Re: Slingshotting ships with gravity wells in SJ

>sorry i miss-spoke
>I meant the wildspace navigation proficiency
>I have a tendancy to clump spelljamming and navigation together

[scratches head and stares at a chart crudely tacked onto the wall]

Are you sure you're reading this right? The sentence I assume you're
referring to, "avoiding hazards and using planetary motion to improve speed
over long journeys" suggests something completely different to me. I fail to
see the connection here between planetary motion and planetary gravitation,
and the connection between navigation and spelljamming tricks.

The so-called "slingshot maneuver" is a spectacular and dangerous trick to
gain extra speed by dipping into a planet's gravity well, orbiting the
planet for a short time, and then escaping it at just the right point that
it adds momentum to your flight. It was popularized by 2001: A Space
Oddyssey, and Star Trek at certain points. It's not the sort of thing you
want to do on a regular basis. If you miscalculate, and at these speeds that
isn't difficult, you could either be flung far from your destination, or
that extra momentum could hurl you violently to the planet's surface. A few
degrees difference at your ejection point, and you could be removed from
your destination by millions of miles. Not that these wouldn't all be
interesting adventure hooks, but that is beside the point.

Clearly what we have here is a difference of interpretation. Where I see
cutting travel time by taking planetary motion (that is, the progress of
whichever astronomical figure along its ordained celestial path) into
account, you see manipulating planetary gravity to gain speed and cut travel
time. While both have the same effect, and the aforementioned passage could
be interpreted to mean either, I feel obligated to explain my position.

[gesturing at a sketch hastily scribbled on a napkin]
Now, say I'm on a ship at planet A (pointing to a planet at the bottom of
the napkin). My destination is on planet B (which is at the left-hand side
of the napkin). I should try to calculate my path to reach a point ahead of
planet B's current location, since I have no hope of catching a planet if it
has a lead on me...

Now. Assuming I know the relative directions and speeds the two planets are
travelling, I should be able to figure out when and where I can reach an
appropriate destination point ahead of planet B's rotation by a significant
margin, say 12 hours (50 million miles) or so, in case I get sidetracked.

Assuming I don't leave enough time or distance in my calculations, I could
under/overshoot my mark, and get stuck trying to catch (or having to wait
for) my destination planet. (travel time increases by 20%) If I'm just right
with my numbers, charts, and guesswork, the course I've charted pays off, my
traveltime is reduced by 10%, and I meet my planet a day or two ahead of
schedule.

Pretty much, instead of taking a course I'm sure will work, I cut across the
plaent's orbital track and try to predict where it will be when I arrive.

Am I making sense to anybody?


~George Lavalle

"Caelum videre iussit, et erectos ad sidera tollere vultus."

He bid them look at the sky and lift their faces to the stars.

~Ovid.

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