Space–Time Computational Analysis of the Orion Spacecraft Parachute Aerodynamics and Fluid–Structure Interaction: Virtual Test and Evaluation in Parachute Design

Abstract

The Space–Time Computational Flow Analysis (STCFA) enabled the virtual test and evaluation of spacecraft parachutes and helped reach the final design of the parachutes used in the Orion spacecraft landing in April 2026. Computational fluid–structure interaction (FSI) analysis of spacecraft parachutes requires overcoming a number of formidable challenges. (i) Because the parachute dynamics involves very large air masses compared to the parachute structure mass, the coupled fluid and structure equations need to be solved with the most robust coupling method practically realizable. Otherwise, the computation can generate nonphysical parachute-shape fluctuations, which would be mistaken for actual, physical shape fluctuations. That would, of course, throw off the design process if the design objective is to minimize the physical fluctuations. (ii) Spacecraft parachute canopies have a “ringsail” construction, creating a “geometric porosity” with hundreds of ring gaps and sail slits that the flow goes through to enhance the canopy shape stability, making the FSI problem seemingly intractable. (iii) Spacecraft parachutes are typically used in cluster configurations, where the parachute canopies interact with each other, creating flow computation challenges associated with large mesh deformations and contact between moving structural surfaces. (iv) The final parachute design had, beyond the hundreds of gaps and slits, a “modified geometric porosity,” aimed at enhancing the canopy shape stability. In FSI computations with such modified geometric porosity, the flow through the “windows” created by the removal of the panels and the wider gaps created by the removal of the sails has to be represented in a different way than the flow through the gaps and slits, because they are larger and their sizes are design parameters. Together with the core STCFA methods, a number of ancillary methods played an essential role in overcoming these challenges, leading to the first-ever FSI computation of the Orion spacecraft final-design parachute clusters, which was reported in 2013. We provide an overview of the core and ancillary STCFA methods that enabled the computations reported in 2013 and summarize the computations carried out for various parachute designs tried before reaching the final design and for other types of parachutes involved in the deceleration of the Orion spacecraft as it returns to Earth. We also provide an overview of the methods we introduced since 2013 to increase the fidelity and scope of spacecraft parachute computational flow analysis and summarize the computations carried out since then. These new developments include extending the computations to compressible flows and upgrading the discretization from finite elements to isogeometric analysis, first with NURBS and then with T-splines.