EllieClifford: "Add old wiki"

2021-04-19T18:58:19Z

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A compilation of reasons why your rocket may no longer be in one piece

# The chute shroud lines being the same length as the shock cord, therefore the shock cord could go tight without ensuring the chute was completely out of the bay.
# Poor shock cord attachment at motor end or nose end.
# Poor Nomex placement results in burnt chute/shock cord
# Chute tangles are reduced with use of a swivel.
# Shock cords about 5m to reduce shock loads.
# Place chute so that nose and tail sections don't bash each other on decent.
# Ensure chute compartment is sufficiently sealed so that it can pressurise, primarily between the altimeter bay which should be well vented.
# Motor retention inadequate, resulting in motor being ejected rather than chute.
# Flight computer must signal continuity on pad.
# Flight computer can signal continuity but have damaged capacitor so not fire, ground test firing circuit if possible.
# Use redundant systems, two flight computers.
# Don't use smokeless powder, it is too pressure sensitive. Blackpowder substitutes behave differently and should be avoided
# Make sure e-matches are well clamped in screw terminals.
# Use acceleration tolerant switches, key switches are good.
# Align switches perpendicular to axis to avoid acceleration effects.
# Shock cord not strong enough, assume 20g loads (probably excessive)
# Use kevlar cord (heat resistant) next to ejection charge and nylon cord or tape to reduce shock load.
# Use good knots, bowlines, barrel knots and fig 8 for cord, tape knots and overhands for tape.
# Use tape to pad kevlar cord where it leaves body tube to avoid tube damage "zipper effect"
# Ground test every deployment three times, to check for repeatability
# Ejection charges are best mounted centrally on bulkheads, use eyenuts on the end of studding if required.
# Only use masking tape to adjust fits, other tape generally binds worse.
# Check friction in joints, it can change.
# Use a rape alarm so you can find the debris
# Compartments vented so that reduced ambient pressure doesn't cause premature separation.
# Vent altimeter bays symmetrically to avoid false readings from wind.
# Ensure ejection charge not going to change due to acceleration (ie use wadding).
# Use nylon shear pins (M2) to stop main deploying at drogue deployment.
# A shear pin can be used to stop the drag on the fins at motor burn out causing separation, has this ever happened?

Rocket recovery system failure modes - Revision history

EllieClifford: "Add old wiki"