100 diameter rule

[cbrunish]

Does the 100 diameter rule pertain to just heavenly bodies or both man made and heavenly bodies. What I mean is that would a ship need to be 100 diameters away from another ship before it jumped?

Was thinking of a Battlestar Galactica episode where Boomer jumped within the Galactica and caused damage to the Galactica. Wouldn't something like this happen in Traveller (and would have destroyed the ship Boomer was in).

 

[andrew boulton]

Yup, it applies to everything. Objects smaller than the ship usually won't affect it, but may be sucked into jump or ripped apart. Objects larger than the ship may cause a misjump.

 

[rust]

Does the 100 diameter rule pertain to just heavenly bodies or both man made and heavenly bodies. What I mean is that would a ship need to be 100 diameters away from another ship before it jumped?

As far as I know, the rule only pertains to heavenly bodies, I do not re-
member any mention of a 100 diameter rule for other objects.

Was thinking of a Battlestar Galactica episode where Boomer jumped within the Galactica and caused damage to the Galactica. Wouldn't something like this happen in Traveller (and would have destroyed the ship Boomer was in).

I am not sure how to handle this.

My guess would be that it is not possible to create a jump bubble insi-
de another ship or structure, because there would not be enough emp-
ty space around the smaller ship for this jump bubble, and that there-
fore a jump from inside a ship or structure would normally not be pos-
sible - the drive would just not work.

 

[rinku]

Can't see why not. However, ships are pretty small. You'd only need to be a couple of kilometers away from a Type S, and at most a few tens of kms from even the largest ships. That's maybe one turn of space combat? But you could be in a position of not being able to run with other ships about to board.

In the case of jumping from within another ship... I'd treat that as if you were jumping from within an atmosphere. Technically possible, but suicidally dangerous. Of course, if you were facing certain death anyway...

Basically, it would be an automatic misjump. At best.

EDIT:
Actually, using the original rules, you're automatically destroyed if you attempt a jump within 10 diameters. But the new set allows for the effects of the engineer check and doesn't have that lower limit - it is plausible for a truly heroic and lucky engineer to offset even worse DMs than -8.

Maybe double the penalty to -16?

 

[BP]

Core pg 141, states, 'A ship can only safely jump when it is more than one hundred diameters distant from any object.'

For ships that ain't chasing, that ain't much. Diameter should have been defined (i.e. of sphere fully encompassing object), so assuming longest length: 400-ton ships are generally under 100m - so, only 1 combat round; any ship over 100m and less than 12.5 km, would require short range.

If minutes are important, combat round range changes are estimates -do the math, instead.

('Course, one could also play by one's own rules here! I don't go with all the Jump details myself.)

 

[rinku]

IMHO the diameter rule was only ever a useful simplification. Gravity has always been given as the thing that makes jumping dangerous, which means mass density of the body in question is important. MGT extends the 100 diameter rule to stars... but that means Earth orbits just on the edge of the Sun's 100 diameter limit. But since the sun's density is much lower, the gravitational strength at that distance is much lower than the Earth's is at 100 earth-diameters. (I haven't done the calculations yet, though).

For ships, I think the best rule of thumb would be to apply the -8 penalty if there are any other ships within close range or less. If the ship were a monster battleship, maybe make that Short range as well.

Oh, and the 800 ton Merc Cruiser (handily, a sphere) has a diameter of about 24m, giving a 100-diameter of 2.4km. The Type-S Scout (1/8th the size) has a long axis of about 30m. But I think you'd be hard pressed to argue that you have to be further away from a 100 ton ship than an 800 ton ship!

 

[rust]

I still think that the "any object" rule is an error, simply because I did
not find any mention of it in any of the previous versions of Traveller
I have here.

At least two of these versions, MegaTraveller and Traveller New Era,
include detailed "flowcharts" for interstellar travel (getting into orbit,
getting to the 10 diameter distance from the planet, getting to the 100
diameter distance from the planet ...), but none of them mentions any
other objects besides the world itself and its star.

GURPS Traveller explains the "jump shadow" problem when a world's
100 diameter distance is still within the 100 diameter sphere of the star
(because the world is in a close orbit around a massive star), but also
mentions no other objects as potential problems.

 

[Nuclear Fridge Magnet]

The opening sequence of the old boxed module Tarsus featured this.

The players arrive aboard a Type M Liner at Tarsus... outside the star's 100-diameter limit, not the planet's limit.
It's a long cruise in at 1-G, with a glorious red-giant 'sunset' effect.

 

[rinku]

I had a look back at various old products, and Scouts explicitly mentions 100 diameter jump limits for stars (and has the tables to allow this to be worked out.)

Also, if you go back to Book 2 and use the formulas there to work out what the gravity is at the 100 diameter limit for the various normal planets, it becomes apparent that the larger the mass, the higher the gravity.

According to my workings, the gravity from a size 8 planet with density 1.00 at 100 diameters should be 1/40,000th of a G.

A size 4 planet with density 1.00 would exert 1/80,000th of a G at 100 diameters.

So, I guess I stand corrected and in most cases inner system planets will require a longer journey. However, in YTU you may wish to use a particular gravity gradient instead of the 100 diameter rule.