In the Honor Harrington universe, ship-to-ship combat takes two forms: missiles and direct energy weapons.

Missiles come in two forms - bomb-pumped lasers and contact nukes. Both use multi-megaton nuclear initiations to damage enemy ships.

While this sort of event on a planetary surface will obviously have lasting effects, what long-term effects could be expected in a vacuum environment, aside from the destructive force associated with the explosions themselves, and the resulting EMP? Especially, would there be lingering (or spreading) radiation?

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    Just to note, there is NO EMP FROM NUKES IN SPACE. I wish Sci-fi authors would learn this. EMP from a nuke comes from the interaction of ionised electrons from the atmosphere travelling at high speeds and being bent by the Earth's magnetic field. A nuke emits a large X-ray burst, which ionises and accelerates the electrons from an atmosphere, but would not do so in a vacuum!
    – Nick
    Commented Oct 5, 2012 at 14:48
  • Related: How did the Galactica survive an atomic weapons hit? Commented Jan 6, 2013 at 20:33
  • @Nick I know this is old, but David Weber doesn't ever actually say that the nukes cause EMP's in space.
    – Ryan
    Commented Oct 7, 2014 at 22:07
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    @Jeff he talks about electronic interference frequently yes. The Lac's that are hit by the triple ripple have their sensors skewed up by the explosion, but their electronics still work. In fact in War of Honor it even specifies that their sensors were blinded because the mass explosion was like "staring directly into the belly of a star. It does say the word EMP right before that but he doesn't use it in the sense that we use EMP today, in the sense that electronic circuits were fried. See: bit.ly/1Euqi1r (link to google books).
    – Ryan
    Commented Oct 8, 2014 at 15:40
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    @ryan: The phrasing in that passage from WoH seems to be saying that a wave of nukes damages/scrambles electronics by overwhelming it with photons, including gamma rays. Not by inducing currents in wires with magnetic fields, like EMP usually means. "The warship sensors were hardened against EMP, but nothing had prepared them for ... that many mega-ton warheads in so small a volume of space and time." So it sounds like he's distinguishing between nuke blast vs. EMP, and saying that the nukes aren't an EMP attack. (At least, if you want to take the charitable interpretation.) Commented Nov 29, 2015 at 3:59

8 Answers 8


Space is full of radiation. Its probably one of the greatest dangers we face in space exploration that we do not have a good solution for. In 1962 the US Detonated a nuke in space. The radiation from this is just background noise. While there are likely to be some highly radioactive particles as a result of the explosion these will disperse so quickly that there would be far greater damage from the explosion in any area where these would be of a concentration to be a concern.

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    per your link the space detonated nuke was "hundreds of miles into the air", which would put it in the range of a low earth orbit. while this is technically "in space" the effects of the nuke were still strongly influenced by the Earth. As for the effect of a nuke on a space faring vessel, this would be greatly influenced by the radiation shielding of each individual vessel since the majority of a nuke's "power" is in large amount of energy released as radiation. As you pointed out radiation is a big hazard in space, so most ships should probably be well off in this regard.
    – Xantec
    Commented Jun 10, 2011 at 22:37
  • My point was by the time that the energy from the explosion had dispersed the radioactive by-products would be dispersed enough so as to be negligible with the rest of the background radiation.
    – Chad
    Commented Jun 13, 2011 at 14:13
  • Interesting. So those parts in SG-1 and other space sci-fi shows where there was "too much radiation" from some nuclear blast to do anything useful (scan, beam/transport, etc.) is...bunk?
    – Chad Levy
    Commented Nov 22, 2011 at 22:50
  • @paperjam - you could have some gravitic anomoly that collected a highly radioactive source that continually emitted radiation at a location... but yes the residual radiation from a blast will dissapate fairly quickly... that said this at supermacro and nano scales break normal laws of physics so I will concede that it is possible that some megaexplosion could create that gravitic anomoly though I would suspect it would be highly localized.
    – Chad
    Commented Nov 23, 2011 at 13:38

In space, you'd expect much the same effect from blast, radiation, and heat as in atmosphere.

Of course, with no atmosphere to "carry" the blast effect, it's going to be greatly limited. There will be little or no effect from what you might call "shrapnel"... The bomb itself is going to be vaporized and you're not going to get chunks of stuff flying around at high velocity. Both we and the Russians experimented with the effects of nuclear weapons in space, if you get a chance there's a documentary on Netflix about the development of the hydrogen bomb. It covers these space-based tests.

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    Does "we" mean "United States"? Not everybody is American here, you know, nor we know your nationality.
    – DaG
    Commented Jun 11, 2011 at 22:18
  • it seems possible that under some circumstances, you might get something like shrapnel. if the nuke weren't close enough, and the target ship was large enough, it seems like you might not completely vaporise the material on the far side.
    – JustJeff
    Commented Jun 12, 2011 at 17:46

Compared to everyday celestial events, the energy of an H-bomb is laughably tiny. The sun is something like a billion H-bombs per second. A gamma ray burst may be a billion-billion times that. So anything humans can construct is like an single ant (not a colony) attacking mount Everest (or if you want to compare to a gammaray burst a single virus attacking the enture mountain range). It just won't be noticable except in a small local area. The one thing a nuke does that is different, is generate fission products, which for the most part aren't found in space (although other radioactive isotops yes). And even these isotopes, are probably generated in much greater volume by supernovas, but unless you are in the neighborhood of a recently exploded one, they have long since decayed away.

