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  • Conference paper
    Schwertheim A, Knoll A, 2021,


  • Conference paper
    Staab D, Longhi E, Garbayo A, Swar K, Segovia-Guerrero L, Larsen H, Muir C, Knoll A, Ma C, Wilson S, Sadler J, Sheppard-Alden J, Rodier Cet al., 2021,


  • Conference paper
    Muir C, Ma C, Knoll A, 2021,

    The design, fabrication and test progress summary of the iridium catalysed electrolysis thruster

    , Space Propulsion 2020+1
  • Journal article
    Schwertheim A, Rosati Azevedo E, Liu G, Bosch Borràs E, Bianchi L, Knoll Aet al., 2021,

    Interlaboratory validation of a hanging pendulum thrust balance for electric propulsion testing

    , Review of Scientific Instruments, Vol: 92, Pages: 1-11, ISSN: 0034-6748

    A hanging pendulum thrust balance has been developed by Imperial College London in collaboration with the European Space Agency (ESA) to characterize a wide range of static fire electric propulsion and chemical micro-propulsion devices with thrust in the range of 1 mN to 1 N. The thrusters under investigation are mounted on a pendulum platform, which is suspended from the support structure using stainless steel flexures. The displacement of the platform is measured using an optical laser triangulation sensor. Thermal stability is ensured by a closed loop self-compensating heating system. The traceability and stability of the calibration are ensured using two separate calibration subsystems: a voice coil actuator and a servomotor pulley system. Two nearly identical thrust balances have been constructed, with one being tested in the Imperial Plasma Propulsion Laboratory and the other in the ESA Propulsion Laboratory. Both balances show a high degree of linearity in the range of 0.5 mN–100 mN. Both instruments have demonstrated a stable calibration over several days, with an estimated standard deviation on thrust measurements better than 0.27 mN for low thrust measurements. The same electric propulsion test article was used during both tests: a Quad Confinement Thruster (QCT) variant called QCT Phoenix. This thruster differed from previous QCT designs by having a newly optimized magnetic topology. The device produced thrust up to 2.21 ± 0.22 mN with a maximum specific impulse of 274 ± 41 s for an anode power range of 50 W–115 W.

  • Journal article
    Williams RD, Fabris AL, Knoll A, 2020,

    Insight into the plasma structure of the Quad Confinement Thruster using electron kinetic modelling

    , Acta Astronautica, Vol: 173, Pages: 111-118, ISSN: 0094-5765

    The behaviour of plasma within the discharge channel of the Quad Confinement Thruster is studied on the basis of electron kinetics. Here we propose that E × B drift of electrons drives the formation of unusual quadrant dependent light emitting structures observed experimentally in the discharge channel of the Quad Confinement Thruster. This assertion is made on the basis of a theory-based analysis and a computational model of the Quad Confinement Thruster. A particle orbit model of electron motion under the influence of applied electric and magnetic fields was used to assess electron transport. Structures strongly resembling that of the observed visible emission regions were found in the electron density distribution within the channel. While the motion of electrons cannot be decoupled from the motion of ions, as in this simple electron kinetic approximation, the results of this analysis strongly indicate the physical mechanism governing the formation of the non-uniform density distributions within the Quad Confinement Thruster channel.

  • Patent
    Knoll A, Harle T, Peter S, Frame T, Wantock Tet al., 2020,

    Plasma generation

    , US10595391B2

    A plasma torch having an open end from which a plasma plume is emitted in use is disclosed. The plasma torch includes a central cathode rod, a grounded conductive tube having an open end and being arranged around the cathode and spaced therefrom to form a first cylindrical cavity open at one end; and a high voltage electrode having a dielectric barrier material at a radially inward-facing surface thereof and being arranged around the grounded conductive tube and spaced apart therefrom to form a second annular cylindrical cavity open at one end. A constant direct current (DC) electrical power plus a high voltage pulsed electrical power is provided to the cathode producing an arc discharge in the first cavity between the cathode and grounded tube to generate a central thermal plasma emitted at an open end of the first cylindrical cavity. A high voltage alternating current electrical power or pulsed electrical power is provided to the high voltage electrode producing a dielectric barrier discharge in the second annular cylindrical cavity to generate a non-thermal plasma emitted from an open end of the second cavity as a halo around the central thermal plasma.

  • Conference paper
    Karadag B, Masillo S, Moloney R, Lucca Fabris A, Potterton T, Knoll A, Bianco Pet al., 2020,

    Experimental Investigation and Performance Optimization of the Halo thruster

    , 36th International Electric Propulsion Conference
  • Conference paper
    Mörtl M, Knoll A, Williams V, Shaw P, Argyriou V, Zamattio J, Pugliese Let al., 2020,

    Enhancing Hall Effect Thruster Simulations with Deep Recurrent Networks

    , 36th International Electric Propulsion Conference
  • Conference paper
    Schwertheim A, Knoll A, 2020,

    The Water Electrolysis Hall Effect Thruster (WET-HET): Paving the Way to Dual Mode Chemical-Electric Water Propulsion

    , 36th International Electric Propulsion Conference
  • Conference paper
    Williams V, Argyriou V, Shaw P, Montag C, Herdrich G, Knoll A, Mortl Met al., 2019,

    Development of PPTNet a Neural Network for the Rapid Prototyping of Pulsed Plasma Thrusters

    , 36th International Electric Propulsion Conference
  • Journal article
    Muir C, Knoll A, 2019,

    Catalytic Combustion of Hydrogen and Oxygen for an Electrolysis Micro-Propulsion System

    , Journal of the British Interplanetary Society, ISSN: 0007-084X
  • Journal article
    Schwertheim A, Knoll A, 2019,

    In situ Utilization of Water as a Propellant for a Next Generation Plasma Propulsion System

    , Journal of the British Interplanetary Society, ISSN: 0007-084X

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