Stellar Jump Masking

[Supplement Four]

I had thought that jump masking with respect to a system's star was controversial and didn't make it into Traveller canon until GURPS Trav.

But, tonight, while perusing Book 6, what do I see?

Pg. 42, Book 6: "[Stellar] Radius can also be used to determine minimum jump distance from a star (misjumps are more probable inside 20 radii and 200 radii from the star)."

Here again, I see a concept first imagined in CT (when popular belief is that it was grown into Traveller canon through later rules sets).

But, my question is...

There really isn't an easy way to figure stellar jump masking on the fly during a Traveller game, is there?

In this day and age, where I am able to use a program like Heaven & Earth, I usually print out the details about a world that I know my players will visit and maybe a few worlds around it. Heck, in just a few moments, I can have H&E detail the entire subsector and print that stuff out to have on hand in case my player stray from where I intend them to go during the game.

But, I was looking for a quick fix. I wanted to see if there was a quick way to determine stellar jump masking on the fly. And, right now, I'm at a loss.

It looks like you'd have to detail the star (at least some details), and then figure orbits and place planets and the main world before you could find this out...it's really something that needs to be done pre-game.

I look at the Orbital Distances and Habital Zone Distance tables on pg. 46 of Book 6, and Stellar Radii chart on pg. 47 of Book 6. What I see is that (according to the chart on pg. 46) stellar masking can reach far into the star system.

According to the chart on pg. 46, Terra is jump masked in our star system. Well, it look to be right on the edge.

But, if a ship were to travel to Venus or Mercury, it'd surely falling within the jump masked area of Sol.

If you were leaving Terra, you'd have to plan your flight outsystem, away from Sol, before you were able to safely engage the jump drive.

Am I missing something? Is there an easy way to look at Traveller data and know if the main world in the system is masked by the system's star?

If there is, enlighten me. Because I don't see it. It looks like one would have to detail much of the system--at least the early orbits--before jump masking can be accuratly guessed at.

Anybody got a better system?

 

[Supplement Four]

I had thought that jump masking with respect to a system's star was controversial and didn't make it into Traveller canon until GURPS Trav.

But, tonight, while perusing Book 6, what do I see?

Pg. 42, Book 6: "[Stellar] Radius can also be used to determine minimum jump distance from a star (misjumps are more probable inside 20 radii and 200 radii from the star)."

Here again, I see a concept first imagined in CT (when popular belief is that it was grown into Traveller canon through later rules sets).

But, my question is...

There really isn't an easy way to figure stellar jump masking on the fly during a Traveller game, is there?

In this day and age, where I am able to use a program like Heaven & Earth, I usually print out the details about a world that I know my players will visit and maybe a few worlds around it. Heck, in just a few moments, I can have H&E detail the entire subsector and print that stuff out to have on hand in case my player stray from where I intend them to go during the game.

But, I was looking for a quick fix. I wanted to see if there was a quick way to determine stellar jump masking on the fly. And, right now, I'm at a loss.

It looks like you'd have to detail the star (at least some details), and then figure orbits and place planets and the main world before you could find this out...it's really something that needs to be done pre-game.

I look at the Orbital Distances and Habital Zone Distance tables on pg. 46 of Book 6, and Stellar Radii chart on pg. 47 of Book 6. What I see is that (according to the chart on pg. 46) stellar masking can reach far into the star system.

According to the chart on pg. 46, Terra is jump masked in our star system. Well, it look to be right on the edge.

But, if a ship were to travel to Venus or Mercury, it'd surely falling within the jump masked area of Sol.

If you were leaving Terra, you'd have to plan your flight outsystem, away from Sol, before you were able to safely engage the jump drive.

Am I missing something? Is there an easy way to look at Traveller data and know if the main world in the system is masked by the system's star?

If there is, enlighten me. Because I don't see it. It looks like one would have to detail much of the system--at least the early orbits--before jump masking can be accuratly guessed at.

Anybody got a better system?

 

[Malenfant]

You'd just need to know the star type and the mainworld orbit (which would usually be the habitable zone).

Then you can just lookup on the table below for a rough estimate:

A V: 3 AU (Orbit 0-5 inside)
F V: 2 AU (Orbit 0-4 inside)
G V: 1 AU (Orbit 0-3 inside)
K V: 0.5 AU (Orbit 0-1 inside)
M V: 0.3 AU (Orbit 0 inside)
Giant: 20 AU (Orbit 0-8 inside)

 

[Malenfant]

You'd just need to know the star type and the mainworld orbit (which would usually be the habitable zone).

