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.
Satellite propulsion spectral signature detection and analysis through Hall effect thruster plume and atmospheric modeling
Space Situational Awareness (SSA) is of utmost importance in today's congested and contested space environment. Satellites must perform orbital corrections for station keeping, devices like high efficiency electric propulsion systems such as a Hall effect thrusters (HETs) to accomplish this are on the rise. The health of this system is extremely important to ensure the satellite can maintain proper position and perform its intended mission. 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 emission lines in xenon and krypton to electron temperature measurements. Ground based observations of these spectral lines could allow the health of the thruster to be determined while the satellite is in operation. Another issue worth considering is the availability of SSA assets for ground-based observations. 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 this, precise atmospheric modeling must be used to pull out the signature. Within the atmosphere, the NIR has a higher transmission ratio and typical HET propellants are approximately 3x the intensity in the NIR versus the visible spectrum making it ideal for ground based observations. The proposed research will focus on developing a model to determine xenon and krypton signatures through the atmosphere and estimate the efficacy through ground-based observations. The model will take power modes, orbit geometries, and satellite altitudes into consideration and be correlated with lab and field observations.
Measurement of population and temperature profiles in an arcjet plume
Emission spectroscopy has been used to investigate arcjet performance. Emission data were obtained near the exit of an intermediate power (5 to 15 kW) hydrogen arcjet for two anode configurations and a total of seven operating conditions. The intensity of the first 9 lines of the hydrogen Balmer series was measured across a vertical slice of the plume and then converted through the Abel inversion to radial distributions of excited state number densities. A nonequilibrium collisionalradiative model was then used to relate these densities to the electron density and temperature profiles. The results of the model indicate that the plasma at the nozzle exit is strongly recombining and that the plume is optically thick to Lyman series radiation. Electron temperatures were very uniform at roughly 0.3 eV over all locations and operating conditions and configurations. The electron densities on center line ranged from 3 to 5 x I O i 4 ~ m ~ . The estimated ionization losses ranged from 6 to 12% of input power and increased with increasing power and with decreasing power-to-flowrate ratio. In addition, the anode with the smaller expansion angle had significantly lower ionization losses. Finally, the ionization losses appear to have an inverse correlation with thermal losses, suggesting a tendency to trade energy between loss modes.