Jump question

[CosmicGamer]

Similiar topics have me looking for more detail.
Question) Does a ships speed and orientation have any effect on a Jump?

If you answer yes to part one, then (to me) there would be ways to calculate information about the jump using the ships speed and orientation.

A: Yes) Are there any requirements as to speed and direction when jumping.
Yes Q1) Do you have to be going over a certain speed? Under a certain speed?
Yes Q2) Do you need to be pointing in the direction you are jumping? Some other orientation?

A: No) If you answer that a ships speed and orientation does not matter so a ship could be standing still or moving at any speed and pointing in any direction when it jumps.
No Q1) Is there anything you can determine about a ship that is jumping (departing). Distance it is going based on energy output? Direction it is going?
No Q2) Is there anything you can determine about a ship that has jumped (arriving). Distance it jumped? Direction it came from?

When posting, please indicate if these are your own personal thoughts or if they come from a source. Please state the version of traveller and the source. Thanks.

 

[far-trader]

Similiar topics have me looking for more detail.
Question) Does a ships speed and orientation have any effect on a Jump?

Yes. According to some sources at least. Well not an effect on the Jump itself, but on the consequences.

If you answer yes to part one, then (to me) there would be ways to calculate information about the jump using the ships speed and orientation.

Agreed. To a point. They would however be assumptions, not solid data.

A: Yes) Are there any requirements as to speed and direction when jumping.

No. Some sources suggest the safest and widest practice is to zero your vector before jumping.

A: No) If you answer that a ships speed and orientation does not matter so a ship could be standing still or moving at any speed and pointing in any direction when it jumps.

Correct.

No Q1) Is there anything you can determine about a ship that is jumping (departing). Distance it is going based on energy output? Direction it is going?

Again, depending on the source (rules):

a) You may be able to determine how long/far the jump is (power signature/fuel used) though a micro jump uses a J1 worth of fuel and can go exactly nowhere in real space. And from this, and the original rules, more fuel and power may be used than actual distance jumped. So while it may look like the power and fuel was used to do J3 the ship may actually only be making a J2, J1, or even a microjump.

b) You can tell which directions are "open" to it (jump would be blocked by some rules by large masses in a direct line between the entry point and exit point). Again however a micro jump doesn't have to actually go anywhere. So it would be a case of elimination, and presumption.

No Q2) Is there anything you can determine about a ship that has jumped (arriving). Distance it jumped? Direction it came from?

In MTU, distance no, direction maybe. But then I like a stealthy universe so my jump arrivals don't have a big flash burst explosion of energies associated with them and ships can arrive running silent and be very hard to detect. In MTU all the energy and flash is at the entry.

However, in some rules, the entry is anything but quiet. If you go with entry flash then yes you could determine how far they had travelled based on the energy. Though in a case of misjump that might be incorrect.

For direction, IF the arrival moment is detected then the position can be used to eliminate direction of arrival based on large masses in the direct line between the arrival point and all possible departure points. Again it's more a matter of "they couldn't have come from here, but could have come from here, here, here,... " It really doesn't take much to get outside the line of sight of the masses that would limit you from going anywhere so the information (by itself) is not terribly useful most of the time. You might use it to verify against the arriving crew's story, "We just jumped in from Wypoc, and boy are our legs tired." Or the ship's logs, "Says here you jumped from 128:635:391 Wypoc but that would have put Kedec (the local gas giant) in your jump path. Where did you really come from?"

When posting, please indicate if these are your own personal thoughts or if they come from a source. Please state the version of traveller and the source. Thanks.

Varied sources, aiming for a more complete answer. It'd be easier, if your question is for a specific rule set, to ask about that one. Some of the above is from CT (1st and 2nd editions), MT, TNE, and probably T20. And of course my interpretations and possibly incorrect (though not unsupported) at that

 

[Drakon]

These are my own thoughts:
1) When you talk about speed, you have to ask "relative to what?" The local star is the obvious choice. And on the scale that we're talking about, one can assume fixed stars. But the planets and such would be moving at different rates. So if a ship is zero speed in one system, it will not be when it comes out at the far end relative to its planets.
2) Considering the vasteness of even interplanetary space, I don't think the issue of local gas giants being in the way will crop up.
3) You would want a widely dispersed jump entrance and exit volumes, to minimize collisions. Also the various systems will have some traffic control regulations, such as all incoming ships from Deneb will exit jump space at these coordinates relative to the star, travelling at such and such a vector, within a range. Do not exceed 200 kps, do not get closer to 3 million klicks before contacting system control on 123.75.
4) Direction should be fairly simple. All the ships from Deneb will enter the system from the direction of Deneb. There is a limited number of systems that one can jump from.
5) I think you would want to enter a new system with some headway. Otherwise you have to first accelerate toward the planet, then decelerate once you get close enough. Better to enter a system with some speed, since you got to bleed any speed off for landing anyway.
6) Space traffic control regs would have Imperial wide, standardized. There also has to be a set of regs for uncontrolled or unpopulated systems. I imagine, you would need a nav bouy systems, have ships establish holding patterns or vectors relative to these bouys. If the bouys had something similar to VOR direction findings, you could assign radials to different ships. Assign one set of ships these sets of radials, and these incoming ships these other set of radials. To avoid collisions

