Often people hold themselves back thinking these things are unobtainable for them, or too difficult to learn. Yet the basics of physics are used in all weapons, the basics of electrical engineering are used in all electronics. it doesn't matter how in depth it goes, it matters how patient you are at resolving how many layers of easy stuff before it becomes what we know today.
The million layered onion.
Nothing in this world is not simply layers of rudimentary functions. Its just a matter of learning those first.
Like reverse engineering, its easy when you reverse everything in life. Its hard when its your job. why? because jobs makes big men have big egos and lose their patience.
I was asked the other day how a pressure washer works. I started off thinking about seeing the water shooting out of the hose quickly enough to break caked on dirt off of bricks. That hose would connect to a container with some sort of motor going that makes it super loud for some reason. Water is either connected to a standard hose or kept in a storage container. Next I though, how could I get water to go forward at any sort of pressure. Well, the basic way that some fish tanks work, for example, is that the pump involves pulling air in, using air to move the water, then the air returns to the top. This works by sucking to form pressure with air, then applying that air pressure to the water. Now, to make that impact something bigger, we could use a storage device that's metal (or harder plastic I suppose), and build air pressure quickly into one side with a single small motor and a fan. This needs to have open for lots of air to pull from but asserted into a smaller contained space. This can push on top of the water, to cause the water to push out quicker if we also apply some air into the tube when running (directing the water to suck it out will help push it quicker). The nozzle shape might matter too, such as if you've ever put your thumb over half the water hose to make it go faster/harder/further, so lets get a nozzle with a thinner shape. Hmm... These would need to be maintained at that so you would almost have to set specs on what capabilities it has based on what materials are used. Okay, now that I've spent a whopping 2 minutes thinking about this, lets look it up.
http://www.explainthatstuff.com/pressurewashers.html - seems to agree
https://www.briggsandstratton.com/na/en_us/buying-guides/pressure-washers/pressure-washers-101.html -- seems to agree
https://www.hunker.com/13409072/how-an-electric-water-pump-works -- seems to agree with pump mechanism
https://www.youtube.com/watch?v=_BAnnTLpros -- different type, but same concepts, different method of developing pressure.
https://www.popularmechanics.com/home/how-to/a152/1275136/ -- different type of pump, same ideas
https://images-na.ssl-images-amazon.com/images/I/31I923IYxhL.jpg - pump.
https://www.kaercher.com/int/inside-kaercher/difference-kaercher-magazine/kaercher-stories/how-does-a-pressure-washer-work.html -- also seems to agree.
So I think it's safe to say some shit I came up with just trying to deduce the best answer seems apt. At least enough to understand founding principles of it. But how can we hack it?
WE CAN MAKE IT A WEAPON!
No but really, shrink the nozzle, increase pressure, weaken hardened metal chambers with acid, you know... weapon stuff. Because that's really all it takes is understanding to make anything dangerous.
What about making it useful? Why not use a pressure washer's idea for other rapid water tasks? What about cleaning a pool using a crawling bot that blows gunk from getting stuck to the sides and bottom and then use the pool's filtering system as the source for pressure. Once it gets off of the filter as clean, split into two chambers with priority to the cleaning bot. giving the cleaning bot the ability to pump cleaner water in as it breaks apart dirt.
Or maybe, if you live by some water, use the tides to tick over motor to generate electricity for you. It's the same idea, pressure, chamber, motors, it's just repurposed.
This is how we live. Sometimes thinking like this is criminalized in various nations around the globe. Sometimes curious kids get curious time in jail because of curiosity. But at a functional level, everything in life is this trivial. Go out, explore, adapt, learn from the world around you. To think that the world is not such a trivial place, to think that anything is ridiculously complex, is simply asking for trouble.