How do you get food and oxygen?

We have to launch it all. It takes about 10 kilowatt hours per kilogram of energy to get into orbit. We basically get things above the atmosphere and go sideways fast enough about 8 kms a second, that we literally just fall over the horizon. That is what an orbit is. That energy, that velocity takes a tremendous amount of propellant to push us there, so about 10% of each rocket we launch makes it to orbit, and we have to very carefully balance how much food, oxygen, and water we bring. Aboard the Space Station we recycle the water we respire, it gets into the humidity of the atmosphere, it is collected on the air conditioners, we take that water, we put it into a pair of electrodes, and create oxygen out of that recycled water, so we never have to bring much oxygen to the station, we simply use what’s left over from our perspiration for it. The hydrogen is separated and blown over board. As we breath that oxygen it turns into carbon dioxide, that is scrubbed and sent overboard. The carbon comes up in the form of our food, the oxygen comes up in the form of our water, so we actually do get to recycle things a couple of times.