Why hydrogen?

[EDG]

However, the points on not being forced to to install a fuel puriification plant on even the smallest ship in order to tank water instead of H2 is still valid as is the additional point that doing so would require something that LBB ignored...Energy loss.
It takes energy to crack both ammonia and water to get at the stored H2 and that energy is a loss.

As a point, using unrefined fuel is nonsensical anyway - you can't just dump a mix of gases that contain hydrogen into a fusion reactor and expect it to work. At best, the ions of other elements that end up in the reactor screw up the fusion reaction and reduce its efficiency, and at worst the reaction just won't work.

So either all unrefined fuel that goes into the reactor has to go through some refinement (whether the ship officially has refinement plants or not), or ships without refinement plants just cannot use unrefined fuel, period.

 

[atpollard]

Understood about the "pocket"
However, the points on not being forced to to install a fuel puriification plant on even the smallest ship in order to tank water instead of H2 is still valid as is the additional point that doing so would require something that LBB ignored...Energy loss.
It takes energy to crack both ammonia and water to get at the stored H2 and that energy is a loss.

The chemical energy involved could be considered trivial in a milieu with working fusion. If you could spend a week cracking the storage medium... However, since the H has to be released in a few seconds, the power requirements become quite significant.

From previous versions of Traveller, the power output from a Starship power plant is STAGGERING. The 2 ton Power plant on a Type S Scout is able to produce 200 MW of continuous output while consuming only 0.038 cubic meters of LH2 per hour (CT values, other versions differ slightly). I'll leave it to someone with a better knowledge of chemistry to figure out how much Water could be cracked into H2 in 1 hour with 200 MWh of power, but I bet it is a lot.

I agree much of the jump fuel might NEED to be stored as LH2, but the fuel for the PP and a second jump could easily be stored as the more compact water, and 'Purified' as needed.

 

[Shiloh]

I'm pretty sure that separating off the pure hydrogen from a GG soup could be done with a minimal-energy fractionating column (just let it warm up *slowly*), but hydrogen produced by steam reforming with water would be easy to keep elementally pure; none of the other possible reaction products are nearly as volatile.

Does refined fuel have a higher proportion of heavy H-isotopes?

 

[EDG]

I'm pretty sure that separating off the pure hydrogen from a GG soup could be done with a minimal-energy fractionating column (just let it warm up *slowly*), but hydrogen produced by steam reforming with water would be easy to keep elementally pure; none of the other possible reaction products are nearly as volatile.

Sure, but that implies that powerplants have built-in refinement capabilities, which haven't been explicitly mentioned in canon. But they have to be there for them to use unrefined fuel.

Does refined fuel have a higher proportion of heavy H-isotopes?

I'd imagine it would. I think when I discussed this last time (on the old Avenger boards, I think the thread is gone now) I figured that refined fuel must be really good stuff, with more useful isotopes over and above what you'd get from just doing basic/implicit refinement on unrefined fuel.


More to the point though, are fusion plants for starships also big steam turbines? How does the fusion power get converted to electricity otherwise?

 

[Supergamera]

More to the point though, are fusion plants for starships also big steam turbines? How does the fusion power get converted to electricity otherwise?

If you're only converting a fraction of the input mass into the reactor into energy, you could run the heated discharge plasma through a power turbine, rather than rejecting heat to another medium. As the plasma is ionized, you may be able to make it more like a MHD turbine, and minimize the materials exposed to the plasma. While the overall efficiency may be modest, particularly if it's a simple cycle once-through operation, you're greatly reducing the parts count of the system.

Containment and power generation may also be aided by gravitics, which ties nicely into the evolution of gravitics and fusion power in Traveller.

By dispensing with any recycle operations or secondary power recovery, the starship P-Plant trades fuel efficiency for reliability.

 

[Klaus Kipling]

More to the point though, are fusion plants for starships also big steam turbines? How does the fusion power get converted to electricity otherwise?

If you're only converting a fraction of the input mass into the reactor into energy, you could run the heated discharge plasma through a power turbine, rather than rejecting heat to another medium. As the plasma is ionized, you may be able to make it more like a MHD turbine, and minimize the materials exposed to the plasma. While the overall efficiency may be modest, particularly if it's a simple cycle once-through operation, you're greatly reducing the parts count of the system.

Containment and power generation may also be aided by gravitics, which ties nicely into the evolution of gravitics and fusion power in Traveller.

