To this and sibling posts: as far as I know no, the methane used for rocketry is extremely pure and doesn't have any scent, nor indeed does natural gas getting

To this and sibling posts: as far as I know no, the methane used for rocketry is extremely pure and doesn't have any scent, nor indeed does natural gas getting moved around or used industrially. It's expensive as an additive, but more importantly sulfur is bad news for a big range of applications, and when it comes to engines in general let alone rocket engines combusters/injectors etc are not sulfur loving. Sulfur is bad in vacuum chambers too for that matter, gets into the walls and then the chamber is contaminated forever. This isn't just a methane thing either, it's an issue with traditional fuels. The formulation for RP-1 has changed significantly over time in that respect for example, from the original 500ppm down to 30ppm now. And if it was cheap enough and still mattered one reason rocketry and aerospace companies might be interested in synfuels beyond the environmental aspect is being able to have zero sulfur at all from the get-go.