Can you accelerate during jump?

[Trent]

This has likely been dealt with so excuse me for asking one that's likely been answered, but can you accelerate during a jump?

"Why would you want to do that since it makes it harder to decel after exiting jump to land?" I hear some ask. Well, suppose I'm an eeevil galactic overlord, and I hear that some people on planet Olbermann have dared disagree with my dogma, so I want to plaster them reeeeeally good.

Now assume my homeworld and Olberman are both earthlink, and therefore ~8,000 miles in diameter, thus have a jump limit of ~800,000 miles. (BTW, I know a lot of you metrics only types are writhing in agony over my use of "miles". That's why I'm and :rofl: as I type this.)

Now if an object, like a ship loaded up with a nice big dirty bomb, comes out of just at 800,000 miles from Olbermann the local defenses have some time to intercept it. The faster it comes out of jump the less time they have to react to and intercept it, so if I want to drop a megabomb on Olbermann I want it to come out of jump as fast as possible.

So if I can have it accelerate during it's week in jump it will be moving pretty damn fast when it comes out, even if it was just one week's worth of acceleration at ~1g.

Likewise if I'm jumping into a system known for pirates, I might want to come out mooooving to make me a harder target for some stinking corsair.

So, can a ship accelerate using it's M drive, reactionless thrusters or whatever while in jump on not?

Likewise you might want to decel while in jump if you were chased by a stinking corsair into jump and had to go all out to avoid it and thus entered jump at a higher speed than you should be moving at when you emerge from your jump at a nice, crowded, high traffic planetary area that frowns on ships coming out of jump like a bat out of hell.

 

[Whipsnade]

Trent,

No.


Regards,
Bill

 

[Spinward Scout]

Isn't your velocity the same when you break out of JumpSpace as it was when you went into Jump? So if you're moving at 6-G when you Jump, you're still moving at 6-G when you break out?

 

[far-trader]

Isn't your velocity the same when you break out of JumpSpace as it was when you went into Jump? So if you're moving at 6-G when you Jump, you're still moving at 6-G when you break out?

Yep (except that 6G is an acceleration which over time is a velocity). So if you spend a week ramping up your acceleration you'll have a huge velocity vector (and you won't even need the MegaBomb, your mc2 will be enough E to do a lot of damage). It's one of the taboo subjects of high flame of olde, the near C rock problem.

Wrinkles in the plan...

...if it worked everyone would be doing it and there'd be lots of star systems reduced to rubble.

...is jump accurate enough to make it work? Not according to Marc Miller because of random time spent in jump and random exit point of 1000km(?) x jump number randomly displaced from your desired exit point.

Others are more well versed in this, it should really be a FAQ (maybe it is somewhere) but that's the basics.

As far as the original question. Nothing you can do can affect your course once you enter jump. No changing your destination, no cutting the trip short, and no changing your vector (velocity and direction) you had when you entered jump.

I think, more or less...

 

[Trent]

Well, I know that your jump exit velocity is your jump entrance velocity normally. I knew that. However does that assume you don't actively try to change your speed while in jump or not?

Also, I know that you can't alter a jump once it's engaged, but altering the speed you exit jump at would not alter the duration of the jump or your exit point, grok?

 

[Peter Schutze]

my understanding has always been that you exit jump at effectively zero velocity in relation to the system you are entering

that seems to be the main point in all the piracy threads anyway because otherwise you might be able to hit them as they are entering or leaving jump but you surely have no hope of matching vectors

as to accelerating while in jump space .... its a seperate buble universe about the size of the ship so the question would be accelerate relative to what ?

 

[CosmicGamer]

what happens if your maneuver drives were operating at half, in this case 3G's, when you enter J-Space and after you enter J-space you
1) Shut the M-drives down?
2) Increase the M-drives to full (6G's)?

 

[robject]

Re original post:

Your entry vector may be anything you like when entering jumpspace.

I am not sure what happens to that vector when inside jumpspace. Quite possibly, additional thrust is randomized in jumpspace.

Your exit vector is random with respect to the system into which you precipitate. So, with enough attempts, you probably could bombard a planet, but we need to calculate how many attempts are likely to result in one success.

 

[Commander Truestar]

My understanding of thrust entering and exiting jump is that they are exactly the same.
That is, IIRC, supported by descrptions(though not explicitly) of jump actions and activities.

