Jump Bubble diameter and location of Jump Drive

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dragoner
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Re: Jump Bubble diameter and location of Jump Drive

Postby dragoner » Tue Sep 24, 2013 5:48 pm

"What is not explicitly permitted is forbidden" is a silly place to be. IIRC, Mongoose author Robert Eaglestone was talking of daisy chaining jump drives in T5, so this isn't a new discussion. Basically it is up to GM fiat to accept or reject the concept.
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Re: Jump Bubble diameter and location of Jump Drive

Postby hdan » Tue Sep 24, 2013 6:10 pm

The rules say nothing about the physical configuration of the drives. However, you can infer (if you like) some things from the formulas implied by the drive size and cost tables.

First, each drive has a 5dt "control room" overhead, which is essentially free, or bundled with the cost of the hull+drive in some way.

Second, each letter corresponds to a number of 5dt jump "units", which costs 10MCr each. Larger hulls require more jump units, but not larger control rooms.

There is no economy of scale in drive cost or size. More capable drives seem to just take more of the 5dt "units" to achieve their effect.

Now of course such a view requires you interpret the data, since as F33D will be happy to point out :), the RAW are silent on the subject, which means the GM is free to improvise.

In my current campaign (which is on hold for a while, but still technically "on") I'm using the trope (from Twilight's Peak) of the Far Trader with "short legs". In this case, the players need to buy a new jump module or repair the old one in some way. Their control room can handle two modules (class B), but one is malfunctioning.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Reynard » Tue Sep 24, 2013 6:51 pm

Is a rabbit hole a form of jump space?
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Re: Jump Bubble diameter and location of Jump Drive

Postby Egil Skallagrimsson » Tue Sep 24, 2013 6:55 pm

Reynard wrote:Is a rabbit hole a form of jump space?
Dunno, you will have to ask Alice that one.
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Tue Sep 24, 2013 7:00 pm

hdan wrote: There is no economy of scale in drive cost or size. More capable drives seem to just take more of the 5dt "units" to achieve their effect.
If you look at drives out of MRB and then compare HG drives for very large ships I think you'll see some economy of scale.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Rikki Tikki Traveller » Tue Sep 24, 2013 7:10 pm

Personally, for MyTU, I like the idea of a spherical Jump Bubble. The jump drive is then located in the center of the ship and ALL FTL capable ships are spheres.

SO, that really changes the composition of a naval fleet with Battle Riders much more likely. It also makes Hi Ports much more common (say Starport Class-C or better always have them) and most smaller ports use shuttle service.

Of course almost none of the "standard" layouts would apply, but since I like designing ships, I wouldn't mind. The Tigress would work though!

You could probably come up with some kind of ship size penalty for a Flattened Sphere design (wasted volume of the jump bubble) and that MIGHT allow a smaller craft to fit within that jump bubble and not be directly connected to the other ship. Referee's decision.

It would likely make the game more like the Humanx Commonwealth of the Flinx stories.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Condottiere » Wed Sep 25, 2013 5:21 am

I like to thank everyone for replying to my questions.

I was considering spherical starships ala early Perry Rhodan,and wondered if you could shrink the jump bubble to hug the hull. If an exterior bulkhead were required, I considered making it a berliner, with the drives still central, but an exhaust port giving it a somewhat semi doughnut structure.
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Re: Jump Bubble diameter and location of Jump Drive

Postby hdan » Wed Sep 25, 2013 7:17 pm

F33D wrote:
hdan wrote: There is no economy of scale in drive cost or size. More capable drives seem to just take more of the 5dt "units" to achieve their effect.
If you look at drives out of MRB and then compare HG drives for very large ships I think you'll see some economy of scale.
Plausible. I only use MRB ship designs.
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Re: Jump Bubble diameter and location of Jump Drive

Postby phavoc » Wed Sep 25, 2013 8:35 pm

F33D wrote:
hdan wrote: There is no economy of scale in drive cost or size. More capable drives seem to just take more of the 5dt "units" to achieve their effect.
If you look at drives out of MRB and then compare HG drives for very large ships I think you'll see some economy of scale.
HG uses a percentage, MRB does not. That's where the discrepancy lies. Personally I believe they should have used the same ship construction rules in both rule books.
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Wed Sep 25, 2013 8:40 pm

phavoc wrote:
HG uses a percentage, MRB does not. That's where the discrepancy lies. Personally I believe they should have used the same ship construction rules in both rule books.
Right. When you use HG once you go above the MRB tonnage charts, drives get smaller for the same performance vs. MRB. You're right. They should have used the same system for everything. Including vehicles.
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Re: Jump Bubble diameter and location of Jump Drive

Postby rje » Thu Sep 26, 2013 2:35 pm

Condottiere wrote:Hi,
Hi Condottiere. The following are the guidelines I use when writing Traveller material.

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

Diameter = (Hull Tons * 13.5 )^1/3 *20 (in meters)

and

For most purposes, a Jump Bubble is about five times the diameter of the average of Length, Width, and Height of the ship and centered on the Jump Drive.

I think of it as: the radius from the jump drive to the end of the ship from which the drive is furthest from. That probably works out to the same thing, since most ships are much longer in one dimension than the other two, but the concept is that the bubble encompasses the ship, and is centered on the jump drive.




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

The diameter varies based on construction of the jump drive and the needs of the ship. If the jump drive is on the extreme end of the ship, the jump bubble will probably be quite large.

The bubble is the default, and cheapest, option. Two other options, Jump Plates, and a Jump Grid, offer tighter hull conformance -- and their own advantages and disadvantages.




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

It may be placed anywhere, but this will affect the bubble size.




