Monday, December 07, 2009

The Importance of Lunar Water

Last month I tried to post about how the recent discovery of water on the moon is "kind of a big deal". But I got distracted by the shiny object of sloppy reporting. I promised to come back to the subject later. So here we go.

The first thing to understand about water is that it's very fucking heavy. If you have ever been stuck changing the bottle on the water cooler at work you know what I'm talking about.

A permanent Lunar Base will need a water supply. Shipping large supplies of fresh water to the lunar surface aboard rockets would be ridiculously expensive. True, NASA has some pretty sophisticated urine recycling technology, but that is just a conservation issue. You can't piss what you don't drink. A Lunar Base needs fresh water.

But the significance of finding water on the moon goes way beyond thirsty astronauts not having to drink their own pee.

Turns out, there is a lot you can do with water.

Of course, one of those things is the irrigation of plants. Studies were done using simulated lunar regolith and it was determined that all you needed to do was add a bit of carbon and nitrogen and you could grow plants in it. You also need water. Now we've found water. So it will be possible for astronauts to take seeds, carbon and nitrogen with them and they can plant lunar gardens to grow their own food.

Speaking of plants, they remove carbon dioxide (what we exhale) from the air and they produce oxygen (what we inhale). So having water on the moon and being able to grow plants is a natural, non-mechanical way of scrubbing the breathing air of carbon dioxide.

Speaking of oxygen, you may remember from high school chemistry class that water is two parts hydrogen to one part oxygen. You may also remember that by passing an electric current through water, you can separate it into its constituent components. Hydrogen. Oxygen. The process is called electrolysis.

That's all well and good, but where are you going to get electricity on the moon? Same place they get it on the International Space Station. From solar power.

Let me back step a moment.

The crater in which the frozen water was found is at the moon's south pole. It was chosen because a deep crater at either pole never sees sunlight. It is permanently dark and cold. However, the peaks around the edges of some of those craters never see any shade. They are permanently bathed in sunshine. A perfect location for a photovoltaic array to convert that sunlight into electricity and transport it to the bottom of the crater.

So Step 1 would be to land an unmanned, autonomous photovoltaic power generator and get it going.

Step 2 is to land an unmanned, autonomous lunar soil processor to use the power from the photovoltaic array to extract the water and separate it into hydrogen and oxygen via electrolysis and put them into cryogenic storage tanks.

Liquid hydrogen needs to be pressurized and chilled to −423.17 °F. Liquid oxygen requires pressurization and a temperature of −321 °F. That's pretty fucking cold! On earth, it takes a lot of sophisticated equipment to generate temperatures that cold and maintain them.

Guess what the ambient temperature is at the bottom of those polar lunar craters? Right around −400 °F.

So let's recap.

An automated power generation station and an automated lunar soil processing plant have harvested water from the lunar regolith and separated it into cryogenic storage tanks of hydrogen and oxygen.

So what?

I'll tell you so what. Before you even send astronauts to the moon, you know that there is already a supply of hydrogen and oxygen waiting for them that they don't have to take with them.

Not only does the oxygen give them air to breathe, but there are a couple of different ways you can recombine the hydrogen and oxygen which can be pretty useful for a lunar base.

You can recombine the hydrogen and oxygen explosively in the form of rocket fuel for the return trip home. This is fuel that doesn't have to be launched from earth and carried with you. It's already there waiting for you at the lunar gas station. This is huge!

You can also recombine the hydrogen and oxygen peacefully through a polymer electrolyte membrane and generate electricity in a fuel cell.

Guess what the byproduct is from generating electricity by recombining hydrogen and oxygen? That's right. Water. Which can again be used for drinking and irrigation.

Water is one of two valuable resources to be found on the moon.

The other even more valuable resource is Helium-3.

More on that another time.


Dan said...

Great post - thank you for the explanation.

Al said...

Excellent!! Good read XO.