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Comment by lhoff | Hacker News Reader

I read somewhere that the way the harbour and the storage buildings where structured(probably not intentionally) directed a big part oft the blast downwards, hence the crater. Matches the Videos i've seen were the explosion was sharply going into the sky. Only the shockwave was horizontal.

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Purely from a physics/explosives effectiveness standpoint, the destruction would have been much greater if it had occurred at 200-300m above ground level. This is one of the reasons why air drop freefall nuclear bombs (10-20 kiloton class) were designed with radar fuses to explode at a certain height above the target, and not at ground level. Except when intended to destroy a bunker.

Because the explosion occurred at ground level at least some of its energy was directed into excavating a crater and not destructive shockwave traveling outwards.

Also, IIRC air burst nuclear weapons produce less fallout.

For nuclear war planners, fallout is probably a feature.

Not for theoretical defensive tactical use in Korea / Germany / Israel / similar

Two kinds of nuke classes:

1. Strategic -- The world is going to die nukes. These are big nukes on ICBMs. If the opponent launches a strategic nuke, you launch all of yours and kill them too.

2. Tactical -- Small nukes that you shoot at the opponent's army before sending in your troops.

You're thinking of strategic nukes. But strategic nukes are far weaker if you have a dirty explosion: its probably better to have a more complete bomb. Tactical nukes absolutely must be clean, because your own troops are in the area.

Strategic nukes are typically fission-fusion-fission devices with both more yield and more fallout than a cleaner fission-fusion design of the same weight.

One can think of an explosion causing a roughly spherical shockwave. For a ground level explosion there's a relatively narrow "band" of that shockwave that travels along the surface of the earth damaging buildings and other stuff, the rest is either directed upwards, or as you say, to create a crater (and a lot of the "cratering energy" will be reflected upwards towards the sky as well).

A ground level explosion also means that nearby buildings and geography (hills etc.) shield things behind them, reducing the destructive effect.

With an airburst you have a more even distribution of destructive energy over a larger area.

One of the videos, when you step it frame by frame, manages to capture a nearly spherical fireball [1]. The next frame seems to suggest (to my amateur eyes) that the tall grain silos is causing a bit of a reflection of the fireball. Other than the grain silos, though, there doesn't seem to be any other factors shaping the blast.

[1] https://www.reddit.com/r/nextfuckinglevel/comments/i420ir/th...

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