From Rise: The Vieneo Province - The Space Simulator MMO from Unistellar Industries, LLC

A space ship in a perfect orbit still is falling with the 1G force it is just moving along the ground so fast that in 1 second yes it fell 9.8 meter but the curve of the planet surface cause the ship to seem like it stayed at the same elevation. Since the ship and everything in the ship are always falling every thing in the ship is weightless

To completely describe an orbit mathematically, six quantities must be calculated. These quantities are called orbital elements, or Keplerian elements. They are:

  1. Semi-major axis length apopsis to center of the ellipse.
  2. Eccentricity, a measurement of the orbit’s ellipse (an eccentricity of zero indicates a circular orbit. Written as E
    1. Eccentricity = ((Major axis2)-(Minor axis2)/Major axis).
  3. Inclination, the angular distance of the orbital plane from the plane of the planet’s equator: Written as I
  4. Periapsis is the elevation closest to the planet: Written as AP
  5. Apopsis is the elevation furthest from the planet surface: Written as AA

As a pilot you will be most concerned with the E and AP.
If you have a high E you are either risking flying of in to space or crashing in to the planet.
Obviously if you have a High E and AP is counting down to 0 you really need to start thinking about how not to crash in to the planet.
rana 15:16, 14 March 2007 (HKT)

Useful things pilots want to know

TVM Get to Target in the shortest route.
DOR Get in a prefect circular orbit using least fuel.