Re: Asteroids

>Ran a FT combat and decided to try having asteroids on the board. We
got
>into a discussio on how dense an asteroid field should be. I had 1
>asteroid about every 12", they thought there should be a lot more (ie.
>Empire Strikes Back scene with Mil. Falcon). How dense do other players
>on the list place them? Does anyone know about the real life asteroid
>belt: how close are the big asteroids to each other, how big, or small,
>would one have to be to be a hazard, etc.

Hollywood? SF? Dramatic Effect? It's a lot denser. And in NO way bears
any representation to reality (eg, Empire Strikes Back). It's purely for
visual effect.

Reality? Asteroids are really really reeeeaaally far apart from each
other.
If the asteroid field were anywhere NEAR as dense as what you see in
Hollywood,
you could actually SEE the thing as a ring in our solar system. Despite
the
low albedos (light reflectivity) of individual asteroids, combined
together
in such dense proportions would reflect plenty of light.

Want a fight in an Real Asteroid Field? Put one asteroid on the map.
Voila'!
You are in the asteroid field.	:-)  (Okay, okay, so it depends on what
scale
you're talking here; you might put in two)

How big/small are they to be a hazard? Okay, asteroid-education time. 
;-)
To be a hazard, it again depends on your scale, and depends on how fast
you're
travelling in RL. If fast enough, a basketball-sized asteroid could be a
real
bummer.  ;-)   How big? THere ain't too many 'big' asteroids out there.
There
are only 18 that measure 125 kilometers across or larger (the largest is
only
512 km; the second largest is a whopping 277 km, and they go down from
there).
Of those 18, only 4 are greater than 200 km. There are about 4000 or so
which
are 50 km across or larger. You could probably feasibly guess that there
are
4 or more times as many which are only a few kilometers across.

So, now, let's say we're talking 20,000 asteroids here (just a rough
number,
something to work with). That's really not very much in the grand scheme
of
things. You see, it's like this...

The 'width' of the asteroid belt is quite large. Asteroids tend to range
in
bands from ~1.8 AU to ~5.2 AU from the sun (side note: 1 AU
[Astronomical
Unit] is the distance from the sun to Earth; Mars is ~1.5 AU away from
the sun,
and Jupiter is ~5.2 AU away). There are gaps between the bands, called
Kirkwood
Gaps (I will leave it as an exercise for the student to explore the
Kirkwood
Gap phenomenon). Most asteroids are 'concentrated' in a band that ranges
from
2.2 to 3.2 AU That's an area 93 million miles across. And from
186,000,000 to
270,000,000 miles from the sun. This will yield an area of space that
covers
some 1.2 x 10**17 miles (that's 1.2 followed by 17 0's, btw  :).

To replicate, use this simple calculation:

    pi x (270,000,000**2 - 186,000,000**2)

  where 'pi' is ~3.14159

Now...toss 20,000 asteroids in an area measuring 1.2 x 10**17 miles. Oh,
hell,
toss 20,000,000 asteroids in it. You only get 1 asteroid every
6,000,000,000
miles! And now we're talking stuff that's measuring meters across. And
only
18 of them are larger than 125 km.

Okay, for the moment, go back to your map. Remove that one asteroid (or
both
if you put down two). Now you have a blank map with ships. Declare this
is
an asteroid field. You'll be just as right as not.

Now, mind you, I'm only talking 2 dimensions here. I haven't even
tackled
the Z-coordinate (okay, yeah, it won't be *real* far above/below the
plane
of the asteroid 'ring', but it'll be enough to really diffuse an already
tenuous 'field').

I hope this illustrates the point. WHich basically says: Hollywood is
full of
it.

Trivia note: some of you may have noticed that Jupiter is ~5.2 AU from
the sun,
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.

Thus endeth the lesson for today.  :-)

Mk
(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)
------------------------------------------------------------------------
-
   o/		      ..     .
  /@		       .  .	      If you insist on reaching for a
  <|\			  .  )	      star, be prepared to take a long,
   |		     /\ 	      hard fall.
   |		    //
   /		 o //*		      Indy - climber, astronomer,
adventurer
  /		<%- /|\ 	      supreme. Have rope, will travel.
 /		/\ / | \