Water vs Hydrogen discussion

[aramis]

As Hans notes, the critical element in Traveller ship design isn't mass - it's volume.

The design ton isn't a mass ton, but a volume measurement.

Now, one thing is important to note: in TNE & T4, one designs gravitic and jump drives by volume as long as mass is less than 10 metric tons per displacement ton. A 10 ton mass of water in 1 Td (14 kL) of volume still carries 1.11 Td of hydrogen. And the duration on a TNE fusion plant is long enough that storage losses can be significant. A hydrogen rocket on the pad loses some 1% per week or more of its H2... Hydrogen, unless chemically bound, leaks through any container.

In CT, where it's PURE volume design, that 14 Metric Tons in 1Td (14 kL) is 1.555 metric tons of hydrogen per Td. Cut your tonnage for fuel by 1/3 by installiing a couple tons of FPP and small amount (1 day) of hydrogen ready tankage. For the Type S, it's not a savings... unless using bk2 drives. But for a 1500Td ship under Bk5 with even PP1... 1% per month is 15 Td. Instead install 10 of water, a 1 Td ready tank for Hydrogen, and a 3 Td TL15 minimum size FPP, and you've saved a ton.

The FPP approach can't be readily used for the first jump... the fuel is used in under 20min, and the FPP is 15% of the 8-hour tankage... 20 tons per 8 hours, or about 0.8 tons fuel per 3Td plant per 20 minutes... so you'd need
72Td of TL15 FPP to jump a scoutship... a negative savings of HUGE proportions.

 

[Dragoner]

Real world, it is mass not volume that is most important, c'est la vie..

With the volume for water argument of commercial shipping, I would say savings would be negligible. A big ship will ply it's route (and never do wilderness refueling, the risk assessment for that is horrific) refueling at it's regular stops, that is how 80%-90% of cargo will be shipped. They wouldn't accept any risk to the ship as that would be THE major money loser, the inefficiency of not carrying water pales by comparison in a business sense. Now speculative or FOB stuff like free traders do is different, but they would follow the big boys, just by architecture of ships. The easiest answer to Hans' post from a business perspective is to get a bigger ship, money is made in the margin, yes, if it becomes an issue, increase your load capacity seems the obvious answer. Time doesn't seem an issue to me trade wise, when a shipment of air/raft reaches it's destination would be a matter of procedure, you wouldn't want them too soon or too late and even under a perpetual or periodic inventory system, you balance the books once a month, if it takes longer it just carries over on the balance sheet.

I'm leery to think that the water for jumps wouldn't all have to be converted before jump and in tankage, so a huge volume of tankage would then be empty until needed? That seems to abrogate some of the consideration for volume right there. As per the tankage itself, I know typical loss today is 1%, though that is low tech, like how ancients would store volatiles like naptha in ceramics, which we would never do. We tank gasoline in cars in plain steel tanks of which they could not imagine. I believe I had read that maybe in Hard Times or one of the TNE books that people were still finding full tanks of fuel 10's of years later on boneyard worlds, so that supports an assumption that the storage tech has solved the sublimation issue of current storage.

 

[rancke]

With the volume for water argument of commercial shipping, I would say savings would be negligible. A big ship will ply it's route (and never do wilderness refueling, the risk assessment for that is horrific) refueling at it's regular stops, that is how 80%-90% of cargo will be shipped. They wouldn't accept any risk to the ship as that would be THE major money loser, the inefficiency of not carrying water pales by comparison in a business sense.

It's an unproven and extremely implausible assumption that a water tank and an electrolysis apparatus would present the slightest risk whatsoever. And if it doesn't, then a ton saved is an extra ton of revenue-generating cargo space.


Hans

 

[Enoki]

If volume is the issue then I would think that liquifying hydrogen and compressing it into the smallest volume possible would be the way to go. No volume taken up with anything but usable fuel. So what if the tanks are extremely heavy in design? Its volume that's important.....

