You stay useful until you are not.

The yellow number wins. Your thoughts become a soft hallway. You try to tell Mira a plan that involves the Moon, a garden hose, and a button that does not exist. Jax grabs your harness. Okonkwo’s voice recedes as if she had walked into another room while standing still.

You wake in a restraint with a mask biting your face and a headache like a drawer slammed on a finger. CO2 is down. Time is not. Apoapsis is a thing that happened without you. The low pass already wrote heating on the hull. Mira flew a backup needle and kept heads counted. The mission is a limp toward a rescue window.

Okonkwo holds the spent cartridge where you can see it without sitting up. “Oxygen was fine the whole time,” she says. “You still went to sleep. That is the trick.”

THE END

What you learned: you can have oxygen and still be poisoned by carbon dioxide. CO2 makes you sleepy and sure. Life support is chemistry first, heroics never. A spent lithium-hydroxide cartridge is a clock for your brain.