So I've read up (NASA has good stuff) that nuclear weapons detonated in space are primarily a radiation hazard. Thermal and concussive effects are negligible, other than I suppose hot fragmentation from the missile/warhead itself if close enough.

Now the radiation can be significant, according to NASA, even a 20 kT detonation can expose humans to lethal radiation doses from a detonation 30 km away, maybe more.

But for this question, assume that "shielding" basically negates the radiation hazard.

The other mechanism for a nuclear warhead kill is if you can detonate the nuclear warhead inside the ship. This will most certainly be lethal, if not outright vaporizing a portion of the ship.

In reality, nuclear weapons are not designed to penetrate, most are air detonations to maximize the concussive destructiveness.

So here's my question: is it realistic to expect a nuclear warhead to survive the impact of penetrating a ships armor so that it can detonate inside the ship as intended? Or would the action of penetrating the armor be so violent as to basically destroy the nuclear bomb components before they can detonate?

Let's assume the target ship is heavily armored, likely multi layer, with some sort of outer energized or explosive reactive armor, followed by layers of special composites and ceramics, and finally a thick metal alloy hull.

EDIT: @Nosajimiki - great response, thanks. In regards to the effects of 1 MT space detonation, I did some reasearch.

A 1 MT blast yields 4180 TJ of energy. For air blasts, I've read that approximately 50% of this energy goes into the blast, 35% to thermal, 5% to immediate radiation effects, and 10% to "lingering" radiation effects.

Here's my thought: I took 40% of the 4180 TJ (thermal + immediate radiation). Assuming a spherical blast, the target will only receive a portion of that 40%. I assumed 25%. That means the target is subjected to approximately 400 TJ. In my WB exercise, ships are "large". I assumed an average warship, 1200 m x 80 x 125 m with 30 cm of armor. I assumed, for this purpose, regular iron. It would take nearly 1100 TJ to melt the hull. If you choose better (real) material, you can get this up to 3300 TJ to melt the hull. With a little "future handwavium", this can be increased to nearly 6000 TJ "reasonably". Adding "futuristic" heat tiling further improves the odds of the target.

Any further input would be invaluable to me. Thanks.

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    $\begingroup$ Has anyone mentioned bomb-pumped lasers to you? If not, do I have an answer for you... $\endgroup$
    – DWKraus
    Commented Mar 1, 2021 at 23:29
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    $\begingroup$ You don't want penetration. You just need for the point of explosion to be close enough to include a bit of the target's matter (even its armor) in the primary fireball. This will set off a ridiculously energetic shockwave through the target, shredding it. The total blast will still be very much less than an air detonation, but then your target is usually smaller than a city. $\endgroup$
    – PcMan
    Commented Mar 2, 2021 at 1:00
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    $\begingroup$ nuke behave weird in space youtube.com/watch?v=qEfPBt9dU60 $\endgroup$
    – John
    Commented Mar 2, 2021 at 5:27
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    $\begingroup$ The primary risk of a nuclear detonation nearby a spaceship is the huge blast of EM radiation it produces... It would fry any electronic system within hundreds of kilometres unless they had some serious shielding. $\endgroup$ Commented Mar 2, 2021 at 11:45
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    $\begingroup$ Let's assume you were the politician who persuaded your government to pay for a ship heavily armored, likely multi layer, with some sort of outer energized or explosive reactive armor, followed by layers of special composites and ceramics, and finally a thick metal-alloy hull. How did you get that budget passed? $\endgroup$ Commented Mar 2, 2021 at 22:52

9 Answers 9


The Nuke does not need to penetrate the ship as long as it detonates close enough. By proposing radiation armor that can keep the gamma rays from passing through your ship, you necessitate that your armor absorbs that energy which will in turn become heat. A nuke that detonates just shy of impact will deliver such a concentrated burst of radiation to the hull of the ship that it will instantly heat up to many times hotter than the boiling point of any known matter. This much heat will cause the surface of your ship to experience an explosive expansion. Even if only a fraction of the nuke's energy actually makes contact with the ship, nukes are VERY powerful weapons. Even taking just 1% of a 20kt nuke is about the same as detonating 200,000 kg of high explosives strapped to the front of your ship.

