Harvesting energy from gas planets

[Jamezmon]

Hello, just wondering if it would be theoretically possible to harvest, for example hydrogen, as a clean fuel source from the gas planets? Surely there's an equation where mining / harvesting operations become profitable from what are obviously incredibly rich sources of useable energy? Or is this totally impractical, even with uber-forward-thinking scifi goggles on?

 

Thanks!

[Sensei]

Hydrogen requires Oxygen to become fuel.

Similarly other carbon-based fuels.

They need some kind of oxidizer.

Hydrogen and Oxygen after liquefying could be used as source of energy for rocket in further travel to other stars.

Bringing them (at least Hydrogen-1) make little sense (as we have oceans of it already). Bringing Deuterium would have some sense.

But gas giant planets have much stronger gravitation than Earth, and "start" from that planet, let's say from upper level of atmosphere, would take much more energy than start from the Earth.

It would be better/more practical to use Hydrogen and Oxygen from water, from some ice comet, or asteroid.

But the whole factory converting them to gas, then liquefying would have to be on them.

 

Unless you meant Hydrogen for fusion?

But proton-proton fusion is problematic, and gives little energy 0.42 MeV per reaction,

in comparison to proton- Deuterium, Deuterium-Deuterium, Deuterium-Tritium (17.6 MeV per reaction) fusion reactions.

These give even 40+ times more energy.

But Deuterium has just 115 ppm abundance (on the Earth).

[J.C.MacSwell]

Hydrogen requires Oxygen to become fuel.

Similarly other carbon-based fuels.

They need some kind of oxidizer.

Hydrogen and Oxygen after liquefying could be used as source of energy for rocket in further travel to other stars.

Bringing them (at least Hydrogen-1) make little sense (as we have oceans of it already). Bringing Deuterium would have some sense.

But gas giant planets have much stronger gravitation than Earth, and "start" from that planet, let's say from upper level of atmosphere, would take much more energy than start from the Earth.

It would be better/more practical to use Hydrogen and Oxygen from water, from some ice comet, or asteroid.

But the whole factory converting them to gas, then liquefying would have to be on them.

 

Unless you meant Hydrogen for fusion?

But proton-proton fusion is problematic, and gives little energy 0.42 MeV per reaction,

in comparison to proton- Deuterium, Deuterium-Deuterium, Deuterium-Tritium (17.6 MeV per reaction) fusion reactions.

These give even 40+ times more energy.

But Deuterium has just 115 ppm abundance (on the Earth).

To harvest as an energy source? You can't even break even if you simply plan to reoxidize the hydrogen.

[Jamezmon]

Yeah I think essentially I meant if we have powered the earth so far by mining fossil fuels from mostly plant and animal matter, is there a future where fuel could be extracted from the gas planets? Digged a little more and for example extracting methane from Uranus's atmosphere? Or any other compounds or elements which any gas planet is rich in which we could do with / use?

[Sensei]

To harvest as an energy source? You can't even break even if you simply plan to reoxidize the hydrogen.

True. +1 for good point.

But I was talking about making fuel for rockets. Electricity is poor fuel for rockets.

Split water molecule using one source of energy like solar panels etc.

Then in rocket engine burn Hydrogen with Oxygen to quickly accelerate it to high velocity.

 

Additional separation of water from heavy water, and semi-heavy water, to produce Deuterium, is additional useful byproduct.

(energy from fusion of Deuterium could be used to split regular water to Hydrogen and Oxygen, producing even more fuel for rockets)

Edited July 14, 2016 by Sensei

[swansont]

Yeah I think essentially I meant if we have powered the earth so far by mining fossil fuels from mostly plant and animal matter, is there a future where fuel could be extracted from the gas planets? Digged a little more and for example extracting methane from Uranus's atmosphere? Or any other compounds or elements which any gas planet is rich in which we could do with / use?

 

 

I suspect that extracting any chemical energy source is not going to be energetically favorable unless you are using it quasi-locally. If you could harvest something and use it immediately in rocket engines and you could move enough of it about so that you still had some left over after burning what you needed to, then maybe. You have to look at the economics at that point.

 

If we set up a space station around a planet, harvesting from that planet would likely be cheaper than bringing more fuel from earth.

 

CH₄ + 2 O₂ → CO₂ + 2 H₂O yield 55.5 MJ/kg of CH₄ but that requires 2 kg of O2 as well. So compare the potential of your planet against the 18.5 MJ/kg you can get from combustion (and modify by an efficiency of the reaction) and that will give you a best case for whether or not you would even consider doing this.

[Enthalpy]

The short answer is: no.

 

Comparing the energy of burning H₂ with O₂ (it achieves about 5km/s gas speed) with escaping Uranus (it needs 21km/s) isn't a definite proof as we could burn much resource at Uranus to bring a lttle part to Earth, but economics give an obvious answer with oil at 50$/200kg while 1kg just in low-Earth orbit costing over 10,000$.

 

Some bozos suggest again and again to mine ³He from the Moon and use it in fusion reactors, except that we don't have working fusion reactors, even with the much easier D-T reaction, nor do we even know how much ³He is available there. But it could be an attempt to synthesize tritium from ³He, as tritium serves for nuclear bombs and disappears over time. ³He looks a better precursor than lithium for that goal.

Edited July 17, 2016 by Enthalpy