Performance Scaling of Gas-Fed Pulsed Plasma Thrusters Prepared by:

The performance scaling of gas-fed pulsed plasma thrusters (GFPPTs) is in-vestigated theoretically and experimentally. Analytical models of the discharge current suggest that close to critically damped current waveforms provide the best energy transfer efficiency. A characteristic velocity for GFPPTs that depends on the inductance-per-unit-length and the square root of the capacitance-to-initial-inductance ratio is also derived in these models. The total efficiency is predicted to be proportional to the ratio of the exhaust velocity to the GFPPT characteristic velocity. A numerical non-dimensional model is used to span a large parameter space of possible operating conditions and suggest optimal configurations. From the non-dimensional model, the exhaust velocity is predicted to scale with a non-dimensional parameter called the dynamic impedance parameter to a power that depends on the mass loading prior to the discharge. To test the validity of the predicted scaling relations, the performance of two rapid-pulse-rate GFPPT designs, PT5 (coaxial electrodes) and PT9 (parallel-plat