Jump Drive

[Grav_Moped]

Well, being edition specific, space tugging is quite easy with jump bubbles.

As regards to emergency life boats/notification, a fifty tonne cutter can easily add another fifty tonnes of ballast within a jump bubble, and a one shot jump drive to keep costs low.

Ballast? How about a mylar balloon with an embedded lanthanum grid? Whole thing packs down to less than half a ton, even counting the tank of nitrogen gas to inflate it.

If you're using it as a lifeboat, use a nitrogen/oxygen mix instead of straight nitrogen, and add an air recycler. Pack everyone into the cutter until you get to 100D, then inflate the balloon, kick off the Jump, and then everyone can go outside and float around instead of making like canned sardines. Bring everyone back in when you get back to normal space again.

 

[Carlobrand]

Jumpbreaker Missile: These missiles create localized gravitational distortions when they detonate, making the delicate calculations required for an accurate jump much more difficult. A ship hit by a jumpbreaker missile suffers dee em minus eight to any Jump check (see the Traveller Core Rulebook, page one hundred forty eight) attempted in this combat round or the next.

Anything that causes significant distortions in either the local gravitational environment, or volume within a jump bubble.

"This is Kobayashi Maru. We've struck a gravitic mine and have lost power. Our hull is penetrated and we have sustained..."

Every now and then, I feel the need to quote Douglas Adams: “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.”

We're talking some about 100-diameter limits and things precipitating you out of jump but, let's be frank, if you've been precipitated out of jump-space unexpectedly, you have either screwed up in a fairly major way, have had a quite mind-bogglingly improbable stroke of bad luck, or someone went to a great deal of effort, very careful planning, and more than a little luck to precipitate you out. Or they had some really sweet tech for the job.

Jupiter, for example, is huge - not sun-huge, but the next best thing in this system. Its 100-diameter limit is correspondingly huge. Yet, it moves in its orbit at about a third of its diameter per hour - its limit crosses in front of a given star in about 25 days, out of an orbit that takes 12 years to complete. So, about a 0.6% chance that Jupiter will be in your way on any given launch. I'd expect the scouts have done a very thorough study of every system in the sector, and really the only big obstruction is going to be the local sun, everything else is just some combination of waiting, planning, or choosing to exit the local planet's 100-d limit by heading up or down instead of out.

That 100 KdT freighter has a handy transponder that's announcing, "Hi there, I'm a 100 KdT freighter, and - well, that's not entirely accurate, I'm really a transponder affixed to this 100 KdT freighter and - okay, I know, get on with it. Anyway, this is where this freighter is, and if you track my signal you'll have a really good idea of where it will be when you plan to jump - or you can just ring up my captain on the radio and talk it out with him. It's been just wonderful having this conversation. Message repeats: Hi there, I'm a ..." The freighter's 100-d limit extends maybe 12-13 klicks around it, sensors should detect it inside of maybe 150,000 klicks, and if one still manages to stumble into its shadow - well, fire the navigator because that certificate is a forgery. In fact, firing the navigator out the airlock without a vacc suit has a certain karmic quality.

 

[whartung]

We're talking some about 100-diameter limits and things precipitating you out of jump but, let's be frank, if you've been precipitated out of jump-space unexpectedly, you have either screwed up in a fairly major way, have had a quite mind-bogglingly improbable stroke of bad luck, or someone went to a great deal of effort, very careful planning, and more than a little luck to precipitate you out. Or they had some really sweet tech for the job.

That's not the issue.

The issue is whether you can be precipitated out of Jump at all. And the two concepts, whether you can or can't, by anything, through bad luck or bad planning, or even on purpose, are basically irreconcilable.

 

[Condottiere]

1. Precipitation - if you need hundred diameters of ye default planetary body before you can safely transition, I guess that passing through a powerful enough local gravitional well will pull you out; the other alternative to consider is if you can phase through solar and planetary objects while hypering.

