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De Faoite D.,University College Dublin | Browne D.J.,University College Dublin | Del Valle Gamboa J.I.,Ad Astra Rocket Company | Stanton K.T.,University College Dublin
International Journal of Heat and Mass Transfer | Year: 2014

The heat flux incident upon the inner surface of a plasma discharge tube during a helicon plasma discharge was estimated using an inverse method. Temperature readings were taken from the outer surface of the tube using thermocouples, and the temperature data were interpolated over the tube surface. A numerical inverse procedure based on the Alifanov iterative regularisation method was used to reconstruct the heat flux on the tube inner surface as a function of space and time. In contrast to previously-used inverse models for this application, the current model implements a thermal radiation boundary condition to realistically model the energy exchange in the device. Additionally in these experiments, steady-state operation was reached, and the accurate modelling of the steady-state condition was facilitated by the thermal radiation boundary condition. The variation of heat flux with helicon discharge power, propellant flowrate, and electromagnet current was studied, and it was found that the waste heat flux increased with applied RF power and propellant flowrate, and decreased with current supplied to the electromagnets, over the range of parameter variation tested. © 2014 Elsevier Ltd. All rights reserved.


De Faoite D.,University College Dublin | Browne D.J.,University College Dublin | Chang-Diaz F.R.,Ad Astra Rocket Company | Stanton K.T.,University College Dublin
Journal of Materials Science | Year: 2012

The current review uses the material requirements of a new space propulsion device, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) as a basis for presenting the temperature-dependent properties of a range of dielectric ceramics, but data presented could be used in the engineering design of any ceramic component with complementary material requirements. A material is required for the gas containment tube (GCT) of VASIMR® to allow it to operate at higher power levels. The GCT's operating conditions place severe constraints on the choice of material. An electrically-insulating material is required with a high-thermal conductivity, lowdielectric loss factor, and high-thermal shock resistance. There is a lack of a representative set of temperaturedependent material property data for materials considered for this application and these are required for accurate thermo-structural modelling. This modelling would facilitate the selection of an optimum material for this component. The goal of this article is to determine the best material property data values for use in the materials selection and design of such components. A review of both experimentally and theoretically determined temperaturedependent and room temperature properties of several materials has been undertaken. Data extracted are presented by property. Properties reviewed are density, Young's, bulk and shear moduli, Poisson's ratio, tensile, flexural and compressive strength, thermal conductivity, specific heat capacity, thermal expansion coefficient, and the factors affecting maximum service temperature. Materials reviewed are alumina, aluminium nitride, beryllia, fused quartz, sialon, and silicon nitride. © Springer Science+Business Media, LLC 2012.


Trademark
Ad Astra Rocket Company | Date: 2009-03-24

Space vehicles, namely, rockets.


De Faoite D.,University College Dublin | Browne D.J.,University College Dublin | Del Valle Gamboa J.I.,Ad Astra Rocket Company | Stanton K.T.,University College Dublin
Applied Thermal Engineering | Year: 2016

Potential thermal management strategies for the plasma generation section of a VASIMR® high-power electric propulsion space thruster are assessed. The plasma is generated in a discharge tube using helicon waves. The plasma generation process causes a significant thermal load on the plasma discharge tube and on neighbouring components, caused by cross-field particle diffusion and UV radiation. Four potential cooling system design strategies are assessed to deal with this thermal load. Four polycrystalline ceramics are evaluated for use as the plasma discharge tube material: alumina, aluminium nitride, beryllia, and silicon nitride. A finite element analysis (FEA) method was used to model the steady-state temperature and stress fields resulting from the plasma heat flux. Of the four materials assessed, aluminium nitride would result in the lowest plasma discharge tube temperatures and stresses. It was found that a design consisting of a monolithic ceramic plasma containment tube fabricated from aluminium nitride would be capable of operating up to a power level of at least 250 kW. © 2015 Elsevier Ltd. All rights reserved.


Davis C.,ElectroDynamic Applications, Inc. | Gilchrist B.,University of Michigan | Squire J.,Ad Astra Rocket Company
Journal of Propulsion and Power | Year: 2011

This paper describes the experimental characterization of single-pass ion cyclotron resonance heating as applied to acceleration of ions for electric propulsion. A millimeter-wave interferometer system has shown to be a clear and simple method of quantifying ionacceleration due to ion cyclotron resonance heating. The experimental work was done on the VX-10 experiment of the variable specific impulse magnetoplasma rocket concept. The perpendicular velocity of the ions generated by ion cyclotron resonance heating was converted into axial velocity by the decreasing gradient of the axial magnetic field at the exhaust of the propulsion system from conservation of the magnet moment. This increase in axial velocity is predicted to cause a decrease in density due to conservation of current in the plasma. Interferometer density measurements were taken at three different locations on the VX-10 experiment upstream and downstream of the ion acceleration zone. A clear measurement of a 25% density drop for helium and a 40% density drop for deuterium was measured downstream of the ion resonance zone characteristic of ion acceleration. © 2010 bythe American Institute of Aeronautics and Astronautics, Inc.

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