Soft deployable airless wheel for lunar lava tube intact exploration

Lunar pits and lava tubes hold promise for future human habitation, offering natural protection and stable environments. However, exploring these sites entails challenging terrain, including steep slopes along cave funnels and vertical cliffs. Here, we present a soft, deployable airless wheel to address these challenges. By achieving a high deployment ratio, multiple rovers can be stowed efficiently without sacrificing mobility, thereby improving mission reliability and flexibility. The proposed wheel incorporates a reconfigurable reciprocal structure of elastic steel strips arranged in a woven helical pattern, enabling shape transformations while preserving load-bearing capacity. This reciprocal arrangement also allows for safe vertical descents and mitigates damage from accidental falls in caves. By distributing strain throughout the wheel's body, reliance on delicate mechanical components is minimized-a critical advantage under extreme lunar conditions. The wheel can be stowed at a diameter of 230 millimeters and deployed to 500 millimeters. Experimental results show successful traversal of 200-millimeter obstacles, stable mobility on rocky and lunar soil simulant surfaces, and resilience to drop impacts simulating a 100-meter descent under lunar gravity. These findings underscore the wheel's suitability for future pit and cave exploration, even in harsh lunar environments.