> Note that in The Expanse universe, water isn't usually used as propellant, but simply as reaction mass. All we know about the actual propellant is that it's u

> Note that in The Expanse universe, water isn't usually used as propellant, but simply as reaction mass. All we know about the actual propellant is that it's used in fusion reactors and is surprisingly efficient. It's actually ambiguous if Ceres was spun up before the Epstein drive was invented or not. If the H2O was consumed in an Epstein drive (fueled by D-He3 fusion) then only Hydrogen was consumed to produce thrust. What's not ambiguous is that the H2O on Ceres was consumed We know that mars was colonized 200 years before the Epstein drive was invented. We know that the OPA was founded about 100 years after the Epstein drive was invented, and that 130 years after the Epstein drive is when the main story starts. We know Earth was the first owner of Ceres. We don't know how old Tycho is, other than Fred Johnson was not the first leader of Tycho. It's an open question on to what extend the belt had humans in it during the 200 years humans were on Mars before the invention of the Epstein drive. It's safe to say that answer is somewhere between more than none, and less than what is shown during the opening of the series. It's highly plausible Ceres was spun up during that time.