Evaluation of Pulsed Plasma Thruster Micropulsing

This paper evaluates the concept of pulsed plasma thruster (PPT) micropulsing. Micropulsing was a premise behind a power processing unit (PPU) and an energy storage unit ( ESU ) design that for certain mission profiles, it was advantageous to operat e a PPT at lower energy but higher frequency rather than a t a higher energy but lower frequency. This premise allows for reductions in the ESU volume and mass without paying a penalty in thrust . To complete the evaluation, a n independent spark plug initiation unit, a high voltage power supply and a variety of mica foil capacitors at 2.6, 5, 10 and 20 ∝F w ere used to conduct a series of tests on a single PPT to map performance level s of thrust, impulse bit, efficiency and specific impulse over a comparable power range . Testing at NASA Glenn Research Cen ter was conducted with breadboard PPT hardware . The test results showed that operating in the lower energy ESU micropulsing mode produce d similar thrust levels to a higher energy ESU operating at high power level . Further testing however showed a reduct ion in specific impulse and efficiency when the smaller capacitances were used at the highest power levels. This would require more fuel mass for a mission that was predominately high power, potentially negating the ESU mass savings. Therefore, micropulsin g is advantageous w here most of a mission profile occurs at low power , but retains the ability to conduct high thrust maneuvers when necessary .