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PostPosted: Sun Nov 14, 2010 10:28 pm 
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I'm not familiar with the chemistry of it, but surely there has to be a volume change if you're adding and removing hydrogen from the compound?

(I guess one other problem is the annoying fact that Traveller ignores the mass of stuff (except in TNE) - realistically, mass should be a prime consideration for spacecraft since the more mass you have, the slower you go).

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PostPosted: Sun Nov 14, 2010 10:55 pm 
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EDG wrote:
I'm not familiar with the chemistry of it, but surely there has to be a volume change if you're adding and removing hydrogen from the compound?


Not necessarily, but in fact yes. The grains in the powder get very slightly larger as the lithium nitride reacts with hydrogen. Which means that after you cook the hydrogen out of the tank there is slightly more room in the pores between the grains of powder.

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(I guess one other problem is the annoying fact that Traveller ignores the mass of stuff (except in TNE) - realistically, mass should be a prime consideration for spacecraft since the more mass you have, the slower you go).

Indeed. This entire issue is all about Traveller's focus on volume rather than mass. Which is a very peculiar thing, given that spaceships don't actually need a hull.

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PostPosted: Mon Nov 15, 2010 2:45 am 
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Agemegos wrote:
That's the beauty of the lithium amide-lithium hydride mixture. You keep lithium nitride in a tank, as a fine powder. You pump in hydrogen, and at room temperature the lithium nitride reacts with the hydrogen to produce a mixture of lithium amide and lithium hydride (both solids). When you want to use the hydrogen, you heat the tank to 270 C. The lithium amide and lithium hydride react to release the hydrogen and leave lithium nitride powder in the tank (to be used again another time).


Great idea! Thanks.

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PostPosted: Mon Nov 15, 2010 6:59 am 
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DFW wrote:
Great idea! Thanks.

I feel embarrassed to get any credit for this. The idea came from engineers who are doing R&D on hydrogen-powered buses and trucks.

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PostPosted: Mon Nov 15, 2010 7:14 am 
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EDG wrote:
realistically, mass should be a prime consideration for spacecraft since the more mass you have, the slower you go

For a drive that produces a thrust, yes. It is conceivably that some sort of gravitic drive could impose an acceleration within a volume of space the way a gravitational field does, and that its performance might be dependent on volume and independent of mass the way Traveller M-drives were implied to be in LBB 2. Traveller chucks out Newton's 3rd Law: why not his Second Law too?

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PostPosted: Mon Nov 15, 2010 11:11 am 
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Alternatively, Traveller doesn't ignore mass it just assumes that all starships will have roughly the same density so therefore you can theoreticaly consider either mass or volume alone as a proxy for both, and they chose volume.

It doesn't stand up to very close examination, but then what does in Roleplaying?

Simon Hibbs


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PostPosted: Mon Nov 15, 2010 3:08 pm 
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I always liked the idea of Meta-Stable Metallic Hydrogen (wiki it, it is a real thing) as a fuel. It is 8 times denser than LHyd and stable at room temperature.

I have seriously considered using LHyd as the "Unrefined" version of fuel and MMH as the "Refined" version... 5 times as expensive for 8 times the fuel; but it cannot be skimmed. Haven't done it though.

I hadn't heard about the Lithium Cycle... that is interesting... have to think some more...

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PostPosted: Mon Nov 15, 2010 5:02 pm 
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Cyborg IM1 wrote:
I always liked the idea of Meta-Stable Metallic Hydrogen (wiki it, it is a real thing) as a fuel.

It's a "real" thing in the sense that it is really theoretical that it might be possible. There is no experimental evidence that it is actually possible, and no evidence that it actually exists anywhere. So it isn't an absurd thing to put in an SF setting, but it's not real in the sense that you can buy it by the kilo from ICI. Possibly it never will be. So a GM with grognard tendencies who wanted to maintain the strictures of OTU logistic might reasonably rule that there is no metastable metallic hydrogen in his or her TU.

Ammonia, ammonium hydrogen difluoride, and lithium nitride, on the other hand, are really real in the sense that you can buy them from chemical supply companies this very day. Declaring that they will cease to exist in the future would be a bit rough on verisimilitude and suspension of disbelief.

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PostPosted: Mon Nov 15, 2010 8:16 pm 
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I am seriously considering using that Lithium Hydride trick in MTU. I don't have to change the fuel requirements or anything, just say that rather than using LHyd (Liquid Hydrogen), that Refined fuel is actually Lithium Hydrid (LHyd?) and the "refining" process is what turns plain old everyday Hydrogen into enough fuel to run a Jump Drive. Without Lithium Hydride, you couldn't carry enough hydrogen to get the energy pulse you need to operate the Jump Drive.

No rule changes, just setting changes AND it gets rid of all that hydrogen at near absolute zero surrounding your living quarters.

ME LIKEY A LOT

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PostPosted: Mon Nov 15, 2010 11:31 pm 
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Agemegos wrote:
Indeed. This entire issue is all about Traveller's focus on volume rather than mass. Which is a very peculiar thing, given that spaceships don't actually need a hull.


Okay, I ain't da best Traveller Grognard (whatever version and I am not a grognard in any case but............ How do you figure???????????????????

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