Summary of Issues that arose during development of DS/Xi Recovery Deployment system

Rocket Flight	Issue	Cause	Fix
DS-2/DS-3	Parachute deployed at apogee	Momentum of separating rocket sections at apogee caused nylon screws at forward AvBay joint to shear	Increased number of #6 nylon screws at this joint (increase from 4 screws to 6)
DS-4	Parachute tether snapped during deploy	Increased momentum of separating sections due to fix implemented to nylon screws at this joint	Parachute tether (3.2mm) was tested and found to have breaking strength of 250 lbf. Replaced with 5mm nylon rope with breaking strength 900 lbf.
DS-8	Phenolic forward bulkhead of AvBay fractured	Increased pyro pressure due to greater number of shear screws resulted in structural failure of bulkhead	Replaced phenolic bulkhead with aluminum bulkhead
Xi-1	Tether connecting Aft section to AvBay snapped upon parachute deploy	Not definitely determined	Tether breaking strength tested to be 340 lbf. Shock absorber added to tether
Xi-1	Primary apogee pyro fired but did not separate rocket sections. Firing of secondary pyro successfully resulted in separation	Cold ambient temperature resulted in reduced pressure generated by primary apogee pyro.	Apogee pyro CP content increased from 1.0 gram to 1.3 grams.
Xi-2	Tether connecting AvBay to NFB broke resulting in chute not being extracted	Insufficient venting of parachute bay caused suction effect when NFB pulled out.	Venting holes (qty.6) were increased in size from 1/8² to 3/8². Dual-tether philosophy implemented for all tethers.
Xi-4	Parachute pyro fired but did not separate rocket sections. Firing of secondary pyro successfully resulted in separation and deployment of chute.	Cold ambient temperature resulted in reduced pressure generated by primary parachute pyro.	Parachute pyro CP content increased from 1.2 gram to 1.4 grams.
Xi-4	One of the two tethers connecting AvBay to NFB fractured.	Some heat damage occurred to tethers.	Tethers were coated with silicone to improve heat resistance. Length of tethers increased from 40 to 72cm to improve shock-resistance.
Xi-8	Fixed Ring (NFB reaction point) attachment failed resulting in non-deployment of chute	Joint not sufficiently damage-tolerant. May have had hidden damage resulting from hard landings.	Ring had been secured to body tube with six 9/32² diameter epoxy ‘slugs’. Now secured with twelve 19/64² diameter slugs made from J-B Weld.
Xi-9	One of the two apogee tethers was found to have been cut	Appeared to have contacted hot motor nozzle during the separation event.	Apogee tethers partly coated with silicone to reduce likelihood of heat damage.
Xi-13	Eyebolt connecting AvBay to forward section of rocket came loose causing separation during descent	Spiraling motion during descent unscrewed nut attaching eyebolt	Loctite implemented for eyebolt nut attachment.