section_path: Principles
section_name: Principles
paragraph_text: Principles
  
  There are a few common ways of understanding orbits:
  
  The velocity relationship of two moving objects with mass can thus be considered in four practical classes, with subtypes:
  
  It is worth noting that orbital rockets are launched vertically at first to lift the rocket above the atmosphere (which causes frictional drag), and then slowly pitch over and finish firing the rocket engine parallel to the atmosphere to achieve orbit speed.
  
  Once in orbit, their speed keeps them in orbit above the atmosphere. If e.g., an elliptical orbit dips into dense air, the object will lose speed and re-enter (i.e. fall). Occasionally a space craft will intentionally intercept the atmosphere, in an act commonly referred to as an aerobraking maneuver.