Definition
The specialized chemical propellants used in spacecraft engines (like Draco Thrusters) that are chosen for storability and reliability rather than pure thrust performance.
Why It Matters
Choosing the right propellant is the ‘life-or-death’ trade-off of mission design; understanding hypergols is critical for ensuring that thrusters can fire spontaneously and reliably after years in the vacuum of space, even at the cost of extreme toxicity.
Core Concepts
- Hypergols: Propellants that spontaneously ignite upon contact (e.g., MMH and NTO). This removes the need for complex ignition systems.
- MMH (Monomethylhydrazine): The fuel component; highly toxic and storable at room temperature.
- NTO (Nitrogen Tetroxide): The oxidizer component; a powerful oxidizer that is similarly storable.
- Toxicity: Hypergols are extremely hazardous to humans; contact can be fatal (e.g., the 1960 Nedelin Catastrophe).
- Storable Logic: Unlike cryogenic fuels (LOX/LH2) that boil off, hypergols can remain in tanks for years, making them ideal for long-duration space missions.