Compare different types of electric propulsion systems.

Electrothermal: Resistojets - electrically heated propellant, Isp ~300 s; Arcjets - arc-heated propellant, Isp ~500-600 s. Low-complexity, moderate performance. Electrostatic: Ion engines (gridded) - ionize propellant, accelerate through charged grids, Isp 3000-5000 s, power-limited thrust (Dawn mission used this). Hall-effect thrusters - electrons spiral in magnetic field, accelerate ions, Isp 1500-3000 s, higher thrust density than gridded ion. Electromagnetic: Pulsed plasma thrusters (PPT) - ablates and accelerates Teflon, simple but low efficiency; Magnetoplasmadynamic (MPD) - electromagnetic Lorentz force, high power. Selection: Mission delta-v requirement, Available power, Thrust needs (orbit raising time), and Propellant storage. Hall thrusters dominant for commercial GEO satellites. Ion engines for high-delta-v science missions.