Article answer to your headline question: "It's around 20 years of propellant, roughly speaking,” though he added that it’s a preliminary estimate. There ar

Article answer to your headline question: "It's around 20 years of propellant, roughly speaking,” though he added that it’s a preliminary estimate. There are likely many factors that influence propellant usage which are unknowable - for example, photon pressure from the sun, which can vary over time in an unpredictable way.