Nascap-2K: Simulating the Interaction of Spacecraft with the

Plasma Environment

David CookeAdrian Wheelock

Air Force Research Laboratory, Hanscom AFB, Boston, MA

Myron J. Mandell, Victoria Davis,Jeffrey Hilton, Barbara Gardner

Science Applications International CorporationSan Diego, CA

Code: NASCAP/LEO (1980-1991)Applications: High Voltage Current Collection in Dense PlasmaSponsor: NASA

Code: NASCAP/LEO (1980-1991)Applications: High Voltage Current Collection in Dense PlasmaSponsor: NASA

Code: NASCAP/GEO (1976-1984)Applications: GEO S/C ChargingSponsors: NASA, Air Force

Code: NASCAP/GEO (1976-1984)Applications: GEO S/C ChargingSponsors: NASA, Air Force

Nascap-2K Replaces Earlier Spacecraft-Plasma Codes

Code: POLAR (1978-1991)Applications: Auroral Charging, WakesSponsor: Air Force

Code: POLAR (1978-1991)Applications: Auroral Charging, WakesSponsor: Air Force

Code: DynaPAC (1991-1999)Applications: Complex dense plasma phenomenaSponsor: AFRL

Code: DynaPAC (1991-1999)Applications: Complex dense plasma phenomenaSponsor: AFRL

Surfaces Accumulate Chargeto Achieve Current Balance

Physically, spacecraft surfaces arebombarded with charged particlesfrom the ambient plasma. Secondaryelectrons are emitted from spacecraftsurfaces.

Electrically, the net plasma currents chargespacecraft surface capacitances. Thecapacitances of the surfaces to thespacecraft chassis are much larger thanthose to the plasma.

conductionphotoibackscatenet jjjjjjj sec

Why modeling spacecraft charging is difficultCurrents depend on potentials & fieldsTimescales vary by orders of magnitudeGeometrical details are importantDifferential charging barriers limit secondary electrons

Why modeling spacecraft charging is difficultCurrents depend on potentials & fieldsTimescales vary by orders of magnitudeGeometrical details are importantDifferential charging barriers limit secondary electrons

NASCAP2K Integrated Framework:Surface Potentials & Fields

Surfaces in 3-DObject Toolkit displaySurface Picking

ResultsSurface #Normal vectorPotentialEfieldCurrentConductor #

Surface Potentials after charging in NASA “Worst-Case” Environment

Tenuous Plasma Geosynchronous surface charging Solar Wind surface charging Potentials and Fields Particle Tracking

Dense Plasma External Potentials

•Analytic Space Charge•Hybrid Space Charge

Current Collection EP Plumes Auroral Charging PIC Maxwell’s Eq. (Darwin approx)

Nascap-2k Capabilities

Object Toolkit Examples

DMSP

SSULI

Users interactively size and edit standard shapes

Construct custom primitivesImport from common CAD programs

Examples of recent NASCAP2K Models

STEREO: Twin spacecraft to lead/lag Earth in solar orbit

Concern: Engineer for positive charging to aid electron detection instruments

MESSENGER: Space science mission to Mercury

Concern: Engineer for negative charging to aid ion detection instruments

Success Story: C/NOFSComm/Nav Outage Forecasting System

Ram-facing experiments and E-field probes require equipotential surfaces on ram facets.

SAIC and Spectrum-Astro used Nascap2K to show that an innovative surface grounding scheme could reduce ITO (conductive) coating thickness on solar cells saving ~1 M$ in custom processing.

Next Success Story: DSXDeployed Space Experiment

NASCAP2K models of DSX antenna-plasma interaction 3D electro-dynamic PIC simulation Dynamic sheath structure Ampere’s law magnetic perturbations Sheath dissipation or radiation? In-house parallel processing effort

Trajectory simulations to help place low energy ion and electron sensors

Points represent electron macroparticles.

Ion sheath conduction currents5 eV ion access with 5 kV sheath