We just learned about the Solid Rocket Propellants.
Another type of propellant is Liquid Rocket Propellants.
These can be made up of liquids like gasoline, kerosene or alcohol that are liquids at regular temperatures.
They can also be things that are liquids at really cold temperatures like liquid oxygen, or liquid hydrogen.
The good thing about liquid propellants is that they are lighter than solid ones, so a rocket doesn't have to try as hard to push itself along.
The bad thing is that sometimes they have to be stored very cold in a very high pressure container, and sometimes the liquids can cause problems and eat away at the metals and rubbers that they are stored in.
The first person to make a liquid fueled rocket was Robert H. Goddard, who used gasoline and liquid oxygen to launch a rocket in 1926 in Massachusetts.
(from: wikipedia - robert h. goddard)
Kid Facts - Blast from the past: Threading
