impractical. But you can design the outer layers to work like a car crumple zone. If the drive and essential items are deep inside and heavily cushioned against a crash, you might still limp away.

Note that this is not a direct hit, this is 1km off the broadside.

Edit: I wrote a Python script to calculate effects of nuclear explosions of different sizes against spaceships.

Permanent link (probably): https://pastebin.com/Yv6JuLyD

Run in browser (expires in 1 week): https://www.pythonmorsels.com/p/29ydv/

To run in browser, click "Run in browser," scroll to bottom, enter prompted information about the explosion.

  • 4
    $\begingroup$ +1 for proving that space is not the end-all of nukes like so many bad SciFys have recently tried to make it out to be. That said, a 200+ mph impact has a pretty low survival rate even in a crash seat. If you're lucky enough to survive that, you will still be badly injured and probably unconsciousness. So, it's still a target neutralizing hit even if you can save some of the crew-member's lives. $\endgroup$
    – Nosajimiki
    Commented Jun 5 at 14:43
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    $\begingroup$ Very nice calculations. The fact that the effect scales like 1/r^2 means that it's very important to keep the nukes at a long distance. The effect for a 10 km distance will be 100 times weaker. $\endgroup$ Commented Jun 5 at 16:06
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    $\begingroup$ +1 for backing this up with math instead of just throwing around guesses. $\endgroup$ Commented Jun 5 at 20:48
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    $\begingroup$ @Nosajimiki yeah, but OP is not only just spouting arrant technobabble (2GT is 20x larger than Tsar Bomba's max yield, and so requires 20x as much "nuclear stuff"), but excluding the ability to shoot down missiles is patently absurd. $\endgroup$
    – RonJohn
    Commented Jun 6 at 1:54
  • 2
    $\begingroup$ It might be interesting to compare to something like a 10MT nuke as well. A 2GT nuke seems... infeasible, but 10MT is very doable, and might actually lead to a "possible to survive if you prepare correctly" situation. $\endgroup$
    – codeMonkey
    Commented Jun 6 at 15:56

EDIT: 2GT nukes are commonplace? Screw big ships

Especially in case where each of those small ships can carry and is actually armed with a nuke or several of compared yield. And especially if manufacturing a 2GT nuke costs hundreds of times less than bulding a 1200-meter long spaceship armed with "conventional" weaponry, like lasers, kinetic stuff and ordinary missiles. When you devise a war of this scale, you are playing a war of attrition already, and having a nuke of that size declared a common weapon does put requirements on what could be effectively fielded against an enemy armed such.

Compare Earth, fleet battles with expected nukes. A sizable fleet travels in a very loose order, so that if a nuke is detonated over it, only the closest ship (or the carrier, if they have one in the fleet, as they are actually very vulnerable) will be destroyed, the neighboring ships would likely survive, and the majority of the fleet would only go on high alert (and probably help the crew of those less fortunate). While creating a single nuke costs about a thousand times less than building a battleship, the delivery vessels have to be included into this cost together with the chance of all of them to be destroyed, this makes the cost of actually delivering a nuclear explosion to a fleet be comparable to one ship's worth of money. Also the aftermath of blowing up a nuke is a part of cost to be paid by either party over years to come, even if it's blown up far from any shores, this part of cost acts as a detriment to ever use them in the first place, and is not present in space. Even so, using nukes en masse vs fleets is considered cost effective.

Now, project this to space: first you've got a 1200-meter extremely expensive warship, armed to the teeth, then you say "there are nukes of 2 GT that can be launched as a salvo". As pointed in the answer with maths, a close hit of a 2GT nuke obliterates pretty much everything (although I still claim the below points would help that ship to survive even that blast), but even if the ship won't get destroyed right away, it would still be badly damaged and have to be taken to repairs. So, one nuke = one ship, maths really can be this simple. They spend one nuke, you spend one big ship - so the best action will be to not field such ships vs such nukes. In case we still count those nukes that fail to reach the target, there are tactics that couldn't be done in oceans that would allow overwhelming the enemy point defense at less cost than delivering a hundred warheads, say plain inflatable dummy shells that produce the same kind of radar footprint as warheads - you can't go easy on Earth due to atmosphere (although ICBMs do have such decoys while in space). So while the enemy would have to spend a dozen actual warheads to ensure one close blast vs point defense, the costs are still in favor of nukes here.


