Advancing space health: Towards a soft wearable hypogravity exosuit for enhanced mobility in Martian conditions

As space exploration advances and human travel to Mars becomes reality, addressing the adverse effects of prolonged spaceflight on the human body is critical. Long-term exposure to hypogravity (gravity lower than Earth's) during space missions leads to muscle and bone loss, posing significant health degeneration for astronauts. Current countermeasures, such as exercise routines and rigid body-assisting exoskeletons, do not fully address the issue. Moreover, astronauts may encounter injuries associated with extended spaceflight, particularly from wearing Extravehicular Mobility Units (EMUs). To tackle these challenges, the development of a soft wearable hypogravity exosuit is proposed. It utilises Bubble Artificial Muscles (BAMs), soft lightweight pneumatic actuators that offer a high strength-to-weight ratio. For this study, three parallel BAMs were used to create a wearable device to assist leg flexion during walking in extraterrestrial gravity. An experimental rig emulating knee swing during walking was used to evaluate assistive performance. The device was tested across a range of torques and angular displacements, while exploring the effect of different proportional-integral control parameters. It was found that the device can effectively deliver timely assistance, increasing the maximum flexion angle and angular velocity during walking in simulated Martian gravity. The integration of BAMs in wearable devices holds potential benefits not only for space exploration but also for terrestrial applications for individuals with mobility challenges.