The vision of NASA’s Artemis program is to lead humanity forward in the exploration of the Moon which will prepare us for the exploration of Mars. Paramount to the success of this program is the ability to provide reliable electric power throughout the lunar day and night. The terrestrial grid is primarily composed of AC systems to accommodate legacy grid infrastructure. However, DC microgrids are of primary interest to NASA because of the reduced transmission line and voltage level conversion losses, as well as the reduced complexity of interfacing with DC generation and storage elements such as photovoltaic (PV) panels and battery energy storage systems (ESS). Due to the extreme Lunar and Martian environments, typical terrestrial DC-DC converters often fail due to high energy single event upset radiation effects and extreme temperatures. To address these deficiencies, Mainstream proposes to develop a modular bidirectional isolated DC-DC converter to interface between low voltage sources and loads and the DC microgrid. To achieve this goal, Mainstream will first develop an electro-thermal simulation model of the converter and perform a trade study of available proven radiation-tolerant and temperature rated semiconductor options to maximize the efficiency and specific power of the inverter. Next, Mainstream will prepare detailed schematics for and design the power stage and control card PCBs. Mainstream will develop embedded firmware to control the converter and perform detailed hardware-in-the-loop simulations to validate the control architecture. Finally, Mainstream will detail the requirements for the thermal management system and develop a high-fidelity thermal model of the system.

Mainstream’s proposed converter is directly aligned with the Artemis Plan, NASA’s Lunar Exploration Program, and with NASA’s Global Exploration Roadmap. Providing reliable electric power in the extreme environments of the moon and Mars is essential for establishing long term exploration to support communication, space exploration vehicles, rovers, and ground-based habitation outposts. Specific NASA programs that could benefit include Advanced Exploration Systems (AES), Human Exploration and Operations (HEO), Gateway, and Artemis.

Mainstream develops power converters, including variable-frequency motor drives, active rectifiers, and isolated DC-DC converters, for demanding applications where commercial products are not suitable. Examples include bidirectional multiport DC-DC converters for spacecraft electric power systems and bidirectional battery isolator units and battery inverters for electric vehicle systems.