 

[far-trader]

These are my own thoughts:

And good thoughts they are too They highlight issues I glossed over and add points...

1) When you talk about speed, you have to ask "relative to what?" The local star is the obvious choice. And on the scale that we're talking about, one can assume fixed stars. But the planets and such would be moving at different rates. So if a ship is zero speed in one system, it will not be when it comes out at the far end relative to its planets.

True. When I talk about zeroing vectors prior to jump I generally mean assuming a vector in the departure system such that your arrival vector is zero relative to approaching the destination. For simplicity I just go with the travel times listed in the table though which are based on full acceleration to 50 diameters then full deceleration to 100 diameters. An oversimplification but good enough for me. I tried figuring out the relative velocities once between planets in two different solar systems. The variables are enough that it would be a pain to do and I think it added something like a week to most trips to make up the difference. Suffice to say a handwave that jump space zeros a lot of interstellar velocity looks pretty good

2) Considering the vasteness of even interplanetary space, I don't think the issue of local gas giants being in the way will crop up.

Not often for sure But it makes a great McGuffin.

3) You would want a widely dispersed jump entrance and exit volumes, to minimize collisions.

Noting your correct statement about the vastness of even interplanetary space, there's not much danger of collisions, except around very small destinations with lot of traffic. Like a Class A Starport in a High Pop asteroid belt system.

So there would be conventions in place and regulations in some systems. Somebody proposed a simple convention of in-system travel being restricted to the planetary plane (+/- some thousands of km) and outbound jumps being made above that plane, and inbound jumps being made below that plane. So the convention is you thrust out to 100D in the planetary plane, then pop up to jump out. Inbound you arrive below the planetary plane and move up to it before thrusting in. That alone should reduce the chance of collision to practically zero even in busy systems. Add to it a radian system for where you're coming from and reduce even that chance to infinitesimally small.

4) Direction should be fairly simple. All the ships from Deneb will enter the system from the direction of Deneb.

Not necessarily. There's nothing stopping me from jumping past the destination and appear in some other part of the system than the Deneb line.

5) I think you would want to enter a new system with some headway. Otherwise you have to first accelerate toward the planet, then decelerate once you get close enough. Better to enter a system with some speed, since you got to bleed any speed off for landing anyway.

...and you come out of jump with an object directly ahead and no time to stop. Sure it won't happen often (space is big, and mostly empty, as you noted) but it doesn't sound like a good idea to press your luck.

6) Space traffic control regs...

This kind of thing really should be done in detail, by someone, officially, if it hasn't already.

 

[JAFARR]

I seem to remember reading in some of the official publications WTTE of, "Our navigator did a good job of placing us within easy refueling distance of the GG." From that, I get the idea that if enough is know about the arrival destination, the navigation plot is expected to arrive in a specific area of the system, depending on what you plan to do upon arrival in-system.

 

[rancke]

5) I think you would want to enter a new system with some headway. Otherwise you have to first accelerate toward the planet, then decelerate once you get close enough. Better to enter a system with some speed, since you got to bleed any speed off for landing anyway.

I recently came up with an explanation that I think works well. It is based on the assumption that game rules sometimes are simplifications of "real world" situations for ease of gaming.

Imagine you're aiming for a world that travels 100 planetary diameters in 15 hours. So you aim for the spot where it will be in 168 hours. Due to jump variation, you will arrive in 168 +/- 17 hours. If you arrive after 153 hours, you will be at the 100 diameter limit in the spot where the world will be in 15 hours. If you arrive after 173 hours, you will be at the 100 diameter limit on the spot where the world was 15 hours earlier. And if you arrive any time in between, you will hit the jump limit and be precipitated out 100 diameters from the world somewhere along a half circle. Only if you arrive more than 15 hours early or more than 15 hours late will you be more than 100 diameters from the world. Assuming that arrival times are distributed along a bell curve, that will happen very seldom. So the game rules ignore this possibility for the sake of simplicity.

If you're going to arrive at some unpredictable spot along a half circle around the world, the best vector to have is one that is neutral with respect to the world. Otherwise you might easily find yourself moving AWAY from the world with a vector to kill before you can move towards the world.


