I had figured that TomR's example was a J4 fabricated in the 3I using current tech-max. However you are correct in that if it was a 'relict' drive fabricated centuries ago when the 3I's tech-max was lower, then it should be limited to J4 under all circumstances. This would also be true if the drive was fabricated outside the 3I (Vargr-land?) where the max-TL is lower. However, it's always been understood that higher TL is generally almost always avail but just at a higher price. There's also the question of whether 'older' J-drives can be 'upgraded' to current T-Max levels. I don't think that's ever been discussed. So, I guess my answer must now be amended by this;

"It also depends on the T-Max of the era in which the J-drive was fabricated & what TL it was fabricated at."

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On Sunday, October 6, 2019, 12:56:13 PM MST, Ethan McKinney <xxxxxx@gmail.com> wrote:


From 3I history, max jump distance is strictly limited by Tech Level. At the time of the First Interstellar War, the Ziru Sirka (First Imperium) and the Solomani Confederation were strictly limited to Jump-2. Cramming big jump drives into small ships just didn't matter.

The Terran development of the J-3 drive was one of the daggers in the heart of the First Imperium.

On Sun, Oct 6, 2019 at 12:18 PM Cian Witherspoon <xxxxxx@gmail.com> wrote:
Looking at the LBB gives an interesting perspective, since the “standard” drives in there don’t have a TL limit on potential (just a cap of J6), but do have one on drive size. This means that you can take the highest potential JN and multiply it by that hull size/100 to create a “real potential range” number for that particular drive model (or just divide tonnage by 100 and multiply by jump number if you’re doing this for individual ships), and then divide that by the actual hull size you’re installing the drive in to get that configurations jump number.
You can also do this for M-drives, to get tons of thrust for a drive model.
High Guard introduced “Jump potential by TL”, but it sort of implies, in the context of HG vs LBB2, that this applies only to custom military jump drives.
Looking at Tom’s example, j4 for 400 tons would be potential 16, and when installed in a 300 ton hull would give J5.33.

On Sun, Oct 6, 2019 at 11:49 Phil Pugliese (via tml list) <xxxxxx@simplelists.com> wrote:
As I recall, in the original trio of LBB's, you selected a jump drive by letter (A,B, etc) from a table that was cross-ref'd with hull sizes to yield a jump value.
Sometimes a change in hull displacement would NOT change the jump value but usually it did.
In the CT HG lbb, the 'tonnage' of the JD was calculated as a % of the hull size modified by the max J desired, so if the ship's displacement was modified (re: Gazelle CE or in the case of retaining external demountable tanks) then J was also altered. (NOTE: *internal* demountable tanks does NOT change J MAX)

I would say then that the answer is 'Yes'.

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On Sunday, October 6, 2019, 11:15:01 AM MST, Thomas RUX <xxxxxx@comcast.net> wrote:


Hello all,


Back in when I picked up Traveller my impression, which was reinforced by the GM, has been that a J4 drive has a maximum range of four parsecs regardless of the hull size that it is installed in.


Can a J4 drive built for a 400 ton hull allow a 300 ton hull to make a five parsec jump?


Tom Rux

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