Evaluation of pulsed plasma thruster electrical components

Abstract

The pulsed plasma thruster electrical components evaluated under this test program include a breadboard power processor unit (PPU), energy storage units (ESUs) or capacitors, discharge initiation (DI) electronics and sparkplugs. The main objectives of the breadboard test program are to characterize the efficiency of the PPU main charge circuit and the ESU, to validate the ability of a single PPU to operate multiple ESUs with multiple thruster sites, and to validate the effectiveness of the 'micropulsing' concept as a way to provide throttling and a reduction in system mass. Under an on-going component evaluation program, tests with breadboard electrical components have been completed to demonstrate benchtop functionality, to quantify electrical component performance, to demonstrate vacuum functionality, and to measure thrust throttling capabilities. During the benchtop functionality tests, the PPU was successfully operated over a range of input voltages and output ESU charge voltages. The maximum peak input current to the PPU was less than 9.8 amperes for all conditions tested. The PPU conversion efficiencies ranged from 83 to 87 percent, while the PPU charge efficiencies ranged from 80.1 to 83.7 percent for a nominal input voltage of 28 volts. The equivalent series resistance (ESR) for all ESUs(micafoil capacitors) ranged from 5.0 to 11.4 milliohms with an average ESR of 8.75 milliohms. The PPU, ESU, and DI were successfully operated with two PPT thruster configurations over a nominal range of ESU energies and pulse repetition rates. The constant thrust-to-power ratios, demonstrated for all PPT configurations, were ideal for micropulsing over a range of operating conditions.