Hans

 

[dean]

I'd personally expect that there'd be some sort of standardization of procedure when jumping as to where entering ships and leaving ships vector, simply for safety's safe.

One system used in fiction is that departing ships depart by moving to the polar south (perpendicular to the plane of the system as a whole) and that in bounds plot to come in at the polar north. If vector and/or velocity is maintained from the ship's departure state at the previous system, then vector and velocity changes will be necessary.

Given that there's the 100D issue, it's not possible to jump "across" the 100D sphere and precipitate on the opposite side, as to appear to be arriving from a system in the other direction, and that travel not perpendicular from the system could potentially be complicated by 100D issues created by moons or other objects as well, it just makes sense to go "north" or "south" from the system.

In addition, this standard establishes a point where "jump buoys", or in the case of Imperial space, X-boat tenders, or other service craft, would station themselves for inbound arrivals. These ships and stations (or buoys in less populous/less important systems) would act as continuous receivers of the nature, location, speed, and vector of all (non military) traffic in the system (by way of transceivers) so that the arriving ship would not have to rely on organic sensors to establish a safe course vector.

In addition, it would also place emergency service craft at a convenient, relatively close location for emergency situations. In more important, highly trafficked, or populous systems, this might even have a asteroid or artificial base close to the standard arrival point.

 

[aramis]

My take on the whole mess:

Much of the time spent maneuvering is to cancel out the relative stellar motion; vector is preserved.

One aims for a specific point. That point is likely to be off by quite some distance, between stellar and planetary motions.

One can read the grid to get a general distance and direction (±30° & ±1Pc) of jump; an exceptional navigator at close ranges might be able to narrow it further. (based upon the ability to read jumps in TNE's RegSB.) Not all ships match vectors with the target system at jump entrance.

Your plot has to be made for a particular ship, place, time and orientation. The more of these that are wrong, the more likely and severe a misjump. Orientation does not correlate to direction of jump.

The 100D limit only applies to entry & exit points; not Star-wars style mass shadows (as they are just too hard to calculate). Your exit point, if it is inside the 100D limit, gets showed directly away from center of object; if in the overlap of more than one, the closest boundary junction.

 

[Drakon]

Noting your correct statement about the vastness of even interplanetary space, there's not much danger of collisions, except around very small destinations with lot of traffic. Like a Class A Starport in a High Pop asteroid belt system.

Bingo. That is why you would need some kind of protocalls. The higher the traffic density, the higher the chance of collision. The way to avoid that is to establish target areas for entry into, and exit from, the local traffic patten.

It does depend on how the jump is terminated, the mechanism involved. If you have a trip mechanism on the drive controls, that senses a gravimetric curvature of overs so many g's. Ships would naturally enter a system in a shell around the central star.

Another factor would be accuracy possible with jump drive termination. How accurate can you jump to a specific location in a system?

So there would be conventions in place and regulations in some systems. Somebody proposed a simple convention of in-system travel being restricted to the planetary plane (+/- some thousands of km) and outbound jumps being made above that plane, and inbound jumps being made below that plane. So the convention is you thrust out to 100D in the planetary plane, then pop up to jump out. Inbound you arrive below the planetary plane and move up to it before thrusting in. That alone should reduce the chance of collision to practically zero even in busy systems. Add to it a radian system for where you're coming from and reduce even that chance to infinitesimally small.

Good plan. I would change it so that outbound jumps would be sent to a spot above or below the plane, depending on which side of the local plane the target star is.[/quote]Not necessarily. There's nothing stopping me from jumping past the destination and appear in some other part of the system than the Deneb line.[/quote]Except any extra fuel required by the M drive to get you where you should be. Also I think local traffic control might not want you in odd or restricted spaces. They will prefer things planned, organized, and predictable.

...and you come out of jump with an object directly ahead and no time to stop. Sure it won't happen often (space is big, and mostly empty, as you noted) but it doesn't sound like a good idea to press your luck.

You run that risk regardless of what your vector is, unless you take steps to prevent that.

Basic things would be known orbital data, and some minimum protocalls concerning entry and exit vectors.

Once a ship exits jumpspace, it first things to do would be to sensor sweep, then contact ATC. Then proceed to expected stellar plane, or normal to the central star's spin axis, or nearest port. There are several ways to do it, depending on tech/law level, starport rating, etc. Again another major factor is scale. Are the arrival and departure zones' distance to the plane far less than the size of the plane? or quite large?

This kind of thing really should be done in detail, by someone, officially, if it hasn't already.

I would use FAA regs as a beginning. Establish different air spaces, at different radii from planet or starport, with different contact requirements and vector limits.