System Jump Point v Habitable Orbit Stars

[Maccat]

Stars where the 100d limit for jump from the star is greater than the (standard) Habitable orbit, and distance in Mkm to reach the star's 100d jump limit from the habitable orbit:

K0IV 78.6Mkm
G5V 20.4
K0V 9.975
K5V 49.33
M0V 38.071
G5VI 13.592

This data derived from the Scouts book (thanks for putting the table in um sol radii argh! lol) These systems would be ones where standard jumping in results in you being millions of kilometers from the habitable planet; you have a burn to get there. These are the interstellar jump "bumps in the road". Think adventure hooks.

They also serve very well for system defense, the enemy cannot jump in any closer, so you might have a chance to intercept them before they get to the world. These would also be great pirate lurking systems, ships will have to travel a fair ways to get in/out system.

This is (sort of, I actually like this aspect of traveller) in response to a thread about piracy viability, something along the lines of "It's impossible because all you have to do is patrol the 100d limit of the world" here it's the 100d limit of the *star*! A similar situation arises when the habitable planet is a moon of a gas giant. Or (heh) a gas giant moon in any of the habitable orbits of the stars above <s>. Lastly, other orbits are quite possible in the scout system gen, so the situation can arise in other cases. These though have the niceness of being habitable zone planets. Odds are any system of the above stars (ALWAYS using continuation system!) will have this predicament. Hope it helps, and enjoy!

 

[Whipsnade]

Maccat,

Check your numbers again.

Sol is a G2V type star and Earth orbits outside of the solar 100D jump limit. In fact, Earth's own jump limit orbits outside of the solar limit.


Regards,
Bill

 

[Maccat]

G2V would round down to a G0V (with no problem, actually it's 144.56MkM for 100d, Hab orbit for G0V 149.6Mkm), the G5V it's 20.4 million km. I just worked it up off the scout book tables for solar radii (1.39Mkm dia for sol) then xreferenced with habitable orbit Mkm distances (pg 28). I guess you could interpolate the various 123456etc star sizes. You could also have eccentricity effects as well lol. thanks!

 

[rancke]

This is (sort of, I actually like this aspect of traveller) in response to a thread about piracy viability, something along the lines of "It's impossible because all you have to do is patrol the 100d limit of the world" here it's the 100d limit of the *star*! A similar situation arises when the habitable planet is a moon of a gas giant. Or (heh) a gas giant moon in any of the habitable orbits of the stars above <s>. Lastly, other orbits are quite possible in the scout system gen, so the situation can arise in other cases. These though have the niceness of being habitable zone planets. Odds are any system of the above stars (ALWAYS using continuation system!) will have this predicament. Hope it helps, and enjoy!

You're quite right about worlds in the life zones around K and M stars being inside the solar jump limit. But unless I've missed or forgotten one, there has never been a system description that actually made use of this fact (with the sole exception of one I wrote for JTAS Online). Nor, to my knowledge, has jump masking ever featured in any calculations about the cost of interstellar transportation, all calculations being based on the assumption that the ship jumps from planetary jump limit to planetary jump limit without wasting time clearing the solar limit.

But a solar jump limit doesn't help the pirate much, because it either means that the system defenses place a picket at the solar jump limit or that the pirate has to be really lucky to have the prospective victim jump in close enough to where the pirate is lurking to let the pirate even detect it, much less chase it down.

Unless, of course, you're letting the pirate's detectors spot arriving merchants easy, in which case local defenses have the same advantages when trying to detect pirates.

They also serve very well for system defense, the enemy cannot jump in any closer, so you might have a chance to intercept them before they get to the world. These would also be great pirate lurking systems, ships will have to travel a fair ways to get in/out system.

Every advantage a pirate derives from local conditions are countered by the local defenses having the same advantages of detecting and chasing down the pirates.


