Preventing Structural Collapse During Acceleration of Relativistic Lightsails for Interstellar Travel

Interstellar travel requires new propulsion mechanisms. Employing radiation pressure from a high-power ground-based laser is a conceivable route to accelerate an ultralight spacecraft to a significant afraction of the speed of light. To adhere to strict mass constraints, such a spacecraft can employ an ultrathin elastic membrane for its lightsail. During acceleration, a uniform membrane will deform significantly, potentially leading to its collapse. Here, we study the deformation of circular lightsails propelled by a Gaussian laser beam. We observe a significant change in scaling laws when increasing the lateral sail size from laboratory-scale (tens of micrometers) to mission-scale (several meters). A buckling analysis reveals critical accelerations and suggests design principles for hoop stiffening elements to increase the maximum acceleration. These findings serve as the basis to understand and prevent relativistic-lightsail collapse during acceleration.