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Ecliptic Plane and System Traffic

Do you think that starcraft and starship travel in a system lies, more or less, on the ecliptic plane? I was thinking that the typical jump points of 110-150 diamters would narrow down entry and exit points making piracy possible. If ships entered anywhere on the "sphere" of a 110 planetary diameters it would make piracy or military defense almost impossible it would seem.

I've read some other people's input on the topic of amount of system traffic but have yet to see anything that attempts to locate the system traffic in definable terms.

Any ideas.
To me that would make some sense that all ships eventually travel along the ecliptic. But then you have planets, and in binary/trinary systems, stars, that might travel in an eccentric orbit. Unless you have an extensive map of an eccentric orbit system, or there is some Referee reason why they wouldn't be along the ecliptic, I would see travel along the ecpliptic as a default. Possibly consider it an In-System SpaceRoute - where System Defense and Rescue Ops ships would patrol. They would only go out of that route if there was a ship detected off the ecliptic.


If it makes sense to travel along the ecliptic, and pirates know that, then the smart individual merchanter will not tdo that.

Haven't had the issue really come up, but I think IMTU piracy only works as follows:

1) Pirate supplied insider info from someone in the port or providing cargo (an employee of the company, not the cargo owner unless he's a 76-Patrons style insurance fraudsman) provides course info.

2) Pirate agents penetrate the ship as passengers or as crew recruited from the starport (long term deep cover pirate ops with the culmination being a big hit with internal help)

3) Pirates have help from the local patrol! (Or *are* the local patrol)

4) Pirates know that a jump to system X or from system X is most economically (fuel and vector wise) obtained by jumping within X volume of space (X being a subset of all the possible 100+ diameter space!). Then he lies quiet in that 100d zone waiting for an inbound or outbound.

5) Pirate smuggles something aboard a ship (or has a starport authority hook something to the hull near the jump drive controls) which will disable the ship and prevent jump.

6) The pirate is in orbit or nearspace, along with other legitemate traffic (this one works in busy or semi-busy systems) disguised as something else (not getting close enough for visual ID) - another legitemate bit of traffic. When the target ship goes outbound, they arrange to be either crossing its path or passing obliquely behind it. Since they have been hanging around for a while and are legitemate (supposedly) they get to close up before they engage, and hope to target engines and fuel early on... this is 'smash-and-grab' work. Maybe they come in 'englobement' style from a number of spots (the main corsair + other ships or small craft) that were *all* masquerading as legitemate traffic.

7) Lurk on ocean bottom where ocean refueling is expected, a la SDB.

8) Lurk in gas giant.

9) Use planetary shadowing if the economical route to the ideal jump point is (for whatever window makes sense) going to pass nearby the celestial object. Then come screaming out behind the target and hope you have more delta-V and can get him before he hits 100D.

If you use stellar shadowing, the 100D limit for stars can be rather large (out past orbit 3 in some cases...), this can mean you have to travel quite a distance inside the system in realspace. Places like that will be pirate-risky.

Piracy (most succesfully) is done by social engineering - overhearing or feeding drinks to talkative crew in a starport bar (the beautiful agent of the pirates...), bogus packages loaded aboard that the captain can't open, or by corrupt local authorities in zones out beyond the Imperium (think Mexican police...). Masquerades as local traffic or smash and grabs from behind the moon or during refueling can work, but percentages are much lower than when you have good detail on flight plans etc and can lay traps (including minefields or dormant missiles, etc) along the projected route. Similarly, men on board make it much more likely.

