NAR HPR Electronics & Avionics 2 — Questions and Answers
Question 1: What is the primary purpose of a dual-deployment altimeter in a high-power rocket?
- To measure peak altitude only
- To fire drogue at apogee and main at a lower altitude (Correct answer)
- To ignite the motor electronically
- To transmit GPS coordinates to the ground
Correct answer: To fire drogue at apogee and main at a lower altitude
Dual-deployment altimeters fire a drogue parachute at apogee and a main parachute at a preset lower altitude to control descent rate.
Question 2: Which battery type is most commonly recommended for powering avionics bays in high-power rocketry due to its stable discharge curve?
- Carbon-zinc
- Alkaline AA
- 9V lithium (Correct answer)
- NiMH rechargeable
Correct answer: 9V lithium
9V lithium batteries are preferred for avionics because they maintain stable voltage under load and perform reliably across temperature extremes.
Question 3: What does 'continuity' indicate on an altimeter's pre-launch status check?
- The altimeter has reached operating pressure
- An electrical circuit through the e-match or initiator is complete (Correct answer)
- The parachute bay is sealed
- The battery is fully charged
Correct answer: An electrical circuit through the e-match or initiator is complete
Continuity means current can flow through the e-match circuit, confirming the pyrotechnic initiator is properly connected and functional.
Question 4: When installing an avionics bay, why must the vent holes be positioned away from the fin can area?
- To prevent motor exhaust pressure from triggering false apogee detection (Correct answer)
- To improve radio signal strength
- To reduce aerodynamic drag
- To keep wiring harnesses cool
Correct answer: To prevent motor exhaust pressure from triggering false apogee detection
Motor exhaust can pressurize the airframe near the fin can; vent holes placed there could cause the altimeter to detect a false pressure event and fire pyros prematurely.
Question 5: What is the function of a 'shunt' or 'shorting plug' used with e-match circuits before flight?
- It boosts firing current to the e-match
- It short-circuits the e-match to prevent accidental ignition (Correct answer)
- It tests the altimeter's ARM mode
- It grounds the airframe to dissipate static
Correct answer: It short-circuits the e-match to prevent accidental ignition
A shorting plug bridges the e-match leads together, preventing any stray current from accidentally firing the pyrotechnic charge during handling.
Question 6: In rocketry avionics, what does 'arming altitude' refer to?
- The altitude at which the motor ignites
- The minimum altitude the rocket must exceed before pyro channels are enabled (Correct answer)
- The height at which GPS locks onto satellites
- The apogee detection threshold
Correct answer: The minimum altitude the rocket must exceed before pyro channels are enabled
Arming altitude is a programmable threshold that prevents the altimeter from firing pyro channels unless the rocket has climbed above a set altitude, avoiding ground-level misfires.
Question 7: Which wiring practice is critical to prevent RF interference from triggering e-matches in high-power rocketry electronics?
- Using unshielded wire for all pyro circuits
- Twisting pyro lead wires together and keeping runs short (Correct answer)
- Routing pyro wires parallel to antenna leads
- Using maximum wire gauge throughout
Correct answer: Twisting pyro lead wires together and keeping runs short
Twisting pyro lead wires cancels induced electromagnetic fields and keeping runs short minimizes the loop area that can act as an antenna.
NAR HPR Electronics & Avionics 2
What is the primary purpose of a dual-deployment altimeter in a high-power rocket?