2. There are some signs Mongoose is uncomfortable with external rubber condoms in jump bubbles, though that may only be my paranoia.

3. Coming back to the rubber condoms, even when filled with gas, they may not have enough mass to create a significant local gravitic effect, so that you couldn't blow one up to a kilometre, and precipitate a starship out of warp within a hundred kilometres.

4. It could be that a small object, say a spaceship, would only be felt like a bump on the journey, as let's assume precipitation requires a critical mass that would act like a wall.

5. Passing through the upto hundred diameter limit might not be enough to take a starship out of hyperspace, but if you're within ten diameters, it might; you could make it dice roll, with penalties increasing the closer you get to the gravitic well.

 

[aramis]

The T5 answer is problematic:
any object larger than the ship can precipitate it out.
This effect can happen at any point along the straight line course,

This is a good justification for battleships.

 

[Carlobrand]

That's not the issue.

The issue is whether you can be precipitated out of Jump at all. And the two concepts, whether you can or can't, by anything, through bad luck or bad planning, or even on purpose, are basically irreconcilable.

I thought it was basic canon that you were precipitated out on arrival at your destination if you tried to go deeper than that 100-diameter limit to your destination. By extension, if you hit some other 100-diameter limit while in jump space, you should experience the same effect with respect to that limit. I wasn't aware that this was an issue at all, but I still haven't mustered the funds to plunge into T5. (I was sooo hoping with that stimulus check, but other things ate it up, and now the computer's struggling, so that's gonna have to be a priority.)

...This is a good justification for battleships.

How so? I mean, yes, it can do the Star Wars thing of approaching close enough to prevent Princess Leia's ship from entering jump space once the little ship was disabled - or making it jump at a penalty, at any rate - but we're still dealing with combat distances vast enough that a battleship's jump bubble is still a comparatively miniscule thing. I figure a Tigress to have a diameter around 235 meters, so a 100D limit 23.5 Km out from it. If an enemy decides to jump out, with battle ranges in the tens of thousands of kilometers, that's quite a small angle that Tigress would block. Yes, it could ignore the blocking effect of other craft, but their effects are likewise quite tiny. Certainly it's a small plus to not have to worry about that, but I'd think any one of a host of other concerns would take precedence - its tremendous vulnerability to meson fire being a key one.

 

[Grav_Moped]

The tactical concept of "large ship can precipitate a smaller ship out of Jumpspace" is the idea that the larger ship can force an engagement against a fleeing ship after it's Jumped -- with no apparent limit to how far along the smaller ship's Jump path it's traveled. Apparently the underlying principle is that either the endpoints or perhaps the entire normal-space path of the ship in Jump is subject to gravitational precipitation for the entire duration of the Jump.

I'm not sold on that idea; logically, the result would be a misjump by the targeted ship rather than a Jump-0 (as it would have retroactively Jumped from inside the attacking ship's 10D limit).

 

[Grav_Moped]

It's worse than that, though. It actually allows one-bit messages to be sent at ludicrously high effective Jump Numbers.

I laid it out in my post at #10 in this thread:

Basically, it allows you to add (well, subtract) a 1-bit signal onto the normal flow of XBoats such that the message arrives at the destination one day later rather than the normal jump duration.

In normal operation, there are 7 Xboats in transit between the origin and destination (in each direction, for a total of 14), spaced one day apart.

The destination expects one boat per day (give or take normal duration distribution), and a properly maintained ship using refined fuel cannot misjump (LBB2 rules as written). So, a missing XBoat can represent a 1-bit signal.

To send the 1-bit message, have the XBoat Tender at the origin "step on the departure point" of the Xboat that left 6 days prior. One day later (give or take the time variation), a very surprised XBoat pilot will find himself right back where he started. Simultaneously, a very surprised XBoat Tender crew will not have an XBoat coming in. This happens just ONE DAY after the originating Tender "stepped on" the XBoat's departure point.

The signal (the absence of an expected XBoat) traveled 4 parsecs in one day, not seven days.

