Since 2005, I have worked at the Jet Propulsion Laboratory in Pasadena, CA in the Electric Propulsion Group. JPL is a NASA federally funded research and development center (FFRDC). The lab is managed by the California Institute of Technology.

Between 2000-2005, I worked first as an intern, then part-time, and eventually full-time, in the Electric Propulsion Group at NASA Glenn Research Center.

From 1998 to 2004, I was Ph.D. student in Aerospace Engineering at the University of Michigan, where I worked in the Plasmadynamics and Electric Propulsion Laboratory. My thesis advisor was Prof. Alec Gallimore.  

Questions or comments are welcome. Feel free to contact me at the e-mail address listed at the bottom of this page.

Ph.D. Dissertation

Hofer, R. R., "Development and characterization of high-efficiency, high-specific impulse xenon Hall thrusters," Ph.D. dissertation, Dept. of Aerospace Engineering, University of Michigan, 2004.

Journal Articles

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).

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).

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).

Katz, I., Hofer, R. R., and Goebel, D. M., "Ion Current in Hall Thrusters," IEEE Transactions on Plasma Science 36, 5, 2015-2024 (2008).

Hofer, R. R. 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).

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).

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).

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 and Other Publications

Hofer, R. R., "High-Specific Impulse Operation of the BPT-4000 Hall Thruster for NASA Science Missions," AIAA Paper 2010-6623, July 2010.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Shastry, R., Gallimore, A. D., and Hofer, R. R., "Interpretation of Wall-Mounted Probe Characteristics in Hall Thrusters," AIAA Paper 2008-4723, July 2008.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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," Presented at the 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference, AIAA Paper 2006-4469, Sacramento, CA, July 9-12, 2006.

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," Presented at the 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference, AIAA Paper 2006-5263, Sacramento, CA, July 9-12, 2006.

Hofer, R. R., Johnson, L. K., Goebel, D. M., and Fitzgerald, D. J., "Effects of an Internally-Mounted Cathode on Hall Thruster Plume Properties," Presented at the 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference, AIAA Paper 2006-4482, Sacramento, CA, July 9-12, 2006.

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," Presented at the 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference, AIAA Paper 2006-4658, Sacramento, CA, July 9-12, 2006.

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.

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.

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)

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Gulczinski, F. S., Hofer, R.R., and Gallimore A.D., "Near-field Ion Energy and Species Measurements of a 5 kW Laboratory Hall Thruster, " AIAA-99-2430, 35th Joint Propulsion Conference, Los Angeles, CA, June 1999.