These propellants do not require an ignition system to start the engine, as the fuel and oxidizer react violently the moment they mix in the combustion chamber. This makes them highly reliable for maneuvering thrusters and in-space engine restarts where a spark failure would be catastrophic. The chemicals involved are typically highly toxic and corrosive, requiring specialized handling equipment.
The orbital maneuvering system uses a hypergolic mix, so we can pulse the thrusters without worrying about an igniter failing.
Because hypergolic fuels like hydrazine are extremely toxic, ground crews must wear full self-contained atmospheric protective suits when fueling the spacecraft.
Also heard as
- hypergols
Related terms
Chemical rocket
A propulsion system that generates thrust through the exothermic reaction of chemical propellants.
OMS
The Orbital Maneuvering System provides thrust for spacecraft orbital changes.
Hard start
A damaging overpressure event or explosion that occurs when a rocket engine ignites with excess propellant in the combustion chamber.