It's an expensive way to send a single bit, as it costs one day's message traffic and disrupts the schedule across the entire network. And you might want to validate it by repeating it after the next boat (one missing boat might have been a mishap, two in a row might mean there's a big problem at the origin -- so pull one back, let the next go through, pull the third one back, then resume normal operations), so it might take 4 days to get a verified signal. It still took only 4 days to send that message 4 parsecs.

The extreme case is J-6 Xboats, twice per day. This can provide an effective signal speed of Jump-21. The base case (J-4, daily) provides an effective signal speed of Jump-7.

 

[mike wightman]

The law of unintended consequence strikes again.

In CT and now MgT MWM's jump space article clearly states that gravity only affects a jump on entry, likely causing a misjump or worse, and if a precipitating ship is within a 100D limit.

Note this last bit - contrary to the great voice of fanon and the GURPS crowd - a ship is only affected by the 100D limit if it is precipitating. The 100D limit doesn't cause the ship to precipitate, it just affects where the precipitating ship arrives back in our universe.

So yes, the jump line is imaginary since the ship is moving through a higher dimension, and nothing on this line can affect a ship in jump.

Draw a circle, on one side mark a point and label it X, 180 degrees around the circle mark a point and label it Y. Or better yet get a ball and mark two opposite points. Now how do I move from X to Y?
Next, somewhere between X and Y on the circumference of the circle mark a third point and label it Z.

If you are jumping from X to Y via the dimension you can not experience then Z is not in your way...

 

[BackworldTraveller]

The law of unintended consequence strikes again.

In CT and now MgT MWM's jump space article clearly states that gravity only affects a jump on entry, likely causing a misjump or worse, and if a precipitating ship is within a 100D limit.

Note this last bit - contrary to the great voice of fanon and the GURPS crowd - a ship is only affected by the 100D limit if it is precipitating. The 100D limit doesn't cause the ship to precipitate, it just affects where the precipitating ship arrives back in our universe.

So yes, the jump line is imaginary since the ship is moving through a higher dimension, and nothing on this line can affect a ship in jump.

Draw a circle, on one side mark a point and label it X, 180 degrees around the circle mark a point and label it Y. Or better yet get a ball and mark two opposite points. Now how do I move from X to Y?
Next, somewhere between X and Y on the circumference of the circle mark a third point and label it Z.

If you are jumping from X to Y via the dimension you can not experience then Z is not in your way...

This is a circular argument (sic) and these points have been discussed (without agreement) earlier in this thread.

My conclusion is that how it works in the OTU varies (each version uses different types of the virtual particle "Handwavium" in the "physics") and that you can take your pick as a referee which you fancy.

 

[whartung]

I thought it was basic canon that you were precipitated out on arrival at your destination if you tried to go deeper than that 100-diameter limit to your destination. By extension, if you hit some other 100-diameter limit while in jump space, you should experience the same effect with respect to that limit. I wasn't aware that this was an issue at all, but I still haven't mustered the funds to plunge into T5.

In CT and now MgT MWM's jump space article clearly states that gravity only affects a jump on entry, likely causing a misjump or worse, and if a precipitating ship is within a 100D limit.

Note this last bit - contrary to the great voice of fanon and the GURPS crowd - a ship is only affected by the 100D limit if it is precipitating. The 100D limit doesn't cause the ship to precipitate, it just affects where the precipitating ship arrives back in our universe.

This is the dichotomy. The "original" model is that gravity only matters at the start and at the end of Jump, not during. That Jump is extra-dimensional and only at entrance and egress does gravity come in to play.

The alternate model is that there is a Line of Jump, and that gravity can affect it during the entirety of the jump, thus able to precipitate, i.e. yank, ships out of jump at a whim.

This alternate model is canon within GURPs, there's a specific section talking about it in Far Trader. It sounds like it has becone canon in T5.

