How do terrorist bombs work?

Terrorists have a new way of getting bombs into the United States: mailing them. In this episode, Marshall breaks down the science behind the types of bombs used by terrorists, and the explosive ingredients involved.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brainstoff from house stuff works dot com where
smart happens. I am our so brain. With today's question,
how do terrorists bombs work? For example parcel bombs or
truck bombs or suicide bombs. Terrorists have a new way

(00:22):
of getting bombs to the United States. They simply mail them.
For example, recently there were package bombs sent from Yemen
to the United States disguised to look like ordinary packages.
And these bombs could have brought down their respective airplanes
or they could have exploded at their intended destinations. This
is just the latest in a string of terrorist bombing

(00:44):
attempts that goes back for decades. The string includes truck bombs,
suicide bombs, luggage bombs, and parcel bombs. Although they come
in difference shapes and sizes, all these different types of
bombs have the same basic ingredients. They include the explosives themselves,
some way to detonate those explosives, and some kind of disguise.

(01:07):
Let's take a look at how these elements come together
to create different types of terrorist bombs. Timothy mcveigh's truck
bomb is one of the most famous terrorist bombs in history.
It extends a tradition that started with a truck bomb
placed in nineteen twenty in the heart of the New
York Financial District. In that case, the truck was a

(01:27):
horse drawn wagon, but even so more than three dozen
people died and hundreds were injured. There are still marks
on the New York Stock Exchange left by that bomb.
In the case of Timothy mcveigh's truck bomb, the disguise
was the truck itself. The explosive agent was ammonium nitrate
fertilizer mixed with either nitro methane, the type of fuel

(01:51):
that's used in top fuel dragsters and funny cars, or
diesel fuel. The fertilizer fuel mixture was held in large
plastic barrels in back of the truck. When ammonium nitrate
is mixed with fuel like this, it creates an extremely
powerful explosive agent that's approximately equivalent pound for pound to
t NT, but it does need a detonator. It needs

(02:14):
a smaller explosion that's powerful enough to set off the fertilizer.
In this case, McVeigh used two fuses that he lit
to ignite three fifty pounds of an industrial blasting agent.
The shock from that smaller explosion set off the ammonium nitrate.
Mcveigh's truck carried approximately two and a half tons of

(02:35):
that fertilizer fuel mixture, a huge amount that could be
heard fifty miles away when it exploded. It was enough
to destroy an entire office building. Suicide bombs use a
far smaller amount of explosive material, but the effects are
often just as devastating. Despite the small size, a suicide
bomb can explode in the middle of a crowd, making

(02:57):
it extremely lethal. Suicide bombs are therefore the most common
type of terrorist bomb. In the case of a suicide bomb,
the disguise is the bomber's clothing. Therefore, the bomb is
normally fabricated as a vest or a belt that's laced
with explosive charges. The explosive agent itself varies depending on

(03:18):
the location. It could be tnt harvested from other military
munitions like land mines SE four, which is a common
plastic explosive, or acetone peroxide, which is made of common
household chemicals. The detonation starts with a switch pressed by
the bomber himself. That switch could activate a blasting cap,

(03:39):
but an igniter might be as simple as the filament
of a light bulb. The switch in the bomber's hand
connects a battery to the bulb. The filament heats up
quite hot in a fraction of a second and sets
off the bomb. In the case of the two parcel
bombs sent from Yemen, the use of a toner cartridge
as a disguise is particularly interesting. The reason is because

(04:01):
toner cartridges are a very common cargo. If you have
a laser printer at home, you know that the box
for the new cartridge doubles as a mailer, so you
can return the old cartridge to recycle it. Therefore, there
are thousands of toner cartridges flowing through the parcels system
on any given day. It would be nearly impossible to
screen all of them for bombs. The use of household

(04:23):
chemicals to create the explosive agent would also be beneficial
here because it would throw off dogs used to detect explosives.
In the case of this particular bomb, p e t
N appears to be the explosive. P e t N
is most commonly found in something like debt chord, a
debtonation cord used to set off explosives. The debtonator is

(04:46):
often a modified cell phone. This allows the bomb to
be remotely activated at any time, simply by making a
call to the phone. Another common detonator is an ordinary
battery operated alarm clock. Had either of the bomb exploded
in the air, the airplanes would likely have been blown
out of the sky. Recovery from the Atlantic Ocean would

(05:06):
have been unlikely, so we might never have known exactly
what really happened to the planes. The reason why a
small bomb can take down an entire gigantic passenger jet
is because the cabin is pressurized. Once the bomb punches
a hole through the side of the plane, the pressure
of the cabin rips off a large portion of the fuselage,

(05:27):
and then the plane is doomed. For more on this
and thousands of other topics, is it how staff works
dot com