                              Concept : Altitude

 Yes, Virginia, there is an atmosphere.  And, as in the  real  world,  if  you
loft things up into it, and if you put them high enough, they will stay there.

Through some strange, unknown physical  anomaly,  the  toroidal  form  of  the
empire world has long been known to have gravitational characteristics similar
to a sphere.  While many a student has scratched his head trying to comprehend
the  wierd  physical  nature of the planet, early astronomers and aeronautical
engineers were quick to realize that space flight would be a snap, and learned
to exploit its simple (mostly integer) laws.

Altitude in Empire is represented by integer values ranging  from  0  to  127,
where each step represents roughly 10000 feet, 2 miles, or 3 km -- however you
prefer to think of it.  The atmosphere (in which falling things  have  a  ten-
dency  to  burn  up)  extends  up to altitude 32; useful gravitational effects
extend up to altitude 127.  Beyond 127 lies the great, black,  endless,  scary
void called "space".

Normal Empire aircraft are generally restricted to flight at altitudes up to 5
or so; by including "^" values in flight paths, you can cause planes to change

                              Concept : Altitude

altitude (see `info flightpath').

Higher altitudes are the realm of space vehicles -- satellites  and  shuttles.
With sufficient angular velocity (speed), and neglecting atmospheric friction,
any vehicle placed at a specific given high altitude will tend  to  remain  at
that  altitude for a very long period of time.  These velocity/altitude combi-
nations are called `orbits'.

By strange coincidence, at the maximum altitude of 127, the velocity necessary
to  remain  in  orbit  exactly  matches the rotational surface velocity of the
planet itself.  Thus, any vehicle placed at altitude 127 will  forever  remain
in  a  fixed  position  over  a specific spot on the planet.  Also, by another
strange coincidence, atmospheric friction forces  become  negligable  at  this
point,  and  the  orbit will never decay.  In other words, a vehicle placed at
altitude 127 will stay over the same sector forever.

At lower altitudes, in order to maintain position, angular  velocity  must  be
increased.   After a lifetime spent throwing things from very high places, the
famous physicist "Sid" Euphemism derived his First Law of Things That Go  Fast
and Do Not Fall:

                              Concept : Altitude

       "Any object will stay aloft of its own accord if: At the edge
       of Scary Space (127), it has a velocity is 0 sector per update;
       At the edge of Our Atmosphere (32), it has a velocity of ETU
       sectors per update.  All points betwixt and between are linear."

Many years passed, and people turned their attention away from  physical  laws
and  toward  strange  works of music, fancy architecture, ornate clothing, and
writing bedtime stories.  Sid's Law remained undisputed,  but  also  untested,
until  the  early  17th century, when at the age of 4, the child genius Little
"Al" Kielbasa postulated the existance of atmospheric friction and its  effect
on objects moving in accordance with Sid's Law:

                              Concept : Altitude

       "The air and other stuff way up high, where Sid said stuff would
       fly forever, it hits the flying stuff like wind and makes it slow
       down kinda fast."

A few years later, after learning how to count, Al refined his postulate  into
his now-famous Law of Degrading Orbits:

       "At the edge of the atmosphere (32), an orbiting body will fall
       ETU/2 altitude levels per update.  Near the edge of space (126),
       an orbiting body will fall 1 altitude level per update.  The
       distance fallen at altitude levels in between varies linearly
       between 1 and ETU/2.  A body in the geosynchronous orbit at the
       edge of space (127), will lose no altitude forever.  Of course,
       really light things may be exceptions to this rule."

                              Concept : Altitude

Orbits in Empire are  expressed  as  "<velocity><direction>/<altitude>".   The
<velocity> and <direction> indicate the ground distance and direction that the
vehicle will move at the next update. The <altitude> indicates, obviously, the
altitude.

See also : build, planes, satellite, nuke-types,

