Very interesting question!
I'm going to quote several sources, so you can see that a consensus
seems to have formed.
Q: How does an explosion in space differ from that on Earth?
A: It would appear as a point or globe of light, with no huge clouds
smoke or vapor. Any such gases would diffuse very quickly. There
would also be no blast (pressure wave). That means a near miss by
torpedo would cause no damage other than from radiation.
Q: No nuclear mushroom cloud?
A: Not in space. Fallout, irradiated dust resulting from matter
by the explosion, would also be absent. Nukes are less deadly in
with no atmospheric effects. Most space habitations would also
protection from radiation, an expected hazard of space.
from, "The Science of Science Fiction" edited by Peter Nicholls:
The main hazard of space nuclear explosions is EMP (electromagenetic
The output of an atomic detonation is:
1) Blast: An explosion creates a wall of air (shock wave) which moves
outward from the fireball. In the vacuum of space this does not occur.
There is a smaller wave of vaporized bomb material, but this is minor
at orbital distances.
2) Ionizing radiation: The X-rays, gamma rays, and neutrons would be
both absorbed by the atmosphere and lowered in intensity by the
distance from the bomb (Inverse scaling)
3) Fallout: It is already pretty nasty in space. If the weapon is in
orbit, most of the fallout will have decayed long before re-entry. If
all re-enters, it will be diluted rather majorly. The most serious
pollutant would be plutonium. It is lethal in inhaled concentrations
of one millionth of a gram. The weapon will contain many thousands
grams (which implies many billions of lethal doses).
The re-entering material will be vaporized into gas. The vast bulk
will never be deposited into mammal's lungs. Even the inhaled material
will tend to be less than millionth of a gram quantity. The true
danger depends on the strength of the so-called linear-dosage
hypothesis (which is the current official standard). This is the view
that health effects do not drop off below a minimum dosage, they just
get weaker or less likely. One of its various implications means, for
example, if 1 microgram causes one cancer, then if ten people inhale
only a tenth of a microgram, then, statistically, one should develop
4) Light and heat: The light and heat should be diluted sufficiently
to minimize surface damage. (DON'T look directly at it!)
found on the Explosions in Space discussion board:
Again, in other words:
If a nuclear weapon is exploded in a vacuum-i. e., in space-the
complexion of weapon effects changes drastically:
First, in the absence of an atmosphere, blast disappears completely.
Second, thermal radiation, as usually defined, also disappears. There
is no longer any air for the blast wave to heat and much higher
frequency radiation is emitted from the weapon itself.
This effects are elaborated here:
A less well known effect of high altitude bursts, but also one with
potentially devastating consequences, is the artificial "pumping" of
the Van Allen belt with large numbers of electrons. The bomb-induced
electrons will remain trapped in these belts for periods exceeding one
year. All unhardened satellites traversing these belts in low earth
orbit could demise in a matter of days to weeks following even one
high altitude burst.
For a detailed study of the effects of such an explosion on
communicaton satelites, read here:
Search terms used:
nuclear blast space radiation explosion emp