Jump Bubble diameter and location of Jump Drive

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Condottiere
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Jump Bubble diameter and location of Jump Drive

Postby Condottiere » Mon Sep 23, 2013 8:37 pm

Hi,

I wonder if anyone knows the following:

1. What's the diameter of the Jump Bubble?

2. Does the diameter vary, depending on the tonnage of the drive, it's damage status, etcetera?

3. Does the Jump Drive have to be placed on an exterior bulkhead or can you have them in the starship core?

4. Can Jump Drives be yoked in series, as long as the final tonnage equals to the required size necessary for the planned jump?

5. Do smallcraft need to be grappled during the jump, or if unsecured, could they drift and will they penetrate the Bubble boundaries?

Thanks
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Mon Sep 23, 2013 8:44 pm

Condottiere wrote:Hi,

I wonder if anyone knows the following:

1. What's the diameter of the Jump Bubble?
Big enough to enclose the ship.
Condottiere wrote:2. Does the diameter vary, depending on the tonnage of the drive, it's damage status, etcetera?
Unknown.
Condottiere wrote:3. Does the Jump Drive have to be placed on an exterior bulkhead or can you have them in the starship core?
Can be anywhere.
Condottiere wrote:4. Can Jump Drives be yoked in series, as long as the final tonnage equals to the required size necessary for the planned jump?
Not per RAW.
Condottiere wrote:5. Do smallcraft need to be grappled during the jump, or if unsecured, could they drift and will they penetrate the Bubble boundaries?
See rules for clamps. Ships floating near a ship that goes into jump don't "come along for the ride"
Last edited by F33D on Mon Sep 23, 2013 11:19 pm, edited 1 time in total.
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Re: Jump Bubble diameter and location of Jump Drive

Postby AndrewW » Mon Sep 23, 2013 11:07 pm

F33D wrote:
Condottiere wrote:4. Can Jump Drives be yoked in series, as long as the final tonnage equals to the required size necessary for the planned jump?
Not per RAW.
There's no restriction within the rules that say jump drives have to be all together. Ocasional deckplans do place parts in different locations.
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Mon Sep 23, 2013 11:21 pm

AndrewW wrote:
There's no restriction within the rules that say jump drives have to be all together. Ocasional deckplans do place parts in different locations.
Show where in the rules you can purchase two SEPARATE J-Drives and hook them together that way. I'll wait.

Not not for long as it doesn't exist.
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Re: Jump Bubble diameter and location of Jump Drive

Postby phavoc » Tue Sep 24, 2013 12:58 am

F33D wrote:
AndrewW wrote:
There's no restriction within the rules that say jump drives have to be all together. Ocasional deckplans do place parts in different locations.
Show where in the rules you can purchase two SEPARATE J-Drives and hook them together that way. I'll wait.

Not not for long as it doesn't exist.
That's the point of what Andrew said. It doesn't state that you cannot - it's and assumption because the rules don't talk to it in any sort of specificity.

Also, the comment can be interpreted to mean you can have a power plant room in the middle of the ship, the maneuver drive(s) positioned pretty much anywhere, and the jump drive could be in the front.

I think we all have come to understand the rules could use some polishing and more in-depth explanations of how things work and what limitations, if any, there are.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Infojunky » Tue Sep 24, 2013 5:17 am

Condottiere wrote:
1. What's the diameter of the Jump Bubble?

