What services and actions a spaceship must provide to keep its crew alive on the journey to mars?

Same as with the lives of human in Earth, astronauts need food, water and shelter in deep space. Before the journey, the amount of food is estimated. A trip to Mars and back may take more than three years. Therefore the estimated amount of food is around of thousands of kilograms. For three year mission, a quartet crew will need more than 10 thousand kilogram of food for three meals each day. Five months before the journey, the food is tested for the gravity of space. Because water is heavy, its amount is reduced. Water is produced as a byproduct of fuel cells.

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