By dispensing with any recycle operations or secondary power recovery, the starship P-Plant trades fuel efficiency for reliability.

Nice bit of handwavium rationalisation there! I'm going to use that...

 

[EDG]

That works better, I guess .

Hrm. I wonder if you could use the photons produced by the reaction to power something. Kinda like having uber solar cell type things in there to capture the photons and produce electricity?

 

[captainjack23]

I'm thinking that there's a statement in the Player's Guide PDF that if you go outside in J-space you're dead. rrNProc expunge dead no save no fate point. Dead. That seems like a fairly sudden thing to me. the hydrogen 'bubble' must be a bit more durable for some reason (I like the "plasma" idea) even if the crystaliron hulls might survive such destructive wear and tear for a whole week.

good point, but there are lots more ways to kill a person dead than simple disintergration -a significant enough change in some of the basic physics constants could easily kill a human DEAD much faster than it would dissolve hullmetal.

I always imagined it as being something that the unique nature of H2 would protect against - a difference in the interatomic binding force would have less effect on H, I Imagine than most other atoms -and would have profound effects on an electrochemical system like a human.....

 

[AKAramis]

That works better, I guess .

Hrm. I wonder if you could use the photons produced by the reaction to power something. Kinda like having uber solar cell type things in there to capture the photons and produce electricity?

that's one of the primary modes for current fusion research.

 

[Rikki Tikki Traveller]

Piezo-Electric cells perhaps?

 

[Shiloh]

I'm pretty sure that separating off the pure hydrogen from a GG soup...

Sure, but that implies that powerplants have built-in refinement capabilities, which haven't been explicitly mentioned in canon. But they have to be there for them to use unrefined fuel.

Not at all. Separating off the H is what fuel scoops do. You could even use a "simple" filter, H being such a magnificently small atom/molecule, instead of bringing the whole soup onboard and just tipping the non-H off as it pools...

Does refined fuel have a higher proportion of heavy H-isotopes?

I'd imagine it would. I think when I discussed this last time (on the old Avenger boards, I think the thread is gone now) I figured that refined fuel must be really good stuff, with more useful isotopes over and above what you'd get from just doing basic/implicit refinement on unrefined fuel.

Again, I think it's important to draw the distinction between feedstocks that the Fuel Processors can turn into actual 'useful stuff' and useful stuff (H) that can be *improved*.

More to the point though, are fusion plants for starships also big steam turbines? How does the fusion power get converted to electricity otherwise?

Good question. I'd be inclined to say there has to be some sort of thermal coupling, since the thermal energy of the grav-omak is what can be usefully captured. Pissing the plasma away to drive a turbine directly strikes me as so far from equilibrium as to be terribly wasteful.

 

[captainjack23]

We know that jump drives use (preferably refined) h2 for jump fuel, and that power plants use the same.

We know from this version of Traveller that most of the h2 used in jump is used to inflate the jump bubble.

But why h2?

This is just idle speculation, but could it be something to do with the fact that if you strip the electron from a hydrogen atom, you're left with a proton? Is this some useful handwavium we can use to embellish our MTU jump theories?

Actually, and this is just my own speculation, that may be sort of the case.


The unique thing about H atoms is exactly that - the nucleus is one proton, and nothing else....except for the much less frequent heavy isotopes with one and two neutrons, correct ? So, a cool solution would make the need for H2 fuel dependent on its unique properties.

So, how 'bout this. We know from the previous discussion that 1. potential fusion reactions like more heavy isotopes of hydrogen, and that 2. unrefined fuel has to be a lot cleaner than often supposed -ie you can't throw "any old gas involving hydrogen " in there and make it work(the "pull my finger" refuel, as my useless players call it...) . So, basic scooping has to largely result in mostly H2; what do the refineries do, and why is it that it takes much time at all ? Gas separation isn't wildly hard nowadays, and can't help but get easier.

Here's a thought: most of the job in refining fuel is enriching the powerplant fuel with heavy hydrogen from the jump bubble hydrogen. Unrefined fuel for the fusion plant is simply unenriched hydrogen, and possibly has minor contaminants; but mainly it is unenriched.

So we could stop there, but we can tie it to the jump bubble....

suppose then, that whatever jumpspace is, one of its dangerous qualities is that of supressing or at least degrading the strong nuclear force which binds protons and neutrons...thus causing an atomic nucleus from our world to blast apart -and even heavy hydrogen would shed neutrons like crazy. Single proton Hydrogen, however, doesn't have that problem.