 

[Enoki]

It's an unproven and extremely implausible assumption that a water tank and an electrolysis apparatus would present the slightest risk whatsoever. And if it doesn't, then a ton saved is an extra ton of revenue-generating cargo space.


Hans

The problem here is that you then have to include the space for the electrolysis equipment, piping etc., for it, a power supply for it and, tankage for the hydrogen produced. You can't realistically put it back in the tank you are syphoning the water from now can you? So, you would need tank space for the water, tank space for the hydrogen, space for the extraction equipment, piping etc.
Then there is the question of conversion rate. How long will it take the ship to process the water into fuel? That could be an issue on its own. If it took say 24 hours to make the water into hydrogen and the ship could make the jump point in eight then the ship sits for most of a day making fuel rather than being FTL with a commensurate later arrival date.

 

[Dragoner]

It's an unproven and extremely implausible assumption that a water tank and an electrolysis apparatus would present the slightest risk whatsoever. And if it doesn't, then a ton saved is an extra ton of revenue-generating cargo space.


Hans

It is purely logical, not implausible and a violation of a basic rule of engineering: don't do what you don't need to do. Complexity asks for failure and never do anything in a vehicle that you can do on the ground or somewhere else, makes it cheaper to separate processes as well, clearly. Ships also will probably deadhead on their route as well, so that ton might not be all that valuble; if you need the tonnage, increase the size, the real forecasting will be in sales, not shipping.

 

[rancke]

It is purely logical, not implausible and a violation of a basic rule of engineering: don't do what you don't need to do.

Unless there's a clear benefit to doing it.

Complexity asks for failure and never do anything in a vehicle that you can do on the ground or somewhere else, makes it cheaper to separate processes as well, clearly.

Lovely aphorism, but not actually proof of anything at all.

Ships also will probably deadhead on their route as well, so that ton might not be all that valuble; if you need the tonnage, increase the size, the real forecasting will be in sales, not shipping.

Increasing the size increases the cost. Businessmen have a real aversion to unneccessary expenses. It cuts into their profit margin.

(Battle of the aphorisms!)


Hans

 

[Dragoner]

The problem here is that you then have to include the space for the electrolysis equipment, piping etc., for it, a power supply for it and, tankage for the hydrogen produced. You can't realistically put it back in the tank you are syphoning the water from now can you? So, you would need tank space for the water, tank space for the hydrogen, space for the extraction equipment, piping etc.
Then there is the question of conversion rate. How long will it take the ship to process the water into fuel? That could be an issue on its own. If it took say 24 hours to make the water into hydrogen and the ship could make the jump point in eight then the ship sits for most of a day making fuel rather than being FTL with a commensurate later arrival date.

Also one has to think of what if you water system breaks down far away from a port and your ship has to go in for unexpected repairs, which could be a major disaster business-wise (leading to all sorts of nastiness such as breach of contract and competitors taking market share, loss of goodwill, etc.); then you would have to have on file a risk assessment with a contingency plan and the money set aside (not earning money) to cover it, then any extra savings could be gone with one fell swoop. Water could be relatively unstable as well by boiling and freezing easily which would require heavy tanks.

 

[rancke]

The problem here is that you then have to include the space for the electrolysis equipment, piping etc., for it, a power supply for it and, tankage for the hydrogen produced. You can't realistically put it back in the tank you are syphoning the water from now can you? So, you would need tank space for the water, tank space for the hydrogen, space for the extraction equipment, piping etc.

You feed the hydrogen you separate into the power plant as you separate it. It's high school science, not rocket science. If you're talking about jump fuel, you carry along fuel for a second jump as water instead of as L-Hyd. That means you have a big empty tank to put the hydrogen into.

Then there is the question of conversion rate. How long will it take the ship to process the water into fuel? That could be an issue on its own. If it took say 24 hours to make the water into hydrogen and the ship could make the jump point in eight then the ship sits for most of a day making fuel rather than being FTL with a commensurate later arrival date.

