Connecting Ablative and Gas-Fed Propellant Utilization in Electromagnetic Thrusters

Electromagnetic propulsion systems are fundamentally limited by poor propellant utilization and life-limiting electrode erosion. While conventional architectures are categorized as gas-fed or solid-ablative based on propellant type, this study demonstrates a continuous operational spectrum defined by the electron-to-neutral ratio during the discharge. We characterize this transition in a coaxial pulsed plasma accelerator, sweeping from gas-dominant to ablation-dominant modes. A multidiagnostic approach identifies explosive cathode spots as the primary erosion mechanism. In the gas-starved regime, ablation rates reach [Formula: see text], driven by the ejection of 0.85 μm copper particles. The particle number density increases with peak current (from [Formula: see text] to [Formula: see text]). Performance measurements confirm that a transition from pure gas-fed operation to ablative operation occurs, resulting in the thrust-to-power ratio rising from [Formula: see text] due to entrained electrode mass. The use of a refractory tungsten cathode delays the onset of this transition. Maintaining operation below the propellant starvation threshold was also found to reduce the magnitude of ablative erosion.