Jump distance details

[whartung]

That's my realization when I read Interstellar Wars.

Because if it was calculated on actual distance, jump factor one starships, if correctly positioned, can skip over an intervening hex.

Right, and that's "Jump 2", not "Jump 1".

It's just a nuance of the alternate reality of jump space.

One could argue that the star map JUST SO HAPPENS to look like a hex grid because of jump mechanics. Maybe jump space projects star systems down on to a flat plane and round them up in to single "hex" like bees in a hive. It's not a map of the stars, it's a JUMP map of the stars.

The stars really ARE in a 3D space, but the nature of jump only worries about 2 dimensions.

If, in the end, you want to put stars in places other than the center of the hexes, that's fine, but that's just going to limit Jump 1 even more, as there will no doubt be more > 1 parsec gaps in space than their are now.

No matter how you measure it, Jump 1 can't go more than 1 parsec, so there's "no way" for it to "skip" a hex.

 

[Condottiere]

1. Which is why it works as an abstract concept, not when you actually measure the potential distances involved.

2. The other aspect to consider is fuel consumption; rules make it clear it's a minimum of ten percent, but after that it's its an additional one percent per mini hex.

3. As an extreme example, the hex's star system is hugging the edge of it's hex, and the starship just accelerates to over the border, and jumps from the now crossed hex six light years to the edge of the now adjacent hex.

 

[whartung]

If you want to make it more granular.

Divide the hex into seven sub hexes; the subdivide the sub hexes into seven mini hexes.

That ought to give you about nine or ten mini hexes to cross a hex.

3. As an extreme example, the hex's star system is hugging the edge of it's hex, and the starship just accelerates to over the border, and jumps from the now crossed hex six light years to the edge of the now adjacent hex.

To cross a single "mini" hex (i.e. 1/10th of a hex, 1/10 of a parsec), at 1G, is 1.1 years of travel. At 6G, it's just under 6 months.

Jump early, jump often.

 

[mike wightman]

In Traveller lore the Terrans originally used their jump drive for insystem jumps to speed up travel around the outer solar system.

Both the Vilani and Terran early jump drives were severely limited in range and extra fuel use, again according to a variety of canon sources.

Now for a bit of a retcon to a retcon. If our current theories of the Oort cloud prove to be correct, and the weight of evidence points to the models being correct even if we have yet to observe an Oort object, then our Oort cloud could extend for nearly three light years.

The original interstellar trip to Barnard's Star could be made by a series of jumps to build up fuel supplies in the Oort cloud and then a jump across to the Barnard's Star Oort cloud, and back again building up a fuel reserve there so that further jumps into the Barnard System can be made.

This could explain the length of time the original interstellar mission took...

 

[Condottiere]

1. I believe that's where Interstllar Wars came up with factor zero jump drives, which I'll assume is meant to be technological level 9.0.

2. As regards gaming the jump drive, you tuck the star system in the farthest corner of the hex, and Proxy Pluto becomes Tijuana. You fill up a fifty five percent fuel tank, and jump from one edge of a hex to the farthest edge of the adjacent hex, accelerate over the border, and repeat, which in about six weeks moves you twelve parsecs with a factor one jump drive.

 

[kilemall]

In Traveller lore the Terrans originally used their jump drive for insystem jumps to speed up travel around the outer solar system.

Both the Vilani and Terran early jump drives were severely limited in range and extra fuel use, again according to a variety of canon sources.

Now for a bit of a retcon to a retcon. If our current theories of the Oort cloud prove to be correct, and the weight of evidence points to the models being correct even if we have yet to observe an Oort object, then our Oort cloud could extend for nearly three light years.

The original interstellar trip to Barnard's Star could be made by a series of jumps to build up fuel supplies in the Oort cloud and then a jump across to the Barnard's Star Oort cloud, and back again building up a fuel reserve there so that further jumps into the Barnard System can be made.

This could explain the length of time the original interstellar mission took...

IMTU I am at CT/HG TL10, so J-1 only. The Oort Cloud looms large as a major refuel resource getting to the Centauris or Barnard's Star. It's the home of the Starman's Ice Cathedral, the infamous Faust Station, and many many illegal/illicit/immoral organizations, facilities and activities.

 

[Condottiere]

Since factor zero and factor one are both technological level nine, there's no real advantage at skipping around at a quarter parsec, since you still use the same amount of energy and fuel per jump, other wise it might be worthwhile constructing short jump bridges.

 

[BRover]

Here is something I've added to MTU to make Jumping a little more challenging and hopefully interesting. It requires extra calculations and bookkeeping, so is maybe mostly of interest to gear heads, but others might like it too.

Jump Distances.

The distances between stars on Traveller maps is always in Parsecs. Jump Drive ratings are in parsecs. Very useful for keeping things simple. But simple can be boring, and not very realistic.

So, I was implementing the Primitive and Advanced Spacecraft rules from Chapter 4 of Mongoose Traveller 2nd Ed. when it occurred to me that it would make sense for the Jump Drives to gain a small distance increase at higher tech. For example J2 drives become available at tech 11, but wouldn't a tech 14 J2 have a slightly better range than a tech 11 J2?
As I said, this is just a detail for those that like details.
Say the tech 14 J2 drive's actual range is 2.3 parsecs. That fits the idea, but the map still only shows jump distances as absolute Parsecs. So, for this idea to be meaningful, one must have jump distances between systems vary a bit from the simple Parsec model.
What I do is when someone wants to decide on whether to jump somewhere I roll dice for the accuracy of the map distance. The actual distance can be up to 0.5 Parsecs off compared to the distance shown on the map. Roll 2 dice, subtract 7, use the result as tenth of parsec distance adjustment for the distance between those two stars. Once you roll for the specific distance between a particular pair of stars write it down and use that same distance going forward for all jumps between those stars. . . .