This technique would not be for ships that make single jumps, since you need the full tankage for one jump. Most ships won't need to do two consecutive jumps. Those who do would do it because such a double jump would save at least one jump. So the differenc ewould be between the hours it takes to process the water vs. the time it takes to make a whole extra jump (or more).

That kind of jumps is certainly not going to be common. But it would be an option for the rare situations where it would be an advantage (such as rift-crossing).

The power plant fuel type of savings would be useful for almost all ships, of course.


Hans

 

[Dragoner]

Unless there's a clear benefit to doing it.


Lovely aphorism, but not actually proof of anything at all.


Increasing the size increases the cost. Businessmen have a real aversion to unneccessary expenses. It cuts into their profit margin.

(Battle of the aphorisms!)


Hans

Costs don't cut into profit margins, per se, they are part of gross profits and cost benefit analysis has a risk assessment there, not to mention how costs work, you would do a ratio, but if you didn't have extra capacity and lost sales due to it, sales being the bigger money maker; shipping isn't as big a factor as sales, not at all. It is not an aphorism, you don't refine fuel in any vehicle, I can't think of any vehicle that actually does. Plus you are forgetting your extra tankage for water and hydrogen. There isn't any clear benefit.

 

[rancke]

Also one has to think of what if you water system breaks down far away from a port and your ship has to go in for unexpected repairs, which could be a major disaster business-wise (leading to all sorts of nastiness such as breach of contract and competitors taking market share, loss of goodwill, etc.); then you would have to have on file a risk assessment with a contingency plan and the money set aside (not earning money) to cover it, then any extra savings could be gone with one fell swoop. Water could be relatively unstable as well by boiling and freezing easily which would require heavy tanks.

It's generally the case that water is easier to handle than liquid hydrogen.


Hans

 

[rancke]

Costs don't cut into profit margins, per se, they are part of gross profits and cost benefit analysis has a risk assessment there, not to mention how costs work, you would do a ratio, but if you didn't have extra capacity and lost sales due to it, sales being the bigger money maker; shipping isn't as big a factor as sales, not at all. It is not an aphorism, you don't refine fuel in any vehicle, I can't think of any vehicle that actually does. Plus you are forgetting your extra tankage for water and hydrogen. There isn't any clear benefit.

Yes there is. More cargo space equals greater earning potential.

What you do in trucks and steamers is not evidence for what you would do in a fusion-powered starship.


Hans

 

[Dragoner]

You feed the hydrogen you separate into the power plant as you separate it.

Where is it written you can do this? AFAIK it's refined into tankage before use is how Traveller works (and real world).

That means you have a big empty tank to put the hydrogen into.

...and risk contaminating your fuel tanks, reactor or J-drive.

 

[Dragoner]

It's generally the case that water is easier to handle than liquid hydrogen.


Hans

in outer space?

 

[Dragoner]

Yes there is. More cargo space equals greater earning potential.

What you do in trucks and steamers is not evidence for what you would do in a fusion-powered starship.


Hans

Which is why you would go with the logical route of getting a bigger ship. Traveller says to go with real world examples, which Traveller does, eg containerized freight systems etc. (not steamers). Sales would dominate over shipping though, otherwise the economics don't work.

 

[rancke]

Which is why you would go with the logical route of getting a bigger ship.

A bigger ship costs more money.

Traveller says to go with real world examples, which Traveller does, eg containerized freight systems etc. (not steamers). Sales would dominate over shipping though, otherwise the economics don't work.

Real world examples of starships? Trucks and steamers don't refine fuel on the go because that wouldn't be an advantage for them. Refining fuel from water would be an advantage for starships. It would result in more cargo space for the same investment, resulting in greater earning potential for the same investment.


Hans

 

[rancke]

It's generally the case that water is easier to handle than liquid hydrogen.

In outer space?

Any place where the temperature is conducive to human survival. That would include starships in outer space.

