As global interest in reusable spacecraft and crewed deep-space exploration surges, ensuring the safe recovery of spacecraft in complex maritime environments has become a critical challenge. A groundbreaking study led by researchers from Nanjing University of Aeronautics and Astronautics, published in the Chinese Journal of Aeronautics on June 6, 2025, has systematically decoded the water-landing characteristics of reentry capsules equipped with airbag cushioning systems under wave conditions using a fluid-structure interaction (FSI) model. This research not only provides a scientific foundation for optimizing spacecraft recovery design but also establishes a technical cornerstone for the safety of future crewed missions.
Spacecraft recovery is the "final mile" of crewed space missions, directly impacting personnel safety and equipment integrity. Compared to land recovery, maritime recovery—with its lower impact forces (36% of land impacts), enhanced safety in unpopulated areas, and vast landing flexibility—is the preferred method for crewed missions. However, the complex interactions between reentry capsules and waves, as well as the coupling effects of airbag cushioning and hydrodynamic forces, have long been engineering blind spots.
"With the rise of commercial aerospace and reusable technologies, airbag cushioning systems, such as those on Boeing's CST-100 and the Orion spacecraft, are widely adopted to mitigate impact forces. Yet prior studies focused on land or calm-water scenarios, leaving the mechanisms of capsule-airbag-wave interactions in real ocean environments poorly understood," emphasized Dr. Yang Zhang, corresponding author of the study and an associate researcher at the College of Astronautics, Nanjing University of Aeronautics and Astronautics. "Failure to accurately predict impact loads under wave conditions could lead to structural damage or even mission failure."
The team developed a high-fidelity FSI model integrating fluid dynamics (ALE method), airbag dynamics (control volume method), and wave coupling, and uncovered the following pivotal mechanisms:
- Speed control & angle adjustment ensure stability. At medium speeds (8-10 m/s), airbags stabilize the capsule when paired with optimal tilt angles. However, high speeds (16 m/s) risk capsizing even with airbags, requiring strict speed limits.
- Vertical speed drives impact; attitude angle reduces force. Vertical velocity is the main contributor to peak impact forces, while horizontal speed has minimal effect. Increasing attitude angles cuts impact forces by over 30%.
- Wave troughs pose highest risk; design for chaos. Wave troughs generate 40% higher impacts than crests. Systems must withstand both predictable regular waves and chaotic irregular waves, especially at higher speeds.
"These findings subvert traditional design paradigms dominated by calm-water assumptions," Dr. Zhang stressed. "The randomness of real-world ocean waves must be integrated into recovery system designs."
While the study marks a milestone, the team acknowledges limitations: turbulence effects are unaccounted for, and model accuracy requires enhancement through integration of drop-test data. Next, the team will collaborate with space agencies to conduct maritime airdrop trials, establishing a "simulation-testing" validation loop.
"In the era of deep-space exploration, safe recovery is the 'lifeline' of crewed missions. We hope this work adds certainty to humanity's journey to the stars. Our ultimate goal is to develop an intelligent recovery system adaptive to wave environments," Dr. Zhang revealed. "By real-time sensing of wave phases and capsule dynamics, we aim to dynamically adjust airbag pressure and landing trajectories to keep impact forces within safety thresholds."
Other contributors include Shiqing Wu, Jiangli Lei, Wei Huang, Huai Xie from Beijing Institute of Space Mechanics and Electricity in Beijing, China.
Original Source
Jiapeng HAN, Shiqing WU, Jiangli LEI, Wei HUANG, Huai XIE, Yang ZHANG. Numerical study on water landing characteristics of a reentry capsule with airbag cushioning under calm water and regular/irregular waves [J]. Chinese Journal of Aeronautics, 2025, https://doi.org/10.1016/j.cja.2025.103615.
About Chinese Journal of Aeronautics
Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.7, Q1), EI, IAA, AJ, CSA, Scopus.
