ErgionThorn Posted December 11, 2016 Author Share Posted December 11, 2016 10 minutes ago, foamyesque said: Almost everything you say is the result of aerodynamics and occurs to actual planes and rockets that screw up their designs IRL. nope, it wont happen irl... try it with a model plane. you can experience it first hand 1 minute ago, DD_bwest said: yea yu arent flying right for a proper aerodymanic model. going up 7km then turning is going to produce a massive amount of aerodymanic pressure pushing on the sides of your rocket, making it flip. also, you need to make it more stable by moving weight to the front. which is not true, firstly, on a thing being pushed you want the weight on its rear to have the com closer to the trust so there is a smaller arm and imperfections will move the craft out the least... its the opposite of having a freeflying or pulled object where you want the weight on its front, secondly, when you are slightly turning in atmosphere there is nothing like massive pushing on the sides of the rocket, there is actually barely any sideway pressure unless you are turning in big angles. try it, push your finger into butter and try suddenly turn it while its still moving. it wont break your finger, actually it will smoothen the turn. the very same thing is happening in the air because the atmospheric pressure is applied at EVERY single point of the craft... Link to comment Share on other sites More sharing options...
foamyesque Posted December 11, 2016 Share Posted December 11, 2016 You have how center of mass interacts with rockets exactly backwards and it explains all your problems. Link to comment Share on other sites More sharing options...
DD_bwest Posted December 11, 2016 Share Posted December 11, 2016 8 minutes ago, ErgionThorn said: which is not true, firstly, on a thing being pushed you want the weight on its rear to have the com closer to the trust so there is a smaller arm and imperfections will move the craft out the least... its the opposite of having a freeflying or pulled object where you want the weight on its front, secondly, when you are slightly turning in atmosphere there is nothing like massive pushing on the sides of the rocket, there is actually barely any sideway pressure unless you are turning in big angles. try it, push your finger into butter and try suddenly turn it while its still moving. it wont break your finger, actually it will smoothen the turn. the very same thing is happening in the air because the atmospheric pressure is applied at EVERY single point of the craft... no you want weight at the front. if your front it so light and draggy it will flip everytime, its simple physics. it may be counter intuitive, but its still simple. done right you can actually make a vessel that puts itself into orbit without any turn. if youwant there are some experiments at home that you can do. fill 2 2l bottles 1/5th of the way with plaster, one upsideown, one up right. then try to ballance them on the lid on 2 fingers and see which is easier to keep upright and if you go up 7km, you will get going quickly, at which point you will have almosphere pushing the side of your rocket. go take a papertowel tube and hold it out a window while you drive, turn it against the wind for a second. that is what you are trying to do. we are trying to help you and tell you what you are doing wrong. if you want to be stuborn, you can. but dont expect the world to change the laws of physics because you dont understand it Link to comment Share on other sites More sharing options...
W. Kerman Posted December 11, 2016 Share Posted December 11, 2016 Wow. I haven't see a thread with this much moderator intervention since the "KSP console version is awful!" one! Link to comment Share on other sites More sharing options...
Rhomphaia Posted December 11, 2016 Share Posted December 11, 2016 1 hour ago, ErgionThorn said: one thing anybody can try even with stock planes. choose a bigger, heavier one with front winglets. take off, keep flying straight, when its stable just touch the down pitch, then the up pitch (obviously with keyboard, i dont have joy but it should work with keyboards too) simulating like doing little corrections in elevation. what should happen is that when you pitch up or down, the plane slightly change direction up or down. instead in ksp its like hitting the top or bottom of the plane with a huge hammer, it raise its nose suddenly then dropping back and if its a big enough plane it will start swinging up and down... i dont even need to make a video of this, im 100% sure it works like this for everybody. This is not a problem with Physics or Aerodynamics, but rather the issue is the digital nature of keyboard controls, when you tap the keys You are not simulating little corrections, you are in fact slamming your control surfaces momentarily to maximum deflection. Try turning on fine control (capslock) Link to comment Share on other sites More sharing options...