PS: building layered nukes, while possible, also increases their size, remember the Tsar Bomba was "mere" 100MT yield as a project, and was some 2 meters across, meaning that a 2GT nuke is no longer a target for just point defence systems, normal weapons could be employed to try and blow it up before it'll blow up the ship. So a part of the answer will be "blow them with your main caliber", for example, a single nuke blown up in a field of decoys would eliminate all of them, and might even set off an enemy warhead, which might then turn the costs war in your favor.

Layered anti-dust armor

In fact, nukes in SPACE are overestimated. The largest damage dealer with the nuke is the shockwave, and if there's nothing to shock with, this kind of damage is mostly mitigated. So, you have your armor layered like modern day's Whipple shield, a couple meters deep, with some defense systems showing out of the topmost layer to actually do their job (remember ye olde Doom Star), this way if a nuke (of earthly size, averaging 1Mt) would go off at the surface, the layers would sequentially reflect some of the direct radiation away from the ship, as well as cause the majority of EMP energy to be caught into heating itself, also preventing the bulk of armor to get insta-vaporized. It will still do damage, but with several meters worth of ablation it might not be as devastating.

A nuke worth 2GT blowing up at 1km distance vs such a shield would still cause inward momentum, vaporization of a part of hull, shockwave hit from the ship's own ablated armor turned plasma, etc, but this armor design still comes up on top versus solid steel. First, its layered structure also acts as a shockwave damper, absorbing shockwave energy by breaking apart at depths not vaporized. Second, solid steel does not reflect energy as good, especially penetrating radiation, while every exposed surface of layered shielding would also cause a bit of reflection. Third, when the nuke would turn outer layers into plasma, it will initially have less density, as there is vacuum between shield layers; thus the process of the blast energy penetrating the defense layers would cause more energy to be absorbed by plasma than in case of solid steel wall. The major result would be more plasma heated by incoming radiation, thus less steel vaporized, this will also result in less momentum delivered to the ship via ablation recoil.

Kinetic shrapnel point defence systems

Lasers in SPACE are also overrated by a great margin. Lasers have the most damage dealt at the source, regardless of construction and/or distance to target (mitigated by cooling systems, but still), while kinetic weapons cause direct hard damage to whatever they hit, also their construction can be made to lessen the initial damage to the ship caused by acceleration of the kinetic projectile (railguns etc). Even ancient era machine guns, if fired at an incoming nuke (it's detected at enough range to aim the guns), would cause enough shrapnel density to guarantee at least one hit, and with delta-V of those ships a single bullet hit will be enough to disable an incoming nuke outright. A gas-powered shrapnel cloud weapon with initial particle speed of ~200 m/s would cause more than one hit against a standard-sized nuke (2 meters diameter), and would cover the area of more than 100m in diameter after half a second from launch, more if projected forth on top of scattering. Use several of these in general direction of an expected incoming nuke and watch it get shredded.

There is a tale about Soviet response to US's idea of laser-armed satellites, where the Soviet chairman replied "We would just launch a bucket of nuts and bolts to a retrograde orbit, your laser things would break apart". The general principle would certainly hold itself in your space conditions. The funniest thing about such a defence is that the shrapnel cloud could have zero relative velocity to the launched ship, but if it'll be dense enough, it will destroy any incoming device that's more complicated than a rock. And if you have some small control of gravity, it's possible to devise a protection system that will launch such a cloud in case of incoming nukes, then collect it back once they all got eradicated. (As a side note, such a cloud would also destroy any decoys as well, so devise a projector ship that would be able to whizzle around your fleet and poof shrapnel around itself to catch stuff flying your way. There was even a real life project of a space ship, Project Daedalus, that had such a protector ship flying before the main vessel in order to protect against space dust at high speeds.)

