NASA Astronauts are among the most highly trained and physically fit normal humans in the Marvel Universe. They include men and women who have since obtained super powers as well as many real life heroes whose powers are much more mundane and therefore more extraordinary.
There have been many martyrs to the cause of expanding the frontier of human knowledge and the Marvel Book of the Dead numbers several NASA Astronauts among its ranks.
Astronaut characters in DC comics are less common portrayed. Diana Prince was depicted as an astronaut for a short time in the 1970s.