Starman4308 Posted December 11, 2016 Share Posted December 11, 2016 1 hour ago, ErgionThorn said: those rockets should fly like arrows just because of their huge momentum... Yes. And they do. When your rocket flips out and becomes debris, you will notice they still have a great deal of upwards momentum; that hasn't changed. What your rocket doesn't have is angular/rotational momentum; as a rocket is flying straight and true, it literally has zero angular momentum (relative to CoM) to resist torques. When your rocket flips out, it is because aerodynamic forces are exerting a torque on your rocket that exceeds its control authority. There are two primary mechanisms to address this: aerodynamic stability and spin-stabilization. For aerodynamic stability: by having more cross-sectional area to the rear of your craft, aerodynamics tends to exert a torque which resists any deviation from your current velocity vector. You can think of drag as pulling at your aircraft, at the center of drag, in the direction opposite your current velocity. With CoL (approximately the center of drag) behind CoM, this balances things, with CoL in front of CoM, it makes it aerodynamically unstable and flip-happy. One way to visualize that; imagine center of lift and center of mass as being the two ends of a rod. With CoL behind CoM, aerodynamics are pulling CoL behind CoM, keeping the rod sraight. With CoL in front, aerodynamic forces are pushing at the rod, and it's now a balancing act, where any slight deviation from straight will amplify itself. The other method is spin-stabilization. You know how I said a rocket flying straight and true has no angular momentum? A rocket flying straight, true, and spinning has lots of angular momentum, which will naturally resist torques (up to a limit, of course). Link to comment Share on other sites More sharing options...
DD_bwest Posted December 11, 2016 Share Posted December 11, 2016 7 minutes ago, Starman4308 said: Yes. And they do. When your rocket flips out and becomes debris, you will notice they still have a great deal of upwards momentum; that hasn't changed. What your rocket doesn't have is angular/rotational momentum; as a rocket is flying straight and true, it literally has zero angular momentum (relative to CoM) to resist torques. When your rocket flips out, it is because aerodynamic forces are exerting a torque on your rocket that exceeds its control authority. There are two primary mechanisms to address this: aerodynamic stability and spin-stabilization. For aerodynamic stability: by having more cross-sectional area to the rear of your craft, aerodynamics tends to exert a torque which resists any deviation from your current velocity vector. You can think of drag as pulling at your aircraft, at the center of drag, in the direction opposite your current velocity. With CoL (approximately the center of drag) behind CoM, this balances things, with CoL in front of CoM, it makes it aerodynamically unstable and flip-happy. One way to visualize that; imagine center of lift and center of mass as being the two ends of a rod. With CoL behind CoM, aerodynamics are pulling CoL behind CoM, keeping the rod sraight. With CoL in front, aerodynamic forces are pushing at the rod, and it's now a balancing act, where any slight deviation from straight will amplify itself. The other method is spin-stabilization. You know how I said a rocket flying straight and true has no angular momentum? A rocket flying straight, true, and spinning has lots of angular momentum, which will naturally resist torques (up to a limit, of course). Thanx, you explained that a lot better then I could have. Im not so great at finding the right words lol Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 11, 2016 Author Share Posted December 11, 2016 (edited) 1 hour ago, foamyesque said: You have how center of mass interacts with rockets exactly backwards and it explains all your problems. nope, you have it backwards... 1 hour ago, DD_bwest said: if your front it so light and draggy it will flip everytime if its draggy, but rockets tend to be not draggy, they are pointy and their tail is draggy... thats how rockets are designed. 48 minutes ago, Rhomphaia said: This is not a problem with Physics or Aerodynamics, but rather the issue is the digital nature of keyboard controls, when you tap the keys yeas, i know thats what i was saying too, capslock doesnt really help, it just makes the slam smaller though with proper modelling forces could be applied based on a parabolic curve like force = deltatime^2 so the longer you hold the key the higher the force applied, obviously maxed at the strength of the original force. would solve lots of issues with keyboard controls. also, its still an issue with physics as it shouldnt bob back down, it should just harshly turn upward... 15 minutes ago, DD_bwest said: With CoL (approximately the center of drag) behind CoM, this balances things, with CoL in front of CoM, nobody said com should be behind col, its obviously flipping a craft but col should be far around the rear of the craft while com should be behind the geometric center as close to the rear but in front of the col, if you want i will make a sketch up for you.. if you put the weight on the top of the rocket it will make the pushing force tripping over the craft. what is your mistake is that aerodynamics doesnt care of com, it has things to do with the thrust, aerodynamics cares of col and the geometric center of all the surfaces affected... rear drag and front weight does only matter for object freeflying and not if they are being pushed. anyway, just check the stock rockets, there is one with an orange tank and carries i think just a small fuel tank in the bay...its top is light, its rear is heavy, com is behind the center and it flies very well... so what are we even talking about? the best proofs are the simple stock crafts Edited December 11, 2016 by ErgionThorn Link to comment Share on other sites More sharing options...
