Making Shock Diamonds with a 3D Printed Rocket Nozzle

for some reason since the beginning of the year i don't know why i've been wanting to generate shock diamonds which they occur in the supersonic exhaust of like rocket engines and jet engines which there's they're just laying around everywhere so it should be quick simple video seriously rocket engines typically are large powerful and expensive which i don't have the resources to build a rocket like that so if i were to do it it would need to be small and weak so that it can be cheap that way when i inevitably blow it up or melt it i'm not bankrupt which which is important to me [Music] before i get into how i'm going to design and build this thing that's probably going to just blow up anyway i want to talk about my very limited understanding of how rocket engines are supposed to work that way you can kind of just like picture that over the smoldering wreckage of what i'm going to build i don't know why but when i learned how rocket engines worked the first analogy that popped into my head was a street with a building on it that was on fire but that's a little morbid for this example so let's say that someone walks in with a box of pineapple pizzas and says not to get political but and then naturally everyone runs towards the door as you get closer and closer to the door you can move faster and faster until you're in the door frame where you're moving faster than anyone else in the room once you get out on the street though you start bumping into people and running off in a random direction let's say that getting out of the same building as the pineapple political pizza guy wasn't enough for you you wanted to cross the street and get out of the state entirely then you need to pick up more speed and to do that you could put a really weird hallway at the end of that doorway so that the person passing through it would have more and more space to get up to sprinting speed before he hits the crowd now if the people leaving our really weird hallway are about as densely packed as the people on the street even though they're moving faster then they'll exit in roughly a column shape if the hallway was too wide then the crowd would jostle them until they're about the same density as the crowd itself it would be similar if the hallway was too narrow except for it would be the people exiting the hallway that would be jostling the crowd until they had enough space too we just they really like their personal space in more real terms hot gases leave the combustion chamber and move into the converging section of the nozzle where they speed up to mock speed by the time they hit the throat the throat is like the doorway in the last analogy and then from here the nozzle diverges which expands the gas to the atmospheric pressure or close to it so that you get as much speed out of that compressed hot gas as you can if the pressure at the exit and the pressure of the atmosphere match well enough then the gases leave the nozzle straight and uniform if the exit pressure is higher than the atmospheric it's an underexpanded nozzle and the gases expand as soon as they leave it if the exit pressure is lower than the atmospheric then it's an over expanded nozzle and the gases get crushed in by the atmosphere as soon as they leave the nozzle nozzles that don't perfectly match the atmosphere generate shock diamonds as the gases expand and collapse even the most well-designed rockets can generate shock diamonds because the atmosphere has ever-changing conditions it could be designed for higher altitudes just all sorts of things meanwhile my rocket might actually just explode which isn't something you want to be standing by so ideally there'll be some distance between me and it and then a physical barrier in between us as well so the first thing i want to make is something to remotely trigger the the rocket so that when i mean if it explodes it's on the other side of the barrier and far away from me oh no it's the shameless plug it's reminding you to like share and subscribe and do everything else that makes the algorithm happy i definitely could have designed something a lot simpler but there's something so satisfying about a good toggle switch and a button but i guess it's time to start actually building the engine but it shouldn't be too hard it's not like it's rocket science so the plan was to 3d print the entire rocket now the issue being is that it'll take hours and maybe even a whole day of printing and if there's an inclusion or any kind of air in the print i have to start all over so the new plan is to print just the injector and the nozzle itself and then use this pvc pipe as the main combustion chamber for the rocket using nasa's cea program i found the combustion characteristics of my rocket and then using a python code that i wrote myself i figured out the geometry i needed for the nozzle and the flow requirements for the injector now if you haven't seen the video i made on making rocket injectors i'll put that in the description but basically i just need to figure out how much fuel and oxygen i need to shoot into the combustion chamber to burn to hold it at a safe pressure i designed the components so they match the dimensions spat out by the python program and then i also made it so that they could be filled with refractory cement so that they can keep the heat at bay a little longer hopefully and now i just have to print it all out and put it together [Music] so [Music] with a month of preparation and math out of the way it's finally time to just test the thing