On 19 May 2016 at 6:05, xxxxxx@comcast.net wrote:

> Anyway I still have no real clue on how the jump drive works and so
> far none of the theories presented have helped to clear up my
> questions.

Remember, this is *ficion*. So the "way it works" is what's described
in the rule books. Anything boyend that is stuffg wee make up.

Stuff like the hydrogen jump bubble are attempts to make things more
consistent when what the rules describe doesn't seem to make sense.

According to the rules, the way the drive works is that you make jump
calcs (or use a jump tape). This somehow tells the drive that you are
going from your point of departure to your destination.

There's a special power plant as part of the jump drive. And somehow
this uses huge amounts of L-Hyd to charge the jump capacitors
(according to some rule sets). a lot of handwaving and the jump grid
gets charged and the ship enters jump.

There's a "jump flash" associated with entering jump. According to
some/most rule sets.

A week or so later the ship pops out of jump near where you had set
for the destination. Rules specify how long and how close.

There's a jump flash at exit. again subject to which version of the
rules you use.

There are also rules for misjumping. They depend on how close to the
planet/star you were at departure, purity of fuel and how well
maintained the drive is.

If you misjump there are rules for determining where you arrive. I
think a few rulesets allow for a misjump to take longer than normal.

If your chosen arrival point is inside the 100 diameter limit, the
ship arrives at the 100 diameter limit. Some rules say that if you
cross anything else's 100 diameter limit (jump shadow) along the way
you pop out there instead.

Some rules or other canon material note that going outside the ship
in jump is dangerous. Something about contact with jumpspace. and
that there's some sort of "buubble" around the ship where you *can*
work on the hull with some degree of safety.

They also say that damage to the jump grid can allow jumpspace to get
inside the ship and bad things happen.

That's (as far as I can recall) all we *know* about jumps and
jumpspace.

One major inconsistency is why the jump drive uses so much hydrogen.
If it is converting it to energy, then why can't you use that sort of
power plant to supply energy for other things? If not what is that
hydrogen being used for?

Others involve jump shadow, why the 100 diameter (and 10 diamter)
limits exist, and why they are the size they are. The rules one jump
emergenge (when & where) are vague on a few points as well. Or at
least are open to multiple interpretations.

Then there are questions like "why is jumpspace dangerous?", and "how
does the 'bubble' work?"

I'm one of the folks who suggested the hydrogen being part of the
bubble concept. The idea is that since we *know* that j-space has
different laws of physics and (as I recall) the source on the dangers
of encountering it mentioned some sort of radiation when people,
tools or whatever "crossed the edge of the bubble) then one of the
differences may be in something like (I think) the fine structure
constant).

Basically a small change in that constant (or one of the fundamental
constants anyway) make atomes other than protium (Hydrogen 1 as
opposed to deuterium and tritium) impossible.

So normal matter crossing the bounday would break down into protium
and release various sorts of radiation in the process.

So by having the bubble contain protium (refined fuel) you don't have
any radiation if it leaks over the boundary. You also have an excuse
for all that L-Hyd for jump. Plus some extra "local color" for things
that happen if folks are outside the ship in jump.

I noticed that since planets (at least the non-gas-giant ones) in
Traveller all have the same density (unless you go to one of the
books for generating *lots* of extra details) then the 10 diameter
and 100 diamter bit "makes sense" if it's actually based on the
planet's mass and something that varies as the *third* power of the
distance from the planet.

Turns out that tidal forces (or curvature of spacetime, they're
essenitally the same thing) varies that way. So that gives a way to
calculate jump limits for other things. And a good way to justify
things to players who want more than a "that's just the way it
works".

I'm one of the folks who takes jump calcs as specifying "We want to
go *this* distance in *that* direction". Others are of the opinion
that they are "we want to jump from *this* location to *that* spot
relative to the destination planet".

I have trouble with that "relative to the planet bit, given that said
location isn't fixed.

So by my interpretation you aim for a spot. Call it the "base" exit
point. With said spot being at a particular distance and direction
from where the planet *will be* if you exit jump "on time". With the
location variation being from that spot.

If you exit early, the planet won't be there yet (due to orbital
motion) and if you exit late it'll be past the spot. Likewise the
relative motion of the two stars is a factor.

The other interpretation has the ship's "base" exit point being at a
particular distance and direction from the planet at the time the
ship exits jump, and the variation in location being measured from
there.

So, to summarize, there's "what the rules say" and then there are
*decisions* you as GM have to make about how stuff the rules don't
cover (or are imprecise about) works.

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com