HG p. 44 Metal hydride storage driving me nuttier

[snrdg121408]

Evening AndrewW,

Yep, adding the extra fuel is what I did in the design I did so long ago. The extra fuel provided an extra week to the motherships duration. I agree that the small craft probably have full tanks while in storage. The small problem occurs when they need fuel as being in operation. I think this is probably a smaller issue for civilian craft, but naval units deploying fighters, shuttles, and the ground force vehicles will need to be refuelled between operation.

Of course the better option is probably leave the rules as is.

Could just add extra fuel storage if you need to store more fuel for small craft. They can have full tanks of their own while stored.

 

[snrdg121408]

Evening Ishmal,

Thank you for the reply and suggestions on alternate fuels. Metal hydride is an alternate method that allows the fuel to be stored as a solid instead of a liquid. Storing the hydrogen, per HG p. 44, as metal hydride reduces the chance of an explosion if a tank leaks into the inhabited spaces of the ship. (Submarine slang "The people tank;-)".)

Anhydrous ammonia mentioned here is still being stored in liquid form. Can Anhydrous ammonia be stored as a solid?

Using another type of fuel either to run a power plant or the maneuver drive endangers the crew and passageners in other ways than the explosive nature of hydrogen. One of the dangers is most of the fuels know today and mentioned here is that many of them aer toxic.

I thinking that I'll stick with the rules as written.

instead of metal hydrides to store hydrogen, why not use liquid anhydrous ammonia?
you can get 105Kgs of hydrogen per cubic meter instead of only 71Kg's for liquid hydrogen. ( nearly half again as much )
We already know how to handle it in fairly large bits of infrastructure and its not nearly as difficult to handle as liquid hydrogen although it is toxic.
It IS more massive though... but not a problem for Trav ships that ignore mass in design sequences... but something to remember when figuring mass in FFS1 type design sequences ( .625Kg/m^3 , or about 8.8 times the density of liquid H2 )
for us noodniks that prefer reaction drives, most of it becomes reaction mass.

The relatively small amounts of hydrogen needed for actual fusion can be extracted using catalysts
We are already working on hydrogen fuel cells that run on ammonia

 

[snrdg121408]

Evening EDG,

From allmeasures.com 14 m^3 of hydrogen stored at 0 degrees centigrade has a mass of 1.2586 kg. Both T4 and GT also provides a mass for liquid hydrogen.

Best answer Ive heard is that the equipment that produces a ship's gravity somehow diverts the hydrogen away from the ship's interior.

Hm. I wonder how much hydrogen actually is in 1 displacement ton. TNE is the only version that I can recall that assigns a mass to liquid hydrogen (FF&S p63) - it says that it's 0.07 metric tons per cubic metre. So that's 70 kg/m³ - which sounds a lot but it's really 0.07 kg per litre. BUT... that assumes it's stored cryogenically at 20K (see http://en.wikipedia.org/wiki/Liquid_hydrogen ).

So... can you store even more hydrogen if you compress it more? How much can you compress it by before it turns into weird liquid metallic or solid metallic phases? (Hrm, seems that we're talking about gigapascals of pressure (hundreds of thousands of atm) before we get even to liquid metallic phases, so that's probably not going to happen in a spaceship!).

Still, I'm sure it can be compressed further by several times in order to store more hydrogen in the ship (yummy - pressurised cryogenic liquid hydrogen... that's probably about as dangerous as it gets!). Then you can fit twice, or thrice, or four times or more times the amount of fuel in the ship. It's not like Traveller generally cares about the mass of the ship, does it.

That said, liquid hydrogen is insane anyway - as soon as you got hit in combat and the fuel tanks breached inside the ship, they'd mix with the oxygen therein and then *boom*.

 

[snrdg121408]

Magic works too. I like the idea Gaidheal.

We have magic storage for the liquid hydrogen, rendering it inert! :¬)

 

[Gaidheal]

Umm, just a point; 0 degrees C is not very cold at all and certainly not a worthwhile temp to cool H to, the figures EDG listed are 20 Kelvins which is pretty close to "as cold as you can get for all practical purposes", 0 Kelvins being "as cold as anything can ever be, end of".

[edit] Freezing point of water (0 degrees Celsius) is 273 K, for reference and I do realize that "cold" is relative and even a few hundred C is at the bottom end of things when compared to objects like stars, planets, etc, etc.

 

[EDG]

And I should point out that hydrogen apparently freezes at 14K and boils at 20K (at 1 atm pressure), so there's not much of a "window of liquidity" there.

