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Would a nuclear bomb surrounded by large amounts of separate shotgun-like slugs be a good anti-fleet weapon in space? If yes, how could you counter it?

(If there is a better StackExchange for this question then please say so, I am new to this.)

EDIT:

Thank you very much for all of the quick answers and comments. I can now understand why this would be an,"usele... er, inefficient weapon," as it was put by Renan. Would it be possible to avoid the problem of guidance and range with sheer numbers of slugs (and power of bomb)? Would stacking layers of slugs on top of each other be more effective? (I am assuming that the slugs are made of some impossible material that is exactly like lead except for the melting and boiling points which are somehow not possible to achieve (like in JBH's answer))diagram of multiple layers?

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    $\begingroup$ One would think battle spaceships might be protected against fast-flying space rocks / metal / shotgun slugs. $\endgroup$ – Willk Apr 19 '18 at 20:23
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    $\begingroup$ Actually, I don´t agree with most of the answers. This is the basic principle of a handgrenade. Most SAM´s are working on the same principle. I don´t see why a space-anti-ship-missile should not do this in an up scaled nuclear version. $\endgroup$ – Daniel Apr 19 '18 at 21:48
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    $\begingroup$ My first impression at this title was a shotgun that fires "slugs", i.e. the mollusk. Imagine those guys around a nuclear bomb. $\endgroup$ – Riker Apr 19 '18 at 22:36
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    $\begingroup$ @Riker Battle for Slugterra goes nuclear $\endgroup$ – RozzA Apr 19 '18 at 23:57
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    $\begingroup$ I think it would be more effective as a "shotgun shell"/canister shot more than as a bomb. The problem with spherical explosives is that it goes all over the place and you waste a lot of energy. Canister shots still have some spread if you want to hit multiple targets but it's much more concentrated and has more range. $\endgroup$ – Hawker65 Apr 20 '18 at 9:39

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People are having no fun with this question... Let's have fun...

Let's make an outrageous but perfectly normal assumption in the world of SciFi:

  • Each 100 gram pellet is made of a remarkable alloy of Unobtainium and Adamantium, the result of which is completely indestructible when subjected to a thermonuclear explosion of 100 MT. They might glow a little, which would be cool to watch, but they're indestructible. So say we all.

Our anti-fleet weapon (call it a doomsday bomb, 'cause it'll hurt everyone nearby, friend or foe) can release up to 417 PJ (yup, peta-joules) of energy in a single go. Admiral Humbug has that sucker packed with about 5,000 of our fancy pellets.

That's about 83 TJ per pellet (we're going to completely ignore loses due to space between pellets, imperfections, blah, blah, blah. We're looking for ideal maximum velocity here). If I recall my math correctly...

Joules = $\frac{1}{2}\times m\times v^2$

Which means our nasty little pellets are bookin' at 40.7 Km/s. Sucks to be my enemy!

Problems

  • Outer space is big. The odds of ships being particularly close are low. That means you need a BIG boom with a LOT of pellets. Cluster bombs are generally only useful in close quarters. So, realistically, how close are the ships? If they're within mere kilometers (about touching by space standards), this will be effective. If they're separated by 10,000 klicks, this'll be just about useless.

  • Ships must be designed to take a beating while flying through space. There's dust and debris (asteroids come in sizes smaller than kilometers, we just don't generally care about the little guys) and your ship must have some way to take the pounding (shields or armor). Whatever that is, it will absorb some if not all of your pellet's energy. This is an issue only you can resolve... given the "cruising speed" of your ship and the equation above, how much mass can your ship withstand? Very simplistically (i.e., I'm assuming at "cruising speed" you can't be hurt by what you hit "normally") we calculate... cruising velocity squared $\times\frac{X}{2}$ = 83 TJ, solve for X. If X is greater than 50 grams, this is only partially effective. If it's greater than 100 grams, this bomb is just a party favor.

  • Remember, that bomb goes off in all three dimensions. There isn't a way to force the energy in just one direction. That means it's only useful as an "up yours!" bomb (e.g, you're going to lose the fight, so you're going to take your enemy with you). You could argue that you'll set it and run, but wouldn't your enemy follow?

