Apollo 9.
Apollo 9 (March 3–13, 1969) was the third crewed mission in the United States Apollo program. Launched by a Saturn V rocket and flown in Low Earth Orbit, the mission flight-qualified the Lunar Module, showing that its crew could fly it independently, then rendezvous and dock, as would be required for Apollo 11, the first crewed lunar landing. Commander James McDivitt, Command Module Pilot David Scott, and Lunar Module Pilot Rusty Schweickart tested systems and procedures critical to landing on the Moon. A spacewalk tested the extravehicular life support backpack. McDivitt and Schweickart, entering the lunar module through the docking tunnel, became the first humans to pass between spacecraft without going outside them, two months after Soviet cosmonauts spacewalked to transfer between Soyuz 4 and Soyuz 5. Apollo 9, a complete success, was followed by Apollo 10, the dress rehearsal for Apollo 11.
