section_path: Uses
section_name: Uses
paragraph_text: Uses
  
  Rockets or other similar reaction devices carrying their own propellant must be used when there is no other substance (land, water, or air) or force (gravity, magnetism, light) that a vehicle may usefully employ for propulsion, such as in space. In these circumstances, it is necessary to carry all the propellant to be used.
  
  However, they are also useful in other situations: