When NASA’s Orion capsule splashed down in the Pacific Ocean April 10, completing a successful Artemis II mission milestone, a critical piece of the spacecraft’s safe return traced back to research at Rice University.
The capsule’s three-parachute system — responsible for slowing Orion’s descent and ensuring a safe landing — was developed with key computational parachute fluid-structure interaction (FSI) analysis from mechanical engineer Tayfun E. Tezduyar and longtime collaborator Kenji Takizawa, working alongside NASA Johnson Space Center. Their team was the only group providing computational FSI analysis for the parachute system — work completed in 2013, years before Orion’s return to Earth.
That modeling proved essential to solving one of the most complex challenges in spacecraft parachute design: how to ensure the parachute is both large enough to slow the spacecraft to a safe landing speed and free from descent speed oscillations associated with shape instabilities.
“For a given spacecraft weight, the parachute must generate enough aerodynamic drag to achieve a safe landing speed,” said Tezduyar, the James F. Barbour Professor of Mechanical Engineering at Rice. “But just as important, it has to maintain a stable shape. If the drag fluctuates, so does the descent speed — and that can compromise a safe landing.”
While the aerodynamics of the parachute depend on its shape, the deformation and shape of the parachute fabric structure depend on the aerodynamic forces. This two-way dependence, known as FSI, requires a reliable parachute aerodynamic analysis to actually be a parachute FSI analysis. That, together with the fact that the two-way dependence is even stronger for large parachutes, was one of the many challenges in the computational analysis.
“You cannot separate the aerodynamics from the structural dynamics,” Tezduyar said. “They influence each other continuously and even more so for large spacecraft parachutes, so the analysis must capture that interaction in a robustly coupled way.”
Tezduyar noted that early designs based on scaled-up Apollo-era parachutes revealed what was at stake: NASA drop tests showed large fluctuations in parachute diameter — a sign of shape instabilities that could lead to unsafe landings. Using high-fidelity parachute FSI simulations conducted at Rice, Tezduyar and Takizawa’s team confirmed the issue and helped guide the design toward a more stable configuration.
The final parachute system, refined through a combination of NASA drop tests and Rice’s computational FSI analysis, eliminated those fluctuations, producing a stable descent profile suitable for human spaceflight.
The collaboration also helped reduce development costs and timelines. Each physical drop test was costly and dependent on weather conditions, so the Rice team’s simulations allowed NASA engineers to evaluate designs virtually before committing to real-world testing.
“We ran many, many simulations to test different canopy shapes and suspension-line configurations,” Tezduyar said. “Each one required significant computational resources and time, but it allowed us to narrow down the most promising designs and accelerate the overall design process.”
The work also pushed the boundaries of computational engineering. Modeling Orion’s parachutes required solving complex equations governing airflow and fabric deformation simultaneously, while accounting for features like ringsail canopy construction, which includes hundreds of gaps and slits that the flow goes through as well as aerodynamic interactions among multiple parachutes in a cluster.
Tezduyar emphasized that their work was a team effort.
“We worked very hard at Rice to complete our part of the work quickly,” he said. “Essentially my entire group was dedicated to that work, because I considered it a national priority. Kenji and I were personally involved in every computer simulation. Some of the best graduate students and research associates I met in my career worked on the project, creating unique, first-of-its-kind parachute computer simulations, one after the other.”
Many of those computations are summarized in a recent book authored by Tezduyar and Takizawa.
More than a decade later, their work played a quiet but crucial role in one of NASA’s most triumphant achievements.