Can ships change their real space vector in Jump?

[whartung]

I seem to recall somewhere that this was mentioned.

We know that a ship maintains its vector when it enters and leaves jump. If it's travelling spinward at 10,000km/s when it enters jump, it will be traveling spinward at 10,000km/s when it exits jump.

But I have it in my little brain that it was mentioned somewhere that ships can still apply and use their M Drives in jump, and thus change the vector that they left the normal space in before they return to normal space.

JTAS 24 makes no mention of it, so that suggest that "no" you can't do this.

But I think I've seen this someplace else. Maybe it's GT thing.

Or, I'm hallucinating again. This is what happens when you sleep with deprived oxygen because of a cat resting on your head at night.

 

[mike wightman]

It's in T5.

you can only alter your "real space" vector while in jump with a reaction engine - chemical rocket, HEPlaR, fusion rocket that sort of thing.

M-drives based on gravitics can't do it.

Movement Vector Can Be Changed
A ship can change its speed and direction while in jump space. Vector change requires non-gravity-based drives or devices; gravity-based drives (due to their need to interact with gravity sources) are generally ineffective.

 

[Condottiere]

Has anyone tried a hamster wheel?

 

[infojunky]

Honestly Jump significantly alters the real space velocity/vector just by its nature. In that the point that you jump from has a different vector than the point that you arrive at.

 

[mike wightman]

Your real space vector on jump entry is preserved when you exit, this is canonical fact.

Relative to what is the issue...

 

[infojunky]

Honestly Jump significantly alters the real space velocity/vector just by its nature. In that the point that you jump from has a different vector than the point that you arrive at.

Your real space vector on jump entry is preserved when you exit, this is canonical fact.

Relative to what is the issue...

See that is the issue.

 

[whulorigan]

Your real space vector on jump entry is preserved when you exit, this is canonical fact.

Relative to what is the issue...

Honestly Jump significantly alters the real space velocity/vector just by its nature. In that the point that you jump from has a different vector than the point that you arrive at.

See that is the issue.

Relative to whatever you chose to measure it to prior to jump.

 

[Grav_Moped]

There's been an implicit (and wrong) assumption that the origin and destination worlds are stationary relative to each other.

It's an almost necessary assumption though, as there isn't really any way to systematically track those motions. One could probably encode it into Travellermap, but it almost certainly wouldn't be worth the effort.

 

[RogerD]

There's been an implicit (and wrong) assumption that the origin and destination worlds are stationary relative to each other.

It's an almost necessary assumption though, as there isn't really any way to systematically track those motions. One could probably encode it into Travellermap, but it almost certainly wouldn't be worth the effort.

I brought this up earlier and it was pointed out that for most relative motions between stars the magnitude of the vector would likely be around one turn’s worth of acceleration in any case. Mostly that isn‘t very significant, so it can usually be ignored.

 

[Condottiere]

I don't know.

The safe answer is it's all a straight line, so you exit in the same direction you fell in the rabbit hole.

What would we call this, Newtonian movement?

In theory, we just recreated the Einsteinian universe, so I think in theory we should be able to behave normally within it.

With the jump bubble, that leaves quite a lot of space for margin.

For the lanthanum grid, I think we're very tightly corsetted in within it, leaving no room for manoeuvre.

 

[mike wightman]

If the magic gravitic reactionless m-drive works by interacting with the gravity of large bodies within the universe when the ship is removed from out universe the bubble lacks the gravitational coupling required for a gravitic m-drive to function.

You can - providing you use a reaction engine.

There is no lanthanum grid unless you are playing MegaTraveller.

Lanthanum is used in the drive coils not the hull grid.

 

[Condottiere]

If you think about it, if the jump line passes within a thousand diameters of a gravity well, the manoeuvre drives can grab hold of it, and ignite off the motors.

 

[mike wightman]

So now an object in jump space can interact with the normal universe?

Unintended consequence strikes again

 

[whartung]

It's an almost necessary assumption though, as there isn't really any way to systematically track those motions.

