Re: [GZG] [FT] Scale in the Tuffleyverse

 > How far is a MU?

There's an interesting discussion on the Exodus Project web-site  
about using realistic engines in tactical space combat games. It's  
not for the math-phobic, but there's lots of stuff on how thrust,  
time and distance fit together. The author decided on a 15-minute  
turn-length (so that his FT and Dirtside timescales would match),  
resulting in an MU of about 81 kilometres.

For our Beltwar games, I adopted an MU about 83km so that 12mu =  
1000km. This distance scale means there's no need to put out model  
planets; just treat one edge of the table as the planetary atmosphere  
and rule that anyone who goes off in anything other than a re-entry  
vehicle burns up... You could mark a curved edge if you want to be  
picky, especially for a smaller body like a moon. Dwarf planets like  
Ceres, or large asteroids (Pallas, Vesta etc.) can be represented by  
papier-mâché "scale" models.

Best regards, Robert Bryett
rbryett@gmail.com

On 21/01/2007, at 01:02 , John Brewer wrote:

> 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@lists.csua.berkeley.edu
> 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@webtv.net "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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