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Dr. Richard Hofer

Principal Engineer and Supervisor, Electric Propulsion

About

Bio

Dr. Richard R. Hofer, Principal Engineer and Supervisor of the Electric Propulsion (EP) Group at JPL, is recognized by JPL, NASA, and his professional colleagues as a world leading expert in Hall thruster technology. Since joining JPL in 2005, Dr. Hofer’s research and leadership have led to lasting, high-impact innovations that have been translated in to Hall thrusters that are enabling the next phase of robotic and human exploration of the solar system. As Supervisor, he is responsible for ensuring the technical excellence of the EP discipline as implemented on JPL missions and for formulating and executing a strategy for the long-term growth of EP at JPL. As Principal Engineer, he is the technology lead responsible for the development and qualification of Hall thruster systems for deep space missions. These activities include the development of advanced thrusters and plasma diagnostics concurrent with experimental and numerical investigations of thruster performance, plasma properties, and lifetime.

He is an internationally-recognized expert in Hall thruster design, having designed several advanced Hall thrusters ranging in power from 1 to 100 kW. Thruster technologies developed by Dr. Hofer have led to the award of multiple technology programs valued cumulatively at several hundred million dollars that are now used in every in-house Hall thruster development of the United States Government.

Dr. Hofer is an AIAA Fellow, serves on the Board of Directors of the Electric Rocket Propulsion Society, and former Chair of the AIAA Electric Propulsion Technical Committee. He has received numerous honors and awards, including the NASA Exceptional Engineering Achievement Medal, the JPL Lew Allen Award for Excellence, and five Best Paper awards from AIAA and the International Electric Propulsion Conference. He has 9 patents and over 180 technical publications in the field of electric propulsion.

Education

2004 Ph.D., Aerospace Engineering (Gas Dynamics), University of Michigan

2000 M.S.E., Aerospace Engineering (Gas Dynamics), University of Michigan

1998 B.S.E., Aerospace Engineering (Summa Cum Laude), University of Michigan

1998 B.S.E., Mechanical Engineering (Summa Cum Laude), University of Michigan

Research Interests

Electric propulsion systems, Hall thrusters, Plasma Diagnostics

Experience

Professional Experience

  • Principal Engineer, Electric Propulsion Group (353B), Propulsion and Materials Engineering Section (353), Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (August 2020 – Present)
  • Supervisor, Electric Propulsion Group (353B), Propulsion and Materials Engineering Section (353), Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (April 2017 – Present)
    • Responsible for ensuring the technical excellence of the Electric Propulsion discipline as implemented on JPL missions
    • Responsible for formulating and executing a strategy for the long-term growth of Electric Propulsion at JPL
  • Technical Group Lead, Electric Propulsion Group (353B), Propulsion and Materials Engineering Section (353), Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (December 2015 – March 2017)
    • Technical Lead assisting the Group Supervisor of the Electric Propulsion group at JPL
    • Work with the GS and Section Staff to formulate and execute a vision of the EP group’s future
    • Responsible for guiding and setting the priorities of the experimental work in the group
  • Senior Engineer V, Electric Propulsion Group (353B), Propulsion and Materials Engineering Section (353), Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (April 2005 – present)
    • Lead for Hall thruster development providing technical leadership to focus JPL expertise in design, testing, plasma diagnostics, numerical simulation, and flight systems engineering.
  • Task Manager, High-Power Hall Thruster Development for Nuclear Electric Propulsion for NASA’s Space Nuclear Propulsion Office (July 2024 – present)
  • Subject Matter Expert for Electric Propulsion Implementation, INCUS mission, 2022-present
  • Co-Investigator, “Advancing Electric Propulsion Technology with 3D Printing (AdEPT3D),” JPL Topical R&TD Award, (Oct 2022 – Sep 2024)
  • Principal Investigator, “A Deep-Throttling, High Specific Impulse Hall Thruster
    Enabling the Next Generation of Space Exploration,” JPL Topical R&TD Award, (Oct 2021 – Sep 2023)
    • Developed the 3,000 s specific impulse H10, which is the most efficient magnetically shielded Hall thruster in the world.
  • Lead for Thruster Development of the Hall Effect Rocket with Magnetic Shielding (HERMeS). (Oct 2014-March 2022)
    • Led a multi-center team from JPL and GRC working with Aerojet Rocketdyne through Critical Design Review (CDR) of a 12 kW Hall thruster that is scheduled to fly on NASA’s Power and Propulsion Element
    • Responsible for leading a team of 15 engineers at GRC and JPL in the development of the 12.5 kW HERMeS thruster.
    • Responsible for insight/oversight of the flight thrusters being developed by Aerojet Rocketdyne under the Advanced Electric Propulsion System contract.
  • Principal Investigator, “Hall Thruster Stability at Low Power and High Specific Impulse,” JPL SURP award with the University of Michigan, (Oct 2019 – Sep 2022)
  • Co-Investigator, “Advanced Materials for Electric Propulsion,” JPL Topical R&TD, (Oct 2019 – Apr 2022)
  • Co-Investigator, “XR-100 Hall Thruster System Demonstration.” Aerojet/U of Michigan/JPL/GRC team to develop a 100 kW Nested Hall thruster system to TRL 5. (Jan 2016 – Sept 2019)
  • Principal Investigator, Project H9
    • Lead for the design, fabrication, and test of the magnetically shielded H9 Hall thruster in a collaboration between JPL, the University of Michigan, AFRL, and Georgia Tech. (2016-2019)
  • Principal Investigator, “Long-life, High-Isp Hall Thruster Technology for Primitive Bodies,” Strategic Initiative aimed at qualifying the commercial XR-5 and SPT-140 Hall thrusters for deep-space applications. JPL was awarded the Discovery mission Psyche in 2016 that includes the use of the SPT-140. (2012 – 2015)
  • Lead for high-power Hall thruster technology development for the STMD In-Space Propulsion Technology Project at JPL (2011 – Sept 2014)
    • JPL lead for the joint design of a 15 kW Hall thruster with GRC
    • Led the team demonstrating low erosion operation of a magnetically shielded Hall thruster operating at 3000 s Isp over a 113 h wear test. First ever demonstration of a high-Isp Hall thruster with erosion rates low enough to be relevant to deep space missions.
    • Team member of a U of Michigan/AFRL/GRC/JPL effort to design, fabricate, and test an 80 kW nested Hall thruster
  • Principal Investigator, “Intra-Channel Discharge Coupling Induced Plasma Oscillations and Electron Transport in Nested-Channel Hall Thrusters,” JPL SURP award with the University of Michigan, (Oct 2011 – Sep 2012)
  • Co-Investigator, “Conducting Wall Hall thrusters,” JPL Spontaneous R&TD award. (2012)
  • Principal Investigator, “Nested Hall Thruster with Extremely High Power and Specific Impulse Throttling Capability,” JPL Spontaneous R&TD award. (2011)
  • Co-Investigator, “Breakthrough Hall Thruster Technology with Extremely Long Service Life for High-Throughput JPL/NASA Missions. Topical R&TD effort to develop magnetic shielding in Hall thrusters in order to radically improve lifetime. Responsible for developing thruster designs capable of achieving erosion free operation and validating the design in the laboratory. (2010-2011)
  • Developed numerical simulations of Hall thruster plasma and erosion processes. Licenses for JPL’s version of HPHall-2 have been granted to organizations in government, universities, and industry. (2006-2008)
  • Principal Investigator, Project H6
    • Provided technical leadership and program management in the design, fabrication, and testing of the 6 kW H6 Hall thruster in a collaboration between AFRL, U of Michigan, and JPL that resulted in the world’s most efficient Hall thruster. (2006)
  • Established high-power Hall thruster testing and diagnostic capability at JPL. (2005)
    • Principal Investigator, Pulsed Plasma Lubricator (PPL). Topical R&TD that developed the PPL for the in situ replenishment of dry lubricants in extreme environments. (2009-2011)

