Jump Shadowing/Masking

[Condottiere]

Assuming you give any physical object, regardless whether it's a pebble or spaceship, a gravitational influence, an exiting starship would only have it's flight path deflected, or if it's head on, bounced back.

 

[fusor]

Assuming you give any physical object, regardless whether it's a pebble or spaceship, a gravitational influence, an exiting starship would only have it's flight path deflected, or if it's head on, bounced back.

It doesn't help when people say things like this as if they're from some published set of rules. No behaviour like this has been mentioned, and it only serves to confuse the issue even more.

 

[Infojunky]

All of this is why there's been 30-odd years of argument around the topic .

Yep. I have been watching this debate for decades now, and meanwhile it feels a bit like in the Groundhog Day movie, an endless repetition.

Welcome to the Mongoose Traveller Forum, where all old arguments are New again....

In the end one can either accept the rules as they are ("It's Traveller's alternate universe ...") or replace them with other rules one likes better ("In my Traveller universe ..."), but the discussion with the hope that there will be a final result everyone can and will agree on would probably go on until the guys with the straitjackets appear on the scene. And the 100D limit is not the only topic of that kind, there are also the economy of piracy, stealth in space, Aslan footwear ... :shock:

The Core thing to remember is that Every Traveller Game is different. Even within the same group....

OB Topic; My take on the 100D limit and Jump Points are that on Jumplines between systems the location of the Jump out point and Jump in point are similar. I.e. using the standard course from one Star Port to the Next, Traffic departs and and arrives in the same general areas. These point tend to be around the 100D Limit.

 

[Nerhesi]

Late joiner.. so wait..

Is the 100D of a star further than the 100D of the orbiting planet? I'm asking a question I know the answer to dont I?

"Depending on how far the planet orbits the star and the star - so do the calculation and figure out if you're arriving at 100D from the star or 100D from the planet?"

Say it aint so!

 

[mancerbear]

OB Topic; My take on the 100D limit and Jump Points are that on Jumplines between systems the location of the Jump out point and Jump in point are similar. I.e. using the standard course from one Star Port to the Next, Traffic departs and and arrives in the same general areas. These point tend to be around the 100D Limit.

I would assume, especially planets with Class A, B, and C starports, that flight paths would be monitored closely, and jump points assigned by the starport (just like airports control the airspace around them). Space is big, no doubt about it, but you don't want the risk of a collision in space, or flight paths crossing. Of course, there's no way to know when and where a ship will precipitate out of jump, except somewhere on the edge of the 100D limit, but you can certainly direct traffic out to the limit. Once a ship appears from jump, I imagine the Starport would be right on top of them, giving them an approach path and plotting their course.

Just my opinion though.

 

[Infojunky]

Late joiner.. so wait..

Is the 100D of a star further than the 100D of the orbiting planet? I'm asking a question I know the answer to dont I?

"Depending on far the planet orbits the star - so do the calculation and figure out if you're arriving at 100D from the star or 100D from the planet?"

It all depends on the Star..... (Which the base rules don't cover, so Go Figure)...

 

[Reynard]

Scouts gives a very simple Jump Shadow rule. No actual star but you generate the shadow then the rest of the system. There's a chance the orbit of a destination world could be within the star's 100D shadow. Problem is there's no rules of actual distances so the usage is moot. Everyone goes back to the 100D of the planet rule.

 

[mancerbear]

Scouts gives a very simple Jump Shadow rule. No actual star but you generate the shadow then the rest of the system. There's a chance the orbit of a destination world could be within the star's 100D shadow. Problem is there's no rules of actual distances so the usage is moot. Everyone goes back to the 100D of the planet rule.

GURPS Starships and GURPS Far Trader gives a different method, which is easily adapted to MgT. It covers the size of the stars, their shadow, and how often a planet may fall into being masked by them. I find it very useful.

