Experimental simulation and assessment of the geysers of icy moons in the laboratory

The Cassini spacecraft, observing the Saturnian system for over 13 years, discovered aspects of the planetary system that were previously unseen. One such discovery is the eruption of geysers (plumes) from the Tiger Stripes on the surface of the icy moon Enceladus. An unexpected liquid water ocean exists underneath Enceladus’ icy crust (Postberg et al. 2018). A consequence of this finding was the complete revision of the habitability of the Solar System. This liquid ocean is propagated through conduits within the crust, and forms plumes when it reaches the surface. The plume material is believed to accelerate supersonically through nozzle-like channels (Schmidt et al. 2008) before being ejected at high speeds from the plume vents. This thesis aims to improve the physical understanding of the interaction between the ocean, icy crust, and the plumes of Enceladus, by experimentally simulating such a plume in the wind tunnel laboratories of TU Delft, and monitoring and analyzing the dynamic physical processes taking place across the experimental setup. A physical analog, separated into regions simulating the ocean, crevasse, and vent of the plume mechanism, is monitored with pressure and temperature sensors, while plume particles are detected with optical tracingtechniques. These observations lead to estimations of the vapor mass flow rate, the outflow Mach number, and the fraction of the plume mass that is condensed. It is found that the ocean conditions can be easily controlled through an adjustable heating power supply. The vapor flow generated by the boiling ocean becomes choked in the crevasse and can attain supersonic velocities. The thermodynamic conditions at the vent of the plume exhibit a greatly varying behavior suggesting that the combined effect of the crevasse geometry and thenucleation of vapor into liquid and icy particles results in considerable diversity in the plume characteristics. Thus, an isentropic description of the plume flow is found to be inadequate, while a Rayleigh flow is found to be feasible. Heat exchange phenomena appear to dominate locally the plume flow, as strong evidence of thermal choking in the crevasse is found. Particles with speeds of up to 426 ± 5 m/s are detected being ejected from the vent of the crevasse, and the maximum fraction of condensed plume mass is found to be 2.94% ± 0.15%. Finally, the possibility of a supersonic plume generated on Enceladus by a crevasse of constant cross-sectional area and cold walls is examined and found to be feasible.Aerospace Engineerin