The earth based space tests, were significant, because they happened in the very rarified earths exosphere/magnetosphere, and generated high energy particles (mostly electrons), trapped in the earths radiation belts. At the time it was feared we might have to wait decades for the activity to settle down to the undisturbed state.

  • The talk is about sci-fi in which humans can make weapons more powerful than Sun..
    – user931
    Commented Oct 24, 2012 at 5:12
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    @SachinShekhar Not in the Harrington series. They are stronger bombs then current, but no where near the strength of a sun, the writer tries to keep that somewhat reasonable in power.
    – Kortuk
    Commented Jan 7, 2013 at 19:19

The biggest hazard would have to be any macroscopic particles left over.

Gamma rays, X-rays, and other ionizing radiation would spread out at the speed of light, or nearly so for electrons, alphas, etc., and within moments be less than the radiation that always present in space. After an hour, any such radiation will be smeared out to a volume as large as the orbit of Jupiter. I.e., it's effectively gone. You'd have to worry more about minor solar flares than space nukes.

On the other hand, although most of what's in the immediate vicinity of the explosion would be vaporised to atoms (or parts thereof), it seems possible that you could end up with significant amounts of debris. Perhaps the solar wind would blow the smaller ones away, much like the effect with a comet, but some of the larger chunks would present major navigational hazards. NASA gets very concerned when millimeter sized bits float away in orbit. Obviously anything larger will be more of a concern. If you're moving around at planetary speeds, 10's of km/sec, the kinetic energy in such space junk could easily put a hole your hull.

  • Thanks. It does stand to point out though, that macroscopic particles aren't a serious threat in the HH universe, since they explicitly have particle shielding. In the few instances a ship is seen without it, they tend not to last long (mostly due to other reasons, though).
    – Jeff
    Commented Jun 12, 2011 at 20:28
  • Gamma and neutron radiation are the hardest to shield against. The effect upon materials depends upon how much energy the material absorbs. If it is enough to liquefy, vaporize, or cause to spall; then that material is lost. The effects upon the crew depend upon the amount of neutrons or gamma rays they absorb. In such an engagement, it is possible to get a known 100% lethal dose but have a life expectancy of hours or days after receiving the dose.
    – Jim2B
    Commented May 30, 2018 at 19:57

Purely for informational purpose, there has/had been some consideration of using nuclear detonations as primary propulsion for a space-faring craft.

Wikipedia: Project Orion (nuclear propulsion)

Short term effects: propulsion (most likely)!

Long term effects: ?????

  • Whether you launch the minimum sized vessel or the maximum 8,000,000 ton vessel the size of a small city, the amount of radiation released is about the same. If you are very careful about how and where you do the launch, the estimated global radiation increase should cause 1 additional death over the next ?40? years (40 is the number that sticks in my head but it may be wrong).
    – Jim2B
    Commented May 30, 2018 at 19:53

The Atomic Rockets website has a whole section devoted to describing the effects of nuclear explosions in space.

Basically, conventional nuclear weapons are far less destructive in space than they are in an atmosphere. However, there are some neat things you can do to make them more deadly.

Chief among these ideas are:

  1. Form a nuclear shaped charge (called Casaba Howitzer).
  2. Use enhanced radiation (i.e. neutron) bombs.

Here's an interesting description of how a nuclear explosion attack might look in space:

First off, the weapon itself. A nuclear explosion in space, will look pretty much like a Very Very Bright flashbulb going off. The effects are instantaneous or nearly so. There is no fireball. The gaseous remains of the weapon may be incandescent, but they are also expanding at about a thousand kilometers per second, so one frame after detonation they will have dissipated to the point of invisibility. Just a flash.

The effects on the ship itself, those are a bit more visible. If you're getting impulsive shock damage, you will by definition see hot gas boiling off from the surface. Again, the effect is instantaneous, but this time the vapor will expand at maybe one kilometer per second, so depending on the scale you might be able to see some of this action. But don't blink; it will be quick.

Next is spallation - shocks will bounce back and forth through the skin of the target, probably tearing chunks off both sides. Some of these may come off at mere hundreds of meters per second. And they will be hot, red- or maybe even white-hot depending on the material.

There's a lot more interesting material at the link. Including discussion of radiation survival and other aspects.


Obviously intense EM rad close by but the intensity decreases as the root of distance from the point source so unless you were close, as others have said, normal space rad would be a greater threat. No debris either as all matter would be vaporized and ionized. Would prob be kind of like a ripple in the solar wind. Really it's far worse exploding one at ground level and creating all those isotopic by products with nowhere to go.


I think it looks close to the video linked in this article because what was filmed in Siberia on November 14, 2014, a very big flash, was probably a high-altitude nuclear test - perhaps 50 km to 80 kms above the ground.

Take a look at the video of the flash : it expands very quickly then disappears. The light is extremely bright.

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