Starman4308 Posted December 12, 2016 Share Posted December 12, 2016 (edited) 20 minutes ago, ErgionThorn said: nope, you have it backwards... if its draggy, but rockets tend to be not draggy, they are pointy and their tail is draggy... thats how rockets are designed. yeas, i know thats what i was saying too, capslock doesnt really help, it just makes the slam smaller though with proper modelling forces could be applied based on a parabolic curve like force = deltatime^2 so the longer you hold the key the higher the force applied, obviously maxed at the strength of the original force. would solve lots of issues with keyboard controls. also, its still an issue with physics as it shouldnt bob back down, it should just harshly turn upward... nobody said com should be behind col, its obviously flipping a craft but col should be far around the rear of the craft while com should be behind the geometric center as close to the rear but in front of the col, if you want i will make a sketch up for you.. if you put the weight on the top of the rocket it will make the pushing force tripping over the craft. what is your mistake is that aerodynamics doesnt care of com, it has things to do with the thrust, aerodynamics cares of col and the geometric center of all the surfaces affected... rear drag and front weight does only matter for object freeflying and not if they are being pushed. anyway, just check the stock rockets, there is one with an orange tank and carries i think just a small fuel tank in the bay...its top is light, its rear is heavy, com is behind the center and it flies very well... so what are we even talking about? the best proofs are the simple stock crafts "Geometric center", whatever you mean by that, has nothing whatsoever to do with aerodynamic stability. All that matters is if CoL is behind CoM and your vehicle isn't too far off straight flight. You must also account for changes in CoM as the flight progresses; if you are draining from a tank above CoM, that's naturally going to drag the CoM downwards. Usually it's not a huge deal for rockets, but it's important for aircraft. CoM being up at the top just makes it even more stable (assuming CoL is towards the bottom); that causes the lever arm of aerodynamic stability to be that much longer, producing an even larger torque towards the flight vector. That would even improve control authority provided by gimballed engines, assuming they're radially symmetric. Of course, too much control authority creates a twitchy craft that tends to overcorrect. Edited December 12, 2016 by Starman4308 Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 12, 2016 Author Share Posted December 12, 2016 (edited) 6 minutes ago, Starman4308 said: "Geometric center", whatever you mean by that, has nothing whatsoever to do with aerodynamic stability. All that matters is if CoL is behind CoM and your vehicle isn't too far off straight flight. You must also account for changes in CoM as the flight progresses; if you are draining from a tank above CoM, that's naturally going to drag the CoM downwards. Usually it's not a huge deal for rockets, but it's important for aircraft. CoM being up at the top just makes it even more stable (assuming CoL is towards the bottom); that causes the lever arm of aerodynamic stability to be that much longer, producing an even larger torque towards the flight vector. That would even improve control authority provided by gimballed engines, assuming they're radially symmetric. nope, you are totally wrong, sry. in aerodynamics, com doesnt matter, its the surfaces that matter. the most weight at the top will make the craft trip over... the lever of arm what you are talking about, again, only matters of free flying objects like an arrow that is shot and flies away being dragged by the weight of the arrowhead, its not the case with rockets that has a continuous force pushing from the rear... in that case the lever of arm between the com and the thrust is DE-stabilizing the craft. anyway, instead of just posting and posting, did you take your time to check the stock craft i was mentioning? and why is that nobody build rockets with the orange tanks at the top and the pod on the bottom? it would be possible. on irl rockets why the cargo is on the top while those ar mostly just lightweight satellites and the lots of fuel and rockets are at the bottom? cmon, it dont even need physics knowledge just common sense Edited December 12, 2016 by ErgionThorn Link to comment Share on other sites More sharing options...
