Crew is unaware that their 'space voyage' is a simulation...

[apgw]

Here is the plot; it was written at least 30 years ago, but I don't know the author/title. Any ideas?

In brief: a long space voyage from earth to some star; the psychologist is lively and normal, everyone else, including the main character (MC), is much less so; MC notices an older member always hanging out at one spot in the craft. Later, the older member dies (natural causes). MC investigates the spot, sees a crack in the ship(!) and sees that they are not on a voyage at all but on an airstrip. The project is a simulation of a long voyage, to study its effects; the psychologist has his own escape hatch to the outside world, and is there to observe them. I forget the ending, but that is the essence of the plot.

[Brightonian]

Kinsgley Amis once wrote a story with the same premise, but I can't remember whether the details match your description.

[Guest]

This is a long shot but what about "Capricorn One"? Don't know if I ever saw the whole thing but there is a certain thematic similarity. Check it out and let us know...

[Bright]

The difference is that the crew Capricorn One know it's a simulation, they just don't find this out until "take off".