Jump Space and Conservation of Mass and Energy

[Yenaldlooshi]

JTAS 3 pg12 states "The laws of conservation of mass and energy continue to operate on ships that have jumped; when a ship exits jump space it retains the speed and direction that it had when it jumped."

I think this is a bad thing and that the laws of conservation of mass and energy don't need to apply through Jump Space.

1) It leads to a lot of undesirable in-game possibilities
2) If you consider that given this rule a ship goes into Jump Space with not just the speed relative to the planet it left, but the speed of the orbit the planet was in around its sun, the speed of that sun through its region of the galaxy, the speed of the galaxy and the universe's expansion.... which of all these speeds is conserved and why are the others not?

So I am thinking of making a house rule about this that reads:

"Conservation of mass and energy is NOT maintained through jump. Jump Space has the unexplained effect of zeroing out the speed and direction the vessel had at the point it entered jump space. It emerges from Jump Space with a speed and direction that matches the orbital speed and direction of the nearest planetary body or star and thus zero speed relative to that body or star. It is theorized that this is somehow a default effect of the Astrogation plot itself ie that any such energy from the previous system is 'plotted' into the placement of the arrival point. In this manner, ships jumping from a far outer orbit in one system going to an inner orbit of the next system are not finding themselves flying through the new systems inner orbits so fast they are launched hyperbolically out of the inner system they appeared into.

Due to this Astrogation effect, jumping at a speed greater than zero relative to the nearest planet increases the difficulty to jump by one level (-2) hence why most ships flip and burn down to zero before jumping at 100d"

With this house rule, you can still fire up your jump drive when you are on the run under fire, but we don't have to do crazy modified calculations for how long it takes to close distance from 100D to planetside on the destination because of your built up speed. Also there is incentive to do the flip and burn before leaving which is better for encounters.

Thoughts? Any problems predicted with this? I figure this does not violate physics much more than an actual "jump drive" does in the first place. It solves some problems I see both in realism and in gameplay, else I would not have bothered with it.

 

[MasterGwydion]

JTAS 3 pg12 states "The laws of conservation of mass and energy continue to operate on ships that have jumped; when a ship exits jump space it retains the speed and direction that it had when it jumped."

I think this is a bad thing and that the laws of conservation of mass and energy don't need to apply through Jump Space.

1) It leads to a lot of undesirable in-game possibilities
2) If you consider that given this rule a ship goes into Jump Space with not just the speed relative to the planet it left, but the speed of the orbit the planet was in around its sun, the speed of that sun through its region of the galaxy, the speed of the galaxy and the universe's expansion.... which of all these speeds is conserved and why are the others not?

So I am thinking of making a house rule about this that reads:

"Conservation of mass and energy is NOT maintained through jump. Jump Space has the unexplained effect of zeroing out the speed and direction the vessel had at the point it entered jump space. It emerges from Jump Space with a speed and direction that matches the orbital speed and direction of the nearest planetary body or star and thus zero speed relative to that body or star. It is theorized that this is somehow a default effect of the Astrogation plot itself ie that any such energy from the previous system is 'plotted' into the placement of the arrival point. In this manner, ships jumping from a far outer orbit in one system going to an inner orbit of the next system are not finding themselves flying through the new systems inner orbits so fast they are launched hyperbolically out of the inner system they appeared into.

Due to this Astrogation effect, jumping at a speed greater than zero relative to the nearest planet increases the difficulty to jump by one level (-2) hence why most ships flip and burn down to zero before jumping at 100d"

With this house rule, you can still fire up your jump drive when you are on the run under fire, but we don't have to do crazy modified calculations for how long it takes to close distance from 100D to planetside on the destination because of your built up speed. Also there is incentive to do the flip and burn before leaving which is better for encounters.

Thoughts? Any problems predicted with this? I figure this does not violate physics much more than an actual "jump drive" does in the first place. It solves some problems I see both in realism and in gameplay, else I would not have bothered with it.

I treat is as you exit jump space with the same speed relative to the new body as the speed you had relative to the old body when you entered jump space. Then I don't have to change anything. As for direction? That direction is forward. Unless you happened to be flying backwards when you entered jump space. I treat jump space like travelling through a stargate. You exit it as fast as you enter it, in the direction with which it is oriented. The only difference is that you are in a bubble of real space for a week that it takes to travel that distance.

