The rocket aerodynamic configuration does not change as fuel is burned so the CP stays the same, but the rocket's CG does change. For a rocket using a solid fuel rocket motor, the CG generally shifts forward as the rocket motor gets lighter. This tends to increase the stability since the CG moves farther away from the CP. As the air thins as the rocket ascends the fin lift tends to decrease and the rocket becomes less stable.

​@@labratscientific1127ok great, thanks for the clarification.

This is a terrible take. The first 5 minutes are spent demonstrating that people's knowledge isn't flawed, but rather air can act in different ways in different circumstances. He caps it off by stating that in open circumstances pressure and velocity can adjust to allow density to remain constant, therefore incompressible. Conservation of mass absolutely is applicable to lift generation, as an airfoil relies on it to generate differential velocities and therefore pressures on the upper and lower surfaces, which is the basic principle behind lift generation. I'd genuinely recommend taking another watch, this video is significantly better at explaining the principle, supported by experimentation, than any of my previous education.

​@@Polypythat You do yourself no favours by being an apologist for this nonsense. Conservation of mass in an ideal fluid, (incompressible, inviscid etc.) led Bernoulli to his now famous but poorly interpreted principle. Bernoulli's principle states that in a moving fluid, (and he only worked with water) a change in flow rate is always associated with a pressure change. What the principle doesn't say is that a change in pressure in air (the highly compressible form of a fluid) is always associated with a change in flow rate. A change in pressure in air can be associated with a change in flow rate, but a change in pressure in air can also be associated with a change in volume (by evacuation or compression) or a change in temperature. It's a case of A always results in B but B is not always associated with A. All dogs are animals, but not all animals are dogs. A change of pressure in air does not have to be associated with momentum, velocity or acceleration: think about your tyre pump. Think about heating a container.

Oooo that's a good question

This will depend on the materials you use (as well as how you connect your members together). A given material will have a tension member capacity and a compression member capacity -- these known values tell you how much force, in tension or compression respectively, a member can sustain before failure.

For wind tunnel testing the horizontal or vertical orientation doesn't matter. What does matter it that the test object is in the right orientation with respect to the "relative wind". For the rocket, the nose needs to be pointing into the relative wind - the wind generated by the wind tunnel. As far as the rocket is concerned, there is no difference whether the test is done vertically or horizontally as long as the rocket is pointed into the airflow - the stability dynamics are the same. All pitch/roll/yaw dynamics act about the CG and the CG does not change for the vertical or horizontal direction. All NASA rocket wind tunnel tests are performed horizontally. In addition, it is much easier to build a big wind tunnel in the horizontal plane rather than the vertical. Hope this helps...