Research Objectives:

Research objectives are to:

(1) Define new standards and requirements for when the test environment is sufficiently “space-like” for highpower EP testing.

(2) Develop procedures and techniques for facility design, upgrades, and thruster operation to meet testing requirements.

(3) Demonstrate tools and methodologies based on physics based models to make probabilistic assessments of in-space performance and lifetime from measurements made in non-optimal test facilities

(4) Educate and train the next generation of engineers and scientists to implement high-power EP.

Research Plan:

JANUS will address the challenge of predicting the performance and life of highpower EP devices in-space through a fully integrated research program with four interdependent research pillars: (1) Thruster Testing, (2) Facility Fidelity, (3) Diagnostics and Fundamental Studies, and (4) Physics-based Modeling and Integration.

Physics-based Modeling

The focus is to develop multi-fidelity/multi-physics computational, analytical, empirical, and theoretical models and coordinate them with experiments to provide a means to predict thruster performance and life in space. The results are used to improve EP ground testing and facilities. The effort leverages state-of-the-art models that are directly applicable and extensible to JANUS objectives and adds new physical processes to existing models. The goal is to demonstrate tools and methodologies based on physics-based models to make probabilistic assessments of in-space performance and lifetime from measurements made in non-optimal test facilities  The effort will deliver several new tools, strategies, and guidelines for evaluating existing infrastructure and designing new infrastructure for testing high-power EP. 

Uncertainty Quantification 

JANUS approaches the challenge of facility effects modeling, mitigation, and extension probabilistically and allows the concept of reduction in uncertainty to drive our efforts. Uncertainty quantification (UQ), as applied to systems with unknown physics—so-called epistemic uncertainty—is proving to be an increasingly powerful tool for generating extrapolative measurements.  UQ and probabilistic risk and mitigation are used to determine and guide modeling and experimental efforts and ensure the interdependence of all modeling and experimental work within JANUS. Additionally, the effort is coordinated with the experimental efforts to ensure that essential data is obtained for model verification and validation (V&V).

Fundamental Studies

The focus is to elucidate unexplored aspects of thruster-facility interactions. The effort develops and employs new diagnostics with well-characterized uncertainty in high-power thruster tests and conducts fundamental plasma-material interaction studies on surfaces with flight features. The measurements enhance our understanding of the facility's far- and near-field pressure effects, contamination, and electrical coupling. The fundamental studies focus on the low-energy regime of ion sputtering of materials, and they characterize the carbon deposition processes using a novel carbon isotope tracking technique.

High-Power Ground Tests

We are leveraging the insight gained in the other areas to develop mitigation strategies to compensate for these effects via modeling and experiments. Systematic evaluation of these mitigation strategies is leading to new standardized tools, techniques, and ground-testing methodologies to achieve the ultimate goal of extending the results of high-power ground tests to in-space operation. 

The effort will focus on HETs and GITs operating on xenon and krypton gases. The extension of the modeling, mitigation techniques, and standards to high-power testing will require the combined efforts of all four pillars.

To ensure efficient integration of these efforts and achieve practical results in the five-year timeline, JANUS will use uncertainty quantification (UQ) and sensitivity of the overall thruster performance and life models to drive and accelerate the modeling and experimental inquiries. Unexplained physics and unknown properties will be treated as sources of uncertainty in the performance and life models that impact confidence in the predictions. Thus, the UQ and sensitivity analyses will accelerate the research by focusing the efforts of the team on processes that require higher-fidelity simulations and more in-depth targeted experimental investigations toupdate models and reduce the uncertainties in predictions. We leverage this insight to develop mitigation strategies to compensate for these effects via modeling and experiments. Systematic evaluation of these mitigation strategies will lead to new standardized tools, techniques, and ground-testing methodologies to achieve the ultimate goal of extending the results of high-power ground tests to in-space operation.

This innovative research integration plan will produce research efforts, tools, and databases that represent a huge return on investment and were not conceived in the past because of insular, disjointed investigations.

Research Impact:

This effort will deliver several new tools, strategies, and guidelines for evaluating existing infrastructure and designing new infrastructure for testing high-power EP. These include validated models for the response of HETs and GITs to the facility, new physics-based standards for testing and modeling that encapsulate best practices for mitigating and/or compensating for facility effects, and new standardized diagnostic techniques for characterizing the effects of the facility on thruster operation. We will collaborate with government and partners to incorporate our advancements into present and future research and development processes.

Furthermore, JANUS will employ and graduate many university graduate students. Our work will transform them into engineers and scientists with the skills needed to enable the development of high-power EP technology.