This reminds me of one of my first crappy videos when I built foil rockets after being inspired by the king of random when Grant was at his best.( Bit of a copy of his style but I was learning) Without Grant Thompson I would never have been inspired to start RUclips and find my own niche, I will be forever grateful. It took me about 2 weeks to perfect the no fin match rocket, but to my knowledge still the easiest and furthest range of any match rocket.
Grant Thomson was an inspiration to many of us. I now have an arsonal.of clothespin guns because of his vids.It's good to hear he inspired you to go a step further.🤘
I learned this lesson the hard way back in the 1970's, when one of my own highly modified rockets went sideways shortly after launch, causing all of us to run in different directions. At that point I went back and read all the info on "center of pressure" and "center of gravity" that I had come across before but didn't quite make sense. After the renegade launch however, the pieces started fitting together and I had an "a-HA!" moment. Physics - it's not just a good idea, it's THE LAW!
@@EstamosDe I think it was many years before I did any rocketry after that - as a mentor for some young kids. We stuck to the kits and didn't try anything too dangerous - except perhaps for climbing quite high in a pine tree to retrieve a rocket.
If you are good at rockets, can you confirm something for me? He didn't explain why the center of pressure had to be lower in the video, so I would like to know if my guess is correct. Here is my guess: The center of gravity is like the point of rotation when the rocket wants to turn. When the center of pressure is lower, the drag will be higher on the part below center of gravity compared to the part above it, and thus it will be pushed back to the right orientation, if turned. So, it is a question of whither the point below the center of gravity produces more drag than the part above it. When the center of pressure is below the center of gravity, you are sure that the part below center of gravity will produce more drag.
I had a similar experience in Boy Scouts. I made my own 2-stage rocket design and was quite pleased with it. When it launched, it started doing corkscrews and impacted a wall at the school we were flying our rockets at (the wall was in the middle of the large grass field behind the school and presumably for bouncing a ball against). The rocket exploded into a bazillion pieces! I remember that people were offering their condolences. The truth is that I was a little annoyed that the rocket didn't work, but very pleased with the flaming wreckage that had scattered some distance in all directions. I remember saying "what you you apologizing for? That was awesome!" I think I was a demented little kid.
I did the same with a homebrew rocket we made with a multistage motor whose second stage was a bag of gasoline and firecrackers. We launched it from the back yard and time seemed to move very slowly as it headed for the house, barely clearing the roof. Fortunately, it landed in an empty road intersection.
You’re an absolute mad lad. I can’t believe how many ideas you have for videos without watering down the quality. Everything you put out is genuinely interesting and entertaining and you make like a video a day…
In marine architecture engineering "center of buoyancy vs center of gravity " a point called "meta center" where as center of gravity must be below center of buoyancy or ship/boat capsizes . Similar . Excellent 👍
But the center of buoyancy moves as the ship/boat rocks in the water. If the boat’s hull is vertically sloped at the waterline, yes, it will capsize. Same if the slope is negative, like on a submarine or the stealth ship. But rowboats have a center of mass that is definitely above the center of buoyancy, and they don’t capsize because of the shape of the hull. Think: when the rowboat is on dry land, it’s effective center of buoyancy is at ground level, definitely below the center of mass, and the hull is completely curved. Based on what you said, the rowboat should tip over under these circumstances, but it doesn’t. Because as it rocks, the center of the normal force moves. Edit: self righting objects with round bottoms on dry land exist despite the fact that the “center of buoyancy” for objects on dry land can only be at ground level, certainly below the center of mass.
Missed an opportunity there for Kerbal Space Program 😭 e.g. to demonstrate one of the consequences of a finless rocket, with locked engines and no supporting thrusters. Learned it the hard way, to properly fin my core stages, and boosters, when they're needed. It's an excellent game for the channel viewers, and a bit of a shame it wasn't used here, but regardless, still a great and informative video!
@@chrisfuller1268 before you buy it, beware that it is a bit more complicated than usual games. The tutorial is essentially a physics lecture and is hideously long and you would need a lot of experience along with trial and errors just to make a rocket that doesn't immediately crash. So, it is great because it provides realism along with a real brain challenge, but not very reccomended if you are looking for something that gives instant results
When I was a kid building rockets, once we found the center of gravity, we'd put a string around that spot and hold it with tape. Then we'd spin it around over our heads, letting the string out till it was a few feet. If the nose took the lead as we wanted, the center of preasure was behind the center of gravity and it was ready to fly. Just needed to repeat the test if you made any modifications to weight or shape. If you didn't, you got a quick reminder when you launched it :)
Gets much more difficult when you start trying to swing 7’ tall high power rocket around ;) but definitely a great quick and dirty test for low power rockets like the ones flown in parks
this is a great video, I teach 4H kids model rocketry and you gave me good examples of why rockets need fins and explanation of center of pressure and gravity
The trick to the shadow method is to account for the total fin area. The shape drawn only accounts for two fins so the tail end is slightly light causing the center of pressure to move forward. At model scales you can just eyeball an extra amount, 1/2 the length of the fin, on the end of the fin profile on each side. With the actual Estes rocket we used to add a few metal washers to the bottom of the nose cone to bring the CG really far forward.
What if the shadow was created by spinning the model and drawing the furthest points at any point in the rotation? This would also include any other deformities.
@@glenncurry3041 Imagine if you had four (or more) fins. Even rotating the model you still will only account for two fins. Since this method is to let gravity simulate the effect of wind pressure, your silhouette profile needs the total surface area (weight) of all fins to be accounted for, and in the correct lateral position along the centerline. A 4 fin rocket silhouette would have fins twice as wide as the actual model. Another way would be to cut out the correct number of fins and lay them on a finless silhouette at it's base.
