I Nuclear Explosion in Space… How would it work?

Did a quick search of an explosion in a vacuum and got most of what I was looking for, but on CBS Sunday morning they had a segment on restoring and reevaluating all of the immense footage of America's atmospheric nuclear testing program. They showed some amazing footage of the expansion of the fireball and then the commensurate shock wave. It is clear, that a terrestrial blast would involve both the immense nearly instantaneous EM radiation expansion, but most of the damage occurs from the 700 mph shock wave. In a vacuum I believe there would be no shock wave, but there would still be the expanding ball of radiation that would do damage, but would it still be as devastating? What kind of damage would it be? How would it dissipate?
 
189
90
Did a quick search of an explosion in a vacuum and got most of what I was looking for, but on CBS Sunday morning they had a segment on restoring and reevaluating all of the immense footage of America's atmospheric nuclear testing program. They showed some amazing footage of the expansion of the fireball and then the commensurate shock wave. It is clear, that a terrestrial blast would involve both the immense nearly instantaneous EM radiation expansion, but most of the damage occurs from the 700 mph shock wave. In a vacuum I believe there would be no shock wave, but there would still be the expanding ball of radiation that would do damage, but would it still be as devastating? What kind of damage would it be? How would it dissipate?
Standard damage breakdown for tactical-level nuclear explosion:
50% shockwave
25% instant radiation
10% heat
15% radioactive pollution

Basic rule is what damage of nuclear explosion in space is reduced by 65% (in the yield range of tactical warheads), due much reduced shock-wave and no radioactive pollution.
Residual of nuclear blast damage in space is 70% damage from penetrating radiation and 30% from heat. Larger warheads will have higher heat percentage due self-shielding. Also, space explosion do not have radiation diminishing with distance as rapidly as with terrestrial explosions.

Overall, i suspect for most cases of nuclear explosion in space the kill radius will be determined by penetrating radiation.
 
Is the penetrating radiation of same in a fusion bomb vs. fission? I know that a small fission bomb serves as the trigger for a fusion bomb, but it would have very little effect on yield. Would there be any shock wave at all since there is no medium to carry it?
 
189
90
Is the penetrating radiation of same in a fusion bomb vs. fission? I know that a small fission bomb serves as the trigger for a fusion bomb, but it would have very little effect on yield. Would there be any shock wave at all since there is no medium to carry it?
Regarding penetrating radiation, fission and fusion bomb radiation pulse differ in small details which make difference only to design of lightly shielded automatic spacecraft.
Small shockwave is still formed from the material of bomb itself, even in vacuum. It is not likely to damage assets far enough to survive an initial radiation and heat pulse. Some space war scenarios i seen use the shockwave (fireball) of nuclear explosion in space to blind radar sensors of target, for tandem-warhead style attacks against targets (spaceships) with active defenses.
 
In other words, almost all of the effect would be EM. At 50 million degrees anything solid in the bomb's construction would be reduced to plasma in a nanosecond. Without any other medium there's nothing for the energy to dissipate against. The EM would continue outward forever until absorbed by matter somewhere in the cosmos. I doubt that explosive weapons would be very effective in space for that reason. Kinetic, on the other hand would be effective.
 
1,561
189
I doubt that explosive weapons would be very effective in space for that reason. Kinetic, on the other hand would be effective.
Would it be possible to combine both concepts by using a nuclear warhead to propel projectiles?
 
511
60
Would it be possible to combine both concepts by using a nuclear warhead to propel projectiles?
Isn't that basically the same as a weaponised version of a nuclear propulsion rocket as in Project Orion?
 
1,561
189
Isn't that basically the same as a weaponised version of a nuclear propulsion rocket as in Project Orion?
Yes, that's what I had in mind. But how effective could that be with just a single pulse unit?
 
189
90
Yes, that's what I had in mind. But how effective could that be with just a single pulse unit?
Marginally effective. 10 km/s shrapnel or 80 km/s jet can be produced, with roughly 5% mass efficiency (i.e. 20-ton warhead producing 1 ton of projectiles). Make sense as weapon in very specific technological settings - large yet fragile spaceships with poor propulsion. This topic is related to "Casaba Howitzer" concept.
 

Drakkith

Staff Emeritus
Science Advisor
2018 Award
20,358
4,079
Keep in mind the total energy released by the weapon is the same regardless of where it is detonated. The difference is how that energy is proportioned.
 

davenn

Science Advisor
Gold Member
8,409
5,082
Basic rule is what damage of nuclear explosion in space is reduced by 65% (in the yield range of tactical warheads), due much reduced shock-wave and no radioactive pollution.

I doubt that there would be any shockwave ... a shockwave is a mechanical wave (like a sound wave) it needs a medium to travel in
Unless it was set off in the middle of a gaseous mass aka a nebula or a planetary atmosphere, or a dense part of the asteroid belt etc, there would be no shock wave

Dave
 

A.T.

