Reconstruction of Orion EDU Parachute Inflation Loads

Abstract

The process of reconstructing inflation loads of the Capsule Parachute Assembly System (CPAS) has been updated as the program transitioned to testing Engineering Development Unit (EDU) hardware. The equations used to reduce the test data have been re-derived based on the same physical assumptions made by simulations. Due to instrumentation challenges, individual parachute loads are determined from complementary accelerometer and load cell measurements. Cluster inflations are now simulated by modeling each parachute individually to better represent different inflation times and non-synchronous disreefing. The reconstruction procedure is tailored to either infinite mass or finite mass events based on measurable characteristics from the test data. Inflation parameters are determined from an automated optimization routine to reduce subjectivity. Infinite mass inflation parameters have been redefined to avoid unrealistic interactions in Monte Carlo simulations. Sample cases demonstrate how best-fit inflation parameters are used to generate simulated drag areas and loads which favorably agree with test data.

Summary of CPAS EDU Testing Analysis Results

“…11 This allows for modeling the variability between parachutes in a cluster, such as differences in opening parameters, timing, and drag coefficient, which greatly improves the ability of the simulation to match flight data precisely. It also increased the number of data points that define the parachute inflation parameter dispersions allowing the move towards statistical distributions.…”

“…A detailed flow chart of this process is shown in Ref. 11. Various instruments measure the necessary data: position, velocity, acceleration, riser and harness loads, atmospheric conditions, vehicle mass properties, and photogrammetry.…”

“…The Analysis team published eleven papers in 2013 covering EDU analysis and testing. These papers discuss modeling improvements, 6,7,8,9,10 and contain test reconstruction updates 11,12,13 and summaries of the individual vehicle test techniques 14,15,16 . A timeline of all three test series and the associated test vehicles is depicted in Fig.…”

Extrapolating the Trends of Test Drop Data with Opening Shock Factor Calculations: the Case of the Orion Main and Drogue Parachutes Inflating to 1st Reefed Stage

“…The main goal of this paper is to show how similar extrapolations can be obtained in the case of Orion-CPAS parachute systems, specifically for both Drogues and Mains opening while reefed (1 st reef Stage inflation) [6,7], in the hopes of extrapolating the reach of test drop data to a significantly wider range of mass ratios, as shown in figures 7 -9 below. For large government R&D programs like CPAS where parachute performance simulation and prediction tools already exist [8,9], such trend expansion calculations provide a sanity check or confirming evidence, in the form of an alternate forecast platform based on different sets of physical approximations and assumptions.…”

Aerodynamic Reconstruction Applied to Parachute Test Vehicle Flight Data Analysis

“…Therefore the load measurements are less than the true parachute riser force. A scale factor is applied to the load measurement based on the aerodynamic drag subtracted from the total drag force as measured by the IMU 4 . This adjustment is accomplished by comparing direct load measurement with the theoretical load measurement that is derived from accelerometer data.…”