The tide is another name for the gravitational gradient (that is, the change of force from one point to the next or the slope of that change).  I use a "slope" of about -3.8407*10^-13 m/s^2 (that is, where dF/dr equals that). You aren't saying the force of 0.01g, as the change with respect to distance at the point where the force is 0.01g will vary depending on the mass.

There are a few theoretical special cases where this kind of rule runs up against the 100D rule directly. The net gravitational force within a uniform shell is zero, so how would traveller jump rules apply? Obviously inside a dyson sphere you are within 100D of the sphere but there is no net gravitational effect. By my system a jump would be allowed from anywhere to anywhere within the shell, but traveller rules it probably wouldn't.

On Sun, Jun 28, 2020 at 12:02 PM <xxxxxx@gmail.com> wrote:
I read one version that used (IIRC) 'tidal forces' dropping below 0.01 G as the boundary. That seemed useful. I'm assuming the galaxy would not impose a notable gravitational pull of over 0.01G... would that be true?

I suppose if the other high-tech drives are extensions of Jump tech and not something new and thus perhaps using different physics, then maybe that 'unified jump boundary equation' could make sense.

I know in our games, nobody will ever get their hands on a black or white globe, matter transporters, disintegrators, or anything more than a normal jump drive (unless it was kinda wanky like the limited Annic Nova drive). We mostly prefer to game in the TL 5-13 range with 9-12 being pretty common. The only annoyance of that is most standard TL-15 designs should not be available.

On Sun, Jun 28, 2020 at 2:38 PM Vareck Bostrom <xxxxxx@gmail.com> wrote:
Though for jump entry, there seems to still be a lot of discussion as to whether the sun constitutes a 100D limit or is not relevant - it is convenient to ignore the sun, but its just another body in space with gravity and mass so I'm not sure why it would be ignored.

Like many things in Traveller, the 100D limit doesn't make a lot of sense and is hard to generalize into a rule. If the Sun counts, why not the galaxy? I think a better approach is that the key factor is the gravitational gradient (derivative with respect to distance) at the point of jump, or perhaps the difference in strength of gravity at the opposite ends of the jump bubble. The point gradient is pretty easy to solve for, and if you presume the safe gradient is the same as Earth's at 100 diameters the Sun's limit comes out to be about 0.59 AU rather than almost 1.

That approach to the rule could probably be extended to require different gradients per level of jump or hop (or basically distance attempted) so that a single equation could apply for all drive types and system mass configurations.

On Sun, Jun 28, 2020 at 2:50 AM <xxxxxx@gmail.com> wrote:


On Sat, Jun 27, 2020 at 11:26 PM Thomas Jones-Low <xxxxxx@gmail.com> wrote:
This is brilliant. 

The other thing to keep in mind is developing the Jump Drive is a difficult challenge. It’s only been done seven times in in the history of Charted Space.

Not counting the Aslan! ;)

 
Based on the outcomes of the misjumps and a few other statements, the process of entering jump space is an unstable, chaotic one. You, the Astrogator and the computer system you are using need to know a number of factors to a high degree accuracy. 

Some number of ships are considered 'destroyed'. What evidence is there, I wonder, of that? If there is no evidence, then are they just 'missing, considered destroyed' or are marked 'destroyed' by virtue of some theory of jump science that doesn't result in verifiable outcomes...?

Maybe there are aspects of jump space still not understood that would explain the losses (and whether they are losses - or hopped in time, space, or to a different reality).

I haven't seen any discussion that would indicate they had forensic evidence for a lot of the lost ships.... it seems more likely not seeing them turn up anywhere means they are considered 'lost/destroyed'.

 

Factors would include the gravitational stress at the point on entrance ( the 100D limit), exit (same as before), the stability of the field generated for entrance, and any known potential masses along the flight path. 

Though for jump entry, there seems to still be a lot of discussion as to whether the sun constitutes a 100D limit or is not relevant - it is convenient to ignore the sun, but its just another body in space with gravity and mass so I'm not sure why it would be ignored.

 

The use of unrefined fuel causes fluctuations in the power output of the BHHR, or in the density of the bubble. Which causes the jump field to fluctuate, and cause the misjumps. Scout and military ships avoid the problem simply by overbuilding the power systems and overcharging the hull grid. 

But not enough to use the capacitors as combat energy storage to power weapons, etc. though under some circumstances, if you have a fancy 'black/white' globe, you might be able to use that power somehow to somehow help ??? in a jump.
 

In some cases the misjumps cause the field to collapse. In others the unstable wormhole leaps off in an unexpected direction through space time. The reason you can’t just repeat the misjump to extend the range of a normal jump is the initial conditions are not known with enough accuracy to safely replicate. And get them a little wrong, and you end up as a spray of quarks at the far end. 

Could also be that inherently SOME of the things you need to know are subject to chaos and thus are not guaranteed to be stable enough to depend upon for to-the-microsecond accuracy or better and that could explain misjumps even when you should be able to have all the data otherwise.
 

