Why don’t rifle bullets detonate explosive reactive armor?
In: Engineering
If you mean like tank armor that has an outward facing charge layered inside of it to counteract the impact of rockets and missiles, it’s because the rifle bullets never penetrate the outer layer of the armor. The armor is just plain bulletproof.
The impact of the rifle bullets aren’t energetic enough to initiate the explosive in the tiles. The explosive in the reactive armor is designed to detonate when initiated by something like a shaped charge.
A bullet could hit the armor at 0.9 to 1.2 kilometers per second. A shaped charge will advance at around 7km/s.
They are too slow/don’t have enough energy. Modern explosives can be made insanely stable. By tuning your explosive mix you can basically set the minimum energy needed to set the explosive off. It’s set at a level that is above any small arms but still well below a anti armor round. This is easy as the difference in energy is absolutely enormous. The M833 an anti tank round that is effectively obsolete has a potential kinetic energy of 6.75 million joules. A 50 BMG has a potential kinetic energy of 0.02 million joules. or 1/400 of the energy.
For an actual ELI5:
For the same reason that a balloon doesn’t pop when you shoot it with a spitball or a mouse trap doesn’t go off when you drop a feather on it.
There isn’t enough energy or force and it was designed that way.
Slightly less ELI5:
ERA is designed to be resistant to things that would otherwise not penetrate its base armor. For context, body armor plates that are designed to stop 7.62mm rifle rounds are rated to be resistant to them at essentially point blank range. Modern tank sabot rounds have their penetration value measured at a KILOMETER AWAY.
Very simple: not enough energy.
There’s a certain amount of energy that has to be applied to modern explosives to detonate them. They’re designed that way to make them safer to be around. We want them to explode, but only when they encounter the exact conditions we’re after.
Chemical engineers have spent a lot of energy finding ways to make explosives safe, that includes making sure a bullet won’t detonate them.
A 5.56 bullet might have a muzzle energy of 1500-2000 joules. An explosive might require 10,000 joules or more to go off.
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