Science Advisor
9,345
1,376
Standard damage breakdown for tactical-level nuclear explosion:
50% shockwave
25% instant radiation
10% heat
15% radioactive pollution

Basic rule is what damage of nuclear explosion in space is reduced by 65% (in the yield range of tactical warheads), due much reduced shock-wave and no radioactive pollution.
I don't get this 65% reduction. The total released energy is still the same. So the energy that didn't go into the shock-wave, must go somewhere else, like radiation. But it cannot just disappear.
 

jrmichler

Science Advisor
655
545
The original mass of the weapon is still there, minus a small percentage that was converted to energy, but as a fast moving plasma with kinetic energy and momentum.
 

A.T.

Science Advisor
9,345
1,376
The original mass of the weapon is still there, minus a small percentage that was converted to energy, but as a fast moving plasma with kinetic energy and momentum.
Are you replying to my post #12?
 
189
90
The original mass of the weapon is still there, minus a small percentage that was converted to energy, but as a fast moving plasma with kinetic energy and momentum.
Shockwave of embryonic fireball in vacuum explosion is still here - it formed from outer parts of bomb itself. Being hot and fast, it carry same energy (~50% of bomb energy) as normal airburst shockwave, but at much reduced momentum, resulting in reduced damage. It is the same effect as with conventional grenade shockwave being much more damaging underwater.
Roughly, 1Mt vacuum nuclear explosion in vacuum produce 1 ton, 2.7 PJ shockwave moving at ~2400 km/s.
In near-surface nuclear airburst, secondary fireball at 50m radius weights ~700 tons with same 2.7 PJ energy, producing ~26 times more impulse which is actually doing majority of shockwave damage.
 
Last edited:
I think you answered part of what I was thinking. The case does form a plasma and that is part of the fireball. Seems to be that nukes in space would only be truly effective if the blast was close enough that EM would overwhelm the target, probably kilometers, not tens of kilometers.
 
Last edited:

davenn

Science Advisor
Gold Member
8,409
5,082
Shockwave of embryonic fireball in vacuum explosion is still here - it formed from outer parts of bomb itself. Being hot and fast, it carry same energy (~50% of bomb energy) as normal airburst shockwave
again, a shockwave needs a medium ... there isn't one in space unless in the situations I stated earlier
If you look at large explosions, nuclear or otherwise ( in the atmosphere, on the ground the shockwave is travelling very much faster
than the rest of the material expelled out from the blast
 

davenn

Science Advisor
Gold Member
8,409
5,082
Shockwave of embryonic fireball in vacuum explosion is still here - it formed from outer parts of bomb itself. Being hot and fast, it carry same energy (~50% of bomb energy) as normal airburst shockwave, but at much reduced momentum, resulting in reduced damage. It is the same effect as with conventional grenade shockwave being much more damaging underwater.
Roughly, 1Mt vacuum nuclear explosion in vacuum produce 1 ton, 2.7 PJ shockwave moving at ~2400 km/s.
In near-surface nuclear airburst, secondary fireball at 50m radius weights ~700 tons with same 2.7 PJ energy, producing ~26 times more impulse which is actually doing majority of shockwave damage.
where are you getting these figures from ??
 
189
90
where are you getting these figures from ??
Calculated right now.
again, a shockwave needs a medium ... there isn't one in space unless in the situations I stated earlier
If you look at large explosions, nuclear or otherwise ( in the atmosphere, on the ground the shockwave is travelling very much faster
than the rest of the material expelled out from the blast
You use narrow definition of shockwave (i admit it is standard sanctified by wikipedia) which i feel may be over-constrained for historical reasons. I use more broad definition of shockwave as "phenomenon exhibiting sharp and moving discontinuity of pressure, temperature and density" which do not rely on any medium.
 
Last edited:
1,561
189
This topic is related to "Casaba Howitzer" concept.
Many thanks for this key word. I wasn't aware of the Casaba Howitzer. It seems that such devices have already been experimentaly tested for the SDI program. There is a wide range of possible configuration from nuclear explosive formed projectiles to nuclear powered particle beam weapons and they would be very effective in space. Thus the answer to the OP depends on the type of the warhead. First- and second-generation nuclear weapons (non-isotropic fission or fusion bombs) are far less devastating in vacuum compared to air. Due to the missing medium in space the resulting damage would be limited to a short range. In case of Casaba Howitzer type third-generation nuclear weapons it is the other way around. In space the plasma beam would be devastating even over very large distances (depending on the design up to thousands of kilometres) but it would be almost immediately stopped in air (turning the Casaba Howitzer into a normal nuclear warhead).
 

