Water vs Hydrogen discussion

[rancke]

1) Everything must be done in game terms, much of it is a game device for sure...

And that's the rub. When you tell your players (or at least when I tell my players) that things don't actually work like that, but we're pretending they do for ease of play, they get that. When you tell them that things actually work the way the rules say, they often come up with loopholes to exploit. It's fine to stick to the rules as long as you stick to the same level of abstraction as the rules, but players, bless their devious little minds, have a tendency to look for exploitable advantages.

...but then again the Free Trader and Speculative Market model for economics are game devices as well, because they don't work otherwise.

They don't work unless we pretend that they work. Which works fine if you want to play the Merchant Game. It sucks if your players want to, say, bribe a broker to sell them a cargo that wasn't rolled up in the regular and you try to tell them that they can't even try because the rules don't allow it.

OTOH, the rules do allow you to sell 61 multi-million credit computers with a 300% profit on a world with a population level of 4, if the dice roll that way ...

Which in the game, it does not differeciate between PP fuel and JD fuel, it only says "use of unrefined", which implies either. Without the purifier, the misjump chance is there.

The rules don't differentiate. But is there any logical reason why you cannot differentiate between PP fuel and JD fuel? There is not. Which perfectly illustrates the fallacy of treating the rules as expressions of universal truths rather than simplifications of a complex reality for the sake of playability.

2) Hans has this tendancy to say "implausible" after talking about starships, fusion power and jump drives; which are all implausible.

Actually, I tend to use "implausible" when talking about fusion power, which is not at all implausible and which we have ways to calculate reasonable expectations for. I also tend to look askance at game rules that give illogical or contradictory results in different contexts.

An implied assumtion of a starship is that every task is complex, maybe easier for higher tech, but that doesn't change the complexity of the task.

Actually it does. Improved technology does simplify tasks. That's the whole point of technology.

So no simple water tanks, tubing, TL5, etc.

No, indeed. It's TL15 water tanks, tubing, valves, etc. This is something that could be done with TL5 equipment in a pinch. How much easier must it be to do at TL15?

Traveller doesn't take into account pressure, water reacts differently at different pressure, boils quicker for example.

And equipment to deal with water aboard starships would be designed to cope with the idiosyncracies of water aboard spaceships.

Incidentally, you're quite right that the Traveller rules don't take pressure into account. Does that mean that pressure isn't a factor in the Traveller universe? I didn't think so. So the rules are not a complete and accurate picture of the Traveller universe, are they?


Hans

 

[Dragoner]

And that's the rub. When you tell your players (or at least when I tell my players) that things don't actually work like that, but we're pretending they do for ease of play, they get that. When you tell them that things actually work the way the rules say, they often come up with loopholes to exploit. It's fine to stick to the rules as long as you stick to the same level of abstraction as the rules, but players, bless their devious little minds, have a tendency to look for exploitable advantages.


They don't work unless we pretend that they work. Which works fine if you want to play the Merchant Game. It sucks if your players want to, say, bribe a broker to sell them a cargo that wasn't rolled up in the regular and you try to tell them that they can't even try because the rules don't allow it.

OTOH, the rules do allow you to sell 61 multi-million credit computers with a 300% profit on a world with a population level of 4, if the dice roll that way ...


The rules don't differentiate. But is there any logical reason why you cannot differentiate between PP fuel and JD fuel? There is not. Which perfectly illustrates the fallacy of treating the rules as expressions of universal truths rather than simplifications of a complex reality for the sake of playability.


Actually, I tend to use "implausible" when talking about fusion power, which is not at all implausible and which we have ways to calculate reasonable expectations for. I also tend to look askance at game rules that give illogical or contradictory results in different contexts.


Actually it does. Improved technology does simplify tasks. That's the whole point of technology.


No, indeed. It's TL15 water tanks, tubing, valves, etc. This is something that could be done with TL5 equipment in a pinch. How much easier must it be to do at TL15?


And equipment to deal with water aboard starships would be designed to cope with the idiosyncracies of water aboard spaceships.

