The Oxygen Generator Assembly (OGA) aboard the International Space Station (ISS) consumes a substantial portion of the overall Environmental Control and Life Support System (ECLSS) power budget (32.6% 1 ). It has been deemed both unreliable and cumbersom 2 . In preparation for long-duration deep-space missions, where resupply is impossible, reliable and energy-efficient systems are needed to produce oxygen for life support and hydrogen for rocket fuel 1 . However, under microgravity conditions, traditional density-driven mechanisms such as buoyancy-driven bubble detachment become ineffective 3 . Consequently, gas bubble froth accumulates on electrode surfaces, significantly elevating electrochemical overpotentials and obstructing ionic transport, thereby diminishing electrolysis efficiency significantly. Recent terrestrial simulations have examined bubble-induced effects on overpotentials 4 , yet there is not a comprehensive framework for electrolysis in microgravity. Here, we propose the first integrated theoretical model that explicitly incorporates reduced gravitational effects and microgravity-specific interfacial phenomena into time-resolved simulations. Using Bremen drop-tower experiments at different hydrogen generation rates for validation, we demonstrate how interlinked electrochemical and fluid dynamics can be accurately captured under microgravity conditions and illustrate these phenomena' critical impact on hydrogen generation rates. These findings provide foundational insight into the high-performance, robust electrolyser systems designed for extended deep-space missions. 1 Ross, B., Haussener, S. & Brinkert, K. Assessment of the technological viability of photoelectrochemical devices for oxygen and fuel production on Moon and Mars. Nature Communications 14 , 3141 (2023). 2 Jones, H. W. in International Conference on Environmental Systems (ICES 2016). 3 Brinkert, K. et al. Efficient solar hydrogen generation in microgravity environment. Nature Communications 9 , 2527 (2018). 4 Ross, B., Haussener, S. & Brinkert, K. Impact of Gas Bubble Evolution Dynamics on Electrochemical Reaction Overpotentials in Water Electrolyser Systems. The Journal of Physical Chemistry C 129 , 4383-4397 (2025).