# Jump capacity

I'll keep the maths simple...

1.3 displacement tons of water gets you 2 displacement tons of hydrogen.
So what you're really saying is that Traveller rules, which deal with displacement and not mass for everything from M-drives to jump, you'd be better off using water tanks than liquid hydrogen tanks. You just need the power to electrolyze the water prior to use - easy for M-drive consumption rates. Not so much for j-drive. But any 'spare capacity; for a second jump could be carried in water tanks and then 'refined' during or after the first jump into hydrogen.

Yup.
Water, ammonia and methane are all "better" at storing hydrogen than liquid hydrogen.

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I have a situation in the MGT2 game I am running. The travellers have effectively missjumped (inflicted by NPC) and are now stranded on a planet 4 parsecs from the next system. They have the Harrier (Pirated of Drinax) with J2 capability. They will have to jump to an empty hex and then wilderness jump to the next inhabited system. They will have to build a droptank/external tank to supply the fuel they will need for the back-to-back jumps they are making adding an additional 40dT to the ships 200dT. This additional mass/volume would require an additional 2dT of jump drives.
A 15 Dt jump drive can do J-2 in a 200 Dt ship and J-1 in a 400 Dt ship.

Strap as many tanks as you need to the ship, then do a series of J-1 till you reach civilisation. Takes a few weeks more, but no real problem.

The internal tanks will provide the fuel for the last lap.

Just looked at the drop tank rules and realised that there is a.penalty of 15 - tank TL to jumping. What TL would you assign a wilderness creayed.drop tank?

Just looked at the drop tank rules and realised that there is a.penalty of 15 - tank TL to jumping. What TL would you assign a wilderness creayed.drop tank?
What tech level are your tools? That's the best. And then make someone do a Very Difficult Mechanic check and subtract any negative Effect from the TL to cover flaws. Well, that's how I would fake it anyway... Also depends on what they used for parts, I suppose.

You're unlikely to need that particular set of drop tanks again.

What tech level are your tools? That's the best. And then make someone do a Very Difficult Mechanic check and subtract any negative Effect from the TL to cover flaws. Well, that's how I would fake it anyway... Also depends on what they used for parts, I suppose.
I love that idea. They have TL 14 tools and since the ship is TL 15 the parts will be at that level.
You're unlikely to need that particular set of drop tanks again.
True, I wasn't expecting to keep the tanks. Just evaluating the difficulty of the jump.

Should make them out of aluminum, since I'll assume aluminum is cheaper than titanium steel.

Pre crushed.

The simplest way is to make 2 or 3 small tanks (you will need 50 dT of fuel). No need to make them droppable or to alter the ship.
The tanks should be built at 100D from where you will be getting fuel & will stay there until you jump away. This way you won't have the accelerate or enter an atmosphere with the tanks attached. This way no need to make anything fancy to attach the tanks (won't need to hold acceleration).
1st jump will be 1 parsec, with 250dT & requires 25dT of fuel. Both tanks stay attached.
After the jump, the ship will be in deep space. Transfer 25dT to the ship inner tanks & drop (throw away) the empty tank.
2nd jump will be 1 parsec, with 225dT & requires 22.5dT of fuel. The remaining tanks stays attached.
After the jump, the ship will still be in deep space. Transfer 25dT to the ship inner tanks & drop (throw away) the empty tank. This will top the jump fuel with some leftover for powerplant.
3rd jump can be a 2 parsec jump toward the nearest system. It will just need 40dT of fuel.

This way, no need to bother with the TL of the tanks, you won't drop them just before the jump -> No jump penalty. And the construction will be simplified, just a pair of tanks capable of holding LHyd with a way to transfert the fuel (might be a pump in the hold, no need to put it in a disposable tank).

This way, no need to bother with the TL of the tanks, you won't drop them just before the jump -> No jump penalty. And the construction will be simplified, just a pair of tanks capable of holding LHyd with a way to transfert the fuel (might be a pump in the hold, no need to put it in a disposable tank).
So, reduce cargo space by the amount needed for external cargo clamps of the requisite size. "Repair" the section of hull to the original configuration when you get back to civilization.