The second consideration with nukes is that making one just a little bit bigger can give you a lot more bang. So, while 20kt nukes are an option in space, the main reason to make them that small is to make sure the guy firing it can survive the radiation from the blast. Radiation is lethal from much farther away in space without an atmosphere to absorb it, but if your ships have theoretically perfect gamma ray armor like you've proposed then staying that small is not very logical. The smallest 20kt nuke ever developed by the US was about ~90kg, but by just going up to a ~110kg warhead you can have a warhead 6 times as powerful. I suspect the goal of space nukes would actually become making nukes that can hit close to the Taylor limit (6kt/kg) to optimise kill radius to warhead weight. This would mean 200-250kg warheads with ~1 megaton explosions. https://en.wikipedia.org/wiki/Nuclear_weapon_yield

As for your armor design, most of it will do little to nothing to stop a radiation weapon. Reactive armor has no mass to counteract; so, it will be next to useless. Next you are looking at composites. Most armor composites are some variation of resin and fiberglass. While this is very effective at stopping an impact, it is not very termal resistant compared to metal alloys or ceramics. When heated quickly, it will melt/shatter relatively easily. This just leaves your ceramics and metal alloys to actually sponge up the thermal energy of the blast. Without actually knowing what your hand wavy super materials are made out of that will prevent the gamma ray burst from just sweeping through the ship killing everyone... let's say that they probably have a vaporization point of somewhere between that of graphite and tungsten. You also don't specify what you mean by "thick" since what is thick for a spaceship is generally very thin for a naval ship. So let's say the armor on you spaceship has a similar thickness to a lightly armored Naval Warship: 25mm. At the given values you will need 1.2 million kilojoules of energy per square meter to completely vaporize the hull. This means that you could detonate a 1 megaton nuke at a range of ~520 meters and still cause the hull of a nearby ship to thermally explode... but even from much farther away, you could still heat the outer hull up enough to melt it: plus cause some very serious problems for any people or electronics inside of the ship.

Also, keep in mind that a ship IS a medium capable of transferring a shockwave; so, if you heat the outer hull to explosive temperatures, that explosion will propagate through the whole ship causing shearing/compression/shrapnel etc which will likely rip the whole ship to shreds, and killing everyone on board.

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    $\begingroup$ Also note that if your ship does not have a LOT of shielding you are also talking about lethal radiation doses to the crew. Then you have the most destructive part, Shrapnel, shrapnel propelled by a nuclear detonation will make tear through meteorite shielding like tissue paper. $\endgroup$
    – John
    Commented Mar 2, 2021 at 5:39
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    $\begingroup$ "Close enough" is doing a lot of work there ;-) $\endgroup$ Commented Mar 2, 2021 at 7:48
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    $\begingroup$ @StarfishPrime Yes indeed. If you can get a ~200kg warhead to within that distance, do you even need it to be nuclear? At that point, and at the kind of closing speeds you'd expect for this scenario, I'd have thought a 200kg sack of gravel with a small charge to disperse it would do the job for much cheaper. $\endgroup$
    – G_B
    Commented Mar 2, 2021 at 23:57
  • $\begingroup$ Even if your armor can somehow survive the explosion, wouldn’t it cause quite some rapid acceleration of the spaceship? (depending on its mass) Which would probably be quite unhealthy for humans inside. $\endgroup$
    – Michael
    Commented Mar 3, 2021 at 7:23
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    $\begingroup$ @Michael It probably would unless the setting already has inertial dampeners. $\endgroup$
    – Nosajimiki
    Commented Mar 3, 2021 at 15:14

Nuclear Bomb Pumped Lasers

Are a common SC FI weapon and were experimented with by the US in the 1970s (Project Excalibur) - preliminary tests were conducted but no actual working weapon produced. The basic idea is that a nuclear bomb is detonated as a 'stand off' weapon a pre-calculated distance from the target. All the energy of the blast of course expands outwards symmetrically from the point of origin but along the way a small % is 'captured' by focusing 'arrays' of varying design which act as lenses for the captured energy.

These arrays then emit the captured plasma/energy as either focused x-ray laser pulses or in some designs gamma ray laser pulses. There are (usually multiple) focusing arrays attached to the bomb and just prior to detonation the warhead maneuvers to try and have as many as possible pointed at the target (or perhaps it divides them up across multiple targets in its cone of fire).

The result are utra short, ultra powerful bursts of laser energy that will severely damage whatever they hit no matter how well armored. The weapons are of course 'one shots' since the explosion destroys the device.

Here is a link to 'Atomic Rockets' one of the 'go to' sites for all things both hard SF and 'spacey'. It has a comprehensive list of possible space weapons (bomb pumped lasers are about a quarter of the way in). Also included is the other nuclear option mentioned above the Casaba Howitzer which is very impressive. Atomic Rockets

  • $\begingroup$ You should put in a reference to Excalibur, although the science on actual working bomb-pumped lasers is officially that it hasn't been proved to work. en.wikipedia.org/wiki/Project_Excalibur $\endgroup$
    – DWKraus
    Commented Mar 2, 2021 at 16:54

Nuclear shaped charges.


