General Is there a way to figure out the jump shadow of a sun?
- Thread starter Putraack
- Start date
Easiest is to use a chart from LBB 6 (Scouts) or Traveller5.
Just remember that, since Traveller is not a simulation, you shouldn't feel pressured to get it astronomically perfect. "Stickler" might land you in hot water, since I believe the star's class and rating don't necessarily map to a hard and fast diameter.... though I could be wrong there... but regardless that doesn't sound "easy" at all. It sounds like a painful rabbit-hole.
So.
Here's the T5 version (Book 3, p30). If I understand correctly, this is the exclusion map; for instance, a jump drive cannot operate at orbits 2 and under around a G5 V. At least that's how I remembered it.
Just remember that, since Traveller is not a simulation, you shouldn't feel pressured to get it astronomically perfect. "Stickler" might land you in hot water, since I believe the star's class and rating don't necessarily map to a hard and fast diameter.... though I could be wrong there... but regardless that doesn't sound "easy" at all. It sounds like a painful rabbit-hole.
So.
Here's the T5 version (Book 3, p30). If I understand correctly, this is the exclusion map; for instance, a jump drive cannot operate at orbits 2 and under around a G5 V. At least that's how I remembered it.
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AnotherDilbert
SOC-14 1K
To translate "orbit number" into km (T5.10, B3, p20):
Look up using O= column, read actual distance in AU, Million km, or lightseconds as needed.
This table also gives a rough guide to stellar size.
Look up using O= column, read actual distance in AU, Million km, or lightseconds as needed.
This table also gives a rough guide to stellar size.
AnotherDilbert
SOC-14 1K
If you don't have T5 or just want to make your life simple, you can use this guide to stellar radii relative to Sol radius:
https://en.wikipedia.org/wiki/Main_sequence#Sample_parameters
where R☉ is ~700 000 km.
https://en.wikipedia.org/wiki/Main_sequence#Sample_parameters
where R☉ is ~700 000 km.
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AnotherDilbert
SOC-14 1K
A few years ago I made a spreadsheet to calculate stellar masking distance and travel time for the Imperium, e.g.:
Regina has a F7 V star with a masking distance of 196 million km and a hab zone of 239 million km, so no extra real space travel time.
Hefry has a K6 II star with a masking distance of 17 360 million km and a hab zone of 5 804 million km, so an minimum extra real space travel time of 24.9 days (at 1 G IIRC) if approached at exactly the right angle.
Large spreadsheet:
https://www.dropbox.com/s/q6tem6z2fxn9cwq/ Imperium Stellar.xlsx?dl=1
Regina has a F7 V star with a masking distance of 196 million km and a hab zone of 239 million km, so no extra real space travel time.
Hefry has a K6 II star with a masking distance of 17 360 million km and a hab zone of 5 804 million km, so an minimum extra real space travel time of 24.9 days (at 1 G IIRC) if approached at exactly the right angle.
Large spreadsheet:
https://www.dropbox.com/s/q6tem6z2fxn9cwq/ Imperium Stellar.xlsx?dl=1
If it's a main sequence star, then the jump shadow radius is:
In the case our system, Earth's orbit is about 34 light seconds outside Sol's jump shadow on average. Perisol of .983AU is well outside the shadow of 0.931 AU
In the case our system, Earth's orbit is about 34 light seconds outside Sol's jump shadow on average. Perisol of .983AU is well outside the shadow of 0.931 AU
AnotherDilbert
SOC-14 1K
Looking over the spreadsheet, the short conclusion is don't bother with this unless the star is a giant (class I-III).
For a giant the acceleration time is a few weeks or even months, making trade uneconomical. Presumably a starport would be placed outside the stars jump shadow, orbiting an outer planet or GG, so it would not matter here either.
If we want to really petty, some directions, hence some jump routes, would go through the stars jump shadow, so be impossible, at least some parts of the year.