  • Finally, remember that your energy is distributed among all the pellets. Adding more pellets means less energy per-pellet. It's a balancing game, because to get all the energy you need to completely surround the bomb. That means at least two "pellets" are required (two halves of a sphere). Don't get trapped in the idea of "what if I have 100,000 pellets! Then distance won't matter!" but they'd probably just bounce off the ships 'cause they each have 1/20th the energy.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Apr 24 '18 at 3:23
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This was a real weapons design considered in the 1980's, and projected to propel pellets in a fairly focused beam at up to 100km/sec.

Up to 5 percent of the energy of a small nuclear device reportedly can be converted into kinetic energy of a plate, presumably by employing some combination of explosive wave-shaping and "gun-barrel" design, and produce velocities of 100 kilometers per second and beam angles of 10-3 radians*. (The Chamita test of 17 August 1985, reportedly accelerated a 1-kilogram tungsten/molybdenum plate to 70 kilometers per second.† ) If one chooses to power 10 beams by a single explosion, engaging targets at a range of 2,000 kilometers with a kill energy of 40 kilojoules per pellet (one pellet per square meter), then such a device would require an 8-kiloton explosive and could tolerate random accelerations in the target, such as a maneuvering RV or satellite, of up to 0.5 g (5 m/s2).‡

The initial plate for each beam in this Casaba-like device would weigh only 32 kilograms but would have to fractionate into tiny particles to be an effective weapon—4 million evenly spaced pellets to produce one per square meter at 2,000 kilometers range. If such pellets could be created uniformly, which is highly questionable, then, at a velocity of 100 kilometers per second, they would each weigh 8 milligrams, carry 40 kilojoules of energy (the amount of energy in 10 grams of high explosive), and travel 2,000 kilometers in 20 seconds. Such hypervelocity fragments could easily punch through and vaporize a thin metal plate and could cause structural damage in large soft targets such as satellites and space-based sensors, but they would have little probability of striking a smaller RV, or even disabling it if a collision did occur.§

http://www.projectrho.com/public_html/rocket/spacegunconvent.php

A slightly more detailed description is here:

"Up to 5 percent of the energy of a small nuclear device reportedly can be converted into kinetic energy of a plate, presumably by employing some combination of explosive wave-shaping and "gun-barrel" design, and produce velocities of 100 kilometers per second and beam angles of 10^-3 radians: (The Chamita test of 17 August 1985, reportedly accelerated a I-kilogram tungsten/molybdenum plate to 70 kilometers per second. t) If one chooses to power 10 beams by a single explosion, engaging targets at a range of 2,000 kilometers with a kill energy of 40 kilojoules per pellet (one pellet per square meter), then such a device would require an 8-kiloton explosive and could tolerate random accelerations in the target, such as a maneuvering RV or satellite, of up to 0.5 g (5 m/s2).*

Third generation nuclear warheads could also be used as the drivers for extremely powerful HEAT or Explosively Forged Projectile (EFP) weapons, delivering a slug of metal or a high speed jet of liquid metal at the target (useful for smashing armoured targets or blasting moons and asteroids).

The most advanced version of this idea was the "Casaba Howitzer", which ejected a star hot stream of plasma at a narrow angle, delivering laser like energy without the bulk and expense of all that laser machinery. The device would resemble the "Pulse unit" of an ORION nuclear pulse spacecraft, channeling much of the energy of the device through a small hole into a "filler channel" and using the energy to vapourize a plate of material to become the energetic plasma:

enter image description here

The ORION pulse unit. Nuclear devices to focus the energy of the blast would resemble this

So using nuclear devices to "drive" materials or energy into a target allows you to use nuclear weapons at longer ranges in space (bypassing the inverse square law), and generate the target effects you desire, such as stripping away external fittings and damaging light components (a "nuclear shotgun"), cracking open hard targets (HEAT and EFP weapons) and even blasting targets with laser like energy (Casaba Howitzers).

Choose your weapons.

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    $\begingroup$ Light fuse, and get away FAST! $\endgroup$ – Solomon Slow Apr 20 '18 at 0:46
  • $\begingroup$ I disagree about the inverse square law. The inverse square law still applies to weapons of this type--double the distance and you'll cut the delivered energy by four (or the odds of a hit are cut by four if your projectile spread is wide enough at that point.) $\endgroup$ – Loren Pechtel Apr 21 '18 at 0:48
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    $\begingroup$ A "bare" nuclear explosion in space will expend its energy in a spherical shell of X-ray radiation, and will have little effect on a ship or other object after about a kilometre, virtually point blank range. Look at many of the links and you now have nuclear driven weapons hitting targets at hundreds to tens of thousands of kilometres away. $\endgroup$ – Thucydides Apr 21 '18 at 3:36
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A nuclear explosion is a poor choice for this application.