@@3DPDK Interesting. I am totally new at this. It would seem there would be a quantity/ density of fins that would at some point be the same as just a bulge in the cylinder? Which compared to an ever multiplying surface area of each, would suddenly drop to just that increased girth? And that could reduce at higher air speeds as laminar flow got wider on each surface?
@@glenncurry3041 This actually works. It works with even pressure in 360°. Not so much a bulge, but more of a flare; like the bell of a horn in the tail end of the rocket. The cons are that it applies a constant resistance or drag even if the rocket is flying straight into the air stream, and at high speeds it creates a huge amount of turbulence in the exhaust stream. The problems on a model rocket is being able to make the shape without adding a lot of tail weight, as in 3D printing it, and difficulty with launch wire clearance. Both problems are solvable, but the constant drag limits rocket altitude.
When I saw the thumbnail and the title, I initially thought "ah, I already know what the rocket fins are for; for stabilisation." I was about to skip it when I thought, "wait, maybe there is something I don't know just yet" so I clicked it. I already know about the concept of airplane about how they fly, the airfoil, the CG, flaps, ailerons and other controls like Thrust Vectoring. What I didn't know is the Center of Gravity should also be applied on rockets, and the center of pressure is new to me. It's worth the click. Thanks a lot.
When I was a kid, all my weird rocket inventions didn't make it very far before spiraling. If I had this video back then, I would probably be in jail or something as a teenager 😂😂
do it, there is quite a bit of satisfaction seeing something you designed and built take off at nearly the speed of sound and reach 10,000 feet. I did a 3" dia 6.75' long 2 stage that made it to 13,800 feet, it ran on a K-500 and a J-125. I made the electronics to fire the staging and chute ejection timer from scratch, custom built the rocket frames to handle the stresses, and it was done back in the mid 1980's ( when Tripoli had just a mere 550 members)...
Are you really a rocket scientist or engineering stuff going inside of a rocket/spacecraft? I worked at NASA for a decade designing spacecraft components, scientific instruments, training astronauts and operating instruments on-orbit and don't think I ever met a rocket scientist. I did work with a couple in defense applications, however.
My family was really into rockets in the 70's. NOW I know why my younger self had to duck and cover a few, ahem..., more than a few times. I see Cynthia Cantrell before me had the same joys. Thanks for the memories Action Lab!
I have always been interested in rockets but the sheer maths involved in rocket science always made my head hurt. This video helped me understand the basics of design principles of rockets. Thank you very much The Action Lab, loved this video.
Lol there's nothing called "rocket science", it's aerospace engineering. Also the math used is actually pretty simple, like 90% of the math is literally just multivariable calc and linear algebra and some ODEs and fourier analysis. That's about it really. And the mathematics is actually really fun!! There's so much good stuff on youtube to learn that math. (Dr. Trefor Bazett on youtube, you can learn the calculus and ODEs stuff. And Gilbert Strang lectures on linear algebra on youtube also buy a good book on those subjects too!) You can easily learn it mate, anyone can! don't get intimidated by it, math is actually really beautiful once you actually start learning it
Brilliantly explained! Center of pressure is just like center of gravity, except that, it doesn't differentiate between regions of different mass densities, but rather depends on the cross sectional shape as seen from the direction of the wind.
As a kid I used to just check model rockets by spinning them around me with a string attached at the cg outside. So basically your fan method, but without the fan. Putting a motor in is important since it’s weight in the back. You could get a rocket to take off unstable tumble then stabilize halfway through the burn and dart in a random direction from the change in cg as the fuel burns.
I always thought those were the most entertaining. And then you can track down the maker and sternly ask them why the didn't properly verify the physics before launch. Lol
As a kid, I had a model rocket that would never fly right, it'd just spin around in circles, and I couldn't figure out how to modify it to get it to work. I think this is why! Thanks for helping solve a decades-old personal mystery!
So do fish. Their dorsal and top fins help them keep balance and swim forward, even against strong water currents. Without these fins, the fish will just propel in any direction that the local water current is in.
A good video, as always. One small point is like to mention though it's that when a coiled spring is compressed or stretched it will impart a rotational force on each end. In many of the better racing cars they have a flat bearing under the coil springs so that the lateral force created by the compressing spring doesn't try to bend the damper shaft, and so create more friction.
This makes me appreciate the complexity of rocket science even more now. Watching this I kept thinking about rockets with liquid fuel tanks and how as it’s used, there is a constant shift in weight distribution.
By coincidence, i had a talk with someone this morning about the history of aircrafts and how design could be related to the anatomy of birds. At a moment we were talking about the concorde plane and It's positioning of the wings. I understood the stability by referring to how a trailer can be loaded so you have a stabile path when pulled by a truck at higher speed. Dependent on where the center of gravity is relative to the area where the wheels make contact and carry the load. I was kind of thinking afterwards if the analogy was fully relevant, tbh because of the axial pivoting dynamic in between and difference of pull versus push. After seeing this video, i think i can understand this modelling and placing of wings even better in a isostatic solid body model. Thank you for your video's. They have a certain degree of diy integrity and innocence that reminds me of when i was young and did all kinds of tests and small maquettes because of some facets that the facination of mobility in life brings.
