Since developing the Solid Oxide Electrolysis (SOXE) stacks for the Mars Oxygen ISRU Experiment (MOXIE) program in 2017, the OxEon team has made significant advancements in both the scale and capabilities of the technology with the support of a NASA NextSTEP ISRU, STMD Tipping Point, and SBIR award. Newer variants of the SOXE stack have a five-fold increase in cell area and a 6.5-fold increase in cells per stack. The scaled-up stacks utilize an interconnect specially designed to allow for a sealed anode perimeter and internally manifolded collection of the 99.9% pure O2 produced during operation. Additionally, OxEon has investigated materials to improve redox tolerance of the nickel-based cathode. Demonstration systems have been built and tested with the missionscale stacks, under relevant test conditions, for Lunar, Martian, and terrestrial applications. Results from operating the mission-scale demonstration systems, both at ambient and relevant test conditions, will be presented.