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Pocket Rocket: An electrothermal plasma micro-thruster

Greig, Amelia Diane

Description

Recently, an increase in use of micro-satellites constructed from commercial off the shelf (COTS) components has developed, to address the large costs associated with designing, testing and launching satellites. One particular type of micro-satellite of interest are CubeSats, which are modular 10 cm cubic satellites with total weight less than 1.33 kg. To assist with orbit boosting and attitude control of CubeSats, micro-propulsion systems are required, but...[Show more]

dc.contributor.authorGreig, Amelia Diane
dc.date.accessioned2016-06-21T06:21:54Z
dc.date.available2016-06-21T06:21:54Z
dc.identifier.otherb37881334
dc.identifier.urihttp://hdl.handle.net/1885/104495
dc.description.abstractRecently, an increase in use of micro-satellites constructed from commercial off the shelf (COTS) components has developed, to address the large costs associated with designing, testing and launching satellites. One particular type of micro-satellite of interest are CubeSats, which are modular 10 cm cubic satellites with total weight less than 1.33 kg. To assist with orbit boosting and attitude control of CubeSats, micro-propulsion systems are required, but are currently limited. A potential electrothermal plasma micro-thruster for use with CubeSats or other micro-satellites is under development at The Australian National University and forms the basis for this work. The thruster, known as ‘Pocket Rocket’, utilises neutral gas heating from ion-neutral collisions within a weakly ionised asymmetric plasma discharge, increasing the exhaust thermal velocity of the propellant gas, thereby producing higher thrust than if the propellant was emitted cold. In this work, neutral gas temperature of the Pocket Rocket discharge is studied in depth using rovibrational spectroscopy of the nitrogen (N2) second positive system (C3Πu → B3Πg), using both pure N2 and argon/N2 mixtures as the operating gas. Volume averaged steady state gas temperatures are measured for a range of operating conditions, with an analytical collisional model developed to verify experimental results. Results show that neutral gas heating is occurring with volume averaged steady state temperatures reaching 430 K in N2 and 1060 K for argon with 1% N2 at standard operating conditions of 1.5 Torr pressure and 10 W power input, demonstrating proof of concept for the Pocket Rocket thruster. Spatiotemporal profiles of gas temperature identify that the dominant heating mechanisms are ion-neutral collisions within the discharge and wall heating from ion bombardment of the thruster walls. To complement the experimental results, computational fluid dynamics (CFD) simulations using the commercial CFD-ACE+ package are performed. Simulation results demonstrate that the discharge is driven by ion induced secondary or ‘gamma’ electrons emitted from the surface of the plasma cavity radial wall in the vicinity of the powered electrode. These electrons are accelerated to high velocities through an enhanced sheath formed by the asymmetry of the device, creating a peak in ion density within the centre of the discharge tube.
dc.language.isoen
dc.subjectelectric propulsion
dc.subjectplasma propulsion
dc.subjectelectrothermal thruster
dc.subjectplasma physics
dc.subjectplasma heating
dc.subjection-neutral charge exchange collisions
dc.subjectcomputational fluid dynamics
dc.subjectplasma sheath
dc.subjectradio-frequency thruster
dc.subjectCubeSat propulsion
dc.subjectasymmetric plasma
dc.subjectrovibrational spectroscopy
dc.titlePocket Rocket: An electrothermal plasma micro-thruster
dc.typeThesis (PhD)
local.contributor.supervisorCharles, Christine
local.contributor.supervisorcontactchristine.charles@anu.edu.au
dcterms.valid2015
local.type.degreeDoctor of Philosophy (PhD)
dc.date.issued2015
local.contributor.affiliationDivision of Space Plasma, Power and Propulsion, Research School of Physics and Engineering, College of Physical and Mathematical Sciences, The Australian National University
local.identifier.doi10.25911/5d78d4c0688e7
local.mintdoimint
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