Fragmentation in Time-of-Flight Spectrometry-Based Calculations of Ionic Electrospray Thruster Performance

Courtney, Daniel G.; Shea, Herbert

doi:10.2514/1.b35837

Cited by 18 publications

(9 citation statements)

References 17 publications

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“…We have shown in Ref. [32] that, if specific fragmentation transitions are assumed, F T (t) and F m (t) can be simply calculated using equations 4 and 5 respectively.…”

Section: Indirect Performance Calculationsmentioning

confidence: 99%

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Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Courtney

Dandavino

Shea

2016

Journal of Propulsion and Power

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Highly ionic beams of several hundred μA per cm 2 have been measured from porous glass ionic liquid electrospray sources fabricated using a conventional mill. The thrust output from three prototype devices, two emitting the ionic liquid EMI-Im and one emitting EMI-BF 4, was measured directly using a precise balance. Thrusts up to 50 μN were measured when emitting EMI-Im in a bipolar, alternating potential configuration at less than 0.8 W input power and with propellant supplied from an internal reservoir. Measurements of mass spectra via Time of Flight spectrometry, angle resolved current distributions, ion fragmentation and energy deficits have been applied to accurately calculate thrust and mass flow rates indirectly from the same devices. For two of three cases, calculated and directly measured thrusts were in agreement to within a few μN at input powers from 0.1 W to 0.8 W . Emissions of EMI-BF4 are shown to yield nearly purely ionic beams supporting high propulsive efficiencies and specific impulses, ∼ 65 % and > 3200 s respectively at 0.5 W . Conversely, greater polydispersity was observed in EMI-Im emissions, contributing to reduced specific performance, ∼ 50 % propulsive efficiency and ∼ 1500 s specific impulse at 0.5 W .

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“…We have shown in Ref. [32] that, if specific fragmentation transitions are assumed, F T (t) and F m (t) can be simply calculated using equations 4 and 5 respectively.…”

Section: Indirect Performance Calculationsmentioning

confidence: 99%

“…L is the ToF flight tube length and I(t) is the collected current as a function of flight time. The factors F T (t) and F m (t) are non-dimensional modifiers to the ToF integrand added to account for solvated ions which fragment after emission but prior to complete acceleration [32].…”

Section: Indirect Performance Calculationsmentioning

confidence: 99%

Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Courtney

Dandavino

Shea

2016

Journal of Propulsion and Power

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“…F(t) is a small correction factor accounting for ion fragmentation during acceleration. 23 Nondimensional flow rates / ion and / drop , due to ions and droplets, respectively, were determined via a scaling by m EMI I/e, the mass flow that would result if all species were singly charged and with mass m EMI ¼ 111.2 Da. These parameters 4 isolate changes in mass flow due to beam composition from those due to variances in the recorded current…”

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confidence: 99%

Influences of porous reservoir Laplace pressure on emissions from passively fed ionic liquid electrospray sources

Courtney

Shea

2015

Applied Physics Letters

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“…There it was shown, theoretically and experimentally, that the return of, relatively, low energy particles in the emitted beam can suppress charging. Particles with energy well below the total beam potential are known to be present due to ion or ion-cluster fragmentation downstream of emission [29,30]. While effective at maintaining charge neutralization to within several tens of percent of the beam voltage (positive or negative), those authors also demonstrated that acceleration of these heavy particles towards the thruster can induce damage.…”

Section: Passive Charge Neutralizationmentioning

confidence: 98%

Charge Neutralization and Direct Thrust Measurements from Bipolar Pairs of Ionic Electrospray Thrusters

Courtney¹,

Shea²,

Dannenmayer³

et al. 2018

Journal of Spacecraft and Rockets

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Electrospray (ES) thrusters are unique in their ability to emit both positive and negative beams, each contributing similarly to thrust. Spacecraft charging could be prevented without a dedicated neutralizer if currents of simultaneously emitted opposing polarity beams were matched; despite a lack of implicit coupling between them. We discuss and evaluate experimentally both an active current-balance control circuit and a passive self-balancing configuration. Our highly ionic ES source includes a pair of machined porous glass ES emitter arrays in a single holder. In the passive configuration, unbalanced charge collection on a common floating extractor yields rapid charging towards artificially imposed 200 V limits without means for charge suppression, showing the unsuitability of that architecture. Active balancing of emitted currents was fully effective at charge neutralization during stable periods of emission, yet insufficient during potential alternations. We present methods to improve this approach, including demonstrating beam current modulation at up to 450 Hz. Direct thrust measurements when simultaneously emitting opposing polarity beams of the ionic liquid 1-ethyl-3-methylimidazolium tetrauoroborate are presented. Direct thrust measurements up to 35 µN were in excellent agreement with commanded levels and computations based on measured currents (up to 190 µA) and voltages (up to 2100 V).

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Fragmentation in Time-of-Flight Spectrometry-Based Calculations of Ionic Electrospray Thruster Performance

Cited by 18 publications

References 17 publications

Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Influences of porous reservoir Laplace pressure on emissions from passively fed ionic liquid electrospray sources

Charge Neutralization and Direct Thrust Measurements from Bipolar Pairs of Ionic Electrospray Thrusters

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