XV
List of Figures
Chapter 1: Hall Effect Thruster
Figure 1.1: Hall thruster cross-section schematic showing the crossed electric and magnetic fields, and the ion and electron paths.
Figure 1.2: Magnetic field lines in the channel region of the NASA-173Mv Hall thruster Figure 1.3: Typical Hall thruster radial magnetic field and axial electric field along the channel length
Figure 1.4: Schematic cross section of the plasma in the Hall thruster channel. Figure 1.5: Hall thruster electrical schematic and potential distribution
Figure 1.6: Electrical schematic for the currents flowing through the discharge plasma and power supply.
Figure 1.7: Measured evolution of the discharge current of the SPT-100.
Chapter 2: Power Processing Unit (PPU) Description
Figure 2.1: Anode supply I-V characteristic
Figure 2.2: 200 W Hall thruster discharge supply (buck derived PWM full-bridge) Figure 2.3: Ignitor pulse form
Figure 2.4: SPT cross section and PPU power supplies scheme Figure 2.5: SPT-100 PPU block diagram (SS/L and Fakel) Figure 2.6: Alcatel ETCA PPU for 1.6 kW SPT-100
Figure 2.7: PPU supplies sequence of operation (1.5 kW SPT-100)
Chapter 3: Direct-Drive Implementation
Figure 3.1: PPU and solar array output I-V characteristic
Figure 3.2: Standard and Direct Drive configuration for electric propulsion system Figure 3.3: Direct drive SPT system
Figure 3.4: Tapped solar array system
Figure 3.5: Current, voltage and power threshold for ISS array
Figure 3.6: High voltage solar array in direct drive configuration vs standard PPU system
List of Figures
XVI driven HET
Figure 3.8: V-I characteristic of Express BPT-4000 and its solar arrays Figure 3.9: Trajectory analysis approaches for 10 direct drive 30 kW HETs
Chapter 4: Direct-Drive Implementation in Low-Power Thrusters
Figure 4.1: Artistic representation of the TacSat-2 spacecraft Figure 4.2: Busek BHT-200
Figure 4.3: Artistic representation of the Meteosat 8 spacecraft
Chapter 5: Direct-Drive Implementation in Medium-Power Thrusters
Figure 5.1: Artistic impression of STENTOR spacecraft Figure 5.2: STENTOR TCS fluid loop assembly
Figure 5.3: STENTOR Thruster Module: SPT-100 and PPS-1350 Figure 5.4: Plasma propulsion system architecture
Figure 5.5: Artistic representation of the SMART-1 Figure 5.6: EPS functional diagram
Chapter 6: Direct-Drive Implementation in High-Power Thrusters
Figure 6.1: Artistic picture of AEHF spacecraft Figure 6.2: Electric propulsion system schematic Figure 6.3: BPT-4000 Hall thruster
Figure 6.4: PPU block diagram
Figure 6.5: Comparison between HET system (with direct drive and conventional PPU) and available baseline Dawn payload mass
Chapter 8: Direct-Drive Assessment Conclusions
Figure 8.1: Direct Drive mass benefits
Figure 8.2: Mass saving in one PPU due to the implementation of a Direct Drive configuration
Figure 8.3: Percentage of indirect advantages over the total mass saving Figure 8.4: S/C percentage dry mass saving due to direct drive implementation
Chapter 9: Test Setup
Figure 9.1: HT-100 firing at Alta IV-4 test facility (left) and HT-100 mounted on ALTA thrust balance (right)
List of Figures
XVII Figure 9.2: ALTA’s IV-4 vacuum facility Figure 9.3: The pyranometer (LP PYRA 02)
Chapter 10: Filter Design
Figure 10.1: Hall thruster schematization with Pspice
Figure 10.2: HT-100 current oscillation at anode voltage of 300 V and anode flow rate of 1 mg/s (scale 100mv/A)
Figure 10.3: HT-100 simulated current oscillation
Figure 10.4: Solar array circuit schematization with Pspice Figure 10.5: Nominal solar panel I-V curve simulated with Pspice
Figure 10.6: Filter architecture. Yellow circles represent the location where measurements were taken.
Figure 10.7: Direct-Drive electrical circuit (Pspice) Figure 10.8: Double-log plot of the simulation results Figure 10.9: Filter unit
Figure 10.10: Bode plot of the filter transfer function (neglecting parasitic characteristics of the circuit)
Figure 10.11: Bode plot of the filter transfer function (including parasitic characteristics of the circuit)
Figure 10.12: Filter test with laboratory power supply - electrical circuit Figure 10.13: Thruster current oscillations (scale 100 mV/A)
Figure 10.14: Power supply current oscillations (scale 100 mV/A)
Figure 10.15: Current oscillations (yellow) and its FFT (red) on the thruster side Figure 10.16: Current oscillations (yellow) and its FFT (red) and at the power supply Figure 10.17: Ignition transient. Thruster current peak (scale: 10 mV/A)
Figure 10.18: Ignition transient. Current peak on power supply side (scale: 100 mV/A) Figure 10.19: Ignition transient. Thruster current peak (scale: 10 mV/A)
Figure 10.20: Ignition transient. Thruster current peak (scale: 10 mV/A). Filter removed
Chapter 11: Solar array system
Figure 11.1: Solar array orientation angles
Figure 11.2: Real solar panel I-V curve in standard condition (1000 W/m2, 25°C)
Figure 11.3: Real solar panel power-voltage curve in standard condition (1000 W/m2,
25°C)
List of Figures
XVIII Figure 12.1: Alta’s Direct-Drive solar array test-bed
Figure 12.2: Direct-Drive system electrical scheme. Green circles represent locations of current measurements
Figure 12.3: Test sequence of the HT-100 Direct-Drive operation
Figure 12.4.: Current-Voltage curve during test runtime and thruster operative conditions
Figure 12.5: Power-Voltage curve during test runtime and thruster operative conditions Figure 12.6: Ignition transient during Soft Start on thruster side
Figure 12.7: Ignition transient during Soft Start on panel side Figure 12.8: Ignition transient during Hard Start on thruster side Figure 12.9: Ignition transient during Hard Start on panel side
Figure 12.10: RMS value of current oscillations on thruster side and panel side Figure 12.11: FFT of current signal on thruster side
Figure 12.12: FFT of current signal on panel side
Appendix C: Indirect Mass Saving Esteem Procedure
Figure C.1: Curve fitting obtained from data in [53]
