mike wightman
SOC-14 10K
So it magically disappears when full? Neat trick. 100t cargo hold can hold 99t of fuel, 1t is needed for the bladder folded or unfolded.
Resource Scarcity in the Far Future
- Thread starter Bartleby
- Start date
Though as I re-read the refining rules, I am getting a stronger and stronger impression that converting to liquid H is the only processing, and scooped methane or water is used as-is, when the game refers to unrefined fuel and is why you take a penalty on jumping with unrefined fuel, because it's a bit cumbersome to just-in-time process the amount of fuel you'd need for a jump. So Just-In-Time jump fuel processing is already accounted for in the 'Jumping with unrefined fuel' penalty to the jump roll.
Power plants, as far as I know, run fine on unrefined fuel?
But you're not scooping liquid ammonia or methane. So are you condensing it as you scoop? Alternately, what is the hydrogen content of gaseous ammonia or methane?
Presumably fuel processors that can chill hydrogen to liquid state can do the same for methane or ammonia, so does a ship that scoops fuel from gas giants require the presence of processors regardless of whether you spend the time to process your scooped material into liquid H to avoid the -2 to jump?
Spinward Flow
SOC-14 5K
Okay, RAW.
LBB A5, p13-14:
When the RAW is interpreted correctly, the "1% tonnage" condition applies when the fuel tank is NOT IN USE ... meaning it's EMPTY.
So ... a 100 ton collapsible fuel tank that is EMPTY and therefore
NOT IN USE 
will still require 1 ton of cargo hold (or equivalent) space to be stored in.When the fuel tank IS IN USE ... meaning it's FULL (or even just partially full) and being used ... the 1% of filled tonnage because NOT IN USE condition obviously no longer applies.
A 100 ton capacity collapsible fuel tank holds 100 tons of fuel when full and fits into a 100 ton cargo hold (or equivalent) space while filled.
A 100 ton capacity collapsible fuel tank that is empty and not in use requires 1 ton of cargo hold (or equivalent) space while empty and being stored.
However, can this principle be extrapolated upon?
What happens in a "half empty/half full" condition?
So let's stick with our 100 ton capacity collapsible fuel tank in a 100 ton cargo hold for a moment ... and assume that the collapsible fuel tank is only HALF full ... what then?
The 100 ton capacity collapsible fuel tank has 50 tons of fuel in it ... and 50 tons of capacity remain unused.
Well, obviously ... the 50 tons of fuel capacity filled with fuel is occupying 50 tons of cargo hold capacity.
However, the 50 tons of UNUSED fuel capacity is still subject to the "1% rule" and is thus occupying 0.5 tons of cargo space.
This means that under these conditions, a 100 ton cargo hold would have 49.5 tons of capacity remaining for cargo loading.
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mike wightman
SOC-14 10K
I used the densities of the liquids, since somehow the scooping process can magically conjure liquid hydrogen in the fuel tanks.
mike wightman
SOC-14 10K
When not in use, collapsible tanks collapse and are stored in the cargo hold ;
they take up 1% of their filled tonnage.
Take an empty balloon, roll it up as tightly as you can. Measure its volume. Now inflate the balloon. Does the skin of the balloon magically vanish? No, it gets larger it has a greater surface area but is thinner, less thickness. I wonder what its volume is collapsed vs inflated.
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I had thought that, too, but now am not sure. If the scooping process only scoops the raw material, it'd get liquid water, which is fine, or gaseous methane or ammonia, which I didn't know about. I now think the fuel purifuer, which processes 20T of fuel in 24 hrs, per ton of purifiers, is what converts the scooped material into liquid hydrogen, and until that point, just sits as water/ammonia/methane in the fuel tank. However...
But while there is 1685 kg of hydrogen in liquid ammonia, there is only 1.9kg of hydrogen in gaseous ammonia. But "ammonia vapor", which I'm not sure how it's different from ammonia gas, gets you 1473kg of hydrogen.
Likewise, methane liqud is 1480kg, but 2.5kg as gaseous methane, so the conversion to liquid is required.
(Conversions from www.aqua-calc.com)
All that said, whether ammonia, methane, or hydrogen, keeping it as a liquid requires super cold temperature, so I would have to assume that's a standard feature of fuel tanks? Water is liquid up to 100C, but Methane changes from liquid to gas at -161.5C, Ammonia changes from liquid to gas at -33.4C, liquid hydrogen changes liquid to gas at -259.16C, so "standard fuel" is actually your actual coldest case, so there must already be cooling gear to keep your fuel at the correct temperature, so scoop away at the methane or ammonia your fuel tank will chill it until it consenses and that will get you the density you need.
No it does not disappear, but do you calculate the VOLUME added to your Starship when you paint the Hull so you can reduce its Jump Performance, or is the thin paint membrane an insignificant % of the total volume that falls below the threshold of precision of the calculation?
So too, is the thickness of the membrane (which is NOT subtracted from the Cargo Hold for allowable volume of FUEL in a Dismountable Fuel Bladder) a thin membrane of insignificant thickness to the volume contained.