three [Music] well that that didn't work uh didn't even explode that that would have been better than just you know nothing happening but uh here's what i think happened pressure fed rocket engines using get this pressure to feed fuel and oxygen into the rocket so that it can run they also rely on things like check valves and solenoid valves that can be operated electronically to safely fire the engine and with that we already have our first problem being that inert gases to pressurize fuel tanks are expensive and i don't have the money for that so i'm going to use air which you know mixing an oxidizer and a fuel under pressure is what they call in the industry a bad idea but seeing as i was 50 feet away behind a 12 foot brim of dirt wearing hearing protection and eye protection with nothing within hundreds of yards to be damaged i wasn't too worried about the safety of it all more of that if the fuel tanks exploded i would have nothing left to test with so to prevent that without also making the rocket so large that it was hard to handle i needed to reduce the amount of fuel and oxygen that was pumped in by the injector and obviously i cut it too close because every day that i was out there testing i was chasing issues with ignition and plumbing and i was thinking of ways to fix those issues by adding things like a fuel preheater so that it would be easier to ignite and i realized that i was getting so far away from what the point of this video was which was to make a simple rocket engine that was capable of making shock diamonds so i went back to the drawing board and i came up with this i'm sure you've heard of a wush rocket they're in like every science class a teacher will put some alcohol in a bottle and they'll just ignite it with a match and it goes whoosh now i don't know if the exhaust is supersonic but i know that all the rockets that i've seen they don't have shock diamonds which is again the whole point of this so my goal is going to be to print a nozzle that i can twist onto this cap and see if i can't generate shock diamonds with a wish rocket [Music] and in no time at all i made four nozzles that i want to test nozzle one is really simple it basically assumes that the neck of the bottle acts like a throat of a rocket engine so it just expands from the end of the bottle nozzle 2 is similar but it converges at least a little bit at the end of the bottle before diverging nozzle number three has a very large converging area to a very small throat and then it diverges just a little bit the fourth and final nozzle is kind of just for fun it's an aerospike nozzle which if you haven't heard what those are i'll link an everyday astronaut video in the description but basically they try their best to match the atmospheric pressure wherever they are so they actually might be incapable of making mock diamonds i don't know now i personally think that the third nozzle has the best chance of producing shock diamonds but heck what do i know i've already made one rocket that doesn't work this video so what do you think which nozzle do you think has the best chance of producing shock diamonds and since there's a non-zero chance of this thing just popping i'll be wearing all the safety equipment and then i'll also be kneeling behind a quarter inch piece of construction kevlar that i just have laying around and i'll also be putting sawdust into the bottles that way there's some impurities to burn bright and yellow so that we can see the exhaust more easily my poor neighbors probably just see flashes of fire and then hear maniacal laughter in their backyard because finally there they are out of the simplest little rocket they're shock diamonds now i think they're in the whole flow but they're only showing up in the little licks of flame from the impurities from the sawdust and whatever else in the nozzle now there's a lot more test footage and i'm gonna shoot them into the air too because why not but i'm gonna stop for a second and wrap up the video here by saying thank you for watching first of all and i want to emphasize how great it felt to have a rocket that didn't work for a month and a half and then i stopped and just kind of reevaluated and made a simpler rocket that made shock diamonds on like the third try and also elon man you're overpaying for your shock diamonds by just millions and millions of times this costs like a quarter so if you need any help just just hit me up man it's no problem uh uh so so thanks again for watching i hope you enjoyed it now i left in that whole failure of a rocket because i thought it was important to show but it also kind of helps explain why i haven't posted in like two months so if you didn't like it or found it boring just let me know in the comments and i'll just leave it out next time i might revisit this and make a full-fledged liquid fuel rocket engine since this one kind of turned into the vapor version of a solid rocket booster where all the fuel and oxidizer is mixed in the combustion chamber already before it's fired but that'll be when i have more time and money to spend on this for now the next video is gonna probably be a robot video so subscribe if you want to see that in like four five maybe six months who knows

Channel: Sciencish

Views: 113,911

Keywords: Sciencish, Shock Diamonds, Mach Diamonds, 3D printed rocket, rocket engine, Rocket Nozzle

Id: LFwDNtsQOBw

Length: 14min 35sec (875 seconds)

Published: Thu Sep 24 2020

Reddit Comments

[u/Aerothermal]

Here's a little video about de Laval nozzles and critical expansion of rocket nozzles.