Incidentally, you're quite right that the Traveller rules don't take pressure into account. Does that mean that pressure isn't a factor in the Traveller universe? I didn't think so. So the rules are not a complete and accurate picture of the Traveller universe, are they?


Hans

On technology, saying something is easier, does not necessarily reduce complexity, for example: the use of carbide tipped tools makes it easier to cut steel, however it is more complex when you factor in the making of the carbide tipped tool. Thus ease of use does not equal less complexity.

Personally, I don't mind players finding loopholes and making me think, that is part of the fun of the game. However one thing must be said is that if you want to modify the rules to use water, you can, it's that simple.

Why are fusion reactors and jump drives using the same fuel? Besides the simplicity factor, it seems that there is some sort of connection between power and jump, and power, seems to be based off of electricity, eg you can jump if your bg has filled your capacitors. Electricity is like water, so one can say maybe the use of unrefined fuel interrupts the pressure or flow of power.

While the rules don't provide an accurate picture maybe, wandering too far from the path and you are at the volume vs mass argument, which hydrogen wins, iirc. The rules are just a guide and they will be bent or broken, but without baseline assumptions, we are lost.

 

[rancke]

On technology, saying something is easier, does not necessarily reduce complexity, for example: the use of carbide tipped tools makes it easier to cut steel, however it is more complex when you factor in the making of the carbide tipped tool. Thus ease of use does not equal less complexity.

I wouldn't factor in the making of the carbide tipped tool. I'd just go down to the hardware store and buy it, then enjoy the increased simplicity of steel cutting. Similarly, I don't factor in the making of the TL15 water separator system. I'd just buy one, have it installed, and enjoy this simple and safe way of carrying power plant fuel at reduced volume.

(Note that I'm not saying that the canonical shipbuilding rules don't imply that there's some reason why using water for storage doesn't work. There's just no plausible reason known why this would be the case.)


Hans

 

[atpollard]

3) Oxygen is highly corrosive as well.

True, but Hydrogen is the most corrosive element, the atoms are small enough to slip thriough any possible container, and it seriously weakens whatever it is placed in over time.

Explosion is a layman's term, it is a chemical reaction,

but appropriate for describing the chemical reaction of pumping LH2 into a tank 1/3 full of LOX.

yes one just burns hydrogen to create water, it is a simple process, containment shouldn't be an issue if one is also containing and shielding a fusion reaction. One reason the scientist I was speaking with said they were bring only Liquid Hydrogen to Mars was that it could be used in simple processes, such as to make water.

3) The black box falls outside the rules, it has to be a fpp.

Converting methane and ammonia to 'refined' LH2 is significantly more complex of a device than a simple combustion chamber. I simply described it as a black box to avoid exploring the bunny trails of whether combustion would be better than a fuel cell/catalytic process. It is simply an acknowledement that the system described wil be more complex than just pumping LH2 into a tank 1/3 full of LOX. Clearly a simple combustion chamber (or fuel cell) would not have a minimum size of 42 cubic meters at TL 15 and 140 cubic meters at TL 8.

4) It is the Jump Drive fuel tankage that I am thinking about, if you are already using the tankage, the actual rate begins to fall, so 33% doesn't become enough of a savings, if it was 300%, then of course no doubt. Critical path engineering says to eliminate steps in your flowchart, which if no fpp, no use of water and just hydrogen, saves on complexity (esp infrastructural costs outside the ship), then would it be used?

For Jump Drives, fuel volume is a very big deal. A 100 ton jump-2 (x2) ship would require 20 tons of fuel per jump (40 tons total) which is 40% of the volume of the ship! Storing 20 tons of LH2 and 12 tons of refined water (Refined LH2 plus molecular O2) for the second jump frees up 8 tons of space ... 8% of the ship! This savings simply scales with the ship. A 1000 ton J2x2 ship would save 8% (80 tons) of space by storing the second jump of LH2 as water.

