Star Trek

I have often thought what would be necessary to build and maintain a generational star ship to travel to neighboring star systems.

Near 100% efficient use of materials and energy. Recycling everything. Everything that is lost has to be replaced and a ship traveling for decade in deep space would have no resupply station available. This miniature ecosphere would be very difficult to engineer and I don’t think that I could stand to live in it. Any more than a few people would be hard to maintain.

Gravity: We need gravity to stay healthy. A large rotating ship perhaps.

Very good thermal isulation. Even the slightest radiated heat draws too much energy from the system and has to be replaced.

Farm land or its equivalent. Most of the ship would be needed to supply the few people with food and water. And the bigger the ship the harder it is to achieve the other things plus propel it.

I like this topic and am interested in ideas you may have.

One concept is that it would scoop up the interstellar gases (mostly vacuum, but once it gets moving really fast it will sweep out so much volume each second that it will have appreciable material in it), and use them as fuel. Hopefully the interstellar gases will contain mostly hydrogen, and we’ll have fusion power perfected before we launch this.

That will eliminate the need fro thermal insulation. The fusion will produce waste heat.

If we don’t have something like this, then it could be rather hard to keep the lights on in the ship for decades.

Robert Heinlein wrote an excellent story about a generation ship. He said it was designed to have "no moving parts," the idea being that moving parts necessarily wear out after awhile. But that would be quite a trick.

No reason why a generational ship couldn’t outlast the inhabitants (who would be breeding with each other and since the genetic pool is small would gradially become less than "perfect").