Cislunar Travel and Breathing Gas

 

Mick is really flitting all around cislunar space these days. "Cislunar" is just a fancy word we space explorers use to mean "on this side of the moon" or "not beyond the moon."

He sent me this message today...

Here, Oleg and I are under the decontamination light at Lunar Gateway 5 . He was coming up and I was going down.

LG5 has an Earth-normal atmosphere of oxygen and nitrogen. But we're breathing pure oxygen at low pressure since we'll be in space suits almost all day.

Some explanation about breathing gas might be useful to non-astronauts.

Earth's atmosphere is made of mostly nitrogen (about 78 percent). The oxygen we need to stay alive makes up only about 21 percent of Earth's air.

We don't need to breathe nitrogen to stay alive, so we can throw it away and breathe pure oxygen. When we do that, we also reduce the weight of the overall gas.

Reducing the weight of the gas reduces the pressure inside a spacesuit, and that makes it easier to move; we win all around.

I think of it like this: suppose a pizza is made from dough, cheese, and English peas. If you remove the English peas, you still have a cheese pizza you can eat, but it's lighter than before.

If you want to amaze your friends, go look at Dalton's Law. We use it every day in space.