Remember (if you're going to be making multiple jumps without docking or refueling) that you'll also need to stock additional consumables (food, primarily, but also other items) and additional power plant fuel - most ships as designed only provide enough power plant fuel for four weeks, so if you're going to exceed that, you need to provide. Being forced to decide between running out of power and making that last parsec home really sucks...

We're dealing with the Harrier, which is supposed to be a commerce raider.

Crew could be super sized, to provide personnel as prize crews, or you could have prisoners (of war), and one supposes that they have provisions for long voyages.

Speaking of cannibalism, you could shut down parts of the starwarships that you aren't using, and use equipment to make ad hoc ad hoc adjustments or repairs of the more essential stuff.

I'm working on that for the World Builder's Handbook. In fact, "Empty Hexes" is the last process I need to test before turning in the manuscript. There would probably be an effectively unlimited number of asteroid-sized bodies, but detecting them from a parsec or two out...

With the Harrier's advanced sensors about 4-12 weeks of scanning a hex 2 parsecs out, assuming a competent operator, but if there happens to be be a rogue gas giant out there (rolled secretly by the referee with the same likelihood as a star occupying a hex in that region (roll one check for large, two for medium {Jupiter is medium - superjovians demoted it} and three times for small) then they would be detected in much less time. A parsec-wide hex is a big empty place. Like I said, testing what I wrote. It looks good on paper, but it needs a little excel simulation to see if the process is practical in use.

Then there's the risk that it "looked icy" on scanners, but turns out to be dry. And the risk of a slight miscalculation in the jump distance leaves you needing one of them drives from Deepnight Revelation to move in deep space. Jury-rigged drop tanks might be the safer bet.
I can’t wait to see your “empty hex” section in the new World Builders’ Handbook

Empty doesn't always mean EMPTY. It means there are no planets there, but there can be literally hundreds of adventure ideas that have nothing to do with drop tanks, or technology, or drives or anything like that. Maybe they've heard of some planetoids in that hex with possibilities. They could find other salvage. Alien outposts. Pirates. Whatever.
Imagination is at least as important as planning. Good luck.

Empty doesn't always mean EMPTY. It means there are no planets there, but there can be literally hundreds of adventure ideas that have nothing to do with drop tanks, or technology, or drives or anything like that. Maybe they've heard of some planetoids in that hex with possibilities. They could find other salvage. Alien outposts. Pirates. Whatever.
Imagination is at least as important as planning. Good luck.
Exactly.
Although, I just created rules for encounters in an empty hex to tide me over until the release.

As I understand it, there's no large enough local gravity well to hook the jump drive on.

Reliably, anyway.

As far as I am aware, there is no rule that says you can't jump into the middle of nowhere if you wanted to. At some point during the various editions, Maneuver drives in deep space were nerfed. So if you use that rule, it'll make deep space doings more annoying.

Personally, I choose to go the other direction: deliberately jumping to or from deep space is quite doable - if rather harder than to a star system, since you don't have that convenient big, bright target. It's just more difficult, both to get the numbers right and to determine exactly where you've emerged. Also, deep space doesn't particularly hamper maneuver drives so far as I'm concerned... although relativity may very well do so; pointing your ship in a given direction and just letting the M-drive run at full power is likely to result in BAD THINGS HAPPENING (tm), probably in a shorter time than whoever did it is expecting.

So no, even without a deep space limitation on the M-drive, there probably won't be any realspace trips between hexes. The speed limit is still c, and how many ships do you know of that carry 170 weeks' worth of power plant fuel?

I don't think anyone was talking about NAFAL travel. The nerf to Maneuver drives that makes them minimally useful in the outer region of star systems or in deep space is problematic for if you are trying to get to a comet or some deep space anomaly.

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