In another thread I've started a discussion about the ethics of a three-generation long trip on a large purpose-built starship. In this one, I'd like to talk about the feasability of such a ship.
As I pointed out in the other thread, the second generation in such a ship, the generation which is predestined to spend their entire lives on the ship with no chance of ever leaving, would undoubtedly be pretty unhappy. They're effectively prisoners on the ship.
With them all destined to live in the same vessel for their entire lives, I'd imagine that depression and anger would be widespread amongst the crew. Particularly as they grow older and the reality and tedium of their situation starts to kick in. I can easily imagine many of them choosing suicide over a life on the ship. If that happens then there's a big problem. What if someone vital puts a gun to their head? You've lost him, all his skills and an extra set of hands. And maybe even vital genetic diversity if he kills himself before reproducing.
Now, one guy doing it wouldn't be too much of a problem. Presumably there'd be more than one person for each job, and the required manuals around to give others rudimentary education in the field in question. But what if the ship is suffering dozens of suicides per year? Even on a ship with a crew in the thousands, that sort of attrition will start to take its toll.
Such a suicide rate would mean losing someone, and all of their skills and knowledge, once a month on average. Each time that person has to be replaced. Someone else has to be drafted in to do their job and be given training in that field. That person now has two jobs to do - their new job and the one they were doing previously.
Initialy this wouldn't be a problem, but as the list of deaths grows, the crew and the ship itself will be put under increasing stress. Most of the crew will be performing two or more jobs. This means less time spent on lower-priority tasks. This means less time for the crew to rest and relax. This means added mental strain on everyone on the ship. This means the possibility of some systems on the ship failing as there is less time to perform required maintanence and those doing it would probably only have a basic idea of what to do anyway. If systems do indeed start to fail, expect pressure on the crew to shoot through the roof.
Whether or not systems do start to fail, all of the added pressure on the crew will start to mount up. The suicide rate would undoubtedly rise, particularly as time goes on and more and more of the crew look to death as a release from the prison that is their ship. This stress would also manifest itself in the form of violence between members of the crew. This may very well lead to murders on the ship, increasing the stress levels yet again. Hell, it's possible that there'd be attempted mutinies against the ship's officers or serious religious violence (I'd expect many would turn to religion as another means of escape from the ship).
In any case, as time goes on it's almost a given that a large number of people will die, either due to violence or suicide. Those of the third generation old enough to work would be very quickly drafted into service, but with so many dead and so many vital skills and pieces of knowledge lost, their training would be basic at best, their knowledge gleaned mostly from any manuals that were left on board the ship.
With a constantly rising suicide rate, high chances of serious violence amongst the crew and a general atmosphere of anger and apathy towards their situation and the mission itself, I can easily see the ship itself starting to fail as vital maintanence stops being carried out. The situation would likely improve drasticaly once the third generation takes over, if only for the fact that they know that they have something to live for (the chance to get off the ship onto the planet). Their knowledge and technical expertise would be basic, but likely sufficient to get them to their destination bar any serious accidents.
In the end, I think it's likely that the ship would reach the destination planet, but in a poor state of repair and with a much lower population than was expected when the ship was first launched. And this doesn't even factor in things such as equipment malfunctions, serious accidents, incompetant personel, etc.
And that's just for a three generation long voyage. Can you imagine what it would be like if it was a six generation long trip? Each generation destined to die in space would become more and more apathetic and angry than the last. Simple attrition would wear down the crew's numbers to a point where vital maintanence simply can't be carried out. I predict that such a ship would fail to reach its destination.
So, your thoughts on this matter?