Electrospray propulsion devices employ strong electric fields to extract high velocity droplets and molecular ions from a liquid propellant. When these constituents strike downstream surfaces, impact processes can lead to the emission of a diverse set of secondary species, including electrons, atomic ions, molecular ions, and subsidiary droplets. The objective of this research is to examine the emission and transport of secondary species in electrospray thrusters to understand the effects on thruster life, performance, spacecraft interactions, and terrestrial facility effects.

This dissertation presents theoretical, analytical, and experimental investigations of electrospray operation in vacuum facilities to show that secondary species emission (SSE) plays a significant role in the behavior of electrospray thrusters during ground testing. First, an analysis of SSE mechanisms and onset thresholds showed that SSE occurs in the regimes where electrospray thrusters commonly operate. Therefore, SSE must be carefully considered for accurate measurements and determination of performance and life.

A series of experiments were conducted to investigate the consequence of SSE on electrospray thruster operation. A beam target biasing experiment was conducted to demonstrate the impact of SSE on thruster-to-facility coupling, which introduces significant uncertainty in thruster lifetime measurements. A novel “SSE probe” diagnostic was developed and used to obtain the first-ever angular distributions of positive and negative SSE yields for an electrospray thruster. An optical emission spectroscopy study was conducted to show that glow discharges observed in electrospray thrusters during vacuum operation are a consequence of SSE; this observation is in direct contrast to common postulations that glows are intrinsic to electrospray operation.

Two analytical models were developed to study SSE impact on thruster performance and lifetime. The first model was a one-dimensional heat and mass flux analysis of an ionic liquid ion source, which showed that SSE-induced Ohmic dissipation can significantly affect thruster performance. The second model, named the “Electrospray SSE Control-volume Analysis for Resolving Ground Operation of Thrusters” (ESCARGOT) invokes conservation of charge to derive a set of governing equations that describes the emission and transport of secondary species throughout an electrospray thruster and testing facility. The model relies on geometric factors obtained from numerical simulations, and experimentally-obtained SSE yields to correct for SSE-induced current measurement uncertainty in thruster performance and life testing. Therefore, the ESCARGOT model serves as an important link to determine accurate in-space thruster life and performance predictions based on terrestrial qualification testing.

Overall, this work reveals the critical importance of SSE to electrospray thruster performance, life, facility effects, and space interactions; and provides both experimental and modeling techniques to assess their impact for a range of operating and test conditions.

Recent advances in computer vision and image analysis have enabled biological screens of large volumes. Such high-throughput assays increase the likelihood and scope of discovery ultimately leading to functional analysis of a gene or protein. To increase the efficiency of high-throughput screens, computational tools are essential expedite image analysis, models to make sense of the extracted data, and biological assays to characterize the mutation or small molecule. Chemical genomics, the use of small molecules to inactivate proteins, is an advantageous approach when studying a conserved process such as endomembrane trafficking. Endomembrane trafficking spans kingdoms and is important in defense, development, stress response and other vital physiological process. We have taken numerous approaches to study the quantitative behavior of the dynamic endomembrane system to accelerate discovery and better understand these complex phenomena. First, We identified six small molecules altering endomembrane trafficking in tobacco pollen; we characterized their effect on trafficking dynamics using video tracking facilitated by commercially available software giving us insight into intrinsic quantitative properties of the endomembrane system. Next, we wanted to create an automated tool to enable automatic phenotypic screening in Arabidopsis. EndoQuant is an automated computational tool for automatic sub cellular phenotypic analysis. Once this data was collected we developed a model to predict the biological being disrupted based on the cellular phenotype of a fluorescent marker. Using Gaussian Mixture Model, we were able to successfully predict that a subset of small molecules was disrupting endocytic recycling, leading to better experimental design and faster discovery of bioactive molecules. One particular biologically active molecule in Arabidopsis drastically reduced the root length of seedlings. This was found to be a result of cellulose deposition, most likely due to the miss localization of the cellulose synthesis machinery in response to disrupted trafficking membrane. We have analyzed real time membrane dynamics, automated phenotypic analysis, created a predictive model to link a phenotype with a biological process and characterized a small molecule disrupting the transport of a vital protein complex. These tools and methodologies will augment and accelerate the discovery process and our understanding of endomembrane trafficking in plant cells.

This dissertation studies traditional and popular music of the Wixárika (a.k.a. Huichol) people of western Mexico, focusing especially on the phenomenon of Wixárika musicians who intentionally represent themselves as indigenous “Huichol” people yet perform popular Mexican music primarily for non-indigenous audiences. This phenomenon markets ethnic identity within regional and transnational music industries, following in the footsteps of Wixárika people who have successfully inserted their arts and crafts into global markets. The process of becoming indigenous cosmopolitan capitalists is partly the result of direct assimilatory projects directed by early Mexican anthropologists and the indirect outcome of over a century of Huichol identity construction for consumption, aided greatly by foreign ethnographers and other outsiders. On one hand, the commodification of identity through handicrafts, art, and music generates income for the Wixárika people, and the resultant visibility—sometimes international in scale—may strengthen them politically as Indigenous people. Conversely, the process simultaneously supplants some of the very elements they consider central to Wixárika culture. Musicians often leave their homelands to pursue their craft, making it difficult or impossible to participate in community affairs and ceremonies, and leaving their children bereft of Wixárika language and “customs.” Such people who represent the “customs” but do not practice them are sometimes disparaged as “half disqualified” or “Huichol de pirata” (pirated Huichol), illuminating identity’s commodity form. As the first English-language study of Wixárika music, this dissertation examines the paradox of identity commodification, developing a tripartite model of identity that shows the vital (albeit sometimes inadvertent) role of ethnography in defining the essence of the commodity form of Huichol identity.