Time in Jump

[JustinInOz]

G'Day,

I have done a search on jump timing and jump duration. I did not really find what I was after.

From what I understand a jump takes 151 to 184 hours (168, +- 10%) under normal circumstances. Jumpspace being what it is in Traveller, this variation is not predictable.

How does it work, can fleets all jump together and does this mean that they all precipitate out of jumpspace at the same moment?

I imagine that they do. If they did not, they would probably be destroyed piecemeal as the fleet arrived over the course of 33 hours.


If they do not arrive contemporaneously, do they have to arrive far enough away from the proposed strategic interest (planet, gas giant or base) so that no one can accelerate fast enough to engage them before everyone gets there?

Aside from blatant (and boring) handwavium, how do you justify 100 ships jumping and arriving at the same moment?

Do they all plot the exact same jump run and execute it at the same moment? Why should that mean they arrive together?

Is it not more interesting that they arrive at the same place, but out of phase for time? It always struck me that the jumps were very spatially accurate but unfocussed on the temporal part.

J.

 

[far-trader]

This thread might answer some of your questions...

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=5123

 

[pendragonman]

G'Day,

I have done a search on jump timing and jump duration. I did not really find what I was after.

From what I understand a jump takes 151 to 184 hours (168, +- 10%) under normal circumstances. Jumpspace being what it is in Traveller, this variation is not predictable.

How does it work, can fleets all jump together and does this mean that they all precipitate out of jumpspace at the same moment?

I imagine that they do. If they did not, they would probably be destroyed piecemeal as the fleet arrived over the course of 33 hours.


If they do not arrive contemporaneously, do they have to arrive far enough away from the proposed strategic interest (planet, gas giant or base) so that no one can accelerate fast enough to engage them before everyone gets there?

Aside from blatant (and boring) handwavium, how do you justify 100 ships jumping and arriving at the same moment?

Do they all plot the exact same jump run and execute it at the same moment? Why should that mean they arrive together?

Is it not more interesting that they arrive at the same place, but out of phase for time? It always struck me that the jumps were very spatially accurate but unfocussed on the temporal part.

J.

In MyTU, Fleets moving to assault a system use as a jump "target" the outer edge of said system, often 5-10 AU from the target planet. This distance means that there is significant in system travel to mask during approach to the planet, but the fleet is under very little danger until it unifies out of jump and heads in system.

"Fleets" that would jump much closer to the target, again in MyTU, would be large Battle Rider Tenders. Since the Battle Riders are physically attached to the tender during jump they of course all arrive simultaneously and can begin the assault directly.

I'm unsure as to what canon is on this point however.

 

[Mithras]

That would be my answer also.

 

[rancke]

From what I understand a jump takes 151 to 184 hours (168, +- 10%) under normal circumstances. Jumpspace being what it is in Traveller, this variation is not predictable.

I've been using a bell curve for many years, rolling 8D+140 for the number of hours a jump takes. IIRC, T20 introduced a roll of 6D+147. MT, if you remember, were a little more coarse: You rolled one die and if it was a 1, the jump took 6 days, 2-5 meant 7 days, and a 6 meant 8 days .

How does it work, can fleets all jump together and does this mean that they all precipitate out of jumpspace at the same moment?

There was an answer in the Travellers' Digest's Q&A that addressed this question. IIRC a fleet could spend [a long time] coordinating their jump and having their arrival spread reduced to +/- 1%.

I imagine that they do. If they did not, they would probably be destroyed piecemeal as the fleet arrived over the course of 33 hours.

If they do not arrive contemporaneously, do they have to arrive far enough away from the proposed strategic interest (planet, gas giant or base) so that no one can accelerate fast enough to engage them before everyone gets there?

Exactly.

Aside from blatant (and boring) handwavium, how do you justify 100 ships jumping and arriving at the same moment?

You don't.


Hans

 

[Plankowner]

If you use the idea of each ship arriving separately over 33 hours, that MIGHT justify the Battle Rider concept.

Send in the Battle Rider first to secure the emergence zone, then over the following two days, the other ships arrive...

 

[far-trader]

...Aside from blatant (and boring) handwavium, how do you justify 100 ships jumping and arriving at the same moment?

You don't.


Hans

Hans doesn't

I can.

In MTU the random time and distance factors of jump are not FACTS they are meta-game numbers. They represent in a quick easy abstract way that no two jumps will be the same because jump entry and exit points will vary widely due to the constant movement of the origin and destination systems.

In (the game) reality a jump plot is an extremely precise calculation. It has to be to avoid problems.

"Traveling through hyperspace ain't like dusting crops, boy. Without precise calculations, we'd fly right through a star, or bounce to close to a supernova, and that would end your trip real quick, wouldn't it."

An exaggeration sure, but with a kernel of truth.

So in MTU while each jump is unique, any single plot can serve a large number of ships IF they share the data in real-time and all jump from the same general place to the same general place, at precisely the same time.

This requires one of the ships to serve as the Generate programmer (or all ships to be using the same copy of a pre-calculated jump plot) and all ships have to be in close range and tight communication with the lead ship. All ships are coordinated by the lead ship, requiring it to have a larger computer to handle the data handshaking, under a Fleet Jump program (cpu size varies by fleet size).

