MARS-500

And what's interesting as well is that the space agencies use them to understand the psychological challenges for astronauts as well.

So ESA ran one quite a few years ago now, Mars 500, which was six men in a habitat for 526 days.

And they simulated as part of that the communication delay because of the distance, how far Mars is from Earth.

It can be anywhere between eight to 44 minutes to get a message all the way around.

Going crazy might not seem like a huge risk, You're out here for an adventure, after all, but cabin fever is real.

In 2011, the Mars 500 project simulated what it would be like for a year-long voyage to the Red Planet, with crew members undergoing realistic conditions.

No real-time communication with family, limited entertainment options, and limited living quarters.

At first, the trip was pleasant, with participants all enjoying each other's company.

Social collapse poses an even starker threat.

The Mars 500 experiment, which confined six volunteers in a simulated spacecraft for 520 days, documented significant psychological stress, sleep disruption, and interpersonal conflict even in a group that knew the simulation would end.

A generation ship offers no such assurance.

Mutiny, schism and factional violence are not edge cases on a millennial timescale.