  • 2
    $\begingroup$ The "bucket of bolts" chaff-shield idea is a good one - doesn't technically violate the "beyond shooting down the missile" requirement, since it's really just kinda equivalent to a very distant whipple-shield layer. $\endgroup$ Commented Jun 4 at 23:47
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    $\begingroup$ I've read estimates that suggest 1 million USD - with inflation and removal of over-optimism the cost is still minor in comparison. Latest US carrier $13.4 billion, destroyer $3.4 billion, frigate $900 million. Clearly you recognize nukes are much cheaper than ships so you might want to revise your "is cost comparable" statement because it's confusing your point. $\endgroup$ Commented Jun 6 at 12:55
  • $\begingroup$ @GaryWalker hmm, fair point, although the carrier is not that easy to be hit with a nuke, there's a lot of SAM and other guards to shoot the nuke down if it would be detected, and delivering one nuke vs that carrier would hake some dozens of warheads, leveraging the prices a bit. Or a submarine, or a super unmanned torp, or whatever fancy they claim to have (either side). Also this $1M depends on what's the yield of a nuke, say this estimate says 300kt warheads are worth some $5M. And no guarantee of a hit here. $\endgroup$
    – Vesper
    Commented Jun 6 at 14:10
  • $\begingroup$ Forgot to mention that the 1 million est. (certainly low) was for mass produced nukes. i.e, nukes are commonplace. But almost certainly on the low side. I just thought some scale of actual numbers was helpful. $\endgroup$ Commented Jun 7 at 12:06

Stop the shockwave propagation

Explosions 101

Explosions are dangerous mostly because they convert a little volume (solid TNT, plutonium, whatnot) into a lot of volume. For simple explosions this is done mostly by very quickly burning solid material and producing hot gas that takes up more volume, with nukes you simply produce so much heat that everything close to it either turns to gas or existing gas (air) heats up and thus takes up more volume.

The "more volume" pushes against everything around it (air, water, ground, hull metal). All of THAT (if it does not resist) then pushes further against everything next to it on the other side, propagating a shockwave.

Explosions in space

As other answers and comments have pointed out already, Nukes (all explosions, really) are a lot less effective in space. If the explosion does not occur right on the hull, the hot gasses push into vacuum - which is basically "nothing", and will not further push against anything. So instead of pushing existing material further, you're just throwing hot gas and shrapnel around. Nukes further have the problem that all they can heat up is the material they brought, not any air around them - so the massive amount of energy they produce has a lot less material to actually affect. Other forms of energy transfer from the nukes may still do damage, but the force of the explosion that would flatten a city in an atmosphere falls off very quickly.

Explosions against the hull, in the hull, or in the ship

If something explodes right on the hull, then there will be damage - still a lot less than in an atmosphere because most of the explosion will take the path of least resistance (all the vacuum on the other side of the explosion), but some of the force will be transferred. A bit better. And a nuke will be happy to know that hulls consist of material they can heat up, possibly vaporize, and thus actually do some work!

If you can penetrate the hull before exploding, you get a lot more bang for your buck. An explosion in a hole will have material on all sides except one, so while still worse than in an atmosphere, most of the force will be transferred into something instead of getting wasted. And if you get the explosion through the hull into the ship itself, there might be an atmosphere there to use!


Now, as we have seen, explosions are most dangerous if they are as close to the hull as possible, ideally IN the hull. How do we stop that?

  • point defense: shoot it before it reaches you. Not much to explain there, I think.
  • whipple shield: spaced layers of thin material, with vacuum in between. Even if an explosion hits the outermost layer, it will just rip a hole into that - and the layers below get a bit of shrapnel at most. There's vacuum in between, the shockwave does not get propagated.
  • hard hull: you don't want the explosion inside the material, so make the hull as hard as you can. This might make it brittle - but against explosions, "pieces breaking off when hit" might be less of a problem than "soft metal deforms by impact, allowing explosions in the hull material". Note the trade-off, this armor might be worse against other weapons which can now break chips off instead of slightly deforming softer armor plates.
  • vacuum inside the ship: as seen in the show "the expanse", get into space suits and pump the air out of your ship if you expect combat. That way, a weapon that penetrates the hull entirely will still explode in vacuum. It will throw shrapnel against your people and delicate machinery, so it's not GREAT, but it's less bad than an explosion in atmosphere that can cause damage via shockwave.

