Physics / mechanism
Electric propulsion (EP) accelerates ionised propellant using electromagnetic fields rather than combustion, decoupling thrust from chemical energy limits. Hall-effect thrusters (HETs) trap electrons in a crossed E×B field, ionise xenon or krypton, and electrostatically accelerate ions; specific impulse (Isp) 1,500–3,000 s, thrust 5–500 mN per unit, power 200 W–20 kW. Gridded ion engines run higher Isp (3,000–10,000 s) at lower thrust density. State of the art: SPT-140-class HETs at ~3 kW, flight-proven on GEO comsats and LEO constellations (Starlink uses krypton HETs). Efficiency (thrust/power) 50–65%. Key scaling constraint: erosion of discharge channel ceramics (BN, BN-SiC composites) limits lifetime.
Competitive landscape
HETs compete with cold-gas (simplest, low Isp ~50 s), resistojets (moderate Isp ~150–300 s), and green-monopropellant thrusters for small satellites. Pulsed plasma and electrospray (FEEP) thrusters target sub-100 W CubeSat niches. Chemical bipropellant remains dominant where high instantaneous thrust is required (orbit insertion, deorbit).
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.