# Jump capacity

#### Gavain

##### Banded Mongoose
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.
HG states that Jump-2 drives are 5% of the ships mass (10dT) plus 5dT. Would you allow the additional volume to be covered by the extra 5dT, allowing the ship to jump-2 parsecs, or rule that you would need 17dT of jump drives and therefore the ship can only make a jump-1 with the current engines (15dT)?

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.
HG states that Jump-2 drives are 5% of the ships mass (10dT) plus 5dT. Would you allow the additional volume to be covered by the extra 5dT, allowing the ship to jump-2 parsecs, or rule that you would need 17dT of jump drives and therefore the ship can only make a jump-1 with the current engines (15dT)?
Well, if this would be Elite Dangerous then I would say call the Fuel Rats.
So they are currently in a system that allows them to create external tanks, upgrade the jump drive and refuel? Why not just get help from another ship with a lot of fuel capacity that jumps with them and refuels them on the way? Or put a fuel station two parsecs on the way that bridge the gap for ships that do not have Jump-4?

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Or plant the idea that the empty hex might have ice asteroids they can look for…

Make them look for a while, to keep things interesting then help them out of there?

If you can fabricate a drop tank you don't need to worry. Drop tanks that are dropped before jump do not add their tonnage to the ship.

Build a 40t drop tank and drop it as you make the first jump - you will still have enough internal fuel for jump 2.

This additional mass/volume would require an additional 2dT of jump drives.
HG states that Jump-2 drives are 5% of the ships mass (10dT) plus 5dT. Would you allow the additional volume to be covered by the extra 5dT, allowing the ship to jump-2 parsecs, or rule that you would need 17dT of jump drives and therefore the ship can only make a jump-1 with the current engines (15dT)?
No, the additional volume would not be covered they would need a larger jump drive.

If you can fabricate a drop tank you don't need to worry. Drop tanks that are dropped before jump do not add their tonnage to the ship.
Will also need a drop tank mount for this.

So you make one of those too.
I'm sure you can find a spare 0.16 tons from cargo or whatnot.

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Thanks for your input. I wasn't sure if drop tanks were the way to go or not. Happy to push the crew in that direction. They only need 0.16 dT (0.4% of 40dT = 0.16dT).

Or plant the idea that the empty hex might have ice asteroids they can look for…

Make them look for a while, to keep things interesting then help them out of there?
Any idea how likely it is that there would be a suitable body to mine ice from? How easy would it be to find using only ship sensors?

1. If you have the resources and the technical knowledge, iron tank, plumbing equipment, explosive bolts, and some internal tinkering for the mounts.

2. Might have to cannibalize some parts of the starship, if you don't have a third party way of sourcing them.

3. Second choice would be external cargo, ie the iron tanks, and retank every time you exit; for four parsecs, two factor one jumps, and the rest on the internal tanks.

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Any idea how likely it is that there would be a suitable body to mine ice from? How easy would it be to find using only ship sensors?
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.

You know something, modern astronomy and sensor technology has made an empty hex missjump almost certainly survivable for any ship. Say it was a 200t A1 that had suffered the missjump. A few weeks to find a suitable 'icy' body (water, ammonia, methane take your pick) is much better odds - and greater potential for adventure - than the ship being lost.

You know something, modern astronomy and sensor technology has made an empty hex missjump almost certainly survivable for any ship. Say it was a 200t A1 that had suffered the missjump. A few weeks to find a suitable 'icy' body (water, ammonia, methane take your pick) is much better odds - and greater potential for adventure - than the ship being lost.
Agreed, but sticking with the T5 1000D m-drive cut-off (or severe drop-off) then you might still run out of powerplant fuel (meaning life support energy) before you get there. But it does make for a better story line than: "Nope. Misjump to nowhere. You're all dead - but it takes a long lingering time unless you just give up, shut down the ship, and freeze. So. Let's roll up some new characters, shall we?"

A kinder and gentler referee could assume that the misjump terminates when the ship hits the 100D limit of an icy body (or rogue gas giant) in deep space.

Note other options would be collapsible fuel tanks, fuel/cargo containers, mountable tank and maybe ramscoops as well.

Any idea how likely it is that there would be a suitable body to mine ice from? How easy would it be to find using only ship sensors?
If the story and plot requires it, I’d say the likelihood is close to 100%, but the players don’t have to know that beforehand… Make it exciting for them, let supplies and fuel run low first… Then they can “luckily manage to stumble upon it” and make their way back to civilization and live happily ever after

Note other options would be collapsible fuel tanks, fuel/cargo containers, mountable tank and maybe ramscoops as well.
Ooh, have them jury-rig the cargo scoop into an improvised ramscoop!

And after they survive, advice them to install one of the above fuel options

You could have them use staterooms, hallways and any other open internal space to store water in containers that you would then dump into the tanks. It's the same idea as collapsible tanks, but on a smaller scale. It would literally be barrels or containers holding water. It wouldn't be 100% efficient, so you'd have to factor that into things (say a 20 -25% loss in conversion).

Crews could hot bunk in staterooms without violating the rules (this scenario slides between the restrictions anyways). The crew might be a bit stressed on the trip, but its certainly doable and stays within the rules.

You can look at old photos of submarines leaving base on long patrols and see how they had food stored all over to give them longer time at sea.

Just over 11% of water is elemental hydrogen. Oxygen takes up over 88% of the space in that molecule.
For quick math, 10% of the barrel goes into the Power Plant. Slower math is 11.19%.

Oh yeah, life support.

How's that holding up in the wilderness?

I'll keep the maths simple...

18,000kg of water contains 16,000kg of oxygen and 2,000kg of hydrogen in 18 cubic metres. 1.3 displacement tons of water gets you 2 displacement tons of hydrogen.
So fill a 'stateroom', 4 tons, with water and you have 6 tons of hydrogen. 7 staterooms or their shared space equivalent (56 deckplan squares) gets you enough water to produce 40 tons of liquid hydrogen.

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