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What kind of damage could a bomb that cause everything within a 20 meter radius to just vanish have within the Earth atmosphere? I would imagine that it would create an implosion and inflict immediate structural damage to any building nearby. But how comparable would that be to regular explosoves?

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  • $\begingroup$ What is your aim with the bomb? I mean, it has a ton of implications. You could get access through walls, floors or other less than 7 to 9m thick. You could collapse a building with ease by removing a carrying concrete pillar, without further construction equipment required. You could get a ton of them in the atmosphere and try to do something with ozone, or create weird depressurized zones or the like for crazy effects. It is so wide it's hard to know where to start. $\endgroup$
    – Trioxidane
    Jun 14, 2021 at 16:00
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    $\begingroup$ @Trioxidane why would a 20-meter radius spherical holemaker only give access to "You could get access through walls, floors or other less than 7 to 9m thick"? $\endgroup$
    – PcMan
    Jun 15, 2021 at 9:48
  • $\begingroup$ @PcMan we all make mistakes $\endgroup$
    – Trioxidane
    Jun 15, 2021 at 10:03
  • $\begingroup$ I assume you're looking for an IMPLOSION rather than an EXPLOSION. An explosion of such scale would instantly disintegrate everything within 20m of the point of impact would cause massive damage all over the place, not just the area you're trying to affect. $\endgroup$ Jun 15, 2021 at 14:28

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Much of the damage of a conventional explosion is due to the "N wave" -- the sudden application and immediate reversal of a strong overpressure. The first, compression wave stresses materials, then the reversals stresses them again in the opposite direction, before the material has a chance to "heal" (stress cracks can weld themselves under some conditions).

Your deletion device gives kind of the opposite effect -- the negative pressure, followed by a smaller positive wave as the air compressed by its inertia when it reaches the center of the void re-expands. This ought to produce much the same effect, except for structures specifically designed to withstand pressure from inside or outside. A submarine hull, for instance, is built to handle external pressure (and is vulnerable to external explosions only because it's already stressed, often near its limits, when so attacked). An above ground petroleum storage tank, on the other hand, is made to stand pressure from the weight of the liquid inside.

In the end, there will be an equivalent explosive power for any given size of deletion sphere -- and the resulting damage will be very similar to the overpressure damage from that amount of, say, TNT. What the deletion sphere lacks compared to, say, an artillery shell, grenade, or air dropped bomb, is fragmentation on top of the pressure effects. It doesn't throw pieces of its own shell at rifle bullet velocities in all directions.

As noted in comments, however, the implosion pressure waves aren't where the real effect of this kind of "deletion bomb" lies -- that's in its ability to leave a spherical void (presumably in anything). It's like a camouflet ground penetrating bomb without the need for a heavy bomber to deliver it. It's instantaneous demolition ("Tear down a house? We'll just delete it! Make double sure you've got everything out you might want again..."). It's mining without huge tailings (but then again, without being able to return the tailings to the pit). It's antiaircraft artillery, anti-ship and anti-submarine, airfield denial, and so on.

Fortunately, it also violates a major conservation law...

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  • $\begingroup$ An explosion creates much more than just 1atm overpressure. I don't think the pressure wave of the deletion bomb implosion would be all that impressive. $\endgroup$
    – ths
    Jun 15, 2021 at 14:48
  • $\begingroup$ @ths Exactly -- there's no large positive wave, but there's the underpressure wave that usually follows (perhaps a little stronger than would be the case with conventional explosives, because nothing at the center or near it) and then the oscillation following that. That wave can't exceed 1 atm, but for conventional explosives, overpessure much beyond 1 atm is quite limited in reach, too -- tens of meters for a half-tonne gravity bomb. $\endgroup$
    – Zeiss Ikon
    Jun 15, 2021 at 14:54
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The main effect is of course the deletion of the 33510 cubic meters of material around the bomb. That is one ALMIGHTY big hole, comparable to the direct damage from a medium-to-large tactical nuke. For scale, it is a hole big enough that if you detonated it on the space needle tower in Seattle, it would not only topple the tower, but completely remove the bottom half of the tower!