 

[Terry Mixon]

JTAS 3 pg12 states "The laws of conservation of mass and energy continue to operate on ships that have jumped; when a ship exits jump space it retains the speed and direction that it had when it jumped."

I think this is a bad thing and that the laws of conservation of mass and energy don't need to apply through Jump Space.

1) It leads to a lot of undesirable in-game possibilities
2) If you consider that given this rule a ship goes into Jump Space with not just the speed relative to the planet it left, but the speed of the orbit the planet was in around its sun, the speed of that sun through its region of the galaxy, the speed of the galaxy and the universe's expansion.... which of all these speeds is conserved and why are the others not?

So I am thinking of making a house rule about this that reads:

"Conservation of mass and energy is NOT maintained through jump. Jump Space has the unexplained effect of zeroing out the speed and direction the vessel had at the point it entered jump space. It emerges from Jump Space with a speed and direction that matches the orbital speed and direction of the nearest planetary body or star and thus zero speed relative to that body or star. It is theorized that this is somehow a default effect of the Astrogation plot itself ie that any such energy from the previous system is 'plotted' into the placement of the arrival point. In this manner, ships jumping from a far outer orbit in one system going to an inner orbit of the next system are not finding themselves flying through the new systems inner orbits so fast they are launched hyperbolically out of the inner system they appeared into.

Due to this Astrogation effect, jumping at a speed greater than zero relative to the nearest planet increases the difficulty to jump by one level (-2) hence why most ships flip and burn down to zero before jumping at 100d"

With this house rule, you can still fire up your jump drive when you are on the run under fire, but we don't have to do crazy modified calculations for how long it takes to close distance from 100D to planetside on the destination because of your built up speed. Also there is incentive to do the flip and burn before leaving which is better for encounters.

Thoughts? Any problems predicted with this? I figure this does not violate physics much more than an actual "jump drive" does in the first place. It solves some problems I see both in realism and in gameplay, else I would not have bothered with it.

I like the idea. You could also say that the jump creates a temporary link between the origin and destination such that the momentum is translated the way you said. It’s an unexplained aspect of jump technology and theory.

 

[MasterGwydion]

Personally, had I written the jump rules originally, I would have just said that a ship must be at its lowest point of potential energy, relative to the destination, in order to enter jump space. That is part of the calculation the Astrogator does, figuring out how to achieve a zero velocity with your destination. You need to accelerate in a particular direction and reach a certain velocity before jumping, that way your velocity relative to your destination is zero. Misjumps occur when you screw that little bit up.

 

[Condottiere]

To be fair, we don't actually know what happens in jumpspace.

However, the starship is encapsulated in the rules that govern Einsteinian space.

 

[WHULorigan]

2) If you consider that given this rule a ship goes into Jump Space with not just the speed relative to the planet it left, but the speed of the orbit the planet was in around its sun, the speed of that sun through its region of the galaxy, the speed of the galaxy and the universe's expansion.... which of all these speeds is conserved and why are the others not?

ANSWER: It IS conserved relative to all of them. Speed (or more properly velocity as long as our mass is not changing, because it is momentum that is conserved), is undefined EXCEPT as it is in regard to a specified reference frame/point-of-reference. Then you can compare it to different reference frames.

The other references frames you mentioned above may be of interest academically, but are irrelevant the issue of Jump, any more than I am concerned about my speed relative to galactic expansion or the Earth's rotation or its Revolution about the Sun when I drive to the grocery store. The only reference frame information that matters to me is my position in my own frame, the location of the store relative to my position in my frame, my velocity relative to the store, and the relative velocities of any intervening objects and/or other cars relative to my reference frame as I make my way to the store. All of the other extra-planetary relative velocities of planetary and stellar bodies and galaxies may be interesting, but they have no relevance to the motion of the cars and store, regardless of the actual magnitude of the velocities involved.

The real issue in-game (presuming you wish to include this) is simply to get a feel for a range of real-world believable values for stellar proper motion and planetary orbital velocities at given orbital ranges and use a random roll for the difference between the departure and destination velocities. The values by and large aren't as large as you might think they would be, and with Traveller-style M-Drives with effectively unlimited Delta-V and relatively large continuous accelerations, they can be corrected for in very reasonable amounts of travel time (but occasionally long enough to be a nuisance for some time-sensitive plot reason).

Anything galactic/extra-galactic is likely to far too small on the local level between the two stars to matter for Jump-drive operational ranges.