Hans

 

[Maccat]

I was thinking of a time/distance is opportunity thing. It opens the possibility of a "high G" intercept; sluggo the 1G trader jumps in, starts burning toward the world from the star's jump limit, meanie the pirate burns at 3G to intercept.

Important is that it would be beyond the worlds defenses, regardless no?

As regards a picket i never imagined such precise arriving, more wiggle room somehow on the distance, the idea being on the surface of the 100d star jump limit is a LOT larger surface than the 100d limit for a planet. Personally I'd assume the defenses would launch to intercept if anything happened. Intercepts/flybys with a second to match the soon-to-be-maneuverless prey might work as well say around the turnover, delta Vs get semi high. Or is each merchant escorted in?! Economically, looks like it takes *some* time, but still within a merchant's week in system, maybe just a shorter liberty.

Mostly it's just more room for maneuver, something different than standard 100d jump thing. Has an aspect of "terrain" as regards systems and jumping. Like I say, for adventure hooks; maybe if you don't buy a jump tape to these star systems, and plot it out "standard" 100d from the planet, instead you jump in on the surface of the star 100d limit (and all legitimate traffic uses tapes, so there is no picket. you are also assumed to be a smuggler/pirate as well lol). Or maybe the correction for that only gets covered in Navigator-2 class? Maybe the jump tapes for *exiting* the system cost an extra 5KCr!


Posted a table with the travel times in the "forms and charts" of the file library here, but to summarize:
(Dd HH:MM:SS, 2d 01:15:13 = 25:15:13)

K0 IV
1G 2d 01:15:13, 2G 1d 10:49:39, 3G 1d 04:26:11, 4G 1d 00:37:36, 5G 22:01:36, 6G 20:06:27

G5 V
1G 1d 01:05:32, 2G 17:44:34, 3G 14:29:13, 4G 12:32:46, 5G 07:50:48, 6G 07:09:47

K0 V
1G 17:32:46, 2G 12:24:25, 3G 10:07:49, 4G 08:46:23, 5G 07:50:48, 6G 07:09:47

K5 V
1G 1d 10:16:43, 2G 1d 03:35:27, 3G 22:31:40, 4G 19:30:35, 5G 17:27:00, 6G 15:55:46

M0 V
1G 1d 10:16:43, 2G 1d 00:14:19, 3G 19:47:27, 4G 17:08:21, 5G 15:19:47, 6G 13:59:39

G5 VI
1G 20:28:54, 2G 14:28:58, 3G 11:49:30, 4G 10:14:27, 5G 09:09:35, 6G 08:21:42

 

[rancke]

I was thinking of a time/distance is opportunity thing. It opens the possibility of a "high G" intercept; sluggo the 1G trader jumps in, starts burning toward the world from the star's jump limit, meanie the pirate burns at 3G to intercept.

And stalwart the patrol ship burns at 4G to intercept the pirate.

Not to mention that if the pirate is close enough for his sensors to show the merchant, he is close enough for the patrol ship's sensors to detect him. True, if the merchant is broadcasting his ID, he can be detected at much longer ranges, but if there are pirates around, why would he be communicating with system control by broadcast instead of by laser?

As regards a picket i never imagined such precise arriving,

According to Marc Miller, "jump drive is accurate to less than one part per 10 billion. Over a jump distance of one parsec, the arrival point of a ship can be predicted to within perhaps 3,000 kilometers (on larger jumps, the potential error is proportionally larger). Error in arrival location is also affected by the quality of drive tuning and by the accuracy of the computer controlling the jump; these factors can increase jump error by a factor of 10."

...more wiggle room somehow on the distance, the idea being on the surface of the 100d star jump limit is a LOT larger surface than the 100d limit for a planet.

Yes, but a merchant will want to arrive as close to the destination world as possible in order to minimize travel time. If he comes from the other side of the star, he needs to clear the solar jump limit, but then he can select from a huge circle of equidistant arrival points, which means a lurking pirate is only covering a small slice of the potential arrival points.