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Pretty sure that is 100% correct. Small Craft and BOATS (non Starships) use unrefined fuel fine. OLD CT Rules said the Scout Ship had DRIVES that were hardened to safely run on unrefined fuel - including Jump - but that was pre High Guard, so many people ASSUME it just has a PURIFIER.
- It is possible to liquefy a gas using SHOCKWAVE COMPRESSION ... the essence of skipping through an atmosphere at orbital velocity with a RAM SCOOP open.
- Space (in general) is about 4 degrees K ... that qualifies as REALLY COLD for condensing gasses into liquids.
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Seems reasonable. The outer layers of Jupiter are about -110c, though, and it gets hotter as you get deeper, so the methane is a gas at all layers, so you'd still have to scoop it as a gas and carry it off to let space cool it. And then go back and fill up several times. Or, since the fuel tank must come with chillers since you need -259 for the liquid H anyhow, so you can chill it as you go while you scoop. As to the shockwave compression, I have no idea. But wikipedia says shock wave compression results in a loss of total pressure, so I definitely don't understand how that works.
I did find out that the methane and ammonia content of Jupiter is pretty negligible, less than 1%, and that it's roughly 75% hydrogen 25% helium, so that means most of what you'd scoop would just be hydrogen, and you'd have to cool it from -110 to -259 to get it to liquefy. You'd still need to purify it, as helium's not going to fuse at hydrogen fusing temps, so you'd have 25% unusable fuel (and just as well, if the helium did fuse, it'd produce energy at a rate comparable to the whole galaxy, which I can't imagine is safe for the ship).
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Spinward Flow
SOC-14 5K
Point of order ... space (vacuum) is a notoriously poor heat sink to dump thermal loads into.
Just a reminder.
Actually, the helium would be useful for a variety of things, including thermal transfer. Heat the helium up and dump it overboard.
High energy uses of this sort of thing would amount to HEPlaR maneuver drive types of reaction thrust propellant gas applications.
Low energy uses of this sort of thing would functionally be a means of waste heat rejection out of the craft (via venting of helium).
And let's not forget that helium has its uses as a refrigerant working fluid for things that need to be kept cold.
So although the helium would "not be useful" in the power plant for fusion reactions, there are plenty of OTHER uses that skimmed helium could be put to if it can be separated out from gas giant atmospheric gases by a refining process onboard. Have engineering, will travel(ler).
Not to count the point made here regarding volume, but the original Space Shuttle launched with the external fuel tank painted white.
They stopped painting it (leaving it orange colored) to save weight.
An air conditioner compresses a "working fluid" (gas) and accelerates it in a constricted tube, then the compressed/accelerated gas is allowed to slow and expand. This change in pressure results in a drop in temperature that liquefies the gas and releases heat (the HOT side of an AC or Refrigerator). Shockwave compression works similar, only with supersonic shock waves to compress the gas. So it will cool the gas into a liquid and radiate lots of heat [just like the Fusion PP waste heat].
I could see that as an element of heat dispersion for reentry/gas giant refining where you have an atmosphere to radiate into- maybe not so much deep space fusion heat discharge.
No, I was not clear.
I merely meant that ... LIKE THE FUSION PP ... Shock wave Compression is yet another source of waste heat that magically goes ... SOMEWHERE???
~70 mols H per liter of LH2, I think.
mike wightman
SOC-14 10K
The container volume doesn't magically disappear.
A fuel bladder that has a volume of 1t empty still has a volume of 1t.
Can you put a 1 litre glass inside another 1 litre glass?
A fuel bladder that has a volume of 1t empty still has a volume of 1t.
Can you put a 1 litre glass inside another 1 litre glass?
So the volume magically disappears? An as for painting the hull, yes, painting the hull should add to the displacement of the ship, otherwise you could just armour a ship by slapping armour plates on the outside and not worry about ship displacement increase.
So what is the threshold?
And that is where reality snaps - any container with an internal volume of 1 litre can not fit inside another 1 litre container.
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mike wightman
SOC-14 10K
It is edition specific. In CT from 77 right through to TTB and ST there was this:
"Drive Failure: Each week, throw 13+ for drive failure; apply the following DMs: +1 if using unrefined fuel (and not equipped to do so), +1 per engineer missing from the crew list, +I per week past annual maintenance overhaul date. If a malfunction occurs, then throw 7+ for each drive in use (jump, maneuver, power plant) to determine which actually fail, (if any). Failed drives cease operations completely; maneuver drives will no longer thrust, jump drives will fail and indicate that they cannot support jump; power plants stop delivering power. Batteries will provide life support and basic lighting for 1D days. Throw 10+ per day of repair attempt with DM +engineering skill of the attending engineers to fix them temporarily. More complete repairs must be made at a starport by qualified personnel."
MT mentioned drive failure, thereafter it is difficult to track down rules for this. But if yours is a mostly CT/HG universe than yes, the power plant can fail due to unrefined fuel.
mike wightman
SOC-14 10K
Space is also a perfect insulator so you can only cool it by mechanical means or radiation of heat.
mike wightman
SOC-14 10K
Traveller has magic heat sinks.
I did suggest a way to incorporate gravitic heat sinks into the new MgT SOM handwavium.
