A5049854515- Plasma Diagnostics and Applications
- Advanced Thermoelectric Materials and Devices
- Electrohydrodynamics and Fluid Dynamics
- Semiconductor materials and interfaces
- Magnetic Field Sensors Techniques
- Intermetallics and Advanced Alloy Properties
- Thermal properties of materials
- Cryptographic Implementations and Security
- Thermodynamic and Structural Properties of Metals and Alloys
- Particle accelerators and beam dynamics
- Astro and Planetary Science
- Radiation Effects in Electronics
- Spacecraft and Cryogenic Technologies
- Thermal Expansion and Ionic Conductivity
- Surface and Thin Film Phenomena
- Advanced Sensor Technologies Research
- Boron and Carbon Nanomaterials Research
- Heat Transfer and Optimization
- Metal and Thin Film Mechanics
- Chalcogenide Semiconductor Thin Films
- Nuclear Physics and Applications
- Isotope Analysis in Ecology
- Plasma Applications and Diagnostics
- Ammonia Synthesis and Nitrogen Reduction
- Vacuum and Plasma Arcs
Glenn Research Center
2014-2024
University College Dublin
2021
Case Western Reserve University
2013-2019
University of Akron
2012-2015
Arctic Slope Regional (United States)
2009
National Institute of Standards and Technology
1979
This work establishes the level of uncertainty for electrical measurements commonly made on thermoelectric samples. The analysis targets measurement systems based four probe method. Sources both resistivity and Seebeck coefficient were identified evaluated. Included are reasonable estimates magnitude each source, cumulative propagation error. Uncertainty includes cold-finger effect which has been quantified with thermal finite element analysis. effect, is a result parasitic heat transfer...
Free-space measurement techniques can be contactless and are able to accommodate large, flat sheets of dielectric material, making them useful for characterization hightemperature, millimeter-wave, window radome candidate materials. As part the present work, a high-temperature, W-band (75-110 GHz), free-space system was developed used characterize complex properties bulk material samples at temperatures ranging from 25 °C 600 °C. Two test cases, polyvinyl chloride (PVC) CoorsTek 92% alumina,...
The performance of many Hall thrusters has been shown to exhibit sensitivity background pressure in ground-based test facilities, and this property can have an impact on the prediction in-space performance. SPT-140 thruster, similar design SPT-100 which shows such sensitivity, was subjected a series tests characterize effects thruster over discharge power range 0.9–4.5 kW. Thrust pressure, absolute sense, largest at 4.5 kW decreased with until there little-to-no measurable effect 0.9 In...
The performance of a three-channel, 100-kW nested Hall thruster was evaluated on xenon propellant for total powers up to 102 kW. demonstrated stable operation in all seven available channel combinations at discharge voltages from 300 500 V and three different current densities. resulting test matrix contained forty-six unique conditions ranging 5 kW power 16 247 A current. At each operating condition, thrust, specific impulse, efficiency were characterized. All showed similar given voltage...
This work presents the results of over 6500 h wear testing completed during maturation NASA 12.5 kW Hall Effect Rocket with Magnetic Shielding. Erosion thruster front pole covers was found to be primary life-limiting mechanism and exhibits strong dependencies on operating condition material properties. Specifically, average cover erosion rates increased by 76% as discharge voltage decreased from 600 300 V 42%–96% magnetic field 0.75 1.25 times nominal value. The cause both trends is...
An uncertainty analysis of a common configuration electric propulsion thrust stand is presented. The applies to inverted pendulum stands operating in null-coil with in-situ calibration. Several sources bias and precision are discussed, propagated, combined form conservative estimates the relative absolute uncertainties. A case study NASA Glenn Research Center Vacuum Facility 6 For thruster investigated, was estimated be ±6.9 mN over entire span thrust. This represents maximum instrument...
This paper reviews recent iodine electric propulsion research and development activities at the NASA Glenn Research Center (GRC). Activities included (i) investigation of compatibility BaO-CaO-Al2O3 impregnated tungsten hollow cathodes based on a flight heritage design, (ii) handful materials common to systems, spacecraft, ground test facilities, (iii) reliable feed system technologies, (iv) implementation facility improvements in an attempt mitigate associated negative impacts, culminated...
Uncertainty in erosion rates as measured by different methods is discussed and quantified. The work focuses on case studies from components the Hall Effect Rocket with Magnetic Shielding (HERMeS) thruster, but can be extended for many electric propulsion applications. primary method used evaluating non-contact profilometry of masked exposed components. Accurate quantification critical to determining lifetime therefore mission planning purposes.
In this paper, a wireless capacitive pressure sensor developed for the health monitoring of aircraft engines has been demonstrated. The sensing system is composed Clapp-type oscillator that operates at 131 MHz. Clapp fabricated on an alumina substrate and consists Cree SiC MESFET, thin film inductor, Complex chip capacitors Sporian Microsystem sensor. resonant tank circuit within made up spiral which used to magnetically couple signal coil antenna placed over 1 meter away. 75% power bias...
A diagnostic has been designed and fabricated to verify the thrust vector requirement for Advanced Electric Propulsion System (AEPS) Hall Effect Rocket with Magnetic Shielding (HERMeS) thruster. This will be used that propulsion system offset from mounting surface normal does not exceed 1.5 degrees over entire throttling range course of 23,000 hours thruster testing. The also violate thruster's required voltage standoff capability in presence carbon backsputter by being minimally intrusive...
This paper describes recent progress at the NASA Glenn Research Center (GRC) in development and demonstration of an integrated high-propellant throughput small spacecraft electric propulsion (HT-SSEP) system based on a Hall-effect thruster. A center-mounted cathode innovative magnetic circuit topology were implemented design thruster to achieve throughput, high performance, efficient packaging. To minimize technical risk, HT-SSEP approach sought limit features materials those with clear...
This work presents a summary of the detailed characterization test 12.5 kW Advanced Electric Propulsion System (AEPS) Engineering Test Unit 2 (ETU-2) thruster produced by Aerojet Rocketdyne. campaign had two major goals: to assess risk design compliance with requirements and provide comparison previously-tested NASA Hall Effect Rocket Magnet Shielding (HERMeS) Technology Demonstration Units (TDUs) from which AEPS ETU was derived. Assessments ETU-2 performance stability were conducted for...
A Hall Effect Thruster fueled by xenon was duration tested for 7,198 hours at NASA’s Glenn Research Center. The thruster generated 1 million Newton-seconds of total impulse before the test terminated voluntarily. Thrust, flow rate, and many other parameters were tracked continuously. Over 98.5% conducted a single operating point, where discharge power 600 W, mean thrust 39 mN specific 1500 s. shape channel measured via laser. changed considerably over course test, due to ion sputtering....
Abstract A mayenite‐based electride is being considered for field emitter applications where it will be critical to have a good understanding of processing repeatability and thermal properties. This paper focuses on the details mayenite compounds in strongly reducing graphite environment form an solid‐solution phase as Ca 12 Al 14 O 32 (C 2 ,O ) 1‐x (e x . The work reports, addition details, several was found coefficient expansion (CTE) 7e‐6 K −1 , diffusivity between 0.0063 0.0102 cm /s,...
Skutterudite crystals are of interest for their thermoelectric properties and in particular the flexibility structure offers tuning such properties. One strategy to enhance capabilities these structures is dope "cage" site disrupt phonon modes. Observation changes on atomic scale challenging, however, understanding atomic-scale crucial its macroscopic Here, a series polycrystalline Co2Ni2Sb8Sn4 skutterudites doped with Ce, Dy, Yb were synthesized. Using scanning transmission electron...