I wouldn't constrain ships to the ecliptic. Making piracy easy hasn't ever been something I was concerned about - I think piracy and privateering ought to be tough, then only the best survive and it becomes as much an intelligence/surveillance/human factors job as it does a spacefight.
IMTU - navigation works as follows:

Navigator plots the exit point (destination) from Jump space in the target system. As navigation is done via polar co-ordinates where the frame of reference is the primary sun - any deviation from the exit point due to navigational error is from a known spot.
Due to the uncertainty of *when* one exits from jump space (seven days +/- 10%), the endpoint (or exit from jumpspace) may be ahead of the moving planet, even with the moving planet, or behind the moving planet relative to the planet's speed itself. Example. Earth moves roughly 20,000 miles (two hexes in GURPS TRAVELLER) per combat round. As each round is 20 minutes, missing your exit point by 6 hours has the effect of the planet itself having moved some 36 hexes (roughly 360,000 miles). Smart navigators in my traveller universe plan to exit jumpspace ahead of the planet by several hours so that they can wait for the planet to catch up with their exit point. If they show up REALLY early, they have a bit of a wait - which they can shorten by moving towards the planet. If they arrive really late, they've already planned for this so that they aren't TOO far behind the planet and can catch up to it. If they guess lucky about when they emerge, they will have the best of all worlds - and be almost dead on target for the shortest travel time to the world itself.

So yes, in my traveller Universe, ships arrive on the ecliptic plane - usually ahead of where the planet will be by several hours. Ships leaving the system tend to leave above or below the ecliptic (and no, I do not use the GURPS TRAVELLER jump shadow of intervening objects precipitating a ship out of jump space).
Well mainly I was curious about it because I plan on running a fairly non-rp campaign that is totally starship centric. I have some limited experience as a private pilot and I was thinking of how a "traffic control" for a planet would have to be set up to handle the variety of volumes.

In normal aircraft the are flight levels that correspond to which direction your flying to ensure you have plenty of seperation from aircraft flying intercept course near you. For instance a plane heading north may be assigned a 7500ft flight level while one going west may be assigned to 5500ft. So even though aircraft fly in three dimensional space they still operate in very two dimensional terms alot of the time.

I was thinking of how such a system would have evolved to handle ship traffic appearing in system at very high velocities. I would think there would have to be some standard operational guidelines to reduce the chance of problems arrising when you've got several hundred ships arriving every hour for the larger trade systems. That made me wonder about the possibility of ships arriving in system travelling perpendicular to the ecliptic plane to avoid pirates preying on the typical "in plane" arrival points.

For my game distances, map scales and movement are a really big part of the play time. The players want to feel like they are piloting their single ships so I can't gloss over details like some other Refs do for RP heavy games.
First, stars and their planetary disks don't necessarily rotate in the same plane as the galaxy. Second, even if my first point is discounted, in 3D space, your target system may be above or below you in the galactic plane. That said, more than likely the shortest distance course plotted to a 100d limit will not be aligned with the plane of the star system.

To adjust for this; IMTU, astrogation works like this:

1. Data - Everytime you log a flight plan with the local starport control (which is an Imperial legal requirement), your navigation database is updated. This gives you updated positions and orbital algorithms for the system you are in, any systems you are passing through, and the target system you are going to. Maintaining and updating this information at the starport is a full time duty of the Imperial Scout Service. Warships receive this information free, merchants and privates must pay a small fee. If you are inspected by Customs or the Patrol and do not have updated nav data, you are fined for endangering fellow spacers.

2. Plotting - Navigators plot star to star jumps, using other stellar objects or navigation aids (more on this) as reference, off setting the precip point to end up where they want to. The better the navigator and nav data, the better the chance of jumping in where they want to be.

3. Aids - The Scout Service maintains an extensive network of navigation aids (i.e. buoys) to direct instellar craft to safe jump points. Safe is meant to imply free of debris, masking, etc. These buoys radiate a distinct gravimetric signal which is detectable by ships in J-space. Merchants are required by their insurers to use these aids, when available. Most privates use them too. The military uses them when convenient but often times uses other methods.

4. Computing - Nav computers make course corrections in flight. The initial trajectory for a jump is 99% of the work, but as the ship approaches its target precip point, the computer can/will make course corrections to account for any errors or unforseen circumstances (rogue planetoids, traffic in the jump point, etc.).

IMTU, the computer initiates precip at 100d, not the J drive (although they are integral parts of a whole). The nav comp uses the sensors and J drive metrics to detect gravitic anomolies and determine grav well curves. When it detects a significant grav well (i.e. 100d limit), the comp initiates precip as a safety measure. But that doesn't mean it ignores other grav signatures; it can use recognized signatures as navigation aids (buoys, nearby gas giants, pulsars, etc.) to determine relative position in a system.

