OVERVIEW

The Electromagnetic Effects & Spacecraft Charging Working Group develops spacecraft simulation codes and engineering design guidelines to enable spacecraft designers to mitigate plasma effects.

What is Plasma?

Plasma, composed of equal numbers of positively and negatively charged particles, is a partially ionized gas entrained in the Earth's upper atmosphere. Properties of the plasma are described by specifying particle density and particle energy. Spacecraft can develop an electrical potential while the positively charged ions and negative electrons can cause significant physical effects.

Plasma Source The Sun ejects charged particles and energetic photons into space. These charged particles and photons create an electrically active plasma around the Earth. The collective behavior of plasma generates an electric field that, in turn, affects the charged particle motion. Source of plasma produced within the space vehicle is the ionized gas from the thrustering, plume, venting and man-made hardware design such as plasma contactor.

Plasma Effects on Spacecraft Electrical Systems

As a spacecraft travels through this ionized portion of the atmosphere, it may be subjected to an unequal flux of ions and electrons and may develop an induced charge. Plasma flux to the spacecraft surface can charge the surface and disrupt the operation of electrically biased instruments. This is why the choice of spacecraft ground is an important consideration in determining where the spacecraft will float electrically relative to the surrounding plasma. The graphic above depicts an electrical interaction between a spacecraft and the surrounding plasma.

Plasma Effects on Spacecraft

The plasma environment around the space vehicle will be altered by the presence, operation, and motion of the vehicle. Potential adverse impacts of interactions between the space vehicle and the ionospheric plasma make it important to mitigate the plasma effects. Some of these effects are:

• plasma wave generation

• arcing and sputtering at significantly high negative potential relative to the plasma

• spacecraft charging at high inclination orbits

• corona/ESD phenomena

• current balance between the space vehicle and the ambient plasma

• geomagnetic field effects

Plasma Effects on Spacecraft Electrical Systems

As a spacecraft travels through this ionized portion of the atmosphere, it may be subjected to an unequal flux of ions and electrons and may develop an induced charge. Plasma flux to the spacecraft surface can charge the surface and disrupt the operation of electrically biased instruments. This is why the choice of spacecraft ground is an important consideration in determining where the spacecraft will float electrically relative to the surrounding plasma. The graphic above depicts an electrical interaction between a spacecraft and the surrounding plasma.

Plasma Effects on Spacecraft

The plasma environment around the space vehicle will be altered by the presence, operation, and motion of the vehicle. Potential adverse impacts of interactions between the space vehicle and the ionospheric plasma make it important to mitigate the plasma effects. Some of these effects are:

• plasma wave generation

• arcing and sputtering at significantly high negative potential relative to the plasma

• spacecraft charging at high inclination orbits

• corona/ESD phenomena

• current balance between the space vehicle and the ambient plasma

• geomagnetic field effects

The induced plasma effects can potentially cause rapid space vehicle external materials degradation, an enhanced EMI around the space vehicle. The most damaging of the effects are caused by electric potential differences between the space vehicle structure and the ambient plasma.

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