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Jump Drives


I have a few questions about Jumpdrives/Jump space.

First one: Where does the fuel go when it used up.

Second: How big is the jump space for a ship?

Third: What is at the edge of jump space?

Fourth: If the jump drive fails while the ship is jump space, is the ship instantly destroyed? Or does the jump space take time to collapse...

I have visions of crew members desperately trying to fix a jump drive as space buckles and folds around them.
IIRC applies to all the following:

1) I don't know if it was ever addressed.

2) Normal space extends about 2 meters from the skin of the ship, then "Jump Space" begins. No one knows the properties of jump space, but no rules of physics as we know them apply there.

3) No one knows. See # 2.

4) The ship will precipitate into normal space, but it would be a misjump. The ship could end up as much as J10 or more away from it's intended destination.

As for your comment, it could happen. Don a vacc suit and crawl, VERY carefully, along the skin of the ship to fix the damaged whatever-it-is so the ship doesn't misjump
Some answers as I recall them:

1) This is one of the canon flamewar topics for Traveller. It is partly addressed in several different places. CT support drop tanks, which implies an all at once fuel use. MT explicitly stated an all at once for Fusion pulse to initiate jump. Marc Miller's Jump Space article in JTAS#24 (Reprinted in the online JTAS) also state a "all at once" for the fusion pulse to initiate Jump. So you can't go wrong with that answer.

2) two meters is the accepted answer, but you could make it larger or smaller without offending anyone.

3) The edge of the jump field, where physics no longer applies. Anything coming in contact with the jump field is disintigrated.

4) Depends upon how mean you want to be. There are canon examples (from the JTAS News articles) about how the partial jump field slowly collapses destroying the ship as it went. In general I'd say once the field starts collapsing, start rolling up new characters. Unless right at the end of the jump, the ship may be able to survive long enough for jump to end.
Cannon answers vary. Just to raise my post count, I offer the following house rules interpretation of the tech and how it works...

OK: bigtime, non-cannon, technobabble, IMTU, screwball content follows: This is a compiliation of other people's stuff and some of my own ideas as well.

IMTU, Jump drives use a "jump core" which generates a spherical field around the ship in question. Gravity interferes with the shape of this field, and may warp or stretch it into an off center position. If the field is far enough off center, a misjump occurs. If enough of the field is off center to expose large chunks of the ship, a catestrophic misjump occurs and may destroy the vessel.

This jump field protects the jumping vessel when it "jumps" out system. Borrowing on the "mathmatically resembling a wormhole" idea from TNE, it seems reasonable that the drive is actually routing a tunnel through a compressed space to the emergence point. A massive fusion pulse is required to make this happen, but does not account for all of the jump fuel.

Borrowing from somebody else's idea that I saw on the net somewhere (I don't remember where, but the idea struck me as solid)... It also makes sence that the jump field will be more stable when populated with "stuff"... kinda like a using water instead of air in a baloon... it handles compression better. The bulk of the jump fuel is used to fill this void and keep the jump field stable for the duration of the jump.

The greater the distance involved in the jump, the greater the compression of space through which the ship has to tunnel. This greater compression means greater stresses on the jump field, and more hydrogen is required to keep it stable (and initiate the pulse to get the ship there in the first place). Fuel consumption is thus a function of volume moved, and not mass.

The jump drive bores the tunnel through the compressed higher dimensions to the target, but then pretty much just keeps the field stable and "on axis" for the rest of the trip. Since the tunnel is essentially sloping "down hill" to the less energetic lower dimensions, the ship and whatever was in the jumpfield will eventually emerge at the other end... intact or not. The spotting of wreckage at the destination and near a jump flare is how misjumped ships are identified... assuming they end up somewhere civilized.

As the ship falls down the tunnel, waste heat from the ship itself, compression induced heating, and all sorts of other nifty effects warm the hydrogen atmosphere within the jump bubble. As a result, when the ship re-emerges into n-space it is accompanied by an energetic "jump flare" of escaping hydrogen plasma. Very hard to miss on most sensors.

If the jump field somehow is badly formed (from a defective drive, unrefined fuel, etc), then odd things can happen inside the ship as it jumps. Adventures could spring from trying to get the core to stablilize the field, pumping more jump fuel into the envelope, or just trying to keep the passengers away from the affected areas until the ship emerges at the other end.

