In the aerospace context, hydrogen is a chemical element that is used as a fuel, coolant, or propellant in various aerospace systems and vehicles. Hydrogen is an attractive fuel source for aerospace applications because it is light, highly reactive, and can be converted into electricity to power an electric propulsion system.
Examples of hydrogen usage in aerospace include:
- Fuel cells: Hydrogen can be used to power fuel cells, which generate electricity through a chemical reaction between hydrogen and oxygen. These fuel cells can be used to power electric propulsion systems on aircraft and spacecraft.
- Cryogenic propellant: Liquid hydrogen and liquid oxygen are used as rocket propellant, this combination is known as cryogenic propellant. These cryogenic liquids are stored in the rocket at very low temperatures and require specialized insulation and handling equipment.
- Coolant: Liquid hydrogen is used as a coolant in the cryogenic fuel tanks of the Space Shuttle and the International Space Station.
- Ballast: hydrogen gas is sometimes used as a ballast in high altitude balloons, to control the buoyancy of the balloon.
Hydrogen is considered as a clean energy source as it produces only water vapor when it is used in a fuel cell. The use of hydrogen as a fuel for aerospace application is still in the early stages of development, but it has the potential to reduce dependence on fossil fuels, and to lower emissions and environmental impacts.