Service life of stratospheric balloon gondola recovery parachutes - Part I

摘要

Parachute storage, service, use, and life expectancy have been well documented for both single-use and multiple-use parachutes utilized in U.S. Army troop and cargo deployment, U.S. Forest Service applications, civilian sport, and the Space Shuttle Orbiter program. Each application has an extremely diverse set of operating conditions, and the nature of the cargo has dictated rather conservative lifetime models. It has been determined by the U.S. Army Natick Soldier Research, Development and Engineering Center that nylon 6,6 can withstand ambient storage conditions (without use) for 30+ years without significant strength loss. It has also been determined that the major environmental factor affecting the fabrics for both the canopy and suspension lines during normal tropospheric conditions is penetration by debris such as dirt, sand, and salt. Currently, very little research has been done to define degradation due to exposure to the higher intensity short-wave radiation and extreme cold temperatures experienced by stratospheric flights. There is also periodic exposure to the ozone layer, coupled with chain scission from the exposure to shortwave radiation, which combined may cause undesired carbon functionalization. It is desired to determine if stratospheric exposure during a single flight reduces the effectiveness of the parachute below the minimum acceptable limit for safe recovery of the gondola. Furthermore, due to costs associated with manufacturing these highly specified parachutes, it is advantageous to develop a method for non-destructive analysis and repair for potential reuse. This paper will explore the various conditions experienced during stratospheric flight and begin to model the life expectancy in those conditions for both single-use and multiple-use parachutes. Experimental verification will include data obtained from several recovered balloon gondola parachutes as well as controlled laboratory settings that model various stratospheric conditions.