2. Does the diameter vary, depending on the tonnage of the drive, it's damage status, etcetera?
The Jump bubble is generally conformal to the hull, forming approx a meter or so away....
Condottiere wrote: 3. Does the Jump Drive have to be placed on an exterior bulkhead or can you have them in the starship core?
Wherever you want to place it.... It is an interior hit in the combat system....
Condottiere wrote: 4. Can Jump Drives be yoked in series, as long as the final tonnage equals to the required size necessary for the planned jump?
Yes, Kinda.... Maybe. If you mean does the Jump Drive need to be a unitary location on a deck plan, No. Could a drive and it's backup be a number of small units placed around said deckplan sure, though the rules treat them as unitary installations, so no benefit is gained. weather one or many.... Though there is nothing stopping you from running it differently in your game....
Condottiere wrote: 5. Do smallcraft need to be grappled during the jump, or if unsecured, could they drift and will they penetrate the Bubble boundaries?
Yes, as piercing the Jump Bubble is considered bad form....
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Re: Jump Bubble diameter and location of Jump Drive

Postby mr31337 » Tue Sep 24, 2013 10:10 am

Infojunky wrote:
Condottiere wrote:
1. What's the diameter of the Jump Bubble?

2. Does the diameter vary, depending on the tonnage of the drive, it's damage status, etcetera?
The Jump bubble is generally conformal to the hull, forming approx a meter or so away....
Interesting, I've never heard that before. Do you recall where this idea first came up please?

So what is between the hull and the bubble? Normal space?

Can a crew member exit a ship in jumpspace if he stays within a meter of the hull, for example to make emergency repairs?

Is it therefore possible to jump with a breached hull? I had always assumed that may interfere with the formation of the jump bubble, but if it's a meter off the hull then I can't see why not.
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Re: Jump Bubble diameter and location of Jump Drive

Postby tolcreator » Tue Sep 24, 2013 10:34 am

I'd always thought it was "About a meter from the hull" as well. Yes it is "real space" between the hull and the surface of the bubble, but going out there is a capital bad idea, as it leads to "Jump sickness". This is the same jump sickness that can happen in a misjump.

With a break in the hull, the jump bubble can be deformed and intrude into the breach, again leading to jump sickness if you get too close.

I'd always thought that there was a "jump grid" over the hull that produces the bubble (and partly "inflated" with some of the fuel used for jump). AFAIK jump sickness is caused because the jump boundary isn't 100%, and rather physics starts to get odd the closer you approach the jump bubble. I presume 1 meter is "good enough, then doubled" or what have you, to ensure the ship is safely within a zone of familiar physics.
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Re: Jump Bubble diameter and location of Jump Drive

Postby mr31337 » Tue Sep 24, 2013 11:03 am

Does anybody have any references for this 'meter from the hull' please?
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Re: Jump Bubble diameter and location of Jump Drive

Postby Ishmael » Tue Sep 24, 2013 11:48 am

Its from older editions' description of how j-drive works.
Specific reference is "Starships Operations Manual" from MegaTraveller.


The entire hydrogen jump bubble issue seems to be from the proposed use of the hydrogen fuel separate from the hydrogen fuel used for generating power. I had not seen this until relatively recently ( in MgT although I never saw T4 or GT )
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Re: Jump Bubble diameter and location of Jump Drive

Postby CosmicGamer » Tue Sep 24, 2013 12:28 pm

mr31337 wrote:Does anybody have any references for this 'meter from the hull' please?
I thought that the details for jump technology differed from version to version of Traveller.

For Mongoose, I did a search of my pdf's - which I hardly own them all - and there were 15 publications that came up when searching for "bubble". Escape bubble, Rescue bubble and so on. I checked every occurrence of the word "bubble" just in case there was a phrase like "bubble created by the jump engines" instead of the phrase "jump bubble" or "hydrogen bubble".

In High Guard, the two topical occurrences are in regards to drop tank operation. For example:
When a drop tank is used, roll 2d6. On an 8+, the tank survives the
ejection process and can be retrieved and reused. Otherwise, it is
destroyed by the expanding jump bubble or warped by the jettison
explosion.
An "expanding jump bubble" destroying a jettisoned drop tank makes me think the jump bubble expands over 1 meter - just my own impression.