foamyesque Posted December 12, 2016 Share Posted December 12, 2016 22 minutes ago, ErgionThorn said: if you put the weight on the top of the rocket it will make the pushing force tripping over the craft. what is your mistake is that aerodynamics doesnt care of com, it has things to do with the thrust, aerodynamics cares of col and the geometric center of all the surfaces affected... rear drag and front weight does only matter for object freeflying and not if they are being pushed. Everything you said in here is wrong, man. Pushed, pulled, or free-flying, aerodynamics cares about CoM relative to CoL, and neither cares about the geometric center of anything. You're trying to shoot arrows backwards and wondering why it doesn't work, and you're further handicapping yourself by wrecking the ability of your control surfaces to correct by reducing their lever arms. Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 12, 2016 Author Share Posted December 12, 2016 (edited) 1 minute ago, foamyesque said: Everything you said in here is wrong, man. Pushed, pulled, or free-flying, aerodynamics cares about CoM relative to CoL, and neither cares about the geometric center of anything. You're trying to shoot arrows backwards and wondering why it doesn't work, and you're further handicapping yourself by wrecking the ability of your control surfaces to correct by reducing their lever arms. nope.. its again not true, GO CHECK THAT CRAP CRAFT INGAME!!! instead of coming back with pointless post... "You're trying to shoot arrows backwards and wondering why it doesn't work" omfg, can you even... argh? what did i say? " the lever of arm what you are talking about, again, only matters of free flying objects like an arrow that is shot and flies away being dragged by the weight of the arrowhead " so i agree that the weight on top does matter for the arrow what is your answer? " You're trying to shoot arrows backwards and wondering why it doesn't work" and some are wondering why ppl lose their temper... Edited December 12, 2016 by ErgionThorn Link to comment Share on other sites More sharing options...
DD_bwest Posted December 12, 2016 Share Posted December 12, 2016 24 minutes ago, ErgionThorn said: anyway, just check the stock rockets, there is one with an orange tank and carries i think just a small fuel tank in the bay...its top is light, its rear is heavy, com is behind the center and it flies very well... so what are we even talking about? the best proofs are the simple stock crafts take the same rocket, break the orange tank into 4 smaller ones, and use fuel priorities to drain from the bottom up and it will fly even better. Link to comment Share on other sites More sharing options...
Starman4308 Posted December 12, 2016 Share Posted December 12, 2016 (edited) Ergion, I will ask a question. Who here has sent rocket after rocket after rocket after rocket into space successfully without a hitch? Who here seems to be having difficulty getting one into space without first effectively leaving atmosphere? I would postulate here that the people who have sent rocket after rocket after rocket after rocket might have a slightly better grasp on aerodynamics. Also, the point of having engines a long way away from CoM: if everything is radially symmetric, all the torques cancel out, and if you're gimbaling the engine, you want it to be temporarily unstable, you want a net torque. Edited December 12, 2016 by Starman4308 Link to comment Share on other sites More sharing options...
foamyesque Posted December 12, 2016 Share Posted December 12, 2016 (edited) 8 minutes ago, ErgionThorn said: nope.. its again not true, GO CHECK THAT CRAP CRAFT INGAME!!! instead of coming back with pointless post... It is, in fact, still true. I mean, you could keep on not believing me and continue to make rockets that don't fly, then blame it on the game, that's your choice, but I'm trying to help you. It would also be helpful if you were to provide a name of the rocket you want me to look at. EDIT: 7 minutes ago, ErgionThorn said: what did i say? " the lever of arm what you are talking about, again, only matters of free flying objects like an arrow that is shot and flies away being dragged by the weight of the arrowhead " so i agree that the weight on top does matter for the arrow Yes, see, you're wrong. It matters for everything. Like I said, when I told you you were wrong. And like I'm telling you now, when I'm telling you you're wrong, again. Edited December 12, 2016 by foamyesque Link to comment Share on other sites More sharing options...
panzer1b Posted December 12, 2016 Share Posted December 12, 2016 Guys, i think we need to stop feeding the troll. Normally id consider a person not understanding something to be new or whatnot, but im pretty damn sure its just a troll that is trying to cause a flame war on here. Constantly disagreeing with people is not a productive discussion nor does that actually make the OP look any less like a troll... Please, just STOP and think everyone, and dont feed the troll any more then you are legally required by the laws of your planet of origin. Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 12, 2016 Author Share Posted December 12, 2016 3 minutes ago, DD_bwest said: take the same rocket, break the orange tank into 4 smaller ones, and use fuel priorities to drain from the bottom up and it will fly even better. nope, it will not fly better, it will fly worse. just try it. 2 minutes ago, Starman4308 said: Ergion, I will ask a question. Who here has sent rocket after rocket after rocket after rocket into space successfully without a hitch? Who here seems to be having difficulty getting one into space without first effectively leaving atmosphere? I would postulate here that the people who have sent rocket after rocket after rocket after rocket might have a slightly better grasp on aerodynamics. poor try, ive sent many many many rockets, ive been everywhere in kerbol, i have over 400 hours in the game simply i dont push my head into sand when i see an issue.. just because you can send up rockets and dont even notice the issues doesnt mean you have better understanding on aerodynamics. Link to comment Share on other sites More sharing options...
