Has Piers Sellers or Hans Schlegel been on more Space Shuttle Missions?
Hans Schlegel Hans Wilhelm Schlegel (Überlingen, 3 August 1951) is a German physicist, an ESA astronaut, and a veteran of two NASA Space Shuttle missions.
Wubbo Ockels Wubbo Johannes Ockels (28 March 1946 – 18 May 2014) was a Dutch physicist and an astronaut of the European Space Agency (ESA). In 1985 he participated in a flight on the space shuttle Challenger, STS-61-A, making him the first Dutch citizen in space. After his astronaut career, Ockels was professor of "Aerospace for Sustainable Engineering and Technology" at the Delft University of Technology.