In a nuclear explosion in the atmosphere, the energy largely goes into heating the gas of the atmosphere. The heated gas expands violently. This produces the shock wave and the mushroom cloud. It would definitely accelerate slugs in its path. But in space there is no gas to heat, only the materials adjacent to the explosion. Much of the energy is radiated off into space. The vaporized materials of the bomb casing makes a puny shock wave.

Consider a regular shotgun slug coming out of the shotgun. It is propelled by expanding gas from the explosive in the shell.

You could replicate this in space by using an explosive that itself turns into an expanding gas cloud, which then transfers its kinetic energy to the shells, accelerating them. For example, a keg of black powder.

If you want to use a nuclear explosion you should surround your explosive device with something that will capture the energy of your explosion and turn it into kinetic energy, ideally expanding rapidly as a cloud of gas. That accelerating gas will then push on and accelerate your shells.

A comet would work well to generate the needed rapidly expanding gas cloud..

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  • $\begingroup$ I'm sure that, apart from unobtanium and gases, just anything would become expanding gas. $\endgroup$ – Volker Siegel Apr 20 '18 at 3:10
  • $\begingroup$ Instead of a keg of black powder I would recommend smokeless gunpowder, as black powder doesn't contain its own oxidizer. $\endgroup$ – vsz Apr 20 '18 at 14:13
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  • $\begingroup$ Would not the heat radiation if undisturbed by atmosphere make the heating of everything near it much more effective? The slugs would be heated well over boiling point and pick up momentum from the heat radiation. It would be more of a plasma weapon, small blobs of super hot gas flying extremely fast in all directions. Not to speak of the heat radiation from the initial blast would be undisturbed by atmosphere that could absorb it so it would directly irradiate anything in it's visible path. $\endgroup$ – mathreadler Apr 22 '18 at 10:42
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Following on JBH's line of thinking:

When you said remember, that bomb goes off in all three dimensions, it strikes me that this is the real heart of the Problem of Space Warfare. Strategists think too low-dimensionally, too 21st century. No, the modern strategist will be thinking four dimensionally at least.

So, how to apply a nuclear powered slug-bomb to space warfare? Well, everyone knows about time travel. You know, slingshot around the Sun: you pick up enough speed, you're in time warp. If you don't – you're fried. Well, Space Patrol battle strategists do this with fleet busting bombs. It's a bomb, so they don't care if one or two get fried!

The long and short of it goes like this: long range sensor data coupled with data collected by Outer Rim fortification sensors alerts the High Command as to location, velocity, trajectory and flock arrangement of enemy vessels. Let the Battle Computer churn on that data for a while and launch the 4D Fleet Busters!

These large missile systems, always in motion and awaiting orders, will now accelerate towards the Sun. Approaching the predetermined velocity, the missiles will slingshot around Sun & enter time warp! BAM!! They disappear from all enemy tracking sensors (which wouldn't know about their course changes for some 15 to 20 minutes anyway).

At the appropriate time, according to van Wobbler's Equation, the missiles drop out of time warp and --- and this is the key to modern space warfare --- reenter normal time & space right smack dab in the middle of the enemy vessel!!!

Imagine if you will: sublieutenant Skwlarklann of the Evil Space Empire is making her routine rounds of the IHD Panthera's engineering division, in keen and patriotic anticipation of the immanent surprise attack on the insignificant enemy's star system.

She takes a well deserved sip of her latte macchiato, sets the cup down and looks up towards the Mysteriously Pulsating Crystal Warp Drive Actuator (TM) in the great arcade of the engineering division. Suddenly, there is a strong puff of air and a damp pfffffp! Momentarily suspended before the amazed sublieutenant's vision is an odd looking, dull metal device with a crude image of the Dear Leader painted in his union suit, making a rude gesture and a speech bubble saying Phuck the Empire!!!

Before anyone can react, BBBBBBBBOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMM!!!!!!!!!!!!

