Safety and Reliability
Basic by Design
A hybrid motor is intrinsically safe compared to different rocket propulsion types mostly due to the composition of its fuel types. There are two fuel types found in rocket engines: a fuel and an oxidizer. Conventional hybrid motors have very simple compounds for these fuel types. The fuel is typical an inert compounds like rubber or plastic. Richard Branson's 'RocketMotorTwo' hybrid engine utilizes Nylon plastic as its fuel source, which is a commonly source-able material used in the automotive industry. The oxidizer type commonly used is liquid Nitrous-oxide. While this can be a dangerous compound when used in the incorrect manner, though it is much safer than all oxidizer alternatives found in industry. Nitrous-oxide is most famous for its use in the automotive industry, providing an aftermarket solution to get maximum engine performance out of the engine. The only opportunity for combustion to take place is when the fuel and oxidizer mix while in contact with a heat source, and since hybrids don't combine the fuel and oxidizer until the moment of launch, hybrids have a very high caliber of safety.
Hybrids and Human Spaceflight
Human spaceflight is the apex branch of the engineering field. NASA has the esteemed reputation it does in the world because of their ability to solve human spaceflight challenges. NASA and other governing agencies has extremely high standards for safety and reliability relating to human spaceflight applications. If a human is going aboard a spacecraft, all systems need to have the utmost safety reputation while being reliable and reputable compared to competitors. With hybrid's having the highest safety reputation for an engine class so early in its development, hybrid engine's are becoming a common choice for space tourism vehicles.
