Sigrid Elschot: Then and Now / 2013 Early Career Award Winner

WHAT DID THE 2013 EARLY CAREER AWARD ALLOW YOU TO DO?

Newswise — Meteoroids and space debris travel at incredibly fast speeds. This speed gives them a large amount of energy. When they hit spacecraft, this debris can form a plasma that is extremely dense. The way this plasma expands can result in electrical damage to spacecraft, even if the impacting object is too small to punch a hole through the spacecraft.

The nature of this impact plasma is still not very well understood. My team is interested in determining fundamental properties of this plasma, including density, temperature, and composition. These properties are key to understanding how the plasma expands and interacts with the surrounding environment. These properties also can tell us whether the plasma will emit a radio pulse, like a lightning stroke or nuclear blast, which could be the culprit in damaging spacecraft. Furthermore, these plasmas are similar in some ways to those that are created for fusion energy.

The Early Career Award allowed me and my research group to develop simulation tools to understand these impact plasmas. Because impactors in space can be as small as a tiny grain of sand, our simulations need to capture a wide range of time and length scales. We applied different techniques to understand various aspects of the phenomenon. One simulation we developed focused on understanding how the energy of the impactor vaporizes and ionizes the material from the crater that it forms. Another simulation addressed the radio signals emitted from the plasma once it has started expanding.

The award also supported experiments that we conducted at specialized facilities to make physical measurements of impact plasmas as well as the radio and light signals they emit. The facilities we went to could shoot particles into a vacuum chamber that travel as fast as meteoroids and debris in space, but in a controlled lab environment where we could surround the point of impact with our sensors.

These simulations and experiments laid the groundwork for us to develop theories that explain why some impacts emit radio signals and others don't. This is a first step towards helping us understand how to protect spacecraft from impacts by meteoroids and debris.

ABOUT: 

Sigrid Elschot is an associate professor of aeronautics and astronautics at Stanford University. 

SUPPORTING THE DOE SC MISSION:

The Early Career Research Program provides financial support that is foundational to early career investigators, enabling them to define and direct independent research in areas important to DOE missions. The development of outstanding scientists and research leaders is of paramount importance to the Department of Energy Office of Science. By investing in the next generation of researchers, the Office of Science champions lifelong careers in discovery science.

For more information, please go to the Early Career Research Program page.

THE 2013 PROJECT ABSTRACT: 

Title: Experiments and Simulations of Hypervelocity Impact Plasmas

Hypervelocity particles, including meteoroids and space debris with masses smaller than 1 microgram, routinely impact spacecraft. Upon impact, a particle vaporizes and ionizes itself and part of the spacecraft surface, producing a dense plasma that expands and radiates electromagnetic energy. However, the behavior of the resulting plasma and its potential to produce a spacecraft anomaly remains unknown. This research effort will investigate plasmas generated by hypervelocity impacts in order to characterize the behavior of the expanding plasma and its interactions with the ambient environment. 

The project will include experimental campaigns to be conducted at a dust accelerator facility that can accelerate particles up to 60 km/s, which is representative of meteoroid speeds, and at a light gas gun facility that can accelerate larger projectiles up to 7 km/s, which is representative of orbital debris. The experiments will use plasma, optical and radio frequency sensors to characterize the dynamics and associated emission resulting from hypervelocity impact plasmas. This project will also combine the collected data with results from numerical simulations using particle‐in‐cell (PIC) and smoothed particle hydrodynamics (SPH) techniques. The results from both experimental measurements and simulations will provide a new understanding of the mechanism for the onset of instabilities and turbulence that can lead to radio frequency emission by these plasmas.

RESOURCES:

A Goel, N Lee, and S Close, “Estimation of hypervelocity impact parameters from measurements of optical flash.” International Journal of Impact Engineering, 84, 54, (2015). [DOI:10.1016/j.ijimpeng.2015.05.008]

AC Fletcher and S Close, “Particle-in-cell simulations of an RF emission mechanism associated with hypervelocity impact plasmas.” Physics of Plasmas 24 (5), 053102 (2017). [DOI:10:1063/1.4980833]

YM Hew, A Goel, S Close, and N Lee, “Hypervelocity impact flash and plasma on electrically biased spacecraft surfaces.” International Journal of Impact Engineering, 121, 1, (2018). [DOI:10.1016/j.ijimpeng.2018.05.008]

DOE Explains… offers straightforward explanations of key words and concepts in fundamental science. It also describes how these concepts apply to the work that the Department of Energy’s Office of Science conducts as it helps the United States excel in research across the scientific spectrum. For more information on plasma and DOE’s research in this area, please go to the “DOE Explains…Plasma” webpage. 

Additional profiles of the Early Career Research Program award recipients can be found at the Early Career Program highlights page. 

The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website.