.Scott

Homework Helper
2,178
687
When I was 9 and 10 years old, I remember seeing the really great Aurora Borealis almost every night from northern Massachusetts.
I wondered for many years afterwards when things would be so good until I read about "Operation Fishbowl" and "Starfish Prime".
Here is a link to the Wiki page: https://en.wikipedia.org/wiki/Starfish_Prime#Explosion

I doubt that any kind of explosion in a vacuum is going to create the same type of shock wave you see in the atmosphere. Instead of an abrupt shock wave front, I would expect gas and particles expanding without interference and without significant interaction.

As for the damage, it is very extensive. From the wiki article:
The Starfish Prime electromagnetic pulse also made those effects known to the public by causing electrical damage in Hawaii, about 898 miles (1,445 km) away from the detonation point, knocking out about 300 streetlights, setting off numerous burglar alarms and damaging a telephone company microwave link. The EMP damage to the microwave link shut down telephone calls from Kauai to the other Hawaiian islands.
While some of the energetic beta particles followed the Earth's magnetic field and illuminated the sky, other high-energy electrons became trapped and formed radiation belts around the Earth. ... The weaponeers became quite worried when three satellites in low Earth orbit were disabled. These included TRAAC and Transit 4B. The half-life of the energetic electrons was only a few days. At the time it was not known that solar and cosmic particle fluxes varied by a factor 10, and energies could exceed 1 MeV. In the months that followed these man-made radiation belts eventually caused six or more satellites to fail, as radiation damaged their solar arrays or electronics, including the first commercial relay communication satellite, Telstar, as well as the United Kingdom's first satellite, Ariel 1. Detectors on Telstar, TRAAC, Injun, and Ariel 1 were used to measure distribution of the radiation produced by the tests.

In 1963, it was reported that Starfish Prime had created a belt of MeV electrons. In 1968, it was reported that some Starfish electrons had remained for 5 years.
 
Last edited:
Standard damage breakdown for tactical-level nuclear explosion:
50% shockwave
25% instant radiation
10% heat
15% radioactive pollution

Basic rule is what damage of nuclear explosion in space is reduced by 65% (in the yield range of tactical warheads), due much reduced shock-wave and no radioactive pollution.
I don't get this 65% reduction. The total released energy is still the same. So the energy that didn't go into the shock-wave, must go somewhere else, like radiation. But it cannot just disappear.
I think there is a mistake here also. Isn't the shockwave from heat? If so then the %damage from heat would go up.

Obviously, "heat" in a vacuum is not convective. I agree that in a vacuum the energy dissipates as primarily EM, with a portion as particle radiation. But there may be less lost. The net energy has to be the same, and if it doesn't generate a shockwave, it has to generate EM.

Of that EM, the infrared would be intensely hot, and would melt a lot of things. I don't know the distribution of energy vs wavelength, but it would make some sense that an explosion with temperatures of the sun, would have intense IR.

I'm not sure damage would be as devastating, but I don't think the shockwave energy would just be just lost from the energy budget produced. If it shows up as IR, that has some damage potential.

The blast radius for Hiroshima was something like 1.6 km. I would think the same explosion in space would have a reduced radius of damage. But not 35%. It seems like the shockwave energy would have to show up in the damaging energy equation, even if there is no shockwave.
 
Am I right in thinking if such an explosion occurs in the near vicinity (less than 100 metres say) of a large mass (rock, Moon surface construction or Space craft), the expanding force will convert to a shockwave in the material of the object? Thus damage will occur in this was in addition to EM (for electronics) and heat. Thanks.
 
189
90
I'm not sure damage would be as devastating, but I don't think the shockwave energy would just be just lost from the energy budget produced. If it shows up as IR, that has some damage potential.

The blast radius for Hiroshima was something like 1.6 km. I would think the same explosion in space would have a reduced radius of damage. But not 35%. It seems like the shockwave energy would have to show up in the damaging energy equation, even if there is no shockwave.
If you have linear relation between heat and damage then you are right. In fact, the pulse heat (IR/visible/UV) damage is demonstrating saturation - due ablation effects. To say simple, over-powered heat pulse spend most of its energy over threshold to heat smoke emitted from exposed surfaces, and therefore mostly wasted.
Am I right in thinking if such an explosion occurs in the near vicinity (less than 100 metres say) of a large mass (rock, Moon surface construction or Space craft), the expanding force will convert to a shockwave in the material of the object? Thus damage will occur in this was in addition to EM (for electronics) and heat. Thanks.
True.
 
If you have linear relation between heat and damage then you are right. In fact, the pulse heat (IR/visible/UV) damage is demonstrating saturation - due ablation effects. To say simple, over-powered heat pulse spend most of its energy over threshold to heat smoke emitted from exposed surfaces, and therefore mostly wasted.
Interesting. It's weird that you can have that much energy and so much of it in non-damaging forms. My guess was that heat damage would increase ... not linearly but still significantly. But if the IR is already saturated, then it might just be a bright flash of light in space.
 

Want to reply to this thread?

"Nuclear Explosion in Space… How would it work?" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Top Threads

Top