Jason D. Frieman's research while affiliated with Georgia Institute of Technology and other places

Publications (30)

Conference Paper
Full-text available
NASA and Aerojet Rocketdyne are developing and qualifying a 12-kW Hall thruster for deep-space mission applications through the Advanced Electric Propulsion System (AEPS) project. The core technology of the thruster derives from the NASA-developed Hall Effect Rocket with Magnetic Shielding (HERMeS), which had a design lifetime of 50 kh at specific...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-1353.vid This work presents a summary of a detailed performance assessment of the Hall Effect Rocket with Magnetic Shielding (HERMeS) Technology Demonstration Unit 3 (TDU-3) thruster at an expanded set of throttle conditions. First, an assessment was performed of TDU3 performance and stability...
Article
This work presents the results of over 6500 h of wear testing completed during the maturation of the NASA 12.5 kW Hall Effect Rocket with Magnetic Shielding. Erosion of the thruster front pole covers was found to be the primary life-limiting mechanism and exhibits strong dependencies on thruster operating condition and material properties. Specific...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-3431.vid This work presents a summary of the first detailed performance assessment of the Advanced Electric Propulsion System (AEPS) Engineering Test Unit 2 (ETU-2) thruster produced by Aerojet Rocketdyne at the throttle conditions most relevant for AEPS application on the Gateway Power and Pr...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-3432.vid During development testing of the 12.5-kW Advanced Electric Propulsion System engineering unit Hall thruster, which is magnetically shielded, a laser-induced fluorescence test was performed. During this test, a third medium-energy ion population was found near the inner front pole cov...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-3406.vid This work adapts manufacturing and metrology industry standards to create a risk-based approach for the determination of electric propulsion performance specifications. The developed process is applied to 208 total thrust measurements acquired using three different NASA Hall Effect Ro...
Conference Paper
This work presents a summary of the first wear test of the 12.5 kW Advanced Electric Propulsion System (AEPS) Engineering Test Unit 2 (ETU-2) thruster produced by Aerojet Rocketdyne. The ETU-2 Wear Test accumulated approximately 730 hours of operation split between the nominal 600 V/12.5 kW condition and the 300 V/6.25 kW condition previously ident...
Conference Paper
This work presents a summary of the detailed characterization test of the 12.5 kW Advanced Electric Propulsion System (AEPS) Engineering Test Unit 2 (ETU-2) thruster produced by Aerojet Rocketdyne. This test campaign had two major goals: to assess the risk of design compliance with thruster requirements and provide a comparison to the previously-te...
Conference Paper
Wear measurements of the inner pole cover in HERMeS have shown as much as ten times higher erosion rates than past numerical simulations predicted. Also, measurements of ion velocity distribution functions (IVDF) suggest that ion heating occurs near the chamfered regions of the acceleration channel and around the inner pole surface. This heating ca...
Conference Paper
In order to meet the requirements for qualification-level testing, NASA Glenn Research Center (GRC) has developed a novel technique to measure pole cover wear in magnetically-shielded Hall thrusters, which allows the thruster to remain in the vacuum testing environment during measurements and eliminates the need to modify key thruster components vi...
Article
The performance of many Hall thrusters has been shown to exhibit sensitivity to background pressure in ground-based test facilities, and this property can have an impact on the prediction of in-space performance. The SPT-140 Hall thruster, similar in design to the SPT-100 thruster, which shows such sensitivity, was subjected to a series of tests to...
Article
Full-text available
The impact of propellant species on the role of the conductive vacuum chamber wall in the discharge circuit of the 200 W T-40 Hall effect thruster is experimentally investigated using xenon and krypton propellants at operating pressures of 1×10−6 torr. Aluminum plates are placed adjacent to, but electrically isolated from, the facility walls downst...
Article
Full-text available
The particle-based coupling between background gas flows in vacuum test facilities and neutral ingestion into Hall effect thrusters is investigated. An analytical model of the facility background flow environment is developed to accommodate facilities with different geometries and pump placements, as well as compute the ingested flow rate of backgr...
Conference Paper
The performance of the Aerojet Rocketdyne T-40 low-power Hall current thruster (HCT) is experimentally characterized with both xenon and krypton propellant. The T-40 HCT is operated at a constant anode flow rate of 11.7 sccm (1.14 mg/s Xe, 0.73 mg/s Kr), discharge voltages of 150 V – 300 V, and discharge powers of 75 W-250 W. The nominal facility o...
Article
Full-text available
Accurate control and measurement of propellant flow to a thruster is one of the most basic and fundamental requirements for operation of electric propulsion systems, whether they be in the laboratory or on flight spacecraft. Hence, it is important for the electric propulsion community to have a common understanding of typical methods for flow contr...
Article
Full-text available
The physical mechanisms that govern the electrical interaction between the Hall-effect-thruster electrical circuit and the conductive vacuum-facility walls are not fully understood. As a representative test bed, an Aerojet Rocketdyne T-140 Hall-effect thruster is operated at 3.05kWand a xenon mass flow rate of 11.6 mg/s with a vacuum facility opera...
Article
Full-text available
The impact of facility conductivity on Hall effect thruster cathode coupling is experimentally investigated. The 3.4 kW Aerojet Rocketdyne T-140 Hall effect thruster operating at a discharge voltage of 300 V, a discharge current of 10.3 A, and an anode flow rate of 11.6 mg/s serves as a representative Hall effect thruster test bed. The nominal faci...
Conference Paper
Full-text available
The role of the electrically conductive vacuum chamber wall in the completion of the discharge circuit of a Hall effect thruster is experimentally investigated. The Aerojet Rocketdyne T-140 laboratory-model Hall effect thruster, operating at a discharge voltage of 300 V, a discharge current of 5.16 A, and an anode flow rate of 5.80 mg/s, serves as...
Conference Paper
Full-text available
Identical helicon plasma sources are characterized in two separate vacuum facilities to examine the impact of facility effects on helicon plasma source performance. A replica of the Madison Helicon eXperiment (MadHeX) is operated inside Vacuum Test Facility-2 (VTF-2) at the Georgia Institute of Technology over a radio frequency (RF) forward power r...

