https://thenextweb.com/artificial-intelligence/2018/06/28/interstellar-space-travel-will-require-lots-of-sex/

A pair of scientists from France developed an algorithm to determine the minimum amount of sexually active couples it would take to maintain a human crew inside of a spaceship for 6,300 years – the time it would take to reach the nearest star beyond the sun.

Let’s get it on: The Heritage algorithm, as its called, powers a simulation that determines the likelihood of humans reaching Proxima Centauri using current technology. In order to get people there from Earth, the mission would require multiple generations of people to live their entire lives in space while the vehicle makes the millenniums-long voyage. And that means the initial crew, and subsequent offspring, would have a responsibility to procreate.