The formation of the hole is nonviolent, but the filling of the vacuum will very much be violent. It would have been devastating to anything inside, but... nothing inside, of course. You would just get a thunderclap like lightning, just several times louder. Followed by a rebound explosion of mediocre strength, equivalent to no more than a few hundred kg of tnt.

The biggest damage, by far is the actual deletion effect. It will undercut any building, smash any vehicle even to the size of an aircraft carrier, and do very interesting things if detonated on the surface or underground. The "vacuum" effect is a mere sidenote.

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I think the closest analogue you will find in comparison to existing weapons is a thermobaric weapon, also known as a vacuum bomb: https://en.m.wikipedia.org/wiki/Thermobaric_weapon

The weapon works by combining fuel with atmosphere and then igniting it, burning the fuel with atmospheric oxygen. The resultant blast consists of two stages - an explosion stage as the fuel and oxygen are consumed releasing energy, and an implosion stage as the surrounding atmosphere collapses into the resultant vacuum. The weapon has two main advantages over conventional weapons:

1 - As it uses atmospheric oxygen rather than an oxidiser it need only carry fuel, meaning that more energy can be released vs a same sized conventional weapon which would need to carry both fuel and oxidiser.

2 - The vacuum effect is significantly more harmful to personnel especially when used against targets where there is confined atmosphere ie bunkers, caves, tunnels, etc.

The deletion bomb used in regular atmosphere would probably create a similar effect to the vacuum stage, but without the initial explosion. It would cause less damage than a vacuum bomb of similar size as it would not generate an initial explosive force.

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    $\begingroup$ People may also know this type of explosive as "FAE" -- Fuel Air Explosion. It can occur with flammable powders (grain dust or coal dust, for instance) as well as liquid or gaseous fuels. Militarily, it creates the largest, most powerful non-nuclear aircraft-delivered explosions to date. $\endgroup$
    – Zeiss Ikon
    Jun 15, 2021 at 11:16
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The implosion will be loud, but that is about it.

Air will begin flowing to fill the vacuum at the speed of sound ~767mph which will exert a force of about 13lb/sqin on anything directly outside of the deletion area. For a person sanding just outside of the deletion zone, that is about 1000 pounds of force per second ... now this sounds like a lot except that it will be in a very short period of time spread across your whole body. Since it is so spread out across your body I will say it's not going to do much direct damage since it is about the same pressure you experience from diving about 3 feet underwater, but what about how much it drags you? At this speed the implosion will reach the middle of the vacuum in about 0.026 seconds, and over that time period the force pulling at you will fall off. I'm not entirely sure what curve of fall off it will follow; so, for simplicity sake, let's pretend you will get this maximum force for the whole period of time, and just know that what I am about to say is a significant overestimation of how hard it will pull you (not that it will matter much).

With this force over such a small period of time, that make your total acceleration on a 160lb person about 0.1625 miles per hour. In other words, the implosion would not even be forceful enough to make someone standing right at the edge lose thier balance.

What about the rebound wave?

The implosion will be much less significant than the explosive force of a comparatively destructive bomb. This is because the pressure gradient from inside the deletion and outside the deletion is only ~1bar. In contrast, the pressure gradient of most high explosives ~10,000-140,000bar.

To get a rough approximation of how much potential energy we are talking about, consider the area of your sphere is ~5026.55m^2, so the total potential energy of your implosion will be about the same as a military grade warhead that is ~10cm in diameter. This means it will be loud like a small bomb going off, but since the deletion ensured that there is nothing within 20m to even hit with said shockwave, it's not going to really do anything meaningful beyond what the deletion did.

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  • $\begingroup$ It will be a loud thunderclap. $\endgroup$
    – Willk
    Jun 16, 2021 at 1:26

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