Military sensors, being more sensitive than commercially available models, are able to track grav points to high accuracy, allowing pin point navigation without need for artificial nav aids.

One other general comment; why would you want to travel in the plane anyway, that's were all the junk (i.e. planets, asteroids, dust, etc.) is.
I am not sure about the most debris being in the ecliptic plane. In our own system 7 of the 9 planets are in the plane. Mercury and Pluto being 7 and 17 degrees out of it respectively. The asteroid belt exists mainly in the ecliptic plane as well but there are millions of things orbiting the sun at all sorts of angles off the ecliptic.

See the Halley's comet orbit


Check out this nifty tool from nasa that gives you a moveable 3d map of near earth objects.


My point being that there are countless pieces of rock all around the sun in various orbits so I'm not sure we can say that travelling in the ecliptic plane is more or less "dangerous". I read that Jupiter's intense gravity well is one of the primary reasons asteroids from the belt outside Mars don't come zooming towards the inner planets on their way into the sun. So perhaps the ecliptic is actually the safer travel path because the planets are exerting more control on objects near the plane as opposed to ones that come flying in perpendicular to it. Maybe someone who knows more about astronomy than me can clairify this.
Originally posted by chrome_gnome:
I am not sure about the most debris being in the ecliptic plane. In our own system 7 of the 9 planets are in the plane. Mercury and Pluto being 7 and 17 degrees out of it respectively. The asteroid belt exists mainly in the ecliptic plane as well but there are millions of things orbiting the sun at all sorts of angles off the ecliptic.

My point being that there are countless pieces of rock all around the sun in various orbits so I'm not sure we can say that travelling in the ecliptic plane is more or less "dangerous". I read that Jupiter's intense gravity well is one of the primary reasons asteroids from the belt outside Mars don't come zooming towards the inner planets on their way into the sun. So perhaps the ecliptic is actually the safer travel path because the planets are exerting more control on objects near the plane as opposed to ones that come flying in perpendicular to it. Maybe someone who knows more about astronomy than me can clairify this.
You're right that there are plenty of objects outside the ecliptic, but there are still far fewer objects well outside the plane than there are within or near it. Most objects are within +/- 20 degrees of the ecliptic, and the further off you go from the ecliptic, the less likely you are to encounter anything.

The "control" planets have on objects isn't really an issue. An asteroid wouldn't just randomly change directions seemingly on a whim if it was beyond the ecliptic. In fact, the opposite is more likely - the gravitational effects of planets can divert otherwise harmless objects into potentially dangerous orbits that they wouldn't otherwise be in.
To further beat this horse:

The Scout Service in the 3I would/should be more than capable of cataloging any "near main world" objects and including them in any navigation information they publish.

Rogue asteroids and comets, particularly those passing through the inhabited region of the system, would/should be detected much farther away than we currently can, particularly with patrolling spacecraft. Great effort would/could be made to prevent rogues from entering the navigation lanes to and from any high pop world, whether destroying or redirecting the offending object into a more favorable orbit.

Plenty of reasons to continuously update nagivation information.
For high pop, high tech worlds, sure. For low pop frontiers? Probably not so much. And I'm reasonably certain that a lot of pirates would rather pick at individual merchants without much support on the edges of civilization rather than risk a concerted sweep by a high-pop planets powerful system defence forces....
^ Well, that's the rub, Kal. If you're a pirate, you have to do business on the fringe because otherwise there's too much heat. But on the fringe, where navigation is more "seat of the pants", you never know who's going to show up where around the 100d sphere. You have to be smart and take advantage of the terrain. Makes the set up a much more profitable venture than blind luck.

Now, once a ship has entered the grav well, if you could strike before it hits atmosphere; that would be best. So you need stealth or a really good poker face to get close. Makes the set up even more likely to be the tactic of choice.

But nothing beats a 2-3g advantage in a stern chase to the jump point.