 

[Geir]

I treat is as you exit jump space with the same speed relative to the new body as the speed you had relative to the old body when you entered jump space. Then I don't have to change anything. As for direction? That direction is forward. Unless you happened to be flying backwards when you entered jump space. I treat jump space like travelling through a stargate. You exit it as fast as you enter it, in the direction with which it is oriented. The only difference is that you are in a bubble of real space for a week that it takes to travel that distance.

You sort of have to, otherwise you deal with all those things that you don't know and the difference in star velocities could be as much as 100kps or more (300 kps is about the worst I'm aware of from Earth, at least within 'jump' range) in any direction.

But by 'forward', I suppose you mean that the outbound velocity from one place becomes the inbound velocity at the new place?
Even that could be tricky, since then you can ask 'relative to what? since it's really still a 3D problem. It would be different if it was a physical gate to jump through, then there really wouldn't be any question.

 

[MasterGwydion]

You sort of have to, otherwise you deal with all those things that you don't know and the difference in star velocities could be as much as 100kps or more (300 kps is about the worst I'm aware of from Earth, at least within 'jump' range) in any direction.

But by 'forward', I suppose you mean that the outbound velocity from one place becomes the inbound velocity at the new place?
Even that could be tricky, since then you can ask 'relative to what? since it's really still a 3D problem. It would be different if it was a physical gate to jump through, then there really wouldn't be any question.

I use the point of arrival as the "jump gate", so it would be relative to that. Who is to say that the point of arrival isn't a physical "gate" that only exists for the micro-second it takes to exit jump space? Not a technological construct, but a "window" or "gate" nonetheless, sized to the jump bubble.

Edit: Technically, I guess, Geir, being a writer, would be the one to say yes or no to that...lolz. As long as he or another writer doesn't though, We get to make it up as We go along...lol...

 

[Sigtrygg]

When Grandfather created the interface between our universe and the jump dimension - previously only accessible to psionic teleportation - the "jump membrane" expanded at lightspeed from the point of its detonation.

The "jump membrane" is coupled to the frame of reference of the movement of our galaxy - everything in out local cluster of galaxies can be considered to be a "stationary" reference point.

Part of jump navigation, the generate program, takes into account the relative motion of the departure system, the ship, and the destination system. You can jump at "zero relative velocity" to the departure system and arrive at "zero relative velocity" to the arrival system, or you can maintain your velocity from your departure system and jump in such a way that that velocity is useful in the arrival system. The referee can decide what the navigator does during all this apart from make coffee, press the button marked generate and carry computer cassettes from storage to the computer.

 

[Geir]

I got interrupted by lunch but that got me time to clarify some thoughts. I have my own strong and somewhat difficult opinions on how jump 'should' work, but as an OTU game premise, we can't work with what I'd call 'facts not in evidence'.

By default, core rulebook, all we know is a planet's Size and nothing else about the system except that there is or isn't a gas giant somewhere. Just because I wrote a whole book on describing the rest of the system and just because Travellermap has enough information on it to determine a bunch of other things doesn't mean you have to use it, and certainly not in a homebrew subsector.

So, based on what you have, including a nice table that tells you how long it takes to get to various distances with turn-around (should really include a '100D' table or add that to the existing table). Given that information and wanting to be consistent with 'how things work' - (plus wanting for game balance reasons not to allow relativistic bombardment ships popping out of jump space and closing the distance to the planet in seconds) - then the best assumption to make for game mechanics is that you exit with zero relative velocity to the 100D mass you emerge next to.

@MasterGwydion's jump gate emulation is a nice compromise, but that would also mean that the 'preferred entry' method for merchants wanting to get to market first would be to hit the point at such velocity that they could slow down just in time to reach the destination world - that would halve the time needed for that inbound transit, but also set up some potentially complicated maneuvers and tradeoff on outbound runs, if the world's were of vastly different size - could be fun for some people, but tedious for most. So zero in and zero out (or zero in regardless of whatever velocity you hit the jump button with) is a good game answer, and the physics of jump space are all made up in any case.

The MTU answer would be much more complicated, but I wouldn't use a lot of things as written if I were running a homebrew campaign.

 

[Terry Mixon]

"Why does jump space work this way?" asked the steward.

"Damned if I know," said the astrogator. "We just have to accept we'll never know how or why. Just be glad it works."