foamyesque Posted December 12, 2016 Share Posted December 12, 2016 Just now, ErgionThorn said: nope, it will not fly better, it will fly worse. just try it. poor try, ive sent many many many rockets, ive been everywhere in kerbol, i have over 400 hours in the game simply i dont push my head into sand when i see an issue.. just because you can send up rockets and dont even notice the issues doesnt mean you have better understanding on aerodynamics. I bet your dad works for Nintendo, too. Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 12, 2016 Author Share Posted December 12, 2016 Just now, foamyesque said: I bet your dad works for Nintendo, too. well, even if he would, how would that fit into this topic? Link to comment Share on other sites More sharing options...
Starman4308 Posted December 12, 2016 Share Posted December 12, 2016 Just now, ErgionThorn said: poor try, ive sent many many many rockets, ive been everywhere in kerbol, i have over 400 hours in the game simply i dont push my head into sand when i see an issue.. just because you can send up rockets and dont even notice the issues doesnt mean you have better understanding on aerodynamics. Assuming you are posting in good faith: calm down, step away from the computer, and take a break. It's easy to get too wound up. Come back with a more open mind, and look into aerodynamics more. I am now tempted, however, to suspect Panzer is right, and that you are not, as point of fact, posting in good faith, in which case I'll simply point out that I have thousands of hours played. Link to comment Share on other sites More sharing options...
foamyesque Posted December 12, 2016 Share Posted December 12, 2016 (edited) 1 minute ago, ErgionThorn said: well, even if he would, how would that fit into this topic? I'm saying I don't believe you. Put your money where your mouth is and let's see some screenshots or craft files to back this up. Edited December 12, 2016 by foamyesque Link to comment Share on other sites More sharing options...
panzer1b Posted December 12, 2016 Share Posted December 12, 2016 Just now, foamyesque said: I'm saying I don't believe you. Put your money where your mouth is and let's see some screenshots or craft files to back this up. Its quite possible this guy doesnt even own KSP for all we know, everything this guy has been saying seems to be more or less trolling and flame baiting... Anyways, im out for today, no idea why the hell im actually contributing to a troll thread ... Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 12, 2016 Author Share Posted December 12, 2016 Just now, Starman4308 said: Assuming you are posting in good faith: calm down, step away from the computer, and take a break. It's easy to get too wound up. Come back with a more open mind, and look into aerodynamics more. I am now tempted, however, to suspect Panzer is right, and that you are not, as point of fact, posting in good faith, in which case I'll simply point out that I have thousands of hours played. im completely calm drawing sketch for you Just now, foamyesque said: I'm saying I don't believe you. nobody cares really, im not here to convince you Link to comment Share on other sites More sharing options...
DD_bwest Posted December 12, 2016 Share Posted December 12, 2016 it will fly better. ive 3000 hours, 50+ careers. everyone here knows it, Scott manley knows it. i strogly suggest you do the expirements i suggested. 2l bottles. one with plaster at the top, one with it at the bottom and balance each one on their caps on 2 fingers. Link to comment Share on other sites More sharing options...
ErgionThorn Posted December 12, 2016 Author Share Posted December 12, 2016 here you go, this is how physics work 2 minutes ago, DD_bwest said: it will fly better. ive 3000 hours, 50+ careers. everyone here knows it, Scott manley knows it. i strogly suggest you do the expirements i suggested. 2l bottles. one with plaster at the top, one with it at the bottom and balance each one on their caps on 2 fingers. you still dont understand the difference between the pushed and pulled objects, they are completely different... i will give it a last try: do you realise the difference between them? first one is a fighter jet. has big heavy rear light pointy nose... its being pushed from its rear the second one is an old biplane, it has big heavy nose and nearly weightless rear only with the fin and wings there... whoaaahh, its being pulled. simple physics... Link to comment Share on other sites More sharing options...
Recommended Posts