(Actually, I suspect that water is easier to handle than L-Hyd at any temperature).


Hans

 

[aramis]

It's an unproven and extremely implausible assumption that a water tank and an electrolysis apparatus would present the slightest risk whatsoever. And if it doesn't, then a ton saved is an extra ton of revenue-generating cargo space.


Hans

More over, the stuff coming out of the FPP is considered refined fuel. HG p.27.

 

[aramis]

You feed the hydrogen you separate into the power plant as you separate it. It's high school science, not rocket science. If you're talking about jump fuel, you carry along fuel for a second jump as water instead of as L-Hyd. That means you have a big empty tank to put the hydrogen into.


This technique would not be for ships that make single jumps, since you need the full tankage for one jump. Most ships won't need to do two consecutive jumps. Those who do would do it because such a double jump would save at least one jump. So the differenc ewould be between the hours it takes to process the water vs. the time it takes to make a whole extra jump (or more).

That kind of jumps is certainly not going to be common. But it would be an option for the rare situations where it would be an advantage (such as rift-crossing).

The power plant fuel type of savings would be useful for almost all ships, of course.


Hans

Hourly rate for a 3Td TL 15 FPP
3=0.15*X
3/0.15=0.15*X/0.15
3/0.15=X
20=X
which means 6 1/3 Td per 8 hours per Td of FPP.
Which means 19/24 Td per hour per 3 Td of FPP.

It also means the minimum 3 Td FPP processes 57/24=2 3/8 Td per hour.

Fusion uses 1Td fuel per Td of plant per 30 days. 30 days * 24 hours is 720 hours; that's 1/720 Td per ton of plant per hour. A minimum 3Td TL 15 FPP can thus feed a 1710 Td PP as needed. Anything smaller than that is going to leave leftover capacity for refining the Jump Fuel.

Given 160 hours, that's 20 units of 8-hr time, for 400Td converted per 3Td of FPP in jump. For 400 Td fuel out, water is going to save 1/9 the fuel volume, or 36 Td, but lose 3 Td to the FPP. Which means 36 Td saved for that second jump's 400Td fuel.

The minimums are why H2 is used preferentially to H2O, Hans. You don't save enough on anything not using 400Td per jump, and really, Only 2J1 and maybe 2J2 is financially viable without changing the prices stupidly high. It's space-viable for about 10Td PP fuel at TL15. It's financially viable at about 15 tons PP Fuel, as that gets an extra ton per trip or more, and the FPP is only Cr30K...

 

[Dragoner]

A bigger ship costs more money.

It takes money to make money

Real world examples of starships?

Of course, you mean you don't have starships?

What you are talking about is Transportation and Logistics, it is actually a business specialty, the business dept offers degrees in it.

Trucks and steamers don't refine fuel on the go because that wouldn't be an advantage for them. Refining fuel from water would be an advantage for starships. It would result in more cargo space for the same investment, resulting in greater earning potential for the same investment.

Steamer is a funny word in english, unless you want to be directed to the Ohio division, probably best not use it. I would not mind seeing how you are figuring your numbers. AFAIK, shipping companies all have surplus capacity (and do not figure on capacity lost as much as capacity carried, which is amortized by contract and across a fleet and time), have to, for ships that have to go in to routine maintenance, larger sales, contingency for a lost ship, between sales and acquisition of new ships after the depreciated ships are sold, etc. (for example a shipping company that needed 100 type R's would probably have 5-10% tonnage extra in whole ships to cover various shortfalls). Business is risk averse, a dual stage fuel system would add a 50% failure rate to a standard system and as far as I know, ships like the Type R do not have purification plants. Makes sense as the ships would fuel right after leaving their slip (Fuel Expense, Accounts Payable) then Jump to destination. Thus you wouldn't have any costs, documentation or scheduled maintenance on purification plants because you don't need them, or even want them as wilderness refueling is inefficient on a large scale.