Behnken attended Pattonville High School in Maryland Heights, Missouri (in St. Louis County), and went on to earn Bachelor of Science degrees in mechanical engineering and physics from Washington University in St. Louis in 1992. He attended Caltech for graduate school, where he earned a Master of Science degree in Mechanical Engineering in 1993, and a doctoral degree in 1997.Outstanding Mechanical Engineering Senior, Washington University (1992)National Science Foundation Graduate Research Fellow (1993–1996)Air Force Research Laboratory Munitions Directorate, Eglin AFB, Company Grade Officer of the Year (1997)Air Force Achievement Medal (1997); Air Force Commendation Medal (1998, 2000)Distinguished graduate from the USAF Test Pilot School Program (1999)Recipient of the USAF Test Pilot School Colonel Ray Jones Award as the top Flight Test Engineer/Flight Test Navigator in class 98B.
Behnken's graduate thesis research was in the area of nonlinear control applied to stabilizing rotating stall and surge in axial-flow compressors. The research included nonlinear analysis, real-time software implementation development, and extensive hardware construction. During his first two years of graduate study, Behnken developed and implemented real-time control algorithms and hardware for flexible robotic manipulators.
Prior to entering graduate school, Behnken was an Air Force ROTC student at Washington University in St. Louis, and after graduate school was assigned to enter Air Force active duty at Eglin AFB, Florida. While at Eglin, he worked as a technical manager and developmental engineer for new munitions systems. Behnken was next assigned to attend the U.S. Air Force Test Pilot School Flight Test engineer's course at Edwards AFB, California. After graduating, he was assigned to the F-22 Combined Test Force (CTF) and remained at Edwards. While assigned to the F-22 program, Behnken was the lead flight test engineer for Raptor 4004 and a special projects test director. These responsibilities included flight test sortie planning, control room configuration development, and test conduct. Behnken also flew in both the F-15 and F-16 aircraft in support of the F-22 flight test program.
Behnken has over 780 flight hours in more than 25 different aircraft types.
Selected as an astronaut candidate by NASA in July 2000, Behnken reported for training in August 2000. Following the completion of 18 months of training and evaluation, he was assigned technical duties in the Astronaut Office Shuttle Operations Branch supporting launch and landing operations at Kennedy Space Center, Florida.
In September 2006, Behnken served as an aquanaut during the NEEMO 11 mission aboard the Aquarius underwater laboratory, living and working underwater for seven days.
Behnken was a crew member of the STS-123 mission that delivered the Japanese Experiment Module and the Special Purpose Dexterous Manipulator to the International Space Station in March 2008. Behnken took part in three spacewalks during the mission.
Behnken also flew as a Mission Specialist on STS-130, which launched at 04:14 EST (09:14 UTC) 8 February 2010. This mission delivered the Tranquility module and Cupola to the International Space Station. Behnken again took part in three spacewalks during this mission.
In July 2012, Behnken was named Chief of the Astronaut Office, succeeding Peggy Whitson. He held the job until July 2015, when he was succeeded by Chris Cassidy, after being selected as one of four astronauts training to fly spacecraft contracted under NASA's Commercial Crew Program.
Behnken is married to fellow astronaut K. Megan McArthur.