Approaching the Unknown (2016) on Netflix

Plot summary

The whole world is watching William Stanaforth, but no one is on the spacecraft with him. He is the first person sent on a lone mission to Mars, a one-way trip meant to begin the human settlement of the planet. After liftoff and the rocket separations, he takes off his suit to relax, and the team on the ground sets him on course for 270 days. Flashbacks show him working out the idea before the mission: he makes water by supercompressing sand and dirt and recombining the hydrogen and oxygen they give off, and that synthesis is what makes the journey possible.