Achievements

Awards & Recognitions

  • Professional Society Fellowship | Fellow of the American Institute of Aeronautics and Astronautics (AIAA) | For revolutionizing Hall thruster design and pioneering leadership in electric propulsion, enabling groundbreaking space missions not previously possible. (2024)
  • JPL Principal Designation | 353B - Electric Propulsion (2020)
  • NASA Award | Space Technology Mission Directorate Space Technology Award for the 12.5 kW Hall Thruster Team | NASA STMD (2017)
  • NASA Award | For design of the Hall Thruster Propulsion System for the SEP Technology Demonstration Mission. | Steven V. Szabo Engineering Excellence Award (2015)
  • Professional Society and External Organization Awards | American Institute of Aeronautics and Astronautics (AIAA) | Electric Propulsion Outstanding Technical Achievement Award, "For the identification, development, and demonstration of Magnetic Shielding in Hall Thrusters" (2014)
  • The Lew Allen Award for Excellence | For outstanding technical contributions and leadership in establishing JPL as a world leader in Hall thruster research and development (2011)
  • NASA Award | Exceptional Engineering Achievement Medal | For outstanding technical leadership in efforts to flight-qualify commercial Hall thrusters for NASA/JPL science missions. (2011)

Publications

Journal Articles
  1. Jorns, B.A., Dale, E., Hofer, R.R., “Mode transitions in a magnetically shielded Hall thruster. I. Experimentally informed model,” Journal of Applied Physics, 136, 053301, August 2024
  2. Jorns, B.A., Byrne, M., Roberts, P., Su, L., Dale, E., Hofer, R.R., “Mode transitions in a magnetically shielded Hall thruster. II. Stability criterion,” Journal of Applied Physics, 136, 053302, August 2024
  3. Chari, C. S., McEnerney, B. W., Hofer, R. R., Wollmershauser, J. A., Gorzkowski, E. P., Faber, K. T., “High-temperature carbothermal synthesis and characterization of graphite/h-BN biomaterials,” Journal of the American Ceramic Society, 1-15, 2022. https://doi.org/10.1111/jace.18927
  4. Firdosy, S., Ury, N., Borgonia, J. P., McEnerney, B., Conversano, R., Hofer, R., Hermann, A., Ucar, H., Ravi, V. A., and Dillon, R. P., "Processing–Microstructure–Property Relationships in a Laser‐Deposited Fe‐Co‐V Alloy," Advanced Engineering Materials 2100931 (2021).
  5. Frieman, J. D., Gilland, J. H., Kamhawi, H., Mackey, J., Williams, G. J., Hofer, R. R., and Peterson, P. Y., "Wear Trends of the 12.5 kW HERMeS Hall Thruster," Journal of Applied Physics 130, 14 (2021).
  6. Chaplin, V. H., Lobbia, R. B., Lopez Ortega, A., Mikellides, I. G., Hofer, R. R., Polk, J. E., and Friss, A. J., "Time-Resolved Ion Velocity Measurements in a High-Power Hall Thruster Using Laser-Induced Fluorescence with Transfer Function Averaging," Applied Physics Letters 116, 23 (2020).
  7. Chaplin, V. H., Jorns, B. A., Lopez Ortega, A., Mikellides, I. G., Conversano, R. W., Lobbia, R. B., and Hofer, R. R., “Laser-induced fluorescence measurements of acceleration zone scaling in the 12.5 kW HERMeS Hall thruster,” Journal of Applied Physics, 124, 183302 (2018).
  8. Conversano, R. W., Goebel, D. M., Hofer, R. R., Mikellides, I. G., and Wirz, R. E., "Performance Analysis of a Low-Power Magnetically Shielded Hall Thruster: Experiments," Journal of Propulsion and Power 33, 4, 975-983 (2017).
  9. Conversano, R. W., Goebel, D. M., Mikellides, I. G., Hofer, R. R., and Wirz, R. E., "Performance Analysis of a Low-Power Magnetically Shielded Hall Thruster: Computational Modeling," Journal of Propulsion and Power 33, 4, 992-1001 (2017).
  10. Sekerak, M. J., Gallimore, A.D., Brown, D.L., Hofer, R.R., Polk, J.E., “Mode Transitions in Hall-Effect Thrusters Induced by Variable Magnetic Field Strength,” Journal of Propulsion and Power, 32, 4, 903-917 (2016).
  11. Sekerak, M. J., Longmier, B. W., Gallimore, A. D., Brown, D. L., Hofer, R. R., and Polk, J. E., "Azimuthal Spoke Propagation in Hall Effect Thrusters," IEEE Transactions on Plasma Science 43, 1, 72-85 (2015).
  12. Conversano, R. W., Goebel, D. M., Hofer, R. R., Matlock, T. S., and Wirz, R. E., "Development and Initial Testing of a Magnetically Shielded Miniature Hall Thruster," IEEE Transactions on Plasma Science 43, 1, 103-117 (2015).
  13. Goebel, D. M., Hofer, R. R., Mikellides, I. G., Katz, I., Polk, J. E., and Dotson, B. N., "Conducting Wall Hall Thrusters," IEEE Transactions on Plasma Science 43, 1, 118-126 (2015).
  14. Oh, D. Y., Snyder, J. S., Goebel, D. M., Hofer, R. R., and Randolph, T. M., "Solar Electric Propulsion for Discovery-Class Missions," Journal of Spacecraft and Rockets, 51, 6, 1822-1835 (2014).
  15. Mikellides, I. G., Hofer, R. R., Katz, I., and Goebel, D. M., "Magnetic Shielding of Hall Thrusters at High Discharge Voltages," Journal of Applied Physics, 116, 053302 (2014).
  16. Jorns, B. A. and Hofer, R. R., "Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster," Physics of Plasmas 21, 5, 053512 (2014).
  17. Snyder, J. S., Brophy, J. R., Hofer, R. R., Goebel, D. M., and Katz, I.. "Experimental Investigation of a Direct-Drive Hall Thruster and Solar Array System," Journal of Spacecraft and Rockets, Vol. 51, No. 1, 360-373 (2014).
  18. Mikellides, I. G., Katz, I., Hofer, R. R., and Goebel, D. M., “Magnetic Shielding of a Laboratory Hall Thruster, Part I: Theory and Validation,” Journal of Applied Physics, 115, 043303 (2014).
  19. Hofer, R. R., Goebel, D. M., Mikellides, I. G., and Katz, I., “Magnetic Shielding of a Laboratory Hall Thruster Part II: Experiments,” Journal of Applied Physics, 115, 043304 (2014).
  20. Mikellides, I. G., Katz, I., Hofer, R. R., and Goebel, D. M., "Magnetic Shielding of Walls from the Unmagnetized Ion Beam in a Hall Thruster," Applied Physics Letters 102, 2, 023509 (2013).
  21. Hofer, R. R. and Randolph, T. M., "Mass and Cost Model for Selecting Thruster Size in Electric Propulsion Systems," Journal of Propulsion and Power 29, 1, 166-177 (2013).
  22. Goebel, D. M., Jameson, K. K., and Hofer, R. R., "Hall Thruster Cathode Flow Impact on Coupling Voltage and Cathode Life," Journal of Propulsion and Power 28, 2, 355-363 (2012).
  23. Snyder, J. S., Goebel, D. M., Hofer, R. R., Polk, J. E., Wallace, N. C., Simpson, H., "Performance Evaluation of the T6 Ion Engine," Journal of Propulsion and Power 28, 2, 371-379 (2012).
  24. Huang, W., Gallimore, A. D., and Hofer, R. R., "Neutral Flow Evolution in a 6-kW Hall Thruster," Journal of Propulsion and Power 27, 3, 553-563 (2011).