What's not mentioned, and I have not seen discussed, is the timing of these forced precipitations. I have to think that whether you leave jump via the project course plan, or if you're "yanked out", you have to spend 168 +/- 10% hrs "in jump".

So, if you're in a system, point your ship at the second star on the left, and hit the Jump button, but that 100K dTon freighter just-so-happened to get too close, you'll find yourself back in the origin system, a week later, with no freight in sight, scratching your head and wondering what just happened.

If that's not the case, if you can "leave" jump early, then it completely disrupts the economics of jump, especially in inter-system travel. "We're going to run Jump 2 and hit that system over there, but, "oops", the gas giant got in the way and we precipitated out in a day. Gee, what a shame." A day travel from the inner system to the outer system.

 

[whulorigan]

What's not mentioned, and I have not seen discussed, is the timing of these forced precipitations. I have to think that whether you leave jump via the project course plan, or if you're "yanked out", you have to spend 168 +/- 10% hrs "in jump".

So, if you're in a system, point your ship at the second star on the left, and hit the Jump button, but that 100K dTon freighter just-so-happened to get too close, you'll find yourself back in the origin system, a week later, with no freight in sight, scratching your head and wondering what just happened.

If that's not the case, if you can "leave" jump early, then it completely disrupts the economics of jump, especially in inter-system travel. "We're going to run Jump 2 and hit that system over there, but, "oops", the gas giant got in the way and we precipitated out in a day. Gee, what a shame." A day travel from the inner system to the outer system.

All of the "forced precipitation" events I have seen discussed in rulesets (esp. and specifically T⁵) make explicit that the Jump always lasts for 168 +/- 10% hrs, and that the precipitation occurs at the point where the jump-line intersects the intervening gravity well as of the time of jump-initiation.

 

[creativehum]

All of the "forced precipitation" events I have seen discussed in rulesets (esp. and specifically T⁵) make explicit that the Jump always lasts for 168 +/- 10% hrs, and that the precipitation occurs at the point where the jump-line intersects the intervening gravity well as of the time of jump-initiation.

I'm always looking at this stuff from the point of RPG play. Is it useful for RPG play? Is it fun for RPG play?

I'm seeing a few ways in... but also questions!

With the caveat that different editions of the game, and different articles across forty years of history say different, if not explicitly different things; and that I'm no pro when it comes to understanding how accurate far future sensors are...

• If Ship A is in a battle with Ship B, and ship B plans to Jump, how accurately can Ship A pinpoint Ship B's last location when it jumped in order to interrupt the jump? How accurately can sensors pinpoint and record a slice of empty space?
• Is it an odds game, with the plan for Ship A to float generally within the last known location of Ship B, and hope that it's 100 Dimeters distance cross the Jump Point? Or can ship B guarantee that it can cross it's 100 diameters over the Jump Point?
• Does the distance between Ship B and the Jump Point matter? Two ship battling in space are (relatively). Can a starport in orbit around a planet pinpoint the Jump Point of any ship leaving the system? Or are there distances that are too great to point point. (This matters since any Ship A trying to disrupt Ship B's Jump has a whole week to travel to the Jump point. It can be quite far away when it starts its attempt.)
• Is there a point in terms of distance between Ship A and Ship B that it moves form a gamble to a guarantee? Do the ships have to be within a certain distance for Ship A to get a lock on the Jump Point, and beyond that it becomes a gamble?
• The above question varies by the size of the ship. In a small ship universe, if it is a gamble and not a guarantee, how likely is it a pirate ship will be able to stumble across the Jump Point with its 100D. How likely is it for a capital ship?

Thoughts:
If it is a gamble then the a ship that tries to disrupt a Jump has no idea if it succeed until a week passes. Ship A must sit there waiting to see if it worked. The same is true for Ship B, which is disconnected from Real Space and only learns its fate when it drops out of space 100D from Ship B a week later.

