GT: Far Trader: Jump Masking

[chrisr]

Is there any mention of mass, gravity wells or tidal forces in any of the explanations of jump or jump precipitation from canon or MWM?
What about a zero-mass 'particle' that eminates from an object of sufficient size and causes a shadow in jump-space out to 100D. It would have no effect in normal space, but causes precipitation from jump when in jump space.

 

[daryen]

Hey! I know!

It's all volume based. It's the object's volume that screws with jump space, not its mass, gravity, or tidal forces.

I mean its operation is influenced by volume, not mass anyway. It doesn't matter what the mass of that 100 dTon ship is, it still takes a fixed amount of machinery and hydrogen to jump.

So why wouldn't its limitations be volume based, too?

 

[Springstead]

It would seem, from my current understanding, that gravity in realspace affects a ship entering jump, but not leaving jump. leaving jump is effected by gravity and other factors as they apply IN jump space, where the laws governing their functions are different.
It appears the "jump space" is a kind of alternate space which maps to "real space", but the laws governing jump space are different, affecting scale and distance and time.

 

[Malenfant]

I give up. Between the discussion here and on the T5 board (given we have sod-all to playtest), I've had quite enough of this topic now. As far as I'm concerned, tying it to gravity strength is more than good enough for me. That's what I'd do.

If other people want to come up with wacky explanations for how its based on volume or some weird particle or cosmic strings or armwavy magic then have fun with that

. But just say that instead of trying to make it sound like it's actually based on something realistic when it isn't.

 

[TheEngineer]

Hi !

ChrisR:
Well, the "disturbing effects of gravity" are mentioned in the MT and TNE rulesets, and in the perhaps well known JTAS Jumpspace article.
Anyway, the detailed nature of these effects is not noted AFAIK but the 100D thing is described as "a over the tumb" method explicitly.
Most of the rest is interpretation/speculation

 

[robject]

I rather like Malenfant's mass tables, though I admit my disbelief-suspenders only get snapped when it comes to stars.

As someone else hinted at earlier, I'd probably retool the charts to assume one Earth mass yields a Terran 100D limit.

But then, it looks like that makes the stellar jump distance prohibitively large. I must be doing something wrong.

Alternately, I'd keep the 100D limit for planets, and rely on mass tables for stars. Glancing over the table, it seems that temperature implies jump distance... O = 3 AU, B = 2 AU, A & F = 1 AU, G = 0.75 AU, K = 0.67 AU, M = 0.33 AU...

 

[Malenfant]

...or just use the mass tables as they are. I mean, personally I think tables are much easier to use than having to calculate 100D limits for everything.

 

[robject]

Hmmmm. That's a good point. Would have to have a table anyway to calculate the travel time required.

 

[Jamus]

/agree

 

[robject]

I've compromised and produced an Abomination: a hybrid table that uses diameter for planets, and mass for stars. The result is a decently seamless table.

Jump limits table

 

[Malenfant]

What are the 1G-6G numbers? Travel time from where to where? And is the jump limit determined by the radius at which gravity is at 0.01m/s2?

And why did you use diameter for the planets instead of mass? What is the purpose of using two different systems to figure out the limit at the same time - you're right, that's an abomination, the worst of both worlds. Either use mass for everything, or use diameter for everything - don't mix them.

 

[Anthony]

If you want remotely compatible results between the classic 100D limit and anything mass-based, you have to base the jump limit on the cube root of mass. Fortunately, that's actually physically meaningful, as it's the distance at which the tidal effect exceeds some critical value.

 

[Malenfant]

You know Anthony, that's always bugged me - is GM/r^3 actually a real, meaningful quantity? It's just that I've never seen it used anywhere - all the tidal equations I've seen are vastly more complicated than that. AFAICT it's just the differential of GM/R^2 (missing a constant somewhere) isn't it?

Or is that not how your "tidal limit" is calculated?

 

[Anthony]

http://en.wikipedia.org/wiki/Roche_limit has a concrete example of this formula in use.

And yes, it's the differential of GM/r^2

 

[Malenfant]

Ah, interesting. I'm familiar with the formula to calculate the roche limit, just not the intervening steps for how to get it

But doesn't the formula there require that you know how big the ship is (the 'r' term) and also a mass (m) 'on' the ship that is to be perturbed?

 

[Anthony]

You'll note that for constant density objects the roche limit is independent of the size and mass of the satellite, because the force ripping a satellite apart is proportional to m*r, and the force holding the satellite together is also proportional to m*r. Presumably the jump bubble works in the same way.

 

[TheEngineer]

Just to add:
Here
http://de.wikipedia.org/wiki/Gezeitenkraft
is the derivation of the tidal force itself.
Text is in German, but the formulars cross language borders, I guess

 

[kaladorn]

Originally posted by RainOfSteel:
If only one person needs to be convinced of anything, and that person won't change their mind about anything, then there is no reason to run a playtest of T5.

Agreed. But there is a world of difference between 'not change their mind about anything' and 'not change their mind about this thing'.

Castlebravo hits on the head the reason that the limit exists in the first places. Many games that don't have this kind of limit (or jump points) have real underlying issues with how the universe works since fleets would pounce on planets with ease. So we need this sort of limit (jump bombs mostly go away... if only we had an equally easy remedy for the dreaded near-C rock...).

Tidal forces is about the most reasonable solution I've seen so far, if you don't like the rulebook version. It does seem that even if it was simply a property of matter, it would somehow be related to the density of the matter (as gravity is). Then again, perhaps there is some proprety of matter that is like a binary digit - there is matter at that location, or there is not - and if it is there, it interferes. The problem with this, of course, for those of the community who balk at things they can't at least contrive an explanation for, is that I don't think we have any precedents to suggest how such an interaction might work and it may be problematic from that sense. Sure, it is easy to explain away the ecliptic angles, but this other aspect is a bit tougher.

Tidal forces in many cases would come somewhere close to the 100D limit (at least in examples I looked at last time out, by no means exhaustive).

 

[Jamus]

the trick is to find a happy medium between hard-science and playability<word?> first and formost Traveller should be fun and sadly for most people doing advanced mathematics is not really fun.

 

[RainOfSteel]

Originally posted by kaladorn:
[...] But there is a world of difference between 'not change their mind about anything' and 'not change their mind about this thing'.

I'd agree. However, until I see a list of those things that won't be changed, where I'm better off spitting into the wind rather than steaming up the place with discussions that won't go anywhere, I'll tend to feel inclined to comment (otherwise I wouldn't be here).

You may have noticed I'd already stopped in large part (on this issue, anyway).