Person:
Walker, Mitchell L. R.

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    Design and construction of an annular helicon closed drift thruster
    (Georgia Institute of Technology, 2009-01) Walker, Mitchell L. R. ; Kieckhafer, Alexander W. ; Daniel Guggenheim School of Aerospace Engineering ; Office of Sponsored Programs ; College of Engineering
    The Georgia Institute of Technology (GA Tech) has completed a three-phase process which developed an annular helicon plasma source and integrated it into a Hall Effect Thruster (HET). Phase 1 designed the annular helicon source and began plasma measurements using an RF-compensated Langmuir probe. Phase 2 extended the operating conditions of the annular helicon and used a highly-efficient commercial Langmuir probe unit for rapid data acquisition and development of design criteria for the Annular Helicon Closed Drift Thruster (AHCDT) device. Phase 3 took the results of Phase 2, developed the design for the AHCDT, and began performance testing. Initial tests of the AHCDT show that when operated at conditions similar to a HET, the thrust output of the AHCDT is within 10% of the original HET. Additionally, the AHCDT has shown the capability to operate at discharge voltages much lower than a HET, thus enabling future performance characterization and optimization at high thrust-to-power ratios.
  • Item
    Facility Effects on Ion Flux Measurements of the Radiofrequency Ion Thruster 10 cm (RIT-10)
    (Georgia Institute of Technology, 2020-01) Jovel, David R. ; Nauschütt, Benny ; Walker, Mitchell L. R. ; Klar, Peter J. ; Office of Graduate Education ; Georgia Institute of Technology. Office of Graduate Studies ; Georgia Institute of Technology. Office of the Vice Provost for Graduate Education and Faculty Development ; Georgia Institute of Technology. Student Government Association ; Georgia Institute of Technology. School of Aerospace Engineering
    Electric propulsion is an alternative means for spacecraft to execute orbital maneuvers and provide attitude control in space. Electric propulsion devices generate thrust by electrically converting a neutral gas into a plasma and accelerating the heavy ions through an electric field. The performance of these devices is characterized in vacuum test facilities that can appropriately simulate the space environment and accommodate the plasma plume generated by the thruster. Understanding the facility effects on ion flux pathways from the plasma to its surroundings is critical in characterizing potential thruster-spacecraft interactions. The ion charge density profile of the 1.35 kW radiofrequency ion thruster 10 cm, RIT-10, was captured at the Justus-Liebig University JUMBO test facility. The vacuum chamber maintained high-vacuum levels in the 1x10E-6 Torr range using three turbomolecular pumps and an array of 8 cryopumps. The RIT-10 operating condition was held constant at 2 sccm Xe, 80 mA beam current, 1000 V screen grid bias, and -150 V acceleration grid bias with respect to chamber ground. The vacuum pumping configuration was changed by maintaining all three turbomolecular pumps operational while toggling on different sets of cryopumps. At each pumping configuration, Faraday probe scans across the RIT-10 exhaust plume collected ion flux measurements at 74 cm downstream from the thruster exit plane. The ion charge density profiles captured during the various pumping configurations are compared with the baseline scan. The results and their implications in characterizing facility effects on ion charge density and beam divergence angle of the RIT-10 are discussed on this poster.
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    A full scale atmospheric flight experimental research environment for the Mars helicopter
    (Georgia Institute of Technology, 2019-09-09) Afman, J. Pablo ; Feron, Eric ; Walker, Mitchell L. R. ; Daniel Guggenheim School of Aerospace Engineering ; Georgia Institute of Technology. School of Aerospace Engineering
    This paper proposes to test a full-accuracy ight test experiment for the Mars helicopter through an atmospheric reduced-g flight housing a vacuum chamber.