Still , it's probably those trips that offer the pirate the best opportunity to intercept a merchant.

Personally I'd assume the defenses would launch to intercept if anything happened. Intercepts/flybys with a second to match the soon-to-be-maneuverless prey might work as well say around the turnover, delta Vs get semi high. Or is each merchant escorted in?!

Dpends on the size of the planetary defense force and the number of arriving and departing ships.

Economically, looks like it takes *some* time, but still within a merchant's week in system, maybe just a shorter liberty.

Time is money to a merchant. If a free trader usually spends five days in a system looking for freight and passengers, then it's because four days isn't good enough. But I was thinking about regularly scheduled liners and freighters, which I always assume unload and load in hours rather than days. To them, a turnaround time of 10 days means being able to make 35 jumps per year while 11 days means ~32 jumps per year. That will affect transportation costs.


Hans

 

[shaunhilburn]

Stars where the 100d limit for jump from the star is greater than the (standard) Habitable orbit, and distance in Mkm to reach the star's 100d jump limit from the habitable orbit:

I have a table that shows transit times to jump distance from an Earth-equivalent HZ orbit, based on a star's temperature and diameter.

The maximum transit Time-To-Jump from an HZ orbit is near M0V stars, around 27 hours @ 1G. The forum screws up monospaced fonts, so I can't post the chart here.

 

[boomslang]

The forum screws up monospaced fonts, so I can't post the chart here.

Simply use the CODE tag before and after the text you wish to have appear in a monospaced font. It works similar to the QUOTE formatting tag... just do not forget to close it at the end of the passage.

It displays as follows:

Here is some monospaced text.

And here is some more regular body text for comparison.

 

[Renaissance Man]

So much about piracy (and its feasibility) seems to depend on the attitude toward stealth in space. The two holy wars seem to have a direct lineage.

Jump drive limits vs. habitable zones may well be an adventure hook. But they aren't going to convince a die-hard anti-pirate.

However, I must say, it seems strange to me that one can assume the existence of well-patrolled jump pickets in a system where the mainworld has a C or D class starport. If you can't put together a decent downport (let alone highport), the notion of these pickets, replete with sensors and patrol vessels seems out of place.

Myself, I buy most of the arguments against both stealth and pirates. But I don't subscribe to the idea that every system has the resources, TL, inclination or priority with the Imperium to repel piracy full stop.

 

[aramis]

The real defining point for piracy is the predictability of jump entry and exit points for a given target system.

If, for a given time, a jump from system A to system B (SysA and SysB henceforth), you can predict the SysA jump entry point for going to SysB, and for SysB, you can predict the exit point for SysA, then you can arrange for being at that point, and can have easier piracy and system defense.

If, for SysA->SysB there is an optimal path that results in knowing the jump entry/exit points, even if not the only path, one can engage in piracy on those paths, but again, system defense is also more capable of defending the system. It's weakly implied in TNE that a bingo jump is this kind of relationship.*

If for that same SysA->SysB, a narrow set of n-space paths exist to jump from/to, and these can be predicted, again, piracy is more possible, but also system defense.

If the SysA->SysB exit point is also a SysB->SysC Entry Point, then it's a stronger pirate kind of place, since a pirate can jump out for SysC if the heat is on in SysB. If the Entry for SysB->SysC is far from the exit for SysA->SysB and from entry for SysB->SysA, exit piracy is FAR less likely, as pirates can be pursued by local forces while attempting to reach jump entry.

If you can't predict SysB Exit points, but can predict SysA Entry Points for jumping to SysB, you can't defend the system well, but can have piracy at the SysA end...

If the range of Entry points in SysA is significant, piracy is weakened at the departure end, since departing ships can pick any of a wide range of places; it is also safer for the pirate, since it's more likely he can escape to SysB. Conversely, if the allowed range is narrow, then piracy at jump entry is more doable by virtue of having everyone nearby; likewise, tho, it makes it more dangerous, since local forces can patrol it, too.