 

[Tenacious-Techhunter]

Actually that's exactly what I was referring to. Look at any Traveller star chart and there can be systems between you and your destination. The astrogator isn't just pointing the ship as the crow flies unless that is the shortest path, they are setting a series of twists and jinks all about any number of gravity bodies in their way. You're not always lucky enough to be above or below the ecliptic. So are the stars and planets at destination and you have tried to plot accordingly. A ship in jump space isn't just hanging in there, it is moving relative to our real space (which is why real space gravity still affect it) with the speed of the universe they are in. Yes, you are charting to go around the star.

Known star charts in your ship's computer are huge and complex. Once a system has been thoroughly surveyed, all significant objects movements plus the system's overall path are charted in real time and constantly updated in memory. The astrogation roll represents pinpointing the location of exit as precisely as possible even knowing every obstacle waiting for you. Yes, the computer knows what side of the star it's on.

Everyone picks on the 'retro computers' but don't seem to fathom just how much work these things are tasked with for jump as well as every other function it's performing simultaneously.

The actual, realistic computational workload of simulating the n-body problem of a ballistic trajectory that bypasses several such systems actually would fit on a Raspberry Pi 3. Add a few more in a box the size of a toaster for redundancy. The idea of the “ship’s computer” being a massive giant is obsolete. There is no scientific justification for it. NASA’s computers may be bigger, but they’re trying to solve a harder problem... meeting the same trajectory goals while desperately conserving costly fuel. Fuel isn’t costly in Traveller; nor is its conservation particularly desperate. Removing this one constraint radically simplifies the math problems to be solved. Also, the targets in Traveller are way bigger, way easier to hit, and hitting the 100D limit of any planet or star in the system is a plenty good enough fallback that is trivial to calculate as well.

Traveller GMs need to kill their inner luddite, take a damn look around at the actual, measurable capabilities of modern hardware, and realize they’ve been GMing a damn lie. The size and power requirements of an average hobbyist gaming rig is going to completely dwarf even the biggest Navigation Computer any ship is likely to need.

 

[AnotherDilbert]

I do not see your point.
Maneouvering real space takes trivial computing power, represented by Manouever software with bandwidth 0.
Calculating jumps takes much more computing power in Traveller. There is of course no current idea of how much computing power an imaginary jump would require.

Since TNE ships computers takes about no space at all, so your objection is a few decades outdated.

 

[mancerbear]

Why are we discussing computers and computing power? This thread is about jump masking. Plex stick to the topic.

 

[Tenacious-Techhunter]

Well, Mongoose Traveller 1E still had unnecessarily oversized computers and cockpits, so you’re the one that’s less informed.

 

[Tenacious-Techhunter]

Here’s a reasonable physical justification for 100D limits using gravitons (the source of gravity)...

At 100D, all spherical objects all appear to be the same size. The cone from the center of the ship to the edges of all those objects will be the same angle as well. So... if we suppose that the gravitons from nearby objects puncture the jump bubble in a way that isn’t easily repaired, regardless of how frequently those gravitons may arrive, then once the graviton cone becomes a sufficiently large size, the jump bubble pops, and the ship precipitates out of jump.

However, there are consequences... Any object 1/100th the diameter of the ship or larger could potentially precipitate the ship out of jump, because, when it hits the edge of the jump field, the graviton cone is the same size. Now, you could handwave this away with, “Well sure, but there’s bound to be a a lower limit to the graviton frequency on account of the robustness of the Jump Drive...”; however, I would argue that allowing even small things to precipitate the ship out of jump allows for interesting things to happen.

 

[Reynard]

Core book 1st ed. page 104. Hmmm....

Exactly where is the vast tonnage or any tonnage listed for any of the computer models. T-T, am I missing something? Are we looking in the same books?

 

[Reynard]

T-T, where are you getting your science 'facts'? All spherical objects appear the same size at 100D? You realize the descriptor actually means 100 diameters of that world's size code (Size table page 170) not a single abstract 100 units from the world. A size 1 world has a gravitational influence strong enough to force a jump exit or to prevent jump entry out to 160,000 km while a size 8 world will have its influence out to 1,280,000 km. There's an example for Earth, moon and sun on page 141. Not sure what the cone angle out to object refers to.