For a giant the acceleration time is a few weeks or even months, making trade uneconomical. Presumably a starport would be placed outside the stars jump shadow, orbiting an outer planet or GG, so it would not matter here either.
If we want to really petty, some directions, hence some jump routes, would go through the stars jump shadow, so be impossible, at least some parts of the year.
Spinward Flow
SOC-14 1K
And then there are places like Pax Rulin where the star's enormous jump shadow is used as a (naval) military bastion (the habitable zone is around Pluto's orbit) and the jump shadow is 4.7x larger than that orbital radius.
Kind of makes you wonder how the Aslan Ihatei was able to "blow past" Pax Rulin so easily/conveniently by 1120 in order to conquer 22% of District 268, 93% of Glisten and 37.5% of Trin's Veil subsectors by 1120 ... as if Pax Rulin didn't exist (or have any military significance whatsoever). Being able to move a major race polity border by 3 subsectors in 15 years like that ... strains credulity.
The wiki timeline includes the following datapoints:
1110
1115
1119
So, basically, Aslan ihatei fleets and families effectively overran the entire Trojan Reach sector, snuffing out the Imperial presence in the Pax Rulin, Gazulin and Tobia sectors without ANY COMMUNICATIONS leaking out to coreward to inform fleets in the Spinward Marches thatwinter is coming the ihatei are steamroling their way coreward in an unstoppable tsunami wave consuming HUNDREDS of star systems. It's as if everyone rimward of Glisten just preemptively surrendered without firing a shot and simply let the Aslan roll over them.
Worse, you can't even use the excuse of Stephon's assassination as the proximate cause for this sudden push by the Aslan ihatei, since Strephon was assassinated in 1116, but the Aslan ihatei were already in District 268 of the Spinward Marches by 1115 at Talos.
The whole thing feels like someone spilled ink on the map and then decided to retroactively legitimize it without needing to do any historical setup.
Defeating a nation's military forces can be relatively quick work (especially if you've got a technological and logistical advantage).
SECURING and PACIFYING a nation's population after a quick conquest is a VERY different proposition!
Now scale that up to the point of entire worlds, subsectors and sectors.
How many BILLIONS of Aslan (and MILLIONS of starships!) are going to be required for an ihatei invasion to push all the way through the Trojan Reaches sector up into the Glisten subsector and successfully HOLD and administer the ground that they've gained between their previous border and the new border with Lunion subsector in about 10-20 years?
The only way that makes any sense whatsoever is if places like Pax Rulin were basically paper tigers built on fictions and lies.
Kind of makes you wonder how the Aslan Ihatei was able to "blow past" Pax Rulin so easily/conveniently by 1120 in order to conquer 22% of District 268, 93% of Glisten and 37.5% of Trin's Veil subsectors by 1120 ... as if Pax Rulin didn't exist (or have any military significance whatsoever). Being able to move a major race polity border by 3 subsectors in 15 years like that ... strains credulity.
The wiki timeline includes the following datapoints:
1110
1115
1119
So, basically, Aslan ihatei fleets and families effectively overran the entire Trojan Reach sector, snuffing out the Imperial presence in the Pax Rulin, Gazulin and Tobia sectors without ANY COMMUNICATIONS leaking out to coreward to inform fleets in the Spinward Marches that
Worse, you can't even use the excuse of Stephon's assassination as the proximate cause for this sudden push by the Aslan ihatei, since Strephon was assassinated in 1116, but the Aslan ihatei were already in District 268 of the Spinward Marches by 1115 at Talos.
The whole thing feels like someone spilled ink on the map and then decided to retroactively legitimize it without needing to do any historical setup.
Defeating a nation's military forces can be relatively quick work (especially if you've got a technological and logistical advantage).
SECURING and PACIFYING a nation's population after a quick conquest is a VERY different proposition!
Now scale that up to the point of entire worlds, subsectors and sectors.
How many BILLIONS of Aslan (and MILLIONS of starships!) are going to be required for an ihatei invasion to push all the way through the Trojan Reaches sector up into the Glisten subsector and successfully HOLD and administer the ground that they've gained between their previous border and the new border with Lunion subsector in about 10-20 years?
