Velocity limits/effects out of jump??

[samuelvss]

What are the effects of velocity going into jump on velocity coming out of jump?

Here are the logical options:

1. Velocity remains the same. (Delta v of the planets and planning the maneuver most effectively out and back is what makes a Navigator-3 worth the extra 1-1.5 kCr/month!)

2. Velocity is part of the jump equation, such that jump process, (or maneuver within jumpspace?) can set the exitting velocities.

?? 1.5 Velocity remains the same, but within some (??) limits of Delta V.

?? 2.5 Velocity is part of the jump equation, but within some (??) limits of Delta V.

3. The realtive velocity (Delta v) with the closest body on exitting (from which the xitting separation of 100 diameters must be maintained) must be zero on exitting jump.

3.5 The relative velocities (Delta v) with the respective closest bodies on entering and exitting (from which the xitting separation of 100 diameters must be maintained) must be zero on entering/exitting jump.


Ramifications of 1: by maneuvering -at 1 G acceleration- for 1 week prior to jump, without the effects of Delta v (which could, in fact, be additive), the ship could come out of jump at a velocity where it could pass through the entire 100 diameters of a size 8 planet in 2.7 seconds; a type C, maneuvering for 2 weeks could come out of a (less than capacity) jump, preceded by a 2 week burn before jumping, do a close fly-by and exit the 100 diameters again on the other side in about .9 seconds.

Refigure for a 100,000 dton buffered planetoid with a suicide crew, and you have a planet-killer. :toast:

Ramifications of 2, as I figure it, are similar; jump just sets the exitting velocity, rather than

Which option have y'all used (of these, or one I haven't thought of) and what are some of the tactical ramifications?

 

[mike wightman]

The official rule is thet vector into jump is retained in the target system.

Unfortunately the people who came up with this rule ignored the fact that solar systems themselves are moving, so the jump drive must also compensate for this.

 

[kafka47]

Given that jump drive is reving up to the jump point...you could be in a dead stop motion and turn on the jump drives is useful heurstic for the referee. Think of the terror of a planetary defence system when entire fleet jumps in just within 10 diameters 0.001 of a diameter of the main world and start firing from a fixed position and then turning around to jump again by a minor spurt to the acceleration.

But, sure for cinematic and other reasons, the jump is usually viewed as culumination of reaching the 10 diameters point...either at full speed as a getaway or a fraction of the speed for the Steady as she goes.

That is one of the cool things about Traveller - its flexibility. There is no quick jump into light speed...and if there is there is need for high skills in piloting when it comes time to precipiate.

 

[samuelvss]

The vector (relative to the body next to entry and exit for jump) therefore remains constant, so a huge velocity is possible if the pilot intends.

An asteroid with jump-1, and maneuver-1 could be rigged a a suicide sled to in essence be a planet-killer. o:

Captive world throws off reins of colonial master is spectacular fashion.

As to Kafka's terror scenario, the fleet would be none the less scary if doing a boomerang fly-by at 35,000 km/sec, spending a total of .9 seconds entering the 100 diameters, flying-by (with whatever change in vector the planetary gravity can give it in such short time), and exitting on the other side.

We could, by moving fuel about, etc., get some more impressive numbers.

The reaction time for defenders, with a "human-in-the-loop" level of automation, could not be sufficient for effective return fire.


Of course the time required to jump again would be critical, because while it would only take the .9 sec to get back into a position to jump, on a size 8 world the 100 diameter mark is only .05 light-seconds away; the fleet entering at 35,000 km/sec would still take a full 20 seconds to get past 2 light seconds on the far side {working from memory that that is long range....where does long range END?}.

So how long it took to jump again would be critical. I imagine it would just be the way to handle it to say the ship can't jump again until the next turn, and just play out one turn.

I may be betraying my ignorance here; I never did LBB2 combat, always LBB5, and I have neither immediately at hand. Long story, very sad. If I am missing obvious from canon, just put me out of my misery without standing on ceremony!

 

[flykiller]

An asteroid with jump-1, and maneuver-1 could be rigged a a suicide sled to in essence be a planet-killer.

this has been discussed many times for many years, without any definitive resolution other than the rules allow for it. if one wishes to prevent such a thing the best work-around is 1) no government does this, because they cannot defend themselves from a similar retaliatory strike, and 2) no terrorists do this, because then absolutely everyone unites against them and tracks them down and destroys everything associated with them. as for sick weirdos, they usually operate alone, and this is not something easily done alone.

as for a jump-fly-by, could be done, if ytu allows for precision jump navigation and precision jump transit times. mine doesn't. in any case a single pass attack would cause surface damage but would have little effect on planetary defenses - imtu those take time and effort to locate and dig out - so nobody does it.

