Keeping an entire population of humans alive (possibly around 20,000 - 40,000 individuals [1]) on a space ship for at least 100 years (time required to reach Al

Keeping an entire population of humans alive (possibly around 20,000 - 40,000 individuals [1]) on a space ship for at least 100 years (time required to reach Alpha Centauri with nuclear based propulsion [2]) is quite a technological challenge. So I wouldn't say it's just political, but I agree it's plausible. [1] http://www.sciencedirect.com/science/article/pii/S0094576513004669 http://www.sciencedirect.com/science/article/pii/S0094576513... [2] http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion