So, have the astrogator plot a jump course that goes above or below the shadow of the Primary. Yes, you'll end up further North/South of the mainworld than 100D due to trying to go above or below the System Primary 100D but surely a lot of the time that would be the closest approach than ending a jump anywhere else in the system because of a Jump Shadow, unless the mainworld was on the edge of the Primary's Jump Shadow. And yea, for simplicity sake assume that most systems have planetary orbits in the galactic plane. Once a system is completely surveyed by the IISS then the orbital period and paths of each world in the systems would surely be part of the standard navigational data. Jumping into a system North or South would also avoid any Jump Shadows of any GGs, provided their orbital paths are in the same plane.
Dynamic Sector Map Idea
- Thread starter DangerousThing
- Start date
So, have the astrogator plot a jump course that goes above or below the shadow of the Primary. Yes, you'll end up further North/South of the mainworld than 100D due to trying to go above or below the System Primary 100D but surely a lot of the time that would be the closest approach than ending a jump anywhere else in the system because of a Jump Shadow, unless the mainworld was on the edge of the Primary's Jump Shadow. And yea, for simplicity sake assume that most systems have planetary orbits in the galactic plane. Once a system is completely surveyed by the IISS then the orbital period and paths of each world in the systems would surely be part of the standard navigational data. Jumping into a system North or South would also avoid any Jump Shadows of any GGs, provided their orbital paths are in the same plane.
That's the point of including jump shadows. The astrogator will ALWAYS plot the nearest entry point to the target planet. BUT, you add the travel time. So, instead of 6 hours at 1G you get 24 hours at 1G to the planet or, to the nearest jump point. Etc.
Right. Which is why I just use a 5% rule.
You upload it to the gallery, rightclick on the resulting image, select "Copy image URL" from the popup, then img tag link to the upload in thread.
Enoki
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And the jump is in something like 4D+ space... But, if you assume the "universe" isn't two dimensional like the Traveller one technically is, then you would also need to know the height above and below some assumed reference (the galactic plain?) the systems are as well as their relative velocites of movement with respect to galactic center. For instance, the Sol (Terra) system in km/sec for U, V, W (the common axies used in astromony) are -9, +12, +7. Axial tilt of the two systems would also be important. It is fully possible one looks more like a bull's eye to the other in which case there is no "shadow" as you describe it.
That's alot of motion to keep track of....
Ah. Hey, that's pretty neat: the primary may be blocking the path to the destination system, and the destination star may be blocking the destination world.
That's likely when leaving a mainworld like Terra, isn't it? The sunward half of the sky is effectively blocked, so good luck if you need to get to something thataway.
Terra's worst-case would add approximately 1 day to your trip length. Average case is somewhat better than 50% of 50% of a day -- 6 hours. That's not an issue. Larger stars present larger problems, if the mainworld is near the star's 100D point, though.
That's likely when leaving a mainworld like Terra, isn't it? The sunward half of the sky is effectively blocked, so good luck if you need to get to something thataway.
Terra's worst-case would add approximately 1 day to your trip length. Average case is somewhat better than 50% of 50% of a day -- 6 hours. That's not an issue. Larger stars present larger problems, if the mainworld is near the star's 100D point, though.
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A It is fully possible one looks more like a bull's eye to the other in which case there is no "shadow" as you describe it.
That's alot of motion to keep track of....
Right. That's why I use a flat 5% chance.
Thanks!
Should I add that to the FAQ?
Done! www.travellerrpg.com/CotI/Discuss/faq.php?faq=vb_faq#faq_cotitipstricks
Back to topic.
Remember: The closer an object is to the primary, the more of an angle the primary takes up in its view. The Sun itself blocks about 0.5° of arc. (So also the moon). the exclusion zone for jump is 200 times that (Centerline ± 100 diameters), or about 100°.
From twice as far away, it'd be 1/2 as big as an angle - almost only 50° excluded by the solar blockage to jump.
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One thought about using a gravity model or tidal model - the inner lagrange point should be able to allow one to jump safely despite being inside the 100 diameters - but what they won't do is let you go anywhere - you should drop out at the same spot a week later.
That's why I up the % chance a bit if the planet you're leaving from is "hot" (Venus perhaps if it were habitable).
If you're in the ecosphere, a type G V is going to block 1/6 of the sky, roughly. (A cube is 90°x90° per side. Ecosphere location is going to block 90° to 120° of the sky from jump.)
More simply: the 100D sphere of the type G V effectively blocks close to half of the sky, doesn't it?
No. THe star is only 0.5°. The exclusion zone blocks 200x that, or 100°. That's not half the sky. It's close to half the daytime sky (which on a mountainless plain, is some 181-183° (yes, just a hair MORE than flat), but more than.
In 2d-space, it blocks just over 1/4 of the space.
In 3d-space, it blocks about 1/6th.
Which, given two Gx V stars, means (assuming essentially random positions) a 25/36 chance of not having to go at least half an AU out of your way... 11/36, or about 30.555% of being blocked from direct world-to-world.
Wow! ~6X higher than my random 5% chance. But, that's both sides of the equation. Your calcs are correct. That's a lot of extra travel time for star ships.
Thats why I adopted Measured Tidal Force in my last campaign - It scales as the cube root of distance, and works out to be linear of mass... but big fluffy things (like stars and GG's) get smaller.
And a big GG on the pure diameter can block a nifty large amount.
I always thought going tidal was the right way due to the supposed effect on jump. Mercury type planets get a bigger "shadow", the sun shrinks.
