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

Far Field Plume Distribution and Divergence for NEXT: DART Mission

In support of the Double Asteroid Redirection Test (DART) mission, laboratory measurements were made on the NEXT ion engine, which will be used for the spacecraft's in-space propulsion [1]. This study revisits a small range of mission-specific 2.7A throttle levels to understand the effect of in-flight flow rate variability, investigate intermediate throttle conditions, and improve measurement methodology. This paper specifically examines the far-field plume divergence and backflow ion flux distribution of the NEXT, while a companion paper examines the charge state distributions

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

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

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

Tuberculosis in children in India-II: Chemotherapy for tuberculosis

Tubercle bacilli readily become resistant to the common drugs, and resistant bacilli are more likely to proliferate if they are present in the patient at the start of treatment. So always use more than one drug. The only possible exception is prophylaxis for an asymptomatic case with a normal X-ray. CAUTION! (1) Never give intermittent (twice or thrice weekly) treatment unless every dose can be supervised by a health worker. Daily treatment is usually mandatory. (2) When you give more than one drug, give them both at the same time, so that high blood levels coincide; do not give one drug daily and the other drug less often. THE DOSES of the commonly used drugs for daily and intermittent treatment in children and adults are: lsoniazid (H) 5 mg/kg/24 hours if he is moderately ill and 10 mg/kg/24 hours if he is severely ill. The dose for a twice weekly course is 15 mg/kg. CAUTION! Opinions on the dose of isoniazid vary. Some consider 10 mg/kg/24 hours too much for an Indian child and always give 5 mg. Rifampicin (R) 10 mg/kg/24 hours, or 10 mg/kg twice weekly. Pyrazinamide (Z) 35 mg/kg/24 hours, 75 mg/kg twice weekly or 50 mg/kg thrice weekly, is an important drug for short course treatment, so try to include it whenever it is mentioned in the regimes below. Streptomycin (S) 10-20 mg/kg/24 hours, or 40 mg/kg twice weekly, to a total of not more than 0.75 g. Streptomycin is painful, so avoid it if you can. If you give it, inject in different places each day, because repeated injections into the same site are painful. Ethambutol (E) 25 mg/kg/24 hours for 2 months, then 15 mg/kg/24 hours. Avoid ethambutol in younger children (under 12); they are unable to complain of the early symptoms of retrobulbar neuritis (blindness). Thiacetazone (T) 4 mg/kg/24 hours to a maximum Of 150 mg; unsuitable for intermittent treatment

Tuberculosis in children in India-I

Tuberculosis is different in children. It involves many organs, instead of being the predominantly respiratory disease that it usually is in adults. Fortunately, it readily responds to treatment–if you diagnose it early enough and treat it for long enough! This is the problem. Unfortunately, tuberculosis causes such non-specific symptoms and signs, and you are so seldom able to isolate bacilli, that you may never be sure of the diagnosis. Even experts sometimes disagree. In India particularly, it is a disease of the poorest of the poor, but even in them it causes only a small proportion of their burden of morbidity. The great problem is to reach those infected. Of every thousand Indians, seven children and about twenty adults have active tuberculosis, and five of these adults are sputum positive. Only about half the 9 million in the community at any one time are ever diagnosed, and of these only about 13% complete their treatment, so there is a huge pool of infectious cases, half a million of whom die each year. Fortunately, the incidence of tuberculosis among children reporting to hospital is slowly decreasing, probably largely due to improved coverage with BCG