Ingenium 2020
Analytical model validation for melting probe performance using applied computational fluid dynamics Michael Ullmana, b, Michael Durkaa, b, Kevin Glunta, b, and Matthew Barry, PhDa, b Applied Computational Fluid Dynamics Lab, bDepartment of Mechanical Engineering and Materials Science, University of Pittsburgh, PA, USA
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Michael Ullman
Matthew Barry, PhD
Michael Ullman graduated from the University of Pittsburgh in December 2019 with a Bachelor’s degree in Mechanical Engineering and a minor in Physics. He plans to continue his education in the fall by pursuing a Ph.D. in Aerospace Engineering, focusing on computational fluid dynamics and fluid modeling. Dr. Barry’s research focuses on multi-physics modeling of energy systems. This ranges from terrestrial thermal-fluid-electric coupled modeling of waste-heat recovery systems to thermalelectric-mechanical coupled modeling of space power-generation systems, and includes phase-change modeling for extraterrestrial probe design and evaluation.
Significance Statement
NASA Jet Propulsion Laboratory is developing a melting probe to access Europa’s subterranean oceans in search of extraterrestrial life. This research advances the mathematical formulation of the melting process by identifying and quantifying discrepancies between models, ultimately providing insights into how the probe shall be designed to maximize its performance.
Category: Computational research
Keywords: Melting probe, Europa Clipper, Europa Lander, model validation
Abstract
Observations of water vapor plumes ejected from the waterice surface of Jupiter’s moon Europa have prompted scientists to hypothesize that liquid water oceans lie beneath the surface, making Europa a primary focus in the search for extraterrestrial life. NASA Jet Propulsion Laboratory (JPL) is developing plans for its Europa Lander mission, during which a probe will melt through the surface ice sheets to access Europa’s subterranean oceans. An analytical model is being developed by JPL and the University of Pittsburgh to compute the probe’s melting performance envelope, but this model requires corroboration from numerical models. In this project, the boundary conditions of the analytical model were implemented into ANSYS-CFX finite-volume models to evaluate the analytical model’s validity. All of the numerical models exhibited heat flux distributions qualitatively similar to the analytical model on the front and side of the ice cavities, but the cavity shapes differed from what was desired. The greatest discrepancies occurred at the front corner of the probe, suggesting that radial dissipation of axial heat flux must be considered at this location. The results provide insights into the applicability of the analytical model and how the desired melt profile may be achieved.
1. Introduction
Because terrestrial life originated and thrives in Earth’s oceans, biologists hypothesize that the presence of water may be essential for life to emerge. To test this theory, astrobiologists look to examine extraterrestrial environments where water and organic compounds are plentiful. The discovery of life in these environments would help to elucidate how life developed on Earth and answer one of the most profound questions in science—are we alone in the universe? About 400 million miles from Earth, the smallest of the Galilean moons, Europa, orbits its home planet of Jupiter. This moon is notable for its thin, oxygen-rich atmosphere and fractured water-ice surface, which is splotched with red-brown hues believed to result from salt and sulfur compounds discolored by radiation [1]. Recent analyses of data from NASA’s Galileo orbiter suggest that the spacecraft flew through a plume of water vapor when passing close to Europa in 1997 [2]. Water vapor ejections have also been observed by the Hubble Space Telescope, with periodicity consistent with predicted variations in Europa’s tidal forces [3]. Scientists have hypothesized that these plumes originate within a water ocean beneath Europa’s icy surface, making it a primary focus in the search for extraterrestrial life. Because of this promise, NASA is developing plans for its Europa Lander mission, which will consist of a probe landing on and penetrating the moon’s surface to explore its subterranean oceans. The proposed method for penetrating the ice is a combination of drilling and melting—the latter of which will be caused by nuclear heat generation within the probe. Engineers at NASA Jet Propulsion Laboratory (JPL) and researchers at the University of Pittsburgh are developing a system of nondimensional equations—hereafter referred to as the JPL analytical model—to 97