  25. Mikellides, I. G., Katz, I., Hofer, R. R., Goebel, D. M., De Grys, K. H., and Mathers, A., "Magnetic Shielding of the Acceleration Channel in a Long-Life Hall Thruster," Physics of Plasmas 18, 033501 (2011).
  26. Reid, B. M., Gallimore, A. D., Hofer, R. R., Li, Y., and Haas, J. M., "Anode Design and Verification for a 6-kW Hall Thruster," JANNAF Journal of Propulsion and Energetics 3, 1, 29-43 (2010).
  27. Shastry, R., Hofer, R. R., Reid, B. M., and Gallimore, A. D., "Method for Analyzing ExB Probe Spectra from Hall Thruster Plumes," Review of Scientific Instruments 80, 063502 (2009).
  28. Hofer, R. R., Johnson, L. K., Goebel, D. M., and Wirz, R. E., "Effects of Internally-Mounted Cathodes on Hall Thruster Plume Properties," IEEE Transactions on Plasma Science 36, 5, 2004-2014 (2008).
  29. Katz, I., Hofer, R. R., and Goebel, D. M., "Ion Current in Hall Thrusters," IEEE Transactions on Plasma Science 36, 5, 2015-2024 (2008).
  30. Hofer, R. R., Jankovsky, R.S., and Gallimore, A. D., "High-Specific Impulse Hall Thrusters, Part 1: Influence of Current Density and Magnetic Field," Journal of Propulsion and Power 22 (4), 721-731 (2006).
  31. Hofer, R. R. and Gallimore, A. D., "High-Specific Impulse Hall Thrusters, Part 2: Efficiency Analysis," Journal of Propulsion and Power 22 (4), 732-740 (2006).
  32. Walker, M. L. R., Hofer, R. R., and Gallimore, A. D., "Ion Collection in Hall Thruster Plumes," Journal of Propulsion and Power 22 (1), 205-209 (2006).
  33. Walker, M. L. R., Victor, A. L., Hofer, R. R., and Gallimore, A. D., "Effect of Backpressure on Ion Current Density Measurements in Hall Thruster Plumes," Journal of Propulsion and Power 21 (3), 408-415 (2005).
Conference Papers
  1. Hofer, R. R., Simmonds, J. B., Goebel, D. M., Steinkraus, J. M., and Payman, A. R., "The H10 High Power Density Hall Thruster," Presented at the 38th International Electric Propulsion Conference, IEPC-2024-515, Toulouse, France, June 23-28, 2024.
  2. Simmonds, J. B., Hofer, R. R., Firdosy, S., Daimaru, T., Smith, E. F., Roberts, S., Wexler, T., Dillon, R. P., and Goebel, D. M., "Thermal Management and Performance of the H10 High Power Density Hall Thruster," Presented at the 38th International Electric Propulsion Conference, IEPC-2024-257, Toulouse, France, June 23-28, 2024.
  3. Chari, C. S., Faber, K. T., Hofer, R. R., McEnerney, B. W., Arestie, S. M., Lobbia, R. B., and Marrese-Reading, C. M., "Evaluation of Graphite/h-BN Bimaterials for Electric Propulsion," Presented at the 38th International Electric Propulsion Conference, IEPC-2024-236, Toulouse, France, June 23-28, 2024.
  4. Simmonds, J. B., Chaplin, V. H., Byrne, M. P., Goebel, D. M., Lobbia, R. B., Hofer, R. R., and Conversano, R. W., "Magnetically Shielded Miniature Hall Thruster: Flight Qualification, LIF, and Krypton Performance," AIAA-2024-2166, January 2024.
  5. Hofer, R., Kamhawi, H., Peterson, P., Polk, J., Welander, B., Inaba, D., Blackner, G., Ferraiuolo, B., Frieman, J., Lobbia, R., Chaplin, V., Zubair, J., and Branch, N., "Development and Qualification of a 12-kW Hall Thruster for Deep-Space Missions," Presented at the 73rd International Astronautical Congress, IAC-22-C4-5-15, Paris, France, September 18-22, 2022.
  6. Hofer, R. R., Lobbia, R., and Arestie, S., "Performance of a Conducting Wall, Magnetically Shielded Hall Thruster at 3000-s Specific Impulse," Presented at the 37th International Electric Propulsion Conference, IEPC-2022-401, Cambridge, MA, June 19-23, 2022.
  7. Jorns, B. A., Byrne, M., Roberts, P., Su, L., Dale, E., and Hofer, R. R., "Prediction and Mitigation of the Mode Transition in a Magnetically Shielded Hall Thruster at High-Specific Impulse and Low Power," Presented at the 37th International Electric Propulsion Conference, IEPC-2022-372, Cambridge, MA, June 19-23, 2022.
  8. Frieman, J. D., Kamhawi, H., Mackey, J., Peterson, P. Y., Gilland, J. H., Hofer, R. R., Inaba, D., Dao, H., Branch, N. A., and Welander, B., "Extended Wear Testing of the 12-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster," Presented at the 37th International Electric Propulsion Conference, IEPC-2022-362, Cambridge, MA, June 19-23, 2022.
  9. Johnson, I., Zuo, L., Feng, C., Nelson, N., Bass, K., Aghazadeh, F., Myers, J., Corey, R., Gilland, J. H., Frieman, J., Gray, T., Kamhawi, H., Mackey, J., Dinca, D. et al., "PPE Electric Propulsion Advancing to CDR: 12-kW String," Presented at the 37th International Electric Propulsion Conference, IEPC-2022-467, Cambridge, MA, June 19-23, 2022.
  10. Frieman, J. D., Kamhawi, H., Mackey, J., Haag, T. W., Peterson, P. Y., and Hofer, R. R., "Expanded Performance Characterization of the NASA HERMeS Hall Thruster," AIAA-2022-1353, January 2022.
  11. Frieman, J. D., Mackey, J., Kamhawi, H., Peterson, P. Y., and Hofer, R. R., "Risk-Based Methodology for the Determination of Hall Thruster Performance Specifications," AIAA-2021-3406, Aug 2021.
  12. Frieman, J. D., Kamhawi, H., Mackey, J., Peterson, P. Y., Hofer, R. R., Inaba, D., Dao, H., Branch, N., and Welander, B., "Extended Performance Characterization of the 12.5-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster," AIAA-2021-3431, Aug 2021.
  13. Huang, W., Frieman, J. D., Kamhawi, H., Peterson, P. Y., Hofer, R. R., Branch, N. A., and Dao, H., "Ion Velocity Characterization of the 12.5-kW Advanced Electric Propulsion System Engineering Hall Thruster," AIAA-2021-3432, Aug 2021.
  14. Frieman, J. D., Kamhawi, H., Huang, W., Mackey, J., Ahern, D., Peterson, P., Gilland, J., Hall, S. J., Hofer, R. R., Branch, N. A., Dao, H., Inaba, D., and Welander, B., "Performance of the 12.5-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster," Presented at the 11th JANNAF Spacecraft Propulsion Joint Subcommittee Meeting, Virtual Conference, June 7-17, 2021.
  15. Kamhawi, H., Frieman, J. D., Huang, W., Mackey, J., Ahern, D., Haag, T., Peterson, P., Gilland, J., and Hofer, R., "Performance, Stability, and Throttling of the 12.5-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster," Presented at the 11th JANNAF Spacecraft Propulsion Joint Subcommittee Meeting, Virtual Conference, June 7-17, 2021.
  16. Frieman, J. D., Kamhawi, H., Huang, W., Mackey, J., Ahern, D. M., Peterson, P. Y., Gilland, J. H., Hall, S. J., Hofer, R. R., Inaba, D., Dao, H., Zubair, J., Neuhoff, J., and Branch, N., "Wear Test of the 12.5-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster," AIAA-2020-3625, August 2020.
  17. Frieman, J. D., Kamhawi, H., Huang, W., Mackey, J., Ahern, D. M., Peterson, P. Y., Gilland, J. H., Hall, S. J., Hofer, R. R., Inaba, D., Dao, H., Zubair, J., Neuhoff, J., and Branch, N., "Characterization Test of the 12.5-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster," AIAA-2020-3626, August 2020.
