Space Propulsi Prof. manuel martinez- sanchez Lecture 18: Hall Thruster Efficiency For a given mass flow m and thrust f, we would like to minimize the running power P. Define a thruster efficiency (1) ere is the minimum required power. The actual power is V s。,°。°°· B p。,°°·引 Where Va is the accelerating voltage and Ia the current through the power supply (or anode current or also cathode current). Of the Ia current of electrons injected by the cathode a fraction IB goes to neutralize the beam and the rest iBs back-streams into the thruster Since no net current is lost to the walls, 16.522, Space P pessan Lecture 18 Prof. Manuel martinez Page 1 of 2016.522, Space Propulsion Lecture 18 Prof. Manuel Martinez-Sanchez Page 1 of 20 16.522, Space Propulsion Prof. Manuel Martinez-Sanchez Lecture 18: Hall Thruster Efficiency For a given mass flow m i and thrust F, we would like to minimize the running power P. Define a thruster efficiency 2 F = 2m P ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ η i (1) where 2 F 2m ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ i is the minimum required power. The actual power is P=IVa a (2) Where Va is the accelerating voltage and Ia the current through the power supply (or anode current, or also cathode current). Of the Ia current of electrons injected by the cathode, a fraction IB goes to neutralize the beam, and the rest, IBS back-streams into the thruster. Since no net current is lost to the walls, a B BS I =I +I (3) } Va (IB) e (IB) i IBS IBS Ia (IB) e