NAR HPR Rocket Design & Construction 3

Question 1

What is the typical recommended wall thickness for a phenolic or fiberglass airframe tube used in a Level 2 high-power rocket?

Accepted Answer

0.060–0.125 inches

Answer

Level 2 rockets typically use tubes with wall thickness of 0.060–0.125 inches to balance weight, strength, and cost for typical L2 motor impulse ranges.

Question 2

What is the significance of the 'stability margin' being expressed in calibers rather than absolute length?

Accepted Answer

Calibers normalize stability relative to body diameter, allowing comparison across rocket sizes

Answer

Expressing stability margin in calibers (body diameters) normalizes the measurement, making it meaningful across rockets of different sizes.

Question 3

Which construction method produces the strongest fin-to-body attachment for high-power rocketry?

Accepted Answer

Through-the-wall (TTW) fins bonded to the motor mount tube with internal fillets

Answer

Through-the-wall fins extend through the airframe to bond directly to the motor tube, distributing loads over a larger area and greatly increasing joint strength.

Question 4

What is 'ballistic coefficient' and why does it matter in high-power rocketry?

Accepted Answer

A measure of a rocket's ability to overcome aerodynamic drag, affecting terminal velocity and altitude

Answer

Ballistic coefficient (mass divided by drag area) determines how well the rocket maintains velocity against drag, affecting maximum altitude and terminal descent speed.

Question 5

When using RockSim or OpenRocket, what does a Barrowman stability calculation assume about the rocket's flight regime?

Accepted Answer

Subsonic, non-spinning, small angle of attack flight

Answer

The Barrowman equations are valid for subsonic, non-spinning rockets at small angles of attack and become inaccurate at transonic or supersonic speeds.

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

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

NAR HPR Rocket Design & Construction 3