T5 Question about Maneuver Drives

[Supplement Four]

While 1% effectiveness seems like the ship is absolutely crippled, in reality it is far from it.

The way I read it, the 1% efficiency seems to be a clarification and not the intended rule.

Looking at page 43, the three charts at the bottom of the page clearly show that the M-Drive cannot operate beyond certain orbits of the star.

With an M9 IV star, M-Drive do not work past oribt 1!



It is on page 41, bottom right hand side, that there is a note that says, "Technically, maneuver drives, gravitic drives, and lifters operate at about 1% efficiency beyond their limits."

But, for how far out beyond the max limit?

I read this as, "Typically, M-Drives cannot operate past the 1000 D limit of the system's star or massive body, if close, but it is allowable for the ship to operate at 1% efficiency if operating just outside of the limit."

As a Ref, I'd read that as, "An M-Drive will work at 1% efficiency at one orbit farther than the max limit, but cannot operate at all at 2+ orbits farther."

Thus, with the M9 IV star cited above, a ship would have full M-Drive out to orbit 1, then operates at 1% to oribt 2, then cannot operate at all if past oribit 2.





This can lead to some interesting gaming situations.

Take a M0 VI star. 1000 D limit is orbit 4. Long range sensor analysis reports a high probability of rich lanthanum deposits on a moon of a world in orbit 7.

This sounds like a job for micro-Jumps, yes?

 

[esampson]

I found it in one of the T5 PDFs on my drive (well, 3 of them actually)...
"Jump Governors
A Jump Drive produces a Jump approximately equal to
its Jump number in parsecs, and no less than the next lower
Jump number. A Jump-4 drive can achieve up to 4 parsecs,
and more than Jump-3." (p.370)

Which means J1 is 0<D≤1Pc.

To me that seems dangerously twisty. That particular paragraph is talking about drive performance, not what constitutes a jump of a given number. It appears to say that if you have a Jump-4 drive without a governor you don't have to worry that the ship comes out of J-Space in the vicinity of the Oort cloud simply because that is the point exactly 4 parsecs away from your departure, however that flexibility isn't enough to enable you to jump to some place that is only 3 parsecs away.

It also includes the word 'approximately'. If you use any reasonable system of approximation an in system jump is going to approximate to 0.

I don't want it to sound like I'm saying 'I reject your statement' because I don't. It is certainly a piece of evidence. I'm just not really convinced on the weight of that statement alone.

It's most explicit in the GT materials, tho - "An in-system microjump requires the same amount of fuel as a one-parsec interstellar jump." (GTIW p. 170). It's been the standard through all editions that the J# is the upper limit, not the lower.

That actually does weigh a bit more on me than the previous statement, however it is also GURPS Traveller which is somewhat questionable as to canon.

As for the J# being stated as the upper limit, again, I'm pretty sure that in all the cases you are referencing what they are talking about is drive performance (a J5 drive has an upper limit of approximately 5 parsecs, but no lower limit). That doesn't automatically translate to '5 parsecs is the upper limit of a jump 5 (maneuver, not drive), but there is no lower limit to jump 5 (again, the maneuver, not the drive)'

 

[Supplement Four]

It is on page 41, bottom right hand side, that there is a note that says, "Technically, maneuver drives, gravitic drives, and lifters operate at about 1% efficiency beyond their limits."

But, for how far out beyond the max limit?

I read this as, "Typically, M-Drives cannot operate past the 1000 D limit of the system's star or massive body, if close, but it is allowable for the ship to operate at 1% efficiency if operating just outside of the limit."

I've begun readin the Maneuver chapter, and I've found something that backs up my thought here.

Page 363: The practical result is that In-System Drives operate within specific distances of stars and worlds, and are essentially unusable beyond those distances.



So...given the chart on page 43, there are systems where there is just not enough gravity to satisfy the needs of the ship's M-Drive. Only micro-jumps are used.



This can lead to some interesting gaming, too.

Islands in the Stream.

 

[Supplement Four]

I just noticed that T5 is changing an old CT given. In CT, ships used full thrust to mid point, flipped around, and decelerated to the destination point. If you could get close enough for visual range, you can always tell a ship that is on the second half of its journey, closer to its destination than its starting point, as the ship will be moving "backwards" with it's drive leading the direction of the ship's motion.