If there are a small range of exit points, the system can be defended easier, but also exit piracy is easier, since the prey is more likely to be in reach. It also means that system defenders are more likely to be able to engage pirates quickly. A wide range means less easily patrolled, and thus harder piracy, but also less likelyhood of defense forces intercepting pirates.

If the entry/exit points are consistently in a spot where one can put an object in a stable orbit, then entry/exit points become fortress locations...

Given the major variables:

• range of entry points possible
• range of exit points possible
• separation of entry and exit points
• variability of usefulness of given entry/exit points
• variability of ability to patrol

it's possible to have them in a range where piracy is relatively possible for a given set of economic and naval circumstances.

* A TNE Bingo Jump is one that uses one's outbound residual N-Space vector to put one into a free return capture to orbit aroung the target world. Since it's a critical result, it appears that you can set up an optimal exit point solution; the question is the range of entry points possible; few or many?

 

[rancke]

The real defining point for piracy is the predictability of jump entry and exit points for a given target system.

And for the OTU, we know that jumps can be predicted to within 3000 km (multiplied by the distance in parsecs) in space and to within +/- 17 hours in time. The time variation is one of the pirate's biggest problems (in defended systems, that is) when gunning for a specific target , because an innocent merchant does not want to stay put anywhere for a second more than they need to. Time is money to a merchant. The typical arrival would remain stationary until it has contacted traffic control and been assigned a flight path, no more. Any ship that loiters near the emergence zone risks arousing the interest of system defense PDQ. Unless, of course, it is somehow protected by a "stealth field".


Hans

 

[aramis]

Actually, Hans, for these purposes, we have no idea from what I've read of predictabiity from outside the ship jumping. It's one of those gray areas in the setting. It doesn't matter if the ship knows where it's going, what matters is if others can predict where a ship is going to jump from and to. It's utterly immaterial how tightly the ship can predict if the pirates can't.

 

[shaunhilburn]

Simply use the CODE tag before and after the text you wish to have appear in a monospaced font. I works similar to the QUOTE formatting tag... just do not forget to close it at the end of the passage.

