Electric Propulsion at the university of Southampton. S B Gabriel, I Golosnoy and A Daykin- Iliopoulos

Transcription

1 Electric Propulsion at the university of Southampton S B Gabriel, I Golosnoy and A Daykin- Iliopoulos sbg2@soton.ac.uk

2 Topics Background Previous work Current research Future ideas

3 Electric Propulsion at the University of Southampton Nearly 30 years of research( applied and fundamental) on electric propulsion including: Hollow cathodes and hollow cathode thrusters Gridded ion engines Pulsed plasma thrusters Microcolloid thrusters(mems) About 20 PhD students ( > 1/3 now working in EP at ESA, QinetiQ, Brazil and Mars Space Ltd) Spin-off company, Mars Space Ltd, formed in 2007 Close collaboration with QinetiQ 3

4 Previous work Diagnostics Spectroscopy of interior plasma(pottinger) Langmuir probe of baffle annulus region(turbulent heating)(milligan) Alternative propellants Argon, Krypton, noble gas mixtures(penning)(edwards,rudwan) Life model prediction for BaCaO dispenser cathodes(coletti) PPTs ( Ciaralli, Guarducci) Hollow cathode thrusters( Gessini, Grubisic, Frollani) 300s with QinetiQ T cathode on Xenon( basis of Mars Space HC model) Direct thrust measurement Effect of applied magnetic field 180A cathode designed, built(qinetiq) and run for several hundred hours(hiper)

5 Facilities VC2 ~ 1m diameter x 0.5m long, 450l/s turbomolecular VC1 ~ 0.6m diameter x 1.5m long, 8600l/s turbo pumps(2 4300l/s) VC3 spherical 0.35m diameter, 400l/s turbo ( to be upgraded to 2200l/s) Figure 3 Test facility for the HCA, TDHVL-VC2

6 Current work Heaterless hollow cathode Alternative propellants for GIEs(GIESEPP) Liquid PPTs Spectroscopic diagnostics

7 Intensity, a.u. Plasma Diagnostics(1) Small or Large areas Image projected to optical fibres Time-resolved snapshot or Total radiation Spectrograph & CCD PI Acton Series SP-2750 Pi-MAX3 iccd Resolution nm for 2400 l/mm with instant cover of 4 nm wavelengths range Resolution 0. 5 nm for 150 l/mm with instant cover of 100 nm wavelengths range High speed gating up to 3 ns with 40 ps triggering Wavelength, nm Xe Xe+Kr

8 Plasma Diagnostics(2) Electron temperature from continuum Electron density from hydrogen lines Slope taken for 2-3 ev photon range Electron T(eV)=1/slope 2 separate profiles are needed to account for nonuniform plasma Atomic lines Hydrogen Balmer Collisional-radiative model AlO lines AlO lines

9 Liquid PPT Auxiliary electrode for ignition Field enhancement assistance for ignition Liquid motion Controllable time delay

10 Heaterless hollow cathode overview Laboratory model lanthanum hexaboride heaterless hollow cathode Molybdenum cathode tube LaB 6 emitter with interface sleeve POCO graphite keeper Keeper-cathode separation, 2 mm Reduced keeper orifice diameter, 0.25 mm o Increases cathode-keeper pressure for relatively low ignition voltage/flow o Currently very small, to be incrementally drilled out for further investigations Instrumentation Four integrated thermocouples o Type C (tungsten-rhenium) thermocouples o Sheathed in alumina tubing o Embedded in graphite sleeve o Placed at equal increments along emitter Pyrometer measurements o Disappearing filament optical pyrometer o Measurements at emitter tip Type C thermocouples Mounting bolts Molybdenum cathode tube Radiation foil casing Graphite emitter sleeve Figure 1: Heaterless hollow cathode overview Enclosed POCO keeper Lanthanum hexaboride emitter Radiation insulating foil Alumina two bore thermocouple tubing Figure 2: Thermocouple positioning

11 Heaterless hollow cathode Conclusions A modular LaB 6 heaterless hollow cathode has demonstrated stable ignition from room temperature to over 1400 C in nominal operation o Ignition is achievable in 50 seconds o HHC operated reliable up to 8 A at 1.75 sccm and down to 0.2 sccm (Xe) at 5 A The ignition profile has been characterized o The emitter temperature is highest centrally before changing to the emitter tip. o Full ignition requires W, 50 s Figure 12: HHC Keeper only discharge, 1.75 SCCM, 2 A Steady state operation from 5 to 8 A o Highest temperatures remain at emitter tip o Operational power 123 W at 5 A to 154 W at 8 A

12 Krypton Operation with krypton similar to xenon but in general higher mass flow rates required for spot mode and anode potentials were higher than with xenon at the same current. Xe and Kr discharge V-I characteristics between 10 and 40A At 10A, 30 sccm of krypton gives approximately the same anode potential of approximately 22V with a flow rate of 20 sccm of xenon at this same flow rate of krypton, the anode potentials are 3 and 5 V higher at currents of 15A and 20 A, respectively At higher currents of 30 and 40A, Kr flow rates of 50 and 40 sccm, respectively are needed to get about the same anode potentials with Xe at 20 sccm

13 Future Work Low current, propellantless cathodes Novel geometries for heaterless hollow cathodes New concepts for starting cathodes High current heaterless cathodes Methods of overcoming ion acoustic instability/plasma instabilities ( spot to plume transition) Alternative propellants for EP thrusters Hybrid GIE/HET thruster

14 Than you and any questions