The small nuclear powered FleetBuster Mark VII (Patent Pending) sends a couple tons of adamantium unobtanite shrapnel shards whizzing in every direction, completely crippling the engineering division, critically damaging the environmental systems, disabling the artificial gravity and attitude control of the poor beleaguered Panthera! Large shrapnel punches through deckplates and medium strength bulkheads alike. The ship's shields and heavy armour are useless against an attack from within.

With all the capital ships and carriers destroyed or irreparably disabled, the Outer Rim Defense Force can easily mop all the smaller support vessels and fighters.

So yeah, very effective anti-fleet weapon! Timing is key!

How to defend against such an attack? That may not be such an easy thing to do!

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    $\begingroup$ "How to defend against such an attack? That may not be such an easy thing to do!" Are you sure? We can safely assume that the Evil Space Empire have mastered FTL travel, which in turn means they have mastered time travel. As we all know, Einstein's special theory of relativity equates FTL travel with moving backwards in time. -- fourth wall -- This may not strictly be true, but go with me here ... -- Hence all the ESE ships need to do is use their M.P.C.W.D.A.s to nip back in time a second or two, and at the speed they're moving the bomb will miss by a good few thousand miles. $\endgroup$ – dgnuff Apr 20 '18 at 0:50
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    $\begingroup$ I agree on the points that surely the ESE must have also mastered time travel and they could nip back a second or two. However, this is the EVIL Space Empire we're talking about here, with it's megalomaniac Transgalactic-God-Emperor-of-God-Emperors and its ginormaniac ten star general Hyper-Grand-Field-Marshall-in-Charge-of-Ten-Thousand-Starfleets running the show. Personalitywise and burocracywise, I just don't have any confidence that the ESE's tacticians will do anything but play to character! $\endgroup$ – elemtilas Apr 20 '18 at 16:33
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    $\begingroup$ + for "Immanent Surprise"! That will be the name of my space ship. $\endgroup$ – Willk Apr 21 '18 at 15:49
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    $\begingroup$ immanent: Existing or operating within; inherent. So the FleetBuster Mark VII is the immanent surprise in this story, since it does its thing inside the enemy spaceship. $\endgroup$ – David K Apr 22 '18 at 13:06
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With proper design your slugs would gain considerable velocity, but I doubt it would make an effective weapon.

Think of the slugs as miniature Orion spacecraft, which is a concept that is very well-developed and highly likely to work. The trick would be to design the pusher plates optimally, and that would require some fairly high-quality engineering.

Basically, you want the slugs to be as close as possibly to the nuke so that they accelerate as much as possible, but that costs you in numbers of slugs, and requires a more massive pusher plate. (The "pusher plate" is that part of the slug which is responsible for enduring the nuclear blast and absorbing its momentum.) It's hard to say where the optimal design is.

My guess is that in a case like this you'd design something like an ablator plate where the face of the plate towards the nuke boils away and the gas released provides some of the push.

You might do better with the nuke-pumped x-ray laser idea that was developed for the original Star Wars project. It's clearly harder to do that the DoD thought in the 80s, but that's what R&D is for.

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The shotgun bullets would be disintegrated by the nuke.

The boiling point of iron is around 3,000K.

The temperature of an area right next to a nuke blast center can easily outdo that by two orders of magnitude, probably more in space.

At this point the slugs have probably ceased being a gas or maybe even plasma.

This would make for the most usele... er, inefficient weapon ever in the history of space warfare. Even if the slugs were intact, any target would either be far enough to take the hint they should change direction (causing you to miss them completely), or close enough that the nuke will cause more damage than the slugs.

Against a planet, the slug plasma would be the smallest concern. The nuke might cause damage, but the slugs won't.

In space, projectiles only do for good weapons if they are guided. Otherwise even the slightest change in trajectory causes a projectile to miss. And you won't be able to guide those slugs.

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One of the problems I see with a nuclear-kinetic shotgun, assuming that the engineers at Muppet Labs..., er, I mean R&D can make this, is that these things will keep going until they hit something.

If they miss their primary target, they will keep going until eventually some sort of friction slows them down. I expect that after peace happens, there will still be pellets flying about.

Long-term weapons that you don't have control of aren't a good idea in space.

One weapon proposed is to set off a couple of fragmentation bombs (similar to what you've proposed) several places in Earth orbit. This would not only destroy most of our satellites, but prevent new ones from being put up. It might also prevent space travel from happening until the orbits are cleaned up of debris.

