Snipping the wires on a time bomb

It’s a well-worn movie cliche: Heavily perspiring bomb disposal non-expert needs to defuse a tiking time bomb by snipping one of two or three wires, but if he cuts the wrong one, it will detonate.

But one would think that the basic design would have the bomb detonate only when the timer reaches zero and a circuit is closed, and if any wire is cut, the circuit can’t close and the bomb can’t go off. Is the above design somehow superior? Are they deliberately designed to be hard to defuse? Or is it just an invention of Hollywood?

You could wire a relay or transistor open so that cutting a wire would close it and set off the charge.

Cut the blue wire.

One thing I notice is that the explosive is usually just out there in the open with wires leading right to the detonator. Why not just short across the detonator bridge, or (assuming there’s no vibration sensor) just pull the cap out of the explosive and let it detonate harmlessly? (My favorite bomb disarming scene is Goldfinger, where Bond, in the final seconds before the nuclear bomb detonates, fumbles frantically and finally prepares to just pull out a handful of wires only to be pushed aside by a technician who turns off the switch. It amusingly highlights how totally useless Bond is in the entire film.)

The wire-sniping meme is a stupid movie cliche intended to enhance suspence at the cost of vermisilitude. It’s almost as bad as wiring a bomb on a bus so that it arms when the bus goes 50mph…

Stranger

No, you idiot! Cut the red wi…

Stranger

The really bad example of all this was in The Peacemaker. Besides the god-awful casting and direction, the end of the movie has the heroes trying to defuse an atomic bomb. They go through all sorts of difficulties to do so, when all they had to do was clip a few of the wires leading to the explosive charges. A successful nuclear detonation would need a perfectly symmetrical explosion. Rip some wires, and you get nothing but a bang and some plutonium contamination.

It is not all that hard to make bombs that are extremely hard to defuse. Over the years, the IRA got quite good at making bombs that foiled the British Army. It was a cycle: when the Brits figured out how a certain class of devices could be disarmed, the IRA worked around that method, etc.

Even a “one off” bombmaker can sometimes make an essentially undefeatable bomb. The Stateline NV bomber made a device that according to a link on this page still couldn’t be safely defused with 25 years of tech advances.

Note to would-be wire cutters: there might be multiple explosives with a lot more than 2 wires running into each. There may also be detectors attached to wires to look for breaks. There can be all sorts of dummy things, e.g., Something Bad hidden in something harmless looking. Can you really tell if that green block is a capacitor or what?

And that’s assuming you can get the cover off. Hollywood makes things look way too easy.

This thread reminds me of one of my favorite quotes from Roughnecks: The StarShip Troopers Chronicles

if I were building a bomb with accessable wires I wouldnt use colored wires…at least not different colored wires.

fookin hollywood

I also wouldn’t build a bomb with a deafeningly loud “BEEP!” for each second, and would likely forgo the big LED timer as well.

Amusingly, the most likely bomb-defusing scene I can recall was in an episode of Knight Rider, of all things. Bad guy chained up Devlin and some hostage-du-jour and stuck a brick of C4 on the wall with a detonator jammed in it. Michael Knight comes in later, gets yelled at by the hostages, grabs the brick, yanks out the detonator, saves the day. Easy, clean, and none of that “which wire” crap.

“All right, Bud, you have to cut the ground wire, not the lead wire.It’s the blue wire with the white stripe. Not—I repeat–not the black wire with the yellow stripe.” – The Abyss. (Intuitor.com discussion of the detonator system linked.)

Stranger

There was an episode of Stargate SG1 where they set a nuclear bomb, then had to defuse it. For whatever reason, the control panel on the warhead wasn’t working, so they had to open it up, and someone was telling Jack over the radio how to defuse it, and it went something like such:

“OK, now cut the blue wire.”
“They’re all blue wires.”
“What?!”
“All the wires in this bomb are blue!”
“They’re not supposed to all be blue!”
“I’m gonna put in my report that this was a VERY poorly designed bomb!”

Just pour Coke into its innards.

Back into the realm of reality, bomb squads use a shotgun to blast the timers of real bombs; I guess not in all cases and usually using a robot (I don´t think many people would agree to shoot a bomb at point range personally).

When I build my Very Big Bomb, I’m gonna use green and purple wires. There will be an LED counter, but it will be set off by something like 2 and 1/2 minutes, so it detonates while reading “2:33”.

“Roge, grab the cat.”

Years ago, someone showed me a schematic of a collapsing detonator circuit. It was designed to immediately fire the blasting cap if a wire was cut.

Many bomb squads now use a water gun. It hits the device with a high-speed slug of water, disrupting the device before anything can trigger detonation.

Well, yeah, but bad news if you are holding it on your lap at the time. :slight_smile:

Glow worm!

When I was 12 years old I came up with the notion that the way to deal with a bomb might be to pour liquid nitrogen on it (i.e. surround it with a container that you then fill with liquid nitrogen).

Would this work? Has it ever been tried?