Nuclear shaped charges refers to nuclear weapons that focus the energy of their explosion into certain directions, as opposed to a spherical explosion. Edward Teller referred to such concepts as third-generation weapons, the first generation being the atom bomb and the second the H-bomb. The basic concept has been raised on several occasions, with the first known references being part of the Project Orion nuclear-powered spacecraft project in the 1960s. This used beryllium oxide to convert the X-rays released by a small bomb into longer wavelength radiation, which explosively vaporized a tamper material, normally tungsten, causing it to carry away much of the bomb's energy as kinetic energy in the form of tungsten plasma. The same concept was explored as a weapon in the Casaba/Howitzer proposals...

Princeton nuclear physicist Dan L. Fenstermacher stated that there is a fundamental problem associated with the Casaba Howitzer concept that becomes dire at higher yields: a good portion of the bomb's energy inevitably becomes black-body radiation, which would quickly overtake the propelled mass. This poses the risk that most of the particles will be vaporized or even ionized, rendering them useless for dealing damage to the target.

Shaped charges are effective antitank weapons. The energy of the charge is focused on a very small area. The armor itself becomes the weapon as it is liquified and sprayed into the tank.

Your nuclear shaped charge operates on the same principle but with exceedingly more awesomeness. The energy of the nuclear charge is focused on a small area of armor and converts it to fast moving gas or even ions. These form a cone of destruction that spread inward thru the ship. The CGI for this would be great: a small red circle appears on the near side of the ship and on the far side the cone exits the ship in a spray of red hot ship innards.

I will add that in my vision of this, ships are all robotic and the robots are all backed up to the cloud, so no-one gets hurt but the ship. And it is nonsentient, not one of those really cute spaceship AIs like on Andromeda.

  • $\begingroup$ If I'm understanding your link right, it seems that the current understanding of the efficiency of Nuclear shaped charges per impact area seems to actually be lower than an omni directional nuke. This could still be a good idea but you might need to include some caveat that addresses this. $\endgroup$
    – Nosajimiki
    Commented Mar 2, 2021 at 14:45
  • $\begingroup$ @Nosajimiki - I think you are right. I took away that this is partly because the shaped nukes are as small as a nuke can be made. $\endgroup$
    – Willk
    Commented Mar 2, 2021 at 15:13
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    $\begingroup$ I think the issue is that mini nukes don't scale linearly with size. So, when you start looking a mini-nukes like the M28, you only get a 0.02kt explosion out of a 23 kg warhead, but if you scale it up just a bit you can have something like a W25 which gives you a 1.5kt weapon for 100kg. The only nukes that can actually get close to the taylor limit (6kt/kg) are in the 250kg and greater range, en.wikipedia.org/wiki/Nuclear_weapon_yield#/media/… $\endgroup$
    – Nosajimiki
    Commented Mar 2, 2021 at 17:16
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    $\begingroup$ came here to comment this. Without shaping the charge, >50% of your energy (closer to 50% the closer you detonate to the target) is just going into empty space. Shaping the charge you can get much higher rates of return on your yield $\endgroup$
    – Tristan
    Commented Mar 3, 2021 at 10:12

Space, as the good book says, is big. That means that it takes a long time for any projectile you throw at an enemy to reach time. Nukes are tough, but it'll be awkward to have them survive a coilgun or something accelerating them at a million gees, which means in order to get your nuke to their ship promptly you need big energetic rockets and they're easy to spot from tens or hundreds of thousands of kilometres away.

Nukes are definitely vulnerable to radiation, so nuclear tipped interceptor missiles are practical. Effective lasers and railguns and particle beams are awkward to make but not impossible, making the chances of getting within 100km tricky, to say the least. Your enemy has defenses, and can see you coming from minutes or even hours away.

What you need, then, is a weapon that can strike promptly, from considerable range. Just blowing up a nuke in space is pointless, as the old inverse-square law means that unless you are very close indeed to your target you just won't be able to hurt them, and the chances of getting close enough.

Happily, people have thought about this issue for you. Here are the top three from the old SDI era:

  • Project Excalibur suggested bomb-pumped x-ray lasers. X-ray lasers are potentially very powerful, but very hard to make (due to the whole inability to reflect or focus the beam). Nukes are so powerful though that even converting 1% of the blast to directed x-rays would be extremely effective. The project suggested as many as 50 laser assemblies, each with their own targetting and pointing systems, capable of engaging separate targets.

