The 'Rocket' is a vehicle or projectile that moves by expelling gases to the rear. It produces a recoil similar to the recoil of the gun being fired. The recoil (thrust) lasts as long as the rocket has the fuel to burn. A rocket consists mainly of two parts; the container of the fuel and the exhaust nozzle for burnt gases. The fuel container's shape, design and construction depends to a large extent on the type of fuel used (solid or liquid). Fuels could also be used in gaseous form, but the heavy pressure containers required make them impracticable for most purposes. 