Fuel
From Tardis Wiki, the free Doctor Who reference
According to the Thirteenth Doctor, positrons produced by the Tsuranga's particle accelerator interacted with the fuel materials to produce heat, which produced thrust. (TV: The Tsuranga Conundrum)
The Rocket ZA685 operated on a chemical fuel, of which there was barely enough for a return journey from Earth to the Moon, however the Moon continued to have fuel storage into the 2080s. (TV: The Seeds of Death)
