Electric propulsion


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Electric propulsion

  1. 1. Electric Propulsion
  2. 2. Most commonly used Rocket Engines!!! Chemical Rocket Engines
  3. 3. Criteria for rating Rocket performance • Specific Impulse • Weight of the Engine
  4. 4. What is Electric Propulsion (EP)?? The acceleration of gases for the purpose of producing propulsive thrust by electric heating, electric body forces, and/or electric and magnetic body forces.
  5. 5. Specific Impulses of Various Propulsions  Solid & Liquid Propellants (In use) 250 s  Best Liquid Propellants 350s  Nuclear Rockets 1200 s  Ion Engine 20,000 s
  6. 6. Electric Propulsion 1) • Electrothermal Propulsion • Propellant is electrically heated in some chamber and then expanded through a suitable nozzle to obtain thrust. 2) • Electrostatic Propulsion • Propellant is accelerated by direct application of electrostatic forces to ionized particles. 3) • Electromagnetic Propulsion • Propellant is accelerated under the combined action of electric and magnetic fields.
  7. 7. Electrothermal Propulsion  Three Subclasses of this family:(Propellant heating)  A)Resistojets : Heat is transferred to the propellant from some solid surface, such as the chamber wall or a heater coil.  B) Arcjets : Propellant is heated by an electric arc driven through it  C)Radiatively Heated Devices: Highfrequency radiation heats the flow
  8. 8. Resistojets  Chamber Temperature : 3000K , thus limiting the exhaust velocity not exceeding more than 10km/sec. (~3500m/s)  Propellant : Catalytically decomposed hydrazine  Advantages : Low operational Voltage Avoids complex power processing  In Use : INTEL SAT V series - 1980  Recent application : Attitude control, Orbit insertion and deorbit of LEO satellites, including 72 satellites in the Iridium Constellation.
  9. 9. Arcjets  Temperature range should be of 10,000 K to reach exhaust speeds greater than 10,000m/s.  Effective means : Passing an electric arc directly through the chamber.  3 segments Cathode Fall Region Arc Column Anode Fall Region
  10. 10.  Telstar-4 series of GEO communication satellites – 1993 Limitations: 1)Difficulty of providing high power in space. 2)Lifetime limiting problems of electrode erosion. 3) Whiskering.
  11. 11. Ion Engine • Scheme of a gridded ion engine with neutralization
  12. 12. Ion Engine NASA’s Deep Space One Ion Engine
  13. 13. Ion Engine NASA’s Evolutionary Xenon Thruster (NEXT) at NASA’s JPL
  14. 14. Hall Thruster The Hall effect
  15. 15. Electric Propulsion Applications 1. ISS 2. Interplanetary Missions 3. Commercial/Defense
  16. 16. Conclusion    Electric thrusters in general are about 1.5 times as efficient as a good chemical propulsion system A parameter called an specific impulse comes into play here. (~20,000 s) So why use an electric thruster? If the mission is not time sensitive an electric propulsion system will use less fuel, and therefore cost less to launch into space. On average it currently costs about $10,000 for every kilogram launched into low Earth orbit. Therefore if time is not a crucial issue the delay can be worth the money saved at launch.
  17. 17. THANK YOU!!  Presented By : V SHYAM PRASADA RAO shyamforever@live.com