@@yerri5567 So you know the A10 Warthog? It's got a Gatling gun basically that goes *brrrt?* Well take that concept that apply it to other fast things, like money printer go *brrrrr* which I think is the original or whatever fast occuring things
Got a beginner model rocketry kit when I was about 12. Spent a week or so putting together my first rocket. It wasn't the prettiest but it was technically and mechanically correct. It was basically a bottle rocket with a parachute. My dad and I went out into the pasture away from any buildings and set up the launch pad. We made sure the sun was behind us and got back a safe ways. Then came the launch. We did the traditional countdown together as I flipped the saftey and hit the ignition. Fire blasted out the bottom and she took off into the sky. Up, up, up she went. And kept going. And kept going. And she never seemed to return. We saw no chute deployment, no explosion, no fiery falling shell, nothing. It simply went up and stopped existing, for all we knew and still know to this day. We searched the neighbors' fields downwind, we searched in directions it couldn't have gone. We searched for a couple days until my dad gave up; then I kept searching for a couple more. We never found any trace of it. 30+yrs later, I still wonder about that rocket...
With the advent of computer guidance systems that function at correcting directions thousands of times a second, tailfins may no longer be necessary but, the costs involved make it virtually impossible for fins to ever completely go away. As a kid in the 70s I once accidentally lit a hill on fire by seeing what would happen if I ignited a little Estes rocket without the fins attached. Lesson learned the hard for sure.
Great video! Minor point, but air resistance, or drag, is partially a function of medium density, velocity, and cross sectional area. I believe maximizing cross sectional area actually increases the drag, but your second reason for pressure stability is great. Maximal cross sectional area also maximizes volume/load and decreases costs for wall materials. Think about the drag on a sheet of paper traveling laterally (i.e. as a magic carpet). It will exhibit negligible drag. But it also won't be able to carry anything as it has virtually no volume.
I think the cross sectional area is fixed, as you need to carry a certain amount of fuel. then the drag would be smallest for a cylinder, as less perimeter means less contact with the air around it 😅 But I agree, could've been said more clearly... Like a circle minimizes the perimeter for a fixed area, not that it maximizes the are for a fixed perimeter...
Better Help sounds excellent really… many just need someone to listen to them. Personally I have gained mental awareness by Painting, but only after wrestling with light with pencil and some of the loveliest paper from Italy…Fabriano…the oldest paper company.
I remember a couple of Estes rockets that were called 'tumblers'. Instead of a parachute, the charge that would normally blow the nosecone off just caused the spent engine cartridge 'aft' a few inches. This resulted in the center of gravity shifting aft, past the center of pressure. So on the flight up with the engine forward, it was stable and launched straight up. After burn out the engine shifted aft and the rocket was unstable. So it tumbled around and around as it fell, this limited it's terminal velocity so when it landed in the grass, it was undamaged.
and the fun thing about it all... the CG moves forward as the motor burns making the rocket even more stable... so, when doing the CG testing, do it with the motor you plan to use or else the CG may be behind the CP and once it comes off of the rod it will go wacky...
The same principle can be applied to keep trailers from swaying. If the center of gravity is behind the trailer's axle, it will sway when you pull it. The axles are where the upward force is applied to lift the trailer so it acts like a center of pressure.
Much easier and faster way to find the center of gravity: balance the object on 2 fingers or 2 sticks or something and move those 2 fingers/things towards each other. Where they meet is your center of gravity.
that can only be done on simple surfaces, like the most famous one, the pencil. however when the mass is unbalanced (ex. you put one of those eraser attachments onto one side) you can't really gauge the total mass and thus also the center of gravity unless you balance it further out onto the "attachment." by concept it just might work cuz it sounds logical but practical applications are of course more complex. i'm not a physicist or something btw, just a regular worker who's fascinated by how things get easier if you understand them more lol
@@runic6452 Actually it does work even with unbalanced masses! Try it with a broom, that is quite obvious unbalanced, and you will see it works there, too. The point at which it fails is quite obviously when the surface you are balancing it on changes, e.g. when the center of gravity is somewhere where the fins of the rocket are attached. But for the examples in this video it would have worked perfectly.
Another cool experiment shows how a rocket's roll about its vertical axis can be induced by coordinating the other two axes. Hold a coat by its neck and move your hand in a circle. If you move your hand in a clockwise circle, the coat tries to twist clockwise and vice versa. This is why controls for only two axes are sufficient to orient a rocket in 3D.
"Largest area vs perimeter -> least air resistance" kinda the opposite, that gives the greatest air resistance for given perimeter, so that's disadvantage. BUT. What largest area takes as disadvantage, it gives as advantage in the way that it allows for largest volume for given material (if we're talking cylinder-like shapes, or else sphere is the largest volume).
The ancient Chinese rocket design with just a stick 7x the length of the motor could be an interesting test. In high school, sometimes I'd take a model rocket motor and just tape a long stick to it like a bottle rocket, not the best or most efficient, but flew surprisingly straight. There are modern firework rockets with this design and usually a cone on the top.
Never thought I might say I'm a rocket scientist! This was far more interesting than I expected. But now I'm filled with questions! The sideways-in-the-wind aspect is surprisingly crystal-clear; Why, then, don't they, say, have two thrusters, one at each end, and redirected at a 90degree angle...? If it wants to fly sideways, why force otherwise? And that center of pressure method seems confusing; What would happen if the tailfins were replaced by a cone?
If you try to fly with thrust on both ends, the rocket will break at the middle. It's like a soda or beer can after it's empty, to crush it top to bottom requires some strength to make the sides collapse. But press on an empty can from the sides, and it folds easily. You want rockets to be light for performance, if you make the sides thick enough to not get damaged, the rocket will be very heavy.
