How does propulsion work?
DS1 has two propulsion systems: The attitude control system and the solar electric propulsion (ion propulsion) system.
If DS1 ran out of hydrazine to use as fuel for the attitude control system, it could not correct its heading. If it got off course, it would never get back on. It would also not be able to point its camera (MICAS) at objects to take pictures.
The solar electric propulsion system pushes DS1 towards its destinations in space by ionizing xenon atoms electrically and then shooting them into space. The other "fuel" for the IPS (ion propulsion system) is the electricity generated by DS1's solar panels. That "fuel" will run out as the spacecraft gets farther from the Sun and the solar panels become unable to produce enough electricity. At that point, DS1 will be unable to increase its thrust and will float, pulled by the gravity of the Sun and pushed by its own inertia. It may run out of xenon atoms, but that is unlikely, because it has enough atoms on board to carry it past Mars, where the amount of sunlight is becomes too small to run the solar electric propulsion. Thus, solar energy limits the main drive more than amount of atoms.
Why does DS1 get off course?
What happens to a ship when it runs out of power?
Where does DS1 get its electricity?
What is attitude control?
What kind of fuel do DS1's attitude thrusters use, and how much of it do they use?
What is inertia?
What is thrust?
What role does the Sun play in space missions like DS1's?
What is MICAS?
How does DS1 do a course correction?
Why do solar panels become less useful the farther they get from the Sun?