I always thought that an interesting, Traveller-unique, sight: a ship, it's drive plates a-glow, seemingly moving backwards through space.

T5 suggests different movement options, such as accelerate, coast, then decelerate.

Why would you accelerate, coast, then decelerate when fuel isn't really a factor? The newly imposed Diameter limits on M-Drives. A ship going through a pocket of space where the M-Drives are useless, unable to push off the star's or a planet's gravity well, will accelerate to the pocket, coast through it, then decelerate when it re-enters a D limit on the other side of the pocket.

I've always found giving this kind of character to a system pretty interesting.

 

[Supplement Four]

This sounds like a job for micro-Jumps, yes?

Instead, the answer seems to be NAFAL drives.

 

[aramis]

To me that seems dangerously twisty. That particular paragraph is talking about drive performance, not what constitutes a jump of a given number. It appears to say that if you have a Jump-4 drive without a governor you don't have to worry that the ship comes out of J-Space in the vicinity of the Oort cloud simply because that is the point exactly 4 parsecs away from your departure, however that flexibility isn't enough to enable you to jump to some place that is only 3 parsecs away.

It also includes the word 'approximately'. If you use any reasonable system of approximation an in system jump is going to approximate to 0.

I don't want it to sound like I'm saying 'I reject your statement' because I don't. It is certainly a piece of evidence. I'm just not really convinced on the weight of that statement alone.


That actually does weigh a bit more on me than the previous statement, however it is also GURPS Traveller which is somewhat questionable as to canon.

As for the J# being stated as the upper limit, again, I'm pretty sure that in all the cases you are referencing what they are talking about is drive performance (a J5 drive has an upper limit of approximately 5 parsecs, but no lower limit). That doesn't automatically translate to '5 parsecs is the upper limit of a jump 5 (maneuver, not drive), but there is no lower limit to jump 5 (again, the maneuver, not the drive)'

It's discussing what a "Jump X" is. Elsewhere in the chapter, it says that a drive of J-X can do a Jump of 1 to X.

A microjump is a subset of J1 performance. A drive of J1 or more can do a J1, and hence, a microjump. But in the paragraph on hop drives within the microjump notes, it notes the shortest hop is J9 (so just a hair over 8Pc).

 

[rancke]

I found it in one of the T5 PDFs on my drive (well, 3 of them actually)...
"Jump Governors
A Jump Drive produces a Jump approximately equal to
its Jump number in parsecs, and no less than the next lower
Jump number. A Jump-4 drive can achieve up to 4 parsecs,
and more than Jump-3." (p.370)

Which means J1 is 0<D≤1Pc.

It's most explicit in the GT materials, tho - "An in-system microjump requires the same amount of fuel as a one-parsec interstellar jump." (GTIW p. 170). It's been the standard through all editions that the J# is the upper limit, not the lower.

Somewhere there's a description of how the different jump distances work. There are 36 (or more) different alternate dimensions that are all jumpspaces. A jump-1 drive can get you into the J1 dimension; a J2 drive can get you into the J1 or the J2 dimension; a J6 drive can get you into the J1, J2, J3, J4, J5, and J6 dimensions. Getting into the JX dimension (for X = 1 to 6) costs X*10% of ship volume in fuel and allows you to emerge any distance (including 0) up to X parsecs.

A misjump can get you into the higher jump dimensions at a discount.

I thought it might have been Marc Miller's essay on jump space, but that just mentions that there are multiple jump dimensions. My next thought was SOM, but I can't find my copy. Perhaps you could try that, Wil?


Hans

 

[Supplement Four]

My next thought was SOM, but I can't find my copy. Perhaps you could try that, Wil?

I'm pretty sure it's the SOM.

 

[whulorigan]

Somewhere there's a description of how the different jump distances work. There are 36 (or more) different alternate dimensions that are all jumpspaces. A jump-1 drive can get you into the J1 dimension; a J2 drive can get you into the J1 or the J2 dimension; a J6 drive can get you into the J1, J2, J3, J4, J5, and J6 dimensions. Getting into the JX dimension (for X = 1 to 6) costs X*10% of ship volume in fuel and allows you to emerge any distance (including 0) up to X parsecs.

A misjump can get you into the higher jump dimensions at a discount.

