Satellite propulsion spectral signature detection and analysis
Space Situational Awareness (SSA) is of utmost importance in today's space dependent, congested and contested environment. The health of a propulsion system is vital to ensure proper function and thus proper mission placement. Electric propulsion is gaining popularity for satellite propulsion systems due to higher efficiencies, specific impulse, and the savings it offers in both spacecraft mass and launch costs. Electron temperature is a commonly used diagnostic to determine the efficiency of a Hall thruster. Recent papers have coordinated near infrared (NIR) spectral measurements of ionization lines in xenon and krypton to electron temperature measurements. This research will characterize NIR plume emissions for a 600 Watt Hall thruster using both xenon and krypton propellants for a variety of observation angles and operating power levels. By determining spectral differences when altering these variables, it would be possible to identify angle, power level, and propellant in order to provide information on electron temperature and thus efficiency. Although they have a high specific impulse, electric propulsion systems provide lower thrust than chemical alternatives. This means that the firing times needed for spacecraft maneuvers can be on the order of hours to months. This provides an opportunity for this characterization to not only be put to use in chamber experiments but on-orbit as well. Ground-based observations of these spectral lines would allow for identification of the type of thruster as well as the health of the system while the satellite is in operation on-orbit. The current SSA architecture is limited and task saturated. If smaller telescopes, like those at universities, could successfully detect these signatures they could augment data collection for the SSA network. To facilitate data collection, precise atmospheric modeling must be used to identify the signature. Within the atmosphere, the NIR has a higher transmission rate and typical HET propellants are approximately 3x the intensity in the NIR versus the visible spectrum making it ideal for ground based observations. This research will combine emission measurements with atmospheric and plume models to develop a single end-to-end model that will determine xenon and krypton signatures through the atmosphere, discernable differences in power level and viewing angle of Hall thruster systems, and estimate the efficacy through ground-based observations.
Passive optical diagnostic of Xe propelled Hall thrusters. II. Collisional-radiative model
A collisional radiative model is presented for analyzing the xenon-propelled Hall thruster optical radiation based on apparent electron and ion-impact emission cross sections associated with lines in the visible and near-infrared region of the spectrum. The emission cross sections of selected near-infrared emission lines are incorporated in a collisional-radiative model. The effect of stepwise excitation via metastable states on the derived line intensities for emissions from XeI 5p56p(6p′) levels is evaluated. Meanwhile, visible XeII emissions are shown to provide plasma densities at high electron temperature conditions. The electron temperature and spatial ion number density distribution were determined from the luminescence spectra measured in the discharge and plume near-field plasma of the Hall thruster, the TSNIIMASH D-55 anode layer thruster. The results are in good agreement with the probe measurement data and simulations reported in the literature for the same thruster. The analysis of the Hall t...
30 KW Class Arcjet Advanced Technology Transition Development (ATTD)
Abstract : The Arcjet Advanced Technology Transition Demonstration (ATTD) Program developed and demonstrated a flight qualified 30 kW arcjet propulsion flight unit. Once it successfully completed qualification testing, the flight unit was integrated as the Electric Propulsion Space Experiment (ESEX) flight experiment onto the Air Force Advanced Research and Global Observation Satellite (ARGOS). The objectives of the flight unit space test were to measure arcjet plume deposition, electromagnetic interference, thermal radiation, and performance in space. These measurements were chosen to address specific operational issues that are commonly raised for EP systems. There were a total of eight firings conducted over the course of the 60-day mission, for a total duration of 2,023 seconds. All of the demonstration aspects of the experiment were completed successfully and the arcjet, PCU, PFS and overall system operated very well. All of the data analyzed to date indicate the thruster operated nominally, and operated completely independently of the normal operations of the host spacecraft.