In follow up to this post :

It's unlikely that your players ever will take the chance, but ORKS just might do this. So here a suggestion of the percentile mishap (= BOOM)

Assumptions:

- Warp exit/entry at edge: change of mishap 0% (concerning the gravity well)
- Warp exit/entry close to the star: chance of mishap 50% (again: concerning the gravity well). Initially I was thinking 100% but as habital planets are typically 1 AU away in a typically 40 AU solar system would mean that jumping close to the habital planet is about 100% chance on mishap. That with the fact that mishap = warpdrive explodes, in other words: end of story for the ship!! AND the reference earlier mentioned of the ork fleet jumping in on a star fleet in orbit, would have meant the instant decimation of the entire fleet. Hence: 50% chance on blow-up.

The formula to calculate this is very simple:

Chance on mishap = (7*DFE/SR)^2 %

here is:

SR = Solar system Radius (e.g. 30 AU, solar system of Terra)

DFE = distance from edge of the solar system where you jump in. E.g. with an with an SR=30, 0 is the edge and 30 is inside the sun. Entry at halfway = 15 AU:

Mishap = (7*15/30)^2 = 12%.

If you like to keep things simple and assume EVERY solar system of size 50AU then the formula becomes really simple:

Chance on Mishap = DFE^2 / 50 %

To resolve simply throw a 1d100 if you roll UNDER the set score: BOOM

Some chances (assuming SR = 50)

Jumping in at:
Distance from edge - %

0 (jump at the edge) - 0%
6 - 1%
10 - 2%
20 - 8%
30 - 18%
40 - 32%
49 (jumping close to a habital planet which are typically at 1 to 3 AU away from its sun) - 48%
50 - 50%

If a navigator could exit at a Lagrangian point it might be safer. However this might be a hellish difficulty.

Fresnel said:

hmm interesting notion… I guess that in that case L1 to L3 are right out as they are unstable and too small to ever make that jump (in addition 1 and 2 are REALLY close to the planet), which leaves L4 and 5, which are stable and quite a bit larger then 1,2 and 3. If you would jump there then you would be at 1AU distance from the planet. L4 and 5 are actually pretty big, about 1AU length and half that in width so its not THAT hard. What makes it hard in general to find the right spot at all is the fact of the time distortion in the warp. In order to jump right next to a planet or in a lagrange point you need to know the time (as that decides the position of the planet and LP in regard of its star).

So basically you want to jump at a distance of 1AU from the star without much error, lets say max 10% so within 0.9 to 1.1 AU AND you need to know the exit time. Both these rolls are part of the 5 navigation steps.

First you need to know the time, now the LP are pretty big so there's always a 30% chance that you jump into one. And I would rule that if you jump in from farther then from the edge of the solar system as beyond that its really completely random at what exact time you jump in. Should you jump first to the edge and then from the edge to the LP then I would rule a very hard Navigation Warp test (-30) for the correct estimate, however since there is a 30% chance that you get it right anyway I would simply rule a Navigation Warp Test (+0). Every degree of fail increases the difficulty of the 'leaving the warp' with one step, more then 3 DoF means your NOT jumping in the LP.

'Charting course' is negligible (again assuming jumping from edge) so ordinary warp

'steering vessel' will again influence the time and space exit which are vital so again very hard test (-30) navigation warp and again 3 DOF means NOT jumping in the LP and every DoF increases the difficulty with one step on leaving the warp.

When that's done you need to roll 'leaving the warp test' which is usually at -20, this time modified with the DoF of the other rolls.

Should you actually succeed this test then this would half the chance of BOOM to 24% lowering it further with 1% for every degree of success. Fail would mean you arrive at roughly 1AU from the sun: 48%. Should you fail this warp with 6+ DoF then you jump straight into the sun.

Lagrange points are cosmically not extremely large. One of the systems my RT ran into had a stabilization gate that allowed Lagrange point jumping, but other then that only one Ork vessel and two Chaos vessels ever attempted it (one failing its check miserably and completely torn apart as a result). The above rules are a nice system, I'll keep it in mind if my players ever get desperate enough.

even if they are hard to jump IN to. think of the time saved by jumping OUT from them.

Trader Austin said:

hmm… very very good point. Typically something my players would bring along when I would have proposed this house rule.

However given the fact that jumping out of lagrange spots is still not described anywhere in the rules (although that would require some astronomy/physics knowledge) and thus we sort of can expect that its not common practice. If its not common practice then this can have two origins:

1. unknown (that is the empire is unaware of LP's and thus don't use them.) If thats the case then the players won't know about them either and thus they're effectively useless.

2. (too?) dangerous. Although the BOOM % is much lower then jumping in… its still there, though Im inclined to make it a lot slower. Basically I would say

a. its very hard to plot a course form there -30 nav tests to plot to the edge of the solar, -60 if you try to plot immediately to a further destination.

b. there is still a BOOM %… 10%? maybe relate it to the ship size… still have a test with 1% modification per DoS / DoF ?