2006-2007 - Kennedy Space Center Technology Transfer Office

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Determining Trajectory of Triboelectrically Charged Particles, UsingDiscrete Element ModelingThe Kennedy Space Center (KSC) Electrostatics and Surface Physics Laboratory isContamination participating in an Innovative Partnership Program (IPP) project with an industryControlpartner to modify a commercial off-the-shelf simulation software product to treat theelectrodynamics of particulate systems. The industry partner, DEM Solutions, Inc.,has developed EDEM, a program that can calculate the dynamics of particles. Discreteelement modeling (DEM) is a numerical technique that can track the dynamics of particlesystems. This technique, which was introduced in 1979 for analysis of rock mechanics, wasrecently refined to include the contact force interaction of particles with arbitrary surfaces andmoving machinery. In our work, we endeavor to incorporate electrostatic forces into the DEMcalculations to enhance the fidelity of the software and its applicability to (1) particle processes,such as electrophotography, that are greatly affected by electrostatic forces, (2) grain and dusttransport, and (3) the study of lunar and Martian regoliths [1].After contact force is calculated, additional body forces acting on each particle are calculated. Inthis step, any desired force can be added to the simulation. After the forces on each particle arecalculated, the linear and angular accelerations of each particle are updated according to Newton’ssecond law. Then the positions and orientations of each particle are updated with an explicit timemarchingalgorithm.The introduction of electrostatic forces into the current EDEM configuration requires theaddition of a long-range model that works in conjunction with the existing dynamic calculations.This long-range force model is based on a version of Coulomb’s law [2] that takes into account theelectrostatic screening of adjacent particles. The electrostatic force, F, is given byF = – dU edrq 1q= 2 κ + 14pε 0r r 2(1)where q 1and q 2are the charges of two particles, r is the distance between their centers, ε 0is thepermittivity of free space (8.854 × 10 –12 F/m), U eis the electrostatic potential, and κ is the inverseof the Debye length, λ D, and is based on the local charge concentration.For charge generation, we modify a charge generation equation [3] to model many particles.Q(t) = Nq s(1 – e -at )(2)where N is the number of particles, Q(t) is the total charge on the particles, q sis the saturationcharge, and α is the charge generation constant.We developed a simple inclined-plane apparatus to compare theoretical results with experimentaldata (Figure 1). The inclined plane allowed 500 2.0-mm-diameter glass spheres to roll down overvarious polymer and metal surfaces and into a Faraday cup, where total charge on the spheres wasmeasured. By timing the roll of the spheres down the plane and knowing the total charge, Q(t),we were able to calculate the charge generation constant for the materials under test. The inclinedplanematerials tested were low-density polyethylene (LDPE), polyvinyl chloride (PVC), nylon6/6, polytetrafluoroethylene (PTFE), aluminum, and copper.Spaceport Structures and Materials
Initial results of the EDEM model of the inclined planeshow good comparison to values of Q(t) and α calculatedfrom experimental data. Figure 2 compares the EDEMsimulation output and example Q(t) data.The EDEM modeling tool can be applied to systemsof charged particles that are of interest to NASA, forexample, charged lunar and Martian regoliths. Proposedfuture work includes the addition of dilectrophoreticforce and Van der Waals forces, electrodynamic forcesfrom charged surfaces, and the modeling of nonsphericalparticles.References:[1] C.I. Calle, J.G. Mantovani, E.E. Groop,C.R. Buhler, A.W. Nowicki, M.G. Buehler, andM.D. Hogue, “Electrostatic charging of polymers byparticle impact at Martian atmospheric pressures,”Proceedings ESA-IEJ Joint Meeting, NW University,Laplacian Press, Morgan Hill, California, 2002,pp. 106–117.[2] F.J. Bueche, Introduction to Physics for Scientists andEngineers, 3 rd ed., McGraw-Hill, Inc., 1980, p. 343.[3] W.D. Greason, “Investigation of a test methodologyfor triboelectrification,” Journal of Electrostatics,Vol. 49, Issue 3–4, August 2000, pp. 245–256.Figure 1. EDEM simulation of spheres rolling down theinclined plane.Contacts: Dr. Michael D. Hogue , NASA-KSC, (321) 867-7549; andDr. Carlos I. Calle , NASA-KSC, (321) 867-3274Participating Organization: DEM Solutions, Inc. (Dr. Peter Weitzman and Dr. David R. Curry)Figure 2. Charge-to-mass ratio for 15-degree experiment compared with simulationresults for the six plane materials.KSC Technology Development and Application 2006-2007