Love the channel! Big fan! Now criticism: The cylinder - fan experiment is not precise as the fan is already blowing air before the cylinder is suspended. The cylinder could very well move sideways even without the air flow in the perspective of us audiences. Somewhat more scientific approach would be to first ensure that the cylindrical body is stationary in suspension without any air draft. The conclusions drawn in the video, therefore, could have been wrong. (It certainly isn't wrong though.)
Technically extending the rocket body would shift the center of pressure forward more than the center of gravity. Aka making it less stable. This is especially the case since your motor and motor mount is in the back. Usually little model rockets just have a parachute in the front.
Another way to test for stability, tie a string to it at CG with loaded motor, swing it in a circle around you, if it flies straight, it will fly fine.
That's exactly what people should watch today instead of TikTok and Instagram sh*t. Thanks a lot for making those videos!!! I've learned more from a single 10 minutes video than from my entire time in school 👍 Sorry for my English.
Or folks shud watch what they enjoy and folks shud just not be all judgmental about it. I know many a science educator makin tiktoks that get many millions of views. Your premise is based on a falsehood you assume from your limited worldview.
@@SylviaRustyFae I'm not talking about scientists that make TikTok or Instagram education videos. I'm talking about the other 99% of the content and content makers that you can find there. And hey, look around you and think a bit before you write anything. Most of the people today (especially teenagers) are using TikTok and Instagram or whatever just to spend their time but they learn nothing while doing it because most of them are watching the sh*t content of it. I'm not judging anyone because I don't really care about what anyone watches and shares there, I'm just saying that it could be better to teach people and children to do something useful that could make them smarter and better (like watching videos like this here) and not spend their time on crapcontent. So the next time you comment just think a bit and look at the facts.
@@SylviaRustyFae And that's called degeneration. The action lab could make a video about trying to explain your IQ. I don't see any reason to fall to your level and to continue this conversation so have a nice day.
Funny that when the centre of gravity and pressure are at the same spot, when it is just a tube, it still turns seemingly to maximize its drag. You'd think it would turn to minimise the drag if anything.
It helps to imagine the rocket pivoting around its center of gravity, AKA center of mass, while the air pressure pulls downward from the center of pressure.
This reminds me of one of my first crappy videos when I built foil rockets after being inspired by the king of random when Grant was at his best.(
Bit of a copy of his style but I was learning) Without Grant Thompson I would never have been inspired to start RUclips and find my own niche, I will be forever grateful. It took me about 2 weeks to perfect the no fin match rocket, but to my knowledge still the easiest and furthest range of any match rocket.
Now you make none lol
@@domiepotato And? A bit like you..but successful lolz 😂
Grant Thomson was an inspiration to many of us. I now have an arsonal.of clothespin guns because of his vids.It's good to hear he inspired you to go a step further.🤘
@@allensparks285 Thanks, I think he helped a lot of people without even realising it. Nice legacy to leave.
Yeah, TKOR is awful these days. It's slowly dying.
I learned this lesson the hard way back in the 1970's, when one of my own highly modified rockets went sideways shortly after launch, causing all of us to run in different directions. At that point I went back and read all the info on "center of pressure" and "center of gravity" that I had come across before but didn't quite make sense. After the renegade launch however, the pieces started fitting together and I had an "a-HA!" moment.
Physics - it's not just a good idea, it's THE LAW!
And what about your latest rockets? How did it go?
@@EstamosDe I think it was many years before I did any rocketry after that - as a mentor for some young kids. We stuck to the kits and didn't try anything too dangerous - except perhaps for climbing quite high in a pine tree to retrieve a rocket.
If you are good at rockets, can you confirm something for me? He didn't explain why the center of pressure had to be lower in the video, so I would like to know if my guess is correct.
Here is my guess: The center of gravity is like the point of rotation when the rocket wants to turn. When the center of pressure is lower, the drag will be higher on the part below center of gravity compared to the part above it, and thus it will be pushed back to the right orientation, if turned. So, it is a question of whither the point below the center of gravity produces more drag than the part above it. When the center of pressure is below the center of gravity, you are sure that the part below center of gravity will produce more drag.
I had a similar experience in Boy Scouts. I made my own 2-stage rocket design and was quite pleased with it. When it launched, it started doing corkscrews and impacted a wall at the school we were flying our rockets at (the wall was in the middle of the large grass field behind the school and presumably for bouncing a ball against). The rocket exploded into a bazillion pieces!
I remember that people were offering their condolences. The truth is that I was a little annoyed that the rocket didn't work, but very pleased with the flaming wreckage that had scattered some distance in all directions. I remember saying "what you you apologizing for? That was awesome!"
I think I was a demented little kid.
I did the same with a homebrew rocket we made with a multistage motor whose second stage was a bag of gasoline and firecrackers. We launched it from the back yard and time seemed to move very slowly as it headed for the house, barely clearing the roof. Fortunately, it landed in an empty road intersection.
This is one of the only channels I know that 100% deserves it’s large subscriber count. Great content, and a great host!
If that's the case, you haven't yet seen most of the best (STEM) RUclipsrs like 3Blue1Brown or PBS Spacetime
Ypu have a lot to discover then. Lucky you. Wish I was at that point.
I'm so glad that he's not the type of underrated RUclipsr that make Oscar worthy videos for 3000 views
Watch smartereveryday.
You need to watch veritasium
You’re an absolute mad lad. I can’t believe how many ideas you have for videos without watering down the quality. Everything you put out is genuinely interesting and entertaining and you make like a video a day…
In marine architecture engineering "center of buoyancy vs center of gravity " a point called "meta center" where as center of gravity must be below center of buoyancy or ship/boat capsizes .
Similar .
Excellent 👍
I think he also has a video where he mentions this actually. Pretty cool.
