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Comment by victorbinetruy | Hacker News Reader

Let's say we found a way to make water the fuel of the future (that is used for all (most) of our needs), should we use it? Isn't water (one of) our most precious resource? Should mankind really risk using (wasting) our precious water? Well, we wouldn't loose it if we use it on earth, but space would be a different story (although, if we only use water as fuel for spacecrafts... it would take a while before we deplete the earth of it). What are your thoughts?

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The only way water would be fuel would be via fusion of the hydrogen portion. Of that it is only currently realistic to use the portion of water that contains deuterium which is a relatively small portion of all water on earth. Also fusion would produce a large amount of power from a small amount of hydrogen, so it would have a small impact on earths water supply. So yes we should use it if we can.

Fresh water is a precious resource here on Earth because it is so energy intensive to desalinate ocean water. Once we are capable of mining other bodies in the solar system, there is plenty of water to extractt from other planets, moons, and comets. Getting there and back has proven to be by far the hardest part so far. Either way, water and methane will be the primary hydrogen source for liquid propellant, ion engines, and nuclear rockets.

In space, life support is a closed loop system so a lot of water is recycled anyway and with aeroponics, agriculture requires 80-95% less water. Any industrial uses of water will also likely have very efficient recycling (for example, Intel's Arizona plant recycles at least 60% of their water and their company goal is to get to 100% before mid-century). I believe even now, industrial water usage is far bigger than agricultural or personal.

On any given day tiny comets and asteroid deliver to earth many tons of water. The big ones we see a shooting stars. The giant ones are called asteroids. Only the real monsters actually touch the ground. Most burn up in the atmosphere, delivering their water as steam. So, no. Powering all of our rockets with water will not deplete the planet.

I'd be far more worried about the gold, platinum and other expensive stuff that satellites are built from. We aren't getting those back nearly as quickly.

Water is the space fuel of the future. Well, at least the space oil of the future - if you start mining asteroid and comets, water is one of the best component you can get: good for any life around, quite a good solvent if you need one, and more importantly can be a fuel like this or be transformed into oxygen and hydrogen, which is rocket fuel as well.

Also, good luck depleting the water on Earth with space travel. There would be other issues way before this happens.

Right, like figuring out why you would want to bother lifting significant amounts of water mass into space in the first place.

There's actually quite a lot of potential water available in the Solar System.

https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...

First, it's fresh, drinkable water, delivered to people who need is, is precious. Not just "water". Second, 7 billions of people who drink and bathe and eat water-dependent food every day and a space mission with a few tons of distilled water every now and then are on completely different scales.

Let's imagine that we have a new fuel source that works with dirt and sand. Whenever you can excavate, you can use it for fuel. How long until we run out of "land"? Same concept. Except that we have more ocean surface than we have landmasses.

Potable water is precious. Water in general is not.

At the time we start using a lot of it (enough to matter), we would also be capable to mine it from comets or moons.

You should read Isaac Asimov's "The Martian Way".

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