Water as a fuel source?

when we are able to go to jupiter and mine it for hydrogen ....we will not need the hydrogen.

as that technology to get us there would also give us the energy source .....like fusion

 

okay one more time people .....hydrogen in not an energy source ...its an energy carrier

to make h2 requires energy from somewhere else ...like solar, wind, hydro, tidal, geothermal.....using the energy from those sources water can be split but since it is not 100% efficient , you have to put more energy into splitting the h2o then comes out in h2 gas.....then the h2 is stored ...liquid, compressed, nanopowder, etc. ....h2 is not easily stored takes additional energy to do this, its also an escape artist... you actually lose a percentage of it daily in storage....after storage you put it to use and lose additional energy to the inefficient engine, fuel cell, burner, etc. ..

so to put it simply...put in 5 quarters and you get 2-3 back

 

It amazes me how much this question comes up, and it shows how little people know of physics.

Why don't we just "burn" carbon dioxide? That would be about the same idea.

Because water or carbon dioxide, is already burned. It has already given up its energy, being chemically converted from high energy to low energy. Now how are we to get energy from a low-energy state, to an even lower-energy state, unless a lower energy state is found to be obtainable?

Although water contains hydrogen, water is not hydrogen, and energy must be added, to break apart the molecular bonds. Why don't we just get energy from springs, that haven't been wound up? Because it won't work. You can't run a grandfather clock, without lifting up or winding up the weights. The amount of energy required to break the molecular bonds to liberate the hydrogen, is at least, generally more energy, than can be obtained by burning the hydrogen.

Besides, you don't "burn" the hydrogen to power cars, but use it in fuel cells, which are more efficient, similar to a "battery" in some respects. But hydrogen isn't energy-dense enough, nor stable enough (not liquid) at room temperature, to be practical to power cars.

Now there is a way to use hydrogen as a fuel, but then it isn't about "producing" energy, but merely storing it. Build more hydro-electric dams or nuclear power plants, to produce the electricity for the electrolosis to liberate the hydrogen from the water. But then why manufacture hydrogen this way? Because it is needed for rocket engines, being able to be used as a coolant, having been chilled to ridiculously cold temperatures that would freeze most any other fuel? Yeah, rocket engines run so hot, they use the fuel as coolant, lest they melt. Why not just synthesize gasoline in this manner? It's a far more useful and stable fuel, for such things as cars, than hydrogen is.

 

I was thinking more along the lines, that the cost of bringing back the hydrogen, would greatly outweigh the value of the hydrogen.

Space transportation so far, is very expensive, hardly cheap, a practical reason why people have not been able to venture beyond the moon so far, and we have had to send robotic explorers instead, which fortunately don't need a return trip, sending back their observations and photos, to radio telescope antennas.

It would be far cheaper, to get hydrogen by adding energy, from water. It's often cheaper to mine in our "own backyard" so to speak, than to venture out to asteroids or other planets to do so. Just too far away with the current technology.

And as streamlight2 said, I would further add, that current rocket propulsion, or riding up into outer space upon a precariously-balanced explosion on a gas-guzzling rocket engine(s), isn't likely to get us very far at all. Better technology must be developed first, say like "anti-gravity" waves (as on The Jetsons cartoon) or "warp-drive" or "impulse-drive" (Star Trek).