Not to be ageist but is this not a slight risk from using astronauts who are older in age due to their important experience. It does feel as if we need to find a route to fast track at least some of the crew if we are to expand a program to far more expeditions.
They called mine a "mini-stroke". The symptoms were in my vision. After a few minutes the symptoms went away, and did not return. The docs scanned mah haid and put me on perma-meds for stroke patients. YMMV.
Van Allen belt (consisting of very high energy particles) extends somewhere from 400 to 600km above earth's surface so it's not that far from the space station
Just wanted to clarify: Here "space" means merely 300km above earth's surface and not thousands or millions.
Even 300km is very difficult to survive (space station's zero gravity, etc.)