Jump effects?

[far-trader]

I prefer the simpler (but less dramatic) nothing happens when you attempt to jump from a planet surface.

The power plant charges the capacitors to power the jump drive. The jump drive converts some of the hydrogen into power to charge the jump grid in the hull. The planetary gravity prevents the opening to jump space from forming. The ship just sits there as the remaining hydrogen is vented around the ship.

The hydrogen venting is a fire hazzard, but that is all.
Just my opinion.

I think I prefer this as well. It's so much simpler to say that the jump drive just doesn't work in a gravity well.



Pity the poor deckhand popping out for a cigarette.

Yep, that's not bad either. I (probably) would not even go so far as the hydrogen (super cooled liquid hydrogen remember) venting under that scenario. Rather than worrying about somebody lighting up a cancer stick I'd be worried about flash freezing them. If it came off as a gas it'd rise pretty quick in standard atmo and be "mostly harmless".

But the question then becomes the old issue of is it gravity that interferes though? Remember it is "diameters" not "Gs" that mess up jumps. The gravity sitting on the downport of a size 1 world is much different than sitting on the downport of a size 9 world.

 

[Valarian]

But the question then becomes the old issue of is it gravity that interferes though? Remember it is "diameters" not "Gs" that mess up jumps. The gravity sitting on the downport of a size 1 world is much different than sitting on the downport of a size 9 world.

You can argue that it's the presence of a gravity well, rather than actual G's. The 100d limit for a size 1 world is less than a size 9 world as the gravity well is smaller for the size 1 world.

 

[Andrew Boulton]

The rules have always said you *can* jump in a gravity well.

 

[The Thing]

The rules have always said you *can* jump in a gravity well.

And probably misjump.

BTW, I had a simple way for determining the chance of a misjump if anyone wants to cop it:

You have to be 100 diameters to jump safely, so if you're too close, determine how many diamaters short of 100 you are, that's the chance on percentile die of misjumping.

Example: The March Hare is leaving Morganthis when it's attacked by Blackbeard Jackson's pirate cruiser. The captain sees his only choices are jump early or be shot to bits, then boarded, murdered and robbed.

He jumps.

The March Hare is 480,000 miles from Morganthis, Morganthis' diameter is 8,000 miles, he would normally need to be 800,000 miles away to jump safely. At 480,000 miles he's only 60 diameters away, and thus has a 40% chance of a misjump due to the gravity well proximity, in addition to the normal chance of a misjump.

So upon jump you'd roll a percentile and try to roll over 40, if it fails you automatically go to the misjump table. If it succeeds then roll for jump normally.

 

[aramis]

10 diameters, under CT, is only about a 16% to 35% chance... so your method is FAR harsher... oh, and at surface, it is 2d6+10 for 13+ to misjump, only about 97% chance...

 

[Fritz_Brown]

10 diameters, under CT, is only about a 16% to 35% chance... so your method is FAR harsher... oh, and at surface, it is 2d6+10 for 13+ to misjump, only about 97% chance...

So, there's still a 3% chance we'll make it? Right? Right?

 

[TheEngineer]

Even if you make a misjump, there is a pretty chance to get thru that (using MT).
In MT a throw of 10- on 3D will just bunch you away a bit from the target.
Now, thats a bit in contrast to the information from the good old jumpspace article,
where Mr. Miller describes it as rare event, that a ship survives a jump drive activation
in a gravity well.

What do TNE/T2 say here ?

 

[aramis]

So, there's still a 3% chance we'll make it? Right? Right?

well, 1/36th, to be exact. CT is SOOoo vicious.

Far nicer in MT...

 

[atpollard]

10 diameters, under CT, is only about a 16% to 35% chance... so your method is FAR harsher... oh, and at surface, it is 2d6+10 for 13+ to misjump, only about 97% chance...

From CT book 2:
Misjump: Each time the ship engages in a jump, throw 13+ for a misjump: Apply the following DMs: +1 if using unrefined fuel (and not equipped to do so), +5 if within 100 planetary diameters of a world, +15 if within 10 planetary diameters of a world. If the result is 16+, then the ship is destroyed.

From 10 diameters to 100 diameters, the chance of a misjump is 13+ on 2D6+5 with the ship destroyed on a roll of 16 or higher. Chance for a misjump is 26/36 (72.2%) and the chance for destruction is 3/36 (8.3%).

From surface to 10 diameters, the chance of a misjump is 13+ on 2D6+15 with the ship destroyed on a roll of 16 or higher. The chance for a misjump and destruction are both over 100%.

You may know of some errata to this, but this is repeated in Book 2 (c. 1981), The Traveller Book (c. 1982) and the CT CD PDFs.

 

[TheEngineer]

Well, CT is/was indeed very though here...
So MT saved many characters life I guess

 

[atpollard]

My first thought was "what is the purpose of listing rules for jumping from less than 10 diameters", if the result is automatic destruction with no chance for success?

 

[far-trader]

From 10 diameters to 100 diameters, the chance of a misjump is 13+ on 2D6+5 with the ship destroyed on a roll of 16 or higher. Chance for a misjump is 26/36 (72.2%) and the chance for destruction is 3/36 (8.3%).

