Wave-tested airbag system boosts safety for ocean spacecraft landings

Wave-tested airbag system boosts safety for ocean spacecraft landings
by Riko Seibo
Tokyo, Japan (SPX) Jul 08, 2025

As space agencies and private companies ramp up reusable spacecraft and deep-space missions, returning safely to Earth-especially via ocean splashdowns-has become a pressing challenge. A new study from Nanjing University of Aeronautics and Astronautics offers critical insights into how reentry capsules interact with waves and airbags during maritime recovery.

Led by Dr. Yang Zhang, the team developed an advanced simulation model to analyze how airbag-cushioned capsules behave when landing in real-world ocean conditions. Their work marks the first detailed fluid-structure interaction (FSI) study that accounts for wave dynamics-an area largely overlooked in earlier recovery designs based on calm water or land impact scenarios.

"Splashdowns are safer than land landings and offer more flexibility," said Zhang. "But waves add unpredictability. Our model shows how crucial it is to factor them in to avoid damage or failure during recovery."

The study combined fluid dynamics, airbag mechanics, and wave behavior into a high-fidelity simulation that revealed several key findings:

Impact forces rise sharply in wave troughs: Landing in a wave trough can increase impact by 40 percent compared to crests, making them the most hazardous points of contact.

Tilt angle and descent speed matter: At moderate vertical speeds (8-10 m/s), proper angle alignment and airbag use can stabilize the capsule. But at higher speeds (16 m/s), even airbags may not prevent capsizing-making strict speed control essential.

Vertical speed is the main driver of impact: Increasing the capsule's entry angle can reduce impact forces by more than 30 percent, while horizontal motion contributes little.

"These findings challenge long-held assumptions that calm-water models are sufficient," Zhang noted. "To ensure crew safety, we need to account for the chaos of real oceans."

The researchers also highlighted that current models still lack turbulence simulation and require real-world validation. Their next step is to collaborate with space agencies on live airdrop trials, creating a feedback loop between simulation and experiment.

Looking ahead, Zhang's team aims to build an intelligent recovery system capable of sensing wave phases and adjusting airbag inflation and descent path in real time. This would allow reentry systems to dynamically adapt to changing sea states and reduce risk during recovery.

"In deep-space exploration, recovery is mission-critical," Zhang said. "We want to ensure that astronauts make it home safely-no matter how rough the ocean gets."

Research Report:Numerical study on water landing characteristics of a reentry capsule with airbag cushioning under calm water and regular/irregular waves