Dr Oliver Hitchens
Academic and research departments
Propulsion Group, Surrey Space Centre, Surrey Space Centre research, School of Mathematics and Physics.About
My research project
Performance increase of electron cyclotron resonance magnetic nozzle thruster via magnetically thickened resonance regionElectron Cyclotron Resonance (ECR) magnetic nozzle thrusters are a promising technology due to their electrodeless nature allowing for reduced erosion rates and extended lifetimes. Their simple design makes them relatively low-cost, however their typically low performance prevents them from becoming commercially viable. This thesis investigates multiple novel techniques to enhance the performance of ECR magnetic nozzle thrusters. Each is experimentally characterised to determine performance and the physical mechanism by which it is affected. The primary focus of this thesis is investigating the effect of the magnetic field strength gradient at resonance on the thruster performance. It was found analytically that decreasing the magnetic field strength gradient at resonance increases the thickness of the resonance region and the energy transferred from the microwaves to the electrons. This was then investigated experimentally using two different ECR thrusters. Using an electromagnet, the magnetic field strength gradient at resonance was decreased, resulting in an increase in thrust and specific impulse of 60 %, while thruster efficiency was increased by 16 %. By using an iron ring to decrease the magnetic field strength gradient at resonance, instead of an electromagnet, thrust and specific impulse increased by 15 %, while thruster efficiency increased by 32 %. The use of dual microwave frequencies at low-frequency separations was investigated and was found to increase thrust and specific impulse by up to 13 %. The effect of changing the resonance region location was also investigated, with the thrust found to decrease if the resonance region was located in the rear 8 mm of the thrusters 20 mm long chamber. Lastly, a magnetic mirror trap was implemented, which was found to decrease the propellant mass flow rate required for ignition and could increase the performance of miniaturised, low mass flow rate ECR thrusters.
Supervisors
Electron Cyclotron Resonance (ECR) magnetic nozzle thrusters are a promising technology due to their electrodeless nature allowing for reduced erosion rates and extended lifetimes. Their simple design makes them relatively low-cost, however their typically low performance prevents them from becoming commercially viable. This thesis investigates multiple novel techniques to enhance the performance of ECR magnetic nozzle thrusters. Each is experimentally characterised to determine performance and the physical mechanism by which it is affected. The primary focus of this thesis is investigating the effect of the magnetic field strength gradient at resonance on the thruster performance. It was found analytically that decreasing the magnetic field strength gradient at resonance increases the thickness of the resonance region and the energy transferred from the microwaves to the electrons. This was then investigated experimentally using two different ECR thrusters. Using an electromagnet, the magnetic field strength gradient at resonance was decreased, resulting in an increase in thrust and specific impulse of 60 %, while thruster efficiency was increased by 16 %. By using an iron ring to decrease the magnetic field strength gradient at resonance, instead of an electromagnet, thrust and specific impulse increased by 15 %, while thruster efficiency increased by 32 %. The use of dual microwave frequencies at low-frequency separations was investigated and was found to increase thrust and specific impulse by up to 13 %. The effect of changing the resonance region location was also investigated, with the thrust found to decrease if the resonance region was located in the rear 8 mm of the thrusters 20 mm long chamber. Lastly, a magnetic mirror trap was implemented, which was found to decrease the propellant mass flow rate required for ignition and could increase the performance of miniaturised, low mass flow rate ECR thrusters.
Testing of the Magnetically Thickened Resonance Region ECR Thruster, 2024
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In the media
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An electron cyclotron resonance (ECR) magnetic nozzle plasma thruster typically consists of a microwave antenna and a magnetic nozzle. The magnetic field forms a region where the propellant is resonantly heated and ionised by the microwaves. The ionised gas is then accelerated out of the magnetic nozzle, generating thrust. The design of these thrusters to date has not accounted for the thickness of the resonance region, often assuming it to be near zero. Two test campaigns have been conducted in which the thickness of the resonance region was varied. Larger resonance region thicknesses are seen to increase thrust and specific impulse by up to 60 % and thrust efficiency by up to 32 %. Experimental measurements of electron temperature, plasma potential and ion current indicate that increased electron heating in the larger resonance volume leads to a stronger electrostatic field and higher ion beam current. This study presents strong evidence that optimising for a thickened resonance region can significantly enhance thruster performance.
Electron Cyclotron Resonance (ECR) magnetic nozzle thrusters are a promising technology due to their electrodeless nature allowing for reduced erosion rates and extended lifetimes. Their simple design makes them relatively low-cost, however their typically low performance prevents them from becoming commercially viable. This thesis investigates multiple novel techniques to enhance the performance of ECR magnetic nozzle thrusters. Each is experimentally characterised to determine performance and the physical mechanism by which it is affected. The primary focus of this thesis is investigating the effect of the magnetic field strength gradient at resonance on the thruster performance. It was found analytically that decreasing the magnetic field strength gradient at resonance increases the thickness of the resonance region and the energy transferred from the microwaves to the electrons. This was then investigated experimentally using two different ECR thrusters. Using an electromagnet, the magnetic field strength gradient at resonance was decreased, resulting in an increase in thrust and specific impulse of 60 %, while thruster efficiency was increased by 16 %. By using an iron ring to decrease the magnetic field strength gradient at resonance, instead of an electromagnet, thrust and specific impulse increased by 15 %, while thruster efficiency increased by 32 %. The use of dual microwave frequencies at low-frequency separations was investigated and was found to increase thrust and specific impulse by up to 13 %. The effect of changing the resonance region location was also investigated, with the thrust found to decrease if the resonance region was located in the rear 8 mm of the thrusters 20 mm long chamber. Lastly, a magnetic mirror trap was implemented, which was found to decrease the propellant mass flow rate required for ignition and could increase the performance of miniaturised, low mass flow rate ECR thrusters.