Three dimensional critical wetting experiment in commercial zero-gravity space flight

Lauren M Sharp, Purdue University

Abstract

Without gravity, fluids behave differently and present challenges not observed on Earth. As a result, an understanding of microgravity fluid physics is essential in the development of many space technologies ranging from life support systems on the International Space Station to propellant management devices in spacecraft fuel tanks. Microgravity fluids research has been conducted for decades in drop towers, parabolic aircraft, sounding rockets, the Space Shuttle, and the International Space Station. Recently, flight opportunities for microgravity research experiments are becoming available on commercial suborbital vehicles. Advantages of commercial suborbital space flight include low-cost access to the microgravity environment, multiple launch opportunities in a single day, access to experimental hardware up to minutes before launch, and access to experimental data immediately upon landing. In addition, the initial development of many commercial suborbital vehicles was largely for space tourism meaning that safety requirements for manned missions are in place making autonomous control unnecessary and allowing hands-on experimentation during flight. Suborbital space flights also provide significantly more low-gravity time (approximately 3 to 5 minutes) compared to current drop towers. The emerging market for microgravity research in commercial suborbital space-flight has provided an opportunity to explore critical wetting in a three-dimensional geometry. This thesis discusses the design of a microgravity experiment scheduled to launch on New Shepard vehicle designed by Blue Origin, LLC. The experiment includes a 5-inch diameter spherical tank and two rotating vane structures of different thicknesses The design of the tank and vane structures was completed using the Surface Evolverwhich is a computational tool used to model steady-state low-gravity capillary fluids problems. The critical wetting phenomenon in the gap between the vane and the tank wall was studied. The results obtained from Surface Evolver conclude that the capillary behavior of the liquid in the gap is significantly affected by differences in vane thickness, vane width, contact angle, and the non-circular shape of the vane, or vane spiral. Decreasing the thickness of only one vane reduces the liquid climb height in the vane gap of the thinner vane while the liquid climb height increases in the vane gap of the thicker vane. The same result is observed when the vane width is decreased. Increasing the contact angle increases the liquid climb height in the thick vane gap and decreases the liquid climb height in the thin vane gap for vane angles less than 10°. Lastly, increasing the vane gap by increasing the vane spiral causes the liquid climb height in the thick vane gap to decrease while the liquid climb height in the thin vane gap closely follows the baseline until about 10°. The final vane design was chosen based on the conclusions of this work. The thicker vane has a thickness of 0.1, the thinner vane has a thickness of 0.05, and both vanes have a width of 0.2. The vane thicknesses and width are nondimensionalized by the radius of the tank. The vane spiral rate was chosen to be 0.01 rad, the contact angle of the test fluid was determined to be 40° and 25% is the chosen volume fill fraction. Future work for this experiments includes the launch of the experimental hardware on Blue Origin's New Shepard vehicle. Observations of the capillary behavior of the liquid will be recorded via video cameras, and conclusions from the experimental data will be compared to the numerical results presented in this thesis.

Degree

M.S.E.

Advisors

Collicott, Purdue University.

Subject Area

Aerospace engineering

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