Just a couple of excerpts from the core rules:
To Jump, a ship creates a bubble of
hyperspace by means of injecting high-energy exotic particles into
an artificial singularity. The singularity is driven out of our universe,
creating a tiny parallel universe which is then blown up like a balloon
by injecting hydrogen into it. The Jump bubble is folded around the
ship, carrying it into the little pocket universe.
and
While in Jump space, the ship is completely and utterly cut off from
the universe. It hangs in a shimmering bubble of boiling hydrogen,
a pocket dimension from which nothing can escape. It cannot
communicate with the normal universe, not even by psionic means.
It is utterly alone.
So, with the publications I have, I see no reference to a "one meter from the hull" jump bubble.

Again just my impression from the descriptions of bubbles and balloons, my minds eye thinks of a bubble formed around a lab ship as being more of a ship in a bottle look than a well fitted wrap one meter off all the surfaces.

Of course there are some logic issues with this along the lines of if the lab ship jump drives can create a "bubble" why couldn't there be additional craft within the bubble in the doughnut hole that get to tag along for the jump...
Last edited by CosmicGamer on Tue Sep 24, 2013 12:35 pm, edited 1 time in total.
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Re: Jump Bubble diameter and location of Jump Drive

Postby mr31337 » Tue Sep 24, 2013 12:32 pm

Thanks guys.

Coincidentally, in my PbP campaign the players have just breached the hull of another ship and I'm wondering if it would now be able to jump safely or not.

Frankly, I'm unsure. Any input would be welcomed.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Reynard » Tue Sep 24, 2013 12:42 pm

Reading sources for jump, especially the highly detailed Starship Operator's Manual, I realize why Traveller starships need to be very featureless and, by rights, of basic shape. The lanthanum grid determines the one meter jump bubble. The bubble itself is shaped by the ship's exterior. A ship can't have any protrusions or surfaces that would extend outside another grid surface. You will not see those bizarre anime ships bristling with wings, antenna towers and sensor booms. I'm sure the Nihon Space Agency was sorely disappointed when the vast arrays, struts and wings on their prototype were left behind.

Yamato looks a little duller as a tight cylinder.
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Re: Jump Bubble diameter and location of Jump Drive

Postby klingsor » Tue Sep 24, 2013 12:48 pm

If I remember correctly from older editions:

The hull of a starship incorporates a grid of lanthanum though other rare earth metals may also serve.

Drop tanks are used and dropped before the ship jumps.
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Tue Sep 24, 2013 1:12 pm

phavoc wrote:
That's the point of what Andrew said. It doesn't state that you cannot
Okay, it doesn't state that you CAN'T park a ship in the center of a star and leave again. Therefore you can. :roll:

I could go on ad infinitive about all the things the rules don't say one CAN'T do but. But, I'm logical and won't go down that nutty rabbit hole.
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Re: Jump Bubble diameter and location of Jump Drive

Postby phavoc » Tue Sep 24, 2013 2:31 pm

klingsor wrote:If I remember correctly from older editions:

The hull of a starship incorporates a grid of lanthanum though other rare earth metals may also serve.

Drop tanks are used and dropped before the ship jumps.
That's correct. Previous versions of Traveller utilized lanthanum for jump grids built into the ships hull, and zuchai crystals for the jump drives. I don't recall any mention of substitute minerals, as both lanthanum and crystals were highly prized throughout known space. The jump field surrounded the ship while in jump space. It was about 1m from the hull, and if you were crawling on the outside of the hull and made contact with the field you essentially got lost in space... somewhere in space, where you may or may not survive re-entry into normal space.

