Calculate Stability of a Model Rocket

It is important in model rocketry to ensure your rocket is stable. A stable rocket will fly as intended, while an unstable rocket will fly in an unpredictable pattern creating a dangerous situation. Stability is extremely important when building a rocket from scratch, but it is not a bad habit to test the stability of model rockets built from kits as well.

In order for the rocket to be stable, the center of pressure must be behind (closer to the tail than) the center of gravity.

Steps

  1. Find the center of gravity of the rocket. This is the point at which you can balance the rocket on your finger.
  2. Tie a four to six foot string around the rocket at this point. When hung from the string, the rocket should be parallel to the ground.
  3. With the rocket suspended by the string, spin in a circle. If the rocket is stable, it will point forward in the direction you're turning.
  4. Adjust the rocket to make it stable. There are two ways to do this.
    • Move the center of gravity forward by adding weight to the nose.
    • Move the center of pressure to the rear by enlarging or adding more fins.

Tips

  • Do this with the motor installed in the rocket, as if ready for flight. This will ensure the center of gravity is as far back as it will likely get.

Warnings

  • Do this outdoors away from people, animals or other obstacles.

Things You'll Need

  • Model Rocket
  • Rocket Engine
  • 4-6 feet of strong string

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