Aerodynamic Reconstruction Applied to Parachute Test Vehicle Flight Data Analysis

Abstract

The aerodynamics, both static and dynamic, of a test vehicle are critical to determining the performance of the parachute cluster in a drop test and for conducting a successful test. The Capsule Parachute Assembly System (CPAS) project is conducting tests of NASA's Orion Multi-Purpose Crew Vehicle (MPCV) parachutes at the Army Yuma Proving Ground utilizing the Parachute Test Vehicle (PTV). The PTV shape is based on the MPCV, but the height has been reduced in order to fit within the C-17 aircraft for extraction. Therefore, the aerodynamics of the PTV are similar, but not the same as, the MPCV. A small series of wind tunnel tests and computation fluid dynamics cases were run to modify the MPCV aerodynamic database for the PTV, but aerodynamic reconstruction of the flights has proven an effective source for further improvements to the database. The acceleration and rotational rates measured during free flight, before parachute inflation but during deployment, were used to confirm vehicle static aerodynamics. A multibody simulation is utilized to reconstruct the parachute portions of the flight. Aerodynamic or parachute parameters are adjusted in the simulation until the prediction reasonably matches the flight trajectory. Knowledge of the static aerodynamics is critical in the CPAS project because the parachute riser load measurements are scaled based on forebody drag. PTV dynamic damping is critical because the vehicle has no reaction control system to maintain attitude -the vehicle dynamics must be understood and modeled correctly before flight. It will be shown here that aerodynamic reconstruction has successfully contributed to the CPAS project.

A Boilerplate Capsule Test Technique for the Orion Parachute Test Program

“…The development of that database is described in Cassidy. 8 The rotation of the parachute compartment had the e↵ect of moving the trim angle-of-attack away from the most unstable region of the C mq vs. ↵ curve.…”

Summary of CPAS EDU Testing Analysis Results

“…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.…”