Everything I've read (and I've now skimmed the T5 section on Jumps as well), suggests that Ship B's vector can be independent of the jump-line. So Ship B's vector offers no clues as to helping track the Jump Point. The jump point itself is the only thing that matters. Ship A, then, is left with a last known location in the middle of space an no other clues to work form. Correct?

 

[BackworldTraveller]

I'm always looking at this stuff from the point of RPG play. Is it useful for RPG play? Is it fun for RPG play?

I'm seeing a few ways in... but also questions!

With the caveat that different editions of the game, and different articles across forty years of history say different, if not explicitly different things; and that I'm no pro when it comes to understanding how accurate far future sensors are...

• If Ship A is in a battle with Ship B, and ship B plans to Jump, how accurately can Ship A pinpoint Ship B's last location when it jumped in order to interrupt the jump? How accurately can sensors pinpoint and record a slice of empty space?
• Is it an odds game, with the plan for Ship A to float generally within the last known location of Ship B, and hope that it's 100 Dimeters distance cross the Jump Point? Or can ship B guarantee that it can cross it's 100 diameters over the Jump Point?
• Does the distance between Ship B and the Jump Point matter? Two ship battling in space are (relatively). Can a starport in orbit around a planet pinpoint the Jump Point of any ship leaving the system? Or are there distances that are too great to point point. (This matters since any Ship A trying to disrupt Ship B's Jump has a whole week to travel to the Jump point. It can be quite far away when it starts its attempt.)
• Is there a point in terms of distance between Ship A and Ship B that it moves form a gamble to a guarantee? Do the ships have to be within a certain distance for Ship A to get a lock on the Jump Point, and beyond that it becomes a gamble?
• The above question varies by the size of the ship. In a small ship universe, if it is a gamble and not a guarantee, how likely is it a pirate ship will be able to stumble across the Jump Point with its 100D. How likely is it for a capital ship?

Thoughts:
If it is a gamble then the a ship that tries to disrupt a Jump has no idea if it succeed until a week passes. Ship A must sit there waiting to see if it worked. The same is true for Ship B, which is disconnected from Real Space and only learns its fate when it drops out of space 100D from Ship B a week later.

Everything I've read (and I've now skimmed the T5 section on Jumps as well), suggests that Ship B's vector can be independent of the jump-line. So Ship B's vector offers no clues as to helping track the Jump Point. The jump point itself is the only thing that matters. Ship A, then, is left with a last known location in the middle of space an no other clues to work form. Correct?

Who needs cause and effect? You've no detectable presence at point A but if someone gets to point A within 168ish hours then you go to point A instead of point B.

 

[creativehum]

Who needs cause and effect? You've no detectable presence at point A but if someone gets to point A within 168ish hours then you go to point A instead of point B.

My question is, can a ship get to the Point A? To get to it means knowing where it is. To do that you have to somehow have a fixed location in the middle of space with no other clue but Ship B's last location forty minutes ago or six hours ago or whatever-time-ago Ship B jumped as you travel toward that location.

If you don't know where that point I the middle of space is, you can't get there? Right?

If there is no way to know where Point A, the best a ship that wants to disrupt a jump can do can do is head in the general direction of the Jump Point, float around in space for a week and hope the ship's 100D slips over the Jump Point during that time.

How good are the odds of accidentally bumping across the jump line while floating around in the middle of space? That seems a question worth asking. Because if the odds are terrible then the whole thought experiment about someone purposefully trying to interrupt a jump fall apart.

However, if there is a way to mark another ship's Jump Point, then a bunch of questions for fun RPG play come mind:

One example: If I'm Ship B battling with Ship A, and I want to escape with a Jump, and I know with certainty that Ship A can keep tabs on my jump point once I jump, I know I somehow have to destroy or cripple Ship B before I jump, or scuttle the trip and head back to port for safety and hope to lose Ship A and jump another day.

Another example: The PCs are trying to stop Ship B from jumping out of system. If they know they can pinpoint and accurately travel to Ship B's jump point that leads to a certain set of choices and actions on their part. (They don't need to engage... they only need to silently track Ship B and hope they are not spotted.)

