Hydrogen to water

[PsiTraveller]

If I move 1Dton of water that is 14 m3 of water, 14 000 liters.

If I move 1 DTon/ 14 m3 of Liquid hydrogen and then combined that hydrogen with oxygen at my destination, how much water would I end up with? Assuming 100 percent of the liquid hyrdogen is converted to water.

Is it better to move water or hydrogen and then add oxygen at the destination?

 

[Galadrion]

As near as I can tell, 1 L of lhyd, combined with oxygen, produces approximately 600 mL of water (and more than enough thermal energy to vaporize the water, so unless you contain and condense the steam, you'll lose an awful lot of it). So 14000 L of liquid hydrogen should produce about 8400 L of water - slightly more, technically.

Now, whether it would be economical to ship Lhyd instead of water depends on a large number of factors. Do you have the equipment on the receiving end to combust the hydrogen without losing the water (or is keeping the water even a concern)? Is there sufficient oxygen available in the environment at the receiving end to allow the reaction? (Many places you're going to be shipping water to are also not going to have a great abundance of free oxygen.)

Mostly, whether it would make sense depends largely on why you're shipping the stuff to begin with. Most of the reasons I can come up with would lead to the conclusion that shipping water makes more sense. Even if you were shipping it to be fusion fuel, I think it would be slightly more efficient to ship it as water and electrolyze it at the destination - although there are probably more efficient compounds available for that transaction; methane comes to mind...

 

[Sigtrygg]

14 cubic metres of liquid hydrogen has a mass of 1000kg
1000kg of hydrogen produces 9000kg of water when combined with oxygen.
9000kg of liquid water takes up 9 cubic metres.

Liquid water is a better way to transport it if you are volume constrained.

 

[AnotherDilbert]

9000kg of liquid water takes up 9000 cubic metres.

I agree, with a slight change:
9000kg of liquid water takes up 9000 litres = 9 m³.

 

[Sigtrygg]

Transcription error - laziness on my part cut'n paste-ing and forgetting to knock the zeros off

 

[PsiTraveller]

Thank you everyone for replying. I could not figure out why it seemed my math looked odd. It seems counterintuitive to ship 14000 liters of something and get less than that at the far end of the journey.

 

[RogerMc]

Something I've been contemplating is the practicality of just hauling ice in a jump cargo net and reducing it to water while in deep space.

Doing this pretty much any ship with J2+ could slowly and painfully cross The Great Rift in J1 hops - and it is surely much cheaper if more laborious and risky than paying for drop tanks and then abandoning them.

So assuming you have a handy comet or an ice cap to laser a big chunk off how much of say 100 tons of ice (by volume obviously as this is Traveller) would you lose converting into x tons of fuel?

(and yes you'd obviously need some sort of specialised module to do this in with space and a power source to do your melting inside of it).

 

[Condottiere]

Spray paint your hull with water, and then harvest it, maybe with an adapted Roomba.

 

[SSWarlock]

Combining LHyd with oxygen to make water...didn't some guy named Mark Watney do that on Mars once? :wink:

 

[Condottiere]

He also has a biosphere and produces fertilizer.

 

[PsiTraveller]

I remember playing the zhodani conspiracy game years ago and rather than do the quests I realized I could buy water on one planet for 100 credits and fly to a desert world and sell it for 500 credits. Wash rinse repeat for an hour and I had the best ship upgrades you could buy.

 

[Reynard]

How much was overhead to transport the water each time?

 

[AnotherDilbert]

Something I've been contemplating is the practicality of just hauling ice in a jump cargo net and reducing it to water while in deep space.

Ica has a density of about 0.9 so 1 Dt ice contains 0.9 Dt water and can be converted to ~1.4 Dt LHyd.

The problem is that ice is not very stable in space. It has to be very cold to remain stable. It will evaporate in sunlight in orbit.

 

[PsiTraveller]

The zhodani conspiracy was a computer game, so overhead was not an issue. I could walk to the trading desk from the spaceship, click and buy the water, run to the ship, launch and fly to the next planet, land, trade and sell and back to the watery planet in under a minute.

https://en.wikipedia.org/wiki/MegaTraveller_1:_The_Zhodani_Conspiracy


I did not follow the plot line at all. Never did finish the game.

 

[AndrewW]

I did not follow the plot line at all. Never did finish the game.

Me either.

 

[RogerMc]

Something I've been contemplating is the practicality of just hauling ice in a jump cargo net and reducing it to water while in deep space.

Ica has a density of about 0.9 so 1 Dt ice contains 0.9 Dt water and can be converted to ~1.4 Dt LHyd.

The problem is that ice is not very stable in space. It has to be very cold to remain stable. It will evaporate in sunlight in orbit.

So 100 tons of ice can be converted to 90 tons of water and that converted to 140 tons of LHyd?

If you are hauling the ice to fuel multiple deep space jumps then presumably the instability will not be an issue?

 

[AnotherDilbert]

So 100 tons of ice can be converted to 90 tons of water and that converted to 140 tons of LHyd?

Yes.

If you are hauling the ice to fuel multiple deep space jumps then presumably the instability will not be an issue?

Probably. If we assume jumpspace has the same temperature as the space we launched from, that should be OK.

If jumpspace contains more energy you will arrive with a lot of water vapour or plasma.

If the ship dumps heat into the jump bubble (as it has to?) then the ice will probably melt.

None of this is well defined, so up to the Referee.

 

[RogerMc]

I always assumed that the jump bubble just negates all the normal laws of physics (which is what it is for) and anything that goes in maintains same temperature etc until it comes out again?

Plus it seems that all the stuff about starships (and by implication jump cargo nets) being covered with lanthanum jump nodes is only in one source of dubious canonicity anyway (MT Starship Operators Manual) so you can visualise the jump bubble as a real globular bubble extending some way out from the ship rather than just conforming to the shape of the hull.

Bizarre that after all these years no one has really described what being in Traveller jump space is like (compare and contrast to CJ Cherryh's Alliance-Union-Compact books where being in jump space is so disorientating most species spend it in a drugged sleep).

 

[Condottiere]

The density of hydrogen and oxygen are 0.0899 and 1.429 g/l at 0 degrees centigrade.
One liter of water will thus produce 111/0.0899 =1235 liters of hydrogen and 888.81/1.429 = 622 liters of oxygen. Note that according to Avogadro's law, the volume of hydrogen is about twice that of oxygen, because 1 mol of water produces 1 mol of hydrogen and 1/2 mol of oxygen.

 

[Sigtrygg]

Your example is for water being decomposed into hydrogen gas and oxygen gas.