Publications
88 results found
Lane O, Knoll AK, 2015, Quad Confinement Thruster – Industrialisation & Flight Integration, 34th International Electric Propulsion Conference
Wantock T, Ryan C, Harle T, et al., 2015, Initial performance characterisation of a plasma thruster employing magnetic null regions, 34th International Electric Propulsion Conference
Ahmed O, Knoll AK, 2015, Performance Characterisation of a Hybrid Propulsion System for Cubesat Missions, 51st AIAA/SAE/ASEE Joint Propulsion Conference
Kolbeck J, Lines D, Knoll AK, 2015, Experimental Investigation of an Aluminium Fuelled Vacuum Arc Thruster, 34th International Electric Propulsion Conference
Knoll A, Lamprou D, Lappas V, et al., 2015, Thrust balance characterization of a 200 W Quad Confinement Thruster for high thrust regimes, IEEE Transactions on Plasma Science, Vol: 43, Pages: 185-189, ISSN: 0093-3813
A thrust balance characterization of a low powered Quad Confinement Thruster is presented for high levels of propellant flow. The nominal flow rate for this device is between 1 and 2 sccm of xenon propellant. This paper extends the operating range, and investigates the performance at two high flow conditions of 10 and 20 sccm. Power is varied incrementally between 20 and 200 W in order to characterize the performance versus power trends of the device. It was found that for these high flow regimes the propellant is underutilized, and a proportion of the increased thrust can likely be attributed to a hot gas expansion of the neutral xenon rather than the generation of additional accelerated ions. The thrust was increased from 1 (nominal) to 3.3 mN at 200 W of input power for the 20 sccm condition. However, the performance penalty in terms of the specific impulse was considerable. The specific impulse under these conditions dropped below 200 s, where the nominal condition is 1000 s. A compromise between increased thrust and decreased performance was found at 10 sccm of flow: 3 mN of thrust at 300 s specific impulse.
Knoll A, Harle T, Lappas V, et al., 2014, Experimental performance characterization of a two-hundred-watt quad confinement thruster, Journal of Propulsion and Power, Vol: 30, Pages: 1445-1449, ISSN: 0748-4658
Thrust characterization experiments were carried out on a 200 W quad confinement thruster operating on xenon propellant. The thrust was measured using an inverted pendulum-type thrust stand. The anode power, propellant flow rate, and magnetic field were systematically varied in order to understand the impact of each parameter on the performance, which was characterized in terms of specific impulse, thrust, and thrust efficiency. At 200 W of anode power, the specific impulse of the device reached a maximum value of 860 s, and the thrust reached 3.2 mN. The thrust efficiency was modest, and it reached a maximum value of 4.6%. However, the thrust efficiency was found to depend strongly on the strength of the magnetic field. The quad confinement thruster device investigated in this study was limited to a maximum magnetic field of 250 G. Further improvements to the device can likely be achieved by applying much stronger magnetic fields.
