Spaceship Earth

Down there is my spaceship earth. It has 20 members and it will succeed in keeping a crew alive for 20 years. Although, it cannot carry 20 years worth of supplies. So, we have to cycle food, water, and oxygen. It is actually quite simple. For oxygen we put in a greenhouse since trees and plants provide oxygen. And for food we have a farm, which contains sheep, chickens, and crickets. Water was the hardest by far. We took three classes in order to completely figure it out. We had to create water purifiers, which work by evaporating liquid waste and collecting the pure water that forms on the top of the purifier.