Like I said... non-cannon, screwball, and only partially grounded in physics... but it works well enough IMTU.
I rather like that.

This also makes a misjump (or even a longer-than-average jump) very hard on the skin of a starship. You have a week of heat from a starship building up in this hydrogen gas - that stuff will be very hot indeed by the time you are done. So when you pop out of jump space, yah, there is a huge flare.

I think this is nice and cinematic...

Imagine hanging out on a dark ocean on some high tech, high population world, where the stars are populated with almost constant pin-point flashes - of the comings and goings of the merchant fleet - not unlike the light you get off an Iridium flare.
My 'house-rule' was that jump space was actually a 'hole' out of our space into 'jump space' or 'hyberspace' or 'N-space'; it was called different things depending on where the species was.

The ship would then travel into the hole and 'BAM' they'd be in jumpspace. The hole would then close behind them a few seconds after they entered it.

This opened up a number of interesting ideas; but first some perameters as I described them:

Jump engines were actually generators. They had to generate intense magnetic fields in a localized spot (10+ teslas). The fuel was used to cycle these generators i.e. the generators would burn the fuel in order to create the power.

I treated it as if the travel through jump space was more akin to tossing something through a medium. The creation of the hole was structured for distance and end location and the ship created a lozenge in jump space while it travelled through this hole. Actually, the exit of event the hole travelled with them. This event wasn't observable from normal space, but the people in the jump ship could see it. I always described it as Aa chaotic patterns of flashing lights and colors that the human mind could not grasp" and staring for too long into it would drive men mad.

Now, for the interesting stuff having jump space be like this meant.

Jump-Ships. These are ships that generate their own jump holes and non-jump capable ships can then enter jumpspace. This makes battle-riders more interesting. I also used the old spinward marches map with the trade lines and treated that as a 'jump gate route'; meaning that a gigantic jump generator would open a hole for a fee to that system. And, there was another generator at that system that would open a hole....etc....

Also, ships could try to 'piggy back' on another ship's jump. This was quite dangerous and I once played a fighter chasing the characters down by hopping into thier jump hole because his acceleration vector was such that he couldn't escape it.

anyway....just a few thoughts from CT games I ran a looooong time ago.
RE: Various replies concerning JumpDrive failure or misJump effects.

AS I recollect, if a misJump occurred, (typically due to Jumping too close to a planet's or Sun's gravity field), the afflicted ship ended up an enormous 1D6(1D6) parsecs (ie. hexes) away in a random direction (roll 1D6: 1=Coreward, 2=Coreward Trailing, etc.). Note thus that the MisJump distance bore no relation to the actual Jump attempted- a J1 Jump could (theoretically) result in a J36 Jump!!! Quite incredible fuel efficiency. If the final misJump location contained a world, you came out near it, as if for a normal Jump, but did not know where you were. If it was empty space, well ooops! You hopefully had enough fuel on board to perform another Jump to a nearby system, or (if the GM is being kind), there is a derelict nearby with parts and fuel on board that can be salvaged.
This of course, makes for various adventure possibilities.

As for misJump damage, there was a table with results ranging from "no damage" to "minor damage to aerials, etc." to "minor hull damage" to "lanthanum grid [Jump Grid] damaged" and eventually "ship destroyed". It was certainly not a case of instant ship destruction.

References are to the Traveller hardback (etc.), which I don't have on hand, so can't quote page numbers, I'm afraid.

Hope this helps.

Rules Mechanics.
I always used to rule that the actual Jump took about a day, and that system exit/entry travel generally took up the remainder of a week, so a ship could Jump once per week if desired, or twice if it didn't bother with going in-system (and it had enough fuel available, or was using an LSP Jump Governor to double its Jump fuel efficency [cost about 175kCr/100 Ship Tons, Tonnage about 0.1Tons, as I recollect]). I and my friends always considered the "official" fortnight (ie. two-week) turnaround too slow and unrealistic.
I like the idea of piggybacking, a la Babylon 5; this does indeed make a lot more sense with regard to Battleriders, and other super-large ships that carry complements of fighters, or have escorting smaller ships. Such ships would then get a "Free Jump" with the main ship.

best Wishes to all,

Christopher Simpson (playing RPGs since 1976).