Yes, and boats also tend to want to turn to put the side of the boat facing the wave if you're not careful.
Pretty much the exact same principal.
@@zacrintoul below Mach 1 😂
But the center of buoyancy moves as the ship/boat rocks in the water. If the boat’s hull is vertically sloped at the waterline, yes, it will capsize. Same if the slope is negative, like on a submarine or the stealth ship.
But rowboats have a center of mass that is definitely above the center of buoyancy, and they don’t capsize because of the shape of the hull.
Think: when the rowboat is on dry land, it’s effective center of buoyancy is at ground level, definitely below the center of mass, and the hull is completely curved. Based on what you said, the rowboat should tip over under these circumstances, but it doesn’t. Because as it rocks, the center of the normal force moves.
Edit: self righting objects with round bottoms on dry land exist despite the fact that the “center of buoyancy” for objects on dry land can only be at ground level, certainly below the center of mass.
Missed an opportunity there for Kerbal Space Program 😭 e.g. to demonstrate one of the consequences of a finless rocket, with locked engines and no supporting thrusters.
Learned it the hard way, to properly fin my core stages, and boosters, when they're needed.
It's an excellent game for the channel viewers, and a bit of a shame it wasn't used here, but regardless, still a great and informative video!
Absolutely love Kerbal Space Program!
Cool, I keep hearing about kerbal, I think ill buy a copy
@@chrisfuller1268 before you buy it, beware that it is a bit more complicated than usual games. The tutorial is essentially a physics lecture and is hideously long and you would need a lot of experience along with trial and errors just to make a rocket that doesn't immediately crash.
So, it is great because it provides realism along with a real brain challenge, but not very reccomended if you are looking for something that gives instant results
Remember that KSP requires a good PC but it will barely function on laptops (yes I tried it on my laptop)
@@tejasdixit4417 or they can just go watch a few Scott Manley videos and be in orbit in no time :)
Jeeesus man 4M subscribers! I am so happy for you, when i came to the channel back in the days it was small but i was like "This guy got it"
This is such a cool practical demonstration. Congrats.
KSP helped me realize these concepts, but this feels so much more "real".
i play SFS 💀
This is one of those underrated bits of knowledge that when you have kids, you look like a genius.
Boots of knowledge are never underrated. They give +2 INT.
@@jehru5 you're absolutely right, but I usually would rather just splurge for a thinking cap
@@jehru5 lol I am 11 years old
Definitely dad-knowledge!
When I was a kid building rockets, once we found the center of gravity, we'd put a string around that spot and hold it with tape. Then we'd spin it around over our heads, letting the string out till it was a few feet. If the nose took the lead as we wanted, the center of preasure was behind the center of gravity and it was ready to fly. Just needed to repeat the test if you made any modifications to weight or shape. If you didn't, you got a quick reminder when you launched it :)
We did the same, swinging it by a string.
Be sure to have it loaded ready to fly with a new motor. It works great and is quick.
Gets much more difficult when you start trying to swing 7’ tall high power rocket around ;) but definitely a great quick and dirty test for low power rockets like the ones flown in parks
this is a great video, I teach 4H kids model rocketry and you gave me good examples of why rockets need fins and explanation of center of pressure and gravity
If you have the means, show them both fin type rockets as well as the gimballing engine types (SpaceX)....
Stewart😜
The trick to the shadow method is to account for the total fin area. The shape drawn only accounts for two fins so the tail end is slightly light causing the center of pressure to move forward. At model scales you can just eyeball an extra amount, 1/2 the length of the fin, on the end of the fin profile on each side. With the actual Estes rocket we used to add a few metal washers to the bottom of the nose cone to bring the CG really far forward.
What if the shadow was created by spinning the model and drawing the furthest points at any point in the rotation? This would also include any other deformities.
@@glenncurry3041 Imagine if you had four (or more) fins. Even rotating the model you still will only account for two fins. Since this method is to let gravity simulate the effect of wind pressure, your silhouette profile needs the total surface area (weight) of all fins to be accounted for, and in the correct lateral position along the centerline. A 4 fin rocket silhouette would have fins twice as wide as the actual model. Another way would be to cut out the correct number of fins and lay them on a finless silhouette at it's base.
@@3DPDK Interesting. I am totally new at this. It would seem there would be a quantity/ density of fins that would at some point be the same as just a bulge in the cylinder? Which compared to an ever multiplying surface area of each, would suddenly drop to just that increased girth? And that could reduce at higher air speeds as laminar flow got wider on each surface?
@@glenncurry3041 This actually works. It works with even pressure in 360°. Not so much a bulge, but more of a flare; like the bell of a horn in the tail end of the rocket. The cons are that it applies a constant resistance or drag even if the rocket is flying straight into the air stream, and at high speeds it creates a huge amount of turbulence in the exhaust stream. The problems on a model rocket is being able to make the shape without adding a lot of tail weight, as in 3D printing it, and difficulty with launch wire clearance. Both problems are solvable, but the constant drag limits rocket altitude.
When I saw the thumbnail and the title, I initially thought "ah, I already know what the rocket fins are for; for stabilisation." I was about to skip it when I thought, "wait, maybe there is something I don't know just yet" so I clicked it. I already know about the concept of airplane about how they fly, the airfoil, the CG, flaps, ailerons and other controls like Thrust Vectoring. What I didn't know is the Center of Gravity should also be applied on rockets, and the center of pressure is new to me. It's worth the click. Thanks a lot.
When I was a kid, all my weird rocket inventions didn't make it very far before spiraling. If I had this video back then, I would probably be in jail or something as a teenager 😂😂
I've always wanted to make a rocket. 38 years old and have never tried it.
