Common Causes for a Rocket to Fail

This table contains information about the most common causes for a rocket to fail.

The intent is that, with proper care and prevention, these failure modes may be avoided.  (Source From NASA Houston Rocket Club NAR Section 365)

TASK/STEP	HAZARD	CAUSE	PREVENTATIVE MEASURE
Any	1. Non-Hazardous Anomaly	Premature parachute ejection	All flights in this category result in safe landing under parachute.   –
Flight preparations	2. Premature motor ignition	Connecting igniter to live ignition system	– Using systems with a switch that returns to “off” when released per NAR safety code.  Ensure continuity checker is igniter/electric match/flash bulb safe.
	3. Premature ejection charge ignition	Electronic Altimeter failure / capacitor discharge	-use switch or shunt on charge circuits until placed on pad
Rocket boost	4. Erratic boost	a. Rocket unstable	– Check the stability of the rocket with the selected motor per NAR safety code if not a proven design/motor combination  -Use computer CG/CP program, CP should be 1.0 body diameter aft of CG
		b. Unstable launch pad	– insure launch pad is sufficiently strong to withstand wind and launch forces. – use rail system for HPR launches
		c. Too much wind	– Launch only in winds of less than 20 mph as required by NAR safety code – In windy conditions low thrust launches should be avoided.
		d. Insufficient thrust	– Follow anufacturer¹s recommended maximum lift-off weight per NAR safety code – Use computer simulation program to determine thrust required
	5. Airframe failure	a. Improper construction	– Follow manufacturer assembly instructions. – On original designs use standard construction methods. – Check for secure fins, launch lugs, and proper nose cone fit. – Check secure motor mount assembly.
		b. Fin flutter	– Be sure to align grain with leading edge of fin. (standard construction method) – Avoid high aspect ratio fins
		c. Improper Motor Selection	– Use care in selecting motor for flight.  Follow manufacturer recommendations. – Follow manufacturer recommendations for max lift off weight per safety code. – Attempt high-G launches only rockets having appropriate construction.
	6. Catastrophic motor         failure	a.Temperature cycling of black powder motors	– Store motors at a consistent temperature
		b. Improper construction	– Check all parts have been used (O-rings, ejection charge, spacers, etc.) – Check closures are tight, threads are not stripped.
Rocket recovery	7. Failure to eject     recovery system	a. Motor ejects from rocket	– Use motor retainer clips or sufficient tape to provide positive friction fit of motor – Be sure that recovery system not packed too tightly – Use heat resistant adhesives in motor retention system
		b. Improper assembly of reloadable motors	– Build motor correctly following manufacturer directions  – Avoid grease on delay element  – Avoid crimping or damaging o-rings  -Verify ejection port is clean and clear  – Insure ejection charges are loaded
		c. Electronics failure	– Verify system integrity before first flight or after major changes – Use motor ejection for redundancy
		d. Failure of electronic        recovery system to fire            ejection charge	– Verify charge integrity with multi-tester or self-testing recovery system – Check mach lock-out settings on altimeter – Insure all hardware and electrical leads are installed properly and secured against flight loads.
		e. Construction/ Preparation	– Too much wadding/packed too tightly – parachute packed too tightly – obstructions within body tube
TASK/STEP	HAZARD	CAUSE	PREVENTATIVE MEASURE
	8. Failure of chute to open	a. Recovery device stuck in rocket body	1- Too much wadding 2- Recovery device too large or not packed properly 3- Insufficient ejection charge for size of body tube – see chart
		b. Parachute burned by ejection gasses	– Use flame-resistant recovery wadding or other protection system
		c. Parachute shroud lines fouled	– Fold  parachute carefully as described by manufacturer
	9. Strip of recovery system at deployment	a. Deployment occurred too early or too late	– Follow anufacturer¹s recommended maximum lift-off weight and/or computer simulation data. – Use electronic apogee detecting deployment system. – Use rocket flight simulation program to simulate flight determine best delay time. – Select shorter delays when winds are higher.  The rocket will weather vane into the wind and shorter delays are required for proper recovery system activation.
		b. Improper construction	– Use proper hardware
	10. Separation of recovery or other  system.	a. Recovery system        improperly secured       during preflight prep.	– For initial flight, or subsequent flights after repair, double check that the recovery system is properly attached to the rocket/payload section/nose cone. Inspect quick links, eyebolts, or other hardware to ensure that links are closed/locked and that other hardware is intact and secured. – Insure eye bolt connector will not un-screw during descent
		b. Failure due to wear and     tear of flight operations	– Periodically inspect all components of the recovery system.  Replace/repair burned or worn shock cords. Replace/repair parachutes with worn or frayed shroud lines.
	11. Rocket drifts into buildings / houses / trees	a. Parachute too large	Refer to parachute sizing guide and drift charts on back of checklist
		b. Too windy	Insure winds are within limits. Consider winds aloft information
		c. Main parachute     deploys early	-Use shear pins to secure main parachute compartment. -Use extra long shock cord and “metered deployment” of cord in drogue section. -Use proper amount of black powder in drogue ejection charge
	12. Rocket impacts prep area causing personal injury	Spectators not paying attention to rocket flight	– Use electronic PA system for all high power launches. – Launch Control Officer responsible for calling “Heads Up” -LCO give periodic detailed briefing to spectators on the meaning of ‘heads up’       and the corrective action to be taken -If possible, angle all flights away from spectators
	13. Rocket impacts Buildings/houses in ballistic flight	Multiple failures	-Follow wind/altitude restrictions – see “failure to eject recovery system”

NOTE: Preventative measure is not all inclusive and additional precautions may be required in order to maximize safe flying condition.