  18. Zubair, J., Dao, H., Branch, N., Inaba, D., Welander, B., Frieman, J., Kamhawi, H., Lobbia, R., and Hofer, R., "Development of a 12.5-kW Hall Thruster for the Advanced Electric Propulsion System," AIAA-2020-3628, August 2020.
  19. Snyder, J. S., Chaplin, V. H., Goebel, D. M., Hofer, R. R., Ortega, A. L., Mikellides, I. G., Kerl, T., Lenguito, G., Aghazadeh, F., and Johnson, I., "Electric Propulsion for the Psyche Mission: Development Activities and Status," AIAA-2020-3607, August 2020.
  20. Frieman, J. D., Mackey, J., Kamhawi, H., Peterson, P. Y., Herman, D., Gilland, J., and Hofer, R., "Performance and Wear of the HERMeS Hall Thruster with a Composite Pole Cover," Presented at the 10th JANNAF Spacecraft Propulsion Joint Subcommittee Meeting, Tampa, FL, Dec 9-13, 2019.
  21. Mackey, J., Salem, J., Stanford, M., Kamhawi, H., McEnerney, B., and Hofer, R., "Lot-to-Lot Variation of Boron Nitride Materials for Hall Thruster Discharge Channels," Presented at the 10th JANNAF Spacecraft Propulsion Joint Subcommittee Meeting, Tampa, FL, Dec 9-13, 2019.
  22. Hofer, R., Lobbia, R., Chaplin, V., Lopez Ortega, A., Mikellides, I., Polk, J., Kamhawi, H., Frieman, J., Huang, W., Peterson, P., and Herman, D., "Completing the Development of the 12.5 kW Hall Effect Rocket with Magnetic Shielding (HERMeS)," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-193, University of Vienna, Austria, September 15-20, 2019.
  23. Conversano, R. W., Barchowsky, A., Lobbia, R. B., Chaplin, V. C., Lopez Ortega, A., Loveland, J. A., Lui, A. D., Becatti, G., Reilly, S. W., Goebel, D. M., Snyder, J. S., Hofer, R. R., Randolph, T. M., Mikellides, I. G. et al., "Overview of the Ascendant Sub-kW Transcelestial Electric Propulsion System (Astraeus)," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-282, University of Vienna, Austria, September 15-20, 2019.
  24. Cusson, S. E., Hofer, R. R., Goebel, D. M., Georgin, M. P., Vazsonyi, A. R., Jorns, B. A., Gallimore, A. D., and Boyd, I. D., "Development of a 30-kW Class Magnetically Shielded Nested Hall Thruster," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-266, University of Vienna, Austria, September 15-20, 2019.
  25. Chaplin, V. H., Conversano, R. W., Lopez Ortega, A., Mikellides, I. G., Lobbia, R. B., and Hofer, R. R., "Ion Velocity Measurements in the Magnetically Shielded Miniature (Masmi) Hall Thruster Using Laser-Induced Fluorescence," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-531, University of Vienna, Austria, September 15-20, 2019.
  26. Peterson, P. Y., Herman, D., Kamhawi, H., Frieman, J., Huang, W., Verhey, T., Dinca, D., Boomer, K., Pinero, L., Criswell, K., Hall, S., Birchenough, A., Gilland, J., Hofer, R. et al., "Overview of Nasa's Solar Electric Propulsion Project," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-836, University of Vienna, Austria, September 15-20, 2019.
  27. Chaplin, V. H., Lobbia, R. B., Lopez Ortega, A., Mikellides, I. G., Roberts, P. J., Peter, J. S., Hofer, R. R., Polk, J. E., and Friss, A. J., "Spatiotemporally Resolved Ion Velocity Distribution Measurements in the 12.5 kW HERMeS Hall Thruster," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-532, University of Vienna, Austria, September 15-20, 2019.
  28. Frieman, J. D., Kamhawi, H., Peterson, P. Y., Herman, D., Gilland, J., and Hofer, R., "Impact of Facility Pressure on the Wear of the NASA HERMeS Hall Thruster," Presented at the 36th International Electric Propulsion Conference, IEPC-2019-714, University of Vienna, Austria, September 15-20, 2019.
  29. Frieman, J. D., Kamhawi, H., Mackey, J., Haag, T., Peterson, P. Y., Herman, D. A., Gilland, J., and Hofer, R. R., "Completion of the Long Duration Wear Test of the NASA HERMeS Hall Thruster," AIAA-2019-3895, August 2019.
  30. Shark, S. W., Hall, S. J., Jorns, B. A., Hofer, R. R., and Goebel, D. M., "High Power Demonstration of a 100 kW Nested Hall Thruster System," AIAA-2019-3809, August 2019.
  31. Lobbia, R. B., Polk, J. E., Hofer, R. R., Chaplin, V. H., and Jorns, B. A., "Accelerating 23,000 Hours of Ground Test Backsputtered Carbon on a Magnetically Shielded Hall Thruster," AIAA-2019-3898, August 2019.
  32. Lobbia, R. B., Conversano, R. W., Reilly, S., Hofer, R. R., and Sorensen, R., "Environmental Testing of the HERMeS TDU-2 Hall Thruster," AIAA-2018-4646, July 2018.
  33. Frieman, J. D., Peterson, P. Y., Gilland, J. H., Kamhawi, H., Williams, G., Herman, D. A., and Hofer, R. R., "Long Duration Wear Test of the NASA HERMeS Hall Thruster," AIAA-2018-4645, July 2018.
  34. Frieman, J. D., Ahern, D., Williams, G., Mackey, J., Haag, T., Huang, W., Kamhawi, H., Herman, D. A., Peterson, P. Y., Gilland, J. H., and Hofer, R. R., "In-Situ Diagnostic for Assessing Hall Thruster Wear," AIAA-2018-4721, July 2018.
  35. Jorns, B. A., Gallimore, A. D., Hall, S. J., Peterson, P. Y., Gilland, J. E., Goebel, D. M., Hofer, R. R., and Mikellides, I., "Update on the Nested Hall Thruster Subsystem for the Nextstep XR-100 Program," AIAA-2018-4418, July 2018.
  36. Mackey, J., Salem, J., Kamhawi, H., McEnerney, B., Hofer, R., Johnson, M., Faber, K., and Peterson, P., "Evaluation of Boron Nitride Materials for Hall Thruster Discharge Channels," Presented at the 65th JANNAF Propulsion Meeting, Long Beach, CA, May 21-24, 2018.
  37. Peterson, P. Y., Frieman, J., Kamhawi, H., Williams, G., Herman, D., Gilland, J., and Hofer, R., "NASA HERMeS Hall Thruster Long Duration Wear Test," Presented at the 65th JANNAF Propulsion Meeting, Long Beach, CA, May 21-24, 2018.
  38. Frieman, J. D., Williams, G., Kamhawi, H., Sarver-Verhey, T., Herman, D., Peterson, P., Gilland, J., and Hofer, R., "Impact of Cathode and Keeper Configuration on HERMeS Thruster Operation," Presented at the 65th JANNAF Propulsion Meeting, Long Beach, CA, May 21-24, 2018.
  39. Schmidt, G., Jacobson, D., Patterson, M., Ganapathi, G., Brophy, J., and Hofer, R., "Electric Propulsion Research and Development at NASA," Presented at the Space Propulsion 2018 Conference, SP2018-389, Seville, Spain, May 14-18, 2018.
  40. De Groh, H. C., Geng, S. M., Niedra, J. M., and Hofer, R. R., "Magnetic Properties of Fe-49co-2v Alloy and Pure Fe at Room and Elevated Temperatures," NASA Technical Memorandum, NASA/TM-2018-219872, April 2018.
  41. Hofer, R., Polk, J., Mikellides, I., Lopez Ortega, A., Conversano, R., Chaplin, V., Lobbia, R., Goebel, D., Kamhawi, H., Verhey, T., Williams, G., Mackey, J., Huang, W., Yim, J. et al., "Development Status of the 12.5 kW Hall Effect Rocket with Magnetic Shielding (HERMeS)," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-231, Atlanta, GA, Oct. 8 - 12, 2017, 2017.
