Buzz Aldrin propellants, with an expected five and a half month journey from the Earth to Mars, and a return trip to Earth of about the same duration on a twin-cycler. Aldrin continues to research this concept with engineers from Purdue University. In December 2003, Aldrin published an opinion piece in "The New York Times" criticizing NASA's objectives. In it, he voiced concern about NASA's development of a spacecraft "limited to transporting four astronauts at a time with little or no cargo carrying capability" and declared the goal of sending astronauts back to the Moon was "more like reaching for past glory
Space rendezvous maneuvering thrusters to adjust its orbit to match that of its twin. The initial separation distances were in the range of , and slowly diverged to thousands of kilometers (over a thousand miles) over the course of the missions. In 1963 Buzz Aldrin submitted his doctoral thesis titled, " Line-Of-Sight Guidance Techniques For Manned Orbital Rendezvous." As a NASA astronaut, Aldrin worked to "translate complex orbital mechanics into relatively simple flight plans for my colleagues." The first attempt at rendezvous was made on June 3, 1965, when US astronaut Jim McDivitt tried to maneuver his Gemini 4 craft to meet