If you want to make it more granular.

Divide the hex into seven sub hexes; the subdivide the sub hexes into seven mini hexes.

That ought to give you about nine or ten mini hexes to cross a hex.

Of course, now you need to place everything within the hex into where they'd be in the mini hexes.

That would kinda fit into my supposition that it's jump factor plus a quarter, or you can be generous and say ten mini hexes per jump factor, plus three.

And you can squeeze a jump factor four out of a hundred tonne hull.

Of course, if you are going to go to that sort of detail, you could include the "Pythagorean Theory" as adapted to a hex grid. You likely know, on a square lattice, the distance between two points is the square root of the sum of the squares of the x and y distances (d^2 = x^2 + y^2).

Hexes have a similar formula. If you go x hexes in one direction, turn 60 degrees and go y hexes more, then the final distance fits d^2 = x^2 + xy + y^2. So, go 3 hexes in a straight line, (x=3, y=0), final distance = 3 pc. Go in a 3-hex dogleg, (x=2, y=1), d^2 = 4+2+1, d = √7 = 2.64... pc.

And so on. It turns out that, anything up to 6 hexes away will be over 5 parsecs straight line. 7 hexes will be over 6 parsecs. However, at 8 hexes, (4,4) and (5,3) are √48 = 6.928... and √49 = 7.00 parsecs, so a Jump 7 drive could make these jumps . . .

Yaskrodray had a thing about hexes and 6. Was this part of the reason?

 

[Straybow]

Jump-1 is 1 parsec. That's it. Not 1.1. Up to 1 parsec.

One of the most interesting characteristics of the Traveller Universe, is not only is it FLAT, all of the systems live in the center of their hexes. Just what are the odds of that, but it shows it's just another one of the great mysteries that reflects on the power of the Ancients and their OCD nature. They squashed the galaxy flat while scattering Man across the stars.

If you want to map the J drive in to a more realistic astrographic situation, then J1 drives can STILL only jump 1 parsec. Need 1.1 parsec? Then either jump twice, or get a J2 drive.

The ships designs will adapt to such a universe, not the J drive. If most systems are 2-3 parsecs apart, then you'll have a bunch of J1 ships with a lot of fuel to make the extra jumps. Just the way it is.

That may be true of OTU, but this is MadmaxTU. The ancients didn't turn the galaxy flat or thread a non-Euclidean topology through a number of known stars. It's just an abstract map, by what Madmax is describing.


In that case, yes, J1 can be what MadmaxTU needs it to be. Maybe it is 1.23456789 pc (because it's fun) or 1.5 pc (designed by an unimaginative engineer) or 1.616 pc (the golden ratio for the artistic types).

 

[AtlanticFriend]

I actually meant in real life practicality.

I was wondering if I could game the system, assuming the jump numbers can be rounded up, which means factor one would 1.49 parsecs.

I wonder if that would correct the "Solomani get the news about the Rebellion" conundrum explored in another thread?

 

[sudnadja]

That's my realization when I read Interstellar Wars.

Because if it was calculated on actual distance, jump factor one starships, if correctly positioned, can skip over an intervening hex.

I don't think that's what Interstellar Wars was saying. In IW, a rogue planet or some other interstellar mass was found that acted as a bridge between Sol and Barnard. No "hex" was jumped over, they spent a lot of time building up a fuel depot at that interstellar mass and finally did the 2x Jump-1s to go from Sol to Barnard.

 

[Condottiere]

The real issue is how you can game the system.

It could be that you need some form of a substantial gravitational well to jump into a hex, but this would be more driving over the border of the hex, and jumping from that border to the furthest one away, and then driving over that as well.

Rinse, repeat.

 

[sudnadja]

The real issue is how you can game the system.

It could be that you need some form of a substantial gravitational well to jump into a hex, but this would be more driving over the border of the hex, and jumping from that border to the furthest one away, and then driving over that as well.

Rinse, repeat.

In other words, this would be a valid jump?


The downside is the time it takes to get from the center of the hex to the edge of it, around 23.6 years with a T5 M-1 drive (from a sun-like star). (check that: 195 years if you presume only 15 days of M-drive fuel available)

 

[Condottiere]

Not quite.

You can jump from anywhere within one hex to anywhere within another hex within range of your jump drive.

 

[sudnadja]

As "within range" does mean 1 parsec for Jump-1, I think it fits without problems. Sol-Alpha Centauri would still be two jumps, even though Alpha Centauri is really just one hex over:

As you would have to jump from the center of the Sol hex in the direction of Alpha Centauri and would then have to complete the jump within hex to Alpha Centauri.

 

[Condottiere]

You have to specifically crossover the boundary of the Sol Hex at North East, in this case to the empty hex attached to it, if one metre would be considered sufficient for the game system, or some further distance.

Having crossed the border, you are now in a hex adjacent to Prometheus, Peraspera and Junction, which would be within range of a factor one jump drive, and you can now jump anywhere in these three hexes, whether the furthest shore or straight to the next habitable planet(s) within their respective systems.