The technological and commercial expansion of electric propulsion

Lev, Dan; Myers, Roger; Lemmer, Kristina; Kolbeck, Jonathan; Koizumi, Hiroyuki; Polzin, Kurt A.

doi:10.1016/j.actaastro.2019.03.058

Cited by 243 publications

(112 citation statements)

References 28 publications

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“…The third row contains the Fast Fourier Transforms (FFT) of the temporal modes w i to give more information on the spectral content of the temporal POD modes. Finally, the singular values λ i of each POD modes are shown in the title of the second row of subplots as σ i equal to λ 2 i over the sum of all the squared singular values and expressed as a percentage. Of the over one hundred POD modes computed, only the ones with the higher σ are displayed, as they represent most of the energy stored in the measured fluctuations.…”

Section: Analysis Of the Oscillatory Phenomenon Through The Regime Trmentioning

confidence: 99%

“…), a propulsion system is needed aboard these satellites. Electric propulsion appears to be the best option and ion-gridded thrusters along with Hall-Effect Thrusters (HET) are now routinely used [1,2]. The latter are known from the 1960s and have been successfully used in space (for example, the Safran PPS-1350 on the ESA SMART-1 mission to the moon, in 2003), but, despite extensive studies [3][4][5], the physics of these thrusters is still not well-understood.…”

Section: Introductionmentioning

confidence: 99%

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Fast Camera Analysis of Plasma Instabilities in Hall Effect Thrusters Using a POD Method under Different Operating Regimes

et al. 2020

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Even after half a century of development, many phenomena in Hall Effect Thrusters are still not well-understood. While numerical studies are now widely used to study this highly non-linear system, experimental diagnostics are needed to validate their results and identify specific oscillations. By varying the cathode heating current, its emissivity is efficiently controlled and a transition between two functioning regimes of a low power thruster is observed. This transition implies a modification of the axial electric field and of the plasma plume shape. High-speed camera imaging is performed and the data are analysed using a Proper Orthogonal Decomposition method to isolate the different types of plasma fluctuations occurring simultaneously. The low-frequency breathing mode is observed, along with higher frequency rotating modes that can be associated to rotating spokes or gradient-induced instabilities. These rotating modes are observed while propagating outside the thruster channel. The reduction of the cathode emissivity beyond the transition comes along with a disappearance of the breathing mode, which could improve the thruster performance and stability.

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Section: Analysis Of the Oscillatory Phenomenon Through The Regime Trmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fast Camera Analysis of Plasma Instabilities in Hall Effect Thrusters Using a POD Method under Different Operating Regimes

et al. 2020

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“…The MEE set has five slow variables and one (very regular) fast variable, l. The acceleration vector, a, in Eq. (7) can be written as…”

Section: Equations Of Motionmentioning

confidence: 99%

A novel approach for optimal trajectory design with multiple operation modes of propulsion system, part 2

et al. 2020

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Equipping a spacecraft with multiple solar-powered electric engines (of the same or different types) compounds the task of optimal trajectory design due to presence of both real-valued inputs (power input to each engine in addition to the direction of thrust vector) and discrete variables (number of active engines).Each engine can be switched on/off independently and "optimal" operating power of each engine depends on the available solar power, which depends on the distance from the Sun. Application of the Composite Smooth Control (CSC) framework to a heliocentric fuel-optimal trajectory optimization from the Earth to the comet 67P/Churyumov-Gerasimenko is demonstrated, which presents a new approach to deal with multiple-engine problems. Operation of engine clusters with 4, 6, 10 and even 20 engines of the same type can be optimized.Moreover, engine clusters with different/mixed electric engines are considered with either 2, 3 or 4 different types of engines. Remarkably, the CSC framework allows us 1) to reduce the original multi-point boundary-value problem to a two-point boundary-value problem (TPBVP), and 2) to solve the resulting TP-BVPs using a single-shooting solution scheme and with a random initialization of the missing costates. While the approach we present is a continuous neighbor of the discontinuous extremals, we show that the discontinuous necessary conditions are satisfied in the asymptotic limit. We believe this is the first indirect method to accommodate a multi-mode control of this level of complexity with realistic engine performance curves. The results are interesting and promising for dealing with a large family of such challenging multi-mode optimal control problems.

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“…Additionally, these micro-Hall thrusters generally require a higher propellant mass flow rate per channel volume (̇/ ) where ̇ and are the mass flow rate for nominal operation and the total volume of the discharge channel, respectively. Hall thrusters operating at 300 W or less require 0.20-0.62 mg/cm 3 •s [15,16], which is much larger than in kW-class Hall thrusters (0.07-0.19 mg/cm 3 •s) [17,18]. Thus, it is expected that the strong magnetic field and large neutral particle supply per unit volume in lowpower Hall thrusters affect the electron mobility as well as the ionization in the near-plume region, which can exhibit a different ionization rate profile compared to that of kW-class Hall thrusters.…”

Section: Introductionmentioning

confidence: 99%

Distinct discharge modes in micro Hall thruster plasmas

Lee

Doh

Kim

et al. 2021

Plasma Sources Sci. Technol.

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Two distinct discharge modes were observed in a 50-W-class micro-Hall thruster plasma under different operating conditions. A ball-shaped plasma with a broad plume (Mode A) was observed at low mass flow rates (less than 0.37 mg/s) over the entire operational anode voltage range (160-280 V). Raising the anode voltage beyond 200 V with the mass flow rate fixed (larger than 0.37 mg/s) produced a narrow plume and stretched core structure (Mode B). In Mode B, the thruster showed performance improvements in terms of thrust (3.8 mN vs. 3.3 mN), specific impulse (913 s vs. 800 s), and anode efficiency (28% vs. 22%), with only a 2 W difference in the anode power (61 W in Mode B and 59 W in Mode A). This suggests that operation is more advantageous in Mode B than in Mode A for the utilization of such low-power Hall thrusters. A considerable difference was observed in the axial profile of Xe II ion velocity between the two modes. Mode A exhibits an axially extended ion acceleration region outside the discharge channel, where 75% of the final ion velocity is achieved at approximately 40 mm from the thruster exit, while most of the ion acceleration occurs within 10 mm from the thruster exit in Mode B. Measurements show that the full width at half maximum of the Xe II ion energy distribution function, electron temperature, and Xe II emission intensity decreased after the plasma transitioned from Mode A to Mode B. Based on the optical emission spectroscopy, the ionization rate in the plasma plume decreased by 30-41% after the mode change, which is likely related to the reduction of the beam angle and electron current by 24% and 30%, respectively.

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The technological and commercial expansion of electric propulsion

Cited by 243 publications

References 28 publications

Fast Camera Analysis of Plasma Instabilities in Hall Effect Thrusters Using a POD Method under Different Operating Regimes

Fast Camera Analysis of Plasma Instabilities in Hall Effect Thrusters Using a POD Method under Different Operating Regimes

A novel approach for optimal trajectory design with multiple operation modes of propulsion system, part 2

Distinct discharge modes in micro Hall thruster plasmas

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