An EKG-Bomb

Factual Questions
1

Came upon an interesting bit of mad science in this article.

Reminds me of the Professor from Conrad’s Secret Agent, who kept a flask of explosives which would detonate should he release his grip on a rubber ball.

In this article the concept of the dead man’s switch is updated to include a sort of EKG-trigger for however much HE-plastique you can comfortably conceal on your person. You die=you go boom. But it doesn’t really say how it’s put together.

As far as I know discussing bombmaking on the web is still legal, so in the interest of Science, any a’you clever Dopers want to take a crack at this? How would you rig it?

2

There are automatic defibrillators that analyze heart rhythm and apply a shock as needed in order to restore normal heart rhythm. There are automatic external defibrillators, designed for use by civilians with limited medical training; these are the kind that are becoming more commonly seen in public places. There are also implantable automatic internal defibrillators, which are surgically implanted in the bodies of people who are at high risk for spontaneous cardiac arrhythmia.

It seems to me that it would be trivially easy to surgically implant an AID that has been modified to emit a detonation signal if it detects no pulse for a period of X seconds (where X is a sufficient length of time to assure that you really are dead). Safe deactivation would require physical live-capture of the supervillain fitted with this system, followed by surgical removal. Of course the SV could have booby traps in place, for example an EEG tap or blood chemistry monitor that watches for signs of anesthesia (for which one end run would simply be vivisection).

3

If the explosives are external then defusing is a simple (!) matter of disconnecting the explosives from the electronics.

If the whole installation is internal, defusing is done in a large open area from a distance by a sniper.

4

What is the probability that the first such super-villain would be Snake Plissken?

5

Might removing the electrode result in a flatline reading, thereby kablooie?

6

I’ve heard of him–I heard he was dead.

7

Separate the pacemaker output from the explosives. Even if the pacemaker decides to fire the pacing current, nothing happens except a charge flows down a now-disconnected wire leading to nowhere.

I agree that if you disconnected the pacemaker *input *from the guys heart it’d believe he wasn’t beating anymore and fire the pacing current output. Which output is still connected to the explosive and you’d get a noisy, gloppy mess. Don’t do that.

8

Yet another thing Hollywood overcomplicates to the point of being just plain wrong: You don’t cut the blue wire or the red wire. You cut any wire that connects the battery to the detonator. Once that’s done, it’s not blowing up.

9

Of course there’s always the risk of the big obvious decoy 9V which when disconnected triggers the actual circuit fired by a well-hidden coin battery.

When I build a bomb, the big prominent countdown timer will be included. But when it hits 2:49 to go: KABOOM. That will ensure James Bond becomes James Was-Bombed. He never gets started on the disarming, nor does the girl start looking real nervous & start fingering her top until the countdown gets to about 3 minutes.

Always remember, the people who build bombs are already not playing fair. Don’t expect IEEE standards-compliant construction.

10

Yes.

Bomb-making 101 … without attracting too much attention, all this is public knowledge thanks to Hollywood myth. I’m not an expert, so this is generalities…

Plastic explosives, or fertilizer and diesel fuel, etc. - explosives are harmless. You can jump on them hammer them, drop them 100 feet down a shaft (happened at a mine near where I worked) and NOTHING happens. These need a blasting cap to go off. The force of a real explosion causes these explosives to also explode, and it’s hard to recreate the force of an explosion without a blasting cap.

In your typical al-Qeda-in-Hollywood scenario, they use blasting caps because logically, they are easily(?) commercially available. (The mine I mentioned had boxes and boxes of them - I assume these days inventory is very tightly controlled). There’s no great value in home-making something that is already commercially available. Blasting caps look like a tiny version of a bullet with wires coming out instead of a pointy end, but about as thick as a pencil and maybe two inches long.

There are burning fuse versions, but since the purpose of a fuse is to burn slow and give you time to run away, most convenient is electrically detonated. Of course, as everyone who watches movies knows, burning fuses can be cut. (But IIRC, can’t be pinched out, since commercial fuses are designed to function even when buried or wet… and they are pretty thick, unlike the old firecracker fuses. Electric caps, OTOH, just need a trigger current.

There are unstable explosives - nitroglycerin is the most Hollywood one. There ones you can make at home. (MY father told me of making stuff in high school. Mix it up, pour onto the raidiators before class. As the water evaporates, it becomes crystalized and volatile, and in the middle of class it would suddenly go BANG! like a firecracker.) One is apparently made with mixing hydrogen peroxide. This is why the TSA bans water, it’s easier than making every agent a chemist to inspect every liquid. They are afraid someone would mix up the explosives in the airplane toilet. (At least they didn’t ban the use of toilets through the entire flight)

Home-made gunpowder, apparently, does not give enough bang for the buck. Literally.

the obvious flaw with unstable explosives is - they are unstable. How do you deliver a quart of something that might go off if you hit a pothole or drop it on the way to the target?

Dynamite I think is something in between, nitro in sawdust (Nobel’s big invention?) so it was stable enough to handle and did not need a detonator, but if left alone for too many years would leak volatile pure nitro to make for interesting Hollywood scripts. For this reason, it is less common

So your typical bomb is a wad of safe-ish plastic explosive (like clay, easily molded to fit wherever) and a blasting cap or several in it, and some mechanism to set things off, like an electronic alarm clock built by a precocious Muslim high school student. (Hint - sarcasm…) A common trick too is to wire the trigger to a cell phone ringer, so the bomb can be detonated on command, or by a telemarketer.

