Astronaut reports hearing mysterious 'knocking' on his ship while in space

While many space junkies dream of being shot up into orbit, that's unfortunately not possible for a lot of us.

So, the next best option is to read interviews with those who have been lucky enough to go into space at some point in their lifetime.

Of course, a fair few people have explored outer space now, with many of them having varying experiences.

Yang Liwei is one of the lucky ones to have explored space, in fact, he made a bit of history in 2003 by becoming China's first astronaut.

He flew to space on board the Shenzhou 5 spacecraft, and made China the third country to independently send an astronaut to space.

Yang Liwei pictured in 2003. (Robert Ng/South China Morning Post via Getty Images)

Only the US and Russia had sent astronauts independently prior, so China certainly made a bit of history.

While Liwei made history just getting to space, what he reported from the time he was up there is just as compelling.

Yang was sent to space in 2003 on a 21-hour mission, but in an interview he revealed how nervous he was after hearing 'knocking' on board the Shenzhen 5 spaceship.

"A non-causal situation I have met in space is a knock that appeared from time to time," he told Xinhua.

"It neither came from outside nor inside the spaceship, but sounded like someone is knocking the body of the spaceship just as knocking an iron bucket with a wooden hammer."

The former astronaut went on to say he was nervous when he heard the sound, and looked out the porthole to try and see the cause.

The astronaut was left bemused by the noises. (STR/AFP via Getty Images)

However, Liwei saw nothing of note - which only added to suspicions.

Liwei certainly wasn't hearing things either, as the same sound was heard by other Chinese astronauts on the Shenzhou 6 in 2005 and 7 spacecraft in 2008.

So, now we've discovered China's first astronaut to go to space isn't crazy, what are the possibilities for the cause of the noise?

The first possibility is space debris could have struck the spacecraft, though this seems unlikely.

A more likely option is the noise may have been because of the spacecraft expanding and contracting in the low-temperature environment of space.

Upon Liwei's return into earth's atmosphere, he could no longer hear the noise on the shuttle. However, he tried his best to recreate it to see if technicians would recognize it.