Progress Toward a Variable Specific Impulse Electrospray Propulsion System

Coffman, Chase S.; Courtney, Daniel G.; Hicks, Fernando Mier; Jamil, Sara; Li, Hanqing; Lozano, Paulo

doi:10.2514/6.2011-5591

Cited by 12 publications

(10 citation statements)

References 9 publications

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“…It is tempting to broadly attribute this behavior to degradation due to electrochemical reactions at the ionic liquid to guard ring contact interface [2,44]. We have followed the most recent recommendations in the literature whenever possible: use of a the glass emitter substrate enforces a distal electrical contact [46] and attempts were made to balance positive and negative emission charge transfer over each period of potential alternation during thrust measurements [33,50]. However; long (>10 s) periods of sustained unipolar operation were unavoidable with the ToF and RPA systems as configured, and the efficacy of potential alternation to suppress reactions was not confirmed within our specific application.…”

Section: Emission Decay and Longevitymentioning

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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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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Section: Emission Decay and Longevitymentioning

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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“…2,3 The operational performance of the thruster was promising and merited further development, though several issues arose which needed to be improved upon. The first version of the iEPS thruster design included and all-silicon package, a porous nickel emitter array, and gold-coated silicon grids.…”

Section: Initial Thruster Developmentmentioning

confidence: 99%

“…It was suspected after investigation of failed devices that some of the conductive liquid was climbing the inner walls of the device and forming an electrical path between the emitter and extractor electrodes. 2,3 The main approach to solving this problem has been putting "obstacles" along the path between the emitter and grid layer.…”

Section: Iiib Liquid Current Leak Mitigationmentioning

confidence: 99%

Progress Toward Demonstration of Remote, Autonomous Attitude Control of a CubeSat Using Ion Electrospray Propulsion Systems

Perna¹,

Hicks²,

Coman³

et al. 2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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As a solution to the problem of scalable propulsion in small satellite architectures, the microfabricated ion Electrospray Propulsion System (iEPS) developed by MIT's Space Propulsion Laboratory has progressed to a point where it is ready to be characterized on a realistic testbed. In this paper, developments in the iEPS thruster design and testing equipment are outlined. Design changes address the performance and testing issues encountered with the first version. These changes include features to mitigate the formation of liquid current paths and ease grid-to-tip alignment and grid removal. Additionally, a 1-DOF free-floating CubeSat testbed with an integrated autonomous remote control system and high-voltage PPU has been developed and tested for use as a thrust balance and attitude control demonstrator.

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“…Duty cycle modulations have been employed to satisfy the later requirement for ILs with a propensity to emit higher currents in one polarity compared with another [33]. However; the practical benefits of such a solution are diminished in a bipolar configuration when satisfying constraint i).…”

Section: Compliance With Electrochemical Charge Balancingmentioning

confidence: 99%

“…This interfacial potential increases due to the collection of charges of one polarity or another. As previously identified [33,34], the currents emitted during each half period of operation must match to ensure zero total charge transfer on average. If this condition is not met, charge would gradually accrue over multiple periods that after some time must be dissipated through an electrochemical reaction or other discharge.…”

Section: Compliance With Electrochemical Charge Balancingmentioning

confidence: 99%

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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Progress Toward a Variable Specific Impulse Electrospray Propulsion System

Cited by 12 publications

References 9 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

Progress Toward Demonstration of Remote, Autonomous Attitude Control of a CubeSat Using Ion Electrospray Propulsion Systems

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

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