IMTU I consider the following facters as reasons why most ships slow to zero delta vee before entering jump:
1) Most planets have jump space emergance and precipitation zones prescribed much like air traffic lanes for aviation. This is done by the Imperial Navy(proportedly for basic safety of commercial operations) and are advertized regularly. Navigators plotting jumps to a system know the respective Space Trafffic controls expect them to enter or emerge from jump in a certain region of local space. Defying that is asking for a SDB/Naval interview and inspection at the least.
So my Entrance and Exit zones are based much on what was used by FASA's Battletech universe. Nadir(Due South of the southern pole of the local sun) and Zenith(Due North of the southern pole o the local sun) space are broken into four cubes of space. these cubes are either for jump precipitation or entrance as below:
The boxes defined by Spinward coordinates are for entering(Zenith) or precipitating
(Nadir) from jump to/from destination Systems Spinward and/or Coreward of the
current system
The boxes defined by Trailing coordinates are for entering(Zenith) or precipitating
(Nadir) from jump to/from destination Systems Trailing and/or Riftward of the
current system

2) In Safety protocals also call for ships to precipitate at Zero Vee because the amount of traffic entering a system is always an unknown to the other arrving vessels. Given the unknown level of danger due to arriving traffic in the same region of space, this is enforced by local and Imperial assets.

Of course, a great deal of scuttlebut is based on the "real reasons" behind these and other Imperial regulations however few want to play the odds they will not find the guns of a fast moving IN Destroyer locked on as they are haled to "stand to for inspection".
Even fewer want to risk their ship and cargo on the ethics of Local government controlled SDB's.

Marc

 

[far-trader]

what happens if your maneuver drives were operating at half, in this case 3G's, when you enter J-Space and after you enter J-space you
1) Shut the M-drives down?
2) Increase the M-drives to full (6G's)?

1) Nothing, until you precipitate from jumpspace at the other end. Then you won't be accelerating but will continue with the vector you had upon entering jump space.

2) Nothing, until you precipitate from jumpspace at the other end. Then you will begin accelerating at 6G adding to the vector you had upon entering jump space.

That said, since maneuver drives do nothing for you during the week in jumpspace they might as well be shut down and the engineers can keep busy doing routine maintenance on them.

 

[far-trader]

Well, I know that your jump exit velocity is your jump entrance velocity normally. I knew that. However does that assume you don't actively try to change your speed while in jump or not?

Also, I know that you can't alter a jump once it's engaged, but altering the speed you exit jump at would not alter the duration of the jump or your exit point, grok?

I grok. The thing is nothing in canon has ever suggested that maneuver drives have any effect once you're in jump space. In fact you're completely cut off from normal space, mostly (1). So your maneuver drives can't change your vector one bit once in jump space.

Of course you could certainly rule otherwise for YTU.

One way I've seen it explained is the jump plot itself is what determines not just where you come out but also your vector in that system. There has to be something to account for relative motion of star systems, and it can be a huge lot of relative motion. More than you'd care to try to counter with maneuver drives in some cases. It also allows you to adjust your arrival vector to what you need for that system. So you can simplify your travel between the jump point and planet.

(1) that whole jump shadow/mask or whatever mess excepted

 

[rancke]

That said, since maneuver drives do nothing for you during the week in jumpspace they might as well be shut down and the engineers can keep busy doing routine maintenance on them.

I wouldn't say the maneuver drive does nothing. Logically it would generate heat. Quite possibly enough heat to overload the subspace heat sinks (I'm joking, of course. Subspace heat sinks wouldn't work in jumpspace ).


Hans

 

[CosmicGamer]

...maneuver drives do nothing for you during the week in jumpspace...

For game purposes, I can live with this but for players who look for scientific accuracy, how do you explain what happens to the force exerted by the maneuver drives?

Next,
What happens if the jump drive goes down once you've entered J-Space?

 

[Whipsnade]

For game purposes, I can live with this but for players who look for scientific accuracy, how do you explain what happens to the force exerted by the maneuver drives?

CG,

The ship is within a bubble which is within another dimension. Ask your players why and how any vector established in that dimension should be transferred to our dimension.

Anyone looking for scientific accuracy with jump drive is just looking for things to grouse about anyway. It's one of the game's "black boxes", you simply need to accept it for what it is.