I thought it might have been Marc Miller's essay on jump space, but that just mentions that there are multiple jump dimensions. My next thought was SOM, but I can't find my copy. Perhaps you could try that, Wil?


Hans

I'm pretty sure it's the SOM.

It is definitely SOM (because I remember reading it there).

Specifically, p.10-11 in the Jump Drive section, under the heading "Theory":

DGP Starship Operators Manual, [FONT=arial,helvetica] p.10-11:

[/FONT]. . . Following the Big Bang (some 15 billion years ago) a multitude of dimensions existed - far more than the four which we normally perceive. Within seconds, however, most of these dimensions collapsed into nothingness and were lost. From that point on, we have the familiar three dimensions of space and the one of time. However, the era of modern physics dawned with the realization that more dimensions than the four we know survived the Big Bang. Modern cosmology places the number of existing dimensions at no fewer than 62. The vast majority of these alternate dimensions do not affect our everyday life in any way. Beyond the first four dimensions, many of the others are in force only at the subatomic level, while the remaining three dozen are accessible only via jump drive. The various jumpspace dimensions are described by modern physicists as "levels". Each jumpspace level has its own character, defined by the physical laws which operate there: these laws are known as the level's "weave". A level's weave ranges from very "loose" (easily entered) to very "tight" (difficult to enter). Currently, there are six jumpspace levels which the major associated with an approximate distance traveled in parsecs, and is normally identified by a number. A ship making a three-parsec jump, for example, is travelling through "level three jumpspace" or more simply "jump-3" space. Since the weave of each higher jumpspace level gets tighter, it is more difficult to enter level six jumpspace than to enter level one. To date, only misjumps have entered jumpspace level seven or higher. . . . In order for a starship to be able to travel through jumpspace, the ship's jump drive must first open a portal into the desired jumpspace. . . .

EDIT #1: BTW (as a side note), the above mentioned 62 dimensions were arrived at by adding the 36 jumpspace dimensions to the (then) theoretical model of a 26-dimensional universe in String-Theory (at the time of SOM's publication). Not long after this supplement was published, it was discovered that the 26-dimensional model (through a mathematical transformation) was equivalent to (and could thus be simplified to) a 10-dimensional space-time model. Since that time, various strains of theoretical modelling in Supergravity-theories and Brane-theory have modified these numbers into various models with 9, 10, or 11 dimensions.

So, if you wanted to, you could reduce the 62 dimensional SOM model to 45, 46, or 47 dimensions.

EDIT #2: Also, from T5:

T5: p. 367-368:

Multiple Jump Spaces
Jump Space is a continuous series of alternative spaces, each with a slightly different set of different physical laws. Each of the Jump Spaces is infinite, but smaller (often much smaller) than Real Space. Jump Space is classified by the distance it allows ships to travel. Jump-1 allows a ship to move about a parsec in
about a week. Jump-2 allows a ship to move about two parsecs in about a week. The maximum Jump is Jump-9: nine parsecs in about a week. Yet there is an infinite hierarchy of Jump Spaces, some of which become available to the appropriate technology. These increasingly powerful Jump Spaces carry their own names corresponding to about an order of magnitude greater performance: Hop Space allows travel in tens of parsecs; Skip Space allows travel in hundreds of parsecs; even higher performance is supported by Leap Space, Bound Space, Vault Space, and beyond. But, access to these Spaces requires technology beyond the reach of most technological cultures in Charted Space. Most worlds and sophonts are restricted to Jump Space and Jump Drives, with some few capable of Hop Drives or rudimentary Leap Drives. It is with good reason that the drives beyond Jump are called the Fantastic Drives.

 

[whulorigan]

No, a J2 is any jump of 2 parsecs or less performed by a J2 drive. Fuel cost is 20% of ship's volume. If the J2 drive doesn't have a jump governor, it has to perform J2 jumps even at less than 1 parsec. With a jump governor drives can perform jumps up to its maximum number.

In any case, a 0 meter jump with a J1 drive costs 10% of ship's volume to perform. Unless it has been changed in T5.

BTW, Jump Governors are handled slightly differently in T5 vs. CT, I believe.

IIRC, in CT/HG1, the Jump Governor apportioned fuel usage, so that (for example) a J3 drive could perform three successive Jump-1's (using 10% x Hull-dton fuel each time), or a single Jump-3 (using 30% x Hull-dton fuel). Without the Governor, the fuel used by a J3 drive was always 30% x Hull-dton fuel, regardless of distance jumped (Jump-1, Jump-2, or Jump-3).