The game does not track it, but that doesn't mean it's not measurable.

In fact, Jump makes it trivially measurable.

Start in some standard system, (Core, Capital, whatever). Something to be considered baseline.

Then set velocity relative to the star to 0 (this should be easily measured).

Then, jump to another system, and measure your new velocity relative to the star. You now have the delta between the two systems. From there, it's just a matter of survey to plot the vectors of all the systems.

But, yes, while technically there is differences among systems, the impact is typically minor.

However, in the HEPLaR universe, it can be important. Fuel is fuel, and it can take a couple of G turns to null it out.

 

[Grav_Moped]

The game does not track it, but that doesn't mean it's not measurable.

In fact, Jump makes it trivially measurable.

Yes, and that's what I was trying to say. Thanks for the clarification!

Easy to measure and keep track of, in-universe (and essential!) Not tracked in the game system, and doing so gets complicated if you're trying to do it right.

Stars' relative motion is easy, planetary relative motion requires calculating orbits and keeping track of where each planet is in its orbit... but you might want to do that anyhow as part of keeping track of stellar jump occlusion.

And if it's tracked in Travellermap (which would probably be the only place it could be), it only works where its procedurally-generated star system matches the one from canon (wiki or direct source material).

 

[Baroun Tardis]

I seem to recall somewhere that this was mentioned.

We know that a ship maintains its vector when it enters and leaves jump. If it's travelling spinward at 10,000km/s when it enters jump, it will be traveling spinward at 10,000km/s when it exits jump.

But I have it in my little brain that it was mentioned somewhere that ships can still apply and use their M Drives in jump, and thus change the vector that they left the normal space in before they return to normal space.

JTAS 24 makes no mention of it, so that suggest that "no" you can't do this.

But I think I've seen this someplace else. Maybe it's GT thing.

Or, I'm hallucinating again. This is what happens when you sleep with deprived oxygen because of a cat resting on your head at night.

T5 has a conversation on it.

"Yes, but..."

M, Z, and G-drives have no gravity well to push against, so you can't change vector in jump space using them.
Conventional rockets work, so if you have a HEPLAR you can do burns as fuel is available.
T-Drives work in jump space

 

[Condottiere]

Fractional rocket thrust.

 

[atpollard]

It's in T5.

you can only alter your "real space" vector while in jump with a reaction engine - chemical rocket, HEPlaR, fusion rocket that sort of thing.

"Movement Vector Can Be Changed

A ship can change its speed and direction while in jump space. Vector change requires non-gravity-based drives or devices; gravity-based drives (due to their need to interact with gravity sources) are generally ineffective. "

M-drives based on gravitics can't do it.

Just the POSSIBILITY opens up a plethora of questions ...

• What happens if a ship ENTERS Jumpspace at 1000 dTons and exits at 100 dTons? Is there a conservation of "volume momentum" when transitioning between "universes"?
• Isn't jumping towards a planet and accelerating to near C while in Jumpspace an indefensible doomsday weapon ... a 100 dTon planet-killer super-torpedo with 1 week to impact and zero chance to intercept?

... are just the first two that spring to my mind. It seems like a subtle paradigm shift from "Jumpspace" (JTAS 24).

 

[Baroun Tardis]

Just the POSSIBILITY opens up a plethora of questions ...

• What happens if a ship ENTERS Jumpspace at 1000 dTons and exits at 100 dTons? Is there a conservation of "volume momentum" when transitioning between "universes"?

Well, if it's a rocket, the rocket exhaust is in the jump bubble with you, so there's conservation of mass.

But when you exit jump space, it's a really impressive jump flash as the ionized vapor expands

 

[Condottiere]

Probably would depend on edition.

For a jump bubble, any significant shift in volume would likely destabilize the bubble, leading to an immediate crash transition - where you end up, and in what condition, would vary.

For the lanthanum grid, volume loss includes likely loss of part of the grid, which would also cause jumpspace to spit you out, somewhere.