[GZG] [FT] Scale in the Tuffleyverse

["John Brewer" <jbrewer@xxxxxxxxx>]

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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