CT: High Guard (1979), p.32:

Jump Governor: It is possible to procure a jump governor for ships produced according to Book 2. It allows such a ship to utilize fuel more efficiently; instead of consuming all fuel when performing a jump, regardless of jump number, the ship will consume fuel equal to O.1MJn, where Jn is the actual jump number used, rather than the maximum jump number available. . . . Ships produced according to this book already have the jump governor as part of their drives.

In T5, the Jump Governor modifies how the Jump Drive operates:

T5 Core Rules, p.370:

Jump Governors
A Jump Drive produces a Jump approximately equal to its Jump number in parsecs, and no less than the next lower Jump number. A Jump-4 drive can achieve up to 4 parsecs, and more than Jump-3.

A Jump Governor modifies the operation of a Jump Drive allowing any jump performance equal to or less than the drive’s rating. A Jump-4 drive by itself can only perform Jump-4; equipped with a Jump Governor, it can perform Jump-3, Jump-2, or even Jump-1.

A Jump Governor is integral to a Standard or higher tech level Jump Drive. It follows that any Experimental, Prototype, or Early Jump Drive does not have a Jump Governor.

I cannot find a clear T5 reference as to whether or not Jump fuel is used proportionately by Jump# attempted, or counsumed completely regardless of Jump#. I would go with Jump# attempted, until proven otherwise.

 

[rancke]

I cannot find a clear T5 reference as to whether or not Jump fuel is used proportionately by Jump# attempted, or counsumed completely regardless of Jump#. I would go with Jump# attempted, until proven otherwise.

So are you saying that T5 has changed the rules so that you can't jump less than three parsecs with a jump-4?

If so, that's one more T5 retcon I for one am not going to adopt.

Perhaps this ought to be clarified.


Hans

 

[whulorigan]

So are you saying that T5 has changed the rules so that you can't jump less than three parsecs with a jump-4?

Correct, if you do not have a Jump Governor. All Jump Drives, though, do have a Jump Governor if they are constructed at Standard TL or higher.

So your standard TL-13 or higher J4 Drive has a governor, and does not have this problem. A TL-12 Early-J4 Drive, or a TL-11 Prototype J4 Drive does NOT have a governor, and is restricted as noted above.

But even if you do not have a governor and are restricted in your Jump-Level, you can still manage a Jump of less than the rated number if you aim the ship to intersect a gravity-well in your Jump-calculations and force-precipitate the ship out of J-Space at a shorter distance at the 100dia limit. You just can't make a less-than-rated Jump into Free Space.

Perhaps this ought to be clarified.

Yes. What needs to be clarified is how the Jump-Fuel load is consumed for less-than-max rated jumps for a given J-Drive.


BTW, I added an additional edit to post #49 above.
http://www.travellerrpg.com/CotI/Discuss/showpost.php?p=460002&postcount=49

 

[esampson]

The SOM is definitely shows that in a previous edition of Traveller a ship committing a microjump had to burn enough fuel for a full Jump-1 and there seems to be little evidence that it was ever intended to function differently in any other canon editions of Traveller. Still, if would be nice to have it put into errata to make it all nice and clean so that new players won't have to consult with grognards who have the proof in supplements of previous editions.

Incidentally, the model given in SOM for how Jump works doesn't fully agree with the common interpretations of T⁵. As the model is written it appears that you should be able to make a shorter jump with drives that do not have jump governors without the necessity of forcing a misjump. You will still need to spend all the fuel of the full jump, but you won't be limited. This has even bigger implications for Hop and Skip drives as it would seem to indicate that jumping a distance of 14 parsecs is simple whereas it currently appears to be impossible to intentionally do (as you cannot forcibly misjump at ranges in excess of 9 parsecs).

The disagreement between the model and some of T⁵'s rules though don't seem to be enough to justify arguments that microjumps shouldn't use the fuel of a full 1 parsec Jump, however.

 

[Supplement Four]

The SOM is definitely shows that in a previous edition of Traveller a ship committing a microjump had to burn enough fuel for a full Jump-1 and there seems to be little evidence that it was ever intended to function differently in any other canon editions of Traveller.

Yes, that's my understanding of canon as well.