Citations

... The articles in this collection highlight several outstanding physics-based questions related to these devices. Key topics include the nature and impact of large scale ionization-driven plasma oscillations [6]- [11], onset of self-organized, gradient-driven modes [12], microinstabilities and their impact on particle transport [13]- [15], evaluation of lifetime and the processes that govern lifetime [15]- [17], operation on alternative propellants [18], [19], methods for improving testing fidelity [20], the role of variations in magnetic field configuration and thruster geometry on performance [21]- [24], and development of novel diagnostics tools to assess the plasma state [10], [25], [26]. ...
... The second thruster, ETU-2, was used to evaluate thruster performance, stability, thermal, and life characteristics [11,12,20,21,30,38]. Additionally, detailed ion velocity measurements were made via laserinduced fluorescence (LIF) that are used to validate physics-based plasma models of thruster erosion [28,42]. ...
... ETU-1 successfully completed all environmental testing and the facilities and processes were demonstrated to be capable of performing qualification testing. The second thruster, ETU-2, was used to evaluate thruster performance, stability, thermal, and life characteristics [11,12,20,21,30,38]. Additionally, detailed ion velocity measurements were made via laserinduced fluorescence (LIF) that are used to validate physics-based plasma models of thruster erosion [28,42]. ...
... In Ref. [30], a statistics-based methodology was developed and used to derive the AEPS performance specification at the wear test RFCs listed in Table 2. In order to develop a suitably large data set for application of that methodology to the expanded set of RFCs listed in Table 3, a minimum of four performance measurements were acquired at each RFC with measurements spread over several test days and two facility vacuum cycles. ...
... This approach is currently being applied to the 12.5 kW HERMeS thruster for the Advanced Electric Propulsion System [3], the 4.5 kW SPT-140 thruster for the Psyche mission [4], and the 1 kW MaSMi thruster (part of the ASTRAEUS system) [5]. Validation experiments involving plasma measurements in the thruster channel and near plume play a critical role in the modeling process, increasing confidence in the predictive capability of the simulations and supplying information to guide implementation of additional physics when needed [2,6,7]. In recent years, it has become clear that noninvasive optical measurements are the preferred means for obtaining the required validation data, particularly within and upstream of the acceleration region where perturbations from injected probes become unacceptably large [8,9]. ...
... Studies on midpower HETs show that elevated facility pressures allow the thruster to ingest the background neutral gas as propellant, thereby augmenting the measured thrust. Recent investigations by Snyder et al. show that SPT-140 thrust measurements increase from 278 mN to almost 300 mN as the facility pressure increased by an order of magnitude at the constant 4.5 kW, 300 V operating condition [82,108]. In addition, elevated facility pressures can also enhance erosion rates of thruster components due to larger populations of charge-exchange (CEX) ions, change plasma properties of the thruster plume, affect discharge oscillations, and vary the location of the acceleration zone in HETs [199][200][201]. ...
... Many high-power GIEs have endured carbon backsputtering effects on grid erosion rate studies [207,211]. The H6MS and HERMeS TDU-1 were the only highpower HETs that have engaged in such investigations [92,209]. Although there is some progress along this front, there is no consensus on the best practices for measuring backsputtered carbon deposition rates, acceptable facility wall lining materials, or facility internal structure geometries to minimize these contamination effects on thruster lifetime assessments. ...
... Hall thrusters are quickly maturing as a technology to become the most common form of electric propulsion in space. [1] Recent scientific missions such as PSYCHE are now utilizing a Hall thruster as the main propulsion unit for deep-space orbital transits and maneuvering, [2] and large constellations of commercial satellites such as Starlink rely upon Hall thrusters to maintain their orbits. These new developments are brought about by two converging factors in the space industry: the rise of higher power capabilities onboard satellites and the miniaturization of components. ...
... In order to assess these wearout failure modes and also to prepare for the planned qualification life test of the AEPS qualification thruster, wear tests with durations ranging from as short as 10 h [58] to as long as 3.6 kh [59] have been conducted with the H6MS [60,61], HERMeS [62][63][64], and AEPS ETU-2 [11,38]. HERMeS and AEPS wear testing has focused on quantifying known and potentially unknown erosion modes of the discharge chamber, pole covers, and cathode. ...
... The overall HERMeS design incorporates technologies developed over nearly two decades, including a magnetic shielding topology and graphite pole covers for a design lifetime exceeding 23 kh [6,7]. The HERMeS TDU-3 thruster configuration was largely unchanged from that used during the previous Long Duration Wear Test and is shown in Fig. 1 [8,9]. It is important to note that at the time of testing, TDU-3 had accumulated approximately 4,500 hours of total operation. ...