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I have watched many videos of large but "amateur" (not military or NASA) rockets and I would have guessed that without some sort of stabilizers like gyroscopes or fins the rocket might wobble or show some other kind of major instability. However such rockets go straight and I am wondering if they all have in fact gyroscopes.

My own experience with model rockets is that they did have fins and bottle rocket fireworks had a long wooden tail that perhaps helped stabilize it. But for larger rockets that go many thousands of meters it does not seem like a gyro would be enough to combat the forces that could cause wobbling, etc.

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Yes, almost all rockets require stabilization.

Simple gyroscopes are not practicable because anything big enough would weigh too much. But small, freely-gimballed ones can be used to signal deviations, and those signals can be fed to an active system. For example the V-2 rocket of WWII had small fins directly in the rocket exhaust and these were used to steer the rocket until it built up enough speed for its outer, aerodynamic fins to work. Modern rockets often have engines mounted on gimbals so the thrust can be steered to maintain attitude.

A stick on a firework rocket provides stability through a combination of its aerodynamic effect as a tail and its trailing mass which moves the centre of mass aft.

If there is sufficient aft mass behind the aerodynamic center of pressure, as in Robert Goddard's first rocket or a space capsule escape rocket perched above its nose on the launch pad, then no other stabilization is needed for vertical flight, but that is very rare.

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  • $\begingroup$ Does your last paragraph contradict en.wikipedia.org/wiki/Pendulum_rocket_fallacy ? $\endgroup$ – DJohnM Mar 11 at 21:34
  • $\begingroup$ As far as I am aware, the effect is dependent on the relation between the center of mass and the aerodynamic center of pressure: if the CM is behind the CP there will be a net moment restoring vertical orientation, and vice versa. This is nothing to do with the thrust fallacy. But yes, I can see that I expressed it badly, thanks for spotting it. I have had a go at clearing it up, Any better now? $\endgroup$ – Guy Inchbald Mar 12 at 10:07
  • $\begingroup$ Thinking about it, the aerodynamic and gravitational effects conflict: An aft CP gives "arrow" stability in the current direction of travel, while an aft CM gives "plumbline" stability in the vertical direction only. I guess the stick works because the trajectory is basically vertical so one effect or the other will work. Maybe I should add that too? $\endgroup$ – Guy Inchbald Mar 12 at 15:46

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