Now that I'm a rocket scientist, i just might!
do it, there is quite a bit of satisfaction seeing something you designed and built take off at nearly the speed of sound and reach 10,000 feet. I did a 3" dia 6.75' long 2 stage that made it to 13,800 feet, it ran on a K-500 and a J-125. I made the electronics to fire the staging and chute ejection timer from scratch, custom built the rocket frames to handle the stresses, and it was done back in the mid 1980's ( when Tripoli had just a mere 550 members)...
Are you really a rocket scientist or engineering stuff going inside of a rocket/spacecraft? I worked at NASA for a decade designing spacecraft components, scientific instruments, training astronauts and operating instruments on-orbit and don't think I ever met a rocket scientist. I did work with a couple in defense applications, however.
@@chrisfuller1268 hello
I've learned so much from this channel
Same here
Same
Whoththo
I want more videos and explanations about this field and matters! Good one
Tf?
thanks so much... you explain everything so clearly and make everything so interesting :)
My family was really into rockets in the 70's. NOW I know why my younger self had to duck and cover a few, ahem..., more than a few times. I see Cynthia Cantrell before me had the same joys. Thanks for the memories Action Lab!
You are one of thubers that just keeps getting better. You (and team) are awesome. And you are appreciated.
9:48 Congratulations, you've now caused thousands of people to experience the Dunning-Kruger effect.
I have always been interested in rockets but the sheer maths involved in rocket science always made my head hurt. This video helped me understand the basics of design principles of rockets. Thank you very much The Action Lab, loved this video.
You should try out Kerbal Space Program if you havent played it yet.
@@xcbrr50 Thanks, I'll try that. And that's a great name you got there
Lol there's nothing called "rocket science", it's aerospace engineering. Also the math used is actually pretty simple, like 90% of the math is literally just multivariable calc and linear algebra and some ODEs and fourier analysis. That's about it really. And the mathematics is actually really fun!! There's so much good stuff on youtube to learn that math. (Dr. Trefor Bazett on youtube, you can learn the calculus and ODEs stuff. And Gilbert Strang lectures on linear algebra on youtube also buy a good book on those subjects too!) You can easily learn it mate, anyone can! don't get intimidated by it, math is actually really beautiful once you actually start learning it
the math used in aeronautics are some of the most straightforward
Brilliantly explained! Center of pressure is just like center of gravity, except that, it doesn't differentiate between regions of different mass densities, but rather depends on the cross sectional shape as seen from the direction of the wind.
The most underrated channel, every new video gives me new information.
This is the best science channel.
As a kid I used to just check model rockets by spinning them around me with a string attached at the cg outside. So basically your fan method, but without the fan. Putting a motor in is important since it’s weight in the back. You could get a rocket to take off unstable tumble then stabilize halfway through the burn and dart in a random direction from the change in cg as the fuel burns.
I always thought those were the most entertaining. And then you can track down the maker and sternly ask them why the didn't properly verify the physics before launch. Lol
This would have been useful back when I started KSP. That and knowing about struts.
As a kid, I had a model rocket that would never fly right, it'd just spin around in circles, and I couldn't figure out how to modify it to get it to work. I think this is why! Thanks for helping solve a decades-old personal mystery!
It's not just rockets you can see it with arrows as well 👍
Just what I thought!
So do fish. Their dorsal and top fins help them keep balance and swim forward, even against strong water currents.
Without these fins, the fish will just propel in any direction that the local water current is in.
Darts too?
@@0neIntangible darts are some kind of arrows, so yes
yeah, thats why all the twigs that i shot used to go sideways :(
A good video, as always. One small point is like to mention though it's that when a coiled spring is compressed or stretched it will impart a rotational force on each end. In many of the better racing cars they have a flat bearing under the coil springs so that the lateral force created by the compressing spring doesn't try to bend the damper shaft, and so create more friction.
I've played enough Kerbal Space Program to know where this is going
This makes me appreciate the complexity of rocket science even more now. Watching this I kept thinking about rockets with liquid fuel tanks and how as it’s used, there is a constant shift in weight distribution.
By coincidence, i had a talk with someone this morning about the history of aircrafts and how design could be related to the anatomy of birds. At a moment we were talking about the concorde plane and It's positioning of the wings. I understood the stability by referring to how a trailer can be loaded so you have a stabile path when pulled by a truck at higher speed. Dependent on where the center of gravity is relative to the area where the wheels make contact and carry the load. I was kind of thinking afterwards if the analogy was fully relevant, tbh because of the axial pivoting dynamic in between and difference of pull versus push. After seeing this video, i think i can understand this modelling and placing of wings even better in a isostatic solid body model. Thank you for your video's. They have a certain degree of diy integrity and innocence that reminds me of when i was young and did all kinds of tests and small maquettes because of some facets that the facination of mobility in life brings.
I'm officially a rocket scientist now! Thanks for the certification. See you at the launch 👋
Scientist: *Fins don't affect rocket at all. It's just a decoration.*
100 years later, The Rocket Fish: *Fins go brrr.*
Whats brrr?
@@yerri5567 It's a meme
@@prich0382 What does brrr in the meme mean?
@@yerri5567 So you know the A10 Warthog? It's got a Gatling gun basically that goes *brrrt?* Well take that concept that apply it to other fast things, like money printer go *brrrrr* which I think is the original or whatever fast occuring things
@@prich0382 Ahhh okok thanks!
Ah yes CG > CP for positive stability... fond memories of the classic Handbook of Model Rocketry by G H Stine; still available today in 7th edition!
"It's not pointy enough.
