SpaceX is set to launch its third crew to the International Space Station an hour before sunrise Friday, recycling a rocket and spacecraft for the first time.

The Crew-2 mission blasts off from pad 39A at the Kennedy Space Center in Florida at 5:49 am Eastern Time (0949 GMT), after being delayed a day by adverse weather along the flight path.

Around 2:30 am (0630 GMT), Thomas Pesquet of France—the first European on a SpaceX mission—along with Americans Shane Kimbrough and Megan McArthur and Japan's Akihiko Hoshide strode out in their suits to say goodbye to their families.

NASA successfully carried out a second flight on Mars on Thursday of its mini helicopter Ingenuity, a 52-second sortie that saw it climb to a height of 16 feet (five meters).

"So far, the engineering telemetry we have received and analyzed tell us that the flight met expectations," said Bob Balaram, Ingenuity's chief engineer at NASA's Jet Propulsion Laboratory in southern California.

From muscle loss to radiation exposure and the psychological effects of confinement, spaceflight takes a toll on those lucky enough to experience it.

European Space Agency flight surgeon Adrianos Golemis, who is responsible for the health of astronaut Thomas Pesquet during the SpaceX Crew-2 mission, shared some insights on the field of space medicine.

Q: What are the major health challenges of space?

A: If we talk about low Earth orbit where the ISS lies, you have almost zero gravity so that takes its toll on your bones and your muscles.

Radiation is a major issue, because here on the ground we are protected by the magnetosphere (magnetic field) and by the atmosphere, but if we go beyond, this protection goes away.

And of course we should not forget we have things that we are just beginning to understand: for example eye pathology (disease), or venous thrombosis (blood clots) that some healthy astronauts develop.