jump points near star

[MacTrom]

Ok, I have a question:

1) jump points are 100 diameters from the destination planet.
2) the star's gravity well would also prevent too close an approach, right?
3) the Sun is 870,000 miles in diameter: 87,000,000 miles to safe jump
4) planet Earth is 94,000,000 so no problem.
5) trying to jump to Venus would result in either dropping out at the Sun's limit or possible misjump trying to get to Venus' limit.

Is that so?

 

[far-trader]

Correct.

Jumping to Venus (or Mercury) from Earth (or another solar system, or anywhere in fact) will result in the ship being precipitated (my term) from jumpspace at 100 diameters from the Sun because its 100 diameter "shadow" extends beyond the 100 diameter "shadow" of the destination.

There will be no misjump chance.*

Misjumps are only possible upon entering jumpspace. So trying to initiate a jump at 100d of Venus for example would have a chance of misjump since you're still inside the 100d of the Sun.

* Though you could call it a misjump (small m) since you won't come out where you intended to.

That's as the rules stand. Personal tastes are another matter and strictly non-canon but not wrong

 

[Supplement Four]

2) the star's gravity well would also prevent too close an approach, right?
3) the Sun is 870,000 miles in diameter: 87,000,000 miles to safe jump
4) planet Earth is 94,000,000 so no problem.
5) trying to jump to Venus would result in either dropping out at the Sun's limit or possible misjump trying to get to Venus' limit.

Is that so?

That is correct. It's called jump masking. Certain areas of a system are masked by the star's gravity limit.

In Traveller, though, it's mostly ignored because its so hard to calculate (you don't always have the star's diameter and the distances of the world from the star at hand during a game).

It's a concept that's been around since the early CT days. I understand some of the GURPS Traveller books addressed this issue a bit.

Today, though, all you need to do is get a copy of the excellent Heaven & Earth program. Click here: http://www.downport.com/wbd/HEAVEN_&_EARTH.htm

Now, before you game, simply run the program on the system you are using. You can enter UWPs if you're using a world of your own creation, but the program also has several canonical sectors.

Have the program generate the entire system (takes a few seconds), and then, boom, you have all the info you need. Local gravity. Local temperature. Distance from the star.

The program will even map out the system for you, and you can eyeball the star's masked area.

Simply do this for every world your players are likely to visit (takes no time at all), and keep your print outs in your GM's notebook. You'll have anything you need to know about a system your players are visiting in a pinch.

I typically print out the entire subsector when I'm running a Traveller game. That way, I'll I have to do is flip to the correct page if my players go off on some unbeaten path I haven't prepared.

 

[rancke]

That is correct. It's called jump masking. Certain areas of a system are masked by the star's gravity limit.

There are two different versions. One is when a world is inside a star's jump limit. The other is when a target is outside any jump limit, but there's a jump limit of some sort in between you and the target. Both are often known as jump masking. Some of us try to distinguish by calling the first version jump shadowing (the world is permanently in the shadow of the star (or gas giant)) and reserve jump masking for the second version.

It's a concept that's been around since the early CT days. I understand some of the GURPS Traveller books addressed this issue a bit.

The concept of jump shadowing has been around since CT. The concept of jump masking was never explicitly mentioned or used in any rules or adventures until GURPS Traveller, but Marc Miller says it was his intention from the start.


Hans

 

[aramis]

Funny, Hans, but Some of us use the terms in the opposite manner... like everyone I've played with.

Jump Shadow being the intervening object, and masking being the terminal points being within the limit.

Of course, that has to do with reading SW novels, I suspect.

In practice, tho', the two terms are mostly synonymous.

Me, I do terminal mass effects only, both ends, but not intervening items.

 

[Supplement Four]

There are two different versions. One is when a world is inside a star's jump limit. The other is when a target is outside any jump limit, but there's a jump limit of some sort in between you and the target. Both are often known as jump masking. Some of us try to distinguish by calling the first version jump shadowing (the world is permanently in the shadow of the star (or gas giant)) and reserve jump masking for the second version.

I've heard that before. (Heck, I think you've said that to me before!)

But...I just don't get the second idea you mention--when there's a jump limit between you and the target world.

Say you're on Planet A, and you want to jump to the other side of the system, to Planet B, where Planet B is on the other side of the star (effectively masked/shadowed by the star's field).

Sure, massive bodies have a gravitational reflection in Jump Space, but line of sight should not matter! The J-Drive works by opening a hole to another dimension.

If Planet B, in the example above, is not within the 100 diam limit of the star, then there should be no issue.

If line of sight were an issue, then there'd be a lot more ticks involved with a vessel doing a 3 parsec (or even a 6 parsec) jump.

 

[Supplement Four]

The concept of jump shadowing has been around since CT. The concept of jump masking was never explicitly mentioned or used in any rules or adventures until GURPS Traveller, but Marc Miller says it was his intention from the start.

BTW, I'll have to find it, but I do think I have a magazine article around here somewhere from the CT era that discusses jump masking. It might have been from White Dwarf or one of the other Trav mags...I'll see if I can find it.