IMTU, pirates gather where precip is forced or necessary, like at a gas giant or in uninhabited hexes between two trading partner worlds. A trader precips, finds itself immediately underfire, and gets boarded before the J drive has a chance to re-energize the grid. If the pirates were smart, they have an agent onboard who takes care of the details so the resistance is nullified.

Even today, piracy on the high seas is very rare; most piracy occurs where ships are forced to transit a narrow passage (such as the Straits of Malacca) and there is plenty of cover for the attackers. A certain lawlessness helps but even Malacca is routinely patrolled by Indonesian, Malay, and Singaporean navy vessels. It's the volume of traffic through the passage that makes anti-piracy efforts difficult.

But back to the topic; if you were a pirate looking for cover, you'd probably stick to the plane of the system where debris or moons or other phenomenon could hide your presence or approach. Firing up your drive when masked then coasting is much better than the alternative. Away from the plane and you stand out anytime you alter course as your aspect and albedo change.
IMTU, it's a little different...

Most ships travel on the line between source world and target world, so that preserved relative vector is towards the target world post jump. Only in-system shipping is going to even think about the ecliptic plane, and that because most use modified hohman transfer orbits.

Pirates are going to wait out just beyond the dropout points for the various worlds.

Canny individuals might choose some unusual angles and jump targets, but anything besides the Burn-out jump burn-in mode adds distance to the N-space portions of the journey... due to clearing 100-diameter limits.(Which, BTW, I calculate from the center of the world, not the surface.) Doing this adds time, but decreases encounter chances slightly.

Of course, I'm a "Low Shipping volume" heretic, too.
Aramis that is kind of what I was wondering. If you take two planets and use their cartesian coordinates you can arrive at the shortest path between them. I somewhat envisioned ships accelerating along this path towards the 100d jump point, entering jump space and then coming out on the same path, more or less, than you were on originally. My thinking was that these points of inbound traffic would be well known arrival areas. A given planet would have one arrival/departure "point" for each planet with 1 jump of it. Ships would arrive near that point aimed at the planet more often than not. Outbound ships would be heading towards that point to jump out of the system as well.

I wondered whether for traffic control reasons either inbound or outbound ships would have standard operating paths to prevent "crowding" on the inbound/outbound path for a system heading towards another system.

In a graphical sense I am pondering how big these "corridors" in space would be. Also it would seem to be somewhat dificult for pirates to linger in the area because they would need to be travelling at a pretty high speed to catch up to ships entering the system at a full clip. Even with high G drives if there is a large difference in velocities the pirate will require up to half the distance to the planet to close on a target. Perhaps the pirats might "orbit" the entry points making large loops where they pass parallel to the entry vector to slide along side a recent system entry. If nothing is present on their pass past the point they would maintain velocity and make an elliptical orbit and make another run along the known path. I can envision pirates using such a technique to make repeated passes at the point from above and below the true vector most merchants will arrive on to be headed in basically the right direction and at an appropriate speed for pursuit.

I picture this somewhat like an interstate on-ramp and off ramp setup. The merchants are on the "highway" and the pirates will come down the on ramp see if anyone is on the interstate and if not they get "off" at the next exit and circle back around to the on ramp for another run. Except in 3D space the pirates could keep moving the location and relative angle of the "on/off ramps" all around the merchant vector. In the end if you plotted the paths it might look like an electric motor with the shaft(merchant path) surrounded by winds and winds of coil wire (pirate loops).

No doubt this is a point that most overlook but for MTU I feel the need to understand how things flow so I can have a consistant and believeable operation of NPC ships around the players. In this way the players can see things out of the ordinary for themselves rather than me having to tell them they think something is odd about the vector on that ship.

Plus it is a gearhead hobby
I was going to say the same. It goes back to that ATC (sorry, Air Traffic Control) thing mentioned by chrome-gnome. Along the regular jump routes, there will be "standard" in/out lanes. Most folks would stick to these for the same reason most people won't drive from their house to the store without using the road - much easier. Of course, some people will always go the wrong way down a one way street. Over and under is a great way to separate departures and arrivals.

