Bruce McCandless II(1937-2017)

McCandless is famous and celebrated for having been the first astronaut to make untethered, free flights in outer space - twice. The mission was on the STS-41B Challenger, launched on February 3, 1984; and it marked the first checkout of the Manned Maneuvering Unit and the Manipulator Foot Restraint, two new designed gear for astronauts.

[About making the first untethered space flight and referring to the famous line by Neil Armstrong, "That's one small step for man..."] It may have been one small step for Neil, but it's a heck of a leap for me.