Starships must maintain a distance of at least 100 diameters during jump operations unless they want to incur a possibility of misjump due to gravity wells. I am curious, does this apply to stars as well? Since a star is the largest stellar object in the system and has the most gravitational pull my guess (based on my limited knowledge of physics) would be yes, the distance applies to ANY stellar body. This makes for some interesting effects. For example, the sun is 1.4 million kilometers in diameter. This means that the minimum safe distance from Sol is 140,000,000 km, or 87,000,000 miles, almost the distance from the Sun to Earth (93,000,000 miles).
Safe Jump Distance from Stars
- Thread starter ddamant
- Start date
yep.
lbb6 scouts lists stellar diameters and planetary orbits, it's not difficult to determine if a destination world is within a star's 100d. I wrote up a qbasic program to generate lbb6 systems that includes information on where the star's 100d is in relation to the planets' orbits.
and yep, iirc our sun's 100d is at 472ls while earth's orbit is at 499ls.
Per T5, it applies to everything bigger than the ship.
T5.09 p.339 said:
Given the term body, we can presume the minimum density is no lower than the corona of a star...
It also means that for giant and supergiant stars, the 100D limit would be prohibitively far away. A giant star with a radius of 1 AU would have a 100D limit of 200 AU.
(though seriously, why the hell is it "100 Diameters"? If it's really "a radius equal to 100 Diameters" then why not just say "200 Radii" which is far less confusing?)
(though seriously, why the hell is it "100 Diameters"? If it's really "a radius equal to 100 Diameters" then why not just say "200 Radii" which is far less confusing?)
I feel this is a particularly flawed and impractical decision. Other ships or small artificial objects shouldn't count (and what, if a small ship extended 1km tethers on either side of it then is it suddenly blocking jump as if it was a 2km wide object?). Are people really going to be expected to calculate the exact position of all the ships nearby to see if they overlap with their 100D limits?
For ships, even the largest canonical ships (1 MTd) have given the needle shape, a maximum measure of about 1050m (1 MTd hull base = 300m, *3.5 for open structure) ... and anything that big within 100 kilometers is visual range. (At 1G, that's a 1 sec burn to cross in 11 sec.)
It's bloody trivial distance for all but the slowest ships.
The 100D of objects in the oort cloud (or asteroid belt for that matter) won't block travel - they're too small and too far apart. The idea that a ship's path can be blocked by asteroids or comets is a myth.
Gravitational fields aren't the issue here, only size matters for the 100D limit. Objects in the Oort cloud are too far apart to affect anything - you could draw a straight line through the Oort Cloud and it wouldn't intersect anything. They're separated by hundreds of millions of km, and their 100D limits of the vast majority are going to be under 100 km. Sure, a few are big enough to be "dwarf planet"-sized and those would have 100D limits of more like 100,000 km but that's still tiny compared to the space in between. (same applies to the asteroid belt too).
The only way you could go to a Oort Cloud object is to know exactly where it is and aim directly for it, you wouldn't just randomly be brought out of jump by hitting the 100D limit of one.
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I can confirm that they're a VERY low percentage of the sky.
The probability of a stop due to Oort clouds, given 100 diameter limits, is P=0.0000816324338903662% or so. (I figured the average density given NASA numbers, then turned it into an average obscuration area per surface area of the oort...
For each 10x increase from 100D, 100x the chance.
T5.0 hop was 0.00816%, G stars blocked to 10 AU (jupiter)
T5.0 skip was 0.816%, G stars blocked to 100 AU (past neptune)
T5.0 Leap was 81.6%, G stars block to 1000 AU
T5.0 Bound, was automatically stopped. G stars block to 10,000 AU, or about 0.16 LY
T5.0 Vault was auto-stop oort, and G stars block 1.6 LY - essentially the system's starmap hex.
This is why 5.09 is not increased jump masking by type. Also note, At T5.0 Leap, a system within 2Pc of your line was likely to interrupt your Leap, and guaranteed to interrupt your bound, because the ~1 AU semi-major and semi-minor axis for outer bound are a series of almost always overlapping shadows when you try to look past.
kilemall
SOC-14 5K
Look, I don't really care about the whole jump shadowing/propagating out of jump thing, that whole post-CT engineering is not my bag and I have it working differently anyway.
In any event I wasn't talking about the Oort cloud as jump barrier, merely contrasting these smaller astronomical objects and their 100d distances as being uncomfortably close to jump in and out of compared to the usual planetary and stellar distances.
As in, too hard to hit Even When You Want To.
1 Pc is 3.26 LY... 31 trillion km. Accuracy is ±3000 km ... about 1 in 1,000,000,000. Hitting an oort object of 20 km across is aiming for 400 km diameter circle...
400/3000=0.13Pc=0.434 LY
You can't hit it from Earth. The inner ones of 23km or so, yes. The biggest ones are dwarf planets, which can be hit from several parsecs...
kilemall
SOC-14 5K
Great, you guys have fun with all that.
I'm quite fat dumb and happy dealing with the CT definition, which just has the 100D limit and no need to hit a specific gravitational boundary/target to exit.
Deep space fuel dumps/stations are a Big Deal for my milieu that do not require gravitational anchors/a spit of rock to use. Same reason I can't be bothered with this 1000D contragrav thing, gotta have reaction/warp drives of some sort that can operate in deep space.
YUMV.
I'm quite fat dumb and happy dealing with the CT definition, which just has the 100D limit and no need to hit a specific gravitational boundary/target to exit.
Deep space fuel dumps/stations are a Big Deal for my milieu that do not require gravitational anchors/a spit of rock to use. Same reason I can't be bothered with this 1000D contragrav thing, gotta have reaction/warp drives of some sort that can operate in deep space.
YUMV.
BlackBat242
SOC-14 1K
Exactly - all that T5 stuff is really out of place here in the CT section anyway.
The ability to be stoped by an intervening a gravity well IS from CT sources. 2nd year of JTAS...
The different star clases (and so sizes) first appear (AFAIK) in LBB6, and those star sizes may mean the 100D limit englobes the habitable zone (and so the mainworld), even if it is often ignored for game simplicity sake.
In fact, there are several systems in Travellermap where a ship would have to exit jump quite far from the mainworld due to this, making commerce more difficult (or assuming trade stations out of the 100D limit of the star) if you want to be purist...
kilemall
SOC-14 5K
I am aware of that and was wondering who was going to throw that one into play.
That's a natural extension of the original 100D and that's it rule.
But that's entirely different from from jump shadowing, at least in my head, to me you are intending to come out into normal space at a specific point but the gravity well forces a bounce out. Different from 'draw a straight line from initial jump to target point, astronomical body intervenes and stops jump'.
Much less that it is a desirable technique morphing into a requirement to have a gravitic body to pull back.
Of course, to be fair, I do have that mapped subspace requirement, which means somebody had to invest the normal space travel time to get there, and arguably is more restrictive in a way.
But that also allows for secret bases, fueling dumps, trade routes, etc. which creates some very high value espionage.
I guess that's my biggest criticism of the whole official jump background that's developed since the 'simpler' days- it just seems like settling nerd arguments instead of providing greater play content.
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kilemall
SOC-14 5K
Don't really need LBB6 to get the diameter of large stars and project the jump limits will be far past any Goldilocks zone.....