The only way that makes any sense whatsoever is if places like Pax Rulin were basically paper tigers built on fictions and lies.
mike wightman
SOC-14 10K
(My)Simple answer, the Aslan were invited to 'invade' by Norris since he needed the sort of loyalty only Aslan granted land can display 
While there were a few genuine conflicts, most of the military forces the Aslan encountered were heavy with personnel of questionable loyalty to Norris.
Post FFW Norris went on a power grab. He deposed Delphine as sector duke but knew he could not command the total loyalty and respect of the other dukes of the Marches.
He faced the possibility of Delphine calling on favours from dukes in the Deneb sector as well.
The Aslan provided a means to an end. From the example set by Darrian Aslan and Imperial Aslan, Norris was aware that if he granted territory the Aslan would swear fealty. So he began inviting them in, there are lots of sparsely populated worlds there for their 'occupation'.
When Norris got early warning of the assassination he contrived his fake elevation to archduke and accelerated the pace of the Aslanmigration invasion.
While there were a few genuine conflicts, most of the military forces the Aslan encountered were heavy with personnel of questionable loyalty to Norris.
Post FFW Norris went on a power grab. He deposed Delphine as sector duke but knew he could not command the total loyalty and respect of the other dukes of the Marches.
He faced the possibility of Delphine calling on favours from dukes in the Deneb sector as well.
The Aslan provided a means to an end. From the example set by Darrian Aslan and Imperial Aslan, Norris was aware that if he granted territory the Aslan would swear fealty. So he began inviting them in, there are lots of sparsely populated worlds there for their 'occupation'.
When Norris got early warning of the assassination he contrived his fake elevation to archduke and accelerated the pace of the Aslan
Gurp Far Trader deals with this at an abstract level.
They have some tables, but they also have a handwave mechanic. Simply, there's a 5% chance of "free space", and if it's blocked, then add 30 hours to the trip.
AnotherDilbert
SOC-14 1K
They simplify slightly... 30 h is nothing in this context, not nearly enough.
This is the worst case:
You either make two jumps (orange jump-lines), or accelerate (blue) for a week (or so) at one or both ends of the jump (red jump-line).
Either way it takes weeks extra.
(My)Simple answer, the Aslan were invited to 'invade' by Norris since he needed the sort of loyalty only Aslan granted land can display
While there were a few genuine conflicts, most of the military forces the Aslan encountered were heavy with personnel of questionable loyalty to Norris...
Not so much arguing Mike, just asking (this time around LOL)
Valid points on conflicts of the narrative brought up, just lookin to fit this piece in
The GDW MegaTraveller Imperial Encyclopedia (I know of the ties to DGP, but this part is GDW data, sir!) shows that by 1120 Glisten subsector was absorbed by the ihatei (minus 1731 Grote and 1733 Lydia) along with portions of District 268 and Trin's Veil subsectors. Putting the physics part aside, how would this fit into the story? The ihatei did not respect Norris' authoriti much after Rebellion started? I would not think Norris' would let them just have Glisten, an "Very Important (+5)" world.
TravellerMap: Glisten Subsector, 1120
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mike wightman
SOC-14 10K
What happened next... after the rebellion era.
Norris consolidates his power base within the Regency and all of those Aslan become loyal regency subjects under Norris...
Also, there is not a cat in hell's chance that Ihatei could "take" Glisten by force - it is a high population TL15 planetoid belt world system.
Norris consolidates his power base within the Regency and all of those Aslan become loyal regency subjects under Norris...
Also, there is not a cat in hell's chance that Ihatei could "take" Glisten by force - it is a high population TL15 planetoid belt world system.
Spinward Flow
SOC-14 1K
Cynical much?(My)Simple answer, the Aslan were invited to 'invade' by Norris since he needed the sort of loyalty only Aslan granted land can display
Post FFW Norris went on a power grab. He deposed Delphine as sector duke but knew he could not command the total loyalty and respect of the other dukes of the Marches.