    Obviously cold-war era tech couldn't possibly deliver this, but you're in the future! Project Rho has more information, including a mention of the existence of bomb-pumped gamma ray lasers too. These are obviously better because you can call them "grasers", whereas "xaser" is just a bit awkward.

    The range of these devices will be limited, due to the impracticality of x-ray lenses (which do exist, but are totally unsuitable here) but you should expect to get a good 100km or more. Softer targets could probably be taken out at 1000km, but at 10000km the radiation flux would be just too low to be useful.

  • The Casaba Howitzer grew out of the design work done on Project Orion propulsion units. Loosely speaking, using a carefully shaped warhead to irradiate a disc of suitable material creates a directed blast, concentrating 10-80% of the bomb's oomph in a relatively small cone (say, 22.5° angle) ahead of it. The blast is made of dust and hot plasma and so hits rather harder than the flash of radiation from an unmodified bomb.

    Quite what the range would have been I'm unsure... probably not tens of thousands of kilometres, but potentially more than 100km. ToughSF imagines a large device of this type might be able to reach out to 1000km or more and kill a hardened target, though I'd take that kind of extrapolation with a pinch of salt.

  • A kind of nuclear shaped charge was also proposed... an explosively formed penetrator driven by a nuclear explosion. In theory it could have formidable speed and striking power, though aiming it from a distance might be tricky. ToughSF waxes lyrical about these, imagining incredible velocities and ranges, but in reality it is astonishingly difficult to deliver much energy to the projectile without blowing it to bits or vapourising it outright. I'd treat suggestions that you can fling a tonne of projectile at a few hundred km/s as such wild extrapolation they might actually have been drug fuelled.

    I have a reference of some very poor test results on these which I can't find right now, but in your imagined future you could handwave their practicality.

I'm sure you can imagine other weapons that could be potentially driven by a nuclear blast if you could somehow capture the energy efficiently, but these three (laser, plasma, projectile) wrap up the major classes of ranged weapon.

Also note that in combat in low orbit around a planet with a magnetosphere and an atmosphere, nuclear explosions could cause

  • high altitude nuclear EMP. This will be as effective on ships in space as it is on targets on the ground, making low orbit a dangerous place for anybody to be when the nukes are flying around. Some degree of hardening of warships will obviously be done, but making a ship immune to very powerful electrical fields will likely be impractical and you might expect it to blind sensors and damage exterior weaponry and any missiles in flight, all without getting within a few hundred km of the target.
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    $\begingroup$ couldn´t you, in theory, shoot a under-critical mass of weapons grade material out of a rail gun and then quickly shoot another mass at slightly higher speed too meet the charge at the desired impact point and thus become critical and explode? I mean as far as I know, that´s what happens inside an atomic bomb anyways. $\endgroup$
    – Daniel
    Commented Mar 2, 2021 at 12:59
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    $\begingroup$ @Daniel the earliest bomb designs were a little like that (Thin Man and Little Boy) but everything is implosion-type these days because you get better control over which bits go critical and when, so your burnup fraction is higher and you get more boom. Also, a pure fission weapon just doesn't have that much oomph compared to a thermonuclear device. Your plan might be feasible, but a bit wasteful of valuable fissiles and rather less destructive than you might think. $\endgroup$ Commented Mar 2, 2021 at 13:41
  • $\begingroup$ (also harder to hit stuff, cos your uranium slugs can't be guided like missiles can) $\endgroup$ Commented Mar 2, 2021 at 13:42
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    $\begingroup$ @Daniel also, from recollection, the book Here Be Dragons had a subcritical fissile mass in a coilgun round that would be compressed to critical density on impact, so you could execute your plan with a single projectile, if you really wanted. $\endgroup$ Commented Mar 2, 2021 at 13:44
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    $\begingroup$ "I'd treat suggestions that you can fling a tonne of projectile at a few hundred km/s as such wild extrapolation they might actually have been drug fuelled." IIRC that's something that actually happened to a "nuclear hubcap" during nuclear bomb tests on Earth, and IIRC got launched faster than the Solar System's escape velocity. $\endgroup$
    – nick012000
    Commented Mar 3, 2021 at 3:27

Regarding the question "...is it realistic to expect a nuclear warhead to survive the impact of penetrating a ships armor?", most likely no, based on indirect evidence.

These values are for existing technology today. Since this is sci-fi and the querent hasn't specified the science-based tag, they could probably handwave a one to two order of magnitude improvement to try to make the scenario work but even this is countered by the fact that projectile velocities have to be much higher than present day tech to make space combat work. So most likely, a nuclear warhead within a shell that impacts a spacecraft simply disintegrates without detonating. One can try to work around this by starting the detonation just before impact but the tiny time window involved makes that rather implausible as well.