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I want to build on @JBH's answer a little.

One of the key problems mentioned there and in the comments is that if you want the pellets to have a "shaped" direction (to focus their spread and energy more efficiently), they would need something of greater mass to push off of. Newton's buzzkill of a law means that in space, just as much energy would be transferred backwards (away from the shape you want) as forwards, so even a backplate of some sort would just fly directly back at you at enormous speed. So how could we avoid literally shooting ourselves in the face?

Let's use some of our Unobtanium alloy to create a massive "core" for the warhead. It would be huge compared to the pellets, probably torpedo-shaped with an engine on the back to propel it towards the target. Then instead of a single spherical charge, it would have a ring of them around the core. The point is to make the core be the center of the explosion, which it would absorb nicely because that's what Unobtanium does. If the "backboard" for the explosions is balanced in the middle of them, the net force would cancel out and it would go nowhere.

So what limitations would this have? Well it would be a bit more complicated design for one, and it would give you a ring of projectiles instead of a sphere, but that could be a good thing because then you don't have to worry about shooting yourself or your allies. Aiming/positioning it would be a little more complicated than just a dumb bomb, but it would still allow you to angle it such that it would hit a good amount of targets.

The bonus is that you could also later recover the core, and prepare it with a new warhead (Unobtanium isn't cheap, after all, otherwise it would be called Affordium).

Here's a terrible diagram of what I mean:

enter image description here

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This Could Work

(If you change the design a bit)

The device described by the OP is basically a nuclear space hand grenade. As others have pointed out, this is problematic, because space is large, and therefore a granade that is actually dangerous to the enemy will likely be very dangerous to your own fleet as well.

So design a Nuclear Space Claymore

The Pascel-B nuclear test was an underground nuclear explosion that launched a one-ton manhole cover into the air at several times escape velocity. It would have been the first man-made object in space if drag forces hadn't vaporized it on the way up.

In space the projectile would not experience those drag forces, and would instead travel in whatever direction you fired it with tremendous speed.

So build a long, thick, hollow tube. Put a nuke at one end, and a large steel plate at the other. Insert impurities into your steel plate such that it shatters on impact, transforming into thousands of tiny, high velocity rounds.

Much of the tube is converted into an expanding cloud of superheated gas, which slams into the steel cap with incredible energy. The cap breaks apart, and is propelled in whatever direction you pointed it.

The fact that you can aim it makes it a viable weapon.

Space Claymore. Has a nice ring to it.

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Simply put, no.

In a vacuum (space) there is no atmosphere. This means that, although the radiation dose would be higher, the blast (shockwave) would disappear, and the slugs wouldn't whip through space. You'd need to physically propel them.

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  • $\begingroup$ The materials the nuke is made of will expand violently in all directions. There's your propulsion. Otherwise see my answer for why even with that, this is a very bad idea. $\endgroup$ – Renan Apr 19 '18 at 20:15
  • $\begingroup$ That's a good point, and exactly why the pellets won't go anywhere. The nuke itself will vaporize and the blast won't go anywhere. $\endgroup$ – FoxElemental Apr 19 '18 at 20:16
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    $\begingroup$ The slugs would absorb that radiation, vaporize and ionize, and you would get plumes of plasma shooting out at quite a high speed. $\endgroup$ – Elukka Apr 19 '18 at 20:20
  • $\begingroup$ @Renan, So will the materials that a chemical bomb is made from, and the chemical bomb is a whole lot less expensive to make. Explode a 100 kilogram nuclear bomb and a 100 kilogram conventional bomb in space, and you'll get the same amount of expanding hot gas from each. The difference is, the nuclear bomb will also produce a whole lotta lotta lotta extremely intense radiation. If you had exploded that same nuclear bomb in the atmosphere, the radiation would have heated millions of kilograms of air to white heat, and that's how you get a blast that can flatten an entire city. $\endgroup$ – Solomon Slow Apr 20 '18 at 0:41
  • $\begingroup$ @jameslarge yes, however a chemical bomb can get the expanding gas to only a tiny fraction of the temperature that a nuclear one will manage. And, for a given mass of gas, temperature determines the kinetic energy that the slugs can get. The problem is to prevent the bomb from also vapourizing the slugs. $\endgroup$ – leftaroundabout Apr 21 '18 at 10:01
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We invent a capacitor that is charged like MAD by radiation.

