Propelling a spacecraft to get us to another planet is just one challenge. Another is making sure we have the resources to stay alive on board our spacecraft while we make our way to our destination. Even a visit to a nearby planet would require months of travel. With weight and space at such a premium, how do you determine how much water to bring and how do you manage it?
To say that every drop of water aboard a spacecraft is precious is an understatement. On board the International Space Station there are systems that recycle 93 percent of the water used [source: NASA]. The processes purify water so that it may be used repeatedly, reducing the need to send up more water from Earth.
That means gray water -- the waste water produced after cleaning dishes, clothes or even people -- can be made into drinking water again. But that's not all! Even sweat and, yes, urine are processed. Everything is filtered out and only pure water remains.
The waste water moves into a distiller. The distiller rotates in order to simulate gravity -- otherwise contaminants in the liquid wouldn't separate. Water passes through a filtration system that uses materials like charcoal and chemical compounds to bond with contaminants, letting only the water pass through.
A long space flight won't have the chance to pick up more water along the way. Conserving every drop possible will be a necessity. And some of that technology may even find its way into systems down here on Earth.