Special mention: Honeycombed armor

Once a shockwave actually is in the hull, one way to lessen its damage is to have honeycombed armor. This means that after the initial thick plate, you have layers of vacuum-filled chambers with relatively thin walls - a shockwave will deform the walls, but the vacuum chambers will give it a lot of empty space to waste its energy in. These armor plates will get damaged with every combat encounter, so make sure they're easy to replace afterwards - and longer combat will mean that some armor sections will already be smushed flat by earlier explosions, and thus less effective against new ones. So rotate the ship, show the enemy your intact armor!

  • 2
    $\begingroup$ Just a note on hard hulls: spallation is a thing. and not a good one, if you're on the business side of it. spallation is when "knocking hard" on the outside of a hull causes bits of the hull on the inside to break up and fly around on the inside. propagation hill be roughly hemispheric from the point of impact, so actually letting it hit through your hull and hopefully out the other side would cause very much less damage. $\endgroup$
    – Burki
    Commented Jun 4 at 12:17
  • 1
    $\begingroup$ Whipple shields don't work on nukes. Nukes are already able to destroy the whole surface of the ship if it detonates shy of the target; so, forcing an early detonation to spread the attack out on your inner hull is redundant... not to mention that most of the energy from a nuke will be in the form a gamma rays so, whipple shields are going to be too thin to be able to absorb a significant % of the radiation anyway $\endgroup$
    – Nosajimiki
    Commented Jun 5 at 14:27


As others have pointed out, explosions in space aren't super effective. And Syndic's answer has some good countermeasures with whipple shields and the like.

If you want to still be functional after taking hits you need redundancy.

B17 Flying Fortresses in WW2 had 4 engines but could still fly on two engines.

It doesn't matter if some nukes have knocked out some engines if you have more that you can fly with. Redundancy is critical and anything you can't have redundancy for would be kept in the most protected part of the ship.

If the enemy knock out an engine you can still fly with the others.

The design of the ship can have multiple corridors internally so parts of the ship can be sealed off if they get hit while still retaining access (albeit probably to now unpressurised bits) power and control of systems.

Redundancy works for whatever the enemy throws at you. It doesn't matter if it's a nuclear missile or an meteorite, if you have another system which doesn't get hit you can still keep on going.


Space reduces the kill radius of a nuke, but not be enough to matter

While people talk about how much weaker a nuke is in space, it is not by enough to matter. If we assume this ship is armored similar to a WWII Battleship then the entire conical of the ship facing the blast would be about 1.7 billion kg of steel. (You don't need to know the exact geometry of the ship because there is an approximately 1:1 relationship between this volume of steel and the cross-sectional silhouette's surface area) which at a specific heat of 420/J/K and boiling point of 3000K means that the entire outer hull of the ship would explosively vaporize from about 2.2e15J of energy (it would probably take much less than this to simply shatter the hull from thermal shock, but this is easier to calculate).

A 2GT nuke releases about 8.4e18J of energy which means that if the nuke detonates within 21km of the ship, the entire outer hull of a heavily armored warship will be instantly vaporized, and expand with enough explosive force that it will collapse in dozens if not hundreds of meters of the ship's interior and sending a shockwave, radioactive burst, and EMP though your ship that should kill everyone on board and wreck every system on the ship.

Nukes are not weak, your shields are just that strong.

