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  • Arduino Powered Rocket Guidance System

    I would have done things a little bit differently. I would have used plywood for the centering rings as opposed to cardboard. The cardboard will either a. rip under the strain of the launch, or ignite when the ejection charge goes off. Speaking of ejection charge, it is generally considered bad practice and even illegal in some areas and launch sites to launch without a recovery system. 4 servos would be enough here, and the ones you have are massively overkill. as far as electronics go, you don't need the breadboard at all, and you could use a much smaller arduino to control the servos. I would have secured the motors with CA glue as opposed to zip ties, and the electronics would go higher. Remember, for a rocket to be passively stable it's center of aerodynamic pressure needs to be at...see more »I would have done things a little bit differently. I would have used plywood for the centering rings as opposed to cardboard. The cardboard will either a. rip under the strain of the launch, or ignite when the ejection charge goes off. Speaking of ejection charge, it is generally considered bad practice and even illegal in some areas and launch sites to launch without a recovery system. 4 servos would be enough here, and the ones you have are massively overkill. as far as electronics go, you don't need the breadboard at all, and you could use a much smaller arduino to control the servos. I would have secured the motors with CA glue as opposed to zip ties, and the electronics would go higher. Remember, for a rocket to be passively stable it's center of aerodynamic pressure needs to be at least on caliber (diameter of the sustainer's body tube) lower than the center of mass. The center of mass is right about at the back of this rocket, so it probably won't be passively stable. This means that as the nose deviates from the velocity vector, it will tend to increase deviation as opposed to correct it. Even the arduino would have trouble correcting for this with the fins. Also, keep in mind that model rockets are supposed to have thrust-weight ratios of at least 4:1 or else they won't come off of the rod/rail/tower cleanly. With a rocket of this weight, you would have to be flying it on something like an H or I-class motor, which are illegal to own if you don't have your L1, Jr L1, or are planning on using it for your qualifying flight. Whatever body tube material that you are using probably isn't strong enough to contain the 300 Newton seconds of force that the motor would put on the rocket. The electronics all piled up against one side would make sure that the CoM isn't in line with the thrust vector, and not mounting them means that when the rocket launches, they will shift around, changing the CoM in flight, something which generally causes Catastrophic Failures.

    If you want your rocket to go straight up, just tilt the fins 2 or 3 degrees, or sand them with asymmetric aerofoils. No need for all this arduino shenanigans. These servos don't have the minute control authority to turn the rocket slightly, especially over mach 1.

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