Orbital station
Resupply vehicle
Launch site
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A space station cannot manufacture the water, oxygen and CO₂-scrubber sorbent its crew consumes every day — every gram has to arrive on a cargo vehicle launched from Earth. This simulator models that resupply chain as a continuous-review (s, Q) inventory system: a consumable buffer drains at a controllable daily rate, a cargo launch is triggered automatically once the buffer falls to a reorder point, and the delivery arrives after a stochastic transit time shaped by a lead-time-jitter control. Live readouts track the buffer level, days of runway remaining, missions flown, and a stockout-risk percentage computed from the same safety-stock statistics real mission planners use to size resupply cadence for the ISS.