The thing that is worrisome about jump-in/out in the ecliptic is that if most of the mass in the system is IN the ecliptic, then wouldn't you run into problems with the 100D limit? After all, there is almost always some planet or another between us (Earth) and the nearest star system, right? So, you go out to Earth's 100D and jump... only to promptly re-enter n-space because you crossed the 100D line for Jupiter. You could go out at an angle, but what if all the planets in that system happen to be on your side (that is, the side through which you need to jump) of the sun that month? If you travel up or down far enough to clear all the 100D limits, then your direction of jump is practically limitless.
BTW, one of the other high-tech innovations in my extra-Imp technocracy is the jump speed bump (called the jump-bump). The scientists were trying to build a permanent jump "tube", so that ships wouldn't need to carry a jump drive to travel within the pocket empire. They would fire up two special jump drives at each location, which were quantum-linked. It worked great! Except that they could never get the ends of the tunnel to open. So, the j-drives would simply hang in j-space, with this jump bubble strung between them.

Well, the advantage is that the tunnel acts as a gravitic field to ships in j-space. It forces them to precipitate out of jump. The empire has strung nets of these on the direct lines to the nearest star systems at a certain jump distance. This allows robotic sensor ships to pick up any inbound foreigners so a reception committee (read dreadnoughts) can be prepared. The technocracy's ships can go around these jump-bumps because their micro-jump drive allows for an arced approach.
^ I like that idea, Fritz. Sort of like the Interdictor class cruisers in Star Wars except you could force precip over considerable distances.

You could conceivably use this technology to blockade a world. Might be a military secret!
Well, it IS a military secret, insofar as it only exists in the technocracy IMTU. These are the same folks with micro-jump (which, BTW, is only micro when your perspective is interstellar distances). The ONLY people in and out of the technocracy ARE the technocracy.

You can also use this to set up a minefield. Set up the jump-bump net, then set a massive minefield in n-space. Those exploratory ships, go out, but they never come back....
I also use micro-jumps IMTU. I have one trinary system where it is almost a requirement because the stars tend to mask the main world. Because the world orbits inside the orbit of the nearest companion star, safe navigation requires you to jump in near the companion, alter course, and then micro jump the remaining distance to the main world. That or make a 4-5 day transit at sublight speed. Some cargo transfers occur at the jump point for this exact reason.

One of the reasons I adhere to my house rules is to allow my players to skulk about; it is a rebellion setting after all. Giving them the option of entering a system anywhere they want allows them to create tactics to avoid detection or enter/exit systems covertly.

It's not meant to sound like any easy accomplished feat. It does take great skill to plot a pin point jump effectively, and unfortunately few PC's in any campaign have Nav skill greater than 2. So to compensate, I shifted everything to the left, making civilian navigation very easy because there is so much help available. In addition to navigation buoys, and highly accurate, up-to-date nav data, you have monitored travel lanes, designated approach and departure vectors, designated jump points, and even the potential of positive automated control by starport control computers. Hands off is an understatement particularly in high traffic areas. The crew exist only to respond to emergencies (which is how the insurers like it).

That said, IMTU, civilian navigators must carry a skill level of 1 or better but they really don't need to. Most starports will even process jump data and provide plots to anyone willing to pay for them. Military and scout navigators learn the hard way which makes them worth their weight in lanthanum when they get out, particularly to smugglers and pirates.

Nav comps are more flexible and capable as well; the better the comp, the less work the navigator has to do. Military computers are far better (and far more expensive) than anything on a civilian ship. You'd have to expect scout and military craft to be more capable, particularly when they travel outside normal shipping routes.

Sort of like the difference between needing paper charts to navigate versus using a Garmand GPS with color readout and chart overlays. Why would anyone do it the old way when you don't have to?
Aahh, but we do still do it the old way... Our navigators (when we still had them) on the KC-135 still took celestial shots for navigating over the polar regions and in case every other system was knocked out (Strategic Air Command thinking, there).

And, of course, that is why the military folks would tend to be much better navigators than their merchie counterparts.

BTW, my technocracy engages in a small amount of piracy to keep tabs on things in the 3I. They are also big on Q-ships for that same reason. The micro-jump is perfect for that. Fortunately, noone else has figured it out yet....