  This work presents an experimental design for studying low-velocity
collisions into granular surfaces in low-gravity. In the experiment apparatus,
reduced-gravity is simulated by releasing a free-falling projectile into a
surface container with a downward acceleration less than that of Earth's
gravity. The acceleration of the surface is controlled through the use of an
Atwood machine, or a system of pulleys and counterweights. The starting height
of the surface container and the initial separation distance between the
projectile and surface are variable and chosen to accommodate collision
velocities up to 20 cm/s and effective accelerations of ~0.1 - 1.0 m/s^2.
Accelerometers, placed on the surface container and inside the projectile,
provide acceleration data, while high-speed cameras capture the collision and
act as secondary data sources. The experiment is built into an existing 5.5 m
drop-tower frame and requires the custom design of all components, including
the projectile, surface sample container, release mechanism and deceleration
system. Data from calibration tests verify the efficiency of the experiment's
deceleration system and provide a quantitative understanding of the performance
of the Atwood system.