  42. Hofer, R. R., Cusson, S. E., Lobbia, R. B., and Gallimore, A. D., "The H9 Magnetically Shielded Hall Thruster," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-232, Atlanta, GA, Oct. 8-12, 2017, 2017.
  43. Cusson, S. E., Hofer, R. R., Lobbia, R. B., Jorns, B. A., and Gallimore, A. D., "Performance of the H9 Magnetically Shielded Hall Thrusters," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-239, Atlanta, GA, Oct. 8-12, 2017.
  44. Cusson, S. E., Hall, S. J., Hofer, R. R., Jorns, B. A., and Gallimore, A. D., "The Impact of Magnetic Field Coupling between Channels in a Nested Hall Thruster," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-507, Atlanta, GA, Oct. 8-12, 2017.
  45. Lev, D., Myers, R. M., Lemmer, K. M., Kolbeck, J., Keidar, M., Koizumi, H., Liang, H., Yu, D., Schonherr, T., Gonzalez Del Amo, J., Choe, W., Albertoni, R., Hoskins, A., Yan, S., Hart, W., Hofer, R., et al., "The Technological and Commercial Expansion of Electric Propulsion in the Past 24 Years," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-242, Atlanta, GA, Oct. 8-12, 2017.
  46. Jackson, J., Allen, M., Myers, R., Hoskins, A., Soendker, E., Welander, B., Tolentino, A., Hablitzel, S., Hall, S., Gallimore, A., Jorns, B., Hofer, R., Goebel, D., and Pencil, E., "100 kW Nested Hall Thruster System Development," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-219, Atlanta, GA, Oct. 8-12, 2017.
  47. Jackson, J., Allen, M., Myers, R. M., Soendker, E., Welander, B., Tolentino, A., Hablitzel, S., Yeatts, C., Xu, S., Sheehan, C., Cardin, J., Snyder, J. S., Hofer, R. R., Tofil, T. et al., "13 kW Advanced Electric Propulsion Flight System Development and Qualification," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-223, Atlanta, GA, Oct. 8 - 12, 2017, 2017.
  48. Herman, D. A., Tofil, T., Santiago, W., Kamhawi, H., Polk, J. E., Snyder, J. S., Hofer, R. R., Picha, F., Jackson, J., and Allen, M., "Overview of the Development and Mission Application of the Advanced Electric Propulsion System (AEPS)," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-284, Atlanta, GA, Oct. 8 - 12, 2017, 2017.
  49. Chaplin, V. H., Conversano, R. W., Lobbia, R. B., Lopez Ortega, A., Mikellides, I. G., Hofer, R. R., and Jorns, B. A., "Laser Induced Fluorescence Measurements of the Acceleration Zone in the 12.5 kW HERMeS Hall Thruster," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-229, Atlanta, GA, Oct. 8 - 12, 2017, 2017.
  50. Conversano, R. W., Lobbia, R. B., Tilley, K. C., Goebel, D. M., Reilly, S. W., Mikellides, I. G., and Hofer, R. R., "Development and Initial Performance Testing of a Low-Power Magnetically Shielded Hall Thruster with an Internally-Mounted Hollow Cathode," Presented at the 35th International Electric Propulsion Conference, IEPC-2017-064, Atlanta, GA, Oct. 8-12, 2017.
  51. Hall, S. J., Jorns, B., Gallimore, A., and Hofer, R. R., "Expanded Thruster Mass Model Incorporating Nested Hall Thrusters," AIAA Paper 2017-4729, July 2017.
  52. Conversano, R. W., Goebel, D. M., Hofer, R. R., and Arora, N., "Performance Enhancement of a Long-Life, Low-Power Hall Thruster Deep-Space Smallsats," Presented at the IEEE Aerospace Conference, Big Sky, MT, Mar 4-11, 2017.
  53. Kamhawi, H., Huang, W., Haag, T., Yim, J., Herman, D., Peterson, P., Williams, G., Gilland, J., Hofer, R., and Mikellides, I., "Performance, Facility Pressure Effects, and Stability Characterization Tests of Nasa’s Hall Effect Rocket with Magnetic Shielding," Presented at the 63rd JANNAF Propulsion Meeting, Phoenix, AZ, Dec. 5-8, 2016.
  54. Mackey, J., Kamhawi, H., McEnerney, B., and Hofer, R., "Selection of Ceramic Materials for Hall Thrusters: Material Characterization and Properties," Presented at the 63rd JANNAF Propulsion Meeting, Phoenix, AZ, Dec. 5-8, 2016.
  55. Williams, G. J., Gilland, J. H., Peterson, P. Y., Kamhawi, H., Huang, W., Ahern, D. W., Yim, J., Herman, D. A., and Hofer, R. R., "Wear-Testing of the 12.5 kW HERMeS Technology Demonstration Unit One," Presented at the 63rd JANNAF Propulsion Meeting, Dec. 5-8, 2016.
  56. Conversano, R. W., Hofer, R. R., Sekerak, M. J., Kamhawi, H., and Peterson, P. Y., "Performance Comparison of the 12.5 kW HERMeS Hall Thruster Technology Demonstration Units," AIAA-2016-4827, July 2016.
  57. Herman, D., Santiago, W., Kamhawi, H., Polk, J. E., Snyder, J. S., Hofer, R. R., and Sekerak, M. J., "The Ion Propulsion System for the Asteroid Redirect Robotic Mission," AIAA-2016-4824, July 2016.
  58. Hofer, R., Polk, J., Sekerak, M., Mikellides, I., Kamhawi, H., Verhey, T., Herman, D., and Williams, G., "The 12.5 kW Hall Effect Rocket with Magnetic Shielding (HERMeS) for the Asteroid Redirect Robotic Mission," AIAA-2016-4825, July 2016.
  59. Jorns, B. A., Dodson, C., Anderson, J., Goebel, D. M., Hofer, R. R., Sekerak, M., Lopez Ortega, A., and Mikellides, I., "Mechanisms for Pole Piece Erosion in a 6-kW Magnetically-Shielded Hall Thruster," AIAA-2016-4839, July 2016.
  60. Kamhawi, H., Huang, W., Haag, T., Yim, J., Herman, D., Peterson, P. Y., Williams, G., Gilland, J., Hofer, R., and Mikellides, I., "Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster," AIAA-2016-4826, July 2016.
  61. Katz, I., Lopez Ortega, A., Goebel, D. M., Sekerak, M. J., Hofer, R. R., Jorns, B. A., and Brophy, J. R., "Effect of Solar Array Plume Interactions on Hall Thruster Cathode Common Potentials," Presented at the 14th Spacecraft Charging Technology Conference, ESA/ESTEC, Noordwijk, NL, April 4-8, 2016.
  62. Peterson, P. Y., Kamhawi, H., Huang, W., Yim, J., Herman, D., Williams, G., Gilland, J., and Hofer, R., "NASA's HERMeS Hall Thruster Electrical Configuration Characterization " AIAA-2016-5027, July 2016.
  63. Reilly, S., Sekerak, M., and Hofer, R., "Transient Thermal Analysis of the 12.5 kW HERMeS Hall Thruster," AIAA-2016-5024, July 2016.
  64. Williams, G. J., Gilland, J. H., Peterson, P. Y., Kamhawi, H., Huang, W., Ahern, D. W., Yim, J., Herman, D. A., Hofer, R. R., and Sekerak, M., "Wear Testing of the HERMeS Thruster," AIAA-2016-5025, July 2016.
  65. Jorns, B. A., Goebel, D. M., and Hofer, R. R., "Plasma Perturbations in High-Speed Probing of Hall Thruster Discharge Chambers: Quantification and Mitigation," AIAA-2015-4006, July 2015.
  66. Lopez Ortega, A., Jorns, B. A., Mikellides, I. G., and Hofer, R. R., "Numerical Simulations of the XR-5 Hall Thruster for Life Assessment at Different Operating Conditions," AIAA-2015-4008, July 2015.
