Wattah!

I've made a big change to my next Traveller game.

The huge tanks of hydrogen will be replaced with water.

The main reason is that it's not 1977 any more.

In 1977 it likely seemed very reasonable to the writers at GDW to use hydrogen for the ship's fuel as it appeared to be the only readily accessible fusion fuel source.

This was before the Kuiper Belt was theorized, let alone discovered or widely known.

This was before the past 36 years of research into fusion.

Water is plentiful in the solar system, and mostly more accessible than raw hydrogen.  You have to thaw it though.

Besides electrolysis, applying ridiculous levels of heat will separate oxygen and hydrogen in water.  That's something a fusion reactor has to spare.  Then it's a few protium reactions, a couple of lithium 6 injections and whammo!  Tritium fusion breeding He3 fusion.  Consume the oxygen as a secondary burn or collect it to use as a coolant, your choice.

In GURPS terms the Traveller power plant consumes an insane amount of fuel, but I am OK with that since the reactionless drives are insanely violating physics; and that's pretty much the entire consumption from a power plant in the Traveller canon.  The extra mass from using the same volume of water is side stepped by the drives apparently moving a volume and not applying thrust to a mass.

For years I grappled with a good game reason to get the players to purchase fuel from the star port instead of harvesting it from the local gas giant and I think I've gotten it licked; and it took changing the fuel to water to get there.

The Kuiper Belt is out there a ways, so to harvest water from the ice puts you an inconvenient distance from the main system.  Yes, you can get free water, but you lose the travel time.  If you're a merchant ship you only make money on delivery, so anything that spreads the paydays out is costing you.  Time is literally money to any freight hauler.  This gives the players an incentive to purchase fuel from the port, as long as it's cheaper than losing a week to travel.

What could be cheaper than water?

Using water also allows me to retain the refining step from canon.  Industrial water is far more pure than tap water or "wild" water.  All sorts of impurities you don't want in your fusion bottle.

You lose the drama of the dive into a gas giant for fuel, but I've yet to have a player be happy about the idea of their character's lives depending on a single piloting roll.