Before/after jump

[NW_Paul]

Out of curiosity, how do you handle the mechanics before a jump in terms of starship movement?

What I'm getting at here is do you all normally assume a starship maneuvers to their jump point; stops; jumps; and then arrives at the target point stationary?

Would you allow a ship to maneuver to their jump point, and jump without becoming stationary, thereby arriving at the target point in motion?

Assuming the second scenario, would you allow the ship to reappear in normal space 'running dark' to aid in avoiding detection?

 

[SpaceBadger]

I like the idea of any movement vectors relative to the point of jump initiation being retained on coming out of jump, relative to the point of jump exit. That solves a lot of headaches due to figuring in (or just ignoring) relative motions of different star systems to each other; it just doesn't matter, if the transfer of vectors is relative to the entrance/exit points.

 

[whulorigan]

What I'm getting at here is do you all normally assume a starship maneuvers to their jump point; stops; jumps; and then arrives at the target point stationary?

Would you allow a ship to maneuver to their jump point, and jump without becoming stationary, thereby arriving at the target point in motion?

I like the idea of any movement vectors relative to the point of jump initiation being retained on coming out of jump, relative to the point of jump exit. That solves a lot of headaches due to figuring in (or just ignoring) relative motions of different star systems to each other; it just doesn't matter, if the transfer of vectors is relative to the entrance/exit points.

The issue is whether or not you want to hold to conservation of momentum or not. Canon Traveller historically has. So since stars have a proper motion relative to one another, it would be wise to match your momentum vector to the motion of the destination system while still in the originating system, if possible. This would result in a "standing jump", in which you arrive in the destination system stationary relative to your target.

On the other hand, you could do a "running jump", whereby you attempt to maneuver in the originating system prior to jump in such a way that you already have an existing optimal vector for deceleration to your target in the destination system when you arrive.

Of course, you could always rule for YTU that Jump Drive violates the Law of Conservation of Momentum as we understand it today, and say that it gets "accounted for" in the Jump process somehow.

An additional interesting consideration (that I have never heard discussed) is whether or not a ship that is accelerating at the moment of Jump would experience any problems. According to the Equivalency Principle of General Relativity, an accelerated reference frame and a gravitational field are indistinguishable. Does a significant acceleration distort the Jump Field?

 

[Carlobrand]

What they said!

I figure the ship's computer has data on the movements of the various bodies in the various systems. That's what scouts are for, collecting such info. Muy useful, you need to know where the target is so you can plot a course that takes you around the stellar jump shadows to reach it. And, stars move with respect to each other, and planets move around their stars. It's be very unhappy to put yourself at rest with respect to the world you're at and then find yourself a week later closing with the target world at a couple hundred thousand KPH or more.

 

[sabredog]

JTAS#24 has all you need to know.

 

[Fritz_Brown]

I have used the idea that you come to rest relative to your origin system in order to enable the calculations that will put you generally at rest with relation to your target. IMTU, if you jump with motion, you run a very high risk of going boom when you re-enter normal space with too much energy because of the movement differentials. You also have to dissipate the energy of the jump - normally not a big deal if you do the stationary-to-stationary jump, but a problem if you're moving more than a nominal amount.

If you have the capability to run calculations two orders of magnitude more than your normal navigation calcs, then you might be able to avoid going boom. But you better have a *really* good roll.

 

[rancke]

I assume that in "reality" (quotation marks because said reality is fictional) departing ships don't come to a rest relative to the system it is departing but relative to the destination system. However, for gaming purposes coming to a rest with respect to the departure system and nevertheless blithely assuming that the ship is then also at rest relative to the arrival system comes close enough and is much, much simpler.


Hans

 

[Carlobrand]

I have used the idea that you come to rest relative to your origin system in order to enable the calculations that will put you generally at rest with relation to your target. IMTU, if you jump with motion, you run a very high risk of going boom when you re-enter normal space with too much energy because of the movement differentials. You also have to dissipate the energy of the jump - normally not a big deal if you do the stationary-to-stationary jump, but a problem if you're moving more than a nominal amount.

If you have the capability to run calculations two orders of magnitude more than your normal navigation calcs, then you might be able to avoid going boom. But you better have a *really* good roll.

Question: why do you have to be at rest to run calculations? Why not run the calculations hours or days in advance and then plan to be at the precise location at the precise time needed? What is a movement differential? It is rarely possible to be at rest with respect to both origin and destination, given that both are planets orbiting different stars, typically at different orbital distances from stars of different mass. Are you postulating something about the structure of space itself that interacts with the jump field? If so, how does being at rest with respect to a planet orbiting a star orbiting the center of a galaxy that is moving through space? Is there some other factor involved?

 

[BlackBat242]

Not to mention that the stars themselves (and their attendant systems) are moving through space relative to the galactic core and each other.

Within jump distance their vectors are usually virtually identical... but not always.

 

[mike wightman]

And the galaxy itself is hurtling through space at 552 km/s.

 

[whulorigan]

And in all of these points, the most important thing to remember is the question:

"Moving relative to ... what?"

Velocity is undefined relative to space. It is only defined relative to another reference object.

 

[Patron Zero]

And in all of these points, the most important thing to remember is the question:

"Moving relative to ... what?"

Velocity is undefined relative to space. It is only defined relative to another reference object.

Just a shot in the dark but isn't the entire universe itself in some form of motion, generally speaking ?

 

[whulorigan]

Just a shot in the dark but isn't the entire universe itself in some form of motion, generally speaking ?

Objects in the Universe are in motion relative to each other. Velocity is only defined relative to some arbitrarily chosen reference point/object. (This is the fundamental premise of Special & General Relativity (it is what gives rise to the "relativity" part of the name)).

Of course, you could get into fancy Cosmology on the large scale and talk about the expansion of the space-time continuum itself due to "Inflation" or "Dark Energy", but those are large scale cosmological effects.