  67. Garner, C. E., Jorns, B. A., Van Derventer, S., Hofer, R. R., Rickard, R., Liang, R., and Delgado, J., "Low-Power Operation and Plasma Characterization of a Qualification Model SPT-140 Hall Thruster for NASA Science Missions," AIAA-2015-3720, July 2015.
  68. Herman, D. A., Santiago, W., Kamhawi, H., Polk, J. E., Snyder, J. S., Hofer, R. R., and Parker, J. M., "The Ion Propulsion System for the Solar Electric Propulsion Technology Demonstration Mission " Presented at the 34th International Electric Propulsion Conference, IEPC-2015-008, Kobe, Japan, July 4-10, 2015.
  69. Hofer, R., Kamhawi, H., Herman, D., Polk, J., Snyder, J. S., Mikellides, I., Huang, W., Myers, J., Yim, J., Williams, G., Lopez Ortega, A., Jorns, B., Sekerak, M., Griffiths, C. et al., "Development Approach and Status of the 12.5 kW HERMeS Hall Thruster for the Solar Electric Propulsion Technology Demonstration Mission," Presented at the 34th International Electric Propulsion Conference, IEPC-2015-186, Kobe, Japan, July 4-10, 2015.
  70. Kamhawi, H., Huang, W., Haag, T., Shastry, R., Thomas, R., Yim, J., Herman, D., Williams, G., Myers, J., Hofer, R., Mikellides, I., Sekerak, M., and Polk, J., "Performance and Facility Background Pressure Characterization Tests of NASA's 12.5-kW Hall Effect Rocket with Magnetic Shielding Thruster," Presented at the 34th International Electric Propulsion Conference, IEPC-2015-007, Kobe, Japan, July 4-10, 2015.
  71. Mikellides, I. G., Lopez Ortega, A., Hofer, R. R., Polk, J. E., Kamhawi, H., Yim, J. T., and Myers, J., "Hall2De Simulations of a 12.5-kW Magnetically Shielded Hall Thruster for the NASA Solar Electric Propulsion Technology Demonstration Mission," Presented at the 34th International Electric Propulsion Conference, IEPC-2015-254, Kobe, Japan, July 4-10, 2015.
  72. Sekerak, M. J., Hofer, R. R., Polk, J. E., Jorns, B. A., and Mikellides, I. G., "Wear Testing of a Magnetically Shielded Hall Thruster at 2000 S Specific Impulse," Presented at the 34th International Electric Propulsion Conference, IEPC-2015-155, Kobe, Japan, July 4-10, 2015.
  73. Hofer, R. R., Kamhawi, H., Mikellides, I., Herman, D., Polk, J., Huang, W., Yim, J., Myers, J., and Shastry, R., "Design Methodology and Scaling of the 12.5 kW HERMeS Hall Thruster for the Solar Electric Propulsion Technology Demonstration Mission," Presented at the 62nd JANNAF Propulsion Meeting, JANNAF-2015-3946, Nashville, TN, June 1-5, 2015.
  74. Hall, S. J., Florenz, R. E., Gallimore, A. D., Kamhawi, H., Brown, D. L., Peterson, P. Y., Polk, J. E., and Hofer, R. R., "Design Details of a 100-kW Class Nested-Channel Hall Thruster," Presented at the 62nd JANNAF Propulsion Meeting, Nashville, TN, June 1-5, 2015.
  75. Hofer, R. R. and Anderson, J. R., "Finite Pressure Effects in Magnetically Shielded Hall Thrusters," AIAA Paper 2014-3709, July 2014.
  76. Kamhawi, H., Huang, W., Haag, T., Yim, J., Chang, L., Clayman, L., Herman, D. A., Shastry, R., Thomas, R., Griffith, C., Myers, J., Williams, G., Mikellides, I. G., Hofer, R. R. et al., "Overview of the Development of the Solar Electric Propulsion Technology Demonstration Mission 12.5-kW Hall Thruster," AIAA Paper 2014-3898, July 2014.
  77. Conversano, R. W., Goebel, D. M., Mikellides, I. G., Hofer, R. R., Matlock, T. S., Wirz, R. E., and Mikellides, I. G., "Magnetically Shielded Miniature Hall Thruster: Performance Assessment and Status Update," AIAA Paper 2014-3896, July 2014.
  78. Goebel, D. M., Jorns, B., Hofer, R. R., Mikellides, I. G., and Katz, I., "Pole-Piece Interactions with the Plasma in a Magnetically Shielded Hall Thruster," AIAA Paper 2014-3899, July 2014.
  79. Jorns, B., Hofer, R. R., and Mikellides, I. G., "Power Dependence of the Electron Mobility Profile in a Hall Thruster," AIAA Paper 2014-3620, July 2014.
  80. Hall, S. J., Florenz, R. E., Gallimore, A., Kamhawi, H., Brown, D. L., Polk, J. E., Goebel, D. M., and Hofer, R. R., "Implementation and Initial Validation of a 100-kW Class Nested-Channel Hall Thruster," AIAA Paper 2014-3815, July 2014.
  81. Sekerak, M. J., Longmier, B., Gallimore, A., Huang, W., Kamhawi, H., Hofer, R. R., Jorns, B., and Polk, J. E., "Mode Transitions in Magnetically Shielded Hall Effect Thrusters," AIAA Paper 2014-3511, July 2014.
  82. Snyder, J. S. and Hofer, R. R., "Throttled Performance of the SPT-140 Hall Thruster," AIAA Paper 2014-3816, July 2014.
  83. Hofer, R. R., Jorns, B. A., Polk, J. E., Mikellides, I. G., and Snyder, J. S., "Wear Test of a Magnetically Shielded Hall Thruster at 3000 Seconds Specific Impulse," Presented at the 33rd International Electric Propulsion Conference, IEPC-2013-033, Washington, DC, Oct 6-10, 2013.
  84. Conversano, R. W., Goebel, D. M., Hofer, R. R., Matlock, T. S., and Wirz, R. E., "Magnetically Shielded Miniature Hall Thruster: Development and Initial Testing," Presented at the 33rd International Electric Propulsion Conference, IEPC-2013-201, Washington, DC, Oct 6-10, 2013.
  85. Goebel, D. M., Hofer, R. R., Mikellides, I. G., Katz, I., Polk, J. E., and Dotson, B., "Conducting Wall Hall Thrusters," Presented at the 33rd International Electric Propulsion Conference, IEPC-2013-276, Washington, DC, Oct 6-10, 2013.
  86. Oh, D. Y., Snyder, J. S., Goebel, D. M., Hofer, R. R., Landau, D. F., and Randolph, T. M., "Solar Electric Propulsion for Discovery Class Missions," Presented at the 33rd International Electric Propulsion Conference, IEPC-2013-124, Washington, DC, Oct. 6-10, 2013.
  87. Sekerak, M. J., Longmier, B. W., Gallimore, A. D., Brown, D. L., Hofer, R. R., and Polk, J. E., "Azimuthal Spoke Propagation in Hall Effect Thrusters," Presented at the 33rd International Electric Propulsion Conference, IEPC Paper 2013-143, Washington, DC, Oct. 6-10, 2013.
  88. Jorns, B. A. and Hofer, R. R., “Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster,” AIAA-2013-4119, July 2013.
  89. Goebel, D. M., Hofer, R. R., Mikellides, I. G., Katz, I., Polk, J. E., Dotson, B., “Conducting Wall Hall Thrusters,” AIAA-2013-4117, July 2013.
  90. Mikellides, I. M., Hofer, R. R., Katz, I., Goebel, D. M., “The Effectiveness of Magnetic Shielding in High-Isp Hall Thrusters,” AIAA-2013-3885, July 2013.
  91. Sekerak, M. J., Longmier, B. W., Gallimore, A. D., Brown, D. L., Hofer, R. R., Polk, J. E., “Mode Transitions in Hall Effect Thrusters,” AIAA-2013-4116, July 2013.
  92. Sekerak, M., McDonald, M., Hofer, R., and Gallimore, A., "Hall Thruster Plume Measurements from High-Speed Dual Langmuir Probes with Ion Saturation Reference," Proceedings of the IEEE Aerospace Conference, Big Sky, MT, March 2-9, 2013, pp. 1-16, (Institute of Electrical and Electronics Engineers, Washington, DC).