This is in fact the reason it’s so difficult to build a jump drive. The basic equations applied show the process won’t work. It’s not stable, and very dangerous. 

I wouldn't say 'won't work' or it can't exist. I'd say the drive is always subject to not being able to have every bit of information at the right moment. Usually, the lack of some small amounts of information might lead to a slightly bumpiness or some time variability. In other cases, some misjump effects could ensue. In the worst case, maybe a ship is lost.

Unrefined fuel, being inherently less predictable than the refined stuff, is one contributing factor. Simple uncertainties of position, velocity, etc. could account for the others or something more in the nature of the tearing holes between universes may cover the chaos side of things and the error bars on some of the measured quantities that are inputs to the jump.
 

There was a discussion earlier about aliens being amazed at the risks humans would take. Jump Drives are a version of that. No one who understands the jump space equations ever wants to fly in a ship, the margin for error is just too small.

And yet, the volume of traffic around for strangely non-essential travel seems to suggest it can't be too bad.


 

On Sat, Jun 27, 2020 at 3:46 PM Jeff Zeitlin <xxxxxx@freelancetraveller.com> wrote:
I don't claim to have The Answer, but here's how I sorta reconciled all the
various aspects and descriptions of the jump drive.

First, there is textev for the following components for the Jump Drive:

1. The Drive itself. This is a big bulky piece of equipment that we know
   for sure has...
2. ...Jump Coils in it. There are also associated with it...
3. ...Zuchai Crystals, and...
4. ...Jump Capacitors.
5. There is also a "Jump grid" embedded in the hull, of which Lanthanum is
   a component. Except in some older Vargr implementations, which use
   Barium instead.

We also know that 'fuel' is used in large quantities. Very large
quantities. This 'fuel' is canonically liquid hydrogen.



OK, here's my take on what happens, step by step:

0. INFORMATION: The Jump Drive's four most important components are [in no
   particular order] (a) a Big Honking Handwavium-based Reactor (BHHR),
   (b) the Zuchai Crystals, (c) the Jump Coils, which in some designs
   surround the Zuchai crystals and in others are surrounded by the
   crystals, and (d) the Jump Capacitors

1. The course is programmed into the computer. This causes some field
   and/or beam generators surrounding the Zuchai crystals to align
   themselves and set prospective power levels, and also sets a sequence of
   changes therein. If there is a jump grid, it also specifies energization
   levels and sequences for the segments of the grid.

2. When the command to jump is given, the BHHR goes into operation at its
   maximum possible rate. This causes energy to be generated.

3. Most of this energy is sent to the Capacitors for storage. The
   capacitors can take in the energy at least as fast as the BHHR can
   generate it. A comparatively small amount is diverted to the field and
   beam generators.

4. The fields and beams interact with the Zuchai crystals as described in
   the General Field Theory of Mumble and Inaudible. This generates a
   spherical field potential - not yet an actual field - around the ship.

5. If there is a jump grid, its various segments are energised per the
   computer instructions. This allows the field potential to be reshaped to
   conform more closely to the ship's surface.

6. The fully-charged capacitors discharge into the Jump Coils. This causes
   the field _potential_ to become an actual field that "opens" a "hole"
   from normal space into the non-space called jump space. The hole almost
   immediately closes, but the ship is now in jump space. The duration and
   exit point of the jump are now committed; the only thing that can change
   them is a failure of the field - which will destroy the ship.

7. The BHHR is 'stepped down' to provide a low level of energy to keep the
   field and beam generators and the jump grid energised, and thus
   maintaining the field. This prevents jump space from interacting with
   the matter of the ship, which is fatal to the matter.

8. At the appointed time, the field, which has been receiving a steady
   input of energy, "pulses" entirely out of the control of the ship. This
   opens the hole back to normal space, and when it closes (again, almost
   immediately), the ship is back in normal space. The field and beam
   generators and the jump grid de-energise, and the field and field
   potential drop to null. Jump is complete.




Articles like my Color of Jumpspace suggest that the statement about
commitment in 6. above may not be entirely accurate, and it says nothing
about whether there is a hydrogen "bubble" within the field and around the
ship (but perhaps that's a 'safety' feature, on the theory that if there's
a field failure, _maybe_ having the hydrogen 'protecting' the ship itself
will give the crew a chance to restore the field before jumpspace interacts
with the hull itself...). Or maybe the jump engineer that explained it to
me dumbed it down a bit too much, and it's oversimplified. Or something.

®Traveller is a registered trademark of
Far Future Enterprises, 1977-2020. Use of
the trademark in this notice and in the
referenced materials is not intended to
infringe or devalue the trademark.

--
Jeff Zeitlin, Editor
Freelance Traveller
    The Electronic Fan-Supported Traveller® Resource
xxxxxx@freelancetraveller.com
http://www.freelancetraveller.com

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