Then you can just lookup on the table below for a rough estimate:

A V: 3 AU (Orbit 0-5 inside)
F V: 2 AU (Orbit 0-4 inside)
G V: 1 AU (Orbit 0-3 inside)
K V: 0.5 AU (Orbit 0-1 inside)
M V: 0.3 AU (Orbit 0 inside)
Giant: 20 AU (Orbit 0-8 inside)

 

[The Shaman]

Originally posted by Supplement Four:
It looks like you'd have to detail the star (at least some details), and then figure orbits and place planets and the main world before you could find this out...it's really something that needs to be done pre-game.

4e GURPS Space includes a calculation for the diameter of a star in AU, which makes it extremely easy to compare the 100D limit of the star with the orbital distance in AU of the mainworld (or any other world in the system). It's not a particularly difficult calculation, but as you note it's not something you really want to do on-the-fly - a little prep time is helpful for this level of detail.

If the mainworld is a gas giant satellite, the starship navigator also have the diameter of the jovian to consider as well.

 

[The Shaman]

Originally posted by Supplement Four:
It looks like you'd have to detail the star (at least some details), and then figure orbits and place planets and the main world before you could find this out...it's really something that needs to be done pre-game.

4e GURPS Space includes a calculation for the diameter of a star in AU, which makes it extremely easy to compare the 100D limit of the star with the orbital distance in AU of the mainworld (or any other world in the system). It's not a particularly difficult calculation, but as you note it's not something you really want to do on-the-fly - a little prep time is helpful for this level of detail.

If the mainworld is a gas giant satellite, the starship navigator also have the diameter of the jovian to consider as well.

 

[flykiller]

I have a small program that spits out book 6 systems. it specifically lists the star's 100d in LS and the orbit ring of each planet in LS, so a glance at the two immediately shows how far a ship has to go to clear the star's 100d. also does the same thing for gg moons.

if you like I can send you the source code, or a list of systems it generates. you could grab one from the list as you need them.

 

[flykiller]

I have a small program that spits out book 6 systems. it specifically lists the star's 100d in LS and the orbit ring of each planet in LS, so a glance at the two immediately shows how far a ship has to go to clear the star's 100d. also does the same thing for gg moons.

if you like I can send you the source code, or a list of systems it generates. you could grab one from the list as you need them.

 

[Plankowner]

As a quick rule of thumb, I just used the Inner Zone as inside the stellar Jump Mask. GG worlds took a bit of work, but if you use 100,000 km as the diameter of a LGG and 50,000 km as the diameter of a SGG, you could make a pretty good estimate in a very short time.

Of course, if it was part of the storyline, I would do all the calculations and have it ready.

 

[Plankowner]

As a quick rule of thumb, I just used the Inner Zone as inside the stellar Jump Mask. GG worlds took a bit of work, but if you use 100,000 km as the diameter of a LGG and 50,000 km as the diameter of a SGG, you could make a pretty good estimate in a very short time.

Of course, if it was part of the storyline, I would do all the calculations and have it ready.

 

[flykiller]

As a quick rule of thumb, I just used the Inner Zone as inside the stellar Jump Mask.

most stars supposedly are K and M, and the habitable zone (if they even have one) is from 50 to 150 LS inside their 100d. least, by book 6.

 

[flykiller]

As a quick rule of thumb, I just used the Inner Zone as inside the stellar Jump Mask.

most stars supposedly are K and M, and the habitable zone (if they even have one) is from 50 to 150 LS inside their 100d. least, by book 6.

 

[rancke]

Originally posted by Supplement Four:
I had thought that jump masking with respect to a system's star was controversial and didn't make it into Traveller canon until GURPS Trav.

But, tonight, while perusing Book 6, what do I see?

Pg. 42, Book 6: "[Stellar] Radius can also be used to determine minimum jump distance from a star (misjumps are more probable inside 20 radii and 200 radii from the star)."

Here again, I see a concept first imagined in CT (when popular belief is that it was grown into Traveller canon through later rules sets).

That's jump shadowing (a world being perpetually inside the jump limit of a star), and that's been part of CT canon from the start (by implication) and IIRC showed up explicitly pretty early.

Jump masking (both ship and destination world outside stellar jump limits, but a jump limit directly between the two impedes the jump) didn't show up until GT (although it appears that Marc Miller had thought that was the way things worked all the time -- it just hadn't been explicitly mentioned anywhere).

I don't see how jump masking can be controversial. Marc Miller said that's the way it works. How much more canonical can it get?

Unless you mean that some people dislike it. In that sense there's a lot of Traveller material that's controversial, CT to T20 and every version in between.

