Four hundred kilometres above the Earth, human ingenuity has quietly solved one of survival's most intimate problems: how to drink tomorrow what you consumed today. NASA's Universal Waste Management System — a $23 million titanium apparatus four decades in the making — now recycles 98 percent of astronaut urine, sweat, and breath into water cleaner than what flows from most earthly taps. It is a story not of glamour but of relentless iteration, a reminder that the grandest journeys depend on the humblest engineering. As humanity turns its eyes toward Mars, this closed loop may prove as consequ