You need to make it pointier." Duh!!! 🤣
This is your best one !
Also this shadow method is brilliant, it's converting effective surface area of 3d object into 2D information
Got a beginner model rocketry kit when I was about 12. Spent a week or so putting together my first rocket. It wasn't the prettiest but it was technically and mechanically correct.
It was basically a bottle rocket with a parachute.
My dad and I went out into the pasture away from any buildings and set up the launch pad. We made sure the sun was behind us and got back a safe ways. Then came the launch.
We did the traditional countdown together as I flipped the saftey and hit the ignition. Fire blasted out the bottom and she took off into the sky.
Up, up, up she went.
And kept going.
And kept going.
And she never seemed to return.
We saw no chute deployment, no explosion, no fiery falling shell, nothing. It simply went up and stopped existing, for all we knew and still know to this day.
We searched the neighbors' fields downwind, we searched in directions it couldn't have gone. We searched for a couple days until my dad gave up; then I kept searching for a couple more. We never found any trace of it.
30+yrs later, I still wonder about that rocket...
Now im gonna apply for a job and say this guy made me an official rocket scientist
With the advent of computer guidance systems that function at correcting directions thousands of times a second, tailfins may no longer be necessary but, the costs involved make it virtually impossible for fins to ever completely go away.
As a kid in the 70s I once accidentally lit a hill on fire by seeing what would happen if I ignited a little Estes rocket without the fins attached.
Lesson learned the hard for sure.
Great video! Minor point, but air resistance, or drag, is partially a function of medium density, velocity, and cross sectional area. I believe maximizing cross sectional area actually increases the drag, but your second reason for pressure stability is great. Maximal cross sectional area also maximizes volume/load and decreases costs for wall materials.
Think about the drag on a sheet of paper traveling laterally (i.e. as a magic carpet). It will exhibit negligible drag. But it also won't be able to carry anything as it has virtually no volume.
I think the cross sectional area is fixed, as you need to carry a certain amount of fuel. then the drag would be smallest for a cylinder, as less perimeter means less contact with the air around it 😅
But I agree, could've been said more clearly... Like a circle minimizes the perimeter for a fixed area, not that it maximizes the are for a fixed perimeter...
Kites and center of pressure would be a good video.
Better Help sounds excellent really… many just need someone to listen to them. Personally I have gained mental awareness by Painting, but only after wrestling with light with pencil and some of the loveliest paper from Italy…Fabriano…the oldest paper company.
I remember a couple of Estes rockets that were called 'tumblers'. Instead of a parachute, the charge that would normally blow the nosecone off just caused the spent engine cartridge 'aft' a few inches. This resulted in the center of gravity shifting aft, past the center of pressure. So on the flight up with the engine forward, it was stable and launched straight up. After burn out the engine shifted aft and the rocket was unstable. So it tumbled around and around as it fell, this limited it's terminal velocity so when it landed in the grass, it was undamaged.
and the fun thing about it all... the CG moves forward as the motor burns making the rocket even more stable... so, when doing the CG testing, do it with the motor you plan to use or else the CG may be behind the CP and once it comes off of the rod it will go wacky...
When he said let's start it off straight I laughed 🤣
This was super interesting. Great episode!
You've outdone yourself once again. Peak pedagogy !
The consistent uploads with incredible quality is admirable, I love this channel so much
The same principle can be applied to keep trailers from swaying. If the center of gravity is behind the trailer's axle, it will sway when you pull it. The axles are where the upward force is applied to lift the trailer so it acts like a center of pressure.
Interesting. I was just wondering if that trailer stability situation was related, and it is!
Much easier and faster way to find the center of gravity: balance the object on 2 fingers or 2 sticks or something and move those 2 fingers/things towards each other. Where they meet is your center of gravity.
that can only be done on simple surfaces, like the most famous one, the pencil. however when the mass is unbalanced (ex. you put one of those eraser attachments onto one side) you can't really gauge the total mass and thus also the center of gravity unless you balance it further out onto the "attachment." by concept it just might work cuz it sounds logical but practical applications are of course more complex. i'm not a physicist or something btw, just a regular worker who's fascinated by how things get easier if you understand them more lol
@@runic6452 Actually it does work even with unbalanced masses! Try it with a broom, that is quite obvious unbalanced, and you will see it works there, too. The point at which it fails is quite obviously when the surface you are balancing it on changes, e.g. when the center of gravity is somewhere where the fins of the rocket are attached. But for the examples in this video it would have worked perfectly.
As a Besiege player, this is definitely a video I want.
reminded me of my fluid mechanics classes with so many problems on centre of gravity and centre of pressure for ships especially
"Now let's turn on our fan and see what it looks like."
*Wile E. Coyote loved that.*
The pointy head is the most important!
Another cool experiment shows how a rocket's roll about its vertical axis can be induced by coordinating the other two axes. Hold a coat by its neck and move your hand in a circle. If you move your hand in a clockwise circle, the coat tries to twist clockwise and vice versa. This is why controls for only two axes are sufficient to orient a rocket in 3D.
"Largest area vs perimeter -> least air resistance" kinda the opposite, that gives the greatest air resistance for given perimeter, so that's disadvantage. BUT. What largest area takes as disadvantage, it gives as advantage in the way that it allows for largest volume for given material (if we're talking cylinder-like shapes, or else sphere is the largest volume).
It'll be great if Kerbal Space Program use this video to explain center of mass and pressure!
Who would have known that a Pringle's can would become rocket science.... love these experiments and explanations. 👍😁
Tom 😎
ngl I understood this at the beginning of the video.
