[zcami2]

Hello,
I'm doing an assignment on the plausibility of a hydrogen economy.  As part of this assignment I was given this quote to review:

"… since hydrogen is the most abundant element in the universe, it offers an essentially limitless source of energy."

I've been researching the topic and haven't yet found a site saying that hydrogen can be harvested from space.  What form is the hydrogen which comprises the universe in?  Are there hydrogen molecules floating about in outer space or does this hydrogen mostly comprise stars such as our sun?  I would think that if the later were true that this hydrogen would be unable to be collected and used by humans and even if there were hydrogen molecules floating around in outer space the energy required to harvest this hydrogen would be quite high anyway wouldn't it?  So I guess my final question is can hydrogen be harvested from the universe?

Thanks
Z.C.

[Arkcon]

Space is commonly described as "hard vacuum", so while no vast area of space is truly "empty" the hydrogen that's not bound up in stars is really spread out very thin.

[Arkcon]

Look at this page, http://www.spaceweather.com/ , it lists the density of the solar wind -- the charged particles the sun emits into the general vicinity of the Earth.  You'll see particle densities on the order of 1 or 2 protons per cubic centimeter.

[vmelkon]

So I guess my final question is can hydrogen be harvested from the universe?

Perhaps.
Jupiter is said to be 89.8% hydrogen.
Saturn is said to be 96% hydrogen.
Neptune is said to be 80% hydrogen.

and of course, there are interesting compounds out there: NH3 and CH4.
You can burn both of those.
Unfortunately, the gravity on those planets is very high and conditions are harsh. It might be difficult to send a machine and bring back something.
I don't know which moon it was, but it had gigantic pools of methane and astronomers think that it even rains methane there. It should be possible to land on that moon and come back to Earth.

But if you mean getting hydrogen from space, that would be hard as the posters above me said.