There are somewhat standard busses. Though you're correct, many use custom busses for their specific missions. https://en.wikipedia.org/wiki/Comparison_of_sate

There are somewhat standard busses. Though you're correct, many use custom busses for their specific missions. https://en.wikipedia.org/wiki/Comparison_of_satellite_buses https://en.wikipedia.org/wiki/Comparison_of_satellite_buses For example, the SSL 1300 apparently has hosted 118 satellites so far: https://en.wikipedia.org/wiki/SSL_1300 https://en.wikipedia.org/wiki/SSL_1300 Though maybe the distinction between "satellite" and "spacecraft" bears importance here.