Free surface oscillations of liquid hydrogen in microgravity conditions

• We performed six drop tower tests with liquid parahydrogen.
• The experiment container was a right circular cylinder.
• Pressure and temperature could be recorded and visual access was enabled with an endoscope.
• Several wall temperature gradients were imposed on the cylinder.
• The magnitude of the superheated wall had a great influence on the free surface reorientation.

Experiments were performed to investigate the reorientation behavior and axial sloshing of liquid parahydrogen in a partly filled right circular cylinder due to a step reduction of gravity. Different temperature gradients along the cylinder wall in vertical direction were imposed to examine the influence of a wall superheat on the free surface. Experiments were conducted in the drop tower at the University of Bremen which provides a microgravity time of 4.7 s and a compensated gravity environment of 10−6g0 (acceleration due to gravity). The thermal preparation of the experiments allowed to create defined wall temperature gradients and a stratified or homogenous liquid temperature distribution. Several sensors along the cylinder wall and in the vapor region monitored the temperature. The pressure inside the experiment was recorded and visual access was enabled by an endoscope. The experiments showed that the wall superheat has an influence on the free surface as well as on the temperature and pressure evolutions.