Monopropellantteja

Monopropellantteja are substances that can decompose exothermically to produce hot gas for propulsion. Unlike bipropellants, which require two separate components to react, monopropellants contain all the necessary elements within a single, stable molecule. This inherent simplicity simplifies rocket engine design and operation. The decomposition is typically initiated by a catalyst or heat.

The most common monopropellant used in rocketry is hydrazine (N2H4). Hydrazine can be decomposed over a catalyst, such as iridium or platinum supported on alumina, to produce nitrogen, hydrogen, and ammonia. This reaction generates a significant amount of heat and gas, providing thrust. Other monopropellants include hydrogen peroxide (H2O2), often used in a concentrated form, and nitromethane (CH3NO2).

Monopropellant systems are favored for their reliability and ease of use in applications where high performance is not the primary concern. They are commonly found in spacecraft attitude control thrusters, where precise, small impulses are needed to orient or adjust the spacecraft's position. Their simplicity also makes them suitable for smaller launch vehicles or as a backup propulsion system. However, monopropellants generally have a lower specific impulse (a measure of propellant efficiency) compared to bipropellants, meaning they are less efficient for high-thrust or long-duration missions. The handling of some monopropellants, like hydrazine, requires careful safety precautions due to their toxicity and reactivity.