CAPE CANAVERAL, AP – A SpaceX capsule carrying four astronauts has arrived safely at the International Space Station after a 21-hour flight from NASA’s Kennedy Space Center.

The one German and three US astronauts on board said it was an emotional moment when they first spotted the space station 30km away – “a pretty glorious sight”, according to Raja Chari, commander of the Dragon capsule.

“Floating in space and shining like a diamond,” said German astronaut Matthias Maurer.

“We’re all very thrilled, very excited.”

The Dragon’s entire flight was automated, with Chari and pilot Tom Marshburn monitoring the capsule systems, ready to take control if necessary.

At one point, they reported what looked like a “gnarled knob” or possibly a small mechanical nut floating past their camera’s field of view, but SpaceX Mission Control said it posed no concern.

Docking occurred 423km above the eastern Caribbean.

The station’s welcoming committee consisted of three astronauts instead of the originally planned seven, after SpaceX returned four of the ISS residents on Monday following several delays to the new arrivals’ launch.

While Chari, Marshburn, Maurer and NASA astronaut Kayla Barron were adapting to weightlessness – all but Marshburn are space rookies – the previous crew was adjusting to life back on earth.

“Gravity sucks, but getting used to it slowly,” Japanese astronaut Akihoki Hoshide tweeted.

The new crew will spend the next six months at the space station and, during that time, will host two groups of visiting tourists.

Russia will launch the first group in December and SpaceX the second in February.