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, on the condition that the drives must be identical.

For example, an N2 or NN jump drive consists of two N jump drives. A Z9 drive is nine Z drives.




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

They need to be in contact with the ship during jump, or else they are lost in jumpspace. Whether or not they 'drift' before being lost is unknown to me.
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Re: Jump Bubble diameter and location of Jump Drive

Postby Condottiere » Sat Sep 28, 2013 11:44 am

Seems more rule of thumb since how would the Jump Drive know the dimensions of the ship, as compared to having an installed grid that would tell it exactly?

Among other things that vex me are the Alphabet drives, which I assume are supposed to be commercial off-the-shelf variants, since presumably I could install a higher value one on the starship, and have it jump six parsecs, even if the ship was constructed at a much lower TL. Since jump technology is an equivalent to dweomercraft, I suppose you could restrict it based on the limitations of the software programmes needed for astrogation, whereas you couldn't make that excuse for maneuver drives, where brute force could make them go any speed and passenger safety would be the only constraint, ie inertial compensation available or acceleration couches/tanks.
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Re: Jump Bubble diameter and location of Jump Drive

Postby GypsyComet » Sat Sep 28, 2013 4:36 pm

Condottiere wrote:Among other things that vex me are the Alphabet drives, which I assume are supposed to be commercial off-the-shelf variants, since presumably I could install a higher value one on the starship, and have it jump six parsecs, even if the ship was constructed at a much lower TL. Since jump technology is an equivalent to dweomercraft, I suppose you could restrict it based on the limitations of the software programmes needed for astrogation,
The software and the computer to run it are stated limitations and do have TL thresholds in MGT, so yes.
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Re: Jump Bubble diameter and location of Jump Drive

Postby coldwar » Sun Sep 29, 2013 9:32 pm

1 metre distance from I know i have seen it in T20, believe I have seen it somewhere else to.

In T20 and from what I have seen for CT i think, and Mongoose the jump drive has one external part in all of them, which takes no real mass. This is the jump grid, which I have seen used as small nodes placed around the hull. These make sure that the bubble does encroach on the ship destroying it, or part of it. So, in response to a ship that has a breach, the simple answer is not really unless you want a major misjump or complete destruction. However, one can simply re grid the jump grid around the ship so that it takes in account of missing grid nodes and prevents it from misjumps.

You can potentially exit the ship and stay with in the 1 metre zone, but you'd be having to look at the hull at all times. This would be true for what I have seen that mongoose has put of a hydrogen bubble. Because the person would still have to be in a Vacc suit. Though that would be something worthy of debate on if that is safe.
But in general, I wouldn't advise it. Too many risks involved. Cramped space, constant evasion of looking at something that will make you either sick or insane or worse. As well as normal EVA troubles. Would be very high pressured on whoever did try it so to speak.
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Re: Jump Bubble diameter and location of Jump Drive

Postby locarno24 » Wed Oct 02, 2013 9:01 am

You can potentially exit the ship and stay with in the 1 metre zone, but you'd be having to look at the hull at all times. This would be true for what I have seen that mongoose has put of a hydrogen bubble. Because the person would still have to be in a Vacc suit. Though that would be something worthy of debate on if that is safe.
But in general, I wouldn't advise it. Too many risks involved. Cramped space, constant evasion of looking at something that will make you either sick or insane or worse. As well as normal EVA troubles. Would be very high pressured on whoever did try it so to speak.
Not really.
Traveller Player Guide - see www.mongoosepublishing.com/pdf/travpg.pdf‎ wrote:I Go Outside!
Player characters being player characters, it is entirely likely that they will somehow end up outside a starship during a Jump. They die.
Horribly.
A merciful Referee might rule that a character standing on the outside of a ship as it Jumps is stranded in normal space but otherwise healthy. Opening the airlocks while in a Jump bubble is suicidal.
Understand that I'm not advocating violence.
I'm just saying that it's highly effective and I strongly recommend using it.
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Re: Jump Bubble diameter and location of Jump Drive

Postby rje » Wed Oct 02, 2013 4:10 pm

Condottiere wrote:... how would the Jump Drive know the dimensions of the ship, as compared to having an installed grid that would tell it exactly?
That is an unanswerable question that I have seen asked before. Magic?
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Wed Oct 02, 2013 4:27 pm

Condottiere wrote:Seems more rule of thumb since how would the Jump Drive know the dimensions of the ship, as compared to having an installed grid that would tell it exactly?
It could well be part of the software. It gets programmed in. Simple.
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Re: Jump Bubble diameter and location of Jump Drive

Postby phavoc » Fri Oct 04, 2013 12:54 am

Keep in mind the old 1 meter distance from the hull to the jump field was put forth when ships had a lanthanum grid in their hull to generate the drive field. MGT changed that with the jump bubble filled with hydrogen.

I'm not sure how opening the airlocks would equate to suicide though.
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Re: Jump Bubble diameter and location of Jump Drive

Postby F33D » Fri Oct 04, 2013 2:52 am

phavoc wrote: I'm not sure how opening the airlocks would equate to suicide though.
Since it wouldn't be from the Hydrogen, it must be some energy around the ship while in jump.
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Re: Jump Bubble diameter and location of Jump Drive

Postby GypsyComet » Fri Oct 04, 2013 3:41 am

The physics beyond the bubble is lethal to human life, but it may take the combination of the bubble and the hull to completely protect life.

Idea: the physics of jump space are somewhat Boyle's Law like. The more you compress J-Space away from the hull, the more energy it has and the more weirdness it radiates through the bubble. The large bubble is just as unsafe to life as the smaller fields a meter off the hull.
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