Why do nuclear bombs explode mid air?

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I’ve always wondered why only nuclear bombs detonate before hitting the ground and not the actual moment of impact. Does it affect the amount of damage? or does it reduce nuclear waste and radiation?

In: Physics

17 Answers

Anonymous 0 Comments

The ground is famously lumpy. If the bomb waits until it actually hits the ground then things nearby that you want to blow up are likely to have significant amounts of ground in between them and the bomb, which will reduce its destructive potential. When it is higher in the air it has a better line of sight to most things, meaning when it explodes there is less in the way of the destructive force.

Anonymous 0 Comments

It differs by purpose of the nuclear explosion. An airburst (explosion above the surface) maximizes the affected area, because a smaller share of the energy will be stopped by soil and structures to the sides. You basically make the energy of the explosion rain down on the area instead of letting most of it be used to move large amounts of soil. 

But if the target is a single high value or tough to crack target like a bunker then a direct hit is the preffered strategy 

By the way the same is true for larger conventional bombs and missiles. Against dispersed soft targets like a collection of soldiers you’ll usually let it explode above them to spread the effect out

Anonymous 0 Comments

The ground fucks up the detonation mechanism, and exploding in the air provides a larger radius

Anonymous 0 Comments

The blast is a sphere. If you detonate it on the ground, then the blast is absorbed by the ground, any buildings or hills in the way, etc. If you detonate it in the air, the entire sphere expands toward the ground from above and you get maximum damage.

And yes, typically there is less radioactive fallout from an airburst than a groundburst.

Anonymous 0 Comments

Another factor to include alongside the other answers.

A ground-burst means energy is absorbed into the earth, causing a massive crater and destroying everything in line-of-sight, but as mentioned this is limited in range by obstructions. Also that force that pulverises the ground to dust is probably just wasted force (unless you conveniently land it on a shallow-dug, high-priority target) that the Earth easily and readily absorbs. Plus you then kick all that irradiated dust into the air and cause problems from there.

An airburst means the blastwave is not only faced with less obstructions giving it a bigger range, that blastwave will not bury into the earth but instead bounce back off it – giving it greater destructive potential. The blastwave travels much, much further so will give a larger area of destruction (all due to the pressure differences/overpressure), as will the thermal energy from the blast causing more burns at greater distances – again, due to a less obstructed line-of-site.

In short, groundbursts are for pulverising a specific target into oblivion, while an airburst maximises damage and casualties for a wider area.

Anonymous 0 Comments

Well, technically you detonate a nuke anywhere you want, it’s not like someone can force you otherwise, *you have a fucking nuke* after all.

But where you detonate them does affect the results a good deal so it depends on what you’re trying to accomplish. If you’re taking out a bunker you’d want your nuke to burrow into the ground for example, if you’re trying to disable communications or vehicles you’d detonate it high up in the atmosphere for an EMP effect.

But the issue with a ground based nuke is partially fall out but also because the ground just reflects the nuke up and away from your target. That’s a tremendous waste of a nuke. So a ground attack would be more something like a dirty bomb or terrorist attack, deliberately inflicting terror and fall out without really trying to strategically eliminate a target.

Detonating a nuke in the air reduces fallout because it doesn’t throw up as much dust and debris (which rains back down somewhere and is what “falls out” during fallout”) but also because it’s sends the energy *down* to the ground. When that energy hits the ground it’s like slapping a fly against a wall, all that energy *crushes* the target *into* the ground.

You also get a wider radius on your effect and do more damage to a larger target.

Anonymous 0 Comments

Maybe a bit above five, but…

There are four main effects from a nuclear weapon:

* Fireball: Everything within is vaporized
* Blast: Everything within a certain range is flattened
* Thermal radiation: Everything within a certain range is burned
* Ionizing radiation: Everything within a certain range is irradiated

So we now have to decide what effect we want from the weapon. The fireball is relatively small, and we don’t necessarily need things vaporized, so we don’t need a ground burst. Probably the only exception would be a hardened target like a bunker or missile silo.

With the exception of the short-lived neutron bomb, we aren’t really relying on radiation either.

We do want the blast and thermal radiation to do more damage at longer distances though to destroy cities and/or kill troops. A ground burst attenuates these effects because half of these effects of the weapon go straight into the ground. An air burst allows these effects to spread much farther away from the blast. Also, a ground burst produces more radioactive fallout, and that can drift uncontrollably over days, not a good thing if your forces are anywhere near the blast.

Anonymous 0 Comments

Just imagine that the ‘useful’ (ick) explosion is a circle around the bomb at the moment of detonation. Any part of the circle that overlaps with the ground is useless. So you explode it more or less when the horizontal diameter of that circle is at ground level and you hit the most things

Anonymous 0 Comments

The air is very good at transferring energy, and the ground is great at absorbing it. The blastwave of heat and wind will travel much farther and do a lot more damage if it starts high in the air.

Anonymous 0 Comments

I’m studying medical imagery so I have a good basis or radiation knowledge but I’m still only 1 semester in so take it with some salt ..
so for the two nuclear bombs that were used against people the goal was maximum immediate destruction. The reason to detonate in the air is partly for more destruction as others pointed out but also because it gives more potential that the radioactive material is used as fuel for the explosion. The goal is not radioactive fallout. If an atom bomb would explode in the ground more of the radioactive material would be absorbed into the ground and slowly disintegrate, causing long term radiation (depending on the type of radioactive material, it’s half-life, disintegration processes and thus type of radiation etc.)
Atom bombs basically are “interesting” to use because for much smaller mass of fuel you can get a lot more energy to use as destructive power due to the radioactive chain reaction of the bomb, not because it’s radioactive specifically.