And it doesn't 'puncture' the bubble per se but the gravity field of influence disrupts the interaction holding the bubble of hydrogen and energy in balance so yeah maybe *pop*. Instantaneous and irreparable... gone. You are now in real space at the point the gravity reached the threshold to precipitate a ship. With gravity science so prevalent in Traveller, I have no doubt ship's sensors have gravitometers and you could see fields you close towards go from nearly imperceptible to a warning of imminent threshold contact, not that you can do anything about it in time. Most instances would be rises and falling as you pass by gravity wells. And only massive objects such as planets, gas giants and stars normally have the size and density ( a combination of the two) to have a sufficient gravitational effect. Phobos and Demos are too small as are the vast majority of comets, asteroids and planetoids (Less than Size 0). Pluto is 2370 km in diameter or size 1 and will have an effect. Can't be 1/100th the diameter of a 'ship' unless it's a MASSIVE blackhole.

There is just a bit of hard science in Traveller.

 

[phavoc]

If you wanted to get specific, not all massive objects are spherical, hence their area of affect wouldn't necessarily be a sphere, more like an ellipse. But for game mechanic purposes, the 100D rule works.

Because it's only science-influenced, and NOT science based, I wouldn't read too much into it or try to apply to much real-world physics either. You are just going to get into a flame war with no victors.

With gravity science so prevalent in Traveller, I have no doubt ship's sensors have gravitometers and you could see fields you close towards go from nearly imperceptible to a warning of imminent threshold contact, not that you can do anything about it in time. Most instances would be rises and falling as you pass by gravity wells. And only massive objects such as planets, gas giants and stars normally have the size and density ( a combination of the two) to have a sufficient gravitational effect. Ceres (946Km), Phobos and Demos are too small as are the vast majority of comets, asteroids and planetoids (size 0 or smaller). Pluto is 2370 km in diameter or size 1 and will have an effect. Can't be 1/100th the diameter of a 'ship' unless it's a MASSIVE blackhole.

There is just a bit of hard science in Traveller.

Are you implying here that a ships sensors would be operational and detecting things in realspace while it was in jump space? That would be a departure from the rules as they have been stated. Or do you mean that while a ship is in real space, it's sensors would be able to detect and plot gravometric influences of space objects?

The game mentions that you can't fly through an object, such as the sun, but I think most people don't try to plot out specific courses when making jump navigation plots. You'd think most ships would arrive above/below the system plane ecliptic to minimize jump shadows. But without 3D plots of star systems, their planes and moons between your departure and arrival points, all you can do is make some basic assumptions - from a gaming perspective at least. I do think having it explained in better detail doesn't detract from the game. If anything it gives referee's additional ideas to make a plot work ("Oops, it turns out your system charts you downloaded were out of date by 10yrs, thus that gas giant was out of place and pulled out you of jump space. Oooh! Lookee there! A ship is nearby..." Trying to detail it out really doesn't do much from a gaming perspective, in my opinion at least.

 

[fusor]

Here’s a reasonable physical justification for 100D limits using gravitons (the source of gravity)...

Gravitons are theoretical particles and their existence has not been proven, so your "reasonable physical justification" goes out of the window right there. The rest of your justification is just technobabble-y armwaving.

And only massive objects such as planets, gas giants and stars normally have the size and density ( a combination of the two) to have a sufficient gravitational effect. Ceres (946Km), Phobos and Demos are too small as are the vast majority of comets, asteroids and planetoids (size 0 or smaller).

Nope. Asteroids and comets can have a 100D too. Nebulae and dust clouds don't, so the physical density of the material does matter (though that can be pretty low, since hypergiant and supergiant stars also have 100D limits and they are very low density). The lower limit to what has a 100D limit has not been established. I think T5 would have us believe that absolutely everything (including spaceships) has 100D limits, but I would prefer an arbitrary limit like 1 billion metric tons or something like that, so that a floating spaceman doesn't mess up jump.

 

[Tenacious-Techhunter]

Well, let’s start with the Core Book, pages 107-108...

The basic controls do not include the ship’s computer,

Why not? It’s a toaster’s volume worth of Raspberry Pi 3s...

which is usually installed adjacent to the bridge.