 

[Patron Zero]

Jump Space EWS

Is this where the theoretical devices referred to as jump detectors come into play ?

Personally I cannot recall if such a technology is canon or not by any of the various incarnations of Traveller rules, if anyone can point to such would be considered more learned than I.

 

[Captain Midnight]

The vector (relative to the body next to entry and exit for jump) therefore remains constant, so a huge velocity is possible if the pilot intends.

The problem I've always had with this is "What if there's no clearly-defined body near your entry or exit point?"

For example, let's say I boost from Earth and start off at my maximum acceleration on a straight-line course for Mars. Once I get to around 800,000 miles from Earth, I'm able to jump without penalty to my rolls; however, what happens if I keep going? Presumably, if I jump to Alpha Centauri, I arrive with "an identical vector" (although nobody has ever explained precisely what that vector is "with respect to", which will become important in just a moment).

What happens if I keep on boosting as hard as I possibly can for Mars, and jump when I am exactly halfway between Earth and Mars? Do I arrive with an "outbound" vector"? Do I arrive with an "inbound" vector? Will the situation change if I jump when I arrive exactly 110 diameters out from Mars? Will it make any difference if I set my jump so that I arrive in the vicinity of a specific planet (although intentionally outside that planet's 100-diameter limit)? Will it make any difference if I arrive far from the location of any planet at all? Can my navigator make any changes in my arrival vector? What if the planets in my departure system are orbiting their star in a clockwise direction while the planets in my destination system are orbiting in the opposite direction? Does the 100-diameter limit from the stars in my departure system and my destination system make any difference?

I have dealt with the issue myself by imposing increasing penalties on navigation, piloting, and engineering rolls depending on relative velocity between both the arrival point and the destination point, and if you're not in the general vicinity of a world, the star serves as your reference. (I allow deep-space jumps, but they're hard to navigate.)

It works like this: If you jump shortly after leaving the 100-diameter limit, your penalties for entering jump are based on your velocity relative to that body. If you choose to arrive with a non-zero velocity, you'll also need to make more difficult navigation and engineering rolls. I assume that relative motions between various stars and their planets get canceled out by the navigator's calculations. The penalties go asymptotic as velocities increase -- nobody's ever managed to successfully jump IMTU at 0.1c, nor have they ever survived attempting to return to normal space at such a high velocity, although some twisted debris has been occasionally found after such attempts.

Crack crews are generally able to make jumps without coming to rest, and they can generally arrive with sufficient velocity that they decelerate all the way in. However, it's not something for less-than-expert navigators, pilots, and engineers to try, and I've been known to throw obstacles at players who got overconfident -- your jump may take longer than anticipated, or you may screw up your arrival point, or the ship might suffer hull flexing and system malfunctions. I'm a big fan of "uncertain" task rolls -- the player makes his roll, and I make the roll too, where he can't see it. If we BOTH succeed, all is well, but if he succeeds and I fail... well, such is the magic that adventures are made of.

 

[mike wightman]

A good navigator will set the jump parameters such that you arrive in system with your vector taking you towards your target, you can then decelerate the whole way until arrival.

 

[mike wightman]

Given that jump drive is reving up to the jump point...you could be in a dead stop motion and turn on the jump drives is useful heurstic for the referee. Think of the terror of a planetary defence system when entire fleet jumps in just within 10 diameters 0.001 of a diameter of the main world and start firing from a fixed position and then turning around to jump again by a minor spurt to the acceleration.

But, sure for cinematic and other reasons, the jump is usually viewed as culumination of reaching the 10 diameters point...either at full speed as a getaway or a fraction of the speed for the Steady as she goes.

That is one of the cool things about Traveller - its flexibility. There is no quick jump into light speed...and if there is there is need for high skills in piloting when it comes time to precipiate.

Difficult to do when the closest you can jump is 100 diameters...

 

[The Oz]

A good navigator will set the jump parameters such that you arrive in system with your vector taking you towards your target, you can then decelerate the whole way until arrival.

To elaborate on this a little more.

IMTU you always kept your normal-space vector (with respect to the planet you were leaving) when you re-entered normal space after a jump.

