> There are exactly nine spacecraft that humans have ever flown in. Only the Mercury/Gemini/Apollo programs really accumulated any kind of experience
From the "classic" era:
Mercury: 6 crewed flights. [1]
Gemini: 10 crewed flights. [2]
Apollo: 15 crewed flights (including Skylab and Apollo-Soyuz missions). [3][4][5]
Vostok: 6 crewed flights. [6]
Soyuz: 147 crewed missions (and counting). [7]
There have been four generations of Soyuz [8], so it's unclear whether it should be counted as one, four (or more?) spacecraft types. That doesn't include China's derivative,
Shenzhou: 11 crewed flights. [9]
Moving on to modern times, we have
STS: 135 crewed flights (counting orbital only). [10]
Dragon 2: 10 crewed flights and counting. [11]
Counting Apollo's LEM but not different Soyuz generations as a separate spacecraft gets us to 9, but out of those, it's STS and Soyuz which stand out as having accumulated most experience.
And all that's ignoring space stations, which arguably are spacecraft too and easily account for the bulk of time spent in space by humans [12][13]:
From the "classic" era:
Mercury: 6 crewed flights. [1]
Gemini: 10 crewed flights. [2]
Apollo: 15 crewed flights (including Skylab and Apollo-Soyuz missions). [3][4][5]
Vostok: 6 crewed flights. [6]
Soyuz: 147 crewed missions (and counting). [7]
There have been four generations of Soyuz [8], so it's unclear whether it should be counted as one, four (or more?) spacecraft types. That doesn't include China's derivative,
Shenzhou: 11 crewed flights. [9]
Moving on to modern times, we have
STS: 135 crewed flights (counting orbital only). [10]
Dragon 2: 10 crewed flights and counting. [11]
Counting Apollo's LEM but not different Soyuz generations as a separate spacecraft gets us to 9, but out of those, it's STS and Soyuz which stand out as having accumulated most experience.
And all that's ignoring space stations, which arguably are spacecraft too and easily account for the bulk of time spent in space by humans [12][13]:
Salyut: 6 orbited, 34 crewed visits.
Skylab: 1 orbited, 3 crewed visits.
Mir: 1 orbited, 39 crewed visits.
Tiangong: 3 orbited, 10 crewed visits.
ISS: 1 orbited, 88 crewed visits.
[1] https://en.wikipedia.org/wiki/Project_Mercury#Crewed
[2] https://en.wikipedia.org/wiki/Project_Gemini#Missions
[3] https://en.wikipedia.org/wiki/List_of_Apollo_missions
[4] https://en.wikipedia.org/wiki/Skylab#Mission_designations
[5] https://en.wikipedia.org/wiki/Apollo%E2%80%93Soyuz
[6] https://en.wikipedia.org/wiki/Vostok_programme#Crewed_flight...
[7] https://en.wikipedia.org/wiki/List_of_Soyuz_missions
[8] https://en.wikipedia.org/wiki/Soyuz_(spacecraft)#Variants
[9] https://en.wikipedia.org/wiki/Shenzhou_(spacecraft)#Launch_r...
[10] https://en.wikipedia.org/wiki/List_of_Space_Shuttle_missions...
[11] https://en.wikipedia.org/wiki/SpaceX_Dragon_2#Crew_Dragon_fl...
[12] https://en.wikipedia.org/wiki/List_of_space_stations
[13] https://en.wikipedia.org/wiki/List_of_spaceflight_records#Du...