The typical Hollywood vest has a whole bunch of wires because it’s several individual pockets of plastique, each with it’s own blasting cap.

Then you get into the mind games. The obvious question is - OK, how to disarm? Pull the blasting caps out of the C40 and after that if they go off, you’ll only lose an eye or some fingers. disconnect the battery, and no trigger current to the caps. Cut the wires to the caps. The obvious repartee is to put dummies ands tests in there to set off the bomb if it’s monkeyed with.

IIRC, many years ago it was the Mad Bomber (?) who created clever things like mercury switches, so if the bomb was moved too much, it triggered the bomb. (Hence the bomb in “Speed” where they are driving over LA city potholes at 60 miles an hour but the bomb can tell if it is moved? Hollywood!) There are trigger switches - if the box is opened, or the bomb sits on a switch so if it is lifted, set things off. There are also booby traps like the trigger electronics monitor a circuit, and if it is cut, trigger the bomb. So one or more sets of blasting cap wires going into the plastique is a dummy. if you cut it, the bomb goes off. Or it’s also a spring-loaded switch, pull the cap out and the bomb goes off. Have two batteries, if one is disconnected, the other powers the explosion. There are plenty of options, the human imagination is a wonderful thing. So you can see why cutting the red wire first could be important.

One trick I read was to build a clay dam around the bomb and fill it with liquid nitrogen, the cold will stop any electronics working and kill the batteries, hopefully not triggering the bomb at the same time.

11

The way a person would build a device that can tell if the vehicle it is attached to has moved (versus hitting a pothole) is to tie the device to the encoder signal coming from a wheel position sensor.

As long as the wheels are spinning (for increases accuracy, you’d average the encoders for all 4 wheels) the vehicle is probably moving.

Accelerometers drift and are subject to interference from orthogonal axes as you pointed out.

You also want to time average - if the bus were still moving and, say, spent a brief period of time in the air without the wheels spinning, you wouldn’t want to set the device off just yet.

Notably, this does suggest a way to defeat such a bomb. Drive the bus onto a bus sized dyno and bail.

12

Or a treadmill :slight_smile:

13

Also, I hope the person checks the bus to be sure the speedometer works and is reliable. Plus a lot of that data goes into the on-board engine module on modern cars or other vehicles, meaning you need to run a tap off the engine - in the back in many modern busses. But odds are the speedometer is mechanical unless it’s a very modern bus…

GPS tech is likely the way to go, and hope it doesn’t go off under a wide bridge or in a tunnel, or in the radio shadow of tall buildings.

Of course, the engineer’s dilemma becomes important - the more complicated it is, the more likely something will go wrong. Then there’s the story of the President Zia’s motorcade in Pakistan. A minute after it passed over a bridge, the bridge blew up. The pundits speculated he had cellphone jammers in his limo, and once he was out of range of the bomb, it got the triggering text or call.

14

Well the OP article seems to sidestep the problem of which wire to cut by using wireless technology. Connect “bioharness”-like device to detonator to c4. BreAk any link in the chain and it will explode. And add some other gadget which can disarm bomb only through punching in alphanumeric code. Would that work?

15

Sure. Assuming the wireless link is “fail deadly” - lose the link for more than a few seconds, and kaboom.

Once crummy “techno-thriller” novel I read, the terrorists encased a nuke in concrete and had a setup like this. It couldn’t be disarmed or moved (GPS sensors, sensors in the concrete to detect cutting, etc).

Authorities actually had to negotiate. Well, they did until our hero messily tortured the terrorists for the disarm code, but it was a novel. (and our hero then chooses the opposite disarm code to the one the terrorist gives him following torture, which is what disarms the bomb)

16

What was that real-life bomb in real-life Las Vegas, I think, that was Hollywood-level untouchable?

17

This one.

18

Thanks. Not Las Vegas, but NV. From your cite:

[RIGHT]According to FBI experts, the Harvey’s bomb remains the most complex improvised explosive device ever created and a replica of “the machine”, as the extortionists called it, is still used in FBI training.[3][/RIGHT]

So, should be standard review material in all fiction-writing training as well.
ETA: makes you wonder about the “improvised” part. I remember that bothered me in news reports from our recent and current wars. Iran’s exported IEDs is a tautology.

19

Weapons might have been snuck in from Iran, but I don’t think they ever found a pile of identical, factory made, serialized EFP mines fresh from Iran.

It’s a good thing, to. If you think about it, a properly made EFP mine would pretty much kill someone every time. It would contain some kind of IR rangefinder sensor to set itself off at the right moment, and there would be an arming cable the bomber would bury. It wouldn’t be under the roadway, it would be 10+ meters away hidden inside a building, a bush, etc - not somewhere it could be found. The arming cable would have an IR receiver on it - the bomber would use an IR remote from a kilometer+ away to actually arm the device when a convoy comes past a marker on the road. No way to jam it and there’s nothing under the road to detect.

I have a friend who got IEDed twice in Iraq. There are soldiers out there who survived dozens of attempts. These people wouldn’t be alive if the devices weren’t “improvised”.