Where have they jumped to?

[Metropolitan District 268]

A ship jumps ... how does another ship know where it went to?

Well, first of all, since every jump takes the same time regardless of distance, you should get a moment-of-jump doppler effect that enables an observer to calculate the length of the jump by the amount of red-shift.

But is this all that can be achieved (often sufficient to tell you where it's gone ...) or is there any way of ascertaining direction as well? And if there is, does it require more than a single point of observation?

 

[FreeTrav]

Who says there's any Doppler effect at all?

 

[fusor]

I don't think there'd be any doppler effect at all; the ship just disappears in a flash of light (according to canon).

You might however be able to figure out where the ship was going if you were close enough to get an exact fix on what direction the ship was pointing in when it jumped. IIRC a ship has to be facing its destination (well, where it's destination will be taking into account light travel time and relative proper motion of the stars...), so an observer may be able to plot a projected path with likely destinations within range?

That said, I think that's going to be very hard to do in practise.

 

[Metropolitan District 268]

C is a constant therefore there's a doppler effect and a red-shift

It may be moving away from you faster than light, but that doesn't mean its electromagnetic radiation won't reach you, any more than you cease hearing a supersonic aircraft after it's passed overhead (indeed, it's BEFORE it's passed overhead that you don' thear it ... )

 

[far-trader]

I don't think there'd be any doppler effect at all; the ship just disappears in a flash of light (according to canon).

I have to disagree, the "flash of light" (if you buy into it, I don't, or at least only partly so, departure flash I can live with, arrival no) itself implies a doppler shift will be observable. I'm not sure how accurate said info would be but it would certainly be helpful in mounting SAR for misjumped ships, if the event was recorded (and most would be, any system with a Starport or another ship would record it as a matter of public record) and the info was accurate. You'd at least know how far to look. As for which direction, that can be deduced from the positional info, IF you subscribe to the jump masking and jump shadowing canon. Or rather possibilities could be narrowed down, in some cases. For distance, one should be able to easily tell how far a jump was being made (barring a misjump) from the energy output directed into jumping. Knowing the distance one can deduce the likely destinations even without knowing the specific direction in many cases. They'll be wanting to jump to another system unless they know of a deep space refueling point.

You might however be able to figure out where the ship was going if you were close enough to get an exact fix on what direction the ship was pointing in when it jumped. IIRC a ship has to be facing its destination...

I think it's kind of implied but not necessarily true.

 

[whartung]

I never go the impression that Jump accelerated you at all. Rather you ... jumped. Other than maintaining your pre-jump vector when you emerge from Jump, there's been nothing that suggested that it actually affected the direction or path of the Jump.

That said, specifically with the Jump Masking tenets, Jump certainly has a "direction". If it didn't then the Jump masking wouldn't matter, at least for pulling a ship out of Jump. You can argue it might affect being able to come out of Jump space (i.e. you can't come out in a masked area).

As for perhaps measuring the power output at Jump, that may be a fair estimate in terms of distance, as was suggested, but I don't think actual direction can be ascertained.

 

[Starviking]

That said, specifically with the Jump Masking tenets, Jump certainly has a "direction". If it didn't then the Jump masking wouldn't matter, at least for pulling a ship out of Jump. You can argue it might affect being able to come out of Jump space (i.e. you can't come out in a masked area).

As an aside, has Jump Masking been canonised?

 

[mike wightman]

C is a constant therefore there's a doppler effect and a red-shift

It may be moving away from you faster than light, but that doesn't mean its electromagnetic radiation won't reach you, any more than you cease hearing a supersonic aircraft after it's passed overhead (indeed, it's BEFORE it's passed overhead that you don' thear it ... )

Emm, a ship in jump isn't in our universe anymore so none of the em emissions from it are detectable by any means.

When a ship enters jump it opens a hole into jump space that it sort of falls into with no real world acceleration.

So no dopler shift.

However, in answer to your original question, according to the TNE rules a jump flash can be analysed to determine the destination of the jumping ship.

 

[mike wightman]

As an aside, has Jump Masking been canonised?

Yes for GT and yes for T5.

Presonally though I think it should have been dumped a long time ago.

It's an example of an secondary authors personal interpretation of the rules making it into canon because there was no counter argument possible at the time.

Going back to MWM's jump space article there are 3 sentences in the whole article about the exit from jump space.

One of them implies jump masking sort of, the other two refute it's existence.

The GT authors went with the one sentence interpretation and jump masking was born.

IMTU I hold to the paradigm where a ship in jump space is cut off from the normal universe and can only be affected by gravity while entering or leaving.

 

[aramis]

C is a constant therefore there's a doppler effect and a red-shift

It may be moving away from you faster than light, but that doesn't mean its electromagnetic radiation won't reach you, any more than you cease hearing a supersonic aircraft after it's passed overhead (indeed, it's BEFORE it's passed overhead that you don' thear it ... )

There is no doppler shift because the ship never even approaches C.

