Neutronium as a Fuel
All starships use neutronium for fuel. Neutronium is a superdense material found at the core of many planets. It is also known as "neutronic" fuel. Fuel is millions of times denser than common elements such as lead or gold. The fuel must be stored in a very powerful inertial damping field to prevent damage to the starship's superstructure. The amount of fuel that a starship can carry is limited by the strength of the inertial damping field only and not the cargo room available on the ship.
Fuel is expended whenever a ship is given an order to move, is cloaked, or other similar circumstance.
Starships without fuel cannot attack enemy ships. Enemy ships are not allowed to attack ships that are out of fuel, due to the treaty of Nimbus 7. The treaty states "No ship may attack or destroy a ship that is out of fuel. Such ships are helpless and unable to protect themselves. Destroying helpless ships would be a tragic and senseless loss of life."