HPR Level 2—Section D: Rocket Stability
D1) For a rocket to be stable, which of the following statements is true?
A) The center of pressure (CP) must be behind the center of gravity (CG)
B) The center of pressure (CP) must be in front of the center of gravity (CG)
C) The rocket must have fins
D) The length of the body tube must be at least 5 times the model diameter
D2) An unstable rocket can be made stable by:
A) Adding sufficient weight to the nose cone
B) Removing sufficient weight from the nose cone
C) Moving the fins sufficiently forward towards the nose cone
D) Making the rocket sufficiently shorter
D3) Rocket stability can be estimated by:
A) Center of pressure “Barrowman” equations
B) “Cardboard cutout” method
C) Determining the relative positions of the center of pressure (CP) and center of gravity (CG)
D) Stability cannot be estimated before a test flight.
D4) A rocket’s center of pressure can be estimated by using:
A) The “Barrowman” method
B) Finding the point where the model balances
C) The “cardboard cutout” method
D) Both “A” and “C” above
D5) An unstable rocket can usually be made stable by:
A) Using a shorter nose cone
B) Increasing the size of the aft fins
C) Using a larger, heavier rocket motor
D) Increasing the rocket diameter
D6) During boost, a rocket powered by a solid rocket motor tends to:
A) Become less stable in flight
B) Become more stable in flight
C) Have no change in stability
D) Become unstable
D7) Which of the following can cause unstable flight?
A) Weak tubes or couplers that permit airframe bending
B) Misaligned motor mount tube or motor nozzle
C) Inadequate airspeed leaving the launch pad on a windy day
D) All of the above
D8) As a rule of thumb, how far should the center of pressure be from the center of gravity?
A) The center of pressure should be at the same location as the center of gravity
B) The center of pressure should be at least 1.0 body tube diameters behind (aft) the center of gravity
C) The center of pressure should be at least 1.0 body tube diameters ahead (forward) of the center of gravity
D) The center of pressure should be 1.0 body tube diameters ahead (forward) of the fin leading edge; the center of gravity does not matter
D9) The definition of Positive Stability in regards to a rocket is:
A) Where the center of gravity (CG) is located ahead (forward) of the center of pressure (CP)
B) Where the center of gravity (CG) and the center of pressure (CP) lie at the same locations
C) Where the center of gravity (CG) is located behind (aft) of the center of pressure (CP).
D) None of the above
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