With a 3 dTon Purification Plant, I don't need refined water as the storage medium. The effluent from a septic tank will work just as well.



As an aside, Traveller doesn't compare well with real Mars missions because it has magic power plants that create virtually unlimited free electricity and magic reactionless drives that need no reaction mass. The real world is constrained to solar of fission power and limited chemical reaction drives. The dynamics are Apples and Oranges to each other.

 

[rancke]

For Jump Drives, fuel volume is a very big deal. A 100 ton jump-2 (x2) ship would require 20 tons of fuel per jump (40 tons total) which is 40% of the volume of the ship! Storing 20 tons of LH2 and 12 tons of refined water (Refined LH2 plus molecular O2) for the second jump frees up 8 tons of space ... 8% of the ship!

And 8% of the ship would be 20% or 25% or more of the cargo space. However, I'm not sure that such a ship would be cheaper than a jump-4 ship. A regular J2 ship doing two jumps with a source of fuel at the midpoint is cheaper than jump-4, but one with 32% fuel tanks instead of 20% might not be.

Of course, if you don't have jump-4 ships and don't have a convenient fuel source at the mid-point, carrying along the second load in the form of water is a definite (and lucrative) no-brainer.

Or it would be if it wasn't for the Mysterious Mishaps that inexplicably strike all ships that carry hydrogen in the form of water. Or is it the Imperial edict that prohibits any such reprehensible anti-Imperium activity?


Hans

 

[atpollard]

(Note that I'm not saying that the canonical shipbuilding rules don't imply that there's some reason why using water for storage doesn't work. There's just no plausible reason known why this would be the case.)
Hans

Wouldn't ammonia, methane or liquid hydrocarbons be even better than water? (I mean with a full 3dT purifier rather than a simple water cracker).

 

[atpollard]

Or it would be if it wasn't for the Mysterious Mishaps that inexplicably strike all ships that carry hydrogen in the form of water. Or is it the Imperial edict that prohibits any such reprehensible anti-Imperium activity?

Hans

Must be related to Gravitics and Psionics some how.

 

[rancke]

Wouldn't ammonia, methane or liquid hydrocarbons be even better than water? (I mean with a full 3dT purifier rather than a simple water cracker).

The rules likewise imply that those substances won't work either.

Sure, they'd work better and may be used in preferrence. I believe the improvenment is marginal and that they are a lot nastier than water, but the same arguments I've made for water might be used for them.

I believe they'd be more expensive than tap water, but maybe they're viable. I do know that I'd reject the argument "Water is too dangerous to handle safely" (because I know how dangerous it is to handle water) whereas I wouldn't reject the argument "Ammonia/methane/liquid hydrocarbons are too dangerous to handle safely" (because I imagine that it's dangerous to handle), but that could be mere vulgar ignorance -- or prejudice against ammonia and methane and liquid hydrocarbons.


Hans

 

[Dragoner]

I wouldn't factor in the making of the carbide tipped tool. I'd just go down to the hardware store and buy it, then enjoy the increased simplicity of steel cutting. Similarly, I don't factor in the making of the TL15 water separator system. I'd just buy one, have it installed, and enjoy this simple and safe way of carrying power plant fuel at reduced volume.

(Note that I'm not saying that the canonical shipbuilding rules don't imply that there's some reason why using water for storage doesn't work. There's just no plausible reason known why this would be the case.)


Hans

Fine but do you understand the concept? It is why what may seem cheaper and easier on the surface, isn't. Another concept you are using, efficiency (there is a whole engineering iceberg here), is also deceptive, for example: the automobile engine is around 18% efficient. So why use it to do so much work (and it will be continued to be used until the fuel becomes too expensive)? Because of ease of use, infrastructure, risks, hazards and a thousand other reasons. It is only implausible to you because you aren't thinking like an engineer. Take the handling of toxic and volatile substance you said you were afraid of, but how often do you do it? Fairly often if you are like me and have to go fill your auto with petrol at the station every week. You just learn the protocols and it's fine. But without an actual cost comparison and extra space isn't guaranteed income, the cost benefit relationship remains undefined.

