Modeling the plasma plume of a hollow cathode

In this study, a numerical model is developed to simulate the xenon plasma plume from a thermionic hollow cathode employing an orifice plate used for propellant ionization and beam neutralization in an electrostatic space propulsion system. The model uses a detailed fluid model to describe the electrons and a particle-based kinetic approach is used to model the heavy xenon ions and atoms. A number of key assumptions in terms of physical modeling and boundary conditions of the simulations are assessed through direct comparisons with experimental measurements. For two of the three cathode operating conditions considered, good agreement with the measured data is obtained. The third condition appears to lie in a different physical regime where elevated electron and ion temperatures and decreased transport coefficients are required in the simulation to provide agreement between the model and the measured data. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71113/2/JAPIAU-95-7-3285-1.pd

The T6 Hollow Cathode: Measurements and Modeling

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76762/1/AIAA-2003-4171-765.pd

Grid erosion analysis of the T5 ion thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76419/1/AIAA-2001-3781-901.pd

Plume measurement and modeling results for a hollow cathode micro-thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77184/1/AIAA-2001-3795-876.pd

Annular Engine Development Status

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106479/1/AIAA2013-3892.pd

Development Status of High-Thrust Density Electrostatic Engines

Ion thruster technology offers the highest performance and efficiency of any mature electric propulsion thruster. It has by far the highest demonstrated total impulse of any technology option, demonstrated at input power levels appropriate for primary propulsion. It has also been successfully implemented for primary propulsion in both geocentric and heliocentric environments, with excellent ground/in-space correlation of both its performance and life. Based on these attributes there is compelling reasoning to continue the development of this technology: it is a leading candidate for high power applications; and it provides risk reduction for as-yet unproven alternatives. As such it is important that the operational limitations of ion thruster technology be critically examined and in particular for its application to primary propulsion its capabilities relative to thrust the density and thrust-to-power ratio be understood. This publication briefly addresses some of the considerations relative to achieving high thrust density and maximizing thrust-to-power ratio with ion thruster technology, and discusses the status of development work in this area being executed under a collaborative effort among NASA Glenn Research Center, the Aerospace Corporation, and the University of Michigan

High Thrust-to-Power Annular Engine Technology

Gridded ion engines have the highest efficiency and total impulse of any mature electric propulsion technology, and have been successfully implemented for primary propulsion in both geocentric and heliocentric environments with excellent ground/in-space correlation of performance. However, they have not been optimized to maximize thrust-to-power, an important parameter for Earth orbit transfer applications. This publication discusses technology development work intended to maximize this parameter. These activities include investigating the capabilities of a non-conventional design approach, the annular engine, which has the potential of exceeding the thrust-to-power of other EP technologies. This publication discusses the status of this work, including the fabrication and initial tests of a large-area annular engine. This work is being conducted in collaboration among NASA Glenn Research Center, The Aerospace Corporation, and the University of Michigan

Thrust Stand Characterization of the NASA Evolutionary Xenon Thruster (NEXT)

Direct thrust measurements have been made on the NASA Evolutionary Xenon Thruster (NEXT) ion engine using a standard pendulum style thrust stand constructed specifically for this application. Values have been obtained for the full 40-level throttle table, as well as for a few off-nominal operating conditions. Measurements differ from the nominal NASA throttle table 10 (TT10) values by 3.1 percent at most, while at 30 throttle levels (TLs) the difference is less than 2.0 percent. When measurements are compared to TT10 values that have been corrected using ion beam current density and charge state data obtained at The Aerospace Corporation, they differ by 1.2 percent at most, and by 1.0 percent or less at 37 TLs. Thrust correction factors calculated from direct thrust measurements and from The Aerospace Corporation s plume data agree to within measurement error for all but one TL. Thrust due to cold flow and "discharge only" operation has been measured, and analytical expressions are presented which accurately predict thrust based on thermal thrust generation mechanisms

Conflict of Laws in the Era of Globalization

本稿の目的は, グローバル化に対応した抵触法の在り方を巡る近時の議論動向を採り上げ, その意義と問題点を探ることにある。社会のグローバル化 は, 抵触法の前提である, 法の抵触が国家法の間でしか生じないという国家中心的な考え方, 及び, 公法・私法の区別に基づき私法のみを準拠法選択の対象とするという考え方に対し大きな動揺を与えている。グローバル化による私人の影響力の上昇と国家の影響力の後退が主として齎すこうした新たな状況に対応するため, 近時では, 従来の抵触法の基本的枠組に替えて, 法の抵触の調整に関して新たなアプローチを主張する見解が幾つか登場している。本稿では, これらの新たなアプローチの特徴として, グローバル・ガヴァナンスのための抵触法, 普遍主義的アプローチ, 機能的アプローチ, 手続基底的アプローチという4点を幾つか指摘した上で, その意義と今後の課題について述べる。This paper discusses how the conflict of laws is trying to respond to the challenges brought by the globalization. The globalization of economy and society has brought challenges to the assumptions that the traditional conflict of laws is based on: 1) the state-centered assumption that only the state can create law, and that as a result, the conflict of laws can happen only horizontally, namely among state laws; 2) the public/private distinction. How effectively can the conflict of laws respond to these challenges brought by the globalization? Is the conflict of laws still workable under these situations? This paper describes and analyzes the new approaches of the conflict of laws.特集　「グローバル化と公法・私法の再編

Spatially-Resolved Beam Current and Charge-State Distributions for the NEXT Ion Engine

Plume characterization tests with the 36-cm NEXT ion engine are being performed at The Aerospace Corporation using engineering-model and prototype-model thrusters. We have examined the beam current density and xenon charge-state distribution as functions of position on the accel grid. To measure the current density ratio j++/j+, a collimated Eprobe was rotated through the plume with the probe oriented normal to the accel electrode surface at a distance of 82 cm. The beam current density jb versus radial position was measured with a miniature planar probe at 3 cm from the accel. Combining the j++/j+ and jb data yielded the ratio of total Xe+2 current to total Xe+1 current (J++/J+) at forty operating points in the standard throttle table. The production of Xe+2 and Xe+3 was measured as a function of propellant utilization to support performance and lifetime predictions for an extended throttle table. The angular dependence of jb was measured at intermediate and far-field distances to assist with plume modeling and to evaluate the thrust loss due to beam divergence. Thrust correction factors were derived from the total doubles-to-singles current ratio and from the far-field divergence dat