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chap8_1_50 - AAE 439 8 Electric Propulsion An Overview Ch8...

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AAE 439 Ch8 –1 8. Electric Propulsion An Overview
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AAE 439 Ch8 –2 OVERVIEW At the beginning of last century, Goddard experimented with electric gas discharge tubes recognizing basic concepts for Electric Propulsion. “Wege zur Raumschiffahrt” by Hermann Oberth, 1929. Since the 1950’s, Electric Propulsion has a well established research history in government, academia, and industry (US, Soviet Union, Europe, Japan). Since the mid 1980’s, the propulsion community has seen a boom in Electric Propulsion research. Since the early 1990’s: all major US communications satellite manufactures (such as Hughes, SS/LORAL, Lockheed-Martin) have embraced Electric Propulsion. Earth and Space Science Missions are increasingly baselined with Electric Propulsion (DS-1, EO-1, ST, CNSR, Mars Sample Return, etc.)
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AAE 439 Ch8 –3 OVERVIEW EP Statistics: EP Capability: East/West and North/South Station Keeping Orbit Transfer Orbit Insertion US Industry (GEO/LEO): 142 Hydrazine Arcjets ordered or in orbit Over 100 Hydrazine Resistojets in orbit 10 Xenon Ion Thrusters in orbit Russia: Over 100 Hall Thrusters in orbit European and Japanese satellite manufacturers increasingly baseline EP into spacecraft design.
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AAE 439 Ch8 –4 Flight History of EP Systems
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AAE 439 Ch8 –5 CHARACTERISTICS Chemical Propulsion Payload Propellant Power Thrust Exhaust (Momentum Flux) Thruster Powerplant Payload Propellant Thrust Exhaust (Momentum Flux) Engine Energy Limited Chemical bonding energy Limiting energy release Restricting specific impulse Low payload fraction Strong but short burns High thrusts and propellant mass flows Moderate exit velocities Limited final velocity Electric Propulsion Power Limited Energy conversion rate Material restrictions Separate power source Higher energy content supplied to propellant High specific impulse High exit velocities Low propellant consumption Low thrusts and acceleration High final velocities Short travel times
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AAE 439 Ch8 –6 ELECTRIC PROPULSION BENEFITS High Fuel Efficiency Enables Missions (High Isp) EP provides 2 to 10 times payload increases compared to chemical EP reduces trip time up to 3 times for many missions 0 0.1 0.2 0.3 0.4 0.5 0.6 Geosynchronous Neptune Orbiter Pluto Orbiter Jupiter Grand Tour Interstellar Precursor Payload Mass / Launch Mass Chemical Propulsion Electric Propulsion Courtesy of NASA GRC
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AAE 439 Ch8 –7 FUNDAMENTALS Definition: Electric propulsion is accomplished by the acceleration of gases by electrical and/or electric and magnetic forces acting on a conducting plasma made up of the propellant gas constituents. Electrical Energy Used to increase Potential Energy Potential Energy Converted to Kinetic Energy by Various Methods
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AAE 439 Ch8 –8 CLASSIFICATION E L E C T R I C S P A C E P R O P U L S I O N Electrostatic Systems Electromagnetic Systems Electrothermal Systems Arcjets Resistojet Thrusters
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