Sequential stills from a test sequence, showing a test mass inside a box being dropped down a drop tower encountering a simulated sandy asteroid surface. A team at the Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-Supaero), part of the University of Toulouse, worked with the University's Department of Mechanics of Structures and Materials, rigged up a system of pulleys and counterweights to simulate reduced-gravity with the drop tower. Such towers are typically used to recreate full weightlessness.