A Firework Rocket is an item that was first seen in Snapshot 12w49a, and was added in the Christmas update (1.4.6.). Rockets are able to fade, shade, and have special effects. These can all be determined by the materials used in crafting the rocket. Fireworks can be customized into many different colors, sizes and heights. Fireworks must be placed on a solid block from hand in order to launch them from hand; this will cause them to go straight up, making a whistling sound and eventually a pop indicating the explosion. Fireworks can be shot from dispensers, but will head straight up upon being released from the dispenser.
Adding a Firework Star to the recipe will enable the rocket to have an explosion. Firework Stars of different colors, shapes and effects, can be combined when crafting a Firework Rocket to make a rocket with every aspect of the stars, without blending colors together. Adding more gunpowder to the recipe (1-3 gunpowder is all that can be used) will increase the height of the flight before the explosion. But it is currently not available in minecraft 1.8.3