These included suggesting the use of a modular spacecraft to reach the Moon, leaving the propulsion section of the vehicle on orbit while a smaller lander journeyed to the surface and back (the strategy eventually adopted by the engineers of the Apollo program).[7] He included detailed calculations of the trajectory to take a spacecraft from Earth orbit to lunar orbit and back to Earth orbit, a trajectory now known as "Kondratyuk's route" or "Kondratyuk's loop".