  93. McDonald, M. S., Sekerak, M. J., Gallimore, A. D., and Hofer, R. R., "Plasma Oscillation Effects on Nested Hall Thruster Operation and Stability," Proceedings of the IEEE Aerospace Conference, Big Sky, MT, March 2-9, 2013, pp. 1-17, (Institute of Electrical and Electronics Engineers, Washington, DC).
  94. Strange, N., Landau, D., Hofer, R., Snyder, J. S., Randolph, T., Campagnola, S. et al., "Solar Electric Propulsion Gravity-Assist Tours for Jupiter Missions," AIAA Paper 2012-4518, August 2012.
  95. Florenz, R., Liu, T. M., Gallimore, A. D., Kamhawi, H., Brown, D. L., Hofer, R. R. et al., "Electric Propulsion of a Different Class: The Challenges of Testing for Megawatt Missions," AIAA-2012-3942, July 2012.
  96. Hofer, R. R., Goebel, D. M., Mikellides, I. G., and Katz, I., "Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase II: Experiments," AIAA-2012-3788, July 2012.
  97. Mikellides, I. G., Katz, I., Hofer, R. R., and Goebel, D. M., "Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase III: Comparison of Theory with Experiment," AIAA-2012-3789, July 2012.
  98. Snyder, J. S., Brophy, J., Hofer, R. R., Goebel, D. M., and Katz, I., "Experimental Investigation of a Direct-Drive Hall Thruster and Solar Array System at Power Levels up to 10 kW," AIAA-2012-4068, July 2012.
  99. Hofer, R. R. and Randolph, T. M., "Mass and Cost Model for Selecting Thruster Size in Electric Propulsion Systems," AIAA Paper 2011-5518, July 2011.
  100. Mikellides, I. G., Katz, I., and Hofer, R. R., "Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase One: Numerical Simulations," AIAA Paper 2011-5809, July 2011.
  101. Shastry, R., Gallimore, A. D., and Hofer, R. R., "Experimental Characterization of the Near-Wall Plasma in a 6-kW Hall Thruster and Comparison to Simulation," AIAA Paper 2011-5589, July 2011.
  102. Sultan, A., Koch, B., Mathers, A., and Hofer, R. R., "Development of a Modular Hall Thruster Power Converter," AIAA Paper 2011-5997, July 2011.
  103. Strange, N., Merrill, R., Landau, D., Drake, B., Brophy, J., and Hofer, R., "Human Missions to Phobos and Deimos Using Combined Chemical and Solar Electric Propulsion," AIAA Paper 2011-5663, July 2011.
  104. Katz, I., Mikellides, I. G., and Hofer, R. R., "Channel Wall Plasma Thermal Loads in Hall Thrusters with Magnetic Shielding," AIAA Paper 2011-6082, July 2011.
  105. Hofer, R. R., "High-Specific Impulse Operation of the BPT-4000 Hall Thruster for NASA Science Missions," AIAA Paper 2010-6623, July 2010.
  106. Mikellides, I. G., Katz, I., Hofer, R. R., Goebel, D. M., De Grys, K. H. et al., "Magnetic Shielding of the Acceleration Channel in a Long-Life Hall Thruster," AIAA Paper 2010-6942, July 2010.
  107. Snyder, J. S., Goebel, D. M., Hofer, R. R., Polk, J. E., Wallace, N. C. et al., "Performance Evaluation of the T6 Ion Engine," AIAA Paper 2010-7114, July 2010.
  108. Mueller, J., Hofer, R. R., Parker, M., and Ziemer, J. K., "Survey of Propulsion Options for Cubesats," Presented at the 57th JANNAF Propulsion Meeting, Colorado Springs, CO, May 3-7, 2010.
  109. Shastry, R., Gallimore, A. D., and Hofer, R. R., "Erosion Characterization Via Ion Power Deposition Measurements in a 6-kW Hall Thruster," Presented at the 57th JANNAF Propulsion Meeting, Colorado Springs, CO, May 3-7, 2010.
  110. McDonald, M. S., Gallimore, A. D., Hofer, R. R., and Goebel, D. M., "Development of a 3D Electron Trajectory Model with Monte Carlo Collisions for the Hall Thruster Near-Field Plume," Presented at the 57th JANNAF Propulsion Meeting, Colorado Springs, CO, May 3-7, 2010.
  111. Hofer, R. R., Goebel, D. M., Snyder, J. S., and Sandler, I., "BPT-4000 Hall Thruster Extended Power Throttling Range Characterization for NASA Science Missions," Presented at the 31st International Electric Propulsion Conference, IEPC-2009-085, Ann Arbor, MI, Sept. 20-24, 2009.
  112. Mikellides, I. G., Katz, I., Hofer, R. R., and Goebel, D. M., "Hall-Effect Thruster Simulations with 2-D Electron Transport and Hydrodynamic Ions," Presented at the 31st International Electric Propulsion Conference, IEPC-2009-114, Ann Arbor, MI, Sept. 20-24, 2009.
  113. Oh, D. Y., Hofer, R. R., Katz, I., Sims, J. A., Warner, N. Z. et al., "Benefits of Using Hall Thrusters for a Mars Sample Return Mission," Presented at the 31st International Electric Propulsion Conference, IEPC-2009-217, Ann Arbor, MI, Sept. 20-24, 2009.
  114. Shastry, R., Gallimore, A. D., and Hofer, R. R., "Near-Wall Plasma Characterization of a 6-kW Hall Thruster," Presented at the 31st International Electric Propulsion Conference, IEPC-2009-133, Ann Arbor, MI, Sept. 20-24, 2009.
  115. Snyder, J. S., Randolph, T. M., Hofer, R. R., and Goebel, D. M., "Simplified Ion Thruster Xenon Feed System for NASA Science Missions," Presented at the 31st International Electric Propulsion Conference, IEPC-2009-064, Ann Arbor, MI, Sept. 20-24, 2009.
  116. Szabo, J., Robin, M., Duggan, J., and Hofer, R. R., "Light Metal Propellant Hall Thrusters," Presented at the 31st International Electric Propulsion Conference, IEPC-2009-138, Ann Arbor, MI, Sept. 20-24, 2009.
  117. Shastry, R., Gallimore, A. D., and Hofer, R. R., "Near-Wall Plasma Properties and EEDF Measurements of a 6-kW Hall Thruster," AIAA-2009-5356, Aug. 2009.
  118. De Grys, K. H., Carpenter, C., Welander, B., Mathers, A., Hofer, R. R. et al., "Extended Duration Operation of BPT-4000 Qualification Unit at Low Power," Presented at the 3rd JANNAF Spacecraft Propulsion Joint Subcommittee Meeting, Orlando, FL, Dec. 8-12, 2008.
  119. Hofer, R. R., Katz, I., Mikellides, I. G., Goebel, D. M., Jameson, K. K. et al., "Efficacy of Electron Mobility Models in Hybrid-PIC Hall Thruster Simulations," AIAA Paper 2008-4924, July 2008.
  120. Shastry, R., Gallimore, A. D., and Hofer, R. R., "Interpretation of Wall-Mounted Probe Characteristics in Hall Thrusters," AIAA Paper 2008-4723, July 2008.
  121. Shastry, R., Hofer, R. R., Reid, B. M., and Gallimore, A. D., "Method for Analyzing ExB Probe Spectra from Hall Thruster Plumes," AIAA Paper 2008-4647, July 2008.
  122. Reid, B. M., Shastry, R., Gallimore, A. D., and Hofer, R. R., "Angularly-Resolved ExB Probe Spectra in the Plume of a 6-kW Hall Thruster," AIAA Paper 2008-5287, July 2008.
  123. Hofer, R. R., Mikellides, I. G., Katz, I., and Goebel, D. M., "BPT-4000 Hall Thruster Discharge Chamber Erosion Model Comparison with Qualification Life Test Data," Presented at the 30th International Electric Propulsion Conference, IEPC Paper 2007-267, Florence, Italy, Sept. 17-20, 2007.
