Retained inertia & jump

[locarno24]

After looking over this question. For a House rule I decided that a ship does NOT retain inertia in Jump Space. A ship leaving our universe loses its inertial reference (see Mach's principle) and loses its inertia related to our universe.

It does, while in J-space, get a new inertia frame. So, that when it is dumped back, it is moving in conjunction with the target systems frame of reference motion. EI: that of the system star.

Makes sense. We have a different rule with a similar effect - that before jumping a ship needs to try and be at as close to zero velocity as possible with the local gravity gradients - calculations for accurately distorting local space-time is hard enough without moving relative to it when doing so.

As a result, you come out of jump with null velocity having gone into it with zero velocity.

 

[Prime_Evil]

As a result, you come out of jump with null velocity having gone into it with zero velocity.

I suppose that logically if you have some form of reactionless sublight drive based upon gravitic manipulation, you are going to want to turn it off before you make a jump - otherwise you'll be making the jump from the middle of a region of highly warped spacetime. That doesn't mean that you will have zero velocity relative to your initial reference frame though - you might still be coasting along at an impressive speed (although you won't be able to accelerate or decelerate while the maneuver drive is switched off).

 

[DFW]

As a result, you come out of jump with null velocity having gone into it with zero velocity.

I suppose that logically if you have some form of reactionless sublight drive based upon gravitic manipulation, you are going to want to turn it off before you make a jump - otherwise you'll be making the jump from the middle of a region of highly warped spacetime.

Quite correct.

 

[hdan]

I suppose that logically if you have some form of reactionless sublight drive based upon gravitic manipulation, you are going to want to turn it off before you make a jump - otherwise you'll be making the jump from the middle of a region of highly warped spacetime. That doesn't mean that you will have zero velocity relative to your initial reference frame though - you might still be coasting along at an impressive speed (although you won't be able to accelerate or decelerate while the maneuver drive is switched off).

The problem is, which inertial frame are you moving relative to? The one you just left? Then you may not have a strong enough m-drive to even catch up to (or get out of the way of!) the main world in a reasonable time. The one you just entered? How do your orientation and direction get transformed to match the new frame of reference? Can you set that as part of your jumping parameters? (As in, "I'll arrange things so that when we emerge from jump space, our X km/s velocity is pointing at the main world....)

I've read MWM's treatise on Jump before, but I think I prefer DFW's take for its simplicity. It makes more sense to me in MgT's "jump bubble" explanation - you can't be moving relative to the pocket universe you create, or your jump bubble will distort against the "drag" of Jumpspace. (I subscribe to the theory that jump bubbles are a bit like sails or maybe advanced hulls that permit travel through jumpspace. Different jump numbers are achieved through more elaborate jump bubble field configurations, much like Clipper ships can outrun Caravels, even though they're both using canvas and wood to travel across the same sea.)

 

[Reynard]

Finally found another source describing retention of the normal space vector in jump space. Comfirms what I've read in other older Traveller sources. Also adding in the relative vectors of the start and exit systems are the reason ship's computers need to be so powerful.

"Although jumps are usually entered at low velocities, the speed and direction which a ship held prior to jump is retained when it returns to normal space..... This article was copied or excerpted from the following copyrighted sources and used under license from Far Future Enterprises..."

I found this on wikia.com.

 

[DFW]

Finally found another source describing retention of the normal space vector in jump space. Comfirms what I've read in other older Traveller sources.

Yep, taken from sources in earlier versions.

I just made the rule to make it more accurate scientifically and to cut out a lot of problems MM introduced with his rule.

 

[Rikki Tikki Traveller]

I have always used the idea that a ship MUST emerge at the 100D limit of SOMETHING. If you use that idea, then the ship emerges at zero relative velocity to that object; be it a star, planet, moon or whatever.

At TL12, Deep Space Jumps become possible. In that case, the ship projects its own gravity field which causes the ship to precipitate out of jump space (hush, it's handwavy). The ship then emerges at zero velocity relative to that bubble, which since it actually was the ship, means that inertia is maintained and the ship will have a relative velocity to nearby stars, planets and ships.

I TRIED to avoid the Near-C rock thing, but it came back and bit me again. I fixed that by limiting the size of the Jump Bubble to a sphere encompassing 10,000 D-tons at TL15. That keeps the ships small (ish) and avoids the asteriod sized WMDs.