Hypergolic propellant is a type of rocket fuel that ignites spontaneously upon contact with an oxidizer. This means that there is no need for an external ignition source, making it highly reliable for space missions. Common examples of hypergolic propellants include hydrazine as the fuel and nitrogen tetroxide as the oxidizer. These propellants are often used in spacecraft for maneuvering and orbital adjustments. One of the main advantages of hypergolic propellants is their simplicity and ease of handling. They can be stored for long periods without significant degradation, which is crucial for missions like those involving the Apollo Lunar Module or the Space Shuttle. However, they are toxic and require careful management during fueling and operation.