Artemis program has plans for using Orion spacecraft to ferry the astronauts to the Lunar orbit, and then use Starship HLS to make the landing. This will require an ability for Starship to dock to other spacecrafts. As of March 2024, Artemis 3 flight is planned for September 2026. Starship docking should be tested before that.

There are also speculations of other possible missions that would involve docking Starship to other spacecrafts, like Crew Dragon.

This question will be resolved positively when we first see Starship docked to a non-Starship spacecraft, while in space. Docking should involve the docking adaptor, connecting to another spacecraft by e.g. holding it with a robotic arm doesn't count. However it will still count if two spacecrafts are docked, but the hatch between their interiors is not open.

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