Electrostatic Propulsion

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Electrostatic Propulsion
6.9 kW, LM 4 40 cm Ion Thruster (UM-NASA)
From PEPL Univer. Mich.
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Governing Equations

• mdv/dt dm/dt ve T Thrust
• Isp T/W ve/g0 Specific Impulse
• W dm/dt g0 Rate of Exhaust
• ?v ve ln m0/mt Increment of velocity

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3 Types of Thrusters

• Gridded Ion Thruster
• Field Emission Electric Propulsion (FEEP)
• Colloidal Thruster

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ION Thruster
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3 Sources of Ionization

• Electron Bombardment discharge

• Cesium Tungsten surface contact
• RF discharge
• (i.e. Microwaves used in Japan)

• Used less frequently

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FEEP/ Colloidal Thrusters
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FEEP/ Colloidal Thrusters

• High Specific Impulse (6000- 10,000 s)
• Very Low Low Thrust (1 µN 2mN)
• Low mass and space requirements\
• No moving parts
• Very High accuracy and controllability

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Applications

• Used for North-South Station Keeping on
  commercial Satellites since 1994(XIPS)
• Primary Propulsion for deep space probes (Deep
  Space 1 launched 1998)(NSTAR)
• FEEP/ Colloidal - For very small precise
  position adjustments for space craft

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Thrusters Operating
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4
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Advantages/ Limitations

• Efficient use of fuel (efficiencies 60-90)
• Provides thrust for longer amounts of time
• Can reach velocities up to 90,000m/s
• Uses inert gases no explosions

• Require large Power Systems
• Low Thrust Levels 0.5N (low acceleration)
• Must be used in a Vacume

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Future Prospects

• Research into new and better power supplies will
  allow farther reaching missions into space with
  larger payloads

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References

• Jahn, R. G. and Choueiri, E. Y., "Electric
  propulsion,"
• University of Michigan Plasmadynamics Electric
  Propulsion Laboratory
• European Space Agency
• NASA Glenn Research Center
• Centrospazio in Pisa
• Pics from Caltech