One spacecraft design has been carrying people since 1967 — by being modified rather than replaced

The Soyuz that flies now shares its layout and its logic with the original, not its hardware. The current version is the MS — the latest update to the fourth generation of the design. MS stands for Modified Systems: a large number of individually small technological upgrades, made to lighten and modernise the spacecraft rather than to reinvent it. What has persisted is an architecture, refined continuously, not an artefact.

The same family of spacecraft carried crews to the Soviet Salyut stations, then to Mir, and then to the International Space Station. Each of those destinations had different approach, docking and endurance requirements, and each was reached by adapting Soyuz rather than by commissioning a purpose-built replacement. A vehicle used that way accumulates something no new design has: a very long record of how it actually behaves.

Continuous modification has a price. Improvements arrive as increments, so capabilities that would require a different architecture — larger crews, more downmass, reuse — do not arrive at all. The programme's beginning was also its most costly lesson: its first crewed flight, in April 1967, ended in the death of its pilot. What followed was decades of incremental correction rather than replacement.