The rules were kind of hazy in regards to externally docked ships or items. A ship's boat would not normally incorporate lanthanum into the hull, so in theory it would not have arrived at your jump destination. So the idea has always been if you had something physically connected to the vessel doing the jumping, and the external something would also go into jump with you.
F33D wrote:Okay, it doesn't state that you CAN'T park a ship in the center of a star and leave again. Therefore you can. :roll:

I could go on ad infinitive about all the things the rules don't say one CAN'T do but. But, I'm logical and won't go down that nutty rabbit hole.
I get your point. But if you recall some of the official deck plans published over the years you'll see some ships that had physically separate m-drives (and you see them present in MGT published designs as well). The rules don't specifically state that this is allowed, but they do exist. And while this COULD BE another error that has cropped up in the "official" designs, I'm of the opinion that this supports my original position.
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Tue Sep 24, 2013 3:20 pm

phavoc wrote: I get your point. But if you recall some of the official deck plans published over the years you'll see some ships that had physically separate m-drives (and you see them present in MGT published designs as well).
Having ONE M-drive pictorially shown with its components in different locations of the engineering section has ZERO to do with purchasing SEPARATE and discreet drives, placing them in a ship, and "chaining" them together. Also, if you go back, look at those deckplans AND their associated listed components, you won't find multiple M-drives listed. ...
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Re: Jump Bubble diameter and location of Jump Drive

Postby DickTurpin » Tue Sep 24, 2013 3:58 pm

F33D wrote:
phavoc wrote: I get your point. But if you recall some of the official deck plans published over the years you'll see some ships that had physically separate m-drives (and you see them present in MGT published designs as well).
Having ONE M-drive pictorially shown with its components in different locations of the engineering section has ZERO to do with purchasing SEPARATE and discreet drives, placing them in a ship, and "chaining" them together. Also, if you go back, look at those deckplans AND their associated listed components, you won't find multiple M-drives listed. ...
A Jump Drive is an abstraction; a given volume of J-Drive allows defined performance within a certain hull volume. Does the entire volume of the drive need to be co-located? Probably not. It would make sense that small components of the drive that help define the shape of the jump bubble were scattered over the hull with connections back to the main drive unit, so it could be possible to have the main unit be several smaller modules as well.

It is also possible for a separate J-Drive to be installed as a "backup" if you are willing to waste that kind of money and don't need the space for cargo capacity. Does that mean you can buy two type A J-Drives and link them to make an equivalent of a type C while saving 10 MCr.? As much as it pains me to agree with F33D, I would have to say no; at least for everyday use.

As a part of an adventure, say a Far Trader's J-Drive is destroyed and all they can find in a pair of derelict Seeker Mining Ships to scavenge for parts. Could the players link the two drives to give them enough jump capacity to get back to a repair yard? In my opinion, yes. There would be a fairly lengthy Task Chain to get them installed and linked and I would impose a negative DM for the jerry-rigged system, but I would let them do it.
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Re: Jump Bubble diameter and location of Jump Drive

Postby CosmicGamer » Tue Sep 24, 2013 4:22 pm

F33D wrote:I could go on ad infinitive about all the things the rules don't say one CAN'T do but. But, I'm logical and won't go down that nutty rabbit hole.
And I could go on ad infinitive about all the things the rules don't say one CAN do but....
-------------------
Ok, searching on grid like I did on bubble: 10 documents... Power grid, mapping grid, communications grid...

Only one reference on topic. In "Sector Fleet" it discusses powering the Jumpgrid but there is no mention of a Jump bubble in this publication. Instead, converting the hydrogen fuel to power for the jumpgrid creates a "J-field". No mention of lanthanum for the grid in this publication either.

There is mention in other pubs of Lanthanum, but not for a grid. For example, in book 9 Library Data
Lanthanum: A rare earth element, the first of the inner
transition metals. It is vital to the construction of the inner coils
of interstellar jump drive units.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Sigtrygg » Tue Sep 24, 2013 5:46 pm

The lanthanum hull grid and zuchai crystals were inventions of the MT authors (DGP). In CT MWM's Jump Space article in JTAS 24 and many library data entries like the quote upthread mention lanthanum used in the drive coils and a grid built into the hull although the exact material used isn't mentioned.

MT gets quoted a lot because of the Starship Operator's Manual, but you have to be careful since MT changed many of the underlying technological assumptions of CT.

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