Ion Propulsion

1
Ion Propulsion
by Kevin Geohagan
2
Outline

• Rocket Theory
• The Advantage of Ion Propulsion
• The Disadvantage of Ion Propulsion
• Ion Propulsion Systems
• Ion thruster
• Hall-effect thruster
• Plasma thruster

3
Rocket Theory

• Rocket Equation
• FdT MdV
• F (dM/dT)Vexhaust
• M/M0 e(-Vfinal/Vexhaust)
• Gives the ratio of ending to starting mass given
  the final intended velocity and the exhaust
  velocity and vice versa
• Specific Impulse
• Isp F/(dM/dTg)
• Relates engine thrust to propellant mass used as
  a measure of efficiency

4
The Advantage of Ion Propulsion

• Higher exhaust velocity
• 30 40 km/s compared to chemical rockets 3
  5 km/s
• FdT MdV increase exhaust velocity, decrease
  exhaust mass
• Leads to lower propellant/total mass ratios,
  higher Isp (higher efficiency)

5
The Advantage of Ion Propulsion
6
The Disadvantage of Ion Propulsion

• Low Thrust
• Typically about .02 lbs or .1 N
• Because of the low thrust, ion thrusters are
  incapable of reaching orbit independently

7
The Disadvantage of Ion Propulsion
8
Systems Ion Thruster

• Based on electrostatic acceleration of Xenon ions
  (acceleration using electric fields)
• Isp values upwards of 4000 s
• (Space Shuttle main engines have Isp of 455 s)
• Current Ion Thruster Systems
• NSTAR (Deep Space 1)
• NEXT
• XIPS

9
Systems Ion Thruster
10
Systems Hall-Effect Thruster

• Xenon Ions accelerated electrostatically, but
  without charged grids.
• Typical Isp values of 1500 4000 s
• Current Hall Thruster Systems
• PPS-1350 (ESAs SMART-1 Probe)

11
Systems Hall-Effect Thruster
12
Systems Plasma Thruster

• Use ion-magnetic field interaction as a means to
  contain high energy plasma, which is heated and
  expanded to create thrust
• Isp values are variable up to 30000 s

13
VASIMR Plasma Thruster
14

• Theory, Rocket Equation
• Pros/Cons of Ion Propulsion
• High efficiency, Low thrust
• Ion Propulsion Systems
• Ion Thruster NSTAR, NEXT, XIPS
• Hall Thruster SMART-1s thruster
• Plasma Thruster VASIMR

15
Questions?