But this is just excellent explanation
3 basic properties of a craft needed to be regulated are Center of Mass, Center of Lift and Center of Thrust
The ancient Chinese rocket design with just a stick 7x the length of the motor could be an interesting test. In high school, sometimes I'd take a model rocket motor and just tape a long stick to it like a bottle rocket, not the best or most efficient, but flew surprisingly straight. There are modern firework rockets with this design and usually a cone on the top.
Never thought I might say I'm a rocket scientist!
This was far more interesting than I expected. But now I'm filled with questions! The sideways-in-the-wind aspect is surprisingly crystal-clear; Why, then, don't they, say, have two thrusters, one at each end, and redirected at a 90degree angle...? If it wants to fly sideways, why force otherwise? And that center of pressure method seems confusing; What would happen if the tailfins were replaced by a cone?
If you try to fly with thrust on both ends, the rocket will break at the middle. It's like a soda or beer can after it's empty, to crush it top to bottom requires some strength to make the sides collapse. But press on an empty can from the sides, and it folds easily.
You want rockets to be light for performance, if you make the sides thick enough to not get damaged, the rocket will be very heavy.
@@ChucksSEADnDEAD Oh, interesting! That's a good way to explain it, too, crushing a can.
Not only that but the wind pressure would now be quite a bit higher as well, since the long side will naturally want to face the oncoming pressure.
People who played Kerbal Space Program before:
I'm kind of a rocket scientist myself
Another banger video I can watch with younger cousins
More videos like this please!
Love the channel! Big fan! Now criticism: The cylinder - fan experiment is not precise as the fan is already blowing air before the cylinder is suspended. The cylinder could very well move sideways even without the air flow in the perspective of us audiences. Somewhat more scientific approach would be to first ensure that the cylindrical body is stationary in suspension without any air draft. The conclusions drawn in the video, therefore, could have been wrong. (It certainly isn't wrong though.)
"You're now all officially rocket scientists."
Until gimbles and finless rockets, the science was as old as arrow fletching.
Awesome video. Now that you've covered fin stabilized rockets, it'd be cool to see the physics behind a venturi stabilized rocket.
0:48 Man, I didn't realize you had access to such a high-tech windtunnel
Thank you for the explanation, that was a very impressive demonstration. Now I'm sure I can build better rockets in KSP.
**Kerbal Space Program players gained no new knowledge from this video**
Putting rocket scientist in my resume. I don't know why people say it's hard.
Great video. I enjoyed this👍🏾
Wow you explain things so well!
Thanks for having an awesome channel
Technically extending the rocket body would shift the center of pressure forward more than the center of gravity. Aka making it less stable. This is especially the case since your motor and motor mount is in the back. Usually little model rockets just have a parachute in the front.
I needed this so much to continue developing my ICBM! Now only if you could make another video on how warheads work...
I learned something! Thank you for making me a rocket scientist.
This was super useful and entertaining!! Thanks for the video
"you're all now officially rocker scientist"
Me: where do I get my diploma?
Great, thanks for sharing this valuable info
Another way to test for stability, tie a string to it at CG with loaded motor, swing it in a circle around you, if it flies straight, it will fly fine.
I always find you videos really interesting and easy to understand. This video helped me with a recent model rocket project. Thanks!
I am learning a lot from his videos
"I'm not a rocket scientist, I rock the house and sign the t*ts, and that's it" - Teddybears STHLM
That's exactly what people should watch today instead of TikTok and Instagram sh*t.
Thanks a lot for making those videos!!! I've learned more from a single 10 minutes video than from my entire time in school 👍
Sorry for my English.
Or folks shud watch what they enjoy and folks shud just not be all judgmental about it.
I know many a science educator makin tiktoks that get many millions of views. Your premise is based on a falsehood you assume from your limited worldview.
@@SylviaRustyFae I'm not talking about scientists that make TikTok or Instagram education videos. I'm talking about the other 99% of the content and content makers that you can find there.
And hey, look around you and think a bit before you write anything. Most of the people today (especially teenagers) are using TikTok and Instagram or whatever just to spend their time but they learn nothing while doing it because most of them are watching the sh*t content of it.
I'm not judging anyone because I don't really care about what anyone watches and shares there, I'm just saying that it could be better to teach people and children to do something useful that could make them smarter and better (like watching videos like this here) and not spend their time on crapcontent.
So the next time you comment just think a bit and look at the facts.
@@davidsuris9318 Ok Boomer
@@SylviaRustyFae And that's called degeneration. The action lab could make a video about trying to explain your IQ. I don't see any reason to fall to your level and to continue this conversation so have a nice day.
KSP taught me two things:
1. Put CoP/CoL behind CoG/CoM.
2. If not, just put on some engines with a lot of gimbal range haha.
The title of this video feels like a threat. 10/10 I like it
RIP TKoR, action lab is the successor we needed
I’m pretty sure I’m a rocket scientist now. Putting it on my resume.
That was much more interesting than I thought it was going to be.
Amazingly explained. Love from 🇮🇳
This is a really good explanation of a complex topic like rocket science, I love it
It’s not just rockets that use these flight principles, ‘Arrows’ also use their fletchings for flight stabilization.
This has to be the best science channel on youtube
Center of pressure
Fluid mechanics
Need more videos on Bernoulli's principal and different energy heads❤
Right moment for making rocket physics
Funny that when the centre of gravity and pressure are at the same spot, when it is just a tube, it still turns seemingly to maximize its drag. You'd think it would turn to minimise the drag if anything.
It helps to imagine the rocket pivoting around its center of gravity, AKA center of mass, while the air pressure pulls downward from the center of pressure.