    Type   Msun      Lsun         Rsun     Temp K     HZ AU     JD AU
---------------------------------------------------------------------
    B0V   17.50    55,147         10.00    28,000    234.834    9.308
    B1V   14.20    31,219          8.60    26,190    176.691    8.005
    B3V    7.60    12,069          7.20    22,570    109.860    6.702
    B4V    6.70     5,606          5.80    20,760     74.873    5.399
    B5V    5.90     2,239          4.40    18,950     47.328    4.096
    B6V    5.20     13,40          4.16    17,140     36.607    3.872
    B7V    4.50       761.4        3.92    15,330     27.594    3.649
    B8V    3.80       406.0        3.68    13,520     20.149    3.426
    B9V    3.40       199.6        3.44    11,710     14.129    3.202
    A0V    2.90        88.3        3.20     9,900      9.394    2.979
    A1V    2.70        66.3        2.92     9,650      8.145    2.718
    A2V    2.50        48.8        2.64     9,400      6.987    2.457
    A3V    2.40        35.0        2.36     9,150      5.918    2.197
    A4V    2.10        24.4        2.08     8,900      4.935    1.936
    A5V    1.90        16.3        1.80     8,650      4.034    1.676
    A6V    1.80        14.2        1.78     8,400      3.762    1.657
    A7V    1.80        12.3        1.76     8,150      3.502    1.638
    A8V    1.80        10.6        1.74     7,900      3.253    1.620
    A9V    1.70         9.1        1.72     7,650      3.015    1.601
    F0V    1.60         7.8        1.70     7,400      2.788    1.582
    F1V    1.60         6.7        1.64     7,260      2.589    1.527
    F2V    1.50         5.8        1.58     7,120      2.399    1.471
    F3V    1.50         4.9        1.52     6,980      2.218    1.415
    F4V    1.40         4.2        1.46     6,840      2.046    1.359
    F5V    1.40         3.5        1.40     6,700      1.882    1.303
    F6V    1.30         2.9        1.32     6,560      1.707    1.232
    F7V    1.30         2.4        1.25     6,420      1.541    1.162
    F8V    1.20         1.9        1.17     6,280      1.384    1.091
    F9V    1.10         1.5        1.10     6,140      1.238    1.020
    G0V    1.10         1.2        1.02     6,000      1.100    0.949
    G1V    1.00         1.1        1.01     5,890      1.050    0.940
    G2V    1.00         1.0        1.00     5,780      1.001    0.931
    G3V    1.00         0.873      0.97     5,670      0.934    0.903    1G Hrs
--------------------------------------------------------------------------------
    G4V    0.90         0.758      0.94     5,560      0.870    0.875     3.29
    G5V    0.90         0.655      0.91     5,450      0.810    0.847     9.39
    G6V    0.90         0.601      0.91     5,340      0.776    0.845    12.81
    G7V    0.90         0.551      0.91     5,230      0.742    0.843    15.42
    G8V    0.80         0.504      0.90     5,120      0.710    0.841    17.61
    G9V    0.80         0.460      0.90     5,010      0.678    0.840    19.50
    K0V    0.80         0.419      0.90     4,900      0.647    0.838    21.18
    K1V    0.80         0.319      0.83     4,760      0.565    0.774    22.22
    K2V    0.70         0.239      0.76     4,620      0.488    0.711    22.90
    K3V    0.70         0.175      0.70     4,480      0.418    0.648    23.24
    K4V    0.70         0.126      0.63     4,340      0.354    0.585    23.28
    K5V    0.70         0.087551   0.56     4,200      0.296    0.521    23.03
    K6V    0.60         0.075360   0.56     4,060      0.275    0.518    23.92
    K7V    0.60         0.064552   0.55     3,920      0.254    0.514    24.73
    K8V    0.60         0.055007   0.55     3,780      0.235    0.510    25.47
    K9V    0.50         0.046612   0.54     3,640      0.216    0.506    26.15
    M0V    0.50         0.039260   0.54     3,500      0.198    0.503    26.77
    M1V    0.50         0.027902   0.50     3,333      0.167    0.467    26.59
    M2V    0.40         0.019432   0.46     3,167      0.139    0.432    26.24
    M3V    0.30         0.013188   0.43     3,000      0.115    0.397    25.75
    M4V    0.30         0.008700   0.39     2,833      0.093    0.361    25.11
    M5V    0.20         0.005561   0.35     2,667      0.075    0.326    24.32
    M6V    0.20         0.003154   0.30     2,500      0.056    0.279    22.92
    M7V    0.15         0.001661   0.25     2,333      0.041    0.233    21.26
    M8V    0.12         0.000791   0.20     2,167      0.028    0.186    19.29
    M9V    0.10         0.000323   0.15     2,000      0.018    0.140    16.92

Msun: Solar masses (sun =1)
Lsun: Output (sun = 1)
Rsun: Radius (sun =1)
Temp K: Effective photosphere (Kelvin)
HZ AU: Earth-equivalent distance, based on bolometric output (AU)
JD AU: 100-diameter jump distance (AU)


The table shows the 1-G *no-braking* transit time from a world embedded inside the 100-diameter stellar jump distance, Hrs = sqrt(AU/G)×48.5193

A 2G ship takes 0.707 times as long as a 1G ship, sqrt(1/2).
A 3G ship takes 0.816 times as long as a 2G ship: sqrt(2/3).

If a crew wants to stop and loiter at the jump threshold, then the braking transit time = Hrs x sqrt(2) = sqrt(AU/G)×68.6167