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The Chelsea bombing and the pressure cooker bomb

pressure cooker bomb chelseaThe incident in Chelsea, New York this weekend where a pressure cooker bomb went off, injuring 29 people and causing thousands of dollars worth of property damage, caught the attention of the world. Most people don’t expect something like that to happen and much less in a city neighborhood like Chelsea, and so close to the anniversary of September 11th.

We’ll have to wait until the investigation runs its course to know exactly what happened and who might have been responsible but one of the details that people are talking a lot about regarding this incident is the type of bomb used: a pressure cooker bomb. Something that takes an ordinary everyday pot, that everyone has at home, and turns it into a deadly explosive device seemingly without much effort. How does something like that happen?


A pressure cooker bomb: not a new threat by any means

Most people who know the history of these kinds of devices will probably remember the pipe bomb as the ancestor to the modern pressure cooker bomb.The pipe bomb is exactly what it sounds like: A metal pipe which is filled with explosive and sometimes additional shrapnel like nails and screws to create even more damage. Pipe bombs have been around since the 1800s and different militaries around the world have been training people on these devices for decades. Any soldier in the modern era probably knows and has experience with pipe bombs.

pressure cooker bomb chelsea
Boston Marathon bomb remains. Wikipedia.

So it’s not surprising that someone would eventually think about building a pipe bomb with a pressure cooker, hence giving genesis to the modern pressure cooker bomb. We started the see pressure cooker bombs after the year 2000, Mainly in the Middle East as improvised explosive devices . From there pressure cooker bombs found their way into Europe, and eventually they made their way into the United States. Over a decade after their initial appearance in the Middle East, pressure cooker bombs were first used in the United States during the Boston Marathon bombing of 2013.

Any one of these devices, a pipe bomb, a pressure cooker bomb, is an improvised explosive device (IED), which is one of those technical terms used by government agencies, that the media loves for describing all these bombs. IEDs are homemade bombs that use very simple supplies, available mostly anywhere, and that usually explode without any real control… apart from the detonator. IEDs normally have no mechanism to direct the blast or fail-safe mechanism to protect the operator, and work on low-yield explosives, which sets them apart from regular explosive devices.

Pressure cooker bombs are also related to propane gas bombs, which are another type of improvised explosive device (IED) that’s commonly seen in war scenarios.Propane gas bombs simply take a cylinder of propane similar to the one you have on your grill at home, and put a detonator on it, which makes it explode on command.Propane gas bombs have been more common than pipe bombs in South America during the past few decades (mainly in Colombia), because a cylinder of propane gas is a very common staple in these regions. Much more common than the explosive substances needed to build a pipe bomb. Someone looking to make a bomb is going to get a lot less attention if they’re buying propane cylinders at the supermarket than if they’re buying, say, the materials to make ANFO or a similar explosive.


How to make a pressure cooker bomb?

pressure cooker bomb chelsea
A pressure cooker bomb in the real world (Youtube)

Of course we’re not going to give anyone detailed instructions on how to make a pressure cooker bomb at home and possibly blow themselves up in the process. In fact don’t ever try to build a pressure cooker bomb, a pipe bomb or any other type of IED. This is not something you play with or experiment with: an IED will do a whole lot of damage and can kill you, and there’s a lot of places that you can mess up along the way, and accidentally set it off.

So, no. Do not try to build these things under any circumstance. I don’t care if it’s the end of the world and the zombies are at the gate coming for you: do not try to build this thing.

For the technically curious who are wondering how to make a pressure cooker bomb, here’s a simple explanation.

Any kind of bomb or explosive device is essentially a container that lets pressure build-up on the inside. That happens until the pressure reaches a critical point, in which the container ruptures. When the container blows, the built up pressure lets loose and a shock wave is released. The type of shock wave and the force it carries is going to depend a lot on how fast the pressure build-up was, and the way in which the container ruptured.

That’s true for any explosive device: improvised or not. A grenade, a pipe bomb, a pressure cooker bomb, any of those are going to work on the same principle. Build up pressure, break the container, release a shockwave.

A pressure cooker bomb is an ordinary pressure cooker, filled with explosive. The pressure cooker is sealed so gases can’t escape, and a detonator is placed on the inside. The detonator is usually some form of blasting cap, electrically operated.

pressure cooker bomb chelsea
Energy for detonation is provided by batteries

Once everything is sealed up, the cap is hooked up to an electric current source, that sets it off. There’s many ways that people use to get electric current to the cap, and that’s where you see a lot of creativity come into play. In Chelsea it seems they used cell phones, which is a modern way of doing it: the cell phone is connected to an electronic switch, and when it rings, the switch closes and a battery sends energy to the cap.

Using a cell phone does have a very singular disadvantage: tracking. And let’s hope that disadvantage came into play in Chelsea and will give police a way to figure out who was responsible. Any time you’re using a cell phone, your position is known to the phone company. As soon as you turned on the phone, you showed up on their records. Even if you turned it on with another SIM card, your phone’s serial (known as an IMEI) shows up and registers… and it doesn’t change with your SIM card.
If the attackers in Chelsea were dumb enough, their entire trip is registered somewhere in the data banks of a cell carrier in New York. And those records probably even contain the location of their homes, the location they purchased the phone, and where they assembled the bomb.

But then again, the attackers could have just used the phone as a timer the whole way, with no SIM installed. That would make finding out the minute-by-minute details much harder. Although if you manage to turn up the phone or any of its critical memory circuits, you could potentially have an IMEI, and cross reference with records to see what you get.

So there you have it. That’s how a pressure cooker bomb is normally built. Pressure cooker, fill it with explosive, blasting cap, and electricity. When the cap goes off, the pressure builds up in an instant inside, and when it goes critical, the cooker explodes and lets the shockwave loose. The whole explosion takes only a fraction of a second, unlike when a pressure cooker explodes at home, where it’s usually been building up pressure for several minutes.

If you want to see what something like that looks like in the real world, you can find videos on Youtube that show pressure cooker bomb explosions in Afghanistan and Iraq.

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