Experiments
Our experimental research includes propellant accumulation measurement, characterization of surface deposition and surface impact byproducts, electrospray emitter fabrication using nanoscale additive manufacturing, and design of ESI-MS instrument for future planetary science missions.
Research Areas:
Measuring Propellant Accumulation In-situ
(PhD Student: Carl Geiger)
Carl works to develop novel techniques for directly measuring neutral particles in electrospray thruster plumes and their effects on key operating surfaces using quartz crystal microbalances (QCMs), secondary charged species emission (SSE), time-of-flight mass spectrometry (TOF-MS), as well as a suite of surface characterization diagnostics. This work will inform accurate lifetime predictions for electrospray thrusters, allowing this technology to be leveraged for longer, cheaper, and more ambitious small satellite missions.
Characterizing Surface Deposition
(PhD Student: Stefan Bell)
Stefan is working to examine the deposition of ionic liquids onto surfaces in trace quantities. This work involves the detection and quantification of the deposition. Detection is performed using spectrographic techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), fluorescence spectroscopy, and Raman spectroscopy. Quantification of the deposition includes identifying deposition species, as well as mass estimates for the deposition. Techniques explored for this include Multiple Reaction Monitoring Chromatography (MRM) with Electrospray Ionization Mass Spectrometry (ESI-MS), FT-IR, and Energy Dispersive X-Ray Spectroscopy (EDX). Through judicious application of each of these techniques (and more!), the chemical species deposited on a surface of a spacecraft could be identified and quantified.
Characterizing Surface Impact Byproducts with ESI-MS
(PhD Student: Giuliana Hofheins)
Electrospray thrusters utilize ionic liquid propellants that are composed of complex organic cations and anions, which have important chemical properties compared to the typical noble gas-electric propulsion propellants. While noble gas ion-surface interactions have decades of research due to their nearly ubiquitous use among EP systems, the surface interactions of complex ions are hypothesized to be much different. For example, they may deposit at low energies or form new product ions at high energies. Both experiments and simulations indicate that particles from the plume impact thruster and spacecraft surfaces like the extractor electrode, resulting in propellant accumulation and eventual device failure. However, there is a wide gap in the knowledge of the fundamental physics of these molecular ion-surface collisions at the nanoscale and how they ultimately impact thruster lifetime and performance. ASTRAlab is working to develop time-of-flight secondary ion mass spectrometry as an electrospray diagnostic technique to identify species from ion beam/surface impacts and correlate these findings to thruster lifetime.
Nanoscale Additive Manufacturing of Electrospray Emitters
(PhD Student: Luke D'Cruz)
Design of ESI-MS Instrument for Future Planetary Science Missions
(Post Doc: Dr. Zach Ulibarri)
Zach Ulibarri earned his PhD in Physics at the University of Colorado studying the 'speed limit' of flyby spacecraft looking for complex organic chemistry with impact ionization, finding that at speeds beyond 7 km/s, amino acids begin to fragment at an accelerated rate. He now works on adapting electric propulsion sources to work as the first stage of a new type of spacecraft electrospray ionization (ESI) mass spectrometer. His work also carries over into electric propulsion, where he is using a new method of aiming emitted ESI plumes to study their angular characteristics.