478698 Degradation of Nylon 6,6 Parachutes and Implications for Long Term Scientific Ballooning

Monday, November 14, 2016
Grand Ballroom B (Hilton San Francisco Union Square)
Samuel H. Jubb and Sarah Roth Fischer, Balloon Program Office, NASA's Goddard Space Flight Center - Wallop's Flight Facility, Chincoteague, VA

In order to achieve the desired 100-day flight time of future Super Pressure and Zero Pressure balloons, NASA’s Balloon Program Office (BPO) tasked the Balloon Research & Development Lab (BRDL) with determining the impact of environmental effects (including UV degradation) and use on the strength retention of parachutes for scientific balloon payload recovery. The BRDL received a parachute recently used in the recovery of a scientific balloon payload; the entire parachute canvas is woven from nylon-6,6, however the crown was woven in a twill pattern while the gore was woven in a rip-stop pattern. Samples from both sections of the parachute were cut, characterized, and compared to virgin nylon material to ascertain the effects of 30 days in flight at mid-latitudes in the southern hemisphere in conjunction with 30 days on the ground in the Australian Outback on the strength of the parachute. The data was collected through the use of various constant-rate-of-extension tensile testing machines in the BRDL. Results illustrated that the 60 total days of exposure did not statistically affect the overall strength of the gore material in any of the three modes of strength testing. Reefing during flight may contribute to decreased degradation when considering exposure on the entire surface area. In tearing and breaking strength tests, crown material showed a marked decrease in strength from virgin to used material, but virgin and used crown data points possessed little variation between in other with impact testing.

In addition to general sampling across the entire parachute, a study to determine the relationship between material fade and strength retention was conducted. Samples with no fade, samples with a stripe of fade across the middle of the testing area, and completely faded samples were cut from the used parachute. This was an attempt to characterize degradation differences due to reefing. The data collected from this study was also compared to the results acquired from testing of virgin materials. Though faded areas on the parachute provide consistent failure points when tested, the average strength across the entire used parachute still lies above the lowest acceptable limit set by the Parachute Industry Association (PIA).


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