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By Marshall Brain

HowStuffWorks.com

The international space station, is a giant orbiting laboratory bigger than a football field. It is so big that, if you know when it will be flying by, it is easy to see it pass in the night sky with the naked eye.

But have you ever thought about what it takes to keep people alive in the vacuum of space?

Imagine that we launch a big, sealed aluminum tube full of air, as big as a bus. We get inside, load the tube into the space shuttle’s cargo bay and release it into orbit 200 miles up.

The first big problem is the accumulation of carbon dioxide in this sealed tube. Every time a person exhales, there is carbon dioxide coming out. As the amount of carbon dioxide builds, it becomes a poison.

Carbon dioxide poisoning would kill astronauts faster than lack of oxygen would. So the space station solves this problem with a CO2 scrubber, chemical beads that absorb carbon dioxide. Periodically the carbon dioxide gets dumped into space and the beads are reused.

Next, the oxygen problem: On the space station, the main way to create oxygen is to split water molecules using electrolysis. For this process and other uses, the station needs to have a lot of water on board, stored in 20 gallon bags.

For backup there are oxygen tanks and solid oxygen canisters.

Other things you have to worry about in a sealed tube are humidity and other chemicals. Every breath contains moisture (breathe onto a mirror and you can see it). And every human farts 15 to 20 times a day (there is no way to stop it), releasing methane and other chemicals.

The moisture can be condensed out of the air and is actually reused in the space station. Stray chemicals such as methane are trapped with activated charcoal.

Our sealed tube is also going to need some kind of restroom. Without gravity or running water, this gets complicated. Urine is collected by a tube with a vacuum system. The water in the urine is recycled and reused.

Astronauts strap themselves to a space toilet to handle the solid waste. A strong current of air pulls solid waste into a collection bag. The bags get burned up during re-entry like other trash.

Now that the air is breathable and the restroom facilities are taken care of, it might be nice to have some electricity.

The station’s electricity comes from large solar panels much like the ones people put on their homes. Batteries store energy for use when the space station is in Earth’s shadow.

McClatchy-Tribune Information Services