Efficiency Mechanisms in Porous-Media Electrospray Thrusters

Natisin, Michael R.; Zamora, Henry L.; Holley, Zachary A.; Arnold, N. Ivan; McGehee, Will A.; Holmes, Michael; Eckhardt, Daniel

doi:10.2514/1.b38160

Cited by 20 publications

(5 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…ToF-based thrust measurements have been reported accurate to within about 15% of direct thrust measurements for capillary [ 8 ] and non-capillary [ 1 ] electrospray sources. ToF-based mass flow measurements are more variable, with reported errors ranging from a few percent for capillary sources [ 10 , 11 ] to over 60% for porous electrospray sources [ 2 ]. Furthermore, correlations between emitter current and propellant flow rate for capillary electrosprays of EMI-Im are highly variable, with reported values varying by more than ±30% across the literature [ 9 – 11 , 16 ].…”

Section: Resultsmentioning

confidence: 99%

A simple retarding-potential time-of-flight mass spectrometer for electrospray propulsion diagnostics

2023

View full text Add to dashboard Cite

The time-of-flight mass spectrometer (ToF-MS) is a useful tool for quantifying the performance of electrospray thrusters and characterizing their plumes. ToF-MS data can be used to calculate the mass-to-charge distribution in the plume, but the kinetic-energy-to-charge (i.e., the potential) distribution must be known first. Here we use a ToF-MS in tandem with a retarding potential (RP) analyzer. By sweeping the retarding potential through the range of potentials present in the plume, both the mass-to-charge distribution and the potential distribution can be measured independently. We demonstrate this technique in a case study using a capillary electrospray emitter and the ionic liquid propellant 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, abbreviated EMI-Im. We report a linear correlation between retarding potential and mass-to-charge ratio that agrees with published data from more complex orthogonal RP/ToF-MS instruments. Calculated values for the jet velocity and jet breakup potential match within 2% and 12%, respectively. Using conventional ToF-MS, we estimated the propellant flow rate and compared those estimates to direct flow rate measurements. For flow rates between 233 pL/s and 565 pL/s, the error in ToF-based flow rate estimates ranged from -16% to -13% when the plume potential was assumed to be a function of mass-to-charge. Assuming a constant plume potential yielded mixed results. However, using the average stopping potential measured by a retarding potential analyzer resulted in higher errors, ranging from -26% to -30%. Data and MATLAB code are included as supplemental materials so that readers can easily apply the techniques described here.

show abstract

Section: Resultsmentioning

confidence: 99%

A simple retarding-potential time-of-flight mass spectrometer for electrospray propulsion diagnostics

2023

View full text Add to dashboard Cite

show abstract

“…Therefore, it is likely that polarizable simulations may result in higher numbers of dimers and trimers that would compare more favorably with experimental data. Regarding neutral species, while measurements are limited in the literature and are not a part of this effort, future simulations could be used to investigate the reported anomalous mass loss [10] that may hinder electrospray performance.…”

Section: Resultsmentioning

confidence: 99%

“…When the local electrostatic pressure at the emitter tip exceeds an internal pressure by the surface tension of the ionic liquid, ions or droplets are extracted and accelerated, and then the thrust is provided to a spacecraft [8]. ILESTs can operate as either ionic liquid ion sources (ILIS) [9], where propellant is passively fed through an externally wetted emitter or porous material [10,11] to emit purely monomer ions, or a droplet-dominated emission mode, where propellant is actively fed through a capillary emitter [12].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of Ion Extraction from Nanodroplets for Ionic Liquid Electrospray Thrusters

et al. 2022

View full text Add to dashboard Cite

Molecular dynamics (MD) simulations were performed for ion extraction from electrospray thrusters to investigate relevant extraction processes numerically. To approximate the electrospray jet tip, a simulation domain consisting of 4-5 nm-sized ionic liquid droplets was used. The extracted ion angles and kinetic energies from EMI–BF4 (1-ethyl-3-methylimidazolium tetrafluoroborate) and EMI–Im (1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide) droplets were quantified by applying uniform electric fields of 1.3–1.7 V nm−1. The MD simulations are in great agreement with simulations presented in the literature and consistently show a greater preference for monomer emission than reported experimentally. At field strengths above 1.5 V nm−1, apparent droplet fracturing and breakup lead to an increase in ion angular velocity distributions. Greater mobility of EMI–BF4 ions than EMI–Im was also observed, indicative of the crucial role of cation-anion hydrogen bond strengths in ion extraction and beam composition between different propellants.

show abstract

“…Capillary emitters are difficult to emit ions in a purely ionic regime without charged droplets because of the low fluidic impedance of the capillary [15,22]. The porous emitters are now the most popular structures, and many studies have been conducted [13,16,17,[23][24][25][26][27]. The ionic liquid is supplied passively by the capillary force of the tiny pores.…”

Section: Introductionmentioning

confidence: 99%

Emission Measurements and in-situ Observation of Ionic Liquid Electrospray Thrusters with Longitudinally Grooved Emitters

Matsukawa

Nakashima

Takao

2023

Preprint

View full text Add to dashboard Cite

An externally wetted emitter array with longitudinally grooved structures for ionic liquid electrospray thrusters has been fabricated to improve the ionic liquid transport to the emitter tips. Two grooved emitter shapes with different groove depths were successfully fabricated using micro-electro-mechanical systems process techniques. We evaluated the current-voltage characteristics and conducted in-situ observation with a high-speed microscope. The experimental results of the ion emission have shown that the absolute emission current increases compared with our previous emitter without grooves. This tendency becomes stronger with deeper grooves. In addition, the slope of the current-voltage curve for grooved emitters does not decrease even when high voltages are applied, indicating that the grooved structure improves the ionic liquid transport to the emitter tips. However, it was found that deeper grooving also increased the percentage of the current intercepted by the extractor electrode. The high-speed microscope observation has shown that too much ionic liquid deposited on the extractor causes the ion emission from the extractor to the emitter, known as backspray, and implied that no large droplets are emitted for both grooved emitter structures.

show abstract

Efficiency Mechanisms in Porous-Media Electrospray Thrusters

Cited by 20 publications

References 20 publications

A simple retarding-potential time-of-flight mass spectrometer for electrospray propulsion diagnostics

A simple retarding-potential time-of-flight mass spectrometer for electrospray propulsion diagnostics

Molecular Dynamics Simulations of Ion Extraction from Nanodroplets for Ionic Liquid Electrospray Thrusters

Emission Measurements and in-situ Observation of Ionic Liquid Electrospray Thrusters with Longitudinally Grooved Emitters

Contact Info

Product

Resources

About