영어 지문 독해 도와주세요

밑줄 친 부분을 해석해도 이해가 잘되지 않아요.
과제인데 어려워서 도움 부탁드립니다.
the spaceship image is powerful. it suggests at once vulnerability, interdependence, and closure. spaceships are small and fragile in the depths of space, prey to meteorites and radiation and able to support life only so long as they remain intact. and they are also thoroughly and completely closed systems. there is no running down to the corner store for something that has been forgotten: all you have is what you have carried with you from the launching pad. everything must be either used over or used up. crew members of a spacecraft do not recycle because it is politically correct to do so; they recycle because if they do not they will die.
승무원들이 재활용을 하지 않는다고 했다가 바로 다음에 재활용하는 이유가 나와서, 두 문장이 어떻게 이어지는지 이해가 잘 안 됩니다.
all these qualities make the spaceship paradigm far better than other proposed paradigms for modeling a dynamic society on a finite planet. it is, nonetheless, not entirely satisfactory. the primary problem lies in its technological, human-constructed nature, which suggests that technology is the answer to environmental problems as well. worse: it suggests that when things begin to go wrong, the proper course of action is to tinker with them. both of these assumptions are correct for machines but dangerously misleading for the planet. life is an evolved system, not a designed one, and it cannot be treated as though a quick look at the blueprints and a couple of nails can cobble it up and make it run again.