Extended space dive

Extended space dive
by Erica Marchand
Paris, France (SPX) Mar 14, 2025

European scientists are enlisting volunteers to lie on waterbeds for 10 consecutive days in an innovative study aimed at replicating some of the physiological effects of space travel.

The Vivaldi experiment, now in its third and final phase, is being conducted at the Medes space clinic in Toulouse, France. This phase involves the longest immersion period yet and runs alongside a head-down bed rest study, with a total of 20 participants taking part.

The Vivaldi Experiment

During this latest phase, known as Vivaldi III, 10 volunteers recline in specialized tubs covered with waterproof fabric, ensuring they remain dry while being evenly supported by the water. This setup provides a sensation akin to weightlessness, closely resembling the experience of astronauts aboard the International Space Station.

For the entire 10-day period, participants remain in these water-filled enclosures, undergoing a series of medical and scientific studies designed to explore how space conditions impact the human body. Volunteers use floating boards and neck pillows during meals, and bathroom breaks involve being transferred onto a trolley while maintaining their reclined position.

Previous Vivaldi campaigns tested a five-day dry immersion study with both male and female volunteers. This final phase extends the immersion to 10 days and runs parallel with a 10-day head-down bed rest study, each involving 10 male participants.

Both techniques-dry immersion and head-down bed rest-help replicate conditions encountered in space.

"By extending the duration of dry immersion and comparing it to bed rest, we are refining our understanding of how these analogues simulate life in space, the different physiological effects, and how they complement each other," explains Ann-Kathrin Vlacil, team leader for enabling science in human exploration at ESA.

Understanding Space's Effect on the Human Body

In the absence of gravity, astronauts undergo a variety of physiological changes. Muscle and bone density decline, the shape of the eyeball may shift, and fluids redistribute toward the brain.

Dry immersion helps simulate these effects by removing weight from the body, while head-down bed rest mimics fluid shifts and the lack of movement astronauts experience in microgravity. Both techniques trigger changes in the neurological, cardiovascular, and metabolic systems.

Additionally, researchers are examining hormonal fluctuations, immune system responses, and the interactions between the nervous and vision systems. The controlled nature of the study allows for real-time medical assessments and close monitoring of physiological changes.

Earth-Based Benefits

Although designed to mitigate health risks for astronauts and develop countermeasures for extended space missions, the Vivaldi study also has significant implications for Earth-based medicine.

"Bridging the gap between spaceflight and ground-based research is essential for human space exploration. Our findings have significant implications for Earth-based medicine, particularly in ageing-related conditions," says Marc-Antoine Custaud, head of ESA's bed rest and dry immersion campaigns from the University of Angers, France.

Insights from the study may lead to improved treatments for bedridden patients, the elderly, and individuals with musculoskeletal disorders, offering broader healthcare applications beyond space travel.