Discharge Hollow Cathode and Extraction Grid Analysis for the MiXI Ion Thruster

Wirz, Richard E.; Sullivan, Regina; Przybylowski, JoHanna; Silva, Mike

doi:10.2514/6.2006-4498

Cited by 7 publications

(8 citation statements)

References 9 publications

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“…21 In support of that effort, the DC-ION model was scaled down to simulate the 3 cm MiXI. 22,23 Results from the model confirmed inferences from experimental data that the main challenge to discharge utilization efficiency of the small 3 cm ring-cusp discharge is prodigious loss of primary electrons to the chamber walls. The high rate of primary electron loss for this miniature discharge design was due to the need for relatively low magnetic field strengths at the boundaries that allow plasma electrons to be lost at a rate sufficient to maintain discharge stability.…”

Section: Introductionsupporting

confidence: 84%

Near-Surface Cusp Confinement for Weakly Ionized Plasma

Wirz¹,

Araki²,

Dankongkakul³

2012

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

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For this study, we use a combined experimental and computational approach to investigate the near-surface dynamics and structure of plasma confined by a permanent magnet cusp. Improved understanding in this region allows electric propulsion designers to take advantage of cusp confinement for micro-scale discharges (≤ 1 cm), enabling high performance microthrusters that are attractive for both microsatellite and formation flying missions. An electron gun experiment designed specifically for this effort provides detailed data on the plasma for a single permanent magnet cusp for electron-only conditions and multispecies (electron, neutral, and ion) weakly ionized conditions. For these experimental conditions, a multispecies particle-in-cell model is developed that uses an adaptive mesh and analytical solutions for permanent magnets to provide high resolution for particle motion and interactions in the cusp region. Results from the experiment and model agree well and are consistent with existing theory for the "leak radius" at the cusp. Nomenclature a = coefficients for 2D quadratic equation A = amplitude of oscillation dS = differential area along a surface, m 2 E = electric field, V/m E = particle energy, eV E 0 = atomic unit of energy (= 27.21eV) m = particle mass, kg q = charge, C r = radial position, m r l = leak radius, mm R = error of the 2D quadratic equation, V t = time, s U = random number between 0 to 1 v = particle velocity, m/s w l = leak width, mm z = axial position, m Subscripts i = initial k = cell number n = number of neighboring cells f = final Symbols β = magnetic pressure Δt = time step, s ρ h , ρ e , ρ i = hybrid, electron, and ion gyroradii ρ p , ρ s = primary and secondary electron gyroradii φ = electric potential, V χ = deflection angle, rad

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Section: Introductionsupporting

confidence: 84%

Near-Surface Cusp Confinement for Weakly Ionized Plasma

Wirz¹,

Araki²,

Dankongkakul³

2012

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

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“…As discussed in Section 2, a key component for a lunar mission CubeSat is an SEP system which has relatively high power demands (usually in the kW range) in comparison to miniaturized chemical systems 10 . However, recent developments in thruster miniaturization techniques have led to novel thrusters, such as JPL/UCLA's MiXI thruster, on the scale of centimeters in diameter that can operate below 100W while maintaining the same high specific impulse and precision as larger ion thrusters 16,17,18,19 . Such a thruster is necessary for an autonomous CubeSat to successfully navigate to the lunar surface utilizing self-carried propulsion methods.…”

Section: Power Subsystemmentioning

confidence: 99%

CubeSat Lunar Mission Using a Miniature Ion Thruster

Conversano¹,

Wirz²

2011

47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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The feasibility of CubeSats utilizing the Miniature Xenon Ion (MiXI) thruster for lunar missions is the focus of this investigation. The successful heritage, simplicity, and low cost of CubeSats make them attractive candidates for scientific missions to the Moon. This investigation presents the first-order design process for developing a lunar mission CubeSat. The results from this process are then applied to a 3U CubeSat equipped with a MiXI thruster and specifically designed to reach the lunar surface from a low Earth orbit. The small, 3cm diameter MiXI thruster utilized is capable of producing 0.1-1.553mN of thrust with a specific impulse of over 3000s and is projected to be capable of generating over 7000m/s of ∆V for a CubeSat mission. With all margins and contingencies considered, the total power required for the CubeSat using a 40W ion thruster is approximately 92W during daylight operations. With an assumed solar incidence angle of 45°, this power can be generated from a Spectrolab UTJ solar array of 0.35m 2. Thermal calculations show an average spacecraft surface temperature of approximately 59°C during daylight operations and 0°C during eclipse, which are within the operational and survivable temperature ranges of the spacecraft subsystems. A low-thrust trajectory model is utilized to calculate and plot Earth-Moon trajectories.

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“…In addition, the primary electron density and its role in ionization is substantially higher for reduced the discharge size. 17 Previous research efforts with primary electrons have experimentally measured the local cusp density for a 10 cm discharge 18 and computationally improved confinement using a particle tracker. 19 However, their findings are focused on large scale general confinement and do not address the intricate field structures inherent in microdischarges.…”

Section: Introductionmentioning

confidence: 99%

Influence of Upstream Field Structure on Primary Electron Loss for a Permanent Magnet Cusp

Dankongkakul

Araki

Wirz

2013

49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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An improved understanding of the electron loss behavior for permanent magnet cusps is needed to enable the design of efficient micro-scale plasma devices. Such devices can be used for a variety of applications, including high performance micro-thrusters that are attractive for primary propulsion for microsatellites, secondary propulsion for larger spacecraft, and formation flying. Conventional plasma loss theory for magnetic cusps generally relates the loss area to an analytical expression related to the magnetic field strength at the loss surface. In contrast, this study examines the importance of the upstream magnetic field structure on the loss behavior of high energy electrons. For the experimental effort, an electron gun is used to inject monoenergetic electrons towards a cusp confined discharge, while precision electron loss measurements are made at the face of a single permanent magnet point cusp. Measurements are taken at facility base pressure and with xenon background gas. A Monte-Carlo model is used to provide detailed examination of the electron confinement and loss behavior. Comparison of the experimental and computational results shows that the primary electron loss behavior is strongly influenced by the upstream magnetic field structure and is not simply dictated by the field strength very near the cusp collection surface. NomenclatureB B Block B Cylind H m L m m M q r = = = = = = = = = magnetic field magnetic field induced by a block magnet magnetic field induced by a cylindrical magnet height of a block magnet length of a magnet mass of an electron magnetization charge location of interestradius of curvature Larmor radius location of the magnet center radius of a magnet curvature drift velocity grad-B drift velocity parallel velocity perpendicular velocity width of a block magnet gradient of the magnetic field

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Discharge Hollow Cathode and Extraction Grid Analysis for the MiXI Ion Thruster

Cited by 7 publications

References 9 publications

Near-Surface Cusp Confinement for Weakly Ionized Plasma

Near-Surface Cusp Confinement for Weakly Ionized Plasma

CubeSat Lunar Mission Using a Miniature Ion Thruster

Influence of Upstream Field Structure on Primary Electron Loss for a Permanent Magnet Cusp

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