“You know you’re in space when you can tell by the amount of stars that are in the sky how much light’s coming down from the surface.”
OK, so let’s say, just for the sake of discussion, you’re in orbit around Earth. Every time your life support systems are in full use you’re collecting and using a certain amount of oxygen. How much oxygen? Lots. According to NASA, a man, woman, child, human can breathe oxygen continuously for about 90 days, about six years, or give or take a little.
But how far can you go in the spacecraft? How far can your body and mind go on life support, without forcing the rest of your life to an end? How long can you spend with your mind still there, free of your body? If you’re an astronaut, you’ve already lived most of the time, if not all of it, without a body. There’s no way to know how much space you could go into without going under. That’s why in most spaceships people have life support systems that continually try to keep them alive. If you can’t get to space, it might be because your life support systems didn’t know enough, or don’t know enough.
“In the shuttle, there were three stages of life support systems. There was life support on board the shuttle itself. That was designed to keep the shuttle alive in orbit, of course. The external life support systems, the space shuttle took off without life support. That wasn’t possible for the space station because the space shuttle and the space station are designed to work in orbit. But with a space shuttle you can take off without the external life support systems. That’s a big part of what enabled people to go to space to begin with.”
Most of the astronauts can be re-fed with nutrients from a tube that is periodically rotated around to constantly offer them something different. The astronauts, who spend most of their time in space sitting on spacecraft platforms strapped to the sides of their vehicles, have to do a lot of work to keep themselves alive, including a lot of space walks. If they stay within reach of their life support systems they don’t have to do much. But when they leave it becomes much harder.
“Once the shuttle does get to orbit and gets down to about 250 miles and enters the atmosphere we do have to put on our space suits and go outside in order to be able to come back up to life support. At that point you’re actually going to have to be re-fed because that life support that you had that was outside is not going to have any nutrition left on it. It’s going to require you to put your body to work in order to keep it alive, which you could do before, but you had plenty of other things to do to keep yourself alive and not have to worry about your life support system.”
A space station’s life support system can only continue life when the structure itself is in space. A space station that is in orbit may never have life support problems. But if a space station has life support problems, the life support systems are still in space. Space is actually too vast to do much with, but it’s much like a life support system. It doesn’t work unless the necessary parts are close by. The life support systems that are in orbit are close by but have a limited lifetime.