Nuclear weapons in deep space, how viable?

[poisonoustea]

I'm not really into hard science fiction, but this little research is crucial. I know very little of nuclear reactions, but I can see from Wikipedia that :

The energy released from a nuclear weapon detonated in the troposphere can be divided into four basic categories:[1]

• Blast—40-50% of total energy
• Thermal radiation—30-50% of total energy
• Ionizing radiation—5% of total energy
• Residual radiation—5-10% of total energy

So, here's the question: would the blast and thermal radiation diffuse properly in deep space? The list above talks about an explosion occurring in the troposphere, which is the lowest part of Earth's atmosphere, but deep space has a much lower density.

Suppose we're throwing a nuclear weapon against a ship, what would the results be?

 

[ctg]

You mean with the deep space as a vacuum, don't you? In there, the thermonuclear components wouldn't do much as much harm as what they would in the atmosphere, unless if the explosive would go in near vicinity of the vessel. However, much bigger problem would be if the nuke would be located inside or on top a asteroid, as there the explosive force can rip apart the stone, and make shrapnel to deliver kinetic energy punches to the vessel.

But do not think that the radiation would be any less, as if you would explode a nuclear bomb next to or in near vicinity, the radiation would immediately load the vessels radiation shields. You could even compare a nuclear explosion to a solar flare.

 

[poisonoustea]

So the kinetic force of a nuclear blast would still apply in deep space?

You could even compare a nuclear explosion to a solar flare.

Yes, but the sun is largely composed by hydrogen and other gases that function as catalysts for the nuclear explosions (I think. I repeat, I'm very ignorant about this).

Does this mean that a nuclear bomb meant to be set off in space would require 'fuel' like oxygen or hydrogen to cause an explosion?

 

[Ursa major]

Kinetic energy would be transmitted by anything with mass that has been set in motion by the nuclear event. Once on there way, these anythings will continue on the same vector, and with the same constant velocity, they started with until affected by something else.

Thermal radiation (or any sort of radiation) would be subject to the the same square law disipation as any other radiation (e.g. sunlight): double the distance from the source and the energy over a standard area (say one square metre) would be reduced by a quarter. (The likelihood of being hit by one of the anything mentioned earlier would also be reduced.)

If, however, the anythings or the radiation (or both) are directed/focused, the effect would not dissipate with distance (which is not the case in the atmosphere).

 

[chrispenycate]

No, it would explode just fine. It's just that, since there is nothing to transmit the energy. it's a purely omnidirectional effect that drops off extremely rapidly with distance. The "thermal radiation" (not just infrared, everything from long radio waves to gamma radiation, everything in the electromagnetic spectrum) drops off as the square of the distance, but a space vessel is designed to accept unfiltered sunlight, so it's relatively tolerant to that. The shock wave only contains the matter in the original bomb/missile, so is much attenuated relative to an atmospheric blast (and drops off with distance much faster than inverse square). Ionising radiation? Nothing to ionise until it hits the other vessel (or the one that launched it).

Residual radiation? You can just about ignore it, it's spread so thin (remember, no soil to absorb it, store it.

Which leaves EMP, the magnetic pulse that burns out conductors, instrumentation, anything with electrical conductors in. This is inverse square, too. Space craft will be shielded against it, because of solar flares and Jupiter's magnetic field, but have to have some instrumentation outside the screening to navigate with, so is bound to lose some capacity and need some repairs.

So you have to get your bomb in close to do any good (bad?) and this means the defenders have opportunities to either destroy it, blow it up before it gets that close, or go somewhere else in the time it takes to get to where they were.

Not a very effective weapon mass for mass; a light-speed weapon gives no warning time, a kinetic energy weapon is cheaper, your main drive is probably more powerful, and more directive (unless you're doing an Orion drive, in which case it is nuclear bombs).

 

[poisonoustea]

Thanks Chris, excellent input. That's exactly what I needed to know... and what I hoped to hear. I had the idea that nuclear weapons would be used to bomb planets from orbit rather than space warfare, for the reasons above. I wanted a confirmation before explaining this in my plot.

I still need a lot of brainstorming... galactic wars proved more complicated than they seemed at first, but it's fun to think about implications and strategies.

 

[chrispenycate]

Don't be too quick to use nukes for sterilising a planet, either. Oh, they'll work fine (tried and tested technology) but remember, when undergoing a decent acceleration, your main drive is putting out the energy of an atom bomb every few seconds. Whatever form this energy takes (even my graviotronic drive could do some decent Earthquakes and tidal waves) it could be devastating to a planet-bound culture. Don't even get me going on Galactic scale; that was barely interstellar. Otherwise, you're up there (out there to you, but up to the inhabitants) with this great gravity gradient, all in your favour. Drop things on them (preferably scrap, like asteroid bits and their telecommunications satellites). You'd be surprised how little mass you need at escape velocity to reach the energy of an H bomb. Nukes are not very good mass to energy converters; now, if you could throw a kilo of antimatter at them, now you're destroying.

A well equipped interstellar warship should have a couple of nuclear missiles aboard, just in case, but going back for replacements is a long trip. Always better if you can improvise with materials on hand.

 

[HareBrain]

I had the idea that nuclear weapons would be used to bomb planets from orbit

As Ripley said, it's the only way to be sure

 

[poisonoustea]

now, if you could throw a kilo of antimatter at them, now you're destroying.

Destroying is not exactly the aim; or better, not the final aim of bombing attempts by humanity in my setting. The true purpose would be sterilization, as you pointed out. Human modus operandi in my setting is quite simple: reach the planet, obliterate life forms in different ways (residue radiation from nuclear weapons is excellent), then surround the planet with atmosphere generators and let it stay for a while until it's re-purposed. The true menace of the bombings is that lifeforms actually lose not only a planet, but a usable environment for colonization. Also, humanity has the largest fleet in the galaxy and very selective technology. Aliens have incredibly powerful tech (Sun's ship is powered by that kind of technology), but they are extremely few in numbers, so they have to play smart and intercept the fleets before they bomb their colonies.

It still has to be perfected, but that's my idea. I found out that the whole storyline will be heavily influenced by the mechanics of warfare, so I'm badly in need for advice on this matter.

As Ripley said, it's the only way to be sure

Yes, looks like James Cameron will play a crucial role in the evolution of humanity

 

[dustinzgirl]

Also, don't be hesitant to make your own weapons!

I mean, do we really know what phasers are made from, or why the death star worked, or ask the US Airforce!

U.S. Air Force Plans for Future War in Space