Aim for the center of the mass and you will be (if I have understood the rules).
Can ships change their real space vector in Jump?
- Thread starter whartung
- Start date
RogerD
SOC-12
I suppose there could be a "absolute zero" or "jump space zero" velocity that all jumps exit you at regardless of your input velocity, or that you have to match that jump space velocity prior to jump (or risk misjump). Game mechanically, you have to work out the "absolute speed" of the various bodies in the system and ships will have to cancel those out before they can do much in the new system.
In this version, your previous vector is not just cancelled out but you get a new vector that perfectly places you in a stable orbit. This feels a little bit too magical to me, personally. The advantage of this version is that the game mechanics are easy/obvious.
I have an easier time imagining that you get the speed of the object you are 100D from, but no lateral motion. That's the "inertialess" version of jump space.
I still prefer (in concept, if not in game mechanics) the official rule that doesn't break conservation of momentum. I'm thinking about writing a program to make the game mechanics of that easier to deal with.
mike wightman
SOC-14 10K
The only way this makes sense to me is that jump space is coupled to our galaxy and thus the two move together.
A ship maneuvering to the 100D jump point in a straight line may end up at zero velocity with regards to the planet they just left, but the ship is still orbiting the star and the star is still moving through the galaxy.
A ship maneuvering to the 100D jump point in a straight line may end up at zero velocity with regards to the planet they just left, but the ship is still orbiting the star and the star is still moving through the galaxy.
You compensate by jumping ahead of the point the planet and all it’s motions will be at and it’s more matching course.
Theoretically jump is impossible, and is defined per need for decentralized orgs for adventuring purposes. Do what your game needs, we are already in the realm of aesthetics and plot tech.
mike wightman
SOC-14 10K
Lol, you still have to be moving at 552km/s otherwise it will go past you at 552km/s
mike wightman
SOC-14 10K
I suppose it comes down to do we want to play science fiction or science fantasy - that is, have an "in universe physics" explanation rather than an "it just does"?
This whole discussion has arisen because MWM thought it would be a neat idea for ships to be able to maneuver in jump space. Trouble is the more you define this imaginary tech the more unintended consequence arise.
I stick with the simplest version of jump - a ship moves to the 100D limit and jumps. One week later it arrives at its destination, regardless of the position of "real universe" objects. If the destination is within 100D of a sizable object then jump precipitation occurs at the object's 100D boundary.
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And for game play simplicity, it has the nominal vector magnitude it entered jump with (but maybe not direction, depending...)
I mean, yeah, you could probably generate and keep track of stellar and planetary motions, but ain't nobody got time for that.
Edit to add: ... unless the scenario calls for it, as in the case of a star system that originated outside the galaxy that's moving at an unusual speed or direction.
What part of my saying jump ahead and accel to match course several times now was not clear?
mike wightman
SOC-14 10K
"You compensate by jumping ahead of the point the planet and all it’s motions will be at and it’s more matching course."
Even if you jump ahead and match course it will still take you 15 hours to do so.
You jump to a point that is 15 hours of 1g acceleration distant and then start accelerating, by the time you achieve 552k/s the galaxy and you are in the same frame.
Even if you jump ahead and match course it will still take you 15 hours to do so.
You jump to a point that is 15 hours of 1g acceleration distant and then start accelerating, by the time you achieve 552k/s the galaxy and you are in the same frame.
Such is the price of emo consistency. Other schema involves even more calc/play pain. Is it worth the setting wrinkles or hard feel? <shrug>
Baroun Tardis
SOC-12
Back of my hand, 15 hours at 1g is around 15 million meters
The 100D limit for a size 8 is around 13 million meters...
(both of those are back of hand, someone might want to check my math)
So it doesn't look like that big an issue. Drop out of jump at 100D 'local spinward' of the destination, and then burn to match V.
Even if you were coming out of jump at rest with respect to the planet, I think you're looking at right around 15 hours at 1 G to head in ,flip, decel, land
That's not the problem.
Sure, you may have moved 15M meters in 15 hours, but now your target (which is going "galactic velocity") has moved 30M.
From a dead stop, chasing after something going 552km/s, it's about 30hr. The problem then, of course, is that you're going 1000km/s, so you need to slow down. Which you would do earlier, further complicating the math, and making the trip even longer.
