1,720,982 research outputs found
A miniature electrospray thruster for precise attitude control of a nanosatellite
No full textThis paper introduces a miniature electrospray thruster, and investigates its feasibility of working as an attitude control actuator on CubeSat. The miniature thruster has a conically-shaped porous glass emitter, a porous nickel propellant reservoir and a 3D printed thruster casing. The propellant is passively fed through the porous structures using capillary action, resulting in a pressure-free and highly-compact thruster. The size of the thruster is approximately 1 × 1 × 2 cm with a total mass less than 10 g excluding a power control system. The thruster was tested in a vacuum chamber at the University of Southampton. Its thrust varied from 0.1 μN at ±2,600 V to 3 μN at ±2,900 V with a specific impulse higher than 6,800 s with a maximum power of 0.14 W. Based on the thruster specifications and test results, a hypothetical Earth-pointing 3 U CubeSat at a sun-synchronous orbit with an altitude of 500 km was used to analyse the attitude control and orbit maintenance performance of this miniature electrospray thruster. This analytical attitude and orbit control system uses a 16- thruster-configuration and a pulse-width-pulse-frequency modulation. Major orbital disturbances, including atmospheric drag, solar radiation pressure, magnetic field torques and gravity gradients, were considered in the analysis. This study suggests that the miniature electrospray thruster can enable precise attitude control with an accuracy of less than to 0.1 degree and orbit maintenance lifetime of about 6 years for a 3 U CubeSat at a 500 km altitude.</p
Investigating the ions emitted by multiply charged ionic liquids from a porous electrospray ion source
No full textA porous electrospray ion source was tested with three ionic liquids in order to investigate the effects of ionic liquid properties on the sizes of ion clusters emitted by purely ionic electrospray sources. Two of the ionic liquids, bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate and 1,6-bis(3-methylimidazolium-1-yl) hexanebis(trifluoromethylsulfonyl)amide, were selected due to them having a dication or dianion, which were termed multiply charged ionic liquids due to them containing anions or cations with more than one charge within them. These were selected in order to investigate ionic clustering within electrospray ion emission, and were compared against one of the most common ionic liquids, EMI-BF4. The current-voltage data showed that EMI-BF4 emitted similar levels of current to bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate, even though the latter liquid had significantly lower conductivity and higher viscosity, suggesting an improvement in current speculated to be due to the extra charges contained by the ions. TOF and RPA data are provided, showing all three liquids emitting only ions comprising of monomers, dimers, trimers and quadramers, with some of the 1,6-bis(3-methylimidazolium-1-yl) hexanebis(trifluoromethylsulfonyl)amide data indicating heavier species emission. The data also suggested that the multiply charged ionic liquids produced ions which have two anions or cations attached, termed ‘double ions’, with these ions have not been previously reported using porous electrospray sources. Furthermore it was found that the dimers emitted by both of the multiply charged ionic liquids seemed to be more stable than EMI-BF4 dimers, providing insight into ion cluster formation
In-situ lunar propellants for hall effect thrusters
No full textThis paper explores the potential of using lunar resources, specifically magnesium and calcium, as electric propulsion propellants, aiming to facilitate more sustainable space exploration and enable innovative mission architectures. These elements are abundant in the lunar regolith and have a sufficiently high vapour pressure to support the operation of Hall effect thrusters. Sublimation rates have been determined through tests conducted within a vacuum chamber. Conductive heating of the magnesium in granular form resulted in a sublimation rate of approximately 0.94 mg/s at 524.27°C, slightly lower than predicted. Difficulties encountered during in-situ mass measurements have been detailed. To initiate the next stage of the project, propellant storage and delivery system concepts have been created to integrate the sublimation method into a Hall effect thruster propulsion system
Dataset for Thesis: Time-of-flight characterisation of alternative propellants for porous Electrospray thrusters
No full textThis dataset contains:
.txt files for: Current-Voltage, Retarding Potential data
.csv files for: TOF, emitter height and radius data.
.m files for: MATLAB Code used for analysis.
</span
Exploring the influence of metal-based anions on the plume of a porous electrospray emitter
No full text
Investigating the evolution of ionic liquid Taylor cones in porous electrospray thrusters through direct optical visualisation
No full textElectrospray ion thrusters are well suited to small satellites, or for spacecraft with fine pointing requirements, but suffer from limited lifetimes and off-axis emission. Limiting off-axis emission promises to improve performance and lifetimes. This paper utilises direct experimental visualisation of Taylor cones on single porous electrospray emitters to better understand the rich physics of electrospray emission - presenting what is believed to be the first direct experimental measurement of the Taylor cone half-angle on porous emitters, in addition to an examination of the concavity and evolution of the Taylor cone with time and voltage. Broadly, the Taylor cone was found to match trends found in electrospray thruster models for single site emission, with the Taylor cone adopting a flatter structure with increased voltage. This did not, however, hold true in the presence of multiple emission sites. Finally, the Taylor cone behaviour and location appeared to be dominated by the surface topology of the emitter
Analysis of plumes produced by novel ionic liquids in electrospray thrusters
No full textA single emitter electrospray thruster was tested with four ionic liquids, which have not been tested before, in order to investigate the physics of ion emission. Two of these ionic liquids had metal/metalloid halides anions, similar to 1-ethyl-3-methylimidazolium tetrafluroborate, and were found to emit similar to greater currents than typically found with EMIBF4. 1-Ethyl-3-methylimidazolium tetrachloroferrate was found to emit up to +50.7/-33.6µA and 1-ethyl-3-methylimidazolium hexafluoroantimonate up to +12.6/-14.5 µA, compared to +18.3/-9.3 µA for 1-ethyl-3-methylimidazolium tetrafluoroborate. Two further propellants were investigated formed of very novel ionic liquids which have multiple charges on the ions within them, and hence termed multiply charged ionic liquids. These were found to emit reduced currents, with up to +11.4/-5.3 µA by bis(3-methylimidazolium) hexyltetrakis (hexathiocyanato) cobaltate and up to +2.1/-2.2 µA being emitted by tris(1-hexyl-3-methylimidazolium) dysprosium(III) hexathiocyanate. All four of these ionic liquids were shown to emit a purely ionic plume, despite having widely varying propellant properties
Effect of channel width on the performance of a modular hall effect thruster operating on xenon, krypton, and argon
No full textDataset supporting the University of Southampton Doctoral Thesis "Towards a stable, flexible and efficient computational fluid dynamics toolkit for re-entry vehicle design optimisation - development, characterisation and initial findings"
No full textDataset supporting the University of Southampton Doctoral Thesis "Towards a stable, flexible and efficient computational fluid dynamics toolkit for re-entry vehicle design optimisation - development, characterisation and initial findings"
This dataset consists of raw simulation output generated using the software OP2A. The data files suffixed with .plt are to be visualised with Tecplot, whilst those with .dat file extensions can be visualised using Python's matplotlib, or any similar software. Data is divided into 0d, 2d and 2d axisymmetric datasets, in line with presentation in the thesis. Data includes, the specific data presented within the thesis as well as that of the convergence process. Final data files (those whose visualisations are presented in the thesis) can be ascertained by the highest iteration number present within filenames.
</span
- …
