If you're going to be refining it anyway, ship water. If my calculations are correct (*), 1 dTon of water is equivalent to 1.556 tonnes of hydrogen. And, of course, you'll need to ship some water anyway, even if the station is fully automatic.

David Shaw

(*) 1 dTon (14 cubic metres) of water weighs 14 tonnes.

1 mole of water weighs 18g

=> 1 dTon of water contains 777,777.778 moles of water

1 mole of water contains 1 mole of hydrogen (H2)

=> 1dTon of water contains 777,777.778 moles of H2

1 mole of H2 weighs 2g

=> 1dTon of water contains 1,555,555.556g or 1.556 tonnes of H2

Just about everything else is worse. Hydrocarbons suffer from being generally less dense than water, and while the alkanes have a higher mass fraction of H2, their lower density means they contain less H2 than an equivalent volume of water. Metal hydrides either have higher densities than water but much lower H2 mass fractions or higher H2 mass fractions but lower densities (and some of them can be rather nasty. Lithium hydride, for instance, spontaneously ignites on contact with moist air).

The closest alternative I've come across so far is liquid ammonia at 1.206 tonnes H2 per dTon, 22% worse than water.

On 15 Jul 2017 15:38, "Jeff Zeitlin" <xxxxxx@freelancetraveller.com> wrote:

Canonically, one can scoop unrefined fuel from the atmosphere of a gas
giant, or dip it from the oceans of an Earth-like world, and then
refine it for use in the jump drive and power plant. This suggests
that the canonical refiners can break down Damn Near Anything to get
the hydrogen out, and then compress and cool the hydrogen into stored
refined fuel.

OK. I'm with that. I'll take a handwave on the actual tech.

I'm willing to accept that a facility that uses fuel will do so faster
than reasonable refining capacity can provide it - that is, the
refiner can't feed the plant or j-drive directly; you need the total
volume of refined fuel available when you hit the 'go' button.

TNE allowed for "empty hex" jumps, to 'Calibration Points' -
essentially, deep-space stations. I believe that the assumption was
that there was an icy body to provide fuel there, large enough that
there was no need to discuss how they were supplied.

Assume now that a deep-space station _does_ need to have fuel
"trucked" in. The station has sufficient tankage and sufficient
refining capacity to meet its needs as a fueling station, plus it can
keep itself supplied with respect to power plant needs. What's of
interest now is how to most efficiently truck the fuel in.

A little browsing of Wikipedia says that refined fuel - Liquid
Hydrogen, H2(l), has a density of 70kg/m3 - or, by definition of a
Traveller dton (displacement ton), 1 tonne per dton.

Question: (Please show your work!) What substances can be transported
with an "effective refined fuel density" (ERFD) that's higher than
H2(l), and what substance has the highest ERFD? Also note if the
substance in question requires any special handling (i.e., deviations
from STP) to achieve the stated ERFD.

(It's understood that by definition, anything with a higher EFRD than
H2(l) is "unrefined" fuel. That's OK; remember, it's being refined
on-site at the deep-space station.)


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Far Future Enterprises, 1977-2017. Use of
the trademark in this notice and in the
referenced materials is not intended to
infringe or devalue the trademark.

--
Jeff Zeitlin, Editor
Freelance Traveller
    The Electronic Fan-Supported Traveller® Resource
xxxxxx@freelancetraveller.com
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