Now our missile flies into space and waits and listens for targets. When there are targets, it deploys a swarm of rail guns with enough velocity that they get a safe distance from the nuclear weapon. The rail guns have a capacitor on the back, ready to be charged. The rail guns orient. The nuke explodes, bathing the launchers in radiation. This charges the capacitors. They capacitor powers a rail gun which launches a bucket of projectiles at the target.

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Never mind the material, it’s the quantity of fragments that will be the issue. In a typical bomb (anything from a hand-grenade to an air-dropped bomb), the mass of the fragmentation material is generally on the same order of magnitude as the mass of the explosive. That means that you’d be looking at a similar mass to the TNT equivalence of your nuclear device - eg for a megaton class weapon, you’d need a million tons of pellets.

Think of it this way - if you had a bomb with a 10km blast radius, then you’d have a space in the order of 1,000km^3, or one trillion cubic metres. Put a million slugs (a pretty large number, giving you a weapon weighing several tons) and still only gives you only one small slug per 100m x 100m x 100m square. That’s not going to trouble a spaceship much.

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There's some validity to this approach. It's called a fragmentation warhead. However, frag warheads are usually detonated near the target. You describe this as an "anti-fleet" weapon, which to me implies that you aren't targeting a single craft. You're targeting a fleet in general and trying to inflict multiple causalities.

The problem is distances. A best case scenario says that these slugs spread out in a uniform disk that heads towards the target. The idea of a frag warhead is that the expected number of hits on your target (or targets) is equal to the number of fragments times the fraction of the area of the disk that your target covers. If you spread 50 fragments over a $10\text{m}^2$ disk and are trying to hit a $2\text{m}^2$ target, you expect that on average $50\times(\frac{2}{10})=10$ fragments will hit the craft.

Now space is big. Really big. Really really really really really big. That spread is going to cause problems. Let's back up and take on a more terrestrial example. A modern carrier battle group will have an outer screen of ships to detect the enemy at up to $370\text{km}$ and an inner screen of ships within about $19\text{km}$ to dispatch them. Let's pretend our carrier group is all bunched up within $20\text{km}$. The exact makeup of a carrier group isn't very specific, but for our rules of thumb, let's say its 6 destroyers (like DDG-59), 2 AEGIS cruisers, and a supercarrier. According to wikipedia, this is not an unreasonable makeup for our example purposes. The surface areas of these ships are roughly destroyer: $3000\text{m}2$, AEGIS: $3111\text{m}2$ and Nimitz carrier: $25564\text{m}2$. Sum total, that's going to be somewhere on the order of $50000\text{m}2$, or $0.050\text{km}^2$ of surface area to hit. That carrier group is spread over roughly $300\text{km}^2$ of surface, yielding a ratio of $6000:1$. This means for every $1$ hit you want on this unusually bunched up carrier group, you need $6000$ pellets. Now practically speaking, you probably wont expect a single pellet to kill a ship. These are warships, after all. You will want to multiply that by some factor.

Now let's get into space. Space is big. Really Big... Wait, I said that already. The distances between things are much larger. For the ISS, a "close approach" of debris to the space station is defined to be about $25\text{km}$ in radius. That means that the ISS seriously considers spending fuel to change course. In our seafaring example, we had all 9 of our ships bunched up to within a $10\text{km}$ radius ($20\text{km}$ diameter). If we assume the ISS was our supercarrier, with a surface area of $0.025\text{km}^2$ within this radius, we should expect to need roughly $80,000$ pellets in order to achieve a single pellet impact. Again, I would expect it to take a substantial number of hits to get a kill against a warship designed to take on not only these pellets, but the general debris in space.

In interplanetary space, the distances get larger. We don't exactly have SOPs for interplanetary fleets, but distances of $1000\text{km}$ between ships would not be unreasonable at all. At those distances, such a shotgun approach becomes simply meaningless.

So the next question is to find out how heavy your fragments are. Let's say you want to get $100$ hits on your target, with $100\text{g}$ fragments. That calls for $8$ million fragments at $0.1\text{kg}$ each, or $800,000\text{kg}$. The ISS is about $400,000\text{kg}$. Even if we drop our standards and use $10\text{g}$ fragments, it's still $80,000\text{kg}$, or $20\%$ of the mass of the space station.

