Astronauts

Their Dragon capsule - supplied and operated by the private SpaceX company - attached to the bow section of the orbiting lab 422km above China.

After a wait for leak, pressure and temperature checks, the pair disembarked to join the Russian and American crew already on the ISS.

Hurley and Behnken launched from Florida on Saturday.

Theirs is the first crew outing launched from American soil since the retirement of the US space agency (Nasa) shuttles nine years ago.

It will focus on long-term explorations and use of the Moon's surface, in partnership with the private sector.

Mr Trump also said the program would lay the foundation for an eventual mission to Mars, although he did not give a date for this.

Correspondents say any realistic effort will probably need Congress to agree to a big funding boost.

There is bipartisan support for further space exploration but parties disagree over the timeline and budget.

And if they had a medical issue or injury, home wouldn't be far away.

But for astronauts on future deep-space missions, like one to Mars, even a simple radio message might take up to 20 minutes to reach Earth. So how can they pack light and still bring all of the necessities, especially with an increased risk of injury during a six-month flight?

The answer could be what Dr. Julielynn Wong calls the "doctor's bag of the future": 3-D printing.