| Summary: | Vacuum arc thruster performance in a magnetic nozzle configuration is experimentally characterized. Measurements are performed on a miniature coaxial thruster with an anode inner diameter of <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1.8</mn> </mrow> </semantics> </math> </inline-formula> mm. The magnetic field B is produced by a single air coil, 18 mm in diameter. Direct measurement of thrust, mass consumption and arc current are performed. To obtain statistically viable results <inline-formula> <math display="inline"> <semantics> <mrow> <mo>≈</mo> <mn>6000</mn> </mrow> </semantics> </math> </inline-formula> arc pulses are analyzed at each operational point. Cathode mass erosion is measured using laser profilometry. To sustain thruster operation over several measurement cycles, an active cathode feeding system is used. For <inline-formula> <math display="inline"> <semantics> <mrow> <mn>0</mn> <mo><</mo> <mi>B</mi> <mo>≤</mo> <mn>0.2</mn> </mrow> </semantics> </math> </inline-formula> T, performance increase over the non-magnetic case is observed with the best thrust to arc power ratio <inline-formula> <math display="inline"> <semantics> <mrow> <mi>T</mi> <mo>/</mo> <mi>P</mi> <mo>≈</mo> <mn>9</mn> </mrow> </semantics> </math> </inline-formula> <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math> </inline-formula>N/W obtained at <inline-formula> <math display="inline"> <semantics> <mrow> <mi>B</mi> <mo>≈</mo> <mn>0.2</mn> </mrow> </semantics> </math> </inline-formula> T. A parametric model is provided that captures the performance enhancement based on beam collimation and acceleration by the magnetic nozzle. For <inline-formula> <math display="inline"> <semantics> <mrow> <mi>B</mi> <mo>></mo> <mn>0.2</mn> </mrow> </semantics> </math> </inline-formula> T, the arc discharge is shown to be suppressed nullifying any additional gains by the nozzle effect.
|
|---|