If they know tracking and finding Ship B's jump point is a gamble, then they might decide to engage. And failing that, they might wander around the area of the jump point for a week hoping for the best. If that is the case, what are the odds. Are they stupidly long odds, which would make the plan useless? Of is it rolling a 12 on 2D6, which depending on the circumstances might make the gamble worth it.

Cause and effect matters because cause and effect helps us make choices in RPG play, and choices in RPG are the engine of fun. Getting details on what smart people here think about this stuff might allow interesting naval action choices during RPG play.

 

[Condottiere]

1. Well, if hyperspace only interacts with the Einsteinian universe during entry and exit, what if the exit point is in the middle of a star? The starship doesn't interact with the gravitational field of said star until it exits.

2. Maybe in that instance when the starship exits, and the gravitational field starts taking hold, it bounces back in the direcetion it came from, a hundred diameters?

 

[mike wightman]

1. Well, if hyperspace only interacts with the Einsteinian universe during entry and exit, what if the exit point is in the middle of a star? The starship doesn't interact with the gravitational field of said star until it exits.

Yes it does.
As it begins to precipitate back into our universe it is displaced to the star's 100D limit - it says so in the articles.

2. Maybe in that instance when the starship exits, and the gravitational field starts taking hold, it bounces back in the direction it came from, a hundred diameters?

Good enough for me - ever read about what happens when you try and separate quarks?

 

[whartung]

I'm always looking at this stuff from the point of RPG play. Is it useful for RPG play? Is it fun for RPG play?

I think the best scenario that perhaps represents this case in media is in Empire Strikes Back when Han Solo rushes to the Millennium Falcon straight at the Star Destroyer and "vanishes", with the suggestion that they hit hyperspace and escaped.

In a similar scenario, you have a ship trying to escape, and it makes a jump towards Antares. The ship chasing them sees them go in to jump, and they make Reasonable Assumptions about who they are, where they can go, what their range is, etc. and conclude that they did, indeed, jump to Antares.

A week later, the pursuers arrive in Antares only to find that their prey never showed up.

The captain of the chased ship was Really Clever, and knew of badly charted asteroids in the belt. So, while he did, indeed, plot and execute a jump to Antares, he did so "through" this particular section that he was aware as especially dense. He was hoping to be precipitated out early and to never arrive at Antares. But if someone saw the jump, the power applied, the course selected, etc. etc., it LOOKED like a jump to Antares.

But in this case, the ruse worked, and the captain found his ship and crew in the local asteroid belt a week later.

 

[Condottiere]

My take on jump flash is that the power expanded is measurable, and you divide that by the starship volume, will tell you how many parsecs the starship was prepped for.

What you would need is a flash suppressor.

 

[creativehum]

I think the best scenario that perhaps represents this case in media is in Empire Strikes Back when Han Solo rushes to the Millennium Falcon straight at the Star Destroyer and "vanishes", with the suggestion that they hit hyperspace and escaped.

In a similar scenario, you have a ship trying to escape, and it makes a jump towards Antares. The ship chasing them sees them go in to jump, and they make Reasonable Assumptions about who they are, where they can go, what their range is, etc. and conclude that they did, indeed, jump to Antares.

A week later, the pursuers arrive in Antares only to find that their prey never showed up.

The captain of the chased ship was Really Clever, and knew of badly charted asteroids in the belt. So, while he did, indeed, plot and execute a jump to Antares, he did so "through" this particular section that he was aware as especially dense. He was hoping to be precipitated out early and to never arrive at Antares. But if someone saw the jump, the power applied, the course selected, etc. etc., it LOOKED like a jump to Antares.

But in this case, the ruse worked, and the captain found his ship and crew in the local asteroid belt a week later.

That's a good example.

I'm still curious if there is any way for an enemy starship to block a jump line on purpose, after the ship has jumped, without drifting through space for a week and stumbling over the jump line by dumb luck.