Robert Louis Behnken is a NASA astronaut, engineer, and former Chief of the Astronaut Office. Behnken holds a Ph.D in mechanical engineering and the rank of colonel in the U.S. Air Force, where he served before joining NASA in 2000. He flew aboard Space Shuttle missions STS-123 and STS-130 as a mission specialist, accumulating over 708 hours in space, including 55 hours of spacewalk time. He is married to fellow astronaut K. Megan McArthur.
Following retirement of the Space Shuttle, Behnken was Chief of the Astronaut Office from 2012 to 2015. Assigned to the SpaceX Dragon Capsule in 2018 as part of NASA's Commercial Crew Program, Behnken launched aboard the spacecraft's first crewed mission with fellow astronaut Doug Hurley on May 30, 2020, and became one of the first two astronauts launching aboard a commercial orbital spacecraft in spaceflight history. The mission, Crew Dragon Demo-2, took Behnken and Hurley to the International Space Station, where they docked and stayed aboard for 62 days. Behnken completed four spacewalks with NASA Astronaut Christopher Cassidy.