IMTU, I've made alterations to how things work down in Engineering. It may seem heretical to mess around with the rules regarding a ship's drives, but it's something that I think isn't too uncommon among GM's in Traveller.
I use the Proportional Jump Drive IMTU. Ships with jump drives
capable of going longer distances can cover shorter distances in proportionally
less time. For example, a jump-2 ship can travel one parsec in half a week.
When I first read my Traveller book way in the beginning of the 80's, I interpreted the jump rules this way. It wasn't until later that it was made clear to me that all jumps were supposed to take 1 week, no matter what. It seemed to make more sense the other way to me (and anyone else I played Traveller with), so I stuck with it. Of course since CT, the explanation for how a jump drive works has changed and become more detailed, but I haven't read anything that has convinced me to change.
I think commerce in Traveller becomes a bit more practical if you can have courier ships capable of delivering small cargos within 48 hours as opposed to a week. If a J-6 ship is going to take as long as a J-1 ship to get somewhere, why invest in the larger jump drives? The J-1 ships don't become obsolete because they have alot more room for cargo (compared to ships of equal displacement) and cost alot less.
I'm not alone on this one as I've seen variations posted elsewhere.
Mini-Jumps: Applying the proportional jump idea to in-system jumps, we get even smaller jump times. I've dubbed them mini-jumps. Jump-1 is about 170 times the speed of light or 31,617,000 miles/sec. ~20 AUs/minute. At this rate, it would take approximately 3 seconds to cover the distance from the sun to the Earth, which is 1 AU. As such I've made this the minimum distance that can be covered by a mini-jump.
I've since added that these short transits put stress on the jump drive. You can add misjump DMs, drive failure DMs, and/or increases to annual maintenance costs. Adding 1% of the cost of jump drive per mini-jump to the bill is a good start.
The orbital distances between worlds are listed in the main rule books for all versions of Traveller. Now if it just so happens that the departure world and the destination world are in alignment, your transit time calculation will be easy. If not, well you've got a bit more work to do. And be sure to avoid the star's gravity well. Whether or not you adjust for density, you'll still need to keep it in mind.
Fuel consumption for the proportional jump drive and mini-jumps is up to you. Each edition has changed its formula for calculating out jump fuel requirements so use whichever version you prefer. I have the fuel consumed proportionally, of course, for normal jumps. For mini-jumps, I calculate the jump-1 fuel requirement and then assign either 25%, 50%, or 75% of that value to the fuel consumed during the mini-jump performed, based on how far the the ship is traveling in-system. I guess I could split hairs further, but that would just be more work.
I use HEPlaR but I'm unhappy that there are no improvements to the technology
after it's been introduced at TL10. One would think that by TL15 some
improvements would have been made. Or possibly a different kind of maneuver
drive would be introduced (I'd prefer not to break the laws of physics by using
Thruster plates). When I posed this problem to the TNE mailing list, a gearhead
came back with, "HEPlaR is already insanely efficient." While I've always
respected this person, I have to say I think he missed my point. HEPlaR may
indeed be "insanely efficient" by real world standards, but I'm playing
a game. HEPlaR is dragging me down with its lack of technological advancement.
So, I've sparked things up a bit by introducing increased efficiencies with
tech level advancement. What comes after insanely efficient?
TP: Thrust to Power ratio. Units: Tonnes of thrust per MW
FC: Fuel Consumption. Units: Cubic Meters per hour per MW
These small increases may not seem like much but they add up. If I'm calculating
this correctly, using these factors, a TL-15 ship would require 36% less fuel
to maneuver than a TL-10 ship trying to achieve the same performance. I think
the factors provide a reasonable advantage for TL-15 over TL-10 without getting
The improved Thrust to Power ratio also means a smaller HEPlaR drive recombustion chamber is required to achieve the same results.
The Ambiguous Maneuver Drive (AMD): For those of you who want to convert to HEPlaR but can't stomach the fuel economy, try this one. With a nod towards the vagueness of the CT days, the AMD details are intentionally left undefined. The important point is learning how to deal with a limited fuel supply. Consider it HEPlaR with training wheels. Gone is the month long free lunch of thruster plates. It's time to start dieting.
Design specs are CT or MT or even TNE. Your choice. However, the fuel consumption is as follows:
Fuel is consumed at the rate of 1 ton/day per G of acceleration times the displacement of the hull divided by 100. Algebraically, that looks like....
Fc = 1 ton/day * a * (V/100)
where Fc is the fuel consumption rate, a is the acceleration of the ship in G's, and V is the displacement of the hull.
So a 400 ton ship accelerating at 4G (like a Type T Patrol Cruiser) would consume fuel at a rate of 16 tons/day, rather than the CT/MT rate of 10 tons/week. On that same tank of gas, the ship would last 2 1/3 days full throttle. A far cry from 30 days. And it still has longer range than HEPlaR. That same ship in TNE would be good for 15 hours full throttle before having to dip into the jump drive portion of the fuel.
The AMD is somewhere between the two "extremes." It's not as restraining as TNE. You can actually travel interplanetary distances in a reasonable amount of time without always having to rely on your jump drive. But it's not nearly as goofy as CT/MT. You can actually run out of gas.
But if that's still too much, swap out the 1 ton/day multiplier with 2 tons/day (1 ton/12 hours) or 3 tons/day (1 ton/8 hours) until you get something that works for you.
Nothing special here. I use the MT rules here. TNE didn't include any economy of scale factors. Maybe they thought that fusion power plants were already insanely efficient. ;)
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