1. AAE450 Senior Spacecraft Design Fred Ricchio Week 8: March 8 th, 2007 Propulsion Group Analysis of MPD Limitations

2. AAE450 Senior Spacecraft Design Alfven Critical Speed Hydrogen Characteristics –E = 1,312 kJ/mol –m = 1.00794 g/mol Alfven Critical Speed –V crit = 51,022.83 m/s –I sp = 5,202.88 s Max Requirements* –P elec = 5.12 MW –J = 21,890 A –V = 164 V Ricchio (1/4) Negative Effects –Cathode erosion –Reduced thruster lifetime –Increased IMLEO Positive Effects –Lower power requirement –Higher thrust –Faster trip time *Subject to change based on ΔV and mass changes

3. AAE450 Senior Spacecraft Design Experimental Research Argon Characteristics –E = 1,520.6 kJ/mol –m = 39.948 g/mol Alfven Critical Speed –V crit = 8,725.19 m/s –I sp = 889.72 s Observed Exhaust Speed 2 –V = 1.7 x 10 4 m/s Ricchio (2/4) Momentum transfer between gases one possible explanation for this effect 2

4. AAE450 Senior Spacecraft Design Calculations Ricchio (3/4)

5. AAE450 Senior Spacecraft Design References 1 ADAM P. BRUCKNER AND ROBERT G. JAHN AIAA Journal 1974 0001-1452 vol.12 no.9 (1198-1203) 2 TURCHI, P. J. (RandD Associates Washington Research Laboratory, Alexandria, VA) Journal of Propulsion and Power 1986 0748-4658 vol.2 no.5 (398-401) Ricchio (4/4)