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?