Walker served as a mission specialist during NASA’s SpaceX Crew-1 mission to the International Space Station in 2020, the first crewed operational Dragon spacecraft flight. She also was the first woman to fly aboard a Dragon spacecraft. Once aboard the orbiting laboratory, Walker joined the Expedition 64/65 crew and briefly commanded Expedition 65, logging 167 days in space before returning to Earth in May 2021. She spent 163 days in space during her first spaceflight in 2010 as a member of the space station’s Expedition 24/25 crew. She was the pilot of the Soyuz TMA-19, which became the first crew to dock with the station’s Rassvet module.