Because this setting also assumes that kinetic missiles are a viable weapon system, it means that missiles MUST be target accurate enough to actually hit a ship; so, getting within 21km to detonate should be a trivial task for a nuke. Since the META in your universe is big ships, it means that you can not make a ship small enough to simply avoid missiles; so, they can't just be accurate enough to hit a 1.2km dreadnaught, but they also have to be able to hit your smaller drones and fighters meaning that your missiles, and therefore your nukes, have to actually be able to be target accurate within a couple of meters to be internally consistent. So, there is really no scenario where you can assume these nukes have to be detonated outside of thier actual kill radius. Frankly, if the only thing protecting your ship were physical armor, a 2KT nuke should be enough to cripple a ship, let alone a 2GT one...

However, the problem you are having is not actually how strong the nukes are, it is that there is no balance between nukes and the other weapons you wish to see in your setting. What you are forgetting is that future tech space ships tend to be a lot faster than the stuff we have today. If you get hit by a 5 ton kinetic missile moving at 0.2c, you're also getting hit by a 2GT force even without a nuclear warhead. Oh and that laser? It's actually an antimatter particle beam that also hits in the Gigaton range of damage. So the issue is no longer that nukes do insane amounts of damage, but that that EVERYTHING does insane amounts of damage. And that makes your problem a lot easier to solve because it eliminates the internal consistency problem.

The way that most sci-fi settings (Star Trek, Star Wars, etc.) address this conundrum is by introducing "shields". In Star Trek TNG, they talk about how a photon torpedo detonated from over 10km away could destroy the Enterprise D and how a class-X phaser is powerful enough to pierce a planet's crust, yet the Enterprise D can tank several direct hits from these same weapons when its shields are up because they assume the ability to directly mitigate energy with an opposite and equal energy.

If you have missiles that can pack enough energy density to hit relativistic speeds, then imagine how much energy density your 1.2km long ship that is also capable of relativistic speeds must have at its disposal. The thing that makes your big ship so tanky is not its physical size, but how much power it can pack in reserves to maintain its shields. If you imagine your ship has some manner of energy shield that can deflect the energy of attacks to a total of 1e20 Joules of potential energy before running out of juice, then it can logically shrug off 100 of those 2GT nukes, or any combination of equally powerful attacks.

If you want your ship to take actual battle damage, just suppose that the shields can counter something like 99.9999999% of the energy that hits the ship letting through just the tiniest fraction of actual energy which the ship's armor is then responsible for dealing with such that a 2GT hit still puts a nice hole in your side like you would expect from something like a UGM-84 Harpoon Missile, but nothing at all like what a nuke, antimatter beam, or RKKV would do to an unshielded ship.

  • $\begingroup$ Nukes are that weak. A 2 GT nuke going off on Earth might demolish everything within 200 km, but in space, a 2 GT nuke 200 km from your ship will deliver less energy total than the Sun does in two seconds. $\endgroup$
    – Mark
    Commented Jun 5 at 0:00
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    $\begingroup$ @Mark A 2 GT nuke 200 km away will deposit about 1.6 * 10^7 J/m^2. In two seconds the Sun delivers about 2 * 10^3 J/m^2 to objects near Earth. So you're only off by 4 orders of magnitude. $\endgroup$
    – causative
    Commented Jun 5 at 9:22
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    $\begingroup$ @mark If it goes off 200km from your ship, it might be survivable, but the setting already established that kinetic missiles are target accurate enough that bigger is better than smaller which is only internally consistent if missiles are accurate within a couple of meters, not hundreds of km. At that range, you're talking a significant fraction of the nuke's power being absorbed by your ship, and once that portion of the energy hits the dense matter of your ship, it will explosively expand the same as a smaller, but still gigantic nuke. $\endgroup$
    – Nosajimiki
    Commented Jun 5 at 13:16

You have a few options:

