This reduces the amount of energy required to push the rocket through the atmosphere into space. The nose cone protects the payload against aerodynamic wind blast which is very prevalent when a vehicle speeds through the Earth's atmosphere. As previously stated, rocket fuel is also called propellant. Propellant includes not only a fuel which is actually burned, but also an oxidizer which supplies oxygen for the combustion process. Propellant efficiencies are measured by a term called specific impulse, Isp.
Liquid propellants develop the most efficient thrusts for rocket power.
This propellant has an Isp of 254 seconds at sea level and a 302 second rating in a vacuum. These highly efficient fuels and oxidizers still need an ignition spark to start the combustion process. A special liquid propellant which does not need ignition to start combustion is a fuel which ignites spontaneously when it comes into contact with its oxidizer. This type of fuel is called hypergolic. There are two important advantages of using a liquid fuel.