 

[Dragoner]

True, but Hydrogen is the most corrosive element, the atoms are small enough to slip thriough any possible container, and it seriously weakens whatever it is placed in over time.


but appropriate for describing the chemical reaction of pumping LH2 into a tank 1/3 full of LOX.


Converting methane and ammonia to 'refined' LH2 is significantly more complex of a device than a simple combustion chamber. I simply described it as a black box to avoid exploring the bunny trails of whether combustion would be better than a fuel cell/catalytic process. It is simply an acknowledement that the system described wil be more complex than just pumping LH2 into a tank 1/3 full of LOX. Clearly a simple combustion chamber (or fuel cell) would not have a minimum size of 42 cubic meters at TL 15 and 140 cubic meters at TL 8.


For Jump Drives, fuel volume is a very big deal. A 100 ton jump-2 (x2) ship would require 20 tons of fuel per jump (40 tons total) which is 40% of the volume of the ship! Storing 20 tons of LH2 and 12 tons of refined water (Refined LH2 plus molecular O2) for the second jump frees up 8 tons of space ... 8% of the ship! This savings simply scales with the ship. A 1000 ton J2x2 ship would save 8% (80 tons) of space by storing the second jump of LH2 as water.

With a 3 dTon Purification Plant, I don't need refined water as the storage medium. The effluent from a septic tank will work just as well.



As an aside, Traveller doesn't compare well with real Mars missions because it has magic power plants that create virtually unlimited free electricity and magic reactionless drives that need no reaction mass. The real world is constrained to solar of fission power and limited chemical reaction drives. The dynamics are Apples and Oranges to each other.

Hydrogen storage is better in the future, this is implied in it's use as a fuel. Say through some impermeable, inert, closed cell super space age polymer inner tank coating on sale from imperial ronco.

I am just saying no black boxes in order that we stay within the framework of the rules.

However, between now and the far future, the same physics still apply, so the mars mission does have some relevance, if as just a baseline to how things have moved on. Traveller has overcome the limitation of physics, not abrogated them.

Interesting stuff on the jump drive tankage, but it seems the tankage really falls off with the use of 1xJn ship, which are the standard design, not 2xJn; with that the saving becomes negligible. You would still need the 20tons J fuel and whatever minor amount of pp fuel and save with not having a fpp. However if you were going on a long journey and you had say the jump ship from supp 8, you could just grab a huge chunk of ice in the cargo net.

 

[aramis]

Dragoner: you've come in with a rather unpleasant approach - apparently seeking a pat on the back and then snarking when it's pointed out that neither the game nor the universe support that idea.

 

[Dragoner]

Huh.

I don't feel as I am doing either, just discussing the topic.

 

[aramis]

Huh.

I don't feel as I am doing either, just discussing the topic.

THen you need to seriously reevaluate your posting style, because that's how it looks.

 

[Dragoner]

THen you need to seriously reevaluate your posting style, because that's how it looks.

Well, this is just kind of out of left field...

Sorry about that if you feel offended, that is not my intention.

 

[McPerth]

IMHO, most of the discusion about carrying fuel (either PP fuel or spare fuel for a second jump) in form of water come from a simplification CT made in order to make ship designing easier (and so more playable): ignoring mass in favor of displacement (volume).

Also IMHO, that doesn't mean mass don't matter, just that is left out of the rules for sake of simplicity. Of course, if you put back mass in the equation, the issue takes another meaning. I guess this is why most (if not all) cannon sources state LHyd as fuel, and no water (while there's no discusion the same amount of volume can hold more Hyd in form of water than in form of LHyd). If so, it's undeniable taking the fuel as water would affect maneuver capability of the ship, as it would multiply the mass of fuel by a factor of 14.

I take as given ships may crack water into H2 and O2 (at least those capable of wilderness refueling), as they can refuel from water.

