Honestly, I’m watching a war movie and a dude got hit by an IED. It got me thinking though, and I don’t quite get what is the lethal factor in an explosion?
There always seems to be fire in the movies, and it’s clearly a lot of force. But my question is what ACTUALLY happens to (I guess anything) that gets hit by a large bomb/explosion from a play by play/physics situation?
I feel like this is kinda dark, but I just had one of those curious moments and felt like this was the appropriate place to ask
In: Physics
The two primary risks for bodily injury due to an explosive are from objects being propelled by the explosive (shrapnel) and the pressure gradient created by the shockwave. The human body is pretty good at handling pressure changes…just not rapid pressure changes (which is how explosives work). And the damage (depending on the multiple factors) can be as simple as it “knocking the wind out of you” to collapsing your lungs or even as severe as liquifying your internal organs. You typically won’t see a lot of flame with commercial explosives. Some of the exceptions are with homemade explosives such as homemade ANFO where the ammonium nitrate isn’t fully saturated with fuel oil or there is simply too much fuel oil as commercially manufactured ANFO typically has excess fuel drained off prior to packaging.
Hollywood typically uses a lot of gasoline in their pyrotechnics for the visual effect. In reality, unless the goal is specifically the use of an incendiary explosive (such as napalm) you won’t see much fire (though an explosive could start a fire from dispersing the contents of a fuel tank).
Historically, the pressure wave has always been the primary source of injury. A good study on the topic is how trenches evolved during WWI through the use of sharp angles to reduce the effects of the shockwave though WWI was also where modern battle helmets became standard use as they weren’t commonly used during the wars of the “Napoleonic era” to reduce the effects of shrapnel (not bullets) injuring soldiers. The US Army did some fairly extensive testing in the late 1970’s and early 1980’s on the subject as well (nothing classified so it should be searchable) which is now the basis for how armored vehicles are designed increase survivability with the threat of IEDs. Of course, over the last 20 years things have also greatly changed and it has been discovered some vehicle types have better explosive survivability characteristics (i.e. the phasing out of the US HMMWV in certain environments for vehicles with higher ground clearance and better underbelly armor such as the MRAP and M-ATV).
Now this isn’t necessarily limited to military/counter domestic-terrorism application either. You see various technology manufactures who will test their equipment against explosives for various reasons especially in public safety application. For example, a two way radio manufacturer may test their portable radios to ensure the man-down emergency switch (triggers emergency mode after X seconds of the radio being horizontal instead of vertical) will survive a given explosion that could be survivable by the person carrying the radio but may otherwise incapacitate them or even that a mobile radio can be interfaced to the fuel shutoff switch of a car which turns off the fuel pump in the even of an accident (or can be triggered by an explosion) again to put the radio into emergency mode.
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