  124. Katz, I., Hofer, R. R., and Goebel, D. M., "Ion Current in Hall Thrusters," Presented at the 30th International Electric Propulsion Conference, IEPC Paper 2007-365, Florence, Italy, 2007.
  125. Jameson, K. K., Goebel, D. M., Hofer, R. R., and Watkins, R. M., "Cathode Coupling in Hall Thrusters," Presented at the 30th International Electric Propulsion Conference, IEPC Paper 2007-278, Florence, Italy, Sept. 17-20, 2007.
  126. Hofer, R. R., Mikellides, I. G., Katz, I., and Goebel, D. M., "Wall Sheath and Electron Mobility Modeling in Hybrid-PIC Hall Thruster Simulations," AIAA Paper 2007-5267, July 2007.
  127. Hofer, R. R., Goebel, D. M., and Watkins, R. M., "Compact LaB6 Hollow Cathode for a 6 kW Hall Thruster," Presented at the 54th JANNAF Propulsion Meeting, Denver, CO, May 14-17, 2007.
  128. Brown, D. L., Reid, B. M., Gallimore, A. D., Hofer, R. R., Haas, J. M. et al., "Performance Characterization and Design Verification of a 6 kW Laboratory Model Hall Thruster," Presented at the 54th JANNAF Propulsion Meeting, Denver, CO, May 14-17, 2007.
  129. Haas, J. M., Hofer, R. R., Brown, D. L., Reid, B. M., and Gallimore, A. D., "Design of a 6 kW Hall Thruster for High Thrust/Power Investigation," Presented at the 54th JANNAF Propulsion Meeting, Denver, CO, May 14-17, 2007.
  130. Reid, B. M., Gallimore, A. D., Hofer, R. R., Li, Y., and Haas, J. M., "Anode Design and Verification for a 6 kW Hall Thruster," Presented at the 54th JANNAF Propulsion Meeting, Denver, CO, May 14-17, 2007.
  131. Hofer, R. R., Randolph, T. M., Oh, D. Y., Snyder, J. S., and de Grys, K. H., "Evaluation of a 4.5 kW Commercial Hall Thruster System for NASA Science Missions," AIAA Paper 2006-4469, 42nd Joint Propulsion Conference, Sacramento, CA, July 9-12, 2006.
  132. Hofer, R. R., Johnson, L. K., Goebel, D. M., and Fitzgerald, D. J., "Effects of an Internally-Mounted Cathode on Hall Thruster Plume Properties," AIAA Paper 2006-4482, 42nd Joint Propulsion Conference, Sacramento, CA, July 9-12, 2006.
  133. Hofer, R. R., Katz, I., Mikellides, I. G., and Gamero-Castano, M., "Heavy Particle Velocity and Electron Mobility Modeling in Hybrid-PIC Hall Thruster Simulations," AIAA Paper 2006-4658, 42nd Joint Propulsion Conference, Sacramento, CA, July 9-12, 2006.
  134. Welander, B., Carpenter, C., de Grys, K. H., Hofer, R. R., Randolph, T. M. et al., "Life and Operating Range Extension of the BPT-4000 Qualification Model Hall Thruster," AIAA Paper 2006-5263, 42nd Joint Propulsion Conference, Sacramento, CA, July 9-12, 2006.
  135. Hofer, R. R., Gallimore, A. D., "Efficiency Analysis of a High-Specific Impulse Hall Thruster," AIAA-2004-3602, 40th Joint Propulsion Conference, Ft. Lauderdale, FL, July 11-14, 2004.
  136. Jacobson, D. T., Manzella, D. H., Hofer, R. R., Peterson, P. Y., “NASA’s 2004 Hall Thruster Program,” AIAA-2004-3600, 40th Joint Propulsion Conference, Ft. Lauderdale, FL, July 11-14, 2004.
  137. Manzella, D. H., Jacobson, D. T., Peterson, P. Y., Hofer, R. R., “Scaling Hall Thrusters to High Power,” 52nd JANNAF Propulsion Meeting, Las Vegas, NV, May 10-13, 2004. (Also NASA TM-2004-213087)
  138. Hofer, R. R., Haas, J. M., Gallimore, A. D., "Ion Voltage Diagnostics in the Far-Field Plume of a High-Specific Impulse Hall Thruster," AIAA-2003-4556, 39th Joint Propulsion Conference, Huntsville, AL, July 20-23, 2003.
  139. Hofer, R. R., Gallimore, A. D., "Ion Species Fractions in the Far-Field Plume of a High-Specific Impulse Hall Thruster," AIAA-2003-5001, 39th Joint Propulsion Conference, Huntsville, AL, July 20-23, 2003.
  140. Hofer, R. R., Gallimore, A. D., “Recent Results from Internal and Very-Near-Field Plasma Diagnostics of a High Specific Impulse Hall Thruster,” IEPC-03-037, 28th International Electric Propulsion Conference, Toulouse, France, March 17-21, 2003.
  141. Hofer, R. R., Jankovsky, R. S., “The Influence of Current Density and Magnetic Field Topography in Optimizing the Performance, Divergence, and Plasma Oscillations of High Specific Impulse Hall Thrusters,” IEPC-03-142, 28th International Electric Propulsion Conference, Toulouse, France, March 17-21, 2003.
  142. Hofer, R. R., Gallimore, A. D., "The Role of Magnetic Field Topography in Improving the Performance of High-Voltage Hall Thrusters," AIAA-2002-4111, 38th Joint Propulsion Conference, Indianapolis, IN, July 7-10, 2002.
  143. Walker, M. L. R., Hofer, R. R., Gallimore, A. D., "The Effects of Nude Faraday Probe Design and Vacuum Facility Backpressure on the Measured Ion Current Density Profile of Hall Thruster Plumes," AIAA-2002-4253, 38th Joint Propulsion Conference, Indianapolis, IN, July 7-10, 2002.
  144. Jankovsky, R. S., Jacobson, D. T., Pinero, L. R., Sarmiento, C. J., Manzella, D. H., Hofer, R. R., Peterson, P. Y., "NASA's Hall Thruster Program 2002," AIAA-2002-3675, 38th Joint Propulsion Conference, Indianapolis, IN, July 7-10, 2002.
  145. Manzella, D. H., Jankovsky, R. S., Hofer, R. R., "Laboratory Model 50 kW Hall Thruster," AIAA-2002-3676, 38th Joint Propulsion Conference, Indianapolis, IN, July 7-10, 2002.
  146. Hofer, R. R., Walker, M. L. R., Gallimore, A. D., "A Comparison of Nude and Collimated Faraday Probes for Use with Hall Thrusters," IEPC-01-020, 27th International Electric Propulsion Conference, Pasadena, CA, October 15-19, 2001.
  147. Hofer, R. R., Peterson, P. Y., Gallimore, A. D., "A High Specific Impulse Two-Stage Hall Thruster with Plasma Lens Focusing," IEPC-01-036, 27th International Electric Propulsion Conference, Pasadena, CA, October 15-19, 2001.
  148. Hofer, R. R., Peterson, P. Y., Gallimore, A. D., "Characterizing Vacuum Facility Backpressure Effects on the Performance of a Hall Thruster," IEPC-01-045, 27th International Electric Propulsion Conference, Pasadena, CA, October 15-19, 2001.
  149. Hofer, R.R., and Jankovsky, R. S., "A Hall Thruster Performance Model Incorporating the Effects of a Multiply-Charged Plasma," AIAA-2001-3322, 37th Joint Propulsion Conference, Salt Lake City, UT, July 9-11, 2001.
  150. Jankovsky, R. S., Jacobson, D. T., Rawlin, V. K., Mason, L. S., Mantenieks, M. A., Manzella, D. H., Hofer, R. R., Peterson, P. Y., "NASA's Hall Thruster Program," AIAA-2001-3888, 37th Joint Propulsion Conference, Salt Lake City, UT, July 9-11, 2001.
  151. Hofer, R.R., Haas, J. M., and Gallimore, A.D., "Development of a 45-Degree Parallel-Plate Electrostatic Energy Analyzer for Hall Thruster Plume Studies: Preliminary Data," IEPC-99-113, 26th International Electric Propulsion Conference, Kitakyushu, Japan, October 1999.