All this said, I still see one place where carrying fuel in form of water may have a true advantage, as maneuver is not as important as jump and fuel carried: tankers.

If a tanker may carry 1.55... metric tons of hydrogen in 1 dton (1/9 of water weight is hydrogen, so 14 metric tons of water will give 1.55... metric tons of Hydrogen) , its fuel carrying capability is sigificantly increased, and the fact that its maneuver capability is impaired by that may be more than offset by this advantage in its primary mission (carrying large amounts of fuel), needing only 2 tankers where you'd need 3 if carrying LHyd.

Of course that may slow a little the refuelling of the fleet from tankers (though if they cracked the water while in jumpspace, holding the fuel created in their, now empty, own fuel tanks, that slowing may be minimized, as well as if the same ships it intends to refuel may help in the cracking), but when the tankers need is due to lack of fuel (empty hexes or waterless systems with no GG) instrad of quick refuelling, I see it as a feasible option.

 

[BytePro]

IMHO, most of the discussion about carrying fuel (either PP fuel or spare fuel for a second jump) in form of water come from a simplification CT made in order to make ship designing easier (and so more playable): ignoring mass in favor of displacement (volume).

Also IMHO, that doesn't mean mass don't matter, just that is left out of the rules for sake of simplicity. Of course, if you put back mass in the equation, the issue takes another meaning. I guess this is why most (if not all) cannon sources state LHyd as fuel, and no water (while there's no discussion the same amount of volume can hold more Hyd in form of water than in form of LHyd). If so, it's undeniable taking the fuel as water would affect maneuver capability of the ship, as it would multiply the mass of fuel by a factor of 14.
...

Then what of cargo? o:

Assuming the mechanics are just an abstraction doesn't work. The simplification for design and playing is mimicked by the nature of the M-Drive. Notably it is gravitic and that provides a 'justification' for mass being ignored. As any 'type' of maneuver drive could have been stated, I think this was a quite intentional choice to match in-game tech with simple mechanics.

Either all RW physics is thrown out the window - or one assumes either gravitic and/or inertial mass is changed. If both aren't changed (per an earlier post) - then the Theory of General Relativity is thrown out (which doesn't have to be the case otherwise - jump can co-exist with GR).

Three key points:

#1 - Changing gravitational and inertial mass is consistent with the Travel formulas which ignore gravity.

#2 - Changing inertial mass support the lack of additional energy requirements regardless the amount of maneuvering by reducing energy required for acceleration. Of course, this is because it also breaks the conservation of energy laws as we know them. .

#3 - Changing inertial mass also allows for Traveller's long duration high G acceleration.​

Just changing gravitational mass does not do these last two. Plus, as alluded to above, only changing gravitational mass and not inertial, undermines the fundamental principle (Equivalence Principle) General Relativity is based on.

Another option is to change/generate gravitons or the space-time curvature. But if this doesn't affect inertial mass, then F= ma is not affected, and #3 is a problem (though #2 could be explained by graviton/space time curvature changes).

Of course, while gravitics changing inertial and gravitational mass works quite well for most of the mechanics in CT and MgT and perhaps others (including air-rafts and supporting scaling down energy requirements for personal grav devices), there is an inconsistency. The combat rules in the original books with the planetary templates. Fortunately, there is a technical out. The text states that gravity 'can affect movement' and 'gravity may alter that vector'. Interpreted literally, this text allows a conditional choice to disable the aspect of gravitic drives that negates the force of gravity while still applying the acceleration from gravitics (equivalent to thrust). This is my choice to reconcile two otherwise conflicting aspects of the RAW. The author's original intent regarding combat was probably different, but the ambiguity of English and the text as written, allows for the alternate interpretation to be equally valid.

[Note: I only refer to CT and MgT and then mostly the main books.]

...
All this said, I still see one place where carrying fuel in form of water may have a true advantage, as maneuver is not as important as jump and fuel carried: tankers.

Yep.

It is also technically easier and cheaper to 'obtain' water rather than L-Hyd on most habitable worlds in addition to availability regardless of local tech - barring setting 'legalities', of course.

