As a Sr Systems Engineer, you will own the system architecture and top-level requirements that hold Helion’s fusion power plant together as a coherent whole — spanning the fusion machine, balance of plant, and the systems that connect them. You will work across electrical, mechanical, controls, plant, science, and business teams to decompose plant-level mission objectives into traceable subsystem requirements, drive the trade studies that shape major plant architecture decisions, and define the interfaces between subsystems and suppliers through rigorous ICDs. You will lead technical reviews, own verification planning against top-level plant requirements, and maintain clear traceability from plant-level objectives down through the requirements hierarchy to implemented hardware. You will drive technical consensus across functional teams and represent the plant’s technical position in leadership and program-level reviews. This role is architecture- and requirements-focused, serving as the technical integration point across subsystem, science, and business teams at the plant level.