Electrostatic Acceleration
An ion thruster strips electrons from propellant atoms to create positive ions, then accelerates them through a potential difference of 1000-3000 volts. The resulting exhaust velocity depends on the square root of the voltage-to-mass ratio: V_e = sqrt(2qV/m). Heavier ions like xenon (131 amu) produce more thrust per ion but lower exhaust velocity than lighter species. The simulation lets you explore this fundamental trade-off between thrust and specific impulse.
The Power-Thrust Relationship
Ion thrusters are power-limited, not propellant-limited. The input power scales as P = F × V_e / (2η), so higher exhaust velocity demands proportionally more electrical power for the same thrust. A typical 3 kW thruster produces only 100 mN of thrust — about the weight of a sheet of paper on Earth. But in the frictionless vacuum of space, this tiny force accumulates continuously over months.
Mission Applications
NASA's Dawn spacecraft used ion propulsion to orbit both Vesta and Ceres — the only spacecraft to orbit two different bodies beyond Earth. ESA's SMART-1 reached the Moon on just 82 kg of xenon. Starlink satellites use krypton Hall-effect thrusters for orbit raising and station keeping. Each application exploits the extraordinary propellant efficiency to accomplish missions impossible with chemical rockets.
Grid Erosion and Lifetime
The accelerator grid sits in a beam of energetic ions and slowly sputters away. Grid erosion is the primary life-limiting mechanism, with state-of-the-art thrusters achieving 50,000+ hours of operation. Carbon-carbon grids and advanced molybdenum alloys extend lifetime. The simulation's efficiency parameter captures losses from beam divergence, doubly-charged ions, and grid interception that all contribute to erosion.