NASA's Artemis II mission carries four astronauts around the Moon using a computer system that dwarfs the 1960s Apollo Guidance Computer. The modern stack runs every safety‑critical function—from life support to communications—onboard the Orion capsule, where a single failure would be unrecoverable 250,000 miles from Earth. Engineers therefore built a fault‑tolerant architecture that expects radiation‑induced bit flips and hardware faults without any downtime.

Two Vehicle Management Computers each house two Flight Control Modules. Every module holds a self‑checking pair of processors, giving eight CPUs that run flight software in lockstep. When a processor miscalculates from a cosmic‑ray event, the pair silences itself and the system switches to the next healthy module. Tests prove the craft can lose three modules in 22 seconds and still navigate safely.

Determinism relies on a time‑triggered Ethernet that shares a single clock, with an ARINC653 scheduler breaking work into major and minor frames. Triple‑modular‑redundant memory fixes single‑bit errors on each read, and a separate Backup Flight Software runs on different hardware for dissimilar redundancy. If total power is lost, a safe‑mode routine restores attitude and solar pointing, showing Artemis II’s resilience is unmatched.