Asymmetric discharge patterns in the MPD thruster

Hoskins, W. Andrew; Kelly, A. J.; Jahn, R. G.

doi:10.2514/6.1990-2666

Cited by 10 publications

(12 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Results from previous studies [16][17][18] have shown that light intensity qualitatively agrees well with regions of higher current density. Assuming this to be the case here aw well, we draw conclusions about trends in current sheet location based on the brightness of light in photographs.…”

Section: Photographic Evidencesupporting

confidence: 64%

Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

Hallock¹,

Polzin

Kimberlin

et al. 2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

View full text Add to dashboard Cite

Operational characteristics of two separate inductive thrusters with conical theta pinch coils of different cone angles are explored through thrust stand measurements and timeintegrated, unfiltered photography. Trends in impulse bit measurements indicate that, in the present experimental configuration, the thruster with the inductive coil possessing a smaller cone angle produced larger values of thrust, in apparent contradiction to results of a previous thruster acceleration model. Areas of greater light intensity in photographs of thruster operation are assumed to qualitatively represent locations of increased current density. Light intensity is generally greater in images of the thruster with the smaller cone angle when compared to those of the thruster with the larger half cone angle for the same operating conditions. The intensity generally decreases in both thrusters for decreasing mass flow rate and capacitor voltage. The location of brightest light intensity shifts upstream for decreasing mass flow rate of propellant and downstream for decreasing applied voltage. Recognizing that there typically exists an optimum ratio of applied electric field to gas pressure with respect to breakdown efficiency, this result may indicate that the optimum ratio was not achieved uniformly over the coil face, leading to non-uniform and incomplete current sheet formation in violation of the model assumption of immediate formation where all the injected propellant is contained in a magnetically-impermeable current sheet.

show abstract

Section: Photographic Evidencesupporting

confidence: 64%

Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

Hallock¹,

Polzin

Kimberlin

et al. 2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

View full text Add to dashboard Cite

show abstract

“…Magnetic probe signals are accurate to within 2%. 26 Details of the construction and calibration of the probe can be found in Ref. 26.…”

Section: Anode Fall Scaling Parametermentioning

confidence: 99%

“…In order to calculate both of these quantities, the electron temperature, number density, and the local magnetic field must be measured. A magnetic field probe (B probe), originally constructed to investigate asymmetries in the thruster discharge, 26 was used for this experiment. The core of the probe consists of a coil with 30 turns of no.…”

Section: Anode Fall Scaling Parametermentioning

confidence: 99%

Anode power deposition in magnetoplasmadynamic thrusters

Gallimore

Kelly

Jahn

1993

Journal of Propulsion and Power

View full text Add to dashboard Cite

Results of anode heat-flux and anode fall measurements from a multimegawatt self-field quasisteady magnetoplasmadynamic (MPD) thruster are presented. Measurements were obtained with argon and helium propellants for a variety of currents and mass flow rates. Anode heat flux was directly measured with thermocouples attached to the inner surface of a hollowed section. Anode falls were determined both from floating probes and through heat flux measurements. Comparison of data acquired through either method shows excellent agreement. Anode falls varied between 4-50 V with anode power fractions reaching 70% with helium at 150 kW, and 50% with argon at 1.9 MW. The anode fall was found to correlate well with electron Hall parameters calculated from triple Langmuir and magnetic probe data collected near the anode. Two possible explanations for this result are proposed: 1) the establishment of large electric fields at the anode to maintain current conduction across the strong magnetic fields; and 2) anomalous resistivity resulting from the onset of microturbulence in the plasma. To investigate the latter hypothesis, electric field, magnetic field, and current density profiles measured in the vicinity of the anode were incorporated into Ohm's law to estimate the electrical conductivity. Results of this analysis show a substantial deviation of the measured conductivity from that calculated with classical formulas. These results imply that anomalous effects are present in the plasma near the anode. Nomenclature B = magnetic field strength, T E -electric field, V/m e = elementary charge, 1.6 x 10~1 9 C J = thruster current, kA J a = total anode current, A j = current density, A/cm 2 j a = anode current density, A/cm 2 k = Boltzmann's constant, 1.38 x 10~2 3 J/K m = propellant mass flow rate, g/s m e = propellant mass flow rate, g/s n e = electron number density, m~3 P t = total anode power, W p e = electron pressure, Pa q a = anode heat flux, W/cm 2 q c = anode heat flux from convection, W/cm 2 q r = anode heat flux from radiation, W/cm 2 T = thrust, N T e = electron temperature, K T f = ion temperature, K V = terminal voltage, V V a = anode fall, V v = plasma streaming velocity, m/s £ 0 = permittivity of free space, 8.85 x 10~1 2 F/m j] a = anode power fraction rj ± = transverse electrical resistivity, Ohm-m A = plasma parameter \ e = Debye length, m v e = electron collision frequency, s -1°~s h = Spitzer-Harm conductivity, mho/m OQ = inferred electrical conductivity, mho/m 4> = anode material work function, 4.62 V

show abstract

“…It has been shown in previous work [77] with co-axial, quasi-steady pulsed plasma thrusters that the luminous patterns in the arc discharge are a good indication of magnetic field and current conduction symmetry. In this section, the technique for visually capturing the development of the discharge including the ignition phase will be presented.…”

Section: Imaging the Discharge Initiation And Propagationmentioning

confidence: 94%

Gas-Fed Pulsed Plasma Thrusters: Fundamentals, Characteristics and Scaling Laws

Choueiri¹

2000

View full text Add to dashboard Cite

Asymmetric discharge patterns in the MPD thruster

Cited by 10 publications

References 1 publication

Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

Anode power deposition in magnetoplasmadynamic thrusters

Gas-Fed Pulsed Plasma Thrusters: Fundamentals, Characteristics and Scaling Laws

Contact Info

Product

Resources

About