I'd say "yes", even for a classic armoured shell, despite some answers. There are many ways to do damage, but in this answer I focus on a classic penetrating weapon as envisaged in the question.

Penetrating power is a function of shape (pointed or round?), material (soft or hard?), and momentum (speed x mass, also consider density). Depleted uranium is used in land warfare because its extremely dense hence greatly increases momentum.

A hull penetrating weapon would be viable,with an optimised shape and appropriate material, the stronger the hull the more massive and/or speedy the weapon. But as noted in other answers, your electronics can't take the force of such an impact.

What's being overlooked is, they don't have to.

The breaching tip does not have to be rigidly linked to the payload. Think about how a car would behave in a medium speed collision with a 10m thick solid concrete wall; the humans have soft seats, restraints that yield a little, airbags, the car has crumple zones........ They aren't rigidly decelerated at the exact speed the front bumper is, when it hits the wall.

So I could imagine several configurations. Here's 2:

  1. Weapon comprises a hull penetrating front, and a hollow sprung (or fluid cushioned) payload cylinder behind it with free-moving payload, payload relatively slowly decelerated by impact.
  2. Two part weapon, bearing in mind how serious a hull breach would be - both fired a computer controlled time apart, so that warhead at 40 cm width arrives at the hole, about 0.3 - 1.5 seconds after penetrating part creates an 80 cm hole. It has in-flight navigation that tracks the penetrator, then recognises the hole, and dead-centres it. Warhead only needs light protection as the bulk of the opening and depth is already created, just may have to travel/scrape (less speedily and with much less deceleration) through still-moving impact zones. Could even be detonated in-flight between passing the hull and hitting whatever finally stopped the penetrator (a bit like an airburst nuke, detonation can be timed that precisely...), so it never actually hits anything too hard before exploding. Should be doable in many ways.

I agree with Nosajimiki's answer that a nuclear-armed missile doesn't need to penetrate a ship to destroy it.

As for whether it is "realistic to expect a nuclear warhead to survive the impact of penetrating a ships armor so that it can detonate inside the ship as intended", yes, very much yes. Beyond realism, it's existing technology since the 1950's.

https://en.wikipedia.org/wiki/Nuclear_bunker_buster#List_of_US_nuclear_bunker_busters https://en.wikipedia.org/wiki/Mark_8_nuclear_bomb

"According to one government source, the Mark 8 could penetrate 22 feet (6.7 m) of reinforced concrete, 90 feet (27 m) of hard sand, 120 feet (37 m) feet of clay, or 5 inches (13 cm) of hardened armor-plate steel. "


[Purely ficitional]

Considering that military level spaceships should at least have hull components to withstand conventional ballistic weapons and plasma rounds, it is unlikely a nuclear missile is going to be too effective in terms of penetrating power;

Ultimately, it really depends on how fast the missile is; If a nuclear missile can induce a hull breach, any standard munitions can breach it easily; considering hull breaches are incredibly dangerous in the vacuum of space (solar radiation, explosive decompression, breathing problems, heat, etc), it would be arguably more cost-effective to shoot 100 standard missiles than 1 nuclear missile;

So I guess no, even if you can breach with a nuclear round, it would not be a good choice in a military setting;


I would fully expect all operators of explosive weapons to attempt to direct detonations at distance of maximum effectiveness. Which could be to just alter the orbit of the target.

But if the weapon was not armed, or trigger systems failed, and it was an implosion type devices, then yes a KABOOM could easily be mitigated down to a bang upon impact. Still would probably be a ship shattering bang though. I make the distinction of implosion device since they are more delicate in timing then a gun type that the sudden stop can be the trigger. But an operator of the weapon would not let a fizzle happen, they would make it explode on or before contact of the target.

The other thing to consider, the explosion will move the ship. If the explosion is large enough and the ship light enough, the sudden acceleration will kill the crew and destroy the more delicate parts of the ship. Which for most typical ships and nuclear weapons, that will be yes.

The energies involved with nuclear weapons make it such that the best defense will be diplomacy, and appeals to economic self interest. Because practically speaking by the time a ship has enough armor (with our current knowledge), its no longer a ship. It is a habitat inside a planetoid.

The scenarios that would cause nuclear weapons to be less lethal in my opinion: Ship dimensions are measured in KM and have 100m+ thick ice armor. They are not ships, but stations inside planetoids with in excess of 300m of rock/ice shielding. The incoming weapons are destroyed far away from the ship.

Yes, nuclear weapons are destructive.

Explosions are very effective at damaging things. Bigger explosions will damage more.


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