You might have thought from watching videos of
astronauts aboard the International Space Station
(ISS) that spaceships were pretty benign
environments. Floating around in microgravity looks
like a lot of fun. As you are isolated from the rest of
the human population, you are effectively
quarantined against catching flu or any other
transmissible disease. But in fact, space is pretty
harmful to the human body. ---- Therefore, travelling
beyond the planet has a number of negative effects
on the body and mind which need to be overcome
for long-duration missions in the future.