So, the more the jump bubble is composed of single proton hydrogen, the better it works; the more complex atoms it contains, however, the more we get sudden bursts of protons and neutrons. This would be....bad.... in general for the ship and crew...and as the ship's jump bubble enters jumpspace, too many bursts could well disrupt the jump to the point of causing misjumping.

So. The refining process transfers the heavy hydrogen from the jump bubble fuel into the powerplant fuel (as well as minor filtering) ; the hydrogens unique ability to resist jumpspace is increased by the process that makes the powerplant fuel more effective. Talk about efficient dependency !

The nice thing about this, is that the unrefined fuel modifier is no longer caused by the fuel effecting the powerplant but rather the jump process itself. And the whole Jumpspace/jump thing is so vaguely defined as to cause far less problems than making assumptions about engineering or powerplants......

 

[Shiloh]

Actually, and this is just my own speculation, that may be sort of the case.

[snip]...the whole Jumpspace/jump thing is so vaguely defined as to cause far less problems than making assumptions about engineering or powerplants......

I like your thinking. And the easy ionisation of H means that the poor ickle electrons don't have to worry about J-space either.

One useful conclusion the sums earlier have shaken out of this discussion is that if you want to have enough fuel to jump twice, taking fuel for the second jump along as either methane or a methane clathrate (methane/water ice matrix) or even water will reduce the dTonnage needed for its transport, so long as you accept it's going to take some time to crack and purify the transport feedstock. Ditto for "maintenance" fuel, since the rate of demand for that is lower than the demand for "inflation hydrogen".

Splendid.

 

[Klaus Kipling]

Yeah, liking that Captain too.

And I like the fact those belters can cross those rifts using giant buckets of water in their holds for cracking/refining in deep space, rather than unlikely and most probably very dangerous inflatable L-hyd balloons.

 

[captainjack23]

Yeah, liking that Captain too.

And I like the fact those belters can cross those rifts using giant buckets of water in their holds for cracking/refining in deep space, rather than unlikely and most probably very dangerous inflatable L-hyd balloons.

The only real issue with moving the H2 as part of another compound is the mass issue - if the combined substance has much more mass than the stored hydrogen, for equal volumes of hydrogen, then it is a problem - assuming that mass matters for M drives.

I don't know the chemistry well enough to answer the question, though -any takers ?

One other, and this is occuring to me as I write, is that I always saw the jump bubble as needing to be "blown" very quickly - probably as the ship is entering Jspace. Starting from bound H might be a bit problematic -so one would have to have cracked it well beforehand -which does make for a storage problem. Perhaps those big H balloons ? Besides, how dangerous is H2 in the absence of other molecules ? Not very, I'd guess, if one is thinking Hindenberg - that reaction requires O2......

 

[Klaus Kipling]

If one is using the cargo bay to store balloons of H2, then it may very well come into contact with it's combustive partner, O2. Also, with lil' old H being so small, diffusion through any inflated membrane could be quite likely - let alone sharp objects.

 

[captainjack23]

If one is using the cargo bay to store balloons of H2, then it may very well come into contact with it's combustive partner, O2. Also, with lil' old H being so small, diffusion through any inflated membrane could be quite likely - let alone sharp objects.
________________
In the end, we're all dead.

That post meshes so well with your sig......

Yes, that is a point. I'd assumed that for sitting around an cracking H2 between jumps an exterior (ie outside the hull) would be sufficient. Still, one has to get the H2 into a position where the balloon won't count as displacement....and bygod, we are back into drop tank world....shudder.

 

[AKAramis]

given the recent development of monomolecular carbon sheeting, it's quite possible the balloons would not be hydrogen permeable.

 

[atpollard]

given the recent development of monomolecular carbon sheeting, it's quite possible the balloons would not be hydrogen permeable.

Wouldn't the H2 react with a Carbon Compound of any type?

 

[EDG]

Wouldn't the H2 react with a Carbon Compound of any type?

I don't think H2 is itself particularly reactive (not like a halogen like Chlorine or fluorine would be anyway). The problem with hydrogen and oxygen is that any kind of spark will ignite the combination and cause reactions, but I thought that in an otherwise inert environment they could just coexist together without reacting.