Characterization of a 10 W class electrospray array thruster
Collin B. Whittaker, Steven Arestie, Colleen Marrese-Reading, Benjamin Jorns
Abstract
Abstract A porous conical type electrospray array thruster consisting of 6102 individual emitters is operated at up to 13.3 W power. The design and manufacture of the thruster are described, including its porous glass emitter chip and metallized ceramic extractor chip. A precision mass balance mounted inside a bell jar is used to directly measure the thrust, specific impulse, and efficiency in negative polarity, from $$42\pm 0.5\ \upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>42</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.5</mml:mn> <mml:mspace/> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> N, $$1050\pm 26$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>1050</mml:mn> <mml:mo>±</mml:mo> <mml:mn>26</mml:mn> </mml:mrow> </mml:math> s, and $$57\pm 1.9$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>57</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.9</mml:mn> </mml:mrow> </mml:math> % at $$-1000$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1000</mml:mn> </mml:mrow> </mml:math> V and 0.38 W to $$174\pm 0.5\ \upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>174</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.5</mml:mn> <mml:mspace/> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> N, $$420\pm 2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>420</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> s, and $$21\pm 0.3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>21</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> </mml:math> % at $$-1300$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1300</mml:mn> </mml:mrow> </mml:math> V and 1.7 W. Additional negative polarity experiments in a 2 meter vacuum facility demonstrate powers from order 1 $$\upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> W to over 10 W, spanning 7 orders of magnitude. Power and performance measurements were not repeated for positive mode operation, as this was found to induce arcing between the emitter and extractor electrodes at 1400 V and above. The drop in efficiency from $$-1000$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1000</mml:mn> </mml:mrow> </mml:math> V to $$-1300$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1300</mml:mn> </mml:mrow> </mml:math> V operation in the bell jar is discussed within the context of facility effects, and secondary charged particle flux to the thruster is identified as a likely contributor. Finally, the performance of the thruster is considered relative to scaling electrospray systems to higher power robustly.