RE: gravity and ftl [longish] (was severalm other things)

Something like this would be possible to track & chart on a
Starfire-type 
system map, but only the biggies - otherwise, you're talking about a lot
of 
fiddly bits in a strategic system.  I still like the 0.1g limit, with 
pretty much unlimited jumping outside of that.	In 1000km/15 min scale,
you 
can get that limit on the table with a Terra-class planet pretty easily,
if 
my math is right ;).  As i remember, BattleSpace (BattleTech space
system, 
one of the better things they did) had the main jump points way the heck

out of the plane of the ecliptic, to avoid collisions with all the crud
in 
the plane.  Jumping in-plane was considered risky, and usually a prelude
to 
an attack - less time-to-target than the weeks(!) from the zenith/nadir 
points.

Noah

-----Original Message-----
From:	tom.anderson@altavista.net [SMTP:tom.anderson@altavista.net]
Sent:	Saturday, July 11, 1998 12:47 PM
To:	FTGZG-L@bolton.ac.uk
Subject:	Re: gravity and ftl [longish] (was severalm other
things)

Andrew Martin, Alex Shvarts & Brian Martin (although i suspect Mr Martin

wrote it and shamelessly used other people's names :-) wrote:

> In several SF systems, the writers suggest that FTL drives only work
in
> near-flat space.

for instance, i think this is how it works in the battletch books

> If I recall correctly, these are also Lagrange points.

i don't think there's any 'also' about it - as far as i know that's the 
definition of a Lagrange point!

> Around our Earth and Moon, there are, if I recall correctly, six L 
points.

i can only think of five - one point between the two, one 'behind'
either 
body and two equidistant from them and in the plane of the orbit (the 
Trojan points). mind you, this probably just means i can't remember the 
sixth.

note that there is a set of L points for every pair of bodies, ie many, 
given that there is in the Sol system (maybe a poor example, too many 
objects) one star, two gas giants, four rocky planets, two ice subgiants

and pluto, along with thirty-odd (?) moo
ns, and einstein knows how many asteroids (not to mention the particles
in 
the rings of saturn and jupiter, comets, 'roids outside the belt and 
man-made entities), and that each body has one set of L points (5 or 6)
for 
each other body in the system (10 m
ajor bodies, so 90 sets, so 540 points just for starters).

the points formed by these major bodies would be easier to predict,
since 
their motion is well measured; the smaller bodies, such as asteroids,
not 
only have less-well-measured paths, but (see The Many-Body Problem,
Henri 
Poincare, nonlinear dynamics of t
he solar system, etc) their paths are actually chaotic (in the
mathematical 
sense) and hard to predict; thus, there will be masses of jump points 
swarming about a system without much predictability.

in Battletech, i seem to remember that these were known as 'pirate
points' 
- being used mainly by pirates and other units seeking secrecy and not 
averse to risks.

incidentally, if you have Java and decent computational power, try the 
gravity simulator applet at:

http://www.newscientist.com/student/newton/newton.htm

which i wrote. well, part of it - another guy did the user interface, i
did 
the physics (i just tried this and it didn't work - the bug must be in
the 
other guy's code, all my pointers are properly initialised :-).

hope this helps,
Tom

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