In Die Hard, John McClane detonates a block of C4 by sticking a few detonators into it, strapping it between an office chair and a monitor and dropping the whole lot down a lift shaft. Are modern detonators impact-sensitive enough for this to work?
This was probably cinematic license, but in the same film the whole terrorist seige was staged in order to make the FBI cut the power to the building to disarm an “electromagnetic lock.” Are there any locks which require continous electric power to remain closed? Why could the circuits “not be cut locally?”
In Die Hard III, the bad guys made bombs from a two-component explosive which became a sensitive detonating explosive when mixed. Does this stuff exist? What, if anything, would it be useful for?
I figured the monitor on the chair with the explosives was there to provide an electric charge which, I believe, is whats needed to make C4 go BOOM. Monitors (any CRT TV actually) maintains a significant charge in its capacitors even when unplugged. This is one of the reasons it is VERY unwise to do TV repair on your own unless you’ve been trained to do so (the charge in the TV can be anywhere from very painful to lethal).
As for the electromagnetic lock I have no idea really. It would be thoroughly stupid to have a lock that requires power to stay locked and that power could be cut locally. Forgetting artistic license for a moment and looking for a ‘real’ answer I’d say they’d probably have battery backup for an electromagnetic lock hidden safely in the vault. However, if power is cut to the entire building then the lock assumes some worse disaster is afoot and unlocks itself. For instance, I’ve been in computer rooms that required key card access to enter and leave. However, if you hit the fire alarm all doors would unlock.
I don’t know what the bad guys used in Die Hard but for a two component explosive Nitro Glycerine comes to mind. Separately they’re pretty harmless but watch out when you mix the two. I imagine there are dozens of things that are harmless separately but dangerous when mixed.
I can’t answer the C4 question, except to say that in another movie (so it must be true) a lump of C4 was detonated by shooting it, so perhaps C4 is susceptable to detonation from high impact forces… of course, this doesn’t explain the relevance of John McClain shoving detonator caps into the C4. I don’t think it’s reasonable to assume that the point of the monitor was to somehow provide a charge to the caps - I think it was just to add weight to the payload. (not debating, he said cautiously)
As for the electronic lock, I think that part was fairly reasonably explained. The electronic lock was a failsafe. There were several other electromechanical locks that had to be defeated before the final lock was released by the power cut. Presumably a power cut would have to be done after these preliminary locks were disengaged. As to cutting the power locally, they didn’t elaborate, but they did say that it was on a separate secure feed. Also, remeber, the bad guys were supposed to be terrorist not robbers. They wanted the power cut to be the FBI’s idea so it would not be detected and tip their hand.
The CRT strapped to the C4 and caps might provide enough of a mechanical shock when the tube imploded on impact with the ground to set off the caps which in turn set off the C4.
I don’t believe C4 can be detonated by shooting at it. I’ve been told that it needs a very sharp shock wave to detonate. Could have been mis-informed though.
C-4 explosive is extremely stable and requires two stages to detonate.
You can stomp on a brick of C-4 all day long, drop it from any height or drop weights on it and it will not explode.
You can light it on fire and use it to cook if you don’t mind the gasses (very toxic and noxious), you can use it to light fires or burn through brambles if you want to as it does not extinguish easily.
However, when ignited do not stompt it out or you will detonate it. C-4 requires a detonator which is a less stable substance in a much smaller quantity (usually a det-cap or in the construction industry “blasting caps” which I think are pretty much the same thing that they use in the ARMY) which can be exploded through impact or from fire alone. A det cap is similar to the primer cap used in modern ammunition but usually somewhat more powerful (maunly due to size) and typically wired for electrical detonation.
You can also use det-cord to explode C-4. Det-cord is usually packed cordite suspended in a polymer matrix and coating a copper filament wire. Wrap det cord around a block of C-4 and make a circuit on a 9V battery and it go “boom”.
Det-cord is more stable and more usefull that det-caps for most purposes but is also more cumbersome and difficult to set up. Det cord is great for clearing helicopter landing fields in bamboo as you just wind it around the bamboo stands low to the ground in an area large enough for the chopper and send a charge through it and “pow!” instant clearing. Neat stuff. Wish I had a few spools of it, it’s real handy for cracking cement driveways into manageable chunks for removal. I hate jackhammers.
There are two types of electronic door locks, fail-safe and fail-closed. Fail-safe locks are generally used on fire exits, because building codes require these doors to be open during a power failure or fire alarm. They are almost always electromagnets that attract a metal plate on the top of the door. When the power is cut to the electomagnet, it loses it’s ability to be a magnet,and the door opens. These are strong magnets; I’ve been told by my security company that the door will break before the magnet will give.
Fail-closed locks are usually inside the mortise. They require power to disengage a spring in the lock, and then open the door. These are usually found on office doors that are not part of the fire escape route.
Up my alley I would say, since Mag locks and electric strikes are part of what I do every day.
I shall coever the two most common electric locking devices.
Mag lock. In basic description, a Magnet that is mounted to the door frame and pulls a magnet to secure the door. These most often are installed with a battery backup the standard battery powers the lock for approx 8 hours. To exit there has to be an emergency exit button near the interior of the door, they can also be wired into a fire system so that power can be cut to the lock in case of a fire. Most of the Mag locks I install can withstand 500 to 2000lbs of pull.
Electric strikes. These are powered latch plates that come in two functions, Fail safe and fail secure. Fail safe means when power is cut the strike will remain rigid when power fails so exterior security is not compromised.Fail safe, leaves the strike in an open position to allow the door to be opened from the exterior. Electric strikes work with existing hardware so, unless unusual circumstances are in play, you can always leave thru a electric strike door from the inside no matter the power situation.
As for the explosives I do not have a clue. But, if your willing to drive to Huntsville Alabama with a case of Killians and the explosives we can spend the weekend finding out
I’ve seen the magnetic locks on college campuses a lot… The magnets are exceedingly strong as long as you maintain contact, but if you can get so much as a penny between the magnet and the steel plate, it’ll open right up easily (well heck, you’ve got to be able to leave the dorm doors open somehow!).
As for a binary explosive, I can see plenty of applications, namely, anything where safety is an issue. You need to get the stuff from the factory to your quarry/demolition site/whatever, and you want it to be inert in transport (don’t want all your trucks blowing up on the freeway). Then, on-site, you mix them together, put them where you want the explosion, and detonate. I’ll admit, though, that I’m not sure why terrorists would prefer the stuff to something already mixed.
I’d still like to know how impact sensitive a modern “cap” or detonator is. A long time ago they contained mercury fulminate and they really were dangerous to handle - T.E. Lawrence lost a man to a detonator accident.
As for the X-Files movie - I saw that one in a cinema and can’t remember a thing about it. Can’t have been as good as Die Hard!
