NAR HPR Aerodynamics & Stability 2

Question 1

What does a negative static margin indicate about a rocket's stability?

Accepted Answer

The rocket is unstable and will likely tumble or veer off course

Answer

A negative static margin means the Center of Pressure is ahead of the Center of Gravity, causing the rocket to be aerodynamically unstable.

Question 2

How does adding nose weight affect the stability of a marginally stable rocket?

Accepted Answer

It moves the CG forward relative to the CP, increasing stability

Answer

Adding nose weight shifts the CG forward, increasing the distance between CG and CP and thus improving the stability margin.

Question 3

What is the primary aerodynamic purpose of boat-tailing a rocket's airframe?

Accepted Answer

To reduce base drag by smoothing airflow at the aft end

Answer

Boat-tailing tapers the aft section of the airframe, reducing the size of the turbulent wake and thereby decreasing base drag.

Question 4

Which fin configuration is most effective at minimizing roll coupling during flight?

Accepted Answer

Four fins arranged symmetrically with no cant

Answer

Four fins arranged symmetrically with no cant produce balanced lift forces and minimize induced roll torque.

Question 5

What aerodynamic phenomenon causes a rocket to 'weathercock' into the wind?

Accepted Answer

The CP being ahead of the CG causes the nose to turn into the wind

Answer

When CP is ahead of CG (unstable condition), aerodynamic forces rotate the nose into the wind, a behavior called weathercocking.

(NAR HPR) NAR High-Power Rocketry Certification Practice Test