Regards,
Bill

 

[Commander Truestar]

For game purposes, I can live with this but for players who look for scientific accuracy, how do you explain what happens to the force exerted by the maneuver drives?

Next,
What happens if the jump drive goes down once you've entered J-Space?

heheh
Likely for playability purposes they simply said that when you enter jump space you enter alternate physics. So you are now a ship in a bottle. So now that the ship is in jump space it has nothing to push against with M drives.

So the more scientificly correct question would be, "I know they want to accellerate, but what scientific proof evidence do they have to show that M drives should work as expected in an isolated bubble?".

I see no reason IMO why dumping energy into a closed bubble with nothing to push against should give any result as the physics of jump space are not the same as normal space.

Mind you, that is my opinion. Your's may be different but just because you want yours to be right will not make it so

Marc

 

[Whipsnade]

I see no reason IMO why dumping energy into a closed bubble with nothing to push against should give any result as the physics of jump space are not the same as normal space.

Marc,

Your continued use of the phrase "nothing to push against" shows you've little comprehension of how reactions drives work in reality, so it's no wonder why you're having trouble explaining the non-behavior of the same in Traveller's mythical jump bubbles to your players.

Physics doesn't enter into the question however because we're dealing with make-believe. However, the various parameters and operation of that make-believe has been generally described for over thirty years now. There is nothing in Traveller canon, no article, no adventure, no description, nothing across several version which even hints at the idea that ships can develop useful vectors while in jump space. More importantly, the implications of doing so are canon breakers; i.e. sending near-c rocks through jump space.

Both the lack of hints in canon regarding vector propagation in jump space and the real implications of introducing such a thing to canon are all the arguments that are needed against the suggestion.

Individual GMs may do what they please, there's a recent thread here in which a GM happily describes how his players destroyed an entire planet and it's entire population in order to kill one man. However, as far as the OTU is concerned the operation of maneuver drives in jump space do not effect a vessel's vector in normal space.

That's not my opinion, that's the OTU's opinion.


Regards,
Bill

 

[far-trader]

Next,
What happens if the jump drive goes down once you've entered J-Space?

The ship and all hands are lost. Some refs rule that what happens is the entire thing exits jump space at the appropriate time and place, but as energy only (matter cannot be destroyed).

Same thing imo if the power plant goes down or you run out of fuel. Everybody dies.

The physics of the alternate reality of jump space do not allow normal space matter to exist or function. Jump drives and (post 1st printing of CT) the power plant and fuel that keeps it running are the only thing protecting you from direct exposure to jump space (through whatever mechanics).

In all of canon iirc only 1 individual is reported to have survived (brief and limited I think) exposure to jump space. As I recall it wasn't pleasant. And every other reported case of contact or even close proximity results in death or at the very least severe disability.

 

[rancke]

What happens if the jump drive goes down once you've entered J-Space?

Nothing. The jump drive was used to put you into jump space. Once you're in there, the jump drive is no longer needed; you'll emerge a week later at your destination no matter what happens.

Now, if the power plant goes down and you can no longer maintain the field of normal space that protects your ship while it is in jump space, you die. But the ship still emerges from jumpspace exactly on shedule.


Hans

 

[Icosahedron]

For game purposes, I can live with this but for players who look for scientific accuracy, how do you explain what happens to the force exerted by the maneuver drives?

LOL, you seem to have as many different answers as readers, so here's another option:

Ask any child with washing-up liquid and a loop of wire what happens if you put more and more force into a bubble...

Edit: If you're talking about a 'reactionless' drive; well, you tell me how it works and I'll tell you what happens to the force...

Next,
What happens if the jump drive goes down once you've entered J-Space?

I have a whole raft of different types of misjump to spice up eventualities like this. The xD6 in a random direction thing gets boring after a while. :smirk:

 

[far-trader]

LOL, you seem to have as many different answers as readers...

True. I was a bit surprised by Hans' alternate take on the jump drive necessity once into jump space, but the key is in both cases there is no way to cut a jump short by turning off the jump drive. That would make a mess of the basic presumptive mechanic of 1 week in jump space and the full jump distance covered. Barring misjumps of course, which can be so much fun :devil:

If I didn't want to kill the players and something went amiss once jump was engaged (run out of fuel for the power plant or the jump drive dies or whatever) that's what would happen. Referee fiat misjump.