Ionic versus Chemical Propulsion: A Comparative Study

Abstract

As satellites become increasingly central to global communication and navigation, maintaining their precise orbital positioning has become a critical and recurring challenge. Satellites in geostationary orbit experience orbital drift caused by Earth's uneven gravitational field, requiring frequent station-keeping maneuvers throughout their operational lifetimes. This study compares two propulsion methods commonly used for these corrections—the SPT-140 Hall-effect ion thruster and the R-42 bipropellant rocket engine—to determine which is optimal for orbital drift correction. Using a representative scenario of a 6,600 kg communications satellite drifting 0.05° from its assigned position in geostationary orbit, both engines were evaluated under identical mission conditions across thrust output, specific impulse, and operational cost. A sensitivity analysis varied each thrust parameter from 50% to 150% of its standard value to assess reliability, and the thrust and impulse required for the maneuver were calculated and compared against each engine's capabilities. The results show that while the R-42 produces over 11,000 times more thrust, this excess power is a liability for fine maneuvering, limiting it to a burn of roughly 0.04 seconds compared to the SPT-140's controllable 489-second burn. The SPT-140's specific impulse of 2,100 seconds far exceeds the R-42's ~312 seconds, and despite its costlier xenon propellant, its high fuel efficiency reduces operating cost to approximately $1.00 per minute versus the R-42's $4,275.00. These findings indicate that the SPT-140 ion thruster is the superior choice for orbital drift correction, offering greater precision, efficiency, and cost-effectiveness for routine satellite station-keeping.