Most citizens in the Imperium just accept that the Jump Drive works, and in a week they can go Somewhere Else. Well, it’s not that easy. What is a Jump Drive, really? A Jump Drive can project matter “sideways” into alternative dimensions. For convenience, it shoots streams of the same fuel we use for our fusion power: hydrogen. Some fuel is consumed for the high energy requirements of shooting matter “sideways”, but some is the matter itself. The fuel and matter used have to be the same because energy production and the tossing of matter with that energy are in intimate contact and can’t be separated.
Okay, great, so it can
shoot matter into other dimensions. But
what good is that? The Jump Drive is
attached to the ship itself, only the hydrogen goes elsewhere. But by shooting the matter, there is an
impulse or reaction similar to bouncing a perfectly spherical rubber ball on
the pavement. Our ship shoots up, and
lands somewhere else. The hydrogen
shoots opposite, and will eventually make its way back into normal space, but
it also in a perverse way is “carrying” the ship at the same time. Its trajectory matches in some dimensions
with the ship but not others. Also, you'll get only one bounce, not many.
This would be easy to see
if you were an 8-dimensional kid with a ball, but not so easy for us
navigators. We have to envision it more
abstractly, with 8-dimensional matrix algebra, figuring out action and reaction
with 8-dimensional geometric vectors we can’t really see directly. Of course, a computer is helping us calculate
all that in only a few hours…
We get a certain view as we Jump, but our 3-dimensional brains can only really see "pavement", so the Jumpspace looks to us like a swirly, marbled, mother-of-pearl jumble. It hurts our eyes to look at it for too long.
The math gets weird. If the engines are built for it, if they can
convert large masses of fuel at once for more power, you can shoot more fuel,
go further. The bounce seems to fix into
discrete intervals which more or less fit our parsecs, and curiously matches
the general distribution of stars. If
you are the proud owner of a Jump-6 drive, you can program jumps of up to 6
parsecs. Strangely, it doesn’t take 6
times as long as a parsec. We would
think a ball bounced 6 times higher takes longer to go up and fall down
again. But the bounce is more like a
swinging pendulum in this respect.
Galileo looked idly at a swinging chandelier in a chapel and discovered
that, to only small variation, a swing took exactly the same time no matter how
wide the swing. This started modern
time-keeping. So it turns out we are
always talking about a week, give or take.
Of course, things can go
wrong. You want to make a nice, perfectly
spherical “ball” of hydrogen, and the math says it must also be of “even
density” and “smooth”, but I can’t even begin to explain what these
8-dimensional factors mean in real terms.
All your calculations are based on shooting a spherical ball of hydrogen
behind/next to your ship to control where you are going to rejoin normal space.
But what if that ball is
not perfectly “spherical” or “even” or “smooth”? Then, over at universities with nice big
calculus difference-engines, you can calculate the variations, small or large,
in our return points. In practice
on-board we can only do straight navigation and figure out that we veered from
our ideal return spot. If the engine sputtered
or mis-performed, then the misshapen lump of hydrogen could send our ship to a
totally different star or even wreck our ship from sideways torsion. Embarrassing.
Probably even fatal. This is
where you need your engineer to maintain the engines and avoid such
embarrassment. A clean ship is a happy
One extra note: small nicks in the bouncy ball make a ship
veer off in another direction, but a gap of hydrogen in the dead center makes
the ship go in the right direction but fall short of the mark in a combination
of space and time. If the volume of
hydrogen is adjusted to make up for the difference in mass, then the ship will
bounce to the right spot in space but still with a measurable time difference
from the previous predicted time! It
takes much more energy to generate a gap of no hydrogen in a sphere and, as the
hydrogen reasserts itself, a time-displacement results even if the ship has no
net motion. This is more energetic and
finicky, and a fledgling Time Corps is being set up to investigate this
phenomenon. But so far we are at a
primitive stage similar to the earliest days of rocketry. Both launching pads – and astronauts – are blowing
up on us.