He flew on the Endeavour space shuttle mission in April 2001 that delivered the Canadarm 2 to the International Space Station (ISS). Following the Columbia space shuttle disaster in 2003, Phillips flew once again into space in 2005 aboard a Soyuz spacecraft to the ISS, where he served as flight engineer. He returned to space in 2009 aboard the space shuttle Discovery, where he operated the Canadarm-2 robotic arm to unberth and install the S6 truss to the ISS. In 1989, Phillips became the principal investigator for the Solar Wind Plasma Experiment aboard the Ulysses space probe, based at the Los Alamos National Laboratory. He was selected as an astronaut in 1996 and retired from NASA in 2011. During his career, Phillips logged more than 203 days in space.