NAR HPR Rocket Design & Construction 2

Question 1

What is the primary function of a boat-tail transition on a high-power rocket?

Accepted Answer

Reduce base drag by tapering the aft end

Answer

A boat-tail reduces base drag by smoothly tapering the rocket's diameter at the aft end, reducing the turbulent wake behind the airframe.

Question 2

When bonding fiberglass airframe sections, which surface preparation step is most critical for joint strength?

Accepted Answer

Sanding the bonding surfaces and wiping with acetone

Answer

Sanding creates mechanical tooth for adhesion and wiping with acetone removes oils and contaminants that would prevent a strong epoxy bond.

Question 3

What does a positive pitching moment coefficient (Cm > 0) indicate about a rocket's aerodynamic stability?

Accepted Answer

The rocket is statically unstable

Answer

A positive Cm means the aerodynamic moment tends to increase the angle of attack rather than restore it, indicating static instability.

Question 4

What material property is most important when selecting epoxy for a high-power rocket motor mount subject to thermal cycling?

Accepted Answer

High glass transition temperature (Tg)

Answer

High Tg epoxy retains strength at elevated temperatures, which is critical near the motor mount where heat from motor operation is significant.

Question 5

In high-power rocketry, what is the purpose of a thrust plate (or thrust ring) in the motor mount assembly?

Accepted Answer

To transfer motor thrust directly to the airframe structure

Answer

The thrust plate transfers the compressive thrust load from the motor casing directly to the airframe, preventing the motor tube from bearing all the thrust force alone.

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

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

NAR HPR Rocket Design & Construction 2