Re: Asteroids - Reply

Our own "Indy" (Going into the ocean at 600 mph? B-o) wrote:

>> ...and I indicated some asteroids range out as far as 5.2 AU from the
sun;
these asteroids are part of the Kirkwood Gap phenomenon, and are called
Trojan Asteroids, something some of you may have heard of before, in
some
dim faint distant memory from a basic astronomy class. <<

To which Sturart replied:

> I think there are Trojan point asteroids described in the
Niven/Pournelle
"Mote" series.	So for us non-physics guys, what does this really mean?
<

I'm no physics expert, but my understanding of the Trojan point concept
is that
it's a quirk of gravitation. If you have two large masses (does one have
to be
much bigger than the other?) orbiting each other -- or, for simplicity,
let's
consider one of them orbiting the other -- then points in the orbit 60
degrees
ahead and behind the mass are gravitationally stable, i.e., another mass
(and
this time I think it has to be much smaller than either of the first
two) located at
one of those points will stay there and won't be pulled out of position
by gravity
(of course, you do have to deal with gravitational effects from any
other bodies in
the system, but they will hopefully be small).

Which makes the Trojan points a really good place to put a space station
or an
O'Neill colony. It also means that, given enough time, asteroids that
drift through
these points may collect there -- which can mean that there's a ready
supply of
raw material to make that O'Neill colony! Also that you need a good
asteroid
defence for when the next Trojan-wannabe drifts through...

>> (ps: knowing the above, I did run a PBeM FT game last year that took
place
in a hellaciously dense asteroid field -- 30 or so asteroids in a 4900
square unit
area. The purpose was mainly for terrain to force the players to
maneuver about
the place, rather than fight in open space, but in reality this field
would not exist,
unless it was from something recently broken up. I will likely create
fields just
as dense in the future for gaming purposes, but not to reflect reality
any --
unless you want to call it an asteroid 'clump', which might really occur
in very
localized areas, but again, 30 was a heck of a dense field) <<

So you were fighting in and around a Trojan point! They're prime
locations for
battles, because they're where raw material collects.

I hope no-one is going to tear my "explanation" apart, but whether they
do or
not, could some of the _real_ astrophysics buffs answer these:

-- Are the Trojans the same as the L-4 and L-5 Lagrange points?
-- Are points 120 degrees ahead and behind the orbiting mass stable? (I
know
180 is!)

I should know this stuff! I did once, but, like Rabbit, I've forgotten.
<g>

Forgetful Phil
-------------------------------------------------------------
 Gravity is a Downer... So let's go flying!
   -- so sayeth Phil Atcliffe (p-atclif@uwe.ac.uk)