Jump isn't an acceleration. It's a disappearance from the Physical Universe of XYZT axises and appearance in another with UVWT axises.

As for figuring out the destination of a ship you saw jump, rules are in the Ref's section of the Regency Sourcebook. IIRC, it's formidable navigation if within half an LS or so... as you reverse engineer the plot from the J-space tumble imposed by the sequence of grid charging.

 

[Icosahedron]

A ship jumps ... how does another ship know where it went to?

Well, first of all, since every jump takes the same time regardless of distance, you should get a moment-of-jump doppler effect that enables an observer to calculate the length of the jump by the amount of red-shift.

But is this all that can be achieved (often sufficient to tell you where it's gone ...) or is there any way of ascertaining direction as well? And if there is, does it require more than a single point of observation?

IMO (non-canon), nobody knows where it went. If you ignore the jump-masking c**p, you don't even have to face a particular direction. IMTU there's no flash either. There's two ways to figure where he went:
1. Play a game of Battleships and guess.
2. Hire a PI to extract some clues from his recent activity (or do it yourself).
Both make for a more interesting game than 'roll your Nav skill on 2D6 to figure where he's gone'.

 

[captainjack]

IMO (non-canon), nobody knows where it went. If you ignore the jump-masking c**p, you don't even have to face a particular direction. IMTU there's no flash either. There's two ways to figure where he went:
1. Play a game of Battleships and guess.
2. Hire a PI to extract some clues from his recent activity (or do it yourself).
Both make for a more interesting game than 'roll your Nav skill on 2D6 to figure where he's gone'.

Hmmm. My earlier post disappeared.

well, IMTU, the way it works is that observing the jump can give you direction or distance, never both, and always randomly chosen. I mumble about quantum wave collapses, and how in jumpspace direction and distance are just two states of a hyperparticle, which one has to solve for in the navigation. Blah blah, blah, I know, but as you say, it gives enough traction for actual play beyond a 2d6 roll.

 

[Starviking]

However, in answer to your original question, according to the TNE rules a jump flash can be analysed to determine the destination of the jumping ship.

IIRC the rule requires an MFD (Fire Director) lock for analysis. I can't recall where in TNE the rule is though. Maybe a Challenge Mag?

 

[Starviking]

Yes for GT and yes for T5.

Presonally though I think it should have been dumped a long time ago.

It's an example of an secondary authors personal interpretation of the rules making it into canon because there was no counter argument possible at the time.

IMTU I hold to the paradigm where a ship in jump space is cut off from the normal universe and can only be affected by gravity while entering or leaving.

In full agreement with you. IIRC Jump Drive alignment gets thrown within 100 diameters of a mass - effects Jumpspace entry. Who's to say the same effect doen't deposit ships out of Jumpspace once they near their destination?

 

[BlackBat242]

Normal gravity affects the formation of the "hole" between N-space and J-space... it does not change the shape of J-space.

Thus, normal gravity affects entry into/exit from J-space, but not travel through J-space.

However, there can be some gravitational phenomenon (such as black holes) which distort more than just N-space... but these are rare and very far between.



Also, the size/energy characteristics of a "jump hole", calculated against the mass of the ship, gives a good idea of how far the ship jumped... but nothing about direction... but the detecting ship needs to be pretty darned close to get accurate readings on the "hole".



In my Traveller universe, anyway.

 

[mike wightman]

IIRC the rule requires an MFD (Fire Director) lock for analysis. I can't recall where in TNE the rule is though. Maybe a Challenge Mag?

Regency sourcebook, ref's section.

 

[BytePro]

IMTU - originally, sleuthing was the only way.

Physical ship observations or records could give one a pretty good idea on maximum range (though crew skills could exceed this). Investigating recent activity such as refueling bills, and cargo manifests might further clarify intended destination.

However, the mechanic of having to 'plot a jump' is indicative of having to setup various parameters prior to jump which could, in all likelihood, lead to some observable n-space artifacts.​

So, if a ship was observed in the act or immediately after, then I figure sensitive readings could be used to 'recreate' the potential jump plots. This would be no easy task and be dependent on how detailed and how 'fresh' the residual jump signature was... so a sensor check along with a jump plot check with appropriate difficulty DMs.

 

[Starviking]

Regency sourcebook, ref's section.

Cheers!

 

[boomslang]

However, in answer to your original question, according to the TNE rules a jump flash can be analysed to determine the destination of the jumping ship.

This is presumably because Cherenkov radiation (which is the likely-intended source of the characteristic "blue flash" observed in Jumpspace transitions) is highly directional. Although the "velocity" of Jumping vessels is traditionally described as being "zero" (despite zero velocity in open space being a meaningless concept), there should be some residual inertial, radiation signatures (from the drives' helium exhaust, if nothing else) of mass being displaced from realspace to Jumpspace and vice-versa along a vector observable from realspace.