Once those requirements are met it's trivial to arrive together.

This doesn't invalidate Battle Riders, they have other advantages (and disadvantages). And it doesn't mean fleets will always time their jumps to arrive together. A good tactic employing the same Fleet Jump mechanics is to stagger your arrivals with calculated arrival points and times known ahead of time.

 

[Plankowner]

Dan, I actually like your idea better than what I have been using. Consider it stolen (urh borrowed).

It also makes a lot more sense when you use the distance variation from JTAS. 3000km if I remember right.

To be that accurate over 6 parsecs means incredible accuracy and the timing would have to be just as critical/accurate to make it work. So precise calculation of distance and time will be necessary, as well as knowledge of all astromomical bodies at the departure and arrival areas. Misjumps happen more due to Navigation error than due to Engine error. Miscalculate the location of that moon and you "bounce" off of it's gravity well and end up a dozen parsecs off course. That works for me!

 

[far-trader]

Dan, I actually like your idea better than what I have been using. Consider it stolen (urh borrowed).

...That works for me!

That's why I threw it out here

Well partly at least, "discussions" are only interesting if there's more than one point being "discussed"

 

[far-trader]

...It also makes a lot more sense when you use the distance variation from JTAS. 3000km if I remember right.

If I recall rightly it's 3,000km per parsec travelled.

 

[Plankowner]

Just to put that into perspective, a parsec is about 3x10^13 km, so that makes the jump calculations accurate to 0.00000001% error, as opposed to time with it's 10% error.

So your jump calculations have GOT to be precise. At that kind of accuracy, missing the orbit of Jupiter by 1% will throw off your calculations for an Earth/Alpha Centauri Jump. Not to mention every other planet and moon, all 4 stars and anything else that might be between them; oh and the gravitational influence of the center of the galaxy and probably Andromeda as well.

 

[G. Kashkanun Anderson]

If I recall rightly it's 3,000km per parsec travelled.

Spot on, although that's the optimal number. Under lesser conditions (lower grade software, non-military equipment, suddenly realizing that your moronic nephew Rodney isn't nearly the navigator your sister claimed he'd be, etc.) the number off can be considerably greater.

 

[boomslang]

From what I understand a jump takes 151 to 184 hours (168, +- 10%) under normal circumstances. Jumpspace being what it is in Traveller, this variation is not predictable.

Actually, under CT HG2 (written before the "Jumpspace" article in dead-tree JTAS and before the SOM), Jump takes 150 to 175 hours, which would be 162.5 ± 12.5 hours (with presumed Normal Probability Distribution, i.e. the Bell Curve, of the results).

As per far-trader, an interesting interpretation/ruling has been raised about plotting fleet movements -- that although this time (for whichever formula you use IYTU) is variable, perhaps it may be reliably predicted when calculating the Jump.

This solution has two very useful results: 1) fleets may Jump together and emerge together in rough formation, and 2) the location of planets and other destination objects at the breakout point may be reliably plotted for and thereby arrived at more or less when and where expected.

Also, if one allows a particular Jump duration to be calculated prior to the actual Jump, this would suggest that Misjump should be detectable by the Misjumping ship, perhaps as soon as entering Jumpspace...

This "pre-figuring" interpretation of the rules about Jump preserves the randomness of Jump travel times which many refs seem quite inordinately fond of, but eliminates a lot of the practical problems which can occur upon breakout if the duration is left as a surprise...

 

[Plankowner]

I like the idea that you would know about a misjump as soon as you entered Jumpspace. Nothing like having up to 6 weeks to worry about where you are going to be (assuming you have 6 weeks of food and water and air).

 

[far-trader]

Just a quick note on my own misjump application of the known quantity of time and place of jump emergence. Minor misjumps won't be known upon entering jump or through jump though you might have some concerns or suspicions based on drive rumblings or spurious data in the plot coming to light after the fact.

Most of the time the first knowledge of a misjump is NOT coming out precisely when (and where) predicted. Two ways usually:

First, before your etp (estimated* time of precipitation), you suddenly feel that familiar tug and pop there you are back in normal space.

Second, the clock counts down to your etp and, and, dang, you don't feel that familiar tug and pop into real space, instead you get that sick feeling as you wonder how long you'll be stuck in jump space and which will run out first, the fuel for the powerplant or the food.

* and by estimated I mean of course calculated to several decimal points

In a more serious misjump scenario you may know as soon as you jump, as rather than that comforting tug as you jump you feel a serious lurch.

 

[Icosahedron]

I think the unpredictability of the jump time was intended to keep the emergence point secret from others, not from your own navigator. I've always used my own Jump Formula

T=cu rt(D+c^2) [SI Units]

Which gives a Jump Time of 5 to 8 days depending on distance travelled. It works for zero-distance 'micro jumps' and is fine up to the Jump-8 limit that HG fuel and drives formulae define as the limit of fusion drive technology.

I then introduce a small random element whose predictability is modified by computer size and navigator skill, and of course cannot be predicted by others.

 

[aramis]

It works for zero-distance 'micro jumps' and is fine up to the Jump-8 limit that HG fuel and drives formulae define as the limit of fusion drive technology.

It only implies J8, as the tables (and supporting rules text) only go to J6.