He faced the possibility of Delphine calling on favours from dukes in the Deneb sector as well.
The Aslan provided a means to an end.
When Norris got early warning of the assassination he contrived his fake elevation to archduke and accelerated the pace of the Aslanmigrationinvasion.
The timeline for that doesn't work all that well when the ihatei were already on the move in the Trojan Reaches in 1110 (as cited above
) and the ihatei had already reached District 268 by 1115 ... a year before Strephon as assassinated in 1116, which would take another year (at jump lag speed) to reach the Spinward Marches, assuming no Ansible FTL communications tech is available between Core and the Spinward Marches (a few sectors away).Condottiere
SOC-14 5K
That would be one reason to have the early jump advantage for jump drives.
Presumably, that carries over for all jump shadows, cast anywhere.
With an excellent engineer, astounding astrogator, and well maintained machinery, you can risk a transition sub hundred diameters.
Presumably, that carries over for all jump shadows, cast anywhere.
With an excellent engineer, astounding astrogator, and well maintained machinery, you can risk a transition sub hundred diameters.
I'll concur on the 30 hours, but for you example, 700Mkm is "only" ~73 hours at 1g. So, 3 days, rather than a week. An extra week on both ends combined to be sure. And there may be scenarios where the "two jump" method saves time, but at a great cost to fuel (since it may be a deep space jump).
Under a TNE scenario where fuel is much more limited (few ships can afford to burn for 73 hours, much less 150), jumps may make more sense.
Of course the stark truth is that things like the Free Trader and what not were developed, well, in a vacuum. Simply, if ships need to routinely "jump twice" to get around starts, then routes would be established as such, whether with 1J drive w/2J of fuel ship designs, deep space fuel depots to handle stop overs, far orbit way stations, etc.
The talk of "oh, those routes wouldn't be profitable" is crazy talk. Of course they'd be profitable, the goods would simply be more expensive. The demand remains, folks need to eat, etc.
Now, maybe the system wouldn't have been populated in the first place, there's always that, different problem. But if there's several million/billion people on one end, traders will trade and find a way.
AnotherDilbert
SOC-14 1K
You can jump out of a jump shadow, but you can't jump into a jump shadow, regardless of how good your crew is.
Barring the "assuming you don't die" part, this is true.
As a GM and player, I prefer the mis-jumps at less 100 and even 10 diameters rather than "Your ship is destroyed." For NPC's and such, mis-jumps are effectively death sentences "off-screen". Not many ships have fuel capacity to "double jump" even when they know where they are at after mis-jump.
As a GM I see players doing this as a message to me the GM "You made this to hard", "We were stoopid greedy. Sorry." Whether mis-jump or destroyed, I have to start a campaign elsewhere or roll new characters and start a new campaign.
As a player, if I'm involved in deciding, I'm not going to die a "no chance of surviving" death by Navy or local pirates, so I would risk the mis-jump and pray on GM mercy. TPK is devastating to GMs and players alike,
As a GM I see players doing this as a message to me the GM "You made this to hard", "We were stoopid greedy. Sorry." Whether mis-jump or destroyed, I have to start a campaign elsewhere or roll new characters and start a new campaign.
As a player, if I'm involved in deciding, I'm not going to die a "no chance of surviving" death by Navy or local pirates, so I would risk the mis-jump and pray on GM mercy. TPK is devastating to GMs and players alike,
AnotherDilbert
SOC-14 1K
LBB2'81, p10:
T = 2 √( 700 000 000 000 m / 10 m/s2 ) ≈ 530 000 s ≈ 147 h ≈ 6 days.
Standard practice is supposed to be to slow down to jump at low velocity.
Agreed, MT and TNE needed less jump fuel.
The defaults were defined before this was considered, or at least disregarded for simplicity.
Of course, to play the game we have to ignore all this, it's much too complicated to care about at the table. It can be used as a plot device, perhaps?