  1. WMDs are outlawed. People - like here on Earth - have an implicit mutual agreement: I won’t use nukes, and you won’t either. There is virtually no way to survive a nuclear blast, because the shrapnel from the bomb, moving at significant fractions of $c$, will tear through your hull as though it doesn’t exist, and the radiation will cook everybody in the ship and in the surrounding few hundred miles (remember, radiation travels better in a vacuum). So, have everyone have nukes! Every warship on “red alert” arms nuclear warheads and has them ready to launch at a moment’s notice. If someone else uses nukes, which you can detect by the warhead’s radiation, you just launch yours and everybody loses.
  2. Unobtainium-powered pion fields. Fission weapons (which also power fusion weapons, and thus fusion weapons by extension) operate on the principle of making fission energetically favorable, causing it to happen a lot in heavy nuclei and releasing a lot of energy. If you don’t want this to happen, project a “pion field” around your ship: a field that enhances the density of pions, the species of meson that carry the residual strong force that holds nuclei together. With the strong force becoming the “stronger force”, more energy is required to cause fission, and nuclear warheads just fizzle. (Because pion density-enhancing fields are not known to exist, this would be science fiction, but the physics is sort of there.)
  3. Non-Newtonian armor. Non-Newtonian fluids are liquids whose viscosity (resistance to flow) is correlated with the applied pressure. A common example is “Oobleck”, which you can swirl your hands through like water but becomes rock-solid when you hit it with a hammer. Maybe your battleships have armor filled with non-Newtonian fluids: against bullets, it works like a solid; against regular bombs, it can absorb the blast and knock the ship around, but stay intact; and against a nuclear blast, the armor just starts ablating as it becomes a super-solid, probably disappearing in the process but allowing the ship to survive the blast and get considerably knocked around - beware $g$-forces, but the ship is intact, at least. (Also a science-fiction answer: no such non-Newtonian fluids actually exist, but it sounds plausible.)
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    $\begingroup$ I’m always surprised at the non-newtonian armor idea. Take a car and make the crumple zone hard, all you did was increase the shock to the occupants and increase their chance of death. That’s why we invented crumple zones, to reduce that shock. Why would hardened armor help save you against the explosion? At best it would help stop shrapnel, but then you still want a composite armor (hard outer layer soft inner layer to catch remains) or a whipple shield. Unless the non-newtonian effect somehow absorbs the shockwave due to the hardening? But I never see that stated as an effect. $\endgroup$
    – Demigan
    Commented Jun 4 at 14:04

Nuclear missiles aren't used for their explosive effect in space, but for the nuclear electro-magnetic pulse (EMP) that they produce.

Because of the lack of atmosphere, as mentioned in the answer by @RobertRapplean, there is minimal shock wave produced by a nuclear explosion in space. Without a direct hit and transmission of the shock through the ship, the explosive force is not significant, so they are used for their other effect - EMP production.

EMP are propagated in space, in the form of various optical (infrared, ultra violet, visible) and ionizing radiations (gamma-ray, x-ray etc.) which are damaging to both the staff of the ships and the detection equipment on-board the ships. Near miss explosions are just as, if not more, damaging than direct hits because of the greater spread affecting more of the sensors on-board and the wider dispersal of the radiation over the staff.

This is a fairly common trope in SF, and the usual solution for damage to the ship is to have self-repairing equipment and/or equipment that can be rotated out from inside the ship.

The effects on staff could be mitigated by having the ship shielded by heavy-metals (for ionizing radiation) and/or rely on sensors only during battle (i.e. no/covered portholes during battle), so that there is mitigation of damage to the eyes by the bright visible flash produced by explosion.

For some measure of how effective an EMP is, I refer you to the Starfish Prime nuclear test carried out by the USA over the Pacific. This was a 1.5 megaton high-altitude (250 mi/400 km) explosion that took place about 1450 km (~900 mi) away from, but in direct line of sight with, Hawaii. Despite the distance and being a relatively small explosion it still caused damage to the power infrastructure on the islands, knocking out street lights and some tele-communications equipment. In addition, it damaged some satellites in orbit and some technical documents were produced around it

Flash-blindness in people from a nuclear explosion is definitely a problem too, however, I haven't been able to find something that simply explains this and if this is a problem only in an atmosphere or not. The Starfish Prime test linked above had a fireball visible from some 1400-1500 km away, but is still considered to be an in-atmosphere test, despite being 400 km or so above the planet.

