To stay in the proper orbit, many satellites have thrusters – small rocket engines – that fire to change altitude or orientation in space. On Earth, where gravity dominates, five pounds of thrust, equivalent to 22 Newtons of force, may seem small, but in space, it doesn’t take much thrust to move a large spacecraft.
Currently, most satellite thrusters are powered by hydrazine, a toxic and corrosive fuel that is dangerous to handle and store. In a quest to replace hydrazine with a more environmentally friendly fuel, NASA is testing thrusters propelled by green propellants that can provide better performance than hydrazine without the toxicity.
NASA recently completed hot-fire tests with thrusters powered by two different green propellants – AF-M315E and LMP-103S. Both are ionic liquid-based blends that are less toxic and less flammable than hydrazine, which makes them easier and less costly to store, handle, and fuel up spacecraft before launch. Additionally, the new propellants offer higher performance, delivering more thrust for a given quantity of propellant than hydrazine.