I've always stuck with L-Hyd though - its risks and extremely low temps provide good sci-fi RP fodder. And there is one perhaps overlooked technical down side to water - in space it must be kept warm (though it them makes a nice heat sink) or the expansion/contraction cycles accommodated (not overly hard, but its there).

 

[Enoki]

The other issue I see here is that there would have to be substancial differences in design of the tankage, piping, etc., between water and liquid hydrogen.

For example, the piping would have to have differing bend radii and possibly different materials in use between Lhyd and water. The tanks themselves would likely have to be different too. An Lhyd tank would have to be a dewer flask of some sort while a water tank could be a bladder. The water tank would require a far more substancial structure to support it than the Lhyd tank simply due to the differences in mass present.

Pipe lagging (insulation) would have to be different as would the standard for things like valves. Hydrogen leaks would be far more dangerous than water leaks for example.

I would suspect that there would be huge differences overall between the two in terms of physically engineering the systems. That could and probably would make a dual system bulky, complex and, expensive.

 

[atpollard]

Actually, LH2 can be stored in a bladder in the cargo hold that colapses down when not needed (from one of the early rules - CT or MT). So Traveller has the material tech issues resolved ... just slather on another coat of unobtainium.

 

[BytePro]

Practically speaking, water is probably the more logical long duration fuel source for Traveller style fusion. Frozen, one can even ignore sloshing. However, from a Sci-Fi perspective, L-Hyd is just so much cooler (pun intended )...

In the 80's I added the concept of 'in-orbit' fuel stations in the vicinity of high ports which are 'water asteroids' towed into nearby orbits. Suppose this is one step from active 'fuel tankers' (though the asteriods have no jump drives or substantial M-Drives).

IMTU, refined P.P. L-Hyd requires a higher than normal ratio of Deuterium. This makes refining water a process that requires more than one-to-one tonnage of water to L-Hyd. In other words, to 'top off' the tanks requires the ship to process water on site and only retain the refined L-Hyd. Of course, for storage, one could simply use semi-heavy water in such a scenario.

With Mongoose Traveller, at least, a major in-game justification for using L-Hyd is the Jump fuel requirements. MgT has jump fuel used up quickly in creating the 'jump bubble', which probably means refining is not an option. However, I don't think this is the case in CT and maybe the jump-grid versions, though, and personally, I don't use the 'jump bubble' approach (finding it extremely flawed in concept).

 

[saundby]

My experience with actual rockets is that once a particular approach has been proven, the homework done, and some operational experience gained, it is resistant to displacement even by theoretically "better" approaches to solving the same problem. Part of it is that the practical issues are already manageable. Part is that in the course of getting to the point of being even minimally proven a certain amount of infrastructure has been established. And part is simply mindshare among people who have more interest in applications than in systems development--they just want "good enough" so that they can get the job done.

It's also my RL experience that theoretical considerations of technological efficiencies are below the noise level of actual operational efficiencies with working systems. There are a lot more factors in operations than get considered in even very detailed theoretical analyses.

What this means is that a stronger case for either form of storage can be made based on technical history and social/political factors than on pure technical factors. A case can be made either way.

If the right families/proto-megacorps back and fund LH2 over water, LH2 is what will become the dominant form--more probably because the patents and contracts were held by the right people than for technical reasons--the technology need only be sufficiently good, not superlatively good compared to its competitors. The same could be said for water storage systems.

Speaking as someone who's done propulsion R&D, either one presents a number of interesting problems.

Speaking as someone who's been met at the door of the office to be told that their project (and funding) is on hold for a year while competing power interests hold a pissing match, I know the theoretical aspects of the technology isn't what decides what goes into operation.

Now I'm going to prevent my techie side from going into the practical matter of mixing LOX with LH2. It's very interesting, and doesn't work quite as one would suppose at first glance. Have I mentioned the time we put Diborane and ClF5 together and they didn't go bang? It was a very educational experience in propellant handling...