From surface to 10 diameters, the chance of a misjump is 13+ on 2D6+15 with the ship destroyed on a roll of 16 or higher. The chance for a misjump and destruction are both over 100%.

You may know of some errata to this, but this is repeated in Book 2 (c. 1981), The Traveller Book (c. 1982) and the CT CD PDFs.

Nope no errata I know of. I suspect what has you wondering is the 100% chance of both misjump and destruction at less than 10d. But I don't think the DMs for distance were intended to be cumulative. And you've forgotten (or ignored for the examples) the DMs for being Navy (-1) or Scout (-2) ship. So even with cumulative DMs for distance a really really lucky Scout ship may survive and only misjump at less than 10d.

 

[atpollard]

Nope no errata I know of. I suspect what has you wondering is the 100% chance of both misjump and destruction at less than 10d. But I don't think the DMs for distance were intended to be cumulative. And you've forgotten (or ignored for the examples) the DMs for being Navy (-1) or Scout (-2) ship. So even with cumulative DMs for distance a really really lucky Scout ship may survive and only misjump at less than 10d.

The +15 that I quoted was "word for word" from page 6 of Book 2 on the CD by FFE. Page 6 has no mention of other modifiers.

After your comment, I took another look and found the table on page 11 of Book 2. Page 11 lists a +10 modifier for jumping within 10 diameters and the +1 Navy and +2 Scout.

Personally, I think +10 is better than +15 since it makes the action very dangerous but not impossible, but page 6 clearly states +15 (either intending the +5 and +10 to be cumulative or a simple typographic error).

Both the +15 text and +10 table are repeated in The Traveller Book.

 

[far-trader]

Interesting. I must have noticed the discrepancy at some time but glossed over and forgot it.

Looking at it now I'd be inclined to say that both are right. The table is meant to be cumulative and the text reflects adding the +5 and +10. But then we're back to you wondering (and I join you now) why bother? Only a Scout ship is going to have any (very very small) chance of not being destroyed. Every other ship, even Navy ships, will always be destroyed.

And then MT really changed things.

Based on the MT approach I'd argue (and maybe that's why I had CT the way I did) the distance DMs are not cumulative?

 

[Andrew Boulton]

T4:

Each time the ship engages in a jump, roll 2- for a misjump. Apply the following DMs: +1 if using unrefined fuel when not equipped to do so, +5 if within 100 planetary diameters of a world or star. The ship is destroyed if jumped within 10 planetary diameters of a world or star.

Ouch.​

 

[far-trader]

T4, Marc Miller's Traveller after all, seems to be saying that CT was meant to add the distance DMs then.

 

[aramis]

Since I always go with tables over text, I just figured the distance was not cumulative.

In any case, TTB, page 55, shows 16+ for destruction, so a scout (-2) at is +13, and is a 1/36 change of survival if you cumulate distance mods. But, as Thrash pointed out, even 1/36 is an economic breaker, so in CT, the bank should mandate refined fuel only on merchants, and thus D & E ports become "Dead" trade worlds.

MT makes the task formidable (2d + Engr + (edu/5) vs 15+; 2x (3d-Engr-(edu/5)) minutes) with a default assumption of an engineer at Engr 1 and Edu 7 for dm +2, that means it only succeeds if you take extra time (Reduce Diff by 4, similar to a DM+4) or have a more skilled or better educated (10+) engr.

 DM   Success     Fail       Mishap
 +1   0/36= 0%  0/36= 0%  36/36=100% 
 +2   0/36= 0%  1/36= 3%  35/36=97%
 +3   1/36= 3%  2/36= 5%  33/36=92%
 +4   3/36= 8%  3/36= 8%  30/36=83%
 +5   6/36=17%  4/36=11%  26/36=62%
 +6  10/36=28%  5/36=14%  21/36=58%
 +7  15/36=42%  6/36=17%  15/36=43%
 +8  21/36=58%  5/36=14%  10/36=28%
 +9* 26/36=72%  4/36=11%   6/36=17%
+10* 30/36=83%  3/36= 8%   3/36= 9%
+11* 33/36=92%  2/36= 5%   1/36= 3%
+12* 35/36=97%  1/36= 3%   0/36= 0%

*included to account for extra time. 
count extra time as DM+4 for this table, 
otherwise DM+8 is the limit.

On a failure, it's a 3d mishap, with 15+ being destroyed; a natural 2 is 4d mishap (with 15+ still being destroyed). A mishap roll of 11+ is a misjump in the classic sense, and a 3-10 is the wrong time spent in jump.

TNE is almost as forgiving. But I don't have it to hand.

T4 changes the +15 reference to "destroyed if jumped within 10 planetary diameters" but gives the CT Table Verbatim.

 

[Darkhstarr]

The original group I learned Traveller had worked out that operating a jump drive within a planet's gravity well would result in total destruction of the ship. Don't remember the particulars. When I ran the second Sky Raiders adventure the party (whose trader was ptractically unarmed) eliminated the villain fleet of 4 Zhodani scouts by arranging for one to go into jump on the ground. I do remember it left a 10 km radius zone of destruction.