A Sample/Jitter Monte Carlo Technique for Main Parachute Loads Predictions

Models for Orion parachute performance are based on reconstructions of the Capsule
Parachute Assembly System (CPAS) drop test campaign and were documented in the CPAS
“Model Memo.” Experience with similar Commercial Crew Program (CCP) parachute
systems resulted in some updates to the Orion models in preparation for Artemis missions.
The reefing cutter dispersion model for the drogues and mains had been overly-conservative
by producing wide timing differences within clusters. A higher-fidelity timing model was
generated by separating out in-lot variation and temperature effects. The main parachute
inflation model had accounted for some correlations between parameters using complicated
2-D geometric bounding, but the results tended to exaggerate individual peak loads from fast
(leading) inflations and under-emphasize actual lagging experience. Several flight tests were
reconstructed again with an emphasis on matching peak load magnitudes using a search
algorithm. A simpler method for generating inflation parameters uses the 3-D correlated
reconstructed “samples” with some random “jitter” applied. Dispersed Monte Carlo inputs
are then checked against flight test data to evaluate whether they represent reality.