Which is going to lead to visibility. The larger a weapon, the easier it will be to detect. A warfleet is going to have a vested interest in detecting weapons approaching them. A weapon that's a good fraction of the size of the ISS is going to be relatively easy to spot as it approaches.

Which brings up an interesting quirk of the weapon. You don't really need the nuke. In space, things move fast. Orbital velocities are on the order of $8\text{km/s} (8000\text{m/s}$) and interplanetary speeds are necessarily higher. At those speeds, you don't really need an explosive to impart additional velocity. Simply shoot at the craft from any direction other than from behind, and the relative velocities of the fleet vs the pellets will give you all the lethality you were going to get.

A nuke would let you achieve the desired spread quickly, by giving each particle a larger cross-range velocity. This is helpful if you want to get in close, but getting in close with a weapon that's a fraction the size of the ISS isn't realistic. You might as well impart less velocity, with a smaller explosive, and do it earlier, giving the slugs more time to spread out. This would also give you the opportunity to make the slugs into precise shapes to improve lethality, and avoid the whole "nuclear bombs like to melt things" issue.

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  • $\begingroup$ This was a very good answer. If I could have marked two answers, I would mark this one as well. $\endgroup$ – Sievert Apr 20 '18 at 16:06
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A design not too dissimilar to this is how real-world fission weapons actually work - but the effect is different to what you're imagining.

Most of the mass of an early-design fission warhead is inert ballast. The highly enriched core is surrounded by a large mass of un-enriched material purely to provide containment, by way of inertia. The material is vaporised very rapidly by the initial electromagnetic products of the nuclear chain reaction, so it has no tensile strength, but the vapour still has mass, and delays the expansion of the rapidly heating fissile region such that the chain reaction can build and thus produce a more energetic detonation.

The arrangement of (presumably) lead slugs you're envisioning would produce a similar effect, depending on how close they are to the fissionable components and how well shielded they are. They would need a kind of extremely heat-resistant 'wadding' similar to a conventional firearm in order to not be vaporised.

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The heat radiation would likely be much more efficient than the slugs.

In space there is no atmosphere so none of the blast energy gets lost to creating a shockwave. Instead you will have close to 100% of all the types of electromagnetic radiation in all directions unblocked by anything.

It would heat the surface of a ship which would need to be built by a material that would either work as a mirror to reflect ( or at least not get vaporized ) by the intense irradiation.

Now the radiation would decrease as the surface of a sphere around the blast center. We can maybe calculate how far away would be "safe" given some material the space ship is built by. But definitely it is the intense radiation and not any materia that would pose the threat of such a weapon.

The slugs would have small total area that they could hit but the radiation hits anything in the line of sight with the speed of light. You would need a super duper efficient mirror material or absorber to protect against that.

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I don't think slugs would work.

If you are going to use nuclear weapons in space, wrapping the core with iron bars, wrapping that with a heavy duty solenoid, then to set off discharge a large capacitor through the coil, when the magnetic flux reaches peak, explode the bomb. The iron bars lase in the hard X-ray, soft gamma ray range. The magnetic field keeps the columns of iron vapour contained to lase a bit longer.

If you can aim the thing with any precision, you transfer something like 10% of the energy of the weapon into his hull.

You might make a shaped nuclear charge where some 80% of the energy is in a fairly small angle. So you are sending a jet of several million degree plasma. Don't how how coherent that would be. Again, if you can set it up so it carries a magnetic field with it, it may stay more coherent. Right now these are either not made, or not discussed where I can find reports.


Overall space battles will likely be fought with missiles. They can respond to changes in vector of the target.

Compare to Earth naval warfare. Even the primitive submarines of WWII put paid to battleships. They were recycled as sea to shore batteries. And in aircombat far more is done with missles than with guns.

Space combat will be more like submarine warfare: Detection plays a huge role. Distances are large enough that the object isn't there by the time you get the signal. On the flip side it's like air combat in the absence of stuff to hide behind/under. No equivalent of thermoclines, or acoustic convergence zones.

Not clear to me if space combat will be the equivalent of submarines (launch missiles from a big ship) or more like aircraft carriers. (Missiles are carried to a closer distance to be fired.)

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