A good navigator would have the pilot leave the origin planet on such a vector, that, taking into account orbital motion of both worlds, the relative stellar velocities of both systems, and the ship's acceleration capability, the planned arrival point has the ship's vector pointing towards the destination planet and is within the ship's capability to make a zero/zero velocity match with the planet, and allows a certain margin for error, just in case.

This way you accelerate all the way out to jump, and all the way in from jump, which saves a little time.

 

[dean]

Is there not a +/- factor to the number of days a jump takes? Planets and systems move a significant distance in a day, making the 100 diameter rule both a necessary safety factor as well as a plot device...

 

[samuelvss]

this has been discussed many times for many years, without any definitive resolution other than the rules allow for it.

in any case a single pass attack would cause surface damage but would have little effect on planetary defenses -

I think the strategic implications are that, just like MAD and chamical weapons in WWI, some strategies of mutual deterreance work even among enemies, and do continue to do so in the OTU

I think the tactical implications of the fly-by are as follows: like the Doolittle raid on Tokyo (which Did little), there is diplomatic value in counting coup. More importantly, though, it could be used as a recon device. IMTU, BTW, I would say that jump is not precise in its exit, but the flyby would not have to be planned for such. You plan for "small planet, big sky" preprogam your outgoing jump, and hope for the best. As long as your incoming vector doesn't plough you into the planet, you are good. Someone may need to give you a tow on the far end, but...

Many recon missions are, in fact, forlorn hopes.

Again, the original scenario was terror not obliteration. If you could obliterate them, why you wouldn't need to hurry out again!

As for digging them out, I agree. Its always been the pattern.

 

[MR TEK]

I had some thoughts, after reading T20.

First as I recall Cannon has alwals been 168 hrs +/- 10% with planetary movements, that would result in a rather large target sphere.

I would add speculation that safty, traffic, and policing would require some standard conventions.

In a populated systems, there would be specific entry and exit spheres, possibly different for each destination world. There would be VERY still penalties for jumping into the system outside those zones.

There would also be limits on entry vectors, especially relating to relative velocity.

To have a functioning space faring system, and knowing the cannon bias toward calcified thinking, only the most psychotic or brilliantly out of box thinkers would even be able to conceive of breaking these rules on the scale of high-velocity flybys, or planet-killer attacks. even risky high speed approaches would be sio dangerious to risk adverse spacers that no one would try them.

Now T20 discusses that jump plots produces SEVERAL projections that all suggest the same arrival time and location. It then states tghat the navigator tries to pick rthe most efficent plot.

To me this says that ssomething about the transition to and from jump must be the source of the +/- 10%. It also suggests that Nav skill, either through technical prowess or some sort of sympithic connection to jump space mechanics leads to better ability to chose the optimal; plot. In short, a hiogh skilled navigator can minimize the variabilty of the the arrival. They can jump and arrive within a smaller window of time and possably space as well.

In comercial terms, since time is litterally money, the more jumps you can finish in a year, the more jumps you get paid for, higher skill navigators would be paid fort their ability to arrive with the shortest time in jump space and the shortest transit to the desination in normal space.

I have left out the physics of entrance vectors and exit vectors. The science of how those vector releate is the ESSENCE of the navigators job, but knowing those rules is more detail than is important to me.

The navigators JOB will be to enter jumpspace with whatever vector creates the jump transit he wants, and exits with the releitive physical location and vector he wants.

Any navigator that cannot consitantly exit jumpspace pointed in the right direction, at a velosity that allows the ship top safly reach it's desitination and dock withoutt excessive manouvering will likly not be employed a second time, and very well could find himself taking a long spacewalk without a suit.

the possable xit vector sugestions from an earlier post are more complicated, becuse not only do system movements make relitive velosityies differnt moment to moment, but with planets reolving around the star, and planes of rotation not lining up, I would think that the variables would be beyond ANY machines ability to calculate.

Cj Cherryh for examaple used the convention of a north and south perendicular to the plane of rotation of the system. Reguardles of the origin of your jump you arrive at the "north" node, and depart from the south.

In that way there is an consistant incomming trafic lane and an a consistant outgoing lane, and everyones vectors are at least relitivly in the same direction.

In her universve you enter and exit just at near-c which is not a normal traveller convention, but even at lower velosities, the problems of keeping traffic moving without collisions would still be significant, and if ignoring the conventions happened even a few times a week, piracy alone would make commerce impossable.

