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.
Mark T. Vande Hei Mark Thomas Vande Hei (born November 10, 1966) is a current NASA astronaut selected in 2009, who launched to the International Space Station on September 12, 2017 for his first spaceflight.