I was playing around with orbital energy (for something else) and suspect that SOME magic HANDWAVIUM is going to be involved or the conservation of energy as you jump 6 parsecs rim ward or coreward (changing GALACTIC orbit) will make most jumps fatal events as you slam into a planet at hypervelocities (or it hits you) or you are flung off into deep space by the energy imbalance between your total energy (potential and kinetic) and the orbital energy of your new position. I am not sure 30 days fuel is enough to deal with the change in energy/velocity.
What about the change in energy from the center of the universe? Sure the distance change is small, but the MASS is huge. And the change at JUMP is instantaneous.
(I have not done the actual math, nor will I … but based on planetary orbits it could be a BIG issue if one wanted to maintain realistic Conservation of Energy.)
What about the change in energy from the center of the universe? Sure the distance change is small, but the MASS is huge. And the change at JUMP is instantaneous.
(I have not done the actual math, nor will I … but based on planetary orbits it could be a BIG issue if one wanted to maintain realistic Conservation of Energy.)
RogerD
SOC-12
An interesting observation. I've been mainly thinking about conservation of momentum, not energy. By jumping several parsecs you are removing a certain amount of energy from one system and adding it to another, which yes, requires some handwavium. (So did the jump drive).
I guess for me the questions are:
* what is the minimum amount of handwavium needed?
* what are the consequences of that handwavium in fiction terms?
* how easy or hard are the game mechanics?
* do I need to vary from Traveller canon or not?
Baroun Tardis
SOC-12
Depends on where you're jumping in
If you come in 15M meters from where the planet will be when you match velocity, then you should have a 0/0 intercept.
I guess what I'm trying to say is "Yeah, the planet will move 30M. But if my jump point is 15M ahead, then I move 15M and it matches up.... so my entry should be 100D/15M ahead of the planet, and instead of thrusting toward the planet I'm thrusting away from it (in it's orbital path, moving toward where it will be in 15 hours) the whole time to match V at the point the courses intersect"
If you look at it as a number line type thing, with the planet at location 0 when the ship jumps in, and moving to the right two 'notches' per hour, then at hour 15 it'll be at 'notch' 30. 100D is about 14 notches ahead of the planet.
If you jump in at notch 15 and thrust to the right on the line, you should hit a speed of 2 notches per hour when you get to notch 30... right about the time the planet gets there.
Obviously the "perfect" jump is to arrive in "front" of the moving object (i.e. planet) and let its velocity work for (towards) you rather than against (away) from you.
If you always come in "at 0", then the originating jump vector is no matter (you will always accelerate as fast, as long, and away from the planet to get out of the 100D as quickly as you can). Then all of the compensation happens on arrival, with, ideally, arriving in front of the target world.
If the originating vector comes with (as spoke in canon), the problem is the same when arriving, you still need to reconcile the two vectors (yours and the planets), its just more gamey trying to preload you escape vector to make the overall trip more efficient.
If you always come in "at 0", then the originating jump vector is no matter (you will always accelerate as fast, as long, and away from the planet to get out of the 100D as quickly as you can). Then all of the compensation happens on arrival, with, ideally, arriving in front of the target world.
If the originating vector comes with (as spoke in canon), the problem is the same when arriving, you still need to reconcile the two vectors (yours and the planets), its just more gamey trying to preload you escape vector to make the overall trip more efficient.
Krikkitone
SOC-12
I prefer the idea that it dies reset to 0 relative to the masses where you exit. (if jumping into deepspace it would be the nearest stars etc. based on gravitational effects…probably tidal forces) Avoids the jump at 0.9 c super missile.
Another idea is that the relative velocity at entrance to major masses becomes the relative velocity to the major masses at exit…and then (to stop the c-missiles) very high relative velocities 0.001c and up, are dangerous for jump like 100D or less)
As for the energy difference…I think that’s the role of the jump fuel…providing a bunch of extra energy (excess can be “lost to jumpspace”) and somehow can bleed back into normal space as needed.(scattered nearby the entire jumpline?)
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Pay the ferry man his due.
Condottiere
SOC-14 5K
It's why astrogators are paid the big bux.
