When do astronauts return to Earth?

The typical duration of an expedition to the International Space Station is about six months. That pace is set by the cadence of launches, the service life of the vehicle waiting docked, and the medical monitoring of a crew that slowly deconditions in weightlessness. Each handover overlaps a few days with the next to transfer experiments and maintenance tasks. But the schedule stretches when something goes wrong: astronaut Frank Rubio ended up spending 371 days in orbit, between September 2022 and September 2023, because his Soyuz MS-22 lost coolant and another empty spacecraft had to be sent to pick him up.

The return begins with hatch closure and undocking; then, an engine burn slows the craft just enough for the trajectory to intersect the atmosphere. Modules that can't withstand reentry separate and burn up, and only the capsule, protected by its heat shield, passes through the white-hot phase before deploying parachutes. Soyuz capsules touch down on the steppe of Kazakhstan, cushioned in the final meter by retrorockets; Crew Dragon capsules splash down off the coast of the United States. The exact day is decided with little advance notice, depending on wind and sea conditions.

Nobody walks out. After half a year with no load, the heart pumps against a gravity that had stopped existing for it, bones have lost density, and balance takes time to recalibrate, so crew members come out seated in chairs and face weeks of supervised rehabilitation. The record for continuous time in space still belongs to Valeri Polyakov, who spent 437 days aboard the Mir space station between 1994 and 1995; his medical data still informs planning for a future trip to Mars.