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    $\begingroup$ Most of the effects of nuclear EMP come from interactions between the explosion and the Earth's upper atmosphere. With no atmosphere, nukes in deep space don't generate a noteworthy EMP. $\endgroup$
    – Mark
    Commented Jun 4 at 1:07
  • $\begingroup$ @Mark I linked the same link as you (my first link...), there's still an EMP with the high altitude tests, where you have densities in the 1 atom/km^3, they weren't quite in the exosphere, but nearly. There would certainly be ionizing radiation from the blast interacting with the ship's atmosphere and structures. I just don't know much about the longer wavelengths. IR certainly from atmospheric interaction, but UV and visible?? The reports of the initial bright flash indicate very short duration, which would imply from the explosion itself. $\endgroup$
    – bob1
    Commented Jun 4 at 2:48
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    $\begingroup$ @Mark you have it backwards. The EMP effects of a nuke actually have much longer ranges in space because there is no atmosphere to absorb it the high energy gamma rays before they reach your equipment. In the lower atmosphere, high energy waves are absorbed by the air, some energy turns to heat, and the rest is retransmitted at a lower frequency in a way that cascades until the EM radiation is too weak to ionize what it hits. $\endgroup$
    – Nosajimiki
    Commented Jun 5 at 15:59
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    $\begingroup$ The reason upper atmosphere EMPs are more effective is because it can spread out more, unimpeded by the lower atmosphere or the horizon line. In space, there is no air or horizon line at all; so, the high energy gamma rays just expand until they hit your equipment directly where it ionizes your equipment itself, maximizing it's effective range to several times farther than even an upper atmosphere EMP against a ground based target. $\endgroup$
    – Nosajimiki
    Commented Jun 5 at 15:59
  • $\begingroup$ @Nosajimiki, the spread is also subject to the inverse-square rule: the EMP range of a nuke in deep space may be higher, but the effect will be weaker. $\endgroup$
    – Mark
    Commented Jun 5 at 22:41

While people are totally correct that there isn't a shockwave in space, they are forgetting one thing though......the photons that heats the air into the shockwave in a atmosphere is still going to mess up the ship quite alot. take, for example, the 2GT nuke you mentioned, sure it's got no shcokwave but that's still some 1 gigajoules (values halved as the nuke is spreading it's energy in a sphere and only half of it is touching the target) of radioactive death for your vessel to handle. no idea on the technology available in your verse but that's still quite enough to cook some crew, eh?

So, what's the solution, you asked? Well here's some that I came up with or saw around the corner...

1: Explosive Reactive Armour

Although it definitely seems weird to have ERA blocks on your vessel, it might just be workable. You see, you mentioned that the nuke is a contact fused nuke, and if it is exploding on contact, then it might make sense to use the ERA's metal plate to fool the fuse into believing that it is hitting the actual target, and therefore explode prematurely. If it exploded earlier than it should, then a lot more energy is not actually going to touch the vessel, remember square-cube law? He's your friend here

2: Particle Field Armour


3: LOTS of heat-resistant materials

This is probably the worst method, but if you need some backup or simply have some really good materials in your verse then go ahead. according to atomic rockets one gram of boron has a vaporisation energy of 45.3 KJ, which means that to handle the 2GT nuke's surface detonation we would need......9.24E7tons of boron to stop it. Egads Over all, it's probably the best for your vessel to really strengthen it's point defence grids, but if they fail at stopping the nuke then with the above methods it might still be survivable

  • $\begingroup$ Minor nit: a 1 GT doesn't contain 1 GigaJoule but more like 1 ExaJoule, which is rather a lot larger. $\endgroup$ Commented Jun 4 at 23:56
  • $\begingroup$ ...Though I think you got that right in the calculation, just not in the first paragraph. $\endgroup$ Commented Jun 5 at 0:15
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    $\begingroup$ ah, you're right on that, somebody isn't checking units carefully) $\endgroup$ Commented Jun 5 at 3:51

Other answers address the case of a single solid ship being struck by a nuke.

