Very small satellites require very small thrusters. Designing such thrusters requires detailed understanding of fluid mechanics at the micro scale. The Isp Lab maintains imaging and visualization facilities dedicated to exploring surface instabilities and interfacial dynamics of complex liquids at the micro scale. We employ collimated blue laser backlighting and stereo microscopy to visualize effects such as magnetic and electric liquid surface instabilities and micro-jet breakup instabilities. These optical diagnostics can be used to determine the balance of electric, magnetic, and capillary stresses in the deformed fluid interface at the tip of an electrospray thruster. In order to understand fluid physics on the atomic scale we employ imaging techniques much more powerful than optical instruments can achieve. We can insert operating electrospray microthrusters into the specimen imaging chamber of an electron microscope to observe the nano-scale physics within the liquid propellant. We can visualize the molecular motion at the base of the ion jet with detail down to a few nanometers. Using this technique we observe never-before-seen behavior when extreme electric fields as high as 10 Gigavolts/meter are applied to conducting liquid interfaces.
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