Hans

 

[rancke]

Originally posted by Supplement Four:
I had thought that jump masking with respect to a system's star was controversial and didn't make it into Traveller canon until GURPS Trav.

But, tonight, while perusing Book 6, what do I see?

Pg. 42, Book 6: "[Stellar] Radius can also be used to determine minimum jump distance from a star (misjumps are more probable inside 20 radii and 200 radii from the star)."

Here again, I see a concept first imagined in CT (when popular belief is that it was grown into Traveller canon through later rules sets).

That's jump shadowing (a world being perpetually inside the jump limit of a star), and that's been part of CT canon from the start (by implication) and IIRC showed up explicitly pretty early.

Jump masking (both ship and destination world outside stellar jump limits, but a jump limit directly between the two impedes the jump) didn't show up until GT (although it appears that Marc Miller had thought that was the way things worked all the time -- it just hadn't been explicitly mentioned anywhere).

I don't see how jump masking can be controversial. Marc Miller said that's the way it works. How much more canonical can it get?

Unless you mean that some people dislike it. In that sense there's a lot of Traveller material that's controversial, CT to T20 and every version in between.

Hans

 

[flykiller]

for what it's worth, using book 6, here's a list of the various star types and sizes, and their habitable zone orbits adjacent to their 100d limits for easy comparison.

the first chart is the basic star generation system, 'case you need to make one on the fly.

the second chart cross-references the star type with its size. the number in parentheses is the listed habitable orbit number, and the number following is the listed habitable orbit's distance from the star in light seconds. the number under that is the star's 100d limit, in light seconds.

a simple comparison between the habitable zone distance in LS with the star's 100d limit in LS shows whether or not the habitable zone is inside the star's 100d limit, and by how much. those habitable zones that are inside the star's 100d are marked with "*". in some cases the distance inside the star 100d is quite significant.

the third chart shows the orbit number distances in light seconds that I used. ymmv. I believe each digit string is unique so if anything needs to be changed then a simple find/replace should do the trick - might want to check for typo's first though.

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> Star Type
(solo/binary)(spectral type)(spectral decimal)(size)(companion orbit number)

result 2d6 2d6 1d6 2d6 2d6
0 B Ia
1 B 0 Ib
2 solo A 0 II c
3 solo M 0 III c
4 solo M 5 IV 1
5 solo M 5 V 2
6 solo M 5 V 3
7 solo M V 4+d6
8 bin K V 5+d6
9 bin G V 6+d6
10 bin F V 7+d6
11 bin F VI 8+d6
12 bin F D f

Ia Ib II III IV V
B0 (13)320,000 (13)320,000 (12)160,000 (12)160,000 (12)160,000 (12)160,000
24,110 13,910 10,200 7418 6028 4637
B5 (12)160,000 (11) 80,000 (11) 80,000 (10) 40,000 ( 9) 19,711 ( 9) 19,711
34,774 16,228 9273 4637 2457 2040
A0 (12)160,000 (11) 80,000 ( 9) 19,711 ( 8) 9591 ( 7) 4760 ( 7) 4760
62,593 23,183 8346 2875 2086 1484
A5 (12)160,000 (10) 40,000 ( 8) 9591 ( 7) 4760 ( 6) 2595 ( 6) 2595
69,085 25,501 6491 2133 1252 835
F0 (12)160,000 (10) 40,000 ( 8) 9591 ( 6) 2595 ( 6) 2595 ( 5) 1200
80,676 27,356 7418 2179 1252 788
F5 (11) 80,000 (10) 40,000 ( 8) 9591 ( 6) 2595 ( 5) 1200 ( 4) 758
94,586 27,819 8346 2411 * 1206 649
G0 (12)160,000 (10) 40,000 ( 8) 9591 ( 6) 2595 ( 5) 1200 ( 3) 499
138,169 38,947 * 11,591 * 3292 1159 478
G5 (12)160,000 (10) 40,000 ( 8) 9591 ( 7) 4760 ( 5) 1200 ( 2) 359
* 210,499 * 59,348 * 17,155 * 5100 * 1298 * 422
K0 (12)160,000 (10) 40,000 ( 9) 19,711 ( 7) 4760 ( 4) 758 ( 2) 359
* 303,230 * 100,150 * 25,037 * 7418 * 1530 * 421
K5 (12)160,000 (11) 80,000 ( 9) 19,711 ( 8) 9591 ( ?) ? ( 0) 100
* 468,292 * 181,753 * 57,493 * 19,474 * 262
M0 (12)160,000 (11) 80,000 (10) 40,000 ( 8) 9591 ( ?) ? ( 0) 100
* 680,182 * 397,352 * 109,886 * 29,210 * 255
M5 (12)160,000 (12)160,000 (11) 80,000 ( 9) 19,711 ( ?) ? ( ?) -
* 1,400,238 * 961,157 * 330,122 * 105,713 ? 166

orbit radii in LS
0 100
1 190
2 359
3 499
4 758
5 1200
6 2595
7 4760
8 9591
9 19,711
10 40,000
11 80,000
12 160,000
13 320,000</pre>[/QUOTE]