Ahmed O, Knoll AK, Lappas V, 2014, Hybrid Propulsion System for CubeSat Mission Applications, Space Propulsion Conference 2014
Harle T, Knoll AK, Lappas V, 2014, Thrust Balance Characterization of the Halo Thruster using a Radio-Frequency Cathode Neutralizer, Space Propulsion Conference 2014
Knoll AK, Harle T, Lappas V, et al., 2014, Influence of Cathode Position on the Performance of the Quad Confinement Thruster, Space Propulsion Conference 2014
Harle T, Knoll AK, Lappas V, et al., 2013, Performance Measurements of a High Powered Quad Confinement Thruster, 33rd International Electric Propulsion Conference
Knoll AK, Lamprou D, Lappas V, et al., 2013, Thrust Balance Characterization of a 200W Quad Confinement Thruster for High Thrust Regimes, 33rd International Electric Propulsion Conference
Knoll AK, Thomas C, Gascon N, et al., 2012, Experimental Investigation of High Frequency Plasma Oscillations Within Hall Thrusters, 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit
Fernandez E, Knoll AK, Cappelli M, 2012, An Axial-Azimuthal Hybrid Simulation of Coaxial Hall Thrusters, 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit
Knoll AK, Gascon N, Cappelli M, 2012, Numerical Simulation of High Frequency Wave Coupling within a Hall Thruster, 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit
Knoll AK, Shafiq U, Lappas V, et al., 2012, 3-Dimensional Mapping of Plasma Properties in the Plume Region of the Quad Confinement Thruster, Space Propulsion 2012
Pottinger SJ, Lamprou D, Knoll AK, et al., 2012, Impact of plasma noise on a direct thrust measurement system, Review of Scientific Instruments, Vol: 83, ISSN: 0034-6748
<jats:p>In order to evaluate the accuracy and sensitivity of a pendulum-type thrust measurement system, a linear variable differential transformer (LVDT) and a laser optical displacement sensor have been used simultaneously to determine the displacement resulting from an applied thrust. The LVDT sensor uses an analog interface, whereas the laser sensor uses a digital interface to communicate the displacement readings to the data acquisition equipment. The data collected by both sensors show good agreement for static mass calibrations and validation with a cold gas thruster. However, the data obtained using the LVDT deviate significantly from that of the laser sensor when operating two varieties of plasma thrusters: a radio frequency (RF) driven plasma thruster, and a DC powered plasma thruster. Results establish that even with appropriate shielding and signal filtering the LVDT sensor is subject to plasma noise and radio frequency interactions which result in anomalous thrust readings. Experimental data show that the thrust determined using the LVDT system in a direct current plasma environment and a RF discharge is approximately a factor of three higher than the thrust values obtained using a laser sensor system for the operating conditions investigated. These findings are of significance to the electric propulsion community as LVDT sensors are often utilized in thrust measurement systems and accurate thrust measurement and the reproducibility of thrust data is key to analyzing thruster performance. Methods are proposed to evaluate system susceptibility to plasma noise and an effective filtering scheme presented for DC discharges.</jats:p>
Knoll AK, Melly B, Lappas V, 2011, The Quad Confinement Thruster - Preliminary Performance Characterization and Thrust Vector Control, 32nd International Electric Propulsion Conference
Knoll AK, Cappelli M, 2009, A multi-fluid 2-D simulation of a co-axial Hall plasma discharge, 62nd Annual Gaseous Electronics Conference
Knoll AK, Cappelli M, 2009, Experimental Characterization of High Frequency Instabilities within the Discharge Channel of a Hall Thruster, 31st International Electric Propulsion Conference
Lam C, Knoll AK, Cappelli M, 2009, Two-Dimensional (z-theta) Simulations of Hall Thruster Anomalous Transport, 31st International Electric Propulsion Conference
Knoll AK, Cappelli MA, 2008, A simple isentropic model of electron transport in Hall thrusters, Journal of Physics D: Applied Physics, Vol: 41, Pages: 162003-162003, ISSN: 0022-3727
Fernandez E, Knoll AK, Tarik K, et al., 2005, A Two-Dimensional Hybrid (z-theta) Simulation of Coaxial Hall Thrusters, 29th International Electric Propulsion Conference
Saraf S, Knoll AK, Pelletier F, et al., 2002, Investigating Formation Flying and COTS in an Integrated Simulation Environment, SpaceOps 2002 Conference
Saraf S, Knoll AK, Melanson P, et al., 2002, Development of a simulation environment to test space missions COTS technologies, DASIA 2002 - DAta Systems In Aerospace
Saraf S, Knoll AK, Tafazoli M, 2001, A Selection Methodology for Radiation-Hardened Processors, Avionics 2001
Saraf S, Knoll AK, Tafazoli M, 2001, Radiation Hardened Processors: A Comparative Study, Commercialization of Military and Space Electronics
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