Bomb Dismantlement in My City — How Loud Can It Be?

Hi everyone,

A 250 kg bomb from WWII has been discovered by a ship and brought to the port of my city. It will be dismantled on Sunday and the authorities have asked the inhabitants of my city to stay home on that day (with the windows open to avoid being injured by glass shattering in the case the bomb would explode).

The bomb apparently contains 145 kg of explosives. How loud could it be if the worst happens? My house is approximately at 1.2 km of the dismantlement location. I am wondering if I should spend the whole day far from my city... what do you think?

If you're curious, details and pictures here: https://www.lasemainedansleboulonna...-mesures-qui-paralyseront-trois-communes-le-6

 

If you can avoid being home until the all clear is given then I would make the most of the time away.

 

Article about one of those bombs exploding in my lovely country.
https://www.express.co.uk/news/uk/8...s-video-Aston-Villa-Park-stadium-British-Army

I say, better keep it safe and leave your town for some time. I can imagine, that the sound of such an exploding bomb, could be something similar to the one of a thunder strike, and honestly, 1km distance is nothing for a thunder strike sound.

 

On the side note, though. I have made an approximation that the bomb in your town, could have about 100-200 kg high explosive materials in it. This is similar to 100-200 kg of TNT, that is found in dynamites. The conclusion? The bomb in your town, probably has a power of at least 140 Kilowats per hour, and it's equal to about 400 megajoules.

One megajoule (MJ) is equal to one million (106) joules, or approximately the kinetic energy of a one megagram (tonne) vehicle moving at 161 km/h.

But, the bomb is 400 Megajoules. So, if the bomb in your town exploded, it could easily have the kinetic energy of 400 passenger cars going at the speed of 100 miles per hour. But, if we assume that the bomb has more than 200 kg of high explosives, then it would have a similar kinetic force to 1000 cars going at the speed of about 100 mph. That's a lot of force and a lot of noise.

Believe it or not, but the energy that this bomb would create, is only estimated at about the electricity worth bill of $15 US.

Tesla S model cars consume only 0.3 kWh, per driven mile, so I guess my approximations aren't all that unrealistic. And, obviously we are talking about a car that is quite heavy and is moving and big speeds.

 

Hi Julien,

If I were you and able to leave, I would do so.

I live in Berlin, Germany, and we also have a lot of bombs form World War II.
Sometimes they are just found because of construction work.

Then we are also told that they are going to dismantle it, and to stay away from certain areas,
and so on.
Since I live here, never one of these bombs exploded, but of course I always wished to leave.
The thing was always, that I could not leave, mainly because I had to stay at work.

So I would say, if you can leave, do so.
One of these explosions must be so loud.

 

Damn, that sounds scary!

And if they advise people to have their windows open because they fear the glass might shatter from explosion, then that must mean the sound an explosion would make it SERIOUSLY LOUD.

To be frank: I would get the hell out of there, if I were you.

 

Bombs are loud.

 

I think it's highly unlikely the bomb will explode, they'll surely send in the very best UXB experts from the police department to dismantle it.

 

Thank you all for your input.

Thank you Pawel for the explanation about the kinetic energy. I have no idea how much that would translate in noise volume. Apparently if the explosion reaches 160 dB (realistic?), the noise at my level (1.2 km of distance) would "only" reach 98 dB (which would probably be fine if I wear earplugs).

Not sure what I will do. I guess I'll just take my car and chill in some places of my area on that day, away from my city.

 

You must go out of the city if you don't want to risk your hearing. I'm not saying you will go deaf or end up with a louder T but anyway it is rational to go out of the city. You said it's on sunday so why don't you just go somewhere safe?

 

I would not worry about it, personally, especially if you stay indoors: you are far enough for the sound wave to be fairly attenuated, and the noise pattern of an explosion is a spike (short duration).

 

With plugs you'd probably be fine. That being said, better safe than sorry?