Radio Frequency Emission from Hypervelocity Impact Plasma

Speaker: Alex Fletcher, Stanford University
May 5, 2015

Presentation

Abstract

Spacecraft are routinely bombarded with interplanetary dust particles called meteoroids. With impact speeds up to 72 km/s, most meteoroids possess enough energy to ionize and vaporize themselves as well as a significant portion of the spacecraft material upon impact, forming a plasma that rapidly expands into the surrounding vacuum. The associated electrical effects and potential for damage to satellite electronics through these processes remains largely unknown, but it has been proposed that under certain conditions this plasma can produce an electromagnetic pulse (EMP) which can threaten spacecraft electronics. This area of spacecraft engineering requires a deeper understanding of the underlying physics of the impact-generated plasma plume.

In this talk, I present multi-physics simulations of meteoroid impact plasmas. The simulations use a combination of computational continuum dynamics and discontinuous Galerkin particle-in-cell (PIC) techniques running on graphical processing units (GPU). The results predict a minimum velocity threshold of ~18 km/s for fully ionized plasma production, which matches with EMP measurements from impact experiments. The fully ionized plasma produces electrostatic oscillations that can couple to an electromagnetic wave that propagates away from the plasma. Near the impact site, this wave has a field strength that far exceeds the specification to which spacecraft are currently designed. Understanding key parameters of impact plasmas, as well as any EMP mechanisms, will aid in designing more robust and reliable spacecraft that are well protected in the space environment.

Biography

Alex Fletcher is a Ph.D. student at Stanford University in the Space Environment and Satellite System, which is run by Prof. Sigrid Close. Alex is also a member of the Engineering Risk Assessment team at NASA Ames Research Center. He recently defended his thesis and has an NSF fellowship to study turbulence in space plasmas with massively parallel simulations. Alex’s other interests are in spacecraft-plasma interactions, plasma propulsion, and meteors.

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