No, I do NOT need an answer fast. I don’t even need all the details, just trying to understand this Fox News story
It was probably in a metal pressure cooker, which usually isn’t electric, but instead has to be placed on a stove to heat. I don’t think the pressure cooker was anything but a container, and the timer was a seperate mechanism. A pressure cooker makes a good bomb container because it has a locking lid on it. It’s essentially a wide diameter pipe bomb.
Oddly enough, I have a little experience with pressure cooker bombs: on one of my projects in Afghanistan, we had provided pressure cookers as part of start up household goods. Some of these pressure cookers were used to make IEDs. We were contacted by the US military and asked to stop providing pressure cookers.
According to this story, it sounds like the pressure cookers were just used to contain the initial explosion, so it would be more violent (pressure builds up until the pressure cooker explodes); the pressure cooker itself isn’t powered up and a remote controlled or timer detonator is used:
That said, the first thing I thought of when I read “pressure cooker bomb” was this xkcd what-if.
As Tripolar said, they make excellent chambers for bombs. I don’t know much about IEDs other than I’ve been around a lot of them. I’m kind of amazed the number of people killed was so low. It had the potential to be much, much worse.
IANABE (bomb expert), but the amount of orange/flame makes me think it was made from some kind of deflagration in the pot, not a high explosive like C4.
The grim thought that always occurs to me in situations like this is, as horrible as it was with two bombs going off, and maybe a couple more duds, why weren’t there a lot more bombs? Are they just inherently unstable so making, like, 20 of them would be a really bad idea, odds-wise?
IANABE either, but I would imagine that if it’s just one dude, planting a bomb without getting caught becomes an order of magnitude more difficult for each bomb you plant. People get suspicious seeing someone dropping a dozen duffle bags around town.
I got side-tracked by a link within Michael63129’s link to a chemical called dioxygen difluoride (AKA “FOOF”). Really horrible stuff, but unlikely to be used in a terrorist attack as the terrorist would most likely poison or blow himself up making it.
As mentioned it is really just a big pipe bomb. An explosion is an increase in volume and a release of energy. Containing the explosion in a vessel which allows for the pressure to build up prior to containment failure increases the force. Place a firecracker on your palm and light it. Its gonna hurt like a sonofabitch but you probably won’t be injured too bad. Close your fist tight around that same firecracker and you’ll lose part of that hand. The containment is especially important when you are using low explosives such as black powder which is a slower reaction.
I’m guessing but I think there are a few factors contributing to this.
Low explosives. In the parts of the world in which we both have seen IEDs it is a lot easier to come by high explosives such as Semtex. Most likely low explosives were used here which will still cause a decent sized explosion but a huge one. I would bet that most were not injured by the force of the actual explosion but by the shrapnel. The most badly injured were probably right on top of it.
The IEDs are reported to have been placed in garbage cans. Depending on what kind of can they were it could have deflected some of the blast.
It happened at the 4 hour mark. The big crowds there to see the winners had left. There were still a lot of people around but two hours earlier it would have been much worse. Its possible that the bomber couldn’t get that close earlier.
I didn’t see the primary source, but I have heard it reported that gunpowder was used as the explosive.
If it was modern smokeless gunpowder, it doesn’t explode at all if it isn’t contained. The fast burning, fine grained stuff as used in pistols and shotguns will burn in a second or possibly a little less. The coarse stuff used in rifles will take several, or even tens of seconds to burn. You get a vigorous fire, but not even a pop, much less a bang.
These powders display what is known as progressive burning though, where they burn faster under high heat and pressure, as found in the chamber of a firearm. So by containing them the pressure builds, and they can then burn fast enough to make a mild explosion (mild compared to things like simtex, TNT or ANFO). Still they burn at perhaps 1/100 the rate, at best, of a real explosive.
A pressure cooker is designed to operate at a few 10’s of PSI. Guns operate at 10,000 psi and up. Even with a large safety factor designed in, a pressure cooker is going to rupture at a few hundred psi at best.
It is possible they used old fashioned black powder, which is still available for muzzle loading firearms. That will burn pretty quick even at modest pressure, but the available energy is much less than modern powders.
Given the damage, I think it likely that these must have been fairly optimal given what they were.
That’s another feature – the vent valve provides a ready-made point for inserting fuse/detonator with minimal additional drilling or soldering.
Given an electric pressure cooker with a built-in timer, the timer mechanism - not the actual pressure cooker part - would be outside the pressure vessel so it could be opened up to rig it in with the proper detonation wiring.
FWIW, they’ve shown pictures of the pressure cooker parts now, and the “UL listed” marking and most of the word “electric” are visible.
As a teenager an older cousin of mine tried to make paper out of woodchips by using his mother’s pressure cooker in her basement. The story of the explosion and mess are still retold at family reunions more than 50 years later.
These days, I’d be afraid to Google bomb making or any similar subject for fear of a subsequent visit by humorless men in dark gray suits.
In Paris in the 90s, garbage cans aggravated the damages by projecting pieces of metal and hardened plastic like as much sharpnel.
I’m not sure that was the case. Initial reports did say that, but now they seem to be saying they were just in bags on the ground. Certainly when looking on Google Street View I can’t see any permanent rubbish bins at the spots where the bombs went off, and there don’t seem to be any there in the photos of the scenes either.
The second bomb seems to have gone off right about here, between the tree and the mailbox (see photos here, although it seems clear to me that the bag they circle couldn’t have been the bomb because the barricades were blown towards where it sat. Is that black thing definitely a mailbox? I thought they were blue?
Here in London, rubbish bins have mostly been removed from the city anyway for fear of being used as handy bomb receptacles. When there are big crowds around, they usually just provide big clear plastic sacks on stands to put rubbish in.
Thats why I used the word “could”.
It’s an olive-drab relay box.