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The Mars Scout Phoenix program is the next planned mission to Mars, set for launch in the summer of 2007 with an anticipated landing in May of 2008. Similar to previous Mars missions, the Entry, Descent, and Landing (EDL) architecture deploys a parachute at supersonic speeds for deceleration and to establish an appropriate descent timeline that supports all EDL functions. Because of the rapid inflation time and low-density atmospheric conditions, the Parachute Decelerator inflates in a manner that industry refers to as an Infinite Mass Inflation. Under these conditions, there is limited vehicle deceleration during parachute inflation and the peak parachute load occurs at full inflation. Replicating this type of inflation process in the comparatively high density Earth atmosphere is among the most challenging aspects of an aerial structural qualification program. The difficulties include the use of an extremely large vehicle mass to overcome the enhanced drag forces during parachute inflation, along with the increased apparent mass loads that may combine to exceed the strength of the parachute. Mars Exploration Rover (MER) parachute development and qualification utilized the NASA Ames National Full-Scale Aerodynamics Complex (NFAC) to ameliorate these issues. Unfortunately the NFAC was closed shortly after MER requiring the Mars Phoenix program to use the more conventional aerial test method. To correctly design and plan the Mars Phoenix Parachute Deceleration System Aerial Structural Qualification Test, a Monte-Carlo type analysis technique was developed to provide probabilistic guidance for the selection of the optimum test conditions that would yield a “near Infinite Mass Inflation”. This paper discusses the aerial testing analysis technique developed for the Mars Phoenix program to understand peak load prediction uncertainty in this environment. |