On another note, imagine if the Empress Wave passes and how jump works is different afterward. That would be junky.

 

[Sigtrygg]

Well the hop drive is discovered after it has passed...

 

[Terry Mixon]

Well the hop drive is discovered after it has passed...

There you go!

 

[MasterGwydion]

I got interrupted by lunch but that got me time to clarify some thoughts. I have my own strong and somewhat difficult opinions on how jump 'should' work, but as an OTU game premise, we can't work with what I'd call 'facts not in evidence'.

By default, core rulebook, all we know is a planet's Size and nothing else about the system except that there is or isn't a gas giant somewhere. Just because I wrote a whole book on describing the rest of the system and just because Travellermap has enough information on it to determine a bunch of other things doesn't mean you have to use it, and certainly not in a homebrew subsector.

So, based on what you have, including a nice table that tells you how long it takes to get to various distances with turn-around (should really include a '100D' table or add that to the existing table). Given that information and wanting to be consistent with 'how things work' - (plus wanting for game balance reasons not to allow relativistic bombardment ships popping out of jump space and closing the distance to the planet in seconds) - then the best assumption to make for game mechanics is that you exit with zero relative velocity to the 100D mass you emerge next to.

@MasterGwydion's jump gate emulation is a nice compromise, but that would also mean that the 'preferred entry' method for merchants wanting to get to market first would be to hit the point at such velocity that they could slow down just in time to reach the destination world - that would halve the time needed for that inbound transit, but also set up some potentially complicated maneuvers and tradeoff on outbound runs, if the world's were of vastly different size - could be fun for some people, but tedious for most. So zero in and zero out (or zero in regardless of whatever velocity you hit the jump button with) is a good game answer, and the physics of jump space are all made up in any case.

The MTU answer would be much more complicated, but I wouldn't use a lot of things as written if I were running a homebrew campaign.

Read My answer again. You enter jump space at your lowest possible potential energy relative to your destination, which means you exit jump space with zero momentum. So, it does exactly what you want it to do without having to get all complicated math and such..

 

[Sigtrygg]

Explain what you think "lowest possible potential energy relative to your destination" means.

 

[MasterGwydion]

Explain what you think "lowest possible potential energy relative to your destination" means.

Lowest velocity relative to the nearest body large enough to affect the jump shadow. Zero velocity relative to the destination body at 100D would be the lowest potential energy possible. Any velocity that you have would amount to an increase in potential energy relative to the destination body.

Perhaps I explained it poorly. Sadly, I do that a lot...

Edit: Unless you made a jump drive that allowed you to emerge from Jump Space closer than 100D, in which case, that would be the lower potential energy, still at zero velocity relative to the body.

Gravitational Potential Energy

 

[Sigtrygg]

Lowest velocity relative to the nearest body large enough to affect the jump shadow. Zero velocity relative to the destination body at 100D would be the lowest potential energy possible. Any velocity that you have would amount to an increase in potential energy relative to the destination body.

Velocity is kinetic energy which reduces potential energy, not increase it.

Perhaps I explained it poorly. Sadly, I do that a lot...

Edit: Unless you made a jump drive that allowed you to emerge from Jump Space closer than 100D, in which case, that would be the lower potential energy, still at zero velocity relative to the body.

Gravitational Potential Energy

At 100D with zero velocity you would have maximum potential energy.
As you maneuver towards the planet you gain kinetic and lose potential.
Now here is the fun bit, if you maneuver away from the 100D limit you are gaining potential energy and kinetic energy.

 

[MasterGwydion]

Velocity is kinetic energy which reduces potential energy, not increase it.

At 100D with zero velocity you would have maximum potential energy.
As you maneuver towards the planet you gain kinetic and lose potential.
Now here is the fun bit, if you maneuver away from the 100D limit you are gaining potential energy and kinetic energy.

This is what happens when I am away from college for decades not using My education...

 

[Condottiere]

You can always come to a dead stop in relation to the expanding universe, as you fall down the rabbit hole.

Which means you exit at a dead stop in relation to the expanding universe, as you fall out of the rabbit hole.

 

[WHULorigan]

Well the hop drive is discovered after it has passed...

Perhaps it changed Jump/Hop from Base-6 (Jn^1=1-6pc/ Hn^2=6-36pc) to Base 9 (Jn^1=1-9pc/ Hn^2=10-90pc) and added the higher-order Hyperspatial domains.