Keep the essentials
moving in circles.

A viable cabin must control carbon dioxide, humidity, trace contaminants, temperature and pressure as well as oxygen. Sensors need calibration and cross-checking; fans and ducts must prevent poorly ventilated pockets. The concept separates routine regenerative equipment from contingency supplies and emergency scrubbing. Consumable quantities require a defined crew workload, leakage allowance and suit-operation schedule.

NASA’s ISS experience provides valuable hardware heritage, but its demonstrated recovery performance cannot simply be assigned to a lunar habitat. Water use, recoverable waste streams, processor losses, brines, cleaning, hygiene and stored emergency reserves must all enter the balance. Commissioning also requires initial fill water. Our baseline takes no credit for mining lunar water.

For illustration only, four people using 4 kg per person per day for a limited potable-water allowance consume 480 kg over 30 days before recycling. If 90% of that exact stream is collected and recovered, the ideal makeup is 48 kg. This excludes hygiene, food preparation differences, oxygen generation, leakage, EVA, startup inventory and contingency. It is a teaching calculation, not the mission manifest.

Ground demonstrations should combine representative metabolic loads, humidity, contaminants, fluid handling and maintenance. Lunar gravity changes phase separation and other fluid processes, so space heritage alone is insufficient. Tests need failures: stuck valves, bad sensors, loss of power, microbial contamination, cartridge exhaustion and repair while the crew relies on the refuge.