Which oxidizer is most commonly used in commercial hybrid rocket motors?

The correct answer is nitrous oxide (N2O) because it is the most widely used oxidizer in commercial hybrid rocket motors. Nitrous oxide is advantageous for hybrid engines due to its physical properties, such as being a gas at room temperature, which allows for easier handling and storage compared to liquid oxidizers. It also has a high energy content and provides a very stable reaction when mixed with a solid fuel like rubber or wax.

This oxidizer operates at a relatively low pressure when stored in a liquid state, making it safer for commercial applications. Additionally, nitrous oxide is not only used as an oxidizer but can also be employed in some applications to increase performance without the stability concerns that come with more reactive chemicals.

In contrast, the other listed oxidizers, such as nitrogen tetroxide (N2O4), nitrogen dioxide (NO2), and molecular oxygen (O2), have specific applications primarily in liquid engines. They may be more commonly found in bipropellant systems but do not match the popularity and practicality of nitrous oxide in hybrid systems where ease of use and safety are prioritized.