I note that the wiki article at least says that to make liquid hydrogen you also have to pressurise it. So it is in fact pressurised in the fuel tanks already - though there presumably is leeway to compress it further so you can potentially pack twice the amount of hydrogen in the tanks (or more) while keeping it in a liquid phase.

 

[snrdg121408]

Evening Gailheal,

Thank you for the detail on liquid hydrogen and the temperatures. I went back to all measure, http://www.allmeasures.com , which has two hydrogen listing one at 0 degrees C and the other just as hydrogen. Both show that hydrogen has a density of 0.0889 kg/m^3. Unfortunately, the site doesn't have a way to calculate using temperature that I can find.

Drat, another idea that fell short;-).

Umm, just a point; 0 degrees C is not very cold at all and certainly not a worthwhile temp to cool H to, the figures EDG listed are 20 Kelvins which is pretty close to "as cold as you can get for all practical purposes", 0 Kelvins being "as cold as anything can ever be, end of".

[edit] Freezing point of water (0 degrees Celsius) is 273 K, for reference and I do realize that "cold" is relative and even a few hundred C is at the bottom end of things when compared to objects like stars, planets, etc, etc.

 

[snrdg121408]

Hello EDG,

Thank you too for the more detailed information.

And I should point out that hydrogen apparently freezes at 14K and boils at 20K (at 1 atm pressure), so there's not much of a "window of liquidity" there.

I note that the wiki article at least says that to make liquid hydrogen you also have to pressurise it. So it is in fact pressurised in the fuel tanks already - though there presumably is leeway to compress it further so you can potentially pack twice the amount of hydrogen in the tanks (or more) while keeping it in a liquid phase.

 

[Gaidheal]

Well, if you really want it, it's bound to be on a datasheet or the back of one of my textbooks, I'm sure. It's also possible to simply calculate it, given some numbers (which will definitely be in my data).

I'm unclear what your overall intention is, though:

Are you trying to come up with more realistic spacecraft, in terms of fuelling, engines and use of volume?

 

[snrdg121408]

Hello Gailheal,

I am one of those odd people that likes to know all sorts of information that gets used once in a blue moon. Usually, like this thread, I started out trying to make sure I understood how the metal hydride storage option was calculated which had others provide more data on related data.

Back in the mid 1980s I did try my hand at creating a more realistic spacecraft without the benefit of TNE/T4/GT and from a couple of other games' design sequence. I decided that I'd stick with Travellers since several other people had already come up with a decent system.

Again thank you for your assistance.

Well, if you really want it, it's bound to be on a datasheet or the back of one of my textbooks, I'm sure. It's also possible to simply calculate it, given some numbers (which will definitely be in my data).

I'm unclear what your overall intention is, though:

Are you trying to come up with more realistic spacecraft, in terms of fuelling, engines and use of volume?

 

[Gaidheal]

You're welcome, then. Incidentally, you don't need to quote our posts, certainly not the entirety anyway, to reply. If you do quote, however, put what you are responding to above your response, please? (AKA, don't 'top post', please) - it's a lot easier to follow that way (since it's logical and the way we read).

Thank you! :¬)

 

[EDG]

This page may be informative:

http://en.wikipedia.org/wiki/Hydrogen_storage

 

[snrdg121408]

Evening Gailheal,

Thanks for providing the guidance on the proper format for replying and my apologies for using a different format. I'll try to remember the proper technique for replying, but I learned a different style and being an elderly dog I take a lot of time changing habits.

 

[snrdg121408]

Evening EDG,

Thank you for the link to the wikipedia Hydrogen storage article, I found the information interesting and informative.

 

[Gaidheal]

Well, I'm not exactly an authority, heh! However, it's a common annoyance to many on various similar communications media - usually it's because the default 'reply' option is implemented extremely unintelligently, in my opinion.

Anyway, on a forum, especially, if the stuff you're replying to is visible on the same page as your own post there's no real need to repeat it, is my opinion, except to draw special attention to something, in which case, repeat only that part. Opinions probably do vary, though, so thanks for politely replying. :¬)

 

[snrdg121408]

Evening Gaidheal,

I agree that various options, not just reply, on forums are sometimes poorly executed.

My, bad, habit of quoting started as a way to reference the material I was responding because I could not refer back to the original document. Then instead of deleting the quoted material I got lazy and left the material in the reply.

I don't see any reason not to be polite to others, even when the comments are pointing out some something that I did that was out of the norm. The suggestions on proper forum replies was appropriate and helpful. Hopefully, I'll do better in the future.

Thanks again for the help, stay tuned for more questions.