Just my thoughts, and mayby I have discuonted the importance of the main topic, but these are my .02cr

 

[boomslang]

First as I recall Cannon has alwals been 168 hrs +/- 10% with planetary movements, that would result in a rather large target sphere.

Not always.

Way back in CT High Guard, it is 150 to 175 hours. That would then be 162.5 ± 12.5 hours. The 168 ± 10% thing comes later, in a dead-tree JTAS article from MWM, and becomes canonical thenceforth.

The other point worth considering is that although the duration of a Jump may be variable, it is not specified in the original rules that this need be so random as to be a complete surprise to the starship crew; it is still consistent with the old rules that this variable duration may be known (from calculation) before entering Jump. This would allow reasonable fleet operations, for one thing. And it would let navigators make allowances for entry/exit velocity vectors and planetary relative motions and all that stuff.

 

[flykiller]

... there is diplomatic value in counting coup.

vargr, maybe. can't see anyone else being interested in coup, not when there's meson guns involved.

Many recon missions are, in fact, forlorn hopes.

depending on your sensor rules and depictions, recon can be critical. have to find a way to make it more than a forlorn hope.

In short, a hiogh skilled navigator can minimize the variabilty of the the arrival.

'tshow I do it.

 

[Hal]

What would have been nice is if Marc Miller had actually given the skill "Navigation" a purpose and/or function in the game. Seems ironic that it exists, and that you have to have a navigator for piloting a ship, but that there are no actual rules depicting in game, what the navigator does with the skill and when to roll the dice for it other than as a default sensor skill.

Ultimately? If any object moves according to the laws of physics, then a suitably sufficient database containing all of the data relevant to the items of note - can predict where and when any given object will be. As long as a single reference point is used for all other items/objects, one can have a reasonably capable method for determining the vectors involved for all objects.

As for navigation rules? Since Traveller is depicting its star map on a 2 dimensional plane, one need only use the following for their star maps if they are so inclined:

Direction of travel for the star relative to the top of the map itself (ie artificial north). As an added piece of information, one needs to know what the velocity of the star is - which makes it a second piece of information.

Then, when attempting to compute the navigational aspects of star travel, use the original star's direction of motion and velocity as compared against the target star's direction of motion and velocity. In a way, it is no more difficult to compute than vector movement for a starship using its past location and its current location to determine its future location. You just have to add one more step - the velocity of the target location.

 

[boomslang]

What would have been nice is if Marc Miller had actually given the skill "Navigation" a purpose and/or function in the game. Seems ironic that it exists, and that you have to have a navigator for piloting a ship, but that there are no actual rules depicting in game, what the navigator does with the skill and when to roll the dice for it other than as a default sensor skill.

There are actually some meagre rules for using it in the CT Tarsus Module, which involve plotting a Jump exit point close enough to the destination world that you do not end up wasting time and fuel endurance getting to the starport.

There are also rules in the CT Zhodani Alien Module for using Nav skill as a DM when traveling in uncharted space and trying to promptly ascertain whether or not a nearby (within 6 pscs) star has any gas giant satellites. (Note that the CT Vargr Alien Module simply says detecting GGs is automatic from 2 pscs away; go figure.)

There is also a CT adventure somewhere in canon that uses Nav skill to plot a course through a Trojan asteroid field, but the exact source (Beltstrike, perhaps?) eludes me at the moment...

 

[flykiller]

if anyone likes, some navigation skill effects.

jump takes "about 168 hours". roll 2d6 for the actual time.

02) 153 hours
03) 156
04) 159
05) 162
06) 165
07) 168
08) 171
09) 174
10) 177
11) 180
12) 183

for each level of nav skill, subtract 1 from the roll.

and/or, nav skill determines jump destination precision.

nav 1 - within 1000d of a given star
nav 2 - at 100d of a given star
nav 3 - within 100ls of a given destination world
nav 4 - at 100d of a given destination world

 

[samuelvss]

I like the idea, flykiller, and the first table rocks. I think the second is a bit punitive, though. Think a scout, without Nav 1 is always outside 1000 solar diameters. Ouch!

You can just have it as a precent travel time in excess of 100d of the destination world:

2) -10% (Assumes 100d, but using atmospheric breaking or other tricks)
3) -5%(Assumes 100d, but using atmospheric breaking or other tricks)
4) 0%
5) 5%
6) 10%
7) 15%
8) 20%
9) 25%
10) 30%
11) 40%
12) 50%
13) 75%
14) 100%

DM - Nav, No Nav (i.e. 100 ton ships), +2