 

[flykiller]

for what it's worth, using book 6, here's a list of the various star types and sizes, and their habitable zone orbits adjacent to their 100d limits for easy comparison.

the first chart is the basic star generation system, 'case you need to make one on the fly.

the second chart cross-references the star type with its size. the number in parentheses is the listed habitable orbit number, and the number following is the listed habitable orbit's distance from the star in light seconds. the number under that is the star's 100d limit, in light seconds.

a simple comparison between the habitable zone distance in LS with the star's 100d limit in LS shows whether or not the habitable zone is inside the star's 100d limit, and by how much. those habitable zones that are inside the star's 100d are marked with "*". in some cases the distance inside the star 100d is quite significant.

the third chart shows the orbit number distances in light seconds that I used. ymmv. I believe each digit string is unique so if anything needs to be changed then a simple find/replace should do the trick - might want to check for typo's first though.

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> Star Type
(solo/binary)(spectral type)(spectral decimal)(size)(companion orbit number)

result 2d6 2d6 1d6 2d6 2d6
0 B Ia
1 B 0 Ib
2 solo A 0 II c
3 solo M 0 III c
4 solo M 5 IV 1
5 solo M 5 V 2
6 solo M 5 V 3
7 solo M V 4+d6
8 bin K V 5+d6
9 bin G V 6+d6
10 bin F V 7+d6
11 bin F VI 8+d6
12 bin F D f

Ia Ib II III IV V
B0 (13)320,000 (13)320,000 (12)160,000 (12)160,000 (12)160,000 (12)160,000
24,110 13,910 10,200 7418 6028 4637
B5 (12)160,000 (11) 80,000 (11) 80,000 (10) 40,000 ( 9) 19,711 ( 9) 19,711
34,774 16,228 9273 4637 2457 2040
A0 (12)160,000 (11) 80,000 ( 9) 19,711 ( 8) 9591 ( 7) 4760 ( 7) 4760
62,593 23,183 8346 2875 2086 1484
A5 (12)160,000 (10) 40,000 ( 8) 9591 ( 7) 4760 ( 6) 2595 ( 6) 2595
69,085 25,501 6491 2133 1252 835
F0 (12)160,000 (10) 40,000 ( 8) 9591 ( 6) 2595 ( 6) 2595 ( 5) 1200
80,676 27,356 7418 2179 1252 788
F5 (11) 80,000 (10) 40,000 ( 8) 9591 ( 6) 2595 ( 5) 1200 ( 4) 758
94,586 27,819 8346 2411 * 1206 649
G0 (12)160,000 (10) 40,000 ( 8) 9591 ( 6) 2595 ( 5) 1200 ( 3) 499
138,169 38,947 * 11,591 * 3292 1159 478
G5 (12)160,000 (10) 40,000 ( 8) 9591 ( 7) 4760 ( 5) 1200 ( 2) 359
* 210,499 * 59,348 * 17,155 * 5100 * 1298 * 422
K0 (12)160,000 (10) 40,000 ( 9) 19,711 ( 7) 4760 ( 4) 758 ( 2) 359
* 303,230 * 100,150 * 25,037 * 7418 * 1530 * 421
K5 (12)160,000 (11) 80,000 ( 9) 19,711 ( 8) 9591 ( ?) ? ( 0) 100
* 468,292 * 181,753 * 57,493 * 19,474 * 262
M0 (12)160,000 (11) 80,000 (10) 40,000 ( 8) 9591 ( ?) ? ( 0) 100
* 680,182 * 397,352 * 109,886 * 29,210 * 255
M5 (12)160,000 (12)160,000 (11) 80,000 ( 9) 19,711 ( ?) ? ( ?) -
* 1,400,238 * 961,157 * 330,122 * 105,713 ? 166

orbit radii in LS
0 100
1 190
2 359
3 499
4 758
5 1200
6 2595
7 4760
8 9591
9 19,711
10 40,000
11 80,000
12 160,000
13 320,000</pre>[/QUOTE]