Page 5 and 6: ForewordSuccessful technology devel
Page 7 and 8: ContentsSpaceport Structures and Ma
Page 9 and 10: Contents (continued)Process and Hum
Page 11 and 12: IntroductionJohn F. Kennedy Space C
Page 13 and 14: Constellation SystemsSurfaceSystems
Page 15 and 16: Spaceport Structures and MaterialsK
Page 17: 20181614∆ E1210Modified Sensor Be
Page 21 and 22: Contacts: Dr. Carlos I. Calle ,NASA
Page 23 and 24: Close examination of the corrosions
Page 25 and 26: Adhesion at Failure (psi)2500200015
Page 27 and 28: Figure 1. After 500 hours of salt f
Page 29 and 30: Contacts: Dr. Paul E. Hintze , NASA
Page 31 and 32: Figure 2. Repairs to various types
Page 33 and 34: on top of the cuvette contains the
Page 35 and 36: Figure 2. A corrugated NiTi sheet e
Page 37 and 38: The PLTD can be used to (1) calibra
Page 39 and 40: SEM images of neat MWNT fibers: (a)
Page 41 and 42: Contacts: Trent M. Smith
Page 43 and 44: Figure 1. An isometric cutaway view
Page 45 and 46: Figure 2. Quartz sand flowing in th
Page 47 and 48: Figure 2. Top images show how the e
Page 49 and 50: Sand volume fraction contour at t =
Page 51 and 52: Integrated LWRD/RVC engineering bre
Page 53 and 54: Mean relative percentage change in
Page 55 and 56: We compared the model’s predictio
Page 57 and 58: Figure 2. Three-dimensional simulat
Page 59 and 60: Figure 3. Camera calibration model.
Page 61 and 62: The sketch in Figure 2 shows alaunc
Page 63: Figure 2. Signal generator (right)
Page 66 and 67: Hail Size Distribution MappingA 3-D
Page 68 and 69:
Launch Pad 39 Hail Monitor Array Sy
Page 70 and 71:
Autonomous Flight Safety System - P
Page 72 and 73:
The Photogrammetry CubeSpaceport/Ra
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Bird Vision SystemThe Bird Vision s
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Automating Range Surveillance Throu
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Next-Generation Telemetry Workstati
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GPS Metric Tracking UnitAs Global P
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Space-Based RangeSpace-Based Range
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Fluid System TechnologiesKSC Techno
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0.900.850.80Discharge Coefficient,
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Composite seals for performance eva
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140000120000100000Signal80000600004
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Contacts: Dr. Barry J. Meneghelli ,
Page 95 and 96:
60555045Comparative k-value (mW/m-K
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a compatible spacecraft model where
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In an ongoing effort for improvemen
Page 101:
Low-gravity probe prototype test.th
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Countermeasure for Radiation Protec
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Focused Metabolite Profiling for Di
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Process and Human FactorsEngineerin
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DON uses game technology to enable
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Type of mobile crane that impacted
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SALT proof-of-concept communication
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SSLM CAD model.Our design offers th
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Variables that can be integrated by
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Exploration Supply Chain Simulation
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Nanosensors for Evaluating Hazardou
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Sixty-four-Channel Inline Cable Tes
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Wireless Inclinometer Calibration S
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Generating Safety-Critical PLC Code
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Spacecraft Electrostatic Radiation
Page 134 and 135:
Ion Beam Propulsion StudySpacecraft
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RT-MATRIX: Measuring Total Organic
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Appendix AKSC High-Priority Technol
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Risk Assessment ToolMission Data Fe
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Appendix BInnovative Partnership Pr
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system for the Government, using th
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tracking objects after launch, and
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2006-2007 - Kennedy Space Center Technology Transfer Office

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