Nascap-2k Spacecraft Charging Code Overview

Abstract

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden to Department SPONSORINGMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)AFRLNSBXT SPONSORMONITOR'S REPORT NUMBER(S) DISTRIBUTIONIAVAILABILITY STATEMENTApproved for Public Relase; distribution unlimited. SUPPLEMENTARY NOTES - ABSTRACTNascap-2k is a modem spacecraft charging code, replacing the older codes NASCAP/GEO, NASCAP/LEO, POLAR, and DynaPAC. The code builds on the physical principles, mathematical algorithms, and user experience developed over three decades of spacecraft charging research. Capabilities include surface charging in geosynchronous and interplanetary orbits, sheath and wake structure and current collection in low-Earth orbits, and auroral charging. External potential structure and particle trajectories are computed using a finite element method on a nested grid structure and may be visualized within the Nascap-2k interface. Space charge can be treated either analytically, self-consistently with particle trajectories, or by importing plume densities from an external code such as EPIC (Electric Propulsion Interactions Code). Particle-in-cell capabilities are available to study dynamic plasma effects. Auxiliary programs to Nascap-2k include Object Toolkit (for developing spacecraft surface models) and GridTool (for constructing nested grid structures around spacecraft models). The capabilities of the code are illustrated by way of three examples: charging ofa geostationary satellite, self-consistent potentials for a negative probe in a LEO spacecraft wake, and potentials associated with thruster plumes. SUBJECT TERMS Spacecraft chargingPlasma simulation, Nascap-2k AbstractNascap-2k is a modem spacecraft charging code, replacing the older codes NASCAP/GEO, NASCAP/LEO, POLAR, and DynaPAC. The code builds on the physical principles, mathematical algorithms, and user experience developed over three decades of spacecraft charging research.Capabilities include surface charging in geosynchronous and interplanetary orbits, sheath and wake structure and current collection in low-Earth orbits, and auroral charging. External potential structure and particle trajectories are computed using a finite element method on a nested grid structure and may be visualized within the Nascap-2k interface. Space charge can be treated either analytically, self-consistently with particle trajectories, or by importing plume densities from an external code such as EPIC (Electric Propulsion Interactions Code). Particle-in-cell (PIC) capabilities are available to study dynamic plasma effects.Auxiliary programs to Nascap-2k include Object Toolkit (for developing spacecr...

Comparison of Vlasov solvers for spacecraft charging simulation

“…Hence, the time variable appears as a parameter in the stationary Vlasov-Laplace system, and the evolution of the charging phenomena is governed by the non stationary boundary conditions at the spacecraft surface. Such approximated models are used in several codes [8,23,26]. …”

“…Hence, the issue of boundary conditions for the potential is converted into a definition of virtual charges to be distributed on the spacecraft. This is done either by the so-called capacitance matrix method [7,17,26] or by defining an equivalent circuit [17,22,23].…”

“…In turn, these potential differences induce the formation of electric arcing that can produce irreversible failures on the embarked devices, the solar arrays being a particularly sensible region. The problem has motivated the design of specific numerical codes in aerospace engineering: NASCAP and its evolution NASCAP-2K [22,23], SPARCS [8], PicUp3D and SPIS [17,27], ESCAPE [24], SILECS [25,26]... The specific modelling of the discharge phenomena and the electric arc formation is addressed e.g.…”

“…It turns out that PIC methods have several advantages that make them well adapted for simulating spacecraft charging, and they are indeed widely used in industrial codes [8,17,22,23,[25][26][27]. This is particularly relevant when considering geostationary orbits since the corresponding models do not need an accurate description of the particle distribution function.…”

Effect of Solar Illumination on Esd for Structure Used in Spacecraft

“…NASCAP-2K computes the external potential structure and 3-D particle trajectories using Finite Element Method [11]. MUSCAT calculates the worst case charging potential by carrying out parametric runs of various environmental cases to determine that the satellite failure is due to ESD [12].…”