Why didn’t they say “installed within easy reach behind the glass cockpit”*?

In general, larger computers are more advantageous in combat situations.

What? Don’t they mean “more powerful computers are more advantageous in combat situations”? And is either even remotely true?

Ship’s computers work just like personal computers but are considerably more powerful because the software for ship operations requires more processing power than normal programs (see Ship Software, page 113).

Bull@^*%. Name one piece of software that legitimately requires an oversized computer beyond elaborate entertainment software. Not Maneuver, not Evade, not Fire Control... Jump Control is a false argument, since that can be as complex as the fiction authors want it to be... There’s a legitimate case for “Auto-Repair” on account of it being a legitimate Artificial Intelligence problem, but since sentient robots have to be able to do that with a toaster-sized brain, that goes back in the toaster again.

So far, the only basis for an oversized computer is entirely fictional. Now, if people want to start saying “Dedicated Jump Computer”, I can’t mount a reasonable argument against that. But otherwise, the damn thing’s bunk. It should be a standard computer in every way with standard software requirements. Also, note how “Intellect” is described as some kind of TL11 Siri. The hell??? That should be our TL, and be free. Maybe there’s a case for a Rating 1 version at TL11.

Let’s move on to “High Guard”, page 65...

The rating of this central core depends on the Jump range and the size of the ship.

Uh... no it doesn’t... we’re only changing a handful of variables... mass, inertia about 3 axes... It’s still the same basic math problem!

Computers are assumed to have their tonnage included in the command modules of a ship.

“Tonage”? Computers for a job of this “complexity” isn’t measured in “Tons”, displacement or otherwise.

The Seeker Scout and Miner both show a 2dT “Computer Room”; other Mongoose 1E Deckplans are sufficiently poor that it’s hard to scrutinize them properly.


*More on glass cockpits another time.

 

[Tenacious-Techhunter]

T-T, where are you getting your science 'facts'? All spherical objects appear the same size at 100D? You realize the descriptor actually means 100 diameters of that world's size code (Size table page 170) not a single abstract 100 units from the world. A size 1 world has a gravitational influence strong enough to force a jump exit or to prevent jump entry out to 80,000 km while a size 8 world will have its influence out to 1,280,000 km. There's an example for Earth, moon and sun on page 141. Not sure what the cone angle out to object refers to.

And it doesn't 'puncture' the bubble per se but the gravity field of influence disrupts the interaction holding the bubble of hydrogen and energy in balance so yeah maybe *pop*. Instantaneous and irreparable... gone. You are now in real space at the point the gravity reached the threshold to precipitate a ship. With gravity science so prevalent in Traveller, I have no doubt ship's sensors have gravitometers and you could see fields you close towards go from nearly imperceptible to a warning of imminent threshold contact, not that you can do anything about it in time. Most instances would be rises and falling as you pass by gravity wells. And only massive objects such as planets, gas giants and stars normally have the size and density ( a combination of the two) to have a sufficient gravitational effect. Ceres (946Km), Phobos and Demos are too small as are the vast majority of comets, asteroids and planetoids (size 0 or smaller). Pluto is 2370 km in diameter or size 1 and will have an effect. Can't be 1/100th the diameter of a 'ship' unless it's a MASSIVE blackhole.

There is just a bit of hard science in Traveller.

Every object, at a distance 100D from that object, appears to be the same size as other objects you are 100D of that other object from that other object. At 100D of the Sun from the Sun, the Sun looks almost exactly the same size as the Moon 100D of the Moon from the Moon. They both take up the same “area” within the scope of your vision. Which means, if we assume their gravitons can punch through Jump Bubbles, they would also punch the same size hole through your Jump Bubble, hypothetically leading to the same Jump Bubble collapse.

 

[AnotherDilbert]

Yes, Jump space and the mechanics of Jumps are entirely fictional. It even requires fictional computers.


Siri, TL8:

well that was a small part of:

We can easily see that it takes no tonnage, and is basically free.


Sorry, Mancerbear, I will not talk about computers in this thread anymore.