NAR HPR Propulsion Systems & Motor Handling 2

Question 1

What does the letter 'I' in a motor designation like 'I211W' indicate?

Accepted Answer

Total impulse between 320.01 and 640 N·s

Answer

The letter in NFPA 1125 motor designation indicates the total impulse range, with each letter doubling the previous; 'I' represents 320.01–640 N·s.

Question 2

When storing high-power rocket motors, what is the maximum quantity of propellant that may be stored in a Type 4 magazine under NFPA 1124?

Accepted Answer

50 lbs (22.7 kg) net explosive weight

Answer

NFPA 1124 allows up to 50 lbs net explosive weight (NEW) in a Type 4 storage magazine for consumer and high-power rocket motors.

Question 3

What is the primary function of the forward closure (nozzle end cap) in a reloadable motor casing?

Accepted Answer

To seal the combustion chamber and retain forward thrust pressure

Answer

The forward closure seals the aft end of the casing opposite the nozzle, containing combustion pressure and directing thrust through the nozzle.

Question 4

A motor with designation '29/180-360' on its casing refers to which specification?

Accepted Answer

29mm diameter casing rated for 180 to 360 N·s total impulse

Answer

This designation describes the casing diameter (29mm) and the range of reload total impulses (180–360 N·s) it is rated to accommodate.

Question 5

Which propellant type used in many high-power motors produces a characteristic white smoke and is known for high specific impulse?

Accepted Answer

Ammonium perchlorate composite propellant (APCP)

Answer

APCP is the standard propellant for certified high-power motors, producing white exhaust and offering higher specific impulse than black powder.

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