What about changing the design of the ship? @Nosajimiki mentions that other weapons may be equally damaging. Ultimately, for a solid ship/borg cube/deathstar, it's a matter of joules of kinetic or thermal energy to destroy them.

What if instead the ship is designed like a mesh? Rather than a solid hull and squishy internals, instead a self-organized distributed network of interconnected minor ships, each the size of a shipping container, and each with its own hull, and tethers that automatically connect it to nearby ships, from up to several hundred yards distant, to being directly docked together.

The ships at the point of impact are the ablative shield. Practically, there'd be a cloud of shrapnel/debris spreading out from the ablative ships to the next layer and so on. So you'd lose a chunk of the ships.

If they're all loosely tethered, spread apart from each other by several ship-lengths, the ships will be better able to handle large kinetic impacts. Some tethers could carry coolant, and their distributed arrangement would mean they could dissipate thermal energy. When tightly-tethered, each ship physically docked to another, then the ship would be better able to maneuver.

After the impact, the remaining ships would then self-organize to form a new ship. There would need to be specialist ships - engines, fuel storage, etc. These would go to the relevant points. The remaining ships are for living quarters, structural, etc.

This also has the advantage that if the ship would be tactically better off as two ships, to perform a pincer movement, then it can do that. If it's better to be just act as a cloud of separate drones surrounding the target, then drawing in around it to become a solid shell, it can do that.

This, I think, answers the requirements of the question: such an aggregation of tethered ships can take a nuclear hit, and still have some portion of it continue fighting.


Firstly lets consider how nukes would actually be used in space whilst also clearing up some misconceptions.


This isn't as big of a deal as on land, in space once you've shielded yourself from the initial flash, you'll be fine.

After all your in a gigantic hermetically sealed box designed to withstand constant radiation exposure for days or weeks at a time.


This is where it gets tricky, the primary reason a nuke isn't as effective in space is because there's no medium for a blast wave to travel through. If the nuke was in intimate contact with the ship before detonating, the blast wave could travel through the ships hull. I still don't think this would be as devastating as on earth because your still lacking some sort of medium like air or water to carry the blast wave.

You might be able to use some sort of thick coating that absorbs the blast as best as possible to minimize damage. Kind of like starlite.

Nuclear Shrapnel

I don't see many other answers mentioning this but nuclear shrapnel is a real thing. Way back when, some scientists came up with the concept of a "Nuclear shaped charge". It's the same as a regular shaped charge, but enormous and with a little nuke inside.

Imagine if you took that concept, put the cones around the nuke in a sphere and stuck a proximity fuse on it. You've essentially create a nuclear depth charge that can punch car sized holes through an aircraft carrier.

Nuclear Shaped Charges

As mentioned above, nuclear shaped charges have already been dreamt up. We've never technically made one, but in a war in space they could be a ludicrously powerful weapon. If the charge is on a highly maneuverable missile that can avoid getting itself shot down, getting even miles from the target would be sufficient to punch a hole in it.

I see a couple comments mention a form of armor piercing nuclear weapons, as in a projectile that penetrates a hull before detonating. This is needlessly complicated, has a higher risk of being shot down and probably wouldn't work if your target has half decent armor or whipple shields.

A nuclear shaped charge would make alot more sense in my opinion.


So, how do you defend yourself from these weapons? Radiation is straight forward, just add more radiation shielding.

Armor is a no go against a nuclear shaped charge of any kind, there isn't an armor that we know of that could survive a 240,000 km/h impact of molten metal. Even if it doesn't breach the ship, depending on the size of the charge, it could still crush the ship like a pellet gun shooting the side of a tin can.

The only real defense is an effective offense when it comes to these weapons, you have to either shoot them down (A laser might work for this) or using electronic warfare to interrupt its normal operation. An EMP might also work if the weapon isn't EM shielded, it could disrupt the weapons firing circuits to cause a premature or incomplete detonation.


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