NAR HPR Propulsion Systems & Motor Handling 3

Question 1

What is 'specific impulse' (Isp) as applied to rocket motor performance?

Accepted Answer

The thrust produced per unit weight flow rate of propellant, measured in seconds

Answer

Specific impulse (Isp) is a measure of propellant efficiency: thrust divided by propellant weight flow rate, with units of seconds.

Question 2

When a reloadable motor casing shows visible cracks, bulging, or heat discoloration after a flight, the correct action is to:

Accepted Answer

Retire the casing from service immediately and do not reload it

Answer

Any structural damage or severe heat discoloration on a reloadable casing is grounds for immediate retirement to prevent catastrophic failure.

Question 3

The 'thrust curve' of a rocket motor graphically shows which relationship?

Accepted Answer

Thrust output versus time during the burn

Answer

A thrust curve plots thrust (in Newtons) on the Y-axis versus time (in seconds) on the X-axis, describing how thrust changes throughout the burn.

Question 4

A 'regressive' burn profile in a motor means that thrust:

Accepted Answer

Starts high and decreases over the course of the burn

Answer

A regressive burn profile produces higher initial thrust that tapers downward as propellant is consumed, due to decreasing grain surface area.

Question 5

Under what circumstance is it permissible to fly a high-power motor that is not on the NAR/TRA certified motors list?

Accepted Answer

It is never permissible; only certified motors may be flown at sanctioned launches

Answer

NAR and TRA require all motors flown at sanctioned events to be currently certified; no exceptions exist based on certification level or other conditions.

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

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

NAR HPR Propulsion Systems & Motor Handling 3