Now that the List is back up, here's a post that was lost to the void.
From: John Brewer
Sent: Monday, January 1, 2007 10:11 PM
To: gzg-l@xxxxxxxxxxxxxxxxxxxxxxx
Subject: [GZG] [FT] Scale in the Tuffleyverse
Some of the most frequently asked questions on the List are...
How far can a FTL starship go in one jump?...
How far from a stellar or planetary gravity well must a starship be
to make a jump?...
and How far is a MU?
I've been trying to come up with answers based upon canonical
information, scientific data, and player convenience.
I know from a footnote on page 44 of FB1 that the longest
controlled jump was 7.328 lightyears - slightly over 2 parsecs - so
I surmised that military ships can jump about 2 parsecs. And since
distances on FT maps are listed in parsecs, as are results from
trig equations for star system distances posted by Winchell Chung,
it's convenient to round out performance for Tuffleyverse
jumpdrives in parsecs rather than lightyears.
I made this point in a posting in July of '05 - http://
lists.firedrake.org/gzg/200507/msg00368.html - or if the link
doesn't work, search the author index of July'05 for "John Brewer",
it was my only post that month.
People ask how far a MU is because they have plans for a scenario
involving a battle near a planet, and they want to know how big to
make the planet. A consensus here on the List is that a MU is
about 1000km. The problem with this is that the source for star
system & planetary data for the Tuffleyverse is the "GZG star list
with planetary data" - http://wam.umd.edu/~ddr/ - and the planetary
diameters are measured in MILES.
Now it stands to reason that scenarios with battles near planets is
that the high-value strategic targets will be "garden" worlds with
standard atmospheres. They range in diameters from just under 8000
miles to just over 12000 miles. So for player convenience, I
propose that a MU be a variable between 1700 & 2600 miles,
averaging at 2000 miles.
THAT way, a player can use an inverted 9-inch paper plate to
represent a 4.5 inch "garden" planet and its optimum orbit
distance. The base of the starship would track along the edge of
the plate while in orbit, for ease of measuring. But since an
orbit velocity of 4.5 SHOULDN'T be written in movement orders, this
should be a variable too: If the planet diameter is less than
10000 miles, the orbit velocity should be 4 - if more than 10000
miles, the orbit velocity should be 5.
Now, how close & how far away can a ship engage in FTL movement?
According to "Traveller", a starship should manoeuver out to about
100 diameters from any object more than 1 mile in diameter, or risk
misjump. So, for the average "garden" planet, a ship should be 450
MU from the planet to safely engage the jumpdrives.
The problem with this is Jim Webster's scenario on page 37 of More
Thrust, where the distance from orbit to safe jump distance is the
width of the game table. So in THAT scenario, the safe jump
distance is closer to 10 diameters, or 45 MU.
The problem with THAT is that the Tuffleyverse has pirate
organizations - BIG ones - like ORC & Actuarial Nightmare, who
would find it next to impossible to operate if they could only
strike at ships that close to planets with patrols nearby.
So here's a compromise...
Starships with CIVILIAN-built jumpdrives should manoeuver out to
100 diameters from any object more than 1 mile in diameter before
engaging jump. If jump is engaged at less than that distance - in
emergency or miscalculation - the jumpdrive suffers an IMMEDIATE
threshold check - add +1 to the die roll for every 10 diameters
short..
Starships with MILITARY jumpdrives should manoeuver out to 10
diameters - at less than that distance, threshold check - add +1 to
the die roll for every 1 diameter short.
(This should preserve Jim Webster's scenario while giving the
pirates their "hunting grounds".)
Now, what about the system's star? Is it bound by the same "100-
diameter" rule? In preparing for this post, I checked out websites
that let you build scale models of our solar system using
basketballs, peppercorns, pinheads, & marbles. I found that the
distance from our sun to the orbit of Pluto is about 4000 diameters
of the sun, which is about 40 AU. THAT means that by coincidence 1
AU - the distance from sun to Earth - is 100 solar diameters! THAT
must be where Marc Miller - who helped design "Traveller" - got the
idea for the "100-diameter" rule.
But rather than use the straight-forward "100-diameter" rule for
stars, I could just rule that the safe jump distance for stars is
the same as the inner limit of the star's "biozone" - that's close
enough.
(FYI, the inner limit biozone data, as well as the stellar gravity
well data in my July'05 posting, I got from an obscure sci-fi rpg
called "Web of Stars" from Web Games - I bought it FOR the star
system data)
TYPE SIZE JUMP LIMIT [in AU]
O Ia 9.0
O Ib 8.0
O V 7.5
B Ia 7.0
B Ib 6.5
B II 6.0
B III 5.5
B IV 5.0
B V 4.5
A Ia 4.0
A Ib 3.8
A II 3.4
A III 3.0
A IV 2.8
A V 2.5
F Ia 2.2
F Ib 2.0
F II 1.9
F III 1.8
F IV 1.7
F V 1.6
G Ia 1.6
G Ib 1.5
G II 1.0
G III 0.9
G IV 0.8
G V 0.6
G VI 0.5
K Ia 0.4
K Ib 0.4
K II 0.3
K III 0.3
K IV 0.2
K V 0.2
K VI 0.1
M Ia 0.1
M Ib 0.1
M II 0.1
M III 0.1
M V 0.04
M VI 0.03
Dwarfs 0.1
Superbrights +2.0
Pulsars 0.8
Neutron Stars 0.6
Protostars 0.04